Heat powered turbine operated with thermal cyclic working gas

Abstract

A closed-cycle axial flow gas turbine arrangement (7) comprising a gas turbine housing (13), a rotor (14) carrying turbine blades (21) and being operably connected to a rotor output shaft (15), an axial compressor (1) comprising compressor blades (22) located on the rotor (14), a working gas heating arrangement (27), and a working gas cooling arrangement (28). The gas turbine arrangement (7) is configured for converting thermal energy to kinetic energy by a thermal cyclic working gas operation involving: heating the working gas in the working gas heating arrangement (27), guiding the heated working gas in a first mainly axial direction to the turbine blades (21) for rotating the rotor (14), cooling the working gas the in working gas cooling arrangement (28) and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades (22) for compressing the working gas, and guiding the compressed working gas back to the working gas heating arrangement (27).

Description

[0001] Heat powered turbine operated with thermal cyclic working gas

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a heat-engine for converting heat to kinetic energy. Such heat-engine can be used for driving any machinery that can produce work or energy in another form. Common use is to drive electric generator to produce electricity, and other options could be but not limited to hydraulic pumps, fans or heat pumps.

[0004] BACKGROUND

[0005] Various types of heat-engines for converting heat to kinetic energy are known. Stirling engines are typically associated with different types of piston engines, either as a free piston concept or connected mechanical piston engines. The sizes are typically from 1 kW to 30 kW and limited in engine speed from 1000 rpm to 3000 rpm. The existing Stirling engine concepts are designed from one-cylinder units to four cylinders. Stirling engines can be used for energy or heat recovery, or as direct drive engines fuelled by any heat source to create for example electricity.

[0006] Competitive technologies exist in terms of steam engines, such as Organic Rankine Cycles (ORC), or regular steam machinery as Rankine Cycles (RC). Typically, ORC units can operate on a lower temperature level compared with a regular steam engines for producing electricity for an energy recovery application, but the overall efficiency of ORC engines is generally around 15% or less, thus significantly lower than conventional Stirling technology.

[0007] Regular Rankine Cycle concepts typically demand a much bigger size for installation, such as 10 to 20 MW size plants to be financially viable. The level of investment will thus follow the size of installed power and can be seen as an disadvantage. But Rankine Cycle are a well-known and established technology.

[0008] Stirling technology can play a role in between ORC and RC applications thanks to a better efficiency and a better size matching versus installed cost. However, traditional Stirling engines have disadvantages with mechanical piston concepts both from temperature profiles and to get a proper sealing for the working gas as well as producing higher power. The working gas creates the work that is done in the engine thanks to cyclic cooling and heating of the gas. The power output is limited to and determined by the parameters of working gas pressure, engine speed, available heat and available cooling.

[0009] Closed-cycle gas turbines for converting heat from an external heat source to electrical power are known but existing designs generally fail to provide high operating efficiency, operating reliability, cost-efficiency and / or a compact layout.

[0010] SUMMARY

[0011] An object of the present disclosure is to provide a closed-cycle gas turbine driven by heat from an external heat source where the previously mentioned problems are avoided. This object is at least partly achieved by the features of the independent claims. The dependent claims contain further developments of the gas-turbine and associated method.

[0012] According to a first aspect of the present disclosure, there is provided a closed-cycle axial flow gas turbine arrangement comprising: a gas turbine housing; a rotor carrying turbine blades and being operably connected to a rotor output shaft; an axial compressor comprising compressor blades located on the rotor; a working gas heating arrangement; and a working gas cooling arrangement. The gas turbine arrangement is configured for converting thermal energy to kinetic energy by a thermal cyclic working gas operation involving: heating the working gas in the working gas heating arrangement; guiding the heated working gas in a first mainly axial direction to the turbine blades for rotating the rotor; cooling the working gas the in working gas cooling arrangement and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades for compressing the working gas; and guiding the compressed working gas back to the working gas heating arrangement.

[0013] According to a second aspect of the present disclosure, there is provided method for operating a closed-cycle axial flow gas turbine arrangement with working gas for converting thermal energy to kinetic energy. The closed-cycle gas turbine arrangement comprises: a gas turbine housing; a rotor carrying turbine blades and being operably connected to a rotor output shaft; an axial compressor comprising compressor blades located on the rotor; a working gas heating arrangement; and a working gas cooling arrangement. The method comprises: heating the working gas in the working gas heating arrangement; guiding the heated working gas in a first mainly axial direction to the turbine blades for rotating the rotor; cooling the working gas the in working gas cooling arrangement and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades for compressing the working gas; and guiding the compressed working gas back to the working gas heating arrangement.

[0014] This design of the a closed-cycle axial flow gas turbine arrangement, in which the rotor carries both turbine blades and compressor blades, and wherein the heated working gas is guided in a first mainly axial direction to the turbine blades for rotating the rotor; and subsequently back in a second mainly axial direction to the compressor blades for compressing the working gas, provides a very compact, operating efficient and also cost efficient closed-cycle axial flow gas turbine arrangement. The compact design is the result of circulating the working fluid within the housing, to form a convoluted working gas flow, thus eliminating need to route the working gas outside of the housing. Thereby, a more cost-efficient manufacturing of the closed-cycle axial flow gas turbine arrangement is also provided, and the losses associated with long routing of the working gas can be significantly reduced.

[0015] Furthermore, an object of the present disclosure is to provide a closed-cycle axial flow gas turbine arrangement, such as a turbine engine, driven by heat and using the Stirling principle.

[0016] Specifically, the working fluid heat-powered turbine has a turbine wheel enclosing, i.e. surrounding, an axial compressor. In this way, mechanical motion of the moving parts, i.e. the rotor, is low, thereby reducing friction losses and increasing operating efficiency combined with a compact design. This allows the engine to operate at higher speeds and thus providing higher output power with just one moving part. This will also reduce the cost and complexity compared with for example a traditional piston engine. Furthermore, compared with a conventional distributed design of a closed-cycle gas turbine arrangement, in which working gas is guided out from the turbine housing, the integrated and more compact design of the a closed-cycle gas turbine arrangement according to present disclosure provides increased operating efficiency because there are less part and reduced surface area that results in heat loss, and there is less working gas circulating pumping losses.

[0017] Compared with a conventional OCR-based heat-powered turbine arrangement, the closed-cycle gas turbine arrangement according to present disclosure enables significantly higher working gas temperatures. An OCR-based heat-powered turbine arrangement can typically operate with a working medium having a maximal temperature of about 180 deg., while the working gas according to the present closed- cycle gas turbine arrangement can easily operate with a working gas temperature at 1000 deg. C.

[0018] Moreover, the closed-cycle gas turbine arrangement according to the present disclosure uses a working gas that remains in the gas phase during the flow cycle of the closed-cycle gas turbine, i.e. remains a stable and more or less compressed working gas at all operating conditions. Thereby, the closed-cycle gas turbine arrangement according to the present disclosure can eliminate need for safety valves or the like, which is typically necessary in an OCT unit that includes working gas shift from gaseous to liquid state, and oppositely, during each operating cycle.

[0019] Further advantages are achieved by implementing one or several of the features of the dependent claims.

[0020] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the axial compressor is arranged in a centre region of the gas turbine housing, when viewed in an axial direction of the gas turbine housing, wherein the rotor comprises a rotor sleeve located radially offset from and at least partly surrounding the axial compressor, and wherein the turbine blades are fastened to the rotor sleeve. The rotor sleeve provides a cost-efficient design of the gas turbine arrangement while the position of the sleeve partly surrounding the compressor enables the desired compact format of said gas turbine arrangement.

[0021] In some example embodiments, that may be combined with any one or more of the above-described embodiments, a radially outer surface of the rotor sleeve and a radially inner surface of the stationary casing jointly define a first primarily cylindrical or conical flow path through the gas turbine. This design enables simple cooling of the working gas because the working gas flows along the radially inner surface of the stationary casing, thereby enabling easily implemented heat transfer between the casing the working gas.

[0022] In some example embodiments, that may be combined with any one or more of the above-described embodiments, a radially inner surface of the rotor sleeve and a radially outer surface of the stationary casing jointly define a first primarily cylindrical or conical flow path through the gas turbine. This design provides an efficient flow path for the working gas because the working gas is circulating inside of the rotor sleeve, and thus eliminating need to enter into the rotor sleeve from outside of the rotor sleeve in the region between the turbine blades and compressor.

[0023] In some example embodiments, that may be combined with any one or more of the above-described embodiments, a radially outwards facing surface of the axial compressor and a radially inwards facing surface of the stationary casing jointly define a second primarily cylindrical or conical flow path. There the second primarily cylindrical or conical flow path is less disturbed by the rotating rotor sleeve, and the radially inwards facing surface of the stationary casing enables attachment of compressor stator vanes.

[0024] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the first working gas heating arrangement is a heat chamber configured for receiving working gas from the axial compressor via one or more inlet openings and supplying heated working gas to the gas turbine blades via one or more outlet openings, wherein the working gas within the heat chamber is configured to be heated by the external heat-source, and wherein the working gas within the heat chamber is separated from the external heat-source by a wall of the heat chamber. Thereby, the purity of the working gas be more easily maintained, thus enabling improved operational reliability and reduced maintenance requirements.

[0025] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the rotor further comprises a rotor sleeve that is coaxial with and surrounds the rotor shaft, wherein the rotor sleeve is located spaced apart from the rotor shaft in the radial direction RD, wherein the rotor sleeve is attached to the rotor shaft via a sleeve holding structure of the rotor. Thereby, the compressor and rotor sleeve can be located more or less radially overlapping for providing a compact design of the gas turbine arrangement.

