Screw compressor

Abstract

The invention relates to a screw compressor (300), comprising a compressor block having a compressor housing (312), wherein two compressor screws (312a) are received and can be rotated in the compressor housing (312), the compressor housing (312) has an upstream inlet (314) for gas to be compressed and a downstream outlet (318) for compressed gas and, during an operation of the screw compressor (300), the gas is conveyed from the inlet (314) to the outlet (318), the pressure of the gas being increased by reducing the size of a movable chamber (320), which is formed by the compressor screws (312a), in the flow direction after the chamber has passed a control edge (322). According to the invention, the compressor housing (312) has a separation between a downstream high-temperature region (324) and an upstream low-temperature region (326), a material with a reduced thermal conductivity compared to the high-temperature region (324) being present at least in the region of the separation.

Description

[0001] screw compressor

[0002] Description

[0003] The present invention relates to a screw compressor comprising a compressor block with a compressor housing, wherein two compressor screws are rotatably received and driven in the compressor housing, wherein the compressor housing has an upstream inlet for gas to be compressed and a downstream outlet for compressed gas, and wherein, during operation of the screw compressor, the gas is conveyed from the inlet to the outlet, the pressure of the gas being increased by reducing the size of a movable chamber formed by the compressor screws in the direction of flow after it has passed a control edge.

[0004] Screw compressor blocks, or so-called compact units—that is, integrated units consisting of an intake filter, intake regulator, compressor block, separator tank, air separator, thermostat, and pressure relief valve—form the central component of screw compressors. The operating principle of screw compressors is based on two rotating screws within a common compressor housing. The rotation of the screws opens a chamber, which initially expands up to an inlet control edge. Up to this point, the chamber is open to intake. After the chamber passes the inlet control edge, it is largely sealed, and its volume begins to decrease behind the inlet control edge, thus compressing the gas inside.The compression process in such a chamber ends as soon as the chamber reaches an outlet control edge of the compressor housing, whereupon the compressed gas can be expelled and directed to a further purpose.

[0005] In an ideal screw compressor, the intake process gas, which could be process air, for example, has the same temperature and pressure at the start of compression as it did when entering the compressor. However, in real screw compressors, slight pressure losses and significant preheating of the gas in the intake section always occur. This preheating is caused, firstly, by contact with heated compressor components and, secondly, in compressors with injection cooling, by the backflow of warm cooling medium into the intake area. Measured values ​​sometimes show a preheating of the process gas of more than 30 K. Due to the well-known property of gases to expand with increasing temperature, the resulting expansion of the intake gas significantly reduces both the filling capacity and the efficiency of the compressor.

[0006] Up to now, the compressor housings of screw compressors have typically been made of cast iron or cast aluminum and generally feature a division between the actual housing and a bearing cover to allow the compressor rotors to be inserted into the housing during assembly. Furthermore, screw compressors known from the prior art generally have a flange on which an intake valve is mounted, and the connections between the aforementioned housing parts, as well as between the housing and the intake control valve, are generally designed to ensure significant metallic contact and thus very good heat conduction between the components.This results in a very uniform heating of the aforementioned components from the process gas outlet to the process gas inlet during the operation of such a compressor, causing heat transfer from the housing to the process gas in the inlet area as described above. However, as also mentioned previously, this type of heat transfer reduces the operating efficiency of the compressor.

[0007] Accordingly, there is potential to minimize the specific power consumption of such a compressor per compressed gas volume in order to reduce the system's operating costs and increase the compressor's efficiency. On the other hand, it is also desirable to keep the manufacturing costs for such compressors as low as possible, although reducing gap losses by tightening tolerances, and thus without advances in the underlying manufacturing technology, appears to be either impossible or only possible to a limited extent.

[0008] Accordingly, the object of the present invention is to eliminate the disadvantages of the prior art discussed above and to minimize the specific power consumption of a screw compressor without further restricting the tolerances or significantly increasing the manufacturing costs.

[0009] To solve this problem, a screw compressor of the type discussed above is proposed according to the invention, in which, as a further development according to the invention, the compressor housing has a separation between a downstream high-temperature area and an upstream low-temperature area, wherein at least in the area of ​​the separation a material with reduced thermal conductivity compared to the high-temperature area is present. It should be noted that screw compressors according to the invention can be, in particular, fluid-injected, preferably oil-injected screw compressors, in which such a design according to the invention can be implemented particularly advantageously.

