Heat Engine Systems

Abstract

Heat engine system (100, 1100). The heat engine system (100, 1100) comprises a compressor (300) having an inlet (302) and an outlet (304), a heat source (400) having an inlet (402) and an outlet (404), and a turbine (500) having an inlet (502) and an outlet (504). The compressor (300), the heat source (400), and the turbine (500) define a portion of a working fluid flow circuit (700). The heat engine system further comprises a housing (600) operable to be sealed to define a reservoir (602) in which the compressor (300), the heat source (400), the turbine (500), and the working fluid flow circuit (700) are located. The working fluid flow circuit (700) further comprises a compressor-to-heat source duct (800) extending between the compressor outlet (304) and the heat source inlet (402), a heat source-to-turbine duct (802) extending between the heat source outlet (404) and the turbine inlet (502), and a turbine-to-compressor duct (804) extending between the turbine outlet (504) and the compressor inlet (302). A bleed valve (806) is provided in flow communication with the compressor outlet (304) and operable to bleed working fluid into the reservoir (602). An intake valve (808) is provided in flow communication with the compressor inlet (302) and operable to allow working fluid to pass from the reservoir (602) to the compressor inlet (302).

Description

[Technical field]

[0001] The present disclosure relates to heat engine systems. [Background technology]

[0002] Heat engine systems are used to provide power in many different applications, one particular application being the powering of surface vessels, including submarines, which use nuclear reactors as a heat source to heat a working fluid that goes through a closed cycle with a compressor and a turbine to rotate a shaft, and which can then drive other machines (e.g., generators).

[0003] The heat source and main machinery (e.g. compressors and turbines) are housed within the vessel. Such systems have problems with maintaining a desired mass of working fluid in the cycle. For example, leakage may result in reduced power and, if the heat source is nuclear in nature, leakage may pose a contamination risk to the rest of the vessel. Furthermore, maintaining the mass of working fluid in a closed cycle may mean that the power output of the system can only vary within limited ranges.

[0004] Therefore, a heat engine system that offers improved power output control while preserving the volume of working fluid available for use within the cycle is highly desirable. Summary of the Invention

[0005] According to the present disclosure there is provided an apparatus, system and method as set out in the accompanying claims. Further features of the invention will be apparent from the dependent claims and the following description.

[0006] A heat engine system (100, 1100) may be provided comprising a compressor (300) having an inlet (302) and an outlet (304), a heat source (400) having an inlet (402) and an outlet (404), and a turbine (500) having an inlet (502) and an outlet (504). The compressor (300), the heat source (400), and the turbine (500) may define a portion of a working fluid flow circuit (700). The heat engine system may further comprise a housing (600) operable to be sealed to define a reservoir (602) within which the compressor (300), the heat source (400), the turbine (500), and the working fluid flow circuit (700) are located. The working fluid flow circuit (700) may further include a compressor-to-heat source duct (800) extending between the compressor outlet (304) and the heat source inlet (402), a heat source-to-turbine duct (802) extending between the heat source outlet (404) and the turbine inlet (502), and a turbine-to-compressor duct (804) extending between the turbine outlet (504) and the compressor inlet (302). A bleed valve (806) may be provided in flow communication with the compressor outlet (304) and operable to bleed the working fluid into the reservoir (602). An intake valve (808) may be provided in flow communication with the compressor inlet (302) and operable to allow the working fluid to pass from the reservoir (602) to the compressor inlet (302).

[0007] A bleed valve (806) may be provided in the compressor-to-heat source duct (800) and operable to bleed working fluid passing through the compressor-to-heat source duct (800) into the reservoir (602).

[0008] An intake valve (808) is provided in the turbine-compressor duct (804) and is operable to allow working fluid to pass from the reservoir (602) into the turbine-compressor duct (804) for delivery to the compressor inlet (302).

[0009] The heat engine system (1100) may further include a bleed valve (806), an intake valve (808), and a fluid flow merging conduit (810) defining a cavity (812) in flow communication with an opening (814) for fluid communication with the reservoir (602).

[0010] The heat engine system (100) may further include a control system. The control system may be operable to control the opening and closing of the bleed valve (806). The control system may be operable to control the opening and closing of the intake valve (808). The control system may be operable to control the bleed valve (806) and the intake valve (808) independently of one another.