[0026] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the sleeve holding structure of the rotor has one or more passages or openings in the sleeve holding structure for enabling the working gas to flow through the sleeve holding structure and further to the compressor. The sleeve holding structure can be designed with many and large openings for simplifying the flow of working gas through the sleeve holding structure. This enables the desired convoluted circulating flow of working gas within the housing of the gas turbine arrangement.

[0027] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the rotor comprises one or more rows of turbine blades and one or more rows of compressor blades, wherein the location of the one or more rows of turbine blades in the axial direction define a turbine blade region, wherein the location of the one or more rows of compressor blades define a compressor blade region, and wherein the turbine blade region is located at least partly overlapping the compressor blade region in the axial direction; or wherein the turbine blade region may be located displaced from the compressor blade region in the axial direction AD, wherein a displacement distance in the axial direction is not larger than a total length of the compressor blade region in the axial direction AD. The more or less radial overlapping arrangement of the turbine relative to the compressor blades enables the desired convoluted circulating flow of working gas within the housing of the gas turbine arrangement.

[0028] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the heat chamber is located next to and adjacent both the axial compressor and turbine blades. Thereby, the flow path between the compressor and heat chamber, and between heat chamber and turbine blades, is short, thereby enabling a compact overall design of the gas turbine arrangement.

[0029] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the heat chamber is located downstream of the axial compressor and upstream of the turbine blades. In some example embodiments, that may be combined with any one or more of the above-described embodiments, the working gas heating arrangement is located next to and upstream of the turbine blades. This ensures increased pressure of the working gas before engaging the turbines blades, which enables converting heat energy to kinetic energy.

[0030] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the working gas cooling arrangement is located in a region around the turbine shaft, downstream of the turbine blades and upstream of the axial compressor. This design enables a compact overall format of the gas turbine arrangement.

[0031] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the working gas cooling arrangement is attached to, or integrated in, the gas turbine housing. Thereby a more compact design of the gas turbine arrangement is provided.

[0032] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the closed-cycle gas turbine arrangement and the working gas are configured for keeping the working gas constantly in gaseous mode through the complete flow cycle of the working gas. This enables high operating temperature of the working gas, and thus use of high-temperature external heat sources.

[0033] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the rotor has a hollow centre shaft towards the side of the heat chamber and at least one shaft inlet opening for enabling the compressed working gas to enter into the hollow centre shaft via the shaft inlet opening and subsequently to flow through the hollow centre shaft and into the heat chamber via the inlet opening. This enables a more controlled flow of the working gas within the heat chamber, specifically entrance at a central position of the heat chamber, and subsequent exit at a peripheral position of the heat chamber.

[0034] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the closed-cycle gas turbine arrangement comprises an outlet nozzle arranged in connection with each outlet opening, and wherein each outlet nozzles protrude from the heat chamber towards the turbine blades. The outlet nozzles enables increased working gas flow speed before engaging the turbine blades, as well as the possibility to better control the flow direction of the working gas when exiting the heat chamber.

[0035] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the turbine blades are provided with a recess facing towards the heat chamber, and wherein the outlet nozzles protrude from the heat chamber towards the turbine blades, such that the hot high-pressure working gas is configured to exit from the outlet nozzle within said recesses of said turbine blades.

[0036] In some example embodiments, that may be combined with any one or more of the above-described embodiments, the gas turbine is drivingly connected to an external electrical generator that is located outside of the closed-cycle gas turbine arrangement. Thereby, the development cycle of an electrical generator may be allowed to be different from the development cycle of a gas turbine, thereby enabling improved and faster individual development of each of said components without mutual interference. As a result, replacement of one of these parts while keeping the other, is always possible, thereby ensuring optimal operating performance. Moreover, an external electrical generator that is located outside of the closed-cycle gas turbine arrangement enables simplified maintenance work of these parts individually in case of malfunction.

[0037] Further features and advantages of the invention will become apparent when studying the appended claims and the following description. The skilled person in the art realizes that different features of the present disclosure may be combined to create embodiments other than those explicitly described hereinabove and below, without departing from the scope of the present disclosure.

[0038] BRIEF DESCRIPTION OF DRAWINGS

[0039] The gas turbine arrangement and associated method according to the disclosure will be described in detail in the following, with reference to the attached drawings, in which Fig. 1 shows schematically a layout of a closed-cycle heat powered gas turbine arrangement,

[0040] Fig. 2A shows a cross-section of a first example embodiment of a more detailed example embodiment of the closed-cycle gas turbine arrangement according to the disclosure.

[0041] Fig. 2B shows a cross-section of further example embodiment of a more detailed example embodiment of the closed-cycle gas turbine arrangement according to the disclosure,

[0042] Fig. 3 shows a cross-section of an example embodiment of a housing of the gas turbine arrangement,

[0043] Fig. 4A-B show two example embodiments of the relationship between the turbine blades and compressor blades,

[0044] Fig. 5 shows a perspective view of an example embodiment of a rotor,

[0045] Fig. 6 shows a cross-section an example embodiment of an outlet nozzle,

[0046] Fig. 7 shows a further example embodiment of the closed-cycle gas turbine arrangement,

[0047] Fig. 8 schematically shows a view of the working gas heating arrangement,

[0048] Fig. 9 shows a perspective overview of the outside of the closed-cycle gas turbine arrangement,

[0049] Fig. 10A-B show two alternative example embodiments of an axial side wall of the heat chamber including inlet and outlet passages,

[0050] Fig. 11 shows a side view of the housing,

[0051] Fig. 12 shows a side view of the rotor,

[0052] Fig. 13A-F show schematically the closed flow path of six alternative designs of the of the closed-cycle gas turbine arrangement,

[0053] Fig. 14 shows a further example embodiment of the gas turbine arrangement, Fig. 15 shows a gas turbine arrangement connected to an electric generator.

[0054] DESCRIPTION OF EXAMPLE EMBODIMENTS

[0055] Various aspects of the disclosure will hereinafter be described in conjunction with the appended drawings to illustrate and not to limit the disclosure, wherein like designations denote like elements, and variations of the described aspects are not restricted to the specifically shown embodiments but are applicable on other variations of the disclosure.

[0056] Figure 1 shows a schematic layout of a closed-cycle heat powered gas turbine arrangement 7 operated with thermal cyclic working gas.

[0057] The closed-cycle heat powered gas turbine arrangement 7 generally comprises a compressor 1 , a first heat-exchanger 2 for heating the working gas, a gas turbine 3, and a second heat-exchanger 4 for cooling the working gas.

[0058] The first heat-exchanger 2 is also referred to as a working gas heating arrangement 27, and the second heat-exchanger 4 is also referred to as a working gas cooling arrangement 28.

[0059] The first heat-exchanger 2 may be configured to use nearly any type of external heat source 6 for heating the working gas. For example, the first heat-exchanger 2 may heat the working gas based on heat from solar energy, geothermal energy, combustion waste heat, industrial waste heat, bioenergy, energy derived from biomass, electrical energy via resistive conductors or heat pump or the like, laser heating, thermal radiation, friction heating, combustion heating, combustion furnace, wood or coal furnace, etc.

[0060] The second heat-exchanger 4 may use for example be a passive or forced air-cooler arrangement or a liquid-based cooling arrangement, or the like, and configured for cooling the working gas.

[0061] The compressor 1 is drivingly connected to the gas turbine 3, such that the compressor 1 is driven by the gas turbine 3. Furthermore, the gas turbine 3 may also be drivingly connected to an external or internal work unit 5, such that the work unit 5 is driven by the gas turbine 3, for performing a work task. The work unit 5 is for example an electrical generator, such that the thermal energy from the external heat source is converted first to kinetic energy by the closed-cycle heat powered gas turbine, and subsequently to electrical energy by the electrical generator. The electrical generator may be configured to generate electrical power to one or more electrical consumers.

[0062] Alternatively, the work unit 5 may be a pump configured to generate a fluid or gas flow, such as for example a water pump, hydraulic pump, air pump, etc.

[0063] As indicated above, the work unit 5 may be an external device located outside of the closed-cycle gas turbine arrangement 7, as schematically illustrated in figure 1. Alternatively, the work unit 5 may be integrated within the closed-cycle gas turbine arrangement 7, thereby providing a more compact design and potentially eliminating need for a dynamic seal of the rotational output shaft 8 of the closed-cycle heat powered gas turbine arrangement 7 for avoiding leakage of the working gas.

[0064] In continuous operation of the closed-cycle heat powered gas turbine arrangement 7, the working gas is compressed in the compressor 1. The compressed working gas is subsequently routed to the first heat-exchanger 2 and heated therein. The heated working gas is then routed to the gas turbine 3, which is caused to rotate by the hot working gas acting on the turbine blades 21 or aerofoils of the gas turbine arrangement 7. In connection with the working gas flows over the turbine blades or aerofoils 21 , the working gas is expanded and it is allowed to pass to the second heatexchanger 4 to be cooled. After the working gas is cooled by the second heatexchanger 4 it is routed back to the compressor 1 , thereby forming a closed-cycle for the working gas.

[0065] In other words, the same working gas is circulated repeatedly. The working gas performs a thermodynamic cycle, which means working fluid is circulated and used continuously again and again without leaving the gas turbine. The closed-cycle gas turbine working principle is for example based on the so-called Brayton cycle or Joule’s cycle.

[0066] The basis of operation of the closed-cycle heat powered gas turbine arrangement 7 according to the present disclosure is a turbine that is driven with the difference between hot and cold side of the gas turbine arrangement 7, similar to a basic Stirling technology, but using a turbine instead of reciprocating pistons. Consequently, both the heating capacity of the first heat-exchanger 2 and the cooling capacity of the second heat-exchanger 4 are important for obtaining a high-power output of the gas turbine arrangement 7.