[0010] Accordingly, the fundamental concept of the invention is to provide a screw compressor whose compressor housing is segmented into low and high temperature zones, and to minimize the heat flow between these zones by providing this separation. This measure is intended to minimize the preheating of the process gas between the inlet and the start of compression, and consequently increase the operating efficiency of the compressor. This effect results in particular from the fact that a significant reduction in preheating allows for improved filling, i.e., increased delivery capacity for the same compressor size, as well as improved efficiency, and thus increased delivery capacity with virtually unchanged energy consumption.The separation according to the invention between the high-temperature area and the low-temperature area can be realized with current manufacturing technology, so that no narrowing of tolerances is required and an increase in efficiency is possible without or with only minor additional costs.

[0011] In particular, the screw compressor according to the invention can be provided with the separation already mentioned in the area of ​​the control edge, which separates the intake area from the compression area of ​​the screw compressor in the manner explained above.

[0012] Alternatively or additionally, the separation can be designed in such a way that there is no direct metallic contact between the high-temperature and low-temperature areas. Generally, a design of the separation point is also desirable that minimizes the heat conduction cross-section between the high- and low-temperature areas of the housing. One way to achieve this is to design a separating element between the high-temperature and low-temperature areas in such a way that the heat conduction path through the material with low thermal conductivity is as long as possible.

[0013] As already indicated above, the high-temperature area of ​​the compressor housing can be made at least partially of cast iron or cast aluminum, so that at least for this area of ​​the compressor block, materials and manufacturing processes known per se can be used to keep the costs of the screw compressor according to the invention low.

[0014] Furthermore, in a first conceivable embodiment of a screw compressor according to the invention, the low-temperature section can be constructed, at least partially, of thin-walled shells and / or of a material with reduced thermal conductivity, wherein the material with reduced thermal conductivity can preferably be polyamide or polyphenylene sulfide (PPS), each particularly with glass fiber content. Regardless of the material used, the comparatively thin-walled shell construction also serves to reduce the heat conduction cross-section and thus contributes in any case to reducing upstream heat. In such an embodiment, as mentioned above, the high-temperature section, and thus the compression section of the screw compressor, can be constructed of conventional metal, and the separate low-temperature section can be made of a different material.The intake area can be made entirely of the material with reduced thermal conductivity, or, for example, an upper half-shell can be constructed of it, with the separation according to the invention being formed by the transition between the aforementioned materials. The half-shell can preferably begin in the area of ​​the control edge and encompass an inlet area of ​​the screw compressor.

[0015] In a variant of the embodiment described above, the low-temperature area, formed in a thin-walled shell construction and optionally from a material with reduced thermal conductivity, can essentially comprise the entire compressor housing, while the high-temperature area is formed by a bearing cover. In such an embodiment, the separation is accordingly provided at the transition between the compressor housing and the bearing cover. Here, as in the variant described above, the component provided in a thin-walled shell construction can be formed by a plastic part, for example, made of polyamide or polyphenylene sulfide (PPS) with glass fiber content, which can be manufactured, for example, by rotational molding or by blow molding.

[0016] In order to increase the mechanical strength of the screw compressor in the low-temperature region in such an embodiment, at least one downstream section of the low-temperature region can be comprised of a support structure made of a metallic material, preferably of the same material as the bearing cover.

[0017] In a further embodiment, which can in principle be combined with the first embodiment, the separation between the high-temperature and low-temperature areas can be formed by a local component, for example, a seal, with reduced thermal conductivity, preferably made of mica, PTFE, or ceramic. Accordingly, in such an embodiment, heat transfer between the high-temperature and low-temperature areas is locally inhibited within the aforementioned local component, and it is therefore possible for the low-temperature area to also be at least partially made of a metallic material, in particular the same material as the high-temperature area. Nevertheless, by minimizing the contact surfaces between the intake and compression sections of the compressor housing, heat transfer in the upstream direction of the process gas is minimized.

