TURBOMACHINE INNER HOUSING

Description

[0001] The invention relates to an arrangement with a turbomachine inner housing for a radial turbomachine, wherein the turbomachine inner housing has a parting joint along a longitudinal axis, in particular a rotor longitudinal axis, such that the turbomachine inner housing can be divided into a lower part and an upper part, wherein the turbomachine inner housing is designed for a radial turbomachine comprising at least two stages, wherein the turbomachine inner housing has a return stage between each two stages, wherein the lower part and / or the upper part is formed in one piece, at least in sections, spanning at least two stages.

[0002] Radial turbomachines of the type mentioned at the beginning with generic turbomachine inner casings are already known from the documents WO2016026825-A1, WO2010034602-A1, WO2007137959-A1 and EP1860326-A1.

[0003] Further disclosures relating to turbomachinery are contained in the documents US 2017826A, JP S5417101U and US 1050419A.

[0004] From GB 747 359 A a multi-stage centrifugal pump or a multi-stage compressor is known which has an outer casing and an inner casing made of stainless steel.

[0005] DE 10 2013 225065 A1 discloses a pump housing made of plastic.

[0006] A turbomachine inner casing or an inner casing of a turbomachine, in particular a radial turbomachine, is always enclosed by an outer casing. The outer casing is essentially sealed so that no significant quantities of process fluid can escape from the outer casing. If shaft passages are provided in the outer casing, these are sealed by a shaft seal. Technically necessary leaks can occur at these points, but these are undesirable. In principle, a drive for a compressor or pump, for example, can also be provided within the outer casing, thus eliminating the need for a shaft passage. In this case, the corresponding sealing of the outer casing is truly hermetic.

[0007] A corresponding turbomachine within the meaning of the invention serves to transfer technical work from or to the process fluid by means of a rotor that extends along a rotational axis. In the axial course of the turbomachine inner casing, the pressure of the process fluid is either built up or reduced, so that the significant pressure difference in the turbomachine or across the turbomachine occurs between the axial ends of the turbomachine inner casing. In the simplest case, a process fluid flows through the turbomachine, starting from an inflow to an outflow. In principle, it is also possible for partial flows to be fed in or branched off in between. In a radial turbomachine, the flow is deflected from axial to radial or vice versa in each individual impeller.

[0008] A multi-stage design, as defined in this document, means a construction with multiple impellers (one impeller corresponds to one stage in the terminology of this document), which must be diverted from a radially outward flow direction to a radially inward flow direction. In a compressor, the process fluid leaving the impeller flowing radially outward must have its flow direction reversed by 180 degrees radially inward and be fed essentially axially back to the downstream impeller. For this purpose, radial turbomachines have so-called recirculation stages. Such recirculation stages are usually bladed annular channels that have a diffuser with a radially outward flow direction and perform a 180-degree reversal of the flow direction with a correspondingly designed annular channel. The process fluid is then guided radially inward.The diffuser and / or the radially inward return passage typically feature guide vanes that circumferentially subdivide the already relatively complexly shaped annular channel into individual flow channels. For optimal aerodynamics, it is also desirable to design the corresponding guide vanes three-dimensionally, so the geometric design of these components or return stages is extremely complex. Three-dimensional shaping of the return blading is currently technically difficult or impossible to achieve using conventional machining techniques. Such return stages or turbomachinery inner casings, which essentially consist of these return stages, are typically divided into an upper and a lower section along a parting line parallel to the longitudinal axis, particularly for assembly purposes.Furthermore, conventional manufacturing of this highly complex geometry requires an axial division of each individual recirculation stage into at least two axial sections, which together form the described annular channel. Thus, conventional turbomachinery inner casings consist of two axial stacks of individual recirculation stage components, which together form an upper and a lower section to form a complete turbomachinery inner casing. This modular design is very complex due to the large number of individual parts and the associated numerous fastening arrangements and sealing requirements. Furthermore, the various individual parts must not only be sealed to one another but also aligned accordingly. Manufacturing the sealing surfaces and the many required centering devices and fastenings, in addition to the complex manufacturing of the annular recirculation stage flow channels, is very complex and expensive.

[0009] Based on the disadvantages described above, the invention aims to at least partially eliminate these problems. To achieve the inventive objective, an arrangement with a turbomachine inner casing of the type defined above, with the additional features of the characterizing part of the independent claim, is proposed.