[0067] Figure 2A shows a more detailed example embodiment of the closed-cycle gas turbine arrangement 7 according to the disclosure. In this example embodiment, the closed-cycle gas turbine arrangement 7 comprises a hollow gas turbine housing 13 and a gas turbine rotor 14 that is rotationally mounted within the housing 13.

[0068] In the example embodiment of figure 2A, the gas turbine housing 13 comprises a first axial side wall 16, also referred to as the low-pressure axial side wall, an oppositely located second axial side wall 17, also referred to as the high-pressure axial side wall, and an circumferential radial side wall 18 that surrounds the rotor 14, wherein the first and second side walls 16, 17 together with the circumferential side wall jointly defines the turbine housing 13.

[0069] The rotor 14 comprises a central rotor shaft 15 that extends along an axial direction AD and is rotationally mounted in the turbine housing 13, for example in the first and second side walls 16, 17 of the housing 13 via bearings 45, such as roller bearings.

[0070] The rotor shaft 15 may extend through the first side wall 16 and being suitable for being connected to an external work unit 5, and the annular space between the rotor shaft 15 and side wall 16 may be sealed by means of an annular gasket 44, thereby largely avoiding leakage of working gas at the outlet opening of the rotor shaft 15.

[0071] The rotor 14 further comprises a sleeve 20 that surrounds the rotor shaft 15 and is located spaced apart from the rotor shaft 15 in the radial direction RD. The sleeve may have an at least partly cylindrical and / or conical shape.

[0072] In the example embodiment of figure 2A, the rotor sleeve 20 is attached to the rotor shaft 15 via a sleeve holding structure 19 of the rotor 14. In the example embodiment of figure 2A, the sleeve holding structure 19 of the rotor 14 is a radial wall, i.e. flat annular disc, that is attached to and coaxial with the central shaft 15 and to the sleeve 20 of the rotor 14. However, the sleeve holding structure 19 may have other designs, such as for example conical, rounded or cup-shaped annular object. In some example embodiments, the sleeve 20 and sleeve holding structure 19 may be made in one piece, or they may be manufactured separately and subsequently fastened to each other.

[0073] In the example embodiment of figure 2A, the rotor sleeve 20 carries a set of turbine blades 21 located on a radially exterior surface of the sleeve 20. Consequently, the turbine blades 21 are located in a turbine flow passage 23 that is limited radially inwards by the exterior surface of the sleeve 20 and limited radially outwards by the interior surface of the circumferential wall 18 of the gas turbine housing 13.

[0074] The turbine blades 21 may be fastened to a portion of the sleeve 20 that is substantially cylindrical for providing a substantially cylindrical flow path of the working gas.

[0075] In some example embodiments, the sleeve 20 may include a single annular row of turbine blades 21. In other example embodiments, the sleeve 20 may include a plurality of axially spaced-apart annular rows of turbine blades 21 .

[0076] In some example embodiments, the gas turbine may include a plurality of stationary turbine stator vanes or aerofoils 31 located on the interior surface of the circumferential wall 18 of the gas turbine housing 13. The stationary turbine stator vanes or aerofoils would be located next to, and adjacent to, the turbine blades 21 of the gas turbine 3. The stationary turbine stator vanes or aerofoils may serve to increase the gas velocity and to control the gas flow direction of the closed-cycle gas turbine arrangement 7. In other example embodiments, the gas turbine may lack, i.e. be free from, stationary turbine stator vanes or aerofoils 31 located on the interior surface of the circumferential wall 18 of the gas turbine housing 13, because this provides simplified design and manufacturing.

[0077] The rotor 14 further comprises parts of the axial compressor 1. An annular inner core 24 of the compressor 1 may for example be fastened and rotationally secured to the central rotor shaft 15. Alternatively, the inner core 24 forms the central rotor shaft 15 in the area of the compressor 1 .

[0078] The axial compressor 1 comprises compressor blades or aerofoils 22 located on a radially exterior surface of the inner core 24 of the compressor 1. The inner core 24 may include a plurality of axially spaced-apart annular rows of compressor blades 22. These comprises compressor blades 22, in particular said plurality of axially spacedapart annular rows of compressor blades 22, may be located distributed over a significant length of the axial compressor 1 , in the axial direction. This distributed design of the compressor blades 22 enables improved performance and operating efficiency.

[0079] In some example embodiments, as schematically illustrated in figure 2A, the gas turbine may additionally include a plurality of stationary compressor stator vanes or aerofoils 25.

[0080] The stationary compressor stator vanes or aerofoils 25 may for example be located on a stationary compressor stator sleeve 26.

[0081] The stationary compressor stator sleeve 26 may be located inside of the sleeve portion 20 of the rotor 14, as seen in both the radial and axial directions RD, AD. In other words, the sleeve portion 20 of the rotor 14 may be arranged surrounding the stationary compressor stator sleeve 26.

[0082] The gap between the sleeve portion 20 of the rotor 14 and the stationary compressor stator sleeve 26, in the radial direction RD, may be relatively small for avoiding extensive leakage of working gas between the stationary compressor stator sleeve 26 and the sleeve portion 20 of the rotor 14. Such leakage would likely reduced efficiency of the closed-cycle gas turbine arrangement 7.

[0083] In some example embodiments, the gap between the sleeve portion 20 of the rotor 14 and the stationary compressor stator sleeve 26 may include a sealing arrangement for further reducing leakage of working gas between the stationary compressor stator sleeve 26 and the sleeve portion 20 of the rotor 14.

[0084] The stationary compressor stator vanes or aerofoils 25 are configured to be located next to, and adjacent to, the compressor blades 22. The stationary compressor stator vanes or aerofoils 25 serve to increase the gas velocity and to control the gas flow direction of the closed-cycle gas turbine arrangement 7.

[0085] The inner core 24 may have a conical shape with an increased external diameter in the intended flow direction, thereby assisting with compression of the working gas when the working gas passes through the compressor 1. In the example embodiment of figure 2A, the compressor is located within a space defined by the radial inner surface of the cylindrical sleeve portion 20 of the rotor 14. Thereby, the turbine blades 21 may be located approximately at the same, or at least close to, the position of the compressor blades 22, as seen in the axial direction AD.

[0086] In other words, with reference to figure 4A, the location of the one or more rows of turbine blades 21 define a turbine blade region 21* and the location of the one or more rows of compressor blades 22 define a compressor blade region 22*, and the turbine blade region 21* may be located at least partly overlapping the compressor blade region 22*, in the axial direction AD. Alternatively, the turbine blade region 21* may be located displaced from the compressor blade region 22*, in the axial direction AD, as schematically illustrated in figure 4B, but the displacement distance 57 in the axial direction AD is preferably not larger than a total length of the compressor blade region 22* in the axial direction AD. These designs provide a compact shape of the closed- cycle gas turbine arrangement 7, and the flow-path of the working gas is significantly reduced.

[0087] The compressor 1 is for example an axial-flow compressor. In axial-flow compressors, the working gas passes along the rotor shaft 15 of the compressor 1 through the stationary stator compressor stator vanes 25 and rotatable compressor blades 22. The compressor 1 increases the velocity and pressure of the working gas gradually while passing through the compressor 1.

[0088] In the example embodiment of figure 2A, the first heat-exchanger 2 for heating the working gas, i.e. the working gas heating arrangement 27, may be designed as a heat chamber 9, which is heated by the external heat-source 6 such that the working gas flowing within the heat chamber 9 is heated. As discussed above, the heat chamber 9 may be heated by nearly any type of external heat source 6. For example, the heat chamber 9 may be heated by solar energy, geothermal energy, bioenergy, energy derived from biomass, combustion waste heat, industrial waste heat, electrical energy via resistive conductors or heat pump or the like, laser heating, thermal radiation, friction heating, combustion heating, combustion furnace, wood or coal furnace, etc.

[0089] The interior space of the heat chamber 9 is sealed from the outside and has merely one or more inlet openings 11 and one or more outlet openings 12 for the working gas. An advantage of using the heat chamber 9 is the separation of the heating media from the working gas by the wall 10 of the heating chamber 9, thereby avoiding leakage of working gas and contamination of the working gas from the heating medium.

[0090] In other words, the external heat source 6 heats the wall 10 of the heating chamber 9, and the relatively cool working gas from the compressor 1 enters the heating chamber 9 via the inlet openings 11 . The working gas becomes heated when flowing within the heating chamber 9 due to interaction with the hot walls 10 of the heating chamber 9, and then the heated working gas exits from the heating chamber 9 via the outlet openings 12.

[0091] The flow of the working gas within the heat chamber 9 may be controlled by means of the shape of the interior walls of the heat chamber 9, and / or by means of interior stationary guide walls or vanes of the of the heat chamber 9. The flow of the working gas within the heat chamber 9 is preferably controlled to provide high efficiency in terms of heat and pressure of the working gas when exiting the heat chamber 9 via the outlet openings 12.

[0092] Increased heat-transfer efficiency from the external heat source 6 to the working gas within the heat chamber 9 may be arranged by providing the heat chamber 9 with exterior and / or interior flanges, fins, blades, protrusions or the like for increasing the surface area of the heat-transfer from the external heat source 6 to the wall 10 of the heat chamber 9, and / or from the wall 10 of the heat chamber 9 to the working gas.

[0093] The heat chamber 9, which forms part of the working gas heating arrangement 27 that is configured to heat the working gas, is located next to and adjacent both the axial compressor 1 and turbine blades 21. Specifically, the heat chamber 9 is located downstream of the axial compressor 1 and upstream of the turbine blades 21.