[0018] Furthermore, it is conceivable to provide an insert on the inside of the compressor housing for the low-temperature range, made of a material with reduced thermal conductivity. Such an insert in the intake area can thermally insulate an intake control valve located in the inlet area and protect the process gas to be compressed from unwanted preheating in the intake tract for as long as possible. The insert can be made, for example, of an injection-molded plastic material, in particular polyamide or polyphenylene sulfide (PPS), preferably with a glass fiber component. Furthermore, a splitter in the intake area of ​​the compressor screws can be integrated into the insert, and / or the insert can encompass an inlet area of ​​the screw compressor.

[0019] As already indicated above, the screw compressor according to the invention can further comprise a flange with an intake control valve in the area of ​​the inlet.

[0020] Further features and advantages of the present invention will become even clearer from the following description of a generic screw compressor and embodiments of the present invention when these are considered together with the accompanying figures. These show, in detail: Figure 1 the operating principle of a generic screw compressor by means of several successive schematic representations;

[0021] Figure 2 shows a first embodiment of a screw compressor according to the invention;

[0022] Figure 3 shows a second embodiment of an invention

[0023] screw compressor;

[0024] Figure 4 shows a third embodiment of a screw compressor according to the invention, each in schematic representation;

[0025] Figure 5 shows further views of the third embodiment from Figure 4;

[0026] Figure 6 shows a comparison of thermal profiles during operation of the generic screw compressor from Figure 1 compared with the screw compressor according to the invention from Figure 4; and

[0027] Figure 7 shows a fourth embodiment of a screw compressor according to the invention.

[0028] Figure 1 shows a generic screw compressor in a schematic sectional view from top left to bottom right in several successive views during its operation in order to explain the underlying operating principle.

[0029] The generic screw compressor 10 comprises a compressor housing 12 in which two schematically depicted compressor screws 12a are rotatably mounted and driven. Furthermore, it can be seen that in the upstream region of the flow direction of the process gas, indicated by arrows, a flange acting as an inlet 14 with an intake control valve 16 is provided, as well as downstream an outlet 18 for the ultimately compressed gas.

[0030] In the six successive illustrations from Figure 1, it can be seen that a movable chamber 20 formed by the compressor screws 12a is moved from the inlet 14 towards the outlet 18 by the rotation of the screws, with the intake of process gas taking place in the first three illustrations.

[0031] Subsequently, between the third and fourth illustrations, chamber 20 passes a control edge 22, after which chamber 20 is closed and the intake process ends. In the fifth illustration, it can further be seen that the volume of chamber 22 is progressively reduced, resulting in a compression of the process gas, until finally, in the sixth illustration, it is expelled from outlet 18 with a reduced volume and correspondingly higher pressure, whereby, according to the ideal gas law, the compressed gas has also heated up considerably.

[0032] The corresponding heating of the gas will consequently also lead to a heating of the compressor housing, which, due to its typically metallic construction, will become more uniform during operation. This means that heating of the compressor housing will also be observed in the area of ​​the inlet 14, and subsequently, the process gas will be heated even during the intake or suction process. This reduces the operating efficiency of the screw compressor shown here. The heating of the compressor housing originates particularly from areas where, in certain specific compressor designs, the gas is completely heated—i.e., the outlet in screw blocks and, in compact systems, the fully integrated separator. This results in a significantly more pronounced effect in compact systems.

[0033] Figure 2 now shows a first embodiment of a screw compressor according to the invention, which is designated by reference numeral 100, wherein the basic structure and operation of the screw compressor 100 corresponds to the generic screw compressor 10 from Figure 1, so that identical or similar components are designated with the same reference numerals, each increased by 100, and only the differences between the compressors from Figures 1 and 2 are explained, while otherwise reference is made to the description of the generic example from Figure 1.

[0034] In contrast to the screw compressor 10 from Figure 1, the screw compressor 100 according to the invention features a separation between a downstream high-temperature region 124 and an upstream low-temperature region 126, which is located essentially in the region of the control edge 122. The downstream high-temperature region 124 is formed from a metallic material in a similar manner to the screw compressor 10 from Figure 1, while the low-temperature region is constructed in a thin-walled shell design from a material with reduced thermal conductivity, for example, polyamide or polyphenylene sulfide with glass fiber content.