[0011] The control system may be operable to control the bleed valve (806) and the intake valve (808) to open simultaneously with one another and / or to close simultaneously with one another.

[0012] The control system may be operable to control the bleed valve (806) and the intake valve (808) to vary the flow through the bleed valve (806) and the intake valve (808) relative to each other.

[0013] The control system may be operable to control the rate at which the bleed valve (806) and / or the intake valve (808) open and close.

[0014] The control system may be operable to vary the rate at which the bleed valve (806) and the intake valve (808) open and close relative to each other.

[0015] The control system may be operable to control the bleed valve (806) and the intake valve (808) such that when one of the bleed valve (806) and the intake valve (808) is open, the other is closed, such that when one of the bleed valve (806) and the intake valve (808) is fully open, the other is fully closed, and when one of the bleed valve (806) and the intake valve (808) is 50% open, the other is 50% open.

[0016] The compressor (300) and the turbine (500) may be rotatable about a common shaft (900) and may be coupled to rotate together about the common shaft (900).

[0017] The heat source (400) may include a nuclear reactor.

[0018] A vehicle may further be provided comprising a heat engine system (100, 1100) according to the present disclosure.

[0019] A method of operating a heat engine system (100, 1100) according to the present disclosure may also be provided, where the bleed valve (806) is controlled to bleed working fluid into the reservoir (602). The intake valve (808) may be controlled to allow working fluid to pass from the reservoir (602) to the compressor inlet (302). The bleed valve (806) and the intake valve (808) may be controlled to open and close independently of each other.

[0020] The bleed valve (806) and the intake valve (808) may be controlled to open simultaneously with one another and / or to close simultaneously with one another.

[0021] The bleed valve (806) and the intake valve (808) may be controlled such that when one of the bleed valve (806) and the intake valve (808) is open, the other is closed; when one of the bleed valve (806) and the intake valve (808) is fully open, the other is fully closed; and when one of the bleed valve (806) and the intake valve (808) is 50% open, the other is 50% open.

[0022] The bleed valve (806) and the intake valve (808) may be controlled to vary the flow through the bleed valve (806) and the intake valve (808) relative to each other.

[0023] The bleed valve (806) and / or the intake valve (808) may be controlled to open and close at different rates relative to one another.

[0024] Thus, there is provided a heat engine system (e.g., a heat source, such as a nuclear reactor, and a gas turbine) contained within a single (i.e., common) compartment (reservoir 602) having an atmosphere of the working fluid of working fluid flow circuit 700. In this manner, leakage from working fluid flow circuit 700 can be recirculated back into working fluid flow circuit 700 via compressor 300 and therefore is not lost to the environment outside housing 600.

[0025] Additionally, the system is configured to allow for power output control from the system by varying the mass of working fluid in the working fluid flow circuit 700 by flowing working fluid from the working fluid circuit 700 into the reservoir 602 and drawing working fluid from the reservoir into the working fluid circuit 700.

[0026] Examples of apparatus, systems and methods of operation of the present disclosure will now be described, by way of example only, with reference to the drawings in which: [Brief description of the drawings]

[0027] [Figure 1] 1 shows a schematic diagram of a vessel (in this case a submarine) that may include a heat engine system according to the present disclosure. [Diagram 2] By way of example, an example of a heat engine system of the present disclosure is shown located within the vessel shown in FIG. [Diagram 3] FIG. 1 shows a schematic diagram of a first example of a heat engine system of the present disclosure. [Figure 4] FIG. 2 shows a schematic diagram of a second example of a heat engine system of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present disclosure relates to a heat engine system 100, 1100. The present disclosure also relates to a vehicle 10 comprising a heat engine system 100, 1100 according to the present disclosure, and to a method of operation of a heat engine system 100, 1100 according to the present disclosure.

[0029] The vehicle 10 may be provided as a marine vessel, which may be provided as a submersible vehicle, such as a submarine 10 (shown in FIG. 1 ), comprising a thermal engine system 100, 1100 (e.g., shown in FIG. 2 ) according to the present disclosure housed therein.

[0030] Figure 3 shows a first example of a heat engine 100 according to the present disclosure. Figure 4 shows a second example of a heat engine 1100 according to the present disclosure.