[0010] Terms such as axial, radial, circumferential direction, unless otherwise stated, refer to a longitudinal axis of the turbomachine inner casing, which is at least parallel to a rotor longitudinal axis of a corresponding radial turbomachine.

[0011] Unless otherwise stated, the descriptions in this document refer to a turbomachine equipped according to the invention configured as a compressor. Alternatively, the turbomachine equipped according to the invention may also be configured as an expander, without this being expressly stated. Based on their specialist knowledge, the person skilled in the art will be able to apply the present explanations of the invention, mutatis mutandis, to an expander as well.

[0012] The term "one-piece" is understood by the invention to mean a component that is not designed to be divisible without destruction, so that the component is either formed from a homogeneous piece of material or is at least materially or at least form-fittingly formed as a unit in such a way that it cannot be divided again without destruction.

[0013] The one-piece construction of the upper part and / or the lower part over at least one section of the turbomachine inner casing spanning two stages results in excellent stiffening of this structure, because guide vanes in the annular chambers or flow channels of the return stages of the turbomachine inner casing, in particular, ensure a highly resilient assembly. According to the invention, the return stages are bladed or have guide vanes.

[0014] Each integrally formed return stage has guide vanes at least in the radially inward-leading section (flow direction) and preferably in the radially outward-leading section (flow direction).

[0015] Accordingly, not only is an aerodynamically particularly advantageous and efficient design ensured, but also a particularly high rigidity of this one-piece section.

[0016] According to the invention, the turbomachine inner casing consists of up to 50 wt.% metal. Particularly preferably, the turbomachine inner casing consists of no more than 30 wt.% metal.

[0017] According to the invention, the turbomachinery inner casing consists of at least 50% plastic by weight (all percentages in this document are based on weight unless otherwise stated). Compared to conventional designs of turbomachinery inner casings, the design according to the invention allows this component to be manufactured largely from plastic because the one-piece construction ensures mechanical rigidity that would otherwise only be guaranteed by a metallic construction of this component.

[0018] To ensure that the turbomachinery's inner casing is sufficiently wear-resistant, it is advisable for at least some of the surface exposed to a process fluid during operation to be provided with a coating that is more wear-resistant than the base material coated with this layer. Such a coating can particularly advantageously consist at least partially of a metal or be provided from corresponding metal pieces or by means of metal inlays.

[0019] According to the invention, the turbomachine inner casing has at least two recirculation stages, wherein the turbomachine inner casing has an inner surface defining the interior of the turbomachine inner casing and an outer surface, wherein the outer surface has at least one radially inwardly extending recess axially between two recirculation stages. Between the annular flow channels of the recirculation stages, which are U-shaped in longitudinal section, there is usually a part of the impeller in a radial turbomachine, which extends axially, sucking in the process fluid and deflecting it radially.In this area in particular, the axial region located further radially outward is essentially aerodynamically functionless because the annular channel of the recirculation stages extends axially from the outflow from the impeller to the axial inflow to the following impeller (this flow direction specification applies to the compressor; for expanders, the flow direction is reversed; in the following, the compressor will always be used as an example for such flow direction specifications without further reference). Accordingly, it is sensible to provide the axial region between two recirculation stages with a recess or cutout that extends radially inward. Depending on their size, such recesses significantly reduce the dead weight of the turbomachinery inner casing and can be extended radially inward to approximately the outer diameter of the impeller.Particularly preferably, the radially inner base of the corresponding recesses is located in the region of the impeller outer diameter of the adjacent stages plus / minus 20% of the impeller outer diameter. Particularly preferably, such a recess or recesses extend.

[0020] Type has a cross-sectional area proportion of the turbomachine inner casing of at least 35%. Here, 100% means an assumed cross-sectional area that forms the average between the two cross-sectional areas actually present in the area of ​​the axially adjacent impellers of the turbomachine inner casing (cross-sectional area is arranged perpendicular to the longitudinal axis). In a cylindrical turbomachine inner casing, the cross-sectional area proportion of 100% is the constant cross-sectional area. A key advantage of such recesses is that external pressure does not have an axial length-changing effect, at least in the area of ​​the recess. In fact, without these recesses, depending on the rigidity of the turbomachine inner casing and the pressure between the inner casing and the outer casing, significant deformation of the upper and lower sections of the turbomachine inner casing can occur.Accordingly, such recesses reduce the rigidity requirements of the turbomachinery inner casing.