[0094] In other words, the working gas heating arrangement 27 is located next to and upstream of the turbine blades 14, thereby enabling a short path for the relatively cool working gas entering the working gas heating arrangement 27 from the axial compressor 1 until the heated gas exits the working gas heating arrangement 27 and enters a turbine blade region.

[0095] In this way, the closed-cycle gas turbine arrangement 7 may have a compact design.

[0096] The heater surface, shield or pipes can be designed in different geometries. In the example embodiment of figure 2A, the second heat-exchanger 4, i.e. the working gas cooling arrangement 28, for cooling the working gas is provided in a region located around the turbine shaft 15, downstream of the turbine blades 21. For example, the working gas cooling arrangement 28 may be arranged in connection with the gas turbine housing 13, in particular the circumferential wall 18 of the housing 13 and / or the first axial side wall 16, so that more or less the entire wall surface of the housing downstream of the turbine blades 21 form part of the working gas cooling arrangement 28. The interior wall surface of the gas turbine housing 13 would then absorb heat from the working gas and thus act as a working gas cooler. The absorbed heat could for example be removed from the wall surface of the housing 13 by means cold plate 35 or the like that is attached to an exterior surface of the housing 13, and heat may be removed from the cold plate 35 by a circulating liquid cooling medium that flows through the cold plate and a liquid circuit to a heat emitter, such as a liquid- to-air heat exchanger 32, or the like.

[0097] The temperature level and heat absorption capacity of the low temperature source used for cooling the working gas has direct effect on the operating efficiency of the closed-cycle gas turbine arrangement 7.

[0098] According to an alternative design, as schematically illustrated in figure 3, the circumferential wall 18 and / or first axial side wall 16 of the gas turbine housing 13 may include integrated cooling channels 35 that are fluidly connected to a coolant inlet 33 and a coolant outlet 34, such that a liquid coolant may flow through the gas turbine housing 13 instead of through a cold plate as described above with reference to figure 2A.

[0099] Moreover, as schematically illustrated in figure 3, the working gas cooling arrangement 28 may include a plurality of cooling flanges 39 attached to or integrated in the gas turbine housing 13. The cooling flanges 39 may be arranged in a region downstream of the gas turbine blades 21.

[0100] In some example embodiments, the gas turbine may include a plurality of stationary turbine stator vanes or aerofoils 31 combined with a plurality of cooling flanges 39.

[0101] The stationary turbine stator vanes or aerofoils 31 may serve to increase the gas velocity and / or to control the gas flow direction of the closed-cycle gas turbine arrangement 7, while the cooling flanges 39 are primarily configured for enabling improved cooling of the working gas. In such example embodiment, the cooling flanges 39 are located primarily downstream of the turbine stator vanes or aerofoils 31.

[0102] In other words, the gas turbine housing 13 of the example embodiments of figures 2A and 2B may be supplemented with plurality of cooling flanges 39, and the gas turbine housing 13 of the example embodiment of figure 3 may be supplemented with plurality of stationary turbine stator vanes or aerofoils 31.

[0103] According to a further example embodiment, some of the stationary turbine stator vanes or aerofoils 31 may have dual functionality in that they not only serve to control flow direction of the working gas, but also form cooling flanges 39 of the working gas cooling arrangement 28 and are configured for cooling of the working gas.

[0104] Similarly, in some example embodiment, some of cooling flanges 39 may have dual functionality in that they not only serve to cool the working gas, but also form turbine stator vanes or aerofoils 31 configured to control flow direction of the working gas.

[0105] When viewing a cross-section of the closed-cycle gas turbine arrangement 7 in operation in an axial plane, i.e. a plane that coincides with a rotational axis of the rotor, as schematically illustrated in figure 2A, the working gas is circulating in a closed flow path that includes at least four main segments: a first flow path segment 40 in which the working gas flows through the axial compressor 1 , a second flow path segment 41 in which the working gas flows through the heat chamber 9 and turns back towards the gas turbine blades 21 , a third flow path segment 42 in which the working gas flows past the gas turbine blades 21 and possibly at least partly past the working gas cooling arrangement 28, and a fourth flow path segment 43 in which the working gas possibly at least partly flows past the working gas cooling arrangement 28 and turns back towards the axial compressor, thereby ending the closed flow path.

[0106] Each of the second flow path segment 41 and fourth flow path segment 43 thus defines a turning segment of the working gas flow path.

[0107] The dashed arrows in figure 2A schematically indicates said flow path segments 40- 43 and closed flow path of the working gas in a simplified manner that essentially does not take aspects such as rotational flow around the rotor shaft, turbulence, etc. into account. The actual working gas flow path is also occurring not only in the showed crosssection of figure 2A but all around the centre axis of the rotor shaft 15, i.e. in a cylindrical and / or conical fashion between the turning segments of the working gas, wherein the flow of working gas through the gas turbine 3 essentially surrounds the flow of working gas through the axial compressor 1 , but in essentially opposite axial directions.

[0108] Other said, a cross-section of the flow of working gas through the gas turbine 3 in a first axial direction AD, in a plane that is perpendicular to the axial direction AD of the gas turbine arrangement, has essentially the form of an annulus defined by an inner ring and an outer ring, wherein the flow of working gas through the compressor 1 in a second axial direction AD that is essentially opposite to the first axial direction, is located inside said inner ring as seen in said cross-section.

[0109] The rotor comprises a rotor sleeve located radially offset from and at least partly surrounding the axial compressor, and turbine blades are fastened to the rotor sleeve. The technical effect of this feature may be deemed increased operating design flexibility with respect to axial compressor 1 and gas turbine 3. For example, the rotor sleeve 20, which is located radially offset from and at least partly surrounding the axial compressor 1 , enables individual design of the first and third flow path segments 40, 42, because first flow path segment 40 is formed by the rotor shaft 15 and inner core 24, while the third flow path segment 42 is formed by rotor sleeve 20. This design enables for example that the inner core 24 may have a conical shape with an increased external diameter in the intended flow direction, thereby assisting with compression of the working gas when the working gas passes through the compressor 1.

[0110] Moreover, the individual design and structure of the first and third flow path segments 40, 42a effectively makes individual design modifications of said first and third flow paths possible without (negatively) influencing the performance of the other flow path.

[0111] For enabling the working gas to first flow past the gas turbine blades 21 on the outer side of the rotor sleeve 20, and subsequently enabling the working gas to turn back and flow through the sleeve holding structure 19 of the rotor 14 for entering the axial compressor 1 that is located inside of the rotor sleeve 20, the sleeve holding structure structure 19.

[0112] These one or more passages or openings 46 may for example be provided in form of a plurality of openings 46 distributed around a rotational centre point of the sleeve holding structure 19.

[0113] The pressure and temperature of the working gas vary considerably during a single flow cycle through the closed flow path of the closed-cycle gas turbine arrangement 7. However, the closed-cycle gas turbine arrangement 7 according to the present disclosure is not configured for working gas phase shift during a single flow cycle of the closed-cycle gas turbine, e.g. working gas shifting from gaseous to liquid state, and oppositely, such as an OCR unit. In other words, the closed-cycle gas turbine arrangement 7 according to the present disclosure is configured for having working gas constantly in gaseous mode through each single flow cycle, i.e. without phase shift during operation of the closed-cycle gas turbine arrangement 7.

[0114] The working gas is for example air, helium, carbon dioxide, nitrogen, argon, hydrogen or the like.

[0115] The working gas is not a refrigerant gas, i.e. a cooling / heating agent that fluctuates between a liquid or gas state as it goes through the thermodynamic process, specifically at a relatively low temperature, such as for example at about 100 degC.

[0116] Merely as an example, the temperature at point A, i.e. just outside of the heat chamber 9, may for example be about 600 to 2000 deg. C, in particular when the heat source 6 is combustion gases from combustion of fossil fuels, such as coal, oil, or fossil natural gas, or combustion gases from renewal sources, such as cellulose based renewable materials, or combustion of household residual waste, etc. However, the temperature at point A can alternative be more or less than about 600 to 2000 deg. C, depending on the type of heat source 6.

[0117] The working gas temperature at point B, i.e. at the inlet opening 11 to the gas turbine 3, may depending on heat transfer efficiency and heat source, reach up to for example 1000 deg. C. Moreover, the pressure level of the working gas at point B may for example be about between 50 and 100 bar, or about 25 - 150 bar. At point C, i.e. directly downstream of the gas turbine blades 21 , after supply of work to the rotor and after a pressure drop and cooling of the working gas, the working gas may have lost pressure with ratio of about 1 :2 or better. In other words, the pressure level of the working gas at point C may for example be about between 25-50 bar, or about 12 - 75 bar.

[0118] At point D, i.e. just upstream of the axial compressor 1 , the working gas has for example been cooled down with about 100 to 200 deg. C compared with temperature at point C, and the working gas pressure may be for example about 25-50 bar, or about 12 - 75 bar.

[0119] At point E, i.e. at the inlet opening 11 of the heat chamber 9, just downstream of the axial compressor 1 , the working gas has for example been compressed by the axial compressor 1 and pressure level has increased for example at least 10 bar compared with the pressure level at point D, and / or to a pressure of at least 30 bar.

[0120] Based on these numbers, the rotor of the closed-cycle gas turbine arrangement 7 may reach a continuous operating speed of about 1000 - 20000 rpm, specifically about 5000 - 15000 rpm.

[0121] A heat insulation arrangement, such as a heat insulation layer, may be provided between the working gas heating arrangement 27, e.g. the wall 10 of the heat chamber 9, and the working gas cooling arrangement 28, e.g. the gas turbine housing 13, for improving efficiency of the closed-cycle gas turbine arrangement 7.