[0031] Both examples may include a compressor 300 having an inlet 302 and an outlet 304. Additionally, a turbine 500 is provided having an inlet 502 and an outlet 504. The compressor 300 and the turbine 500 are rotatable about a common shaft 900 and are coupled to rotate together about the common shaft 900. The compressor 300 and the turbine 500 may form part of a gas turbine 350 assembly.

[0032] Both examples of heat engine systems 100, 1100 may further include a heat source 400 having an inlet 402 and an outlet 404. The heat source 400 may be any suitable source of heat. The heat source 400 may be a nuclear reactor. In the alternative, the heat source 400 may be chemically fueled, for example, using coal, diesel, or ethanol as a fuel source.

[0033] The compressor 300, the heat source 400, and the turbine 500 define a portion of a working fluid flow circuit 700 through which a working fluid (e.g., nitrogen) passes during operation. The working fluid flow circuit 700 may define a flow path that directs the working fluid through the compressor 300, the heat source 400, and the turbine 500 and back to the compressor 300. The working fluid flow circuit 700 may define a flow path to control the flow of the working fluid into the compressor 300, through the compressor 300, out of the compressor 300, then into the heat source 400, through the heat source 400, out of the heat source 400, then into the turbine 500, through the turbine 500, out of the turbine 500, and back to the compressor 300 to begin the cycle again.

[0034] The working fluid flow circuit 700 may further include a free spinning turbine 1200 through which the working fluid passes. The free spinning turbine 1200 may be used to drive a power offtake. As shown in relation to the first example of the heat engine system 100 of FIG. 3, the working fluid flow circuit 700 may further include a first bypass circuit 1204 that provides a bypass flow path past the free spinning turbine 1200. The first bypass 1204 may include a first bypass flow control valve 1234.

[0035] The working fluid flow circuit 700 may further include a heat exchanger 1202 through which the working fluid passes. The heat exchanger 1202 may be operable to remove heat from the working fluid. As shown in relation to the second example of the heat engine system 1100 of FIG. 4, the working fluid flow circuit 700 may further include a second bypass circuit 1206 providing a bypass flow path past the heat exchanger 1202. The second bypass 1206 may include a second bypass flow control valve 1236.

[0036] As shown in relation to the first example of the heat engine system 100 of Figure 3, the working fluid flow circuit 700 may further include a third bypass circuit 1208 providing a bypass flow path from the compressor 300 to a region downstream of the free spinning turbine 1200. The third bypass circuit 1208 may include a third bypass flow control valve 1238. The third bypass circuit 1208 may additionally or alternatively include a filter 1240 configured to filter particulates and / or chemicals. The third bypass flow control valve 1238 may be provided in series or parallel with the filter 1240.

[0037] The working fluid flow circuit 700 may further include a fourth bypass circuit 1210 that provides a bypass flow path between the heat source inlet 402 and the heat source outlet 404. The fourth bypass 1210 may include a fourth flow control valve 1250.

[0038] The heat engine system may further comprise a housing 600 operable to be sealed to define a reservoir 602 within which the compressor 300, the heat source 400, the turbine 500, and the working fluid flow circuit 700 are located. That is, the housing 600 defines (e.g. determines the limits or boundaries of) the reservoir 602 within which the compressor 300, the heat source 400, the turbine 500, and the working fluid flow circuit 700 are located. The housing 600 may be a separate (i.e. dedicated) structure or may comprise a combination of walls that also form part of a surrounding structure. For example, in the case of a marine vessel, the walls defining the housing 600 may comprise bulkheads and hull regions.

[0039] Housing 600 is sealable and configured to contain a working fluid (e.g., nitrogen). That is, housing 600 may be configured to prevent fluid exchange across a boundary defined by housing 600. In other words, housing 600 may be configured to prevent fluid loss from reservoir 602 (i.e., from inside the boundary defined by housing 600 to outside the boundary defined by housing 600) and to prevent fluid ingress into reservoir 602 (i.e., from outside the boundary defined by housing 600 to inside the boundary defined by housing 600).