[0035] This measure reduces heat transfer from the compression zone of the screw compressor 100 to its intake zone, thus minimizing the heating of the process gas to be compressed and increasing the operating efficiency of the screw compressor 100. In the first embodiment shown in Figure 2, the separation according to the invention between the high-temperature zone 124 and the low-temperature zone 126 is formed by the contact area between these two parts of the compressor housing 112, which can be connected to each other in a tight and mechanically secure manner, for example, by a screw connection or riveting.

[0036] Figure 3 shows a second embodiment of a screw compressor according to the invention, designated by reference numeral 200, in which components analogous to the generic screw compressor 10 from Figure 1 with the same reference numeral, increased by 200, are designated. In this variant of a screw compressor 200 according to the invention, the separation between the high-temperature area 224 and the low-temperature area 226 is formed by a seal 228 with reduced thermal conductivity, which can be made, for example, of plastic, e.g., PA, mica, PTFE, or ceramic, and which serves as a local component within the meaning of the present invention. Such a local component could also be provided without a sealing function in alternative variants of the embodiment described here. Since the provision of this seal orSince the heat transport upstream of the high-temperature area 224 is locally prevented by the local component, the low-temperature area 226 can be formed from a metallic material in a similar way to the high-temperature area 224, but this material will heat up considerably less during operation of the screw compressor 200.

[0037] Figure 4 further shows a third embodiment of a screw compressor according to the invention, which is designated by reference numeral 300, wherein analogous components to the screw compressor 10 from Figure 1 are designated with the same reference numerals, increased by 300. It can be seen that, in contrast to the embodiments from Figures 2 and 3, in the screw compressor 300 the separation between the high-temperature area 324 and the low-temperature area 326 is not located in the area of ​​the control edge 322, but rather that an insert 328 is provided as the low-temperature area on the inside of the compressor housing 312 in the upstream area adjacent to the inlet 314 or the intake control valve 316.

[0038] This insert 328 can, for example, be made of a plastic injection molding material, in particular of polyamide or polyphenylene sulfide with glass fiber content, and further reference is made to Figure 5, in which this insert is shown in a sectional view on the plane area VV from Figure 4 in more detail compared with the schematic view from Figure 4.

[0039] It can be seen that the insert 328 also forms a splitter 330 in the intake area of ​​the compressor screws (not shown) in order to direct the flow of the process gas. The insert 328 extends along the inside of the compressor housing 312 and projects beyond it in the upper area, where the transition to the inlet 314 is provided in the form of a flange. Furthermore, it should be noted that the lower edge of the insert 328 can be designed in such a way as to deflect the process gas flow away from the housing wall in order to reduce preheating even downstream of the insert 328.

[0040] In this context, reference should be made to the thermal profiles in Figure 6, which shows the inlet region of the screw compressor 300 in operation on the left side, in a view similar to that in Figure 5, compared to the generic screw compressor 10 from Figure 1 during operation. The temperature scale shown below illustrates that significantly lower temperatures are present in the upstream part of the screw compressor 300 than in the screw compressor 10. This minimizes preheating of the gas to be compressed, and thus, by using the insert 326 in the low-temperature range, an increase in the operating efficiency of the screw compressor 300 is achieved compared to the screw compressor 10.

[0041] Finally, reference is made to Figure 7, which shows a fourth embodiment of a screw compressor according to the invention, designated by reference numeral 400, in which components analogous to the generic screw compressor 10 from Figure 1 with the same reference numeral, increased by 400, are designated. The fourth embodiment from Figure 7 can be considered a variant of the first embodiment from Figure 2, since here too the low-temperature section 426 is manufactured in a thin-walled shell construction from a material with reduced thermal conductivity. However, in this variant, the low-temperature section 426 essentially comprises the entire compressor housing 412, while the high-temperature section 424 is formed only by the bearing cover 430. Accordingly, the separation between the high-temperature section 424 and the low-temperature section 426 lies in the area of ​​the mounting or...of the transition of the bearing cover 430 to the compressor housing 412.

[0042] Furthermore, it should be noted that in this variant, to increase mechanical strength, a downstream section of the low-temperature area 426 is enclosed by a support structure 432 made of a metallic material, which can, for example, be the same material as that of the bearing cover 430.