[0122] Figure 2B shows a similar embodiment of the closed-cycle gas turbine arrangement 7 as described above with reference to figure 2A, but differing in that the rotor sleeve 20 carries the set of turbine blades 21 on a radially inner surface of the sleeve 20. Consequently, the turbine blades 21 are located in a turbine flow passage 23 that is limited radially inwards by the exterior surface of the compressor stator sleeve 26 of the gas turbine housing 13, and limited radially outwards by the interior surface of the sleeve 20.

[0123] The turbine blades 21 may be fastened to a portion of the sleeve 20 that is substantially cylindrical for providing a substantially cylindrical flow path of the working gas. In some example embodiments, the sleeve 20 may include a single annular row of turbine blades 21. In other example embodiments, the sleeve 20 may include a plurality of axially spaced-apart annular rows of turbine blades 21 , as illustrated in figure 2B.

[0124] In some example embodiments, the gas turbine may include a plurality of stationary turbine stator vanes or aerofoils 31 located on the exterior surface of the compressor stator sleeve of the gas turbine housing 13. The stationary turbine stator vanes or aerofoils 31 would be located next to, and adjacent to, the turbine blades 21 of the gas turbine 3. The stationary turbine stator vanes or aerofoils 31 may serve to increase the gas velocity and to control the gas flow direction of the closed-cycle gas turbine arrangement 7. In other example embodiments, the gas turbine may lack, i.e. be free from stationary turbine stator vanes or aerofoils located on the exterior surface of the compressor stator sleeve of the gas turbine housing 13, because this provides simplified design and manufacturing.

[0125] In the example embodiment of figure 2B, the working gas cooling arrangement 28 for cooling the working gas may be arranged in connection with the circumferential wall 18 of the housing 13 and / or the first axial side wall 16, so that more or less the entire wall surface of the housing downstream of the turbine blades 21 form part of the working gas cooling arrangement 28. The interior wall surface of the gas turbine housing 13 would then absorb heat from the working gas and thus act as a working gas cooler. The absorbed heat could for example be removed from the wall surface of the housing 13 by means cold plate 35 or the like, similar as described above with reference to figure 2A.

[0126] Cooling of the working gas may also, or alternatively, be provided by integrating the cooler in the compressor stator sleeve 26, for example by means of integrated cooling channels within the compressor stator sleeve 26, and / or by means of a cold plate 35 or the like that is attached to the compressor stator sleeve 26.

[0127] A significant advantage with the example embodiment of figure 2B is that the working gas does not need to enter from the outside of the rotor 14 into the rotor via the openings 46 in sleeve holding structure 19, because the working gas is passing through the gas turbine 3 on the inside of the rotor sleeve 20. This design may thus enable an improved flow path in the fourth flow path segment 43, i.e. the location of the working gas turns back towards the axial compressor 1.

[0128] Figure 5 schematically illustrates a perspective view of a further example embodiment of the rotor 14 comprising a central rotor shaft 15, a sleeve 20 that surrounds the rotor shaft 15 and is located spaced apart from the rotor shaft 15 in the radial direction, a sleeve holding structure 19 of the rotor 14 in form of an annular plate having a plurality of distributed openings 46 for enabling the working gas to enter into the interior side of the rotor 14.

[0129] The rotor 14 of figure 5 further comprises a row of turbine blades 21 attached to an exterior side of the sleeve 20 and configured to incur rotational motion to, and thus drive, the turbine 14, upon being exposed to hot high-velocity and high-pressure working gas from the heat chamber 9.

[0130] The hot working gas may for example be conveyed from the heat chamber 9 to the turbine blades 21 via a plurality of distributed outlet nozzles 37 arranged in connection with the plurality of outlet opening 12 of the heat chamber 9.

[0131] The outlet nozzles 37 may be directed to provide an axial flow of the hot working gas on the turbine blades 21 , or a slightly inclined flow direction with respect to the axial direction AD, depending on the type and design of the turbine blades 12.

[0132] The rotor 14 further comprises the axial compressor 1 having an annular inner core 24 that is rotationally connected with the central rotor shaft 15, and a row of compressor blades or aerofoils 22 located on a radially exterior surface of the inner core 24. The compressor 1 is rotationally connected with the turbine blades 21 via the sleeve 20, sleeve holding structure 19, and rotor shaft 15. Consequently, the compressor 1 is powered, i.e. caused to rotate, by the hot working gas acting on the turbine blades 21 , such that the pressure level of the cooled working gas entering the rotor via the openings 46 is increased when passing through the compressor 1 , on the way back to the heat chamber 9.

[0133] The dashed arrows in figure 5 represent the flow path segments 40-43 of the closed flow path of the working gas in a simplified manner, as described above with reference to figure 2A. Figure 6 schematically shows a cross-section of an example embodiment of the outlet nozzle 37 having an inlet side 58, an outlet side 59, a convergent section 60 arranged adjacent the inlet side 58, divergent section 62 arranged adjacent the outlet side 59, and a throat section 61 arranged between the convergent and divergent sections 60, 62.

[0134] This design of the outlet nozzle is configured such that high pressure and low velocity working gas located at the inlet side 58 of the nozzle 27 is transformed to low pressure and high velocity working gas at the outlet side 59 of the output nozzle 37, thereby enabling propelling the turbine to high rotational speed.

[0135] Figure 7 shows an example embodiment of the closed-cycle gas turbine arrangement 7 similar to that described above with reference to figure 2A and figure 5, but differing with respect to for example the rotor 14, the compressor stator 26, and the heat chamber 9.

[0136] Reference is also made to figures 8, 9, 10A, 11 , 12 which show more details of the closed-cycle gas turbine arrangement 7 according to figure 7. Specifically, figure 8 schematically shows a separate view of the working gas heating arrangement 27 including a hemispherical-shaped heat chamber 9, figure 9 schematically shows a 3D-view the closed-cycle gas turbine arrangement 7 including the hemispherical heat chamber 9, figure 10A schematically shows a axial view of the high-pressure axial side wall 17 having a centrally arranged inlet opening 11 and a plurality of outlet openings 12 distributed peripherally around the inlet opening 11 , figure 11 schematically shows a separate view the stationary gas turbine housing 13, and figure 12 schematically shows a separate view the rotor 14.

[0137] With reference to figures 7-9, 10A and 11-12, the working gas heating arrangement 27 may be formed as closed cavity heat chamber 9 having a hemisphere shape for enabling improved working gas flow distribution within the heat chamber 9, particularly in combination with a centrally arranged inlet opening 11 and peripherally located outlet openings 12, because this design enables a smooth and evenly distributed flow of working gas within the heat chamber 9, such that feeding of high pressure working gas to the rotor motion may be provided.

[0138] Figure 9 schematically shows a cylindrical turbine housing 13 with the wall 10 of a hemisphere-shaped heat chamber 9 at an axial end of the turbine housing 13. The heat chamber 9 may have another shape and / or internal walls or working gas flow deflectors, depending on the circumstances, such as the position of the inlet and outlet openings 11 , 12, for providing the desired smooth and evenly distributed flow of working gas.

[0139] Moreover, the closed cavity heat chamber 9 may have internal heating flanges, fins, blades, protrusions or the like 48 for improved heat-transfer capacity from the external heat source 6 to the working gas within the heat chamber 9. The internal heating flanges 48 or the like are preferable adapted to assist with forming said smooth and evenly distributed flow of working gas within the heat chamber 9. The internal heating flanges 48 illustrated in figure 8 are merely schematically illustrated.

[0140] As schematically illustrated in figure 8, the rotor 14 may be provided with a hollow centre shaft 38 towards the side of the heat chamber 9, as well as at least one integrated shaft inlet opening 49 in the rotor shaft for enabling the compressed working gas to enter into the hollow centre shaft 38, and to subsequently flow through the hollow centre shaft 38 and into the heat chamber 13 via the inlet opening 11 .

[0141] In such a scenario, the bearing 45 for the rotor shaft may for example be located on an exterior surface of the hollow centre shaft 38.

[0142] According to an alternative example embodiment, as schematically illustrated in figure 10B, the compressed working gas may simply flow into the heat chamber 13 from the axial compressor 1 via a plurality of inlet openings 11 . Such design enables use of a more conventional and less complex rotor shaft, such as a solid rotor shaft. The inlet openings 11 may for example be arranged in a centre region of the heat chamber 9, as seen in an axial view.

[0143] The heat chamber 9 may be open towards the second axial side wall 17 of the turbine housing 13, which includes the inlet and outlet openings 11 , 12. Alternatively, the heat chamber 9 may include a separate side wall that is configured to abut against, or at least face, the second axial side wall 17 of the turbine housing 13.

[0144] The working gas within the heat chamber 9 is shielded from the external heat source 6 by the wall 10 of the heat chamber 9. In other words, the working gas is configured to be heated by the external heat source 6 through said side wall 10. With reference in particular to figures 5-8, the closed-cycle gas turbine arrangement 7 may include an outlet nozzle 37 arranged in connection with each outlet opening 12. The outlet nozzles 37 protrude from the heat chamber 9 towards the turbine blades 21 , thereby ensuring that the outlet of the hot high-pressure working gas occurs at a suitable location with reference to the turbine blades, for providing a high operating efficiency.

[0145] The outlet nozzles 37 may for example be elongated hollow members, such as cylindrical tubes or the like. The outlet nozzles 37 may have an inlet opening configured to receive hot working gas from the heat chamber 9, and an outlet opening located more or less directly in front of, i.e. upstream of, the turbine blades 21.

[0146] In other words, the outlet nozzles 37 may protrude from the heat chamber 9 towards the turbine blades 21 , such that the hot high-pressure working gas is configured to exit from the outlet nozzle directly upstream of the turbine blades, thereby ensuring that the hot working gas is guided directly towards the turbine blades 21 , such that a high operating efficiency is provided.