[0040] 3 and 4, the working fluid flow circuit 700 may include a compressor-to-heat source duct 800 extending between the compressor outlet 304 and the heat source inlet 402 for passing the working fluid between the compressor outlet 304 and the heat source inlet 402. The working fluid flow circuit 700 may include a heat source-to-turbine duct 802 extending between the heat source outlet 404 and the turbine inlet 502 for passing the working fluid between the heat source outlet 404 and the turbine inlet 502. The working fluid flow circuit 700 may include a turbine-to-compressor duct 804 extending between the turbine outlet 504 and the compressor inlet 302 for passing the working fluid between the turbine outlet 504 and the compressor inlet 302.

[0041] A bleed valve 806 may be provided in flow communication with the compressor outlet 304 and operable to bleed working fluid into the reservoir 602. An intake valve 808 may be provided in flow communication with the compressor inlet 302 and operable to allow working fluid to pass from the reservoir 602 to the compressor inlet 302.

[0042] A bleed valve 806 may be provided in the compressor-to-heat source duct 800 and operable to bleed working fluid passing through the compressor-to-heat source duct 800 into the reservoir 602, the bleed valve 806 having a vent 818 opening into the reservoir 602 and / or in fluid communication with the vent 818. An intake valve 808 may be provided in the turbine-to-compressor duct 804 and operable to allow working fluid to pass from the reservoir 602 into the turbine-to-compressor duct 804 for delivery to the compressor inlet 302, the intake valve 808 having an intake 820 opening into the reservoir 602.

[0043] 4, for a second example of a heat engine 1100, the heat engine system 1100 may further include a bleed valve 806, an intake valve 808, and a fluid flow conduit 810 defining a cavity (e.g., volume and / or chamber) 812 in flow communication with an opening 814 for fluid communication with the reservoir 602. The opening 814 may be at the end of a pipe 816, and the fluid flow may be from the fluid flow conduit 810 into the reservoir 602 or from the reservoir 602 into the fluid flow conduit 810.

[0044] The fluid flow junction conduit 810 may include a filter 830. The filter 830 may be operable to prevent the passage of particulates and / or chemicals from and / or into the working fluid circuit 700.

[0045] The heat engine system 100, 1100 may further include a control system (i.e., controller) (not shown) operable to control the opening and closing of the bleed valve 806. The control system (not shown) may be operable to control the opening and closing of the intake valve 808. The control system may be operable to control the bleed valve 806 and the intake valve 808 independently of one another.

[0046] A control system (not shown) may be operable to control the bleed valve 806 and the intake valve 808 to open simultaneously with one another. A control system (not shown) may be operable to control the bleed valve 806 and the intake valve 808 to close simultaneously with one another.

[0047] A control system (not shown) may be operable to control the bleed valve 806 and the intake valve 808 to vary the flow through them relative to one another. That is, the control system may be operable to control the bleed valve 806 and the intake valve 808 to vary the flow through the bleed valve 806 relative to the flow through the intake valve 808 and vary the flow through the intake valve 808 relative to the flow through the bleed valve 806.

[0048] The control system may be operable to control the rate at which the bleed valve 806 and / or the intake valve 808 open and close.

[0049] The control system may be operable to vary the rate at which the bleed valve 806 and the intake valve 808 open and close relative to one another.

[0050] The control system may be operable to control the bleed valve 806 and the intake valve 808 such that when one of the bleed valve 806 and the intake valve 808 is open the other is closed, such that when the flow rate through one of the bleed valve 806 and the intake valve 808 increases the flow rate through the other of the bleed valve 806 and the intake valve 808. In one example, when one of the bleed valve 806 and the intake valve 808 is fully open the other is fully closed and when one of the bleed valve 806 and the intake valve 808 is 50% open the other is 50% open.

[0051] In operation, the bleed valves 806 and intake valves 808 of the heat engine systems 100, 1100 of the present disclosure are controlled to open and close, for example under the control of a control system (not shown). The relative timing of when one of the bleed valves 806 and intake valves 808 is closed or open relative to the other bleed valves 806 and intake valves 808 may be controlled according to the required power output of the heat engine system 100, 1100 (i.e., the power demand for the heat engine system). That is, the relative timing of when one of the bleed valves 806 and intake valves 808 is closed or open relative to the other bleed valves 806 and intake valves 808 may be controlled to regulate the mass of working fluid passing through the flow circuit 700.