[0021] The advantages of the invention become particularly clear in an arrangement comprising a turbomachine inner housing of the type according to the invention or a corresponding development and a turbomachine outer housing, wherein the arrangement has an axial low-pressure side and an axial high-pressure side, wherein the arrangement has a seal that extends in the circumferential direction and is arranged in a space between the high-pressure side and the low-pressure side, such that the space is divided into a high-pressure part and a low-pressure part. According to the invention, the arrangement is designed such that the high-pressure part is at the ultimate pressure of the turbomachine during operation and the low-pressure part is at the intake pressure during operation.In this case, it is particularly expedient if the recesses between the two adjacent return stages are arranged in the region of the high-pressure part, so that on the one hand the high pressure is at least partially compensated axially and on the other hand the resulting force distribution on the outer surface of the turbomachine inner casing ensures a particularly uniform pressing of the lower part against the upper part of the turbomachine inner casing during operation and accordingly fewer precautions are required for the purpose of fastening and sealing between the two components.

[0022] Particularly expediently, the turbomachinery outer casing of this arrangement is designed in a pot-shaped configuration, with a parting joint extending transversely to the longitudinal axis. It is advantageous if the parting joint separates a cover from a pot of the turbomachinery outer casing. A cover is defined by those skilled in the art as an axial closure of the pot that does not serve as a casing.

[0023] It is particularly expedient for at least the section of the turbomachine inner casing, which is formed in one piece across at least two stages, to be produced by means of an additive manufacturing process (generative manufacturing process or additive manufacturing). Corresponding additive manufacturing processes are already known from WO2016 / 198210, WO2017 / 060036, WO2017 / 102286, WO2017 / 121539, WO2017 / 137376, WO2017 / 37262, WO2017 / 167615, WO2017 / 182220, WO2017 / 182221, WO2017 / 194274, WO2017 / 194451, WO2015 / 144401, WO2017 / 045823, WO2017 / 063861, WO2017 / 093461, WO2017 / 133812, WO2017 / 174234, WO2017 / 174233, WO2017 / 194387, WO2016 / 078800, WO2016 / 113107, WO2016 / 188696 and WO2017 / 157620. In principle, all additive manufacturing processes can be used for the inventive design: e.g.Selective laser melting (SLM), selective laser sintering (SLS), selective heat sintering (SHS), binder jetting (solidifying powder material using a binder), electron beam melting (EBM), fused deposition modeling (FDM or fused filament fabrication (FFF)), cladding, wax deposition modeling (WDM), contour crafting, metal powder deposition (MPA), cold gas spraying and electron beam melting (EBW), stereolithography (SLA) + micro-SLA, processes that use digital light processing (DLP) for exposure and liquid composite molding (LCM), laminated object modeling (LOM), 3D screen printing of metals and light-controlled electrophoretic deposition.

[0024] An advantageous development of the invention provides that the division of the turbomachine inner housing into a preferably one-piece lower part and a preferably one-piece upper part with the exception of a suction insert on the low-pressure side, which is preferably undivided in the circumferential direction and is joined to the lower part LPC and the upper part UPC at a substantially axial division in a parting line SPL to form the turbomachine inner housing TMI. A seal is preferably located on the suction insert between the turbomachine inner housing and the turbomachine outer housing, separating the high-pressure side from the low-pressure side. The suction insert is advantageously made of metal in order to be able to absorb the mechanical load from the pressure difference. Selective laser melting or electronic beam melting is particularly expedient here.In this case, it is particularly useful if not only the aforementioned section, but at least an entire upper part or an entire lower part, or both the upper and lower parts, are formed in one piece. Accordingly, the application of an additive manufacturing process of the aforementioned type is appropriate for the entire turbomachinery inner casing.

[0025] The invention is described in more detail below using a specific exemplary embodiment with reference to a drawing. Figure 1 shows a schematic longitudinal section through an arrangement or a radial turbomachine with a turbomachine inner casing according to the invention.