[0147] The closed-cycle gas turbine arrangement 7 may for example include 3 to 30 outlet openings 12, specifically 5 to 15 outlet openings 12, located in the heat chamber 9 and configured to act as supply holes for hot high-pressure working gas for driving the turbine blades 21. Each, or at least some, of the outlet openings 12 may be provided an outlet nozzle 37 that protrudes towards the turbine blades 21.

[0148] In some example embodiments, as schematically illustrated in figures 7 and 12, each of the turbine blades 21 located next to the heat chamber 9 may include a recess 50 in the turbine blade 21 configured to receive a portion of the outlet nozzle 37. The outlet nozzle 37 is thus configured to extend rearwards in the axial direction AD and into said recess 63. This may enable improved efficiency in certain application.

[0149] The recess 50 of the turbine blades 21 is thus facing towards the heat chamber 9. Moreover, the outlet nozzles 37 may protrude from the heat chamber 9 towards the turbine blades 21 , such that the hot high-pressure working gas is configured to exit from the outlet nozzle within said recesses 50 of said turbine blades 21 . In other words, the outlet nozzles 37 may protrude from the heat chamber 9 towards the turbine blades 21 , such that the second end of the outlet nozzle is located within said recess 50 of the turbine blades 21.

[0150] The rear side of the recess 50 in the turbine blades 21 may have an opening facing rearwards in the axial direction AD, i.e. away from the heat chamber 9 for increased working gas outlet. In some example embodiments, such as in figure 7, said opening in the recess 50 may correspond to an expansion outlet 63, i.e. an outlet opening with gradually or stepwise increased opening area.

[0151] With reference in particular to figure 7 and 11 , the turbine housing 13 may be provided with a working gas flow deflector 52 configured for acting as a working gas funnel that routes the working gas exiting from the axial compressor 1 to have a more focused and centralised flow.

[0152] In some example embodiments, the working gas flow deflector 52 is formed by a radial wall 47 of the compressor stator 26. Hence, the radial wall 47 may function as an inner wall that separates heat chamber 9 from rotor. Moreover, the central rotor shaft 38 may be supported by roll bearings in the inner wall.

[0153] A more focused and centralised flow of working gas exiting from the axial compressor 1 may have beneficial effect on gas flow and heat transfer efficiency within the heat chamber 9.

[0154] The working gas flow deflector 52 may be connected to, or form part of, the compressor stator sleeve 26. Alternatively, the working gas flow deflector 52 may be located within the heat chamber 9.

[0155] The working gas flow path within the closed-cycle gas turbine arrangement 7 will depend on design of the closed-cycle gas turbine arrangement 7, and figures 13A- 13F schematically indicates the closed flow path of six alternative designs of the of the closed-cycle gas turbine arrangement 7, in cross-sectional views similar to that of figure 2A.

[0156] Specifically, figure 13A shows a closed flow path of the working gas similar to that of figure 2A having a substantially conical expending flow path through the first flow path segment 40, i.e. through the axial compressor 1 , and substantially cylindrical flow path through the third flow path segment 42, i.e. past the gas turbine blades 21 .

[0157] Figure 13B shows a closed flow path of the working gas similar to that of figure 7 having a substantially conical expending flow path through the first flow path segment 40, i.e. through the axial compressor 1 , but with a flow deflection at the end of the compressor for obtaining a more focused and centralised flow. Such a flow deflection may for example be caused by a working gas flow deflector 52, as described with reference to figures 7 and 11 above.

[0158] Figure 13C shows a closed flow path of the working gas similar to that of figure 7 but having a more axial flow path through the first flow path segment 40, i.e. through the axial compressor 1. The design of the axial compressor 1 and / or the compressor stator sleeve 26 may be adjusted to provide the desired flow pattern through the axial compressor 1. For example, the design of the axial compressor 1 and / or the compressor stator sleeve 26 may be configured to provide tapered contracting flow pattern as schematically illustrated in figure 13F.

[0159] Figure 13D schematically shows a closed flow path of the working gas similar to that of figure 13C, but with a conical expending flow path through the third flow path segment 42, i.e. past and / or immediately after the gas turbine blades 21. The volume expansion in third flow path segment 42 may assist in providing a high flow of working gas past the turbine blades 21. Figure 13D also shows a substantially cylindrical flow path through the first flow path segment 40, i.e. past the axial compressor 1 , but this flow may be adjusted as described above.

[0160] According to still a further example embodiment, the closed-cycle gas turbine arrangement 7 may be configured to provide a substantially conical expending flow path through the first flow path segment 40, i.e. through the axial compressor 1 , combined with a conical expanding flow path through the third flow path segment 42, i.e. past and / or immediately after the gas turbine blades 21.

[0161] In general, the closed-cycle gas turbine arrangement 7 converts the gaseous energy of the working gas exiting the heat chamber 9 into mechanical energy to drive the axial compressor 1 and any type of work unit 5, either directly or via a reduction gear or the like. The gas turbine 3 converts gaseous energy into mechanical energy by expanding the hot, high-pressure gases to a lower temperature and pressure. The gas turbine 3 may include one or more rows of turbine blades 21. In some example embodiments, as schematically illustrated in figure 2A and 2B, a row of stationary vanes 31 may be located ahead of a row of turbine blades 21 to form a stage, such that each stage of the turbine consists of a row of stationary vanes 31 followed by a row of rotating turbine blades 21. The turbine stator vanes 31 increase gas velocity, and then the turbine blades 21 extract energy.

[0162] The turbine stator vanes 31 and turbine blades 21 are air foils that provide for a smooth flow of the working gas. The working gas is accelerated through the turbine stator vanes 31 , because the stator vanes 31 generally form convergent ducts that accelerates the gas and directs the flow of working gas onto the turbine blades 21 at a more optimum angle.

[0163] As the mass of the high velocity working gas flows across the turbine blades 21 , the gaseous energy is converted to mechanical energy to generate shaft power. In other words, velocity, temperature, and pressure of the working gas is transformed to kinetic energy of the rotor 14.

[0164] In the axial flow compressor 1 , each stage incrementally boosts the pressure from the previous stage. A single stage of compression consists of a set of compressor blades 22 attached to the inner core 24 of the rotor 14, or the like, followed by stationary compressor stator vanes 25 attached to the stationary compressor stator sleeve 26.

[0165] In general terms, the compressor blades 22 convert mechanical energy into gaseous energy. This energy conversion increases total pressure of the working gas. Most of the increase is in the form of working gas velocity, with a small increase in static pressure.

[0166] The compressor stator vanes 25 are typically shaped to slow the working gas by means of their divergent duct shape, thereby converting the accelerated velocity to higher static pressure. The compressor stator vanes 25 are positioned at an angle such that the exiting working gas is directed into the compressor blades 22 of the next stage at the most efficient angle. This process is repeated for each stage of the axial compressor 1.

[0167] In the example embodiment of figure 14, the working gas heating arrangement 27 for heating the working gas may be designed as a pipe structure 53, which is configured to be exposed to the external heat source 6 and is arranged to guide the working gas from the inlet opening 11 to the plurality of outlet openings 12. Specifically, the pipe structure 53 may include an inlet pipe 54 fluidly connected to the inlet opening 11 of the gas turbine housing 13, a plurality of outlet pipes 55 fluidly connected to the outlet openings 12 of the gas turbine housing 13, wherein the inlet and outlet pipes 54, 55 are mutually connected somewhere in the pipe structure 53, such as a central connection point or the like.

[0168] As discussed above, the pipe structure 53 may be heated by nearly any type of external heat source 6. For example, the pipe structure 53 may be heated by solar energy, geothermal energy, combustion waste heat, industrial waste heat, electrical energy via resistive conductors or heat pump or the like, laser heating, thermal radiation, friction heating, combustion heating, combustion furnace, wood or coal furnace, etc.

[0169] The interior space of the pipes of the pipe structure 53 is sealed from the outside and has merely said one or more inlet openings 11 and one or more outlet openings 12 for the working gas. Consequently, the working gas is sealed from combustion gas or the like from the external heat source, thereby avoiding leakage of working gas and contamination of the working gas from the heating medium.

[0170] The flow 32 of the working gas within the pipe structure 53 may be easily controlled by means of the shape and / or routing of the pipes of the pipe structure, such that the flow 32 of the working gas within the pipe structure results in high-efficiency in terms of heat and pressure of the working gas when exiting the pipe structure via the outlet openings 12.

[0171] Figure 15 shows the closed-cycle gas turbine arrangement 7 as described with reference to figure 7, but additionally with an electric machine 56 operatively connected to the rotor shaft 15. The electric machine 56 may then for example be used for driving the rotor of the closed-cycle gas turbine arrangement 7 during a start sequence of the closed-cycle gas turbine arrangement 7, until the circulating flow of working gas causes the gas turbine 3 to generate sufficient power for driving the rotor 14 by itself. Thereafter, the rotor 14 will start driving the rotor of the electric machine 56, such that the electric machine 56 can start delivering electrical power to any type of external electrical consumers. In such a scenario, the combination of closed-cycle gas turbine arrangement 7 and electric machine 56 will convert heat from the external heat source 6 to electrical power.

[0172] A drive transmission may be provided between the outlet shaft 15 and electric machine 56 for reducing the rotational speed of the drive shaft driving the electric machine 56 to a lower operating range, that is compatible with the electric machine 56, such as for example 1500 or 3000 rpm.