[0052] The basic operation of the system 100, 1100 is described in Table 1 below. [Table 1]

[0053] Thus, the bleed valve 806 may be controlled to open to bleed a portion of the working fluid flowing through the flow circuit 700 into the reservoir 602, and the intake valve 808 is controlled to open to allow the working fluid to pass from the reservoir 602 to the compressor inlet 302 and into the flow circuit 700.

[0054] When both the bleed valve 806 and the intake valve 808 are open, the net flow of working fluid from the reservoir 602 into the flow circuit 700 can be positive (i.e., increasing the amount of working fluid in the working fluid flow circuit 700) or negative (i.e., decreasing the amount of working fluid in the working fluid flow circuit 700). When both the bleed valve 806 and the intake valve 808 are closed, there is no controlled flow between the flow circuit 700 and the reservoir 602. That is, when both the bleed valve 806 and the intake valve 808 are closed, there is no flow from the flow circuit 700 into the reservoir 602, except for leakage from the flow circuit 700.

[0055] The bleed valve 806 and the intake valve 808 may be controlled to open and close independently of one another, and thus the bleed valve 806 and the intake valve 808 may be at least partially open (i.e., configured to allow working fluid to flow) at the same or different times.

[0056] The bleed valve 806 and the intake valve 808 may be controlled to open simultaneously with one another and / or to close simultaneously with one another.

[0057] Alternatively or additionally, the bleed valve 806 and the intake valve 808 may be controlled such that when one of the bleed valve 806 and the intake valve 808 opens to allow working fluid to flow therethrough, the other closes, such that when the flow rate through one of the bleed valve 806 and the intake valve 808 increases, the flow rate through the other of the bleed valve 806 and the intake valve 808 decreases.

[0058] Alternatively or additionally, the bleed valve 806 and the intake valve 808 may be controlled such that when one of the bleed valve 806 and the intake valve 808 is fully open, the other is fully closed.

[0059] Alternatively or additionally, the bleed valve 806 and the intake valve 808 may be controlled such that when one of the bleed valve 806 and the intake valve 808 is 50% open, the other is 50% open.

[0060] The bleed valve 806 and the intake valve 808 may be controlled to vary the flow through the bleed valve 806 and the intake valve 808 relative to each other.

[0061] The bleed valve 806 and / or the intake valve 808 may be controlled to open and close at different rates relative to one another.

[0062] The bleed valve 806 and / or the intake valve 808 may have the same flow area capacity or may have different flow area capacities. That is, when fully open, the bleed valve 806 (and vent 818) and the intake valve 808 (and intake 820) may have the same flow area so that the maximum flow rate through both is the same. That is, when fully open, the bleed valve 806 and vent 818 may allow the same maximum flow rate as the intake valve 808 and intake 820.

[0063] During operation, the reservoir 602 delimited by the housing 600 provides storage of working fluid (e.g., nitrogen gas) at the same pressure as the turbine inlet 502. The pressure in the reservoir 602 may be controlled to be at ambient temperature. The pressure in the working fluid flow circuit 700 is greater than ambient pressure. This ensures that leakage from the compressed working fluid flow circuit 700 is not a concern since any leaked working fluid can be directed into the compressor 300 at the compressor inlet 302 while keeping the pressure in the reservoir 602 low.

[0064] As described, using the housing 600 as a pressure vessel such that the working fluid is exhausted from the high pressure working fluid flow circuit 700 into the reservoir 602 allows for a reduction in mass flow rate through the turbine 500, and therefore a reduction in output power level while maintaining a constant pressure ratio. This allows for achieving turbine efficiencies closer to design at part load.

[0065] Also, by maintaining the pressure within reservoir 602 at approximately atmospheric pressure, housing 600 does not need to be a heavy-duty (and therefore expensive, heavy, and large) pressure vessel, and thus housing 600 may be a relatively lightweight structure.

[0066] Changing the flow rates through the bleed valve 806 and the intake valve 808 changes the balance of working fluid lost from the reservoir 602 and gas working fluid gained in the reservoir 602, resulting in either a net loss of gas or a net gain of working fluid from the reservoir 602 to the working fluid flow circuit 700 until the system achieves steady state.