Claims

Claims 1. Screw compressor (100, 200, 300, 400), comprising: a compressor block with a compressor housing (112, 212, 312, 412), wherein two compressor screws (112a, 212a, 312a, 412a) are rotatably mounted and driven in the compressor housing (112, 212, 312, 412); wherein the compressor housing (112, 212, 312, 412) has an upstream inlet (114, 214, 314, 414) for gas to be compressed and a downstream outlet (118, 218, 318, 418) for compressed gas and, in operation of the screw compressor (100, 200, 300, 400), the gas is conveyed from the inlet (114, 214, 314, 414) to the outlet (118, 218, 318, 418), the pressure of the gas being increased by reducing the size of a movable chamber (120, 220, 320, 420) formed by the compressor screws (112a, 212a, 312a, 412a) in the direction of flow. is characterized, after passing a control edge (122, 222, 322, 422), by the fact that the compressor housing (112, 212, 312,412) has a separation between a downstream high-temperature region (124, 224, 324, 424) and an upstream low-temperature region (126, 226, 326, 426), wherein at least in the region of the separation a material with reduced thermal conductivity compared to the high-temperature region (124, 224, 324, 424) is present.

2. Screw compressor (100, 200) according to claim 1, wherein the separation is provided in the area of ​​the control edge (122, 222).

3. Screw compressor (100, 200, 300, 400) according to any of the preceding claims, wherein the separation is designed such that there is no direct metallic contact between the high temperature area (124, 224, 324, 424) and the low temperature area (126, 226, 326, 426).

4. Screw compressor (100, 200, 300, 400) according to any of the preceding claims, wherein the high temperature area (124, 224, 324, 424) of the compressor housing (112, 212, 312, 412) is at least partially made of cast iron or cast aluminum.

5. Screw compressor (100, 400) according to one of the preceding claims, wherein the low-temperature section (126, 426) is at least partially constructed in a thin-walled shell design and / or from the material with reduced thermal conductivity, wherein the material with reduced thermal conductivity is preferably polyamide or polyphenylene sulfide, each in particular with glass fiber content.

6. Screw compressor (400) according to claim 5, wherein the low-temperature area (426) formed in thin-walled shell construction and optionally from the material with reduced thermal conductivity essentially forms the entire compressor housing (412) and the high-temperature area (424) is formed by a bearing cover (430).

7. Screw compressor (400) according to claim 6, wherein at least one downstream section of the low temperature range (426) is comprised by a support structure (432) made of a metallic material, preferably of the same material as the bearing cover (430).

8. Screw compressor (100) according to claim 5, wherein the low-temperature area (126) within an upper half-shell is made of the material with reduced thermal conductivity and the high-temperature area (124) is, for example, of metallic construction, wherein preferably the half-shell begins in the area of ​​the control edge (122) and includes an inlet area of ​​the screw compressor.

9. Screw compressor (200) according to one of the preceding claims, wherein the separation is formed by a local component, for example a seal (228), with reduced thermal conductivity between the high temperature area (224) and the low temperature area (226), preferably consisting of plastic, e.g. PA, mica, PTFE or ceramic, so that, in particular, by minimizing the contact surfaces between an intake part and a compression part of the compressor housing (212), the heat transfer in the upstream direction is minimized.

10. Screw compressor (200) according to the preceding claim, wherein the low temperature range (226) is at least partially formed from a metallic material, in particular the same material as the high temperature range (224).

11. Screw compressor (300) according to one of the preceding claims, wherein the low temperature range (326) is an insert (328) on the inside of the compressor housing (312).

12. Screw compressor (300) according to the preceding claim, wherein the insert (328) is formed from a plastic injection molding material, in particular from polyamide or polyphenylene sulfide, each preferably with glass fiber content.

13. Screw compressor (300) according to one of claims 11 and 12, wherein a splitter (330) in the intake area of ​​the screws (312a) is integrated into the insert (328).

14. Screw compressor (300) according to one of claims 11 to 13, wherein the insert (328) comprises an inlet area of ​​the screw compressor (300).

15. Screw compressor (100, 200, 300, 400) according to one of the preceding claims, further comprising a flange with an intake control valve in the area of ​​the inlet (114, 214, 314, 414).

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