[0173] In all example embodiments of the closed-cycle gas turbine arrangement 7 described herein, the compressor stator sleeve 26 and / or flow deflector 52 may be configured for also leading residual heat from the working gas flowing through the axial compressor 1 back to working gas that flows past the gas turbine blades 21 , for example by means of thermal conduction through the metal material of compressor stator sleeve 26 and / or flow deflector 52.

[0174] Consequently, in view of the example embodiments described above with reference to figures 1 - 15, the present disclosure relates to a closed-cycle axial flow gas turbine arrangement 7 comprising a gas turbine housing 13 and a rotor 14, a working gas heating arrangement 27, and a working gas cooling arrangement 28.

[0175] The gas turbine housing 13 is typically stationary while the rotor is rotatable.

[0176] The rotor 14 comprises turbine blades 21 , a rotor output shaft 15 and an axial compressor 1.

[0177] The axial compressor 1 comprises compressor blades 22 configured to drive the working gas towards the working gas heating arrangement 27 for increasing the pressure of the working gas within said working gas heating arrangement 27.

[0178] The turbine blades 21 and compressor blades 22 are arranged on some rotatable part, i.e. on the rotor 14. The turbine blades 21 are located on turbine rotational power generating part of the rotor. The high-pressure working gas acting on the turbine blades 21 generates rotational torque on the rotor 14, which therefore starts to rotate. Consequently, the turbine rotational power generating part drives the compressor.

[0179] The gas turbine housing 13 may include stationary gas turbine stator vanes 31 and / or stationary compressor stator vanes 25 for improved operating efficiency. In some example embodiments, the closed-cycle axial flow gas turbine arrangement comprises an axial flow gas turbine 3, wherein the compressor 1 is an axial flow compressor 1.

[0180] The working gas heating arrangement 27 is located in connection to, or in, a high- pressure section 29 of the gas turbine arrangement 7.

[0181] The working gas cooling arrangement 28 is located in connection to, or in, a low- pressure section 30 of the gas turbine arrangement 7.

[0182] Operation of the closed-cycle axial flow gas turbine arrangement 7 for converting thermal energy, i.e. heat, to kinetic energy by a thermal cyclic working gas operation includes the following operational events that are all occurring simultaneously and continuously: heating the working gas by an external heat source in the working gas heating arrangement 27; guiding the heated working gas in a first mainly axial direction to the turbine blades 21 for rotating the rotor 14; cooling the working gas the in working gas cooling arrangement 28 and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades 22 for compressing the working gas; and guiding the compressed working gas back to the working gas heating arrangement 27.

[0183] The heated working gas typically includes minor detours, swirls and circumferential and radial flow components, while being guiding in a first mainly axial direction from the high-pressure section 29 towards the low-pressure section 30. However, the main flow direction is mainly parallel with the axial direction AD of the closed-cycle axial flow gas turbine arrangement 7.

[0184] In connection with cooling of the working gas the in working gas cooling arrangement 28, the working gas is guided radially inwards towards a centre axis of the rotor, and subsequently back in a second mainly axial direction, from the low-pressure section 29 towards the high-pressure section 30. The working gas flowing through the compressor 1 thus flows radially inside of, radially surrounded by, the working gas acting on the turbine blades 21 .

[0185] Consequently, the first mainly axial direction is substantially opposite to the second mainly axial direction. In other words, the largest component of the first direction is located in axial direction and opposite to the largest component of the second direction.

[0186] Preferably, the turbine blades 21 are located radially outside of the compressor blades 22, meaning that the compressor 1 is arranged centrally in the closed-cycle axial flow gas turbine arrangement 7 and the turbine rotational power generating part is located surrounding the compressor 1 . However, in other example embodiments, the working gas closed-cycle axial flow gas turbine arrangement 7 may have the opposite configuration, such that the turbine blades 21 are located radially inside of the compressor blades 22, meaning that the turbine rotational power generating part is arranged centrally in the closed-cycle axial flow gas turbine arrangement 7 and the compressor 1 is located surrounding the turbine rotational power generating part.

[0187] In some example embodiments, the axial compressor 1 is arranged in a centre region of the gas turbine housing 13 when viewed in an axial direction of the gas turbine housing 13, wherein the rotor comprises an at least partly cylindrical and / or conical rotor sleeve 20 located radially offset from and at least partly surrounding in the radial direction RD the axial compressor, and wherein the turbine blades 21 are fastened to the rotor sleeve 20.

[0188] The flow area at an inlet region of the axial compressor 1 may be larger than the flow area at an outlet region of the axial compressor 1. This design ensures a wedge- shaped, i.e. a gradually smaller, flow area through the axial compressor 1. The flow area may be measured in a cross-sectional view of the closed-cycle gas turbine arrangement, with the section located in a plane perpendicular to an axial direction of the closed-cycle gas turbine arrangement.

[0189] Depending on design, the compressor 1 , in particular the compressor blades 22, may be arranged at least partly radially overlapping with turbine blades 21 , for providing a compact overall design.

[0190] In some example embodiments, a radially outer surface of the rotor sleeve and a radially inner surface of the stationary casing jointly define a first primarily cylindrical or conical flow path extending mainly in axial direction through the gas turbine 3 from the high-pressure region towards the low pressure region. In other example embodiments, a radially inner surface of the rotor sleeve and a radially outer surface of the stationary casing, specifically a sleeve portion of the stationary casing, and more specifically a compressor stator sleeve 26, jointly define a first primarily cylindrical or conical flow path extending mainly in axial direction through the gas turbine 3 from the high pressure region towards the low pressure region.

[0191] In some example embodiments, a radially outwards facing surface of the axial compressor 1 and a radially inwards facing surface of the stationary casing, specifically a sleeve portion of the stationary casing, and more specifically a compressor stator sleeve 26, jointly define a second primarily cylindrical or conical flow path extending mainly in axial direction from the low pressure region towards the high pressure region.

[0192] The first and second flow paths extend in substantially opposite directions, in particular opposite axial directions.

[0193] Moreover, the second flow path is preferably located radially inside of the first flow path. Others said, the second flow path is an axial flow path that radially surrounds the first flow path.

[0194] In some example embodiments, the first working gas heating arrangement 27 is a heat chamber 9 configured for receiving working gas from the axial compressor 1 via one or more inlet openings 11 and supplying heated working gas to the gas turbine blades 21 via one or more outlet openings 12, wherein the working gas within the heat chamber 9 is configured to be heated by the external heat-source 6, and wherein the working gas within the heat chamber 9 is separated from the external heat-source 6 by a wall 10 of the heat chamber 9.

[0195] In some example embodiments, the rotor 14 further comprises a rotor sleeve 20 that is co-axial with and surrounds the rotor shaft 15, wherein the rotor sleeve 20 is located spaced apart from the rotor shaft 15 in the radial direction RD, wherein the rotor sleeve 20 is attached to the rotor shaft 15 via a sleeve holding structure 19 of the rotor 14.

[0196] The rotor shaft 15 may be solid rotor shaft 15, thereby enabling a simple and efficient implementation, as well as an increased flow volume of the first flow path segment 40. The sleeve holding structure 19 may be formed as a flange, specifically a centre flange, arranged on the rotor shaft 15.

[0197] In some example embodiments, the sleeve holding structure 19 of the rotor 14 has one or more passages or openings 46 in the sleeve holding structure 19 for enabling the working gas to flow through the sleeve holding structure 19, specifically from an exterior side of the sleeve holding structure 19 to an interior side of the sleeve holding structure 19, and further to the compressor 1 .

[0198] In some example embodiments, the rotor comprises one or more rows of turbine blades 21 and one or more rows of compressor blades 22, wherein the location of the one or more rows of turbine blades 21 in the axial direction AD define a turbine blade region 21*, wherein the location of the one or more rows of compressor blades 22 define a compressor blade region 22*, and wherein the turbine blade region 21* is located at least partly overlapping the compressor blade region 22* in the axial direction AD.

[0199] Alternatively, the turbine blade region 21* may be located displaced from the compressor blade region 22* in the axial direction AD, wherein a displacement distance 57 in the axial direction AD is not larger than a total length of the compressor blade region 22* in the axial direction AD.

[0200] In some example embodiments, the heat chamber 9 is located next to and adjacent both the axial compressor 1 and turbine blades 21.

[0201] In some example embodiments, the heat chamber 9 is located downstream of the axial compressor 1 and upstream of the turbine blades 21.

[0202] In some example embodiments, the working gas heating arrangement 27 is located next to and upstream of the turbine blades 14.

[0203] In some example embodiments, the working gas cooling arrangement 28 is arranged in a region located around the turbine shaft 15, downstream of the turbine blades 21 and upstream of the axial compressor 1. In some example embodiments, the working gas cooling arrangement 28 is attached to, or integrated in, the gas turbine housing 13.

[0204] In some example embodiments, the closed-cycle gas turbine arrangement 7 and the working gas are configured for keeping the working gas constantly in gaseous mode through the complete flow cycle of the working gas.

[0205] In some example embodiments, the rotor 14 has a hollow centre shaft 38 towards the side of the heat chamber 9 and at least one shaft inlet opening 49 for enabling the compressed working gas to enter into the hollow centre shaft 38 via the shaft inlet opening 49 and subsequently to flow through the hollow centre shaft 38 and into the heat chamber 13 via the inlet opening 11.

[0206] In some example embodiments, the closed-cycle gas turbine arrangement 7 comprises an outlet nozzle 37 arranged in connection with each outlet opening 12, and wherein each outlet nozzles 37 protrude from the heat chamber 9 towards the turbine blades 21.

[0207] In some example embodiments, the turbine blades 21 are provided with a recess 50 facing towards the heat chamber 9, and wherein the outlet nozzles 37 protrude from the heat chamber 9 towards the turbine blades 21 , such that the hot high-pressure working gas is configured to exit from the outlet nozzle within said recesses 50 of said turbine blades 21.