[0026] Figure 1 shows an arrangement ARG or a radial turbomachine RTM with a turbomachine inner casing TMI according to the invention. The turbomachine inner casing TMI is surrounded by a turbomachine outer casing TMO, through which a process gas PFL flows from an inflow IMF to an outflow EXT. In the specific embodiment of a radial turbocompressor, the process fluid PFL is subjected to a higher pressure as it flows through the turbomachine inner casing TMI by means of impellers IMP, which are part of a rotor ROT rotating about a longitudinal axis X or rotor axis RX. Here, the turbomachine inner casing TMI is a static, particularly aerodynamically acting component, and the rotor ROT with the impellers IMP introduces technical work from an external drive (not shown in detail) into the process fluid PFL.For the purpose of connecting a drive, the left-hand shaft end, as well as the right-hand shaft end of the rotor, extend axially through a passage opening in the outer casing TMO. The corresponding shaft passages are sealed against the pressure difference between the process fluid inside the outer casing TMO and the ambient air by means of a shaft seal (not described in detail).

[0027] The turbomachine inner casing TMI receives the process fluid PFL in the turbomachine outer casing TMO in the area of ​​an intermediate space RBT. The intermediate space RBT is divided into a high-pressure side HPS and a low-pressure side LPS by means of a seal STS between the turbomachine inner casing TMI and the turbomachine outer casing TMO. The seal STS runs in the circumferential direction (to the longitudinal axis X or rotor axis RX) and separates an axial high-pressure section HPC of the intermediate space RBT from an axial low-pressure section LPC. The inflow IMF of the turbomachine outer casing TMO flows into the low-pressure section LPC, and the outflow EXT is in fluid communication with the high-pressure section HPC. The seal STS is designed to fit axially in such a way that, during operation, the higher pressure in the high-pressure section HPC pushes the turbomachine inner casing TMI towards the low-pressure section LPC, thus ensuring the tightness of the seal STS.

[0028] The radial turbomachine RTM shown has six impellers and thus, in the inventive sense, six stages STG or compression stages. Between each two stages, a so-called recirculation stage BFC is formed in the turbomachine inner casing TMI. The recirculation stage receives the radially outward-flowing process fluid PFL from the upstream impeller IMP. In the section of the recirculation stage BFC, which initially acts as a diffuser, the process fluid is decelerated and largely freed of unwanted swirl components by the guide vanes provided there. In the downstream section of the annular channel of the recirculation stage BFC, the process fluid is deflected 180° radially inward and then guided further radially inward through a guide-bladed section. Downstream, a 90-degree deflection in the axial direction takes place to the next upstream impeller IMP.In the specific embodiment, the turbomachine inner casing TMI is formed as a combination of a one-piece lower part LPC and a one-piece upper part UPC with a parting line along a longitudinal axis X. According to the invention, the upper part UPC and the lower part LPC of the turbomachine inner casing can also be formed as a single piece only in sections, spanning at least two stages, and this can only be done for the lower part LPC or the upper part UPC. No further illustration is required for this.

[0029] In the specific embodiment, the turbomachinery inner casing TMI is divided into a lower part LPC and an upper part UPC, with the exception of a suction insert SES, which is joined to the lower part LPC and the upper part UPC in a circumferentially undivided manner by means of a substantially axial division in a parting line SPL to form the turbomachinery inner casing TMI. The seal STS, which separates the high-pressure side HPS from the low-pressure side LPS, rests against the suction insert SES. The suction insert SES is advantageously made of metal in order to absorb the mechanical load resulting from the pressure difference.

[0030] The turbomachinery inner casing TMI consists of up to 50 wt.% metal, preferably up to 30 wt.%. The turbomachinery inner casing is made of 50 wt.% or more plastic. In some areas, the turbomachinery inner casing is coated with an SCC coating on surfaces exposed to the process fluid PFL during operation. This coating consists at least partially of metal.

[0031] The turbomachine inner casing defines an inner surface ISC and an outer surface OSC. Axially between two return stages BFC, the outer surface OSC is provided with a radially inwardly extending recess RRZ. This recess RRZ reaches a cross-sectional area proportion of the turbomachine inner casing TMI of at least 35%. Accordingly, during operation, the ultimate pressure of the high-pressure side HPS also acts in the area of ​​these recesses RRZ and ensures, on the one hand, a lower axial compressive force on the turbomachine inner casing TMI and, on the other hand, only minimal resulting deformation and uniform contact of a sealing surface between the upper part UPC and the lower part LPC. Axial stiffening of the upper part UPC and the lower part LPC is achieved by means of ribs in the recesses RRZ, which extend essentially flat in the axial-radial direction.