[0067] The relatively large reservoir 602 volume required to contain the reactor, compressor, turbine, and other equipment means that working fluid can be pumped into or withdrawn from the reservoir with small pressure changes within the reservoir 602.

[0068] The use of nitrogen as the working fluid ensures that large power changes can be achieved by simply venting the working fluid flow circuit 700 into the reservoir 602 .

[0069] In the example where both the bleed valve 806 and the intake valve 808 are opened simultaneously (thereby providing flow therethrough), a proportional power control is introduced depending on the valve open / close position of the bleed valve 806 and the intake valve 808. This proportional power control simplifies the turbine power output control system since only the valve position needs to be controlled instead of the valve position and the valve open duration. This allows for simplified droop control required for stable division of the load among multiple generators.

[0070] It is important to include droop for stable power control when feeding the grid, especially when there are multiple generators. Droop in a conventional turbine is controlled by a governor and is the proportional response of the turbine power to the error from a reference speed, as shown by equation [1]: Droop %=(No load speed - Full load speed) / (No load speed)

number

[0071] As mentioned above, the opening of the bleed valve 806 and the intake valve 808 may be considered in conjunction. In such an operating mode, the mass of working fluid in the working fluid flow circuit 700 becomes a function of the rate of bleed off from and re-entry into the working fluid flow circuit 700. Thus, the power level becomes proportional to the combined open and closed positions of the bleed valve 806 and the intake valve 808. Droop control is therefore easy to implement by placing the valve position relative to the speed error of the turbine relative to the reference speed. In this manner, part-load efficiency can be maintained since a significant portion of the power reduction is due to the lowering of the mass in the working fluid flow circuit 700, while the flow bypassing the turbine contributes a small portion of the power change increment in the working fluid flow circuit 700. Furthermore, the flow bypassing the turbine can be adjusted by selecting the valve opening and closing profile to ensure increased damping during power control and achieve a desired level of system stability.

[0072] The disclosed heat engine system 100, 1100 configuration places the heat source 400 (e.g., nuclear reactor) and other major machinery in a single compartment. Placing all heat engine components, including the flow paths of the working fluid flow circuit 700, in a single reservoir 602 allows the reservoir 602 to be filled with the same fluid as the working fluid flow circuit 700. The net result is that leakage from the working fluid flow circuit 700 will enter the reactor reservoir 602, where the pressure is near atmospheric with limited pressure drive for further leakage to the environment.

[0073] This design approach largely eliminates the drive mechanism for transporting undesirable characteristics of the heat source (e.g., chemicals or radiation) outside the plant boundary defined by the housing 600. More importantly, the compressor inlet also operates at the same pressure as the reservoir 602, allowing any gas leakage from the pressurized section of the working fluid flow circuit 700 to be effectively drawn back into the working fluid flow circuit 700 at the compressor inlet.

[0074] Such a system having a closed cycle gas cooled reactor offers additional advantages with regard to power control.

[0075] Furthermore, because the volume of gas in reservoir 602 is large, the pressure in reservoir 602 does not change significantly after pressurization and depressurization of working fluid flow circuit 700. This allows a simple valve to act as a bleed into reservoir 602 without the need to include a compressor to store the removed working fluid flow circuit 700 gas in a high pressure cylinder. As a result, rapid power changes can be achieved using the control of the present invention, eliminating the need for additional complexity in the plant control design by maintaining part load design point efficiency.

[0076] The disclosed apparatus, systems, and methods allow for rapid rates of change of power output because the transfer of working fluid is between adjacent volumes (i.e., working fluid flow circuit 700 and reservoir 602) operating at similar pressures. Therefore, additional control systems and working fluid storage systems are not required for rapid power transients.

[0077] Attention is directed to all documents and literature related to this application that are filed contemporaneously with or prior to this application and that are open to public inspection herewith, and the contents of all such documents and literature are incorporated herein by reference.

[0078] All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive.

[0079] Each feature disclosed in this specification (including any accompanying claims, abstract, and drawings), unless expressly stated otherwise, may be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless expressly stated otherwise, each feature disclosed is only one example of a generic series of equivalent or similar features.

[0080] The invention is not limited to the details of the embodiment or embodiments described above. The invention extends to any novel one or any novel combination of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one or any novel combination of the steps of any method or process so disclosed.