[0208] The disclosure also relates to a method for operating a closed-cycle axial flow gas turbine arrangement 7 with working gas for converting thermal energy to kinetic energy. The closed-cycle gas turbine arrangement 7 comprises a gas turbine housing 13, a rotor 14 carrying turbine blades 21 and being operably connected to a rotor output shaft 15, an axial compressor 1 comprising compressor blades 22 located on the rotor 14, a working gas heating arrangement 27, and a working gas cooling arrangement 28.

[0209] The method comprises the following steps: heating the working gas in the working gas heating arrangement 27; guiding the heated working gas in a first mainly axial direction to the turbine blades 21 for rotating the rotor 14; cooling the working gas the in working gas cooling arrangement 28 and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades 22 for compressing the working gas; and guiding the compressed working gas back to the working gas heating arrangement 27.

[0210] It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof.

[0211] Moreover, the present disclosure discloses several schematically illustrated example embodiments of the gas turbine arrangement. For example, figures 2A, 2B, 7, 14 and 15 show larger overviews of different example embodiments of the gas turbine arrangement while figures 3-6, 8, 9, 10A-B, 11 , 12, 13A-F show various details or features of the gas turbine arrangement, and it is intended that details or features described with reference to figures 3-6, 8, 9, 10A-B, 11 , 12, 13A-F is not limited to a specific example embodiment of the gas turbine arrangement, but can be applied and combined with any example embodiment of the gas turbine arrangement.

[0212] Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims. Reference signs mentioned in the claims should not be seen as limiting the extent of the matter protected by the claims, and their sole function is to make claims easier to understand.

[0213] REFERENCE SIGNS

[0214] 1 : Compressor 5: Work unit

[0215] 2: First heat-exchanger 6: External heat source

[0216] 3: Gas turbine 7: Closed-cycle gas turbine

[0217] 4: Second heat-exchanger 35 arrangement 8: Rotational output shaft 34: Coolant outlet

[0218] 9: Heat chamber 35: Cooling channel

[0219] 10: Wall of heat chamber 36: Cold plate

[0220] 11 : Inlet opening to heat chamber 35 37: Outlet nozzle

[0221] 12: Outlet opening from heat 38: Hollow shaft of axial compressor chamber 39: Cooling flange

[0222] 13: Gas turbine housing 40: First flow path segment

[0223] 14: Rotor 41 : Second flow path segment

[0224] 15: Rotor shaft 40 42: Third flow path segment

[0225] 16: First axial side wall 43: Fourth flow path segment

[0226] 17: Second axial side wall 44: Gasket for rotor shaft

[0227] 18: Circumferential wall 45: Bearing for rotor shaft

[0228] 19: Sleeve holding structure of rotor 46: Opening in sleeve holding

[0229] 20: Rotor sleeve 45 structure

[0230] 21 : Turbine blade 47: Radial wall of compressor stator

[0231] 21*: Turbine blade region 48: Heating flange

[0232] 22: Compressor blade 49: Shaft inlet opening

[0233] 22*: Compressor blade region 50: Recess

[0234] 23: Turbine flow passage 50 51 : Rotational movement of rotor

[0235] 24: Inner core 52: Flow deflector

[0236] 25: Compressor stator vanes 53: Pipe structure

[0237] 26. Compressor stator sleeve 54: Inlet pipe

[0238] 27: Working gas heating 55: Outlet pipe arrangement 55 56: Electric machine

[0239] 28: Working gas cooling 57: Displacement distance arrangement 58: Inlet side

[0240] 29: High-pressure section 59: Outlet side

[0241] 30: Low-pressure section 60: Convergent section

[0242] 31 : T urbine stator vane 60 61 : Throat

[0243] 32: Liquid-to-air heat exchanger 62: Divergent section

[0244] 33: Coolant inlet 63: Expansion outlet

Claims

1. 39CLAIMS1. A closed-cycle axial flow gas turbine arrangement (7) comprising: a gas turbine housing (13); a rotor (14) carrying turbine blades (21) and being operably connected to a rotor output shaft (15); an axial compressor (1) comprising compressor blades (22) located on the rotor (14); a working gas heating arrangement (27), and a working gas cooling arrangement (28); wherein the gas turbine arrangement (7) is configured for converting thermal energy to kinetic energy by a thermal cyclic working gas operation involving: heating the working gas in the working gas heating arrangement (27), guiding the heated working gas in a first mainly axial direction to the turbine blades (21) for rotating the rotor (14), cooling the working gas the in working gas cooling arrangement (28) and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades (22) for compressing the working gas, and guiding the compressed working gas back to the working gas heating arrangement (27).

2. The closed-cycle gas turbine arrangement (7) according to claim 1, wherein the axial compressor (1) is arranged in a centre region of the gas turbine housing (13), wherein the rotor comprises a rotor sleeve (20) located radially offset from and at least partly surrounding the axial compressor, and wherein the turbine blades (21) are fastened to the rotor sleeve (20).

3. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein a radially outer surface of the rotor sleeve (20) and a radially inner surface of the stationary casing jointly define a first primarily cylindrical or conical flow path through the gas turbine (3); or40 wherein a radially inner surface of the rotor sleeve (20) and a radially outer surface of the stationary casing jointly define a first primarily cylindrical or conical flow path through the gas turbine (3).

4. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein a radially outwards facing surface of the axial compressor and a radially inwards facing surface of the stationary casing jointly define a second primarily cylindrical or conical flow path.

5. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the first working gas heating arrangement (27) is a heat chamber (9) configured for receiving working gas from the axial compressor (1) via one or more inlet openings (11) and supplying heated working gas to the gas turbine blades (21) via one or more outlet openings (12), wherein the working gas within the heat chamber (9) is configured to be heated by the external heat-source 6, and wherein the working gas within the heat chamber (9) is separated from the external heat-source 6 by a wall (10) of the heat chamber (9).

6. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the rotor (14) further comprises a rotor sleeve (20) that is coaxial with and surrounds the rotor shaft (15), wherein the rotor sleeve (20) is located spaced apart from the rotor shaft (15) in the radial direction RD, wherein the rotor sleeve (20) is attached to the rotor shaft (15) via a sleeve holding structure (19) of the rotor (14).

7. The closed-cycle gas turbine arrangement (7) according to claim 6, wherein the sleeve holding structure (19) of the rotor (14) has one or more passages or openings (46) in the sleeve holding structure (19) for enabling the working gas to flow through the sleeve holding structure (19) and further to the compressor.

8. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the rotor comprises one or more rows of turbine blades (21) and one or more rows of compressor blades (22), wherein the location of the one or more rows of turbine blades (21) in the axial direction (AD) define a turbine blade41 region (21*), wherein the location of the one or more rows of compressor blades (22) define a compressor blade region (22*), and wherein the turbine blade region (21*) is located at least partly overlapping the compressor blade region (22*) in the axial direction (AD); or wherein the turbine blade region (21*) may be located displaced from the compressor blade region (22*) in the axial direction AD, wherein a displacement distance (57) in the axial direction (AD) is not larger than a total length of the compressor blade region (22*) in the axial direction AD.

9. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the heat chamber (9) is located next to and adjacent both the axial compressor (1) and turbine blades (21).

10. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the heat chamber (9) is located downstream of the axial compressor (1) and upstream of the turbine blades (21).

11. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the working gas heating arrangement (27) is located next to and upstream of the turbine blades (14).

12. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the working gas cooling arrangement (28) is located in a region around the turbine shaft (15), downstream of the turbine blades (21) and upstream of the axial compressor (1).

13. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the working gas cooling arrangement (28) is attached to, or integrated in, the gas turbine housing (13).

14. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the closed-cycle gas turbine arrangement (7) and the working gas are configured for keeping the working gas constantly in gaseous mode through the complete flow cycle of the working gas.

15. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the rotor (14) has a hollow centre shaft (38) towards the side of the heat chamber (9) and at least one shaft inlet opening (49) for enabling the compressed working gas to enter into the hollow centre shaft (38) via the shaft inlet opening (49) and subsequently to flow through the hollow centre shaft (38) and into the heat chamber (13) via the inlet opening (11).

16. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims 5 to 15, wherein the closed-cycle gas turbine arrangement (7) comprises an outlet nozzle 37 arranged in connection with each outlet opening (12), and wherein each outlet nozzles (37) protrude from the heat chamber (9) towards the turbine blades (21).

17. The closed-cycle gas turbine arrangement (7) according to any of the preceding claims, wherein the turbine blades (21) are provided with a recess (50) facing towards the heat chamber (9), and wherein the outlet nozzles (37) protrude from the heat chamber (9) towards the turbine blades (21), such that the hot high- pressure working gas is configured to exit from the outlet nozzle within said recesses (50) of said turbine blades (21).

18. Method for operating a closed-cycle axial flow gas turbine arrangement (7) with working gas for converting thermal energy to kinetic energy, the closed-cycle gas turbine arrangement (7) comprising: a gas turbine housing (13); a rotor (14) carrying turbine blades (21) and being operably connected to a rotor output shaft (15); an axial compressor (1) comprising compressor blades (22) located on the rotor (14); a working gas heating arrangement (27), and a working gas cooling arrangement (28); the method comprising: heating the working gas in the working gas heating arrangement (27);guiding the heated working gas in a first mainly axial direction to the turbine blades (21) for rotating the rotor (14), cooling the working gas the in working gas cooling arrangement (28) and guiding the working gas radially inwards and back in a second mainly axial direction to the compressor blades (22) for compressing the working gas, and guiding the compressed working gas back to the working gas heating arrangement (27).

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