[0032] The operating pressure in the individual recesses in the area of ​​the outer surface (OSC) is generally lower than the ultimate pressure on the high-pressure side (HPS). Due to the delicate contour of the outer surface (OSC), this operating pressure compresses the joint (TF) between the upper part (UPC) and the lower part (LPC), preventing internal leaks. In a conventional metal housing, the joint areas are thick-walled with manufacturing-related gaps that lead to internal leaks.

[0033] The turbomachinery outer casing TMO is designed as a pot-shaped structure, with a parting joint OCS on both sides perpendicular to the longitudinal axis X. Axially on both sides, a cover COV forms the axial closure of a pot BRL of the turbomachinery outer casing TMO. The cover does not serve as a casing and merely forms the axial closure.

[0034] The turbomachinery inner casing TMI was produced by means of an additive manufacturing process, at least in the area that is formed in one piece across at least two stages.

Claims

1. Arrangement (ARG) comprising a turbomachine inner housing (TMI), for a radial turbomachine (RTM), wherein the turbomachine inner housing (TMI) has a dividing line (TF) along a longitudinal axis (X), in particular a rotor longitudinal axis (RX), such that the turbomachine inner housing (TMI) can be divided into a lower part (LPC) and an upper part (UPC), wherein the turbomachine inner housing (TMI) is designed for a radial turbomachine (RTM) comprising at least two stages (STG), wherein the turbomachine inner housing (TMI) has a return stage (BFC) between each two stages (STG), wherein the return stage (BFC) is designed in such a way, that within the turbomachine inner housing (TMI) in the downstream section of the annular channel of the return stage (BFC), the process fluid is deflected by 180° radially inwards and then guided further radially inwards through a guide-bladed section, whereby a 90° deflection in the downstream axial direction to the next upstream impeller (IMP) takes place, the lower part (LPC) and / or the upper part (UPC) are / is formed in one piece, spanning at least two stages (STG) at least in some sections, wherein the turbomachine inner housing (TMI) has at least two return stages (BFC), wherein the turbomachine inner housing (TMI) has an inner surface (ISC) defining the inside of the turbomachine inner housing (TMI) and an outer surface (OSC), wherein the outer surface (OSC) has at least one recess (RRZ) extending radially inwards axially between two return stages (BFC), wherein the arrangement (ARG) furthermore comprises a turbomachine outer housing (TMO) surrounding the turbomachine inner housing (TMI), wherein the arrangement (ARG) has an axial low pressure side (LPS) and an axial high pressure side (HPS), wherein the arrangement (ARG) has a seal (STS), which extends in the circumferential direction and is arranged in a space (RBT) between the high pressure side (HPS) and the low pressure side (LPS) in such a manner that the space (RBT) is divided into a high pressure part (HPC) and a low pressure part (LPC), wherein the high-pressure part (HPC) is operating under a final pressure of the turbomachine, and the low-pressure part (LPC) is operating under an intake pressure, wherein the recesses (RRZ) are in each case arranged between the at least two adjacent return stages (BFC) and in the region of the high-pressure part (HPC), wherein the turbomachine inner housing (TMI) consists of up to 50% by weight of metal and at least 50% by weight of plastic.

2. Arrangement according to Claim 1, wherein the surface which is exposed to a process fluid during operation is provided with a coating (SCC), at least in some regions.

3. Arrangement according to Claim 2, the coating (SCC) consisting at least partially of a metal.

4. Arrangement according to Claim 1, wherein the recess (RRZ) or recesses (RRZ) extend over a cross-sectional area portion of the turbomachine inner housing (TMI) of at least 35%.

5. Arrangement (ARG) according to one of the preceding claims, wherein the turbomachine outer housing (TMO) is formed in a barrel design in such a manner that a dividing line (OCS) is provided transversely to the longitudinal axis (X).

6. Arrangement (ARG) according to Claim 5, wherein the dividing line (OCS) separates a cover (COV) from a barrel (BRL) of the turbomachine outer housing (TMO).

7. Arrangement according to one of the preceding claims, wherein at least the section which is formed in one piece, spanning at least two stages (STG), is produced by means of an additive manufacturing method.