Claims

1. a compressor having an inlet and an outlet; a heat source having an inlet and an outlet; a turbine having an inlet and an outlet; A heat engine system comprising: the compressor, the heat source, and the turbine define a portion of a working fluid flow circuit; the heat engine system further comprising a housing operable to be sealed to define a reservoir within which the compressor, the heat source, the turbine, and the working fluid flow circuit are located; The working fluid flow circuit includes: a compressor-to-heat source duct extending between an outlet of the compressor and an inlet of the heat source; a heat source-to-turbine duct extending between an outlet of the heat source and an inlet of the turbine; a turbine-compressor duct extending between an outlet of the turbine and an inlet of the compressor; Further comprising: a bleed valve in flow communication with the compressor outlet and operable to bleed working fluid into the reservoir; A heat engine system comprising: an intake valve in flow communication with the compressor inlet and operable to allow working fluid to pass from the reservoir to the compressor inlet.

2. the bleed valve is provided in the compressor-to-heat source duct and is operable to bleed the working fluid passing through the compressor-to-heat source duct into the reservoir; the intake valve is disposed in the turbine-compressor duct and is operable to allow working fluid to pass from the reservoir into the turbine-compressor duct for delivery to an inlet of the compressor; 10. The heat engine system of claim 1.

3. The heat engine system of claim 1 or 2, further comprising a fluid flow merging conduit defining a cavity in flow communication with the bleed valve, the intake valve, and an opening for fluid communication with the reservoir.

4. Further comprising a control system; the control system is operable to control the opening and closing of the bleed valve; the control system is operable to control the opening and closing of the intake valve; the control system is operable to control the bleed valve and the intake valve independently of one another. A heat engine system according to any one of claims 1 to 3.

5. The control system controls the bleed valve and the intake valve. open simultaneously with each other, and / or Close each other at the same time, 5. The heat engine system of claim 4, operable to control the

6. 6. A heat engine system as claimed in claim 5 when dependent on claim 4, wherein the control system is operable to control the bleed valve and the intake valve to vary the flow through the bleed valve and the intake valve relative to each other.

7. 7. A heat engine system as claimed in any one of claims 4, 5 or 6, wherein the control system is operable to control the rate at which the bleed valves and / or the intake valves open and close.

8. The heat engine system of claim 7 , wherein the control system is operable to vary the rate at which the bleed valve and the intake valve open and close relative to each other.

9. The control system is operable to control the bleed valve and the intake valve such that when one of the bleed valve and the intake valve is open, the other is closed, whereby a. when one of the bleed valve and the intake valve is fully open, the other is fully closed; b. When one of the bleed valve and the intake valve is 50% open, the other is 50% open. A heat engine system according to any one of claims 4 to 8.

10. A heat engine system according to any preceding claim, wherein the compressor and the turbine are rotatable about a common axis and are coupled to rotate together about the common axis.

11. A heat engine system according to any preceding claim, wherein the heat source comprises a nuclear reactor.

12. A vehicle comprising a heat engine system according to any one of the preceding claims.

13. A method for operating a heat engine system according to any one of claims 1 to 11, comprising the steps of: the bleed valve is controlled to bleed hydraulic fluid into the reservoir; the intake valve is controlled to allow working fluid to pass from the reservoir to an inlet of the compressor; A method of operating a heat engine system, wherein the bleed valve and the intake valve are controlled to open and close independently of each other.

14. The bleed valve and the intake valve are open simultaneously with each other, and / or Close each other at the same time, The method of claim 13, wherein the heat engine system is controlled as follows:

15. the bleed valve and the intake valve are controlled such that when one of the bleed valve and the intake valve is opened, the other is closed; a. when one of the bleed valve and the intake valve is fully open, the other is fully closed; b. When one of the bleed valve and the intake valve is 50% open, the other is 50% open; 14. A method of operating a heat engine system according to claim 13.

16. A method of operating a heat engine system according to any one of claims 13 to 15, wherein the bleed valve and the intake valve are controlled to vary the flows through the bleed valve and the intake valve relative to each other.

17. A method of operating a heat engine system according to any one of claims 13 to 16, wherein the bleed valves and / or the intake valves are controlled to open and close at different rates relative to each other.

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