Multistage series energy recovery air compressor unit

Abstract

A multistage series energy recovery air compressor unit, comprising at least two stages of air compressors and a heat exchanger (6), wherein each stage of air compressor comprises a compressor (2), an electric motor (3) and a turbine (4), with an output end of the electric motor (3) and an output end of the turbine (4) both being connected to the compressor (2); an air source is in communication with inlets of multiple stages of compressors (2); the multiple stages of compressors (2) are connected to each other in series; a valve for interrupting the connection is provided between at least some adjacent two stages of compressors (2); an outlet of the last stage of compressor (2) is connected to a hot-side inlet of the heat exchanger (6); compressed air is cooled by the heat exchanger (6) and is then conveyed to a downstream device; and a waste gas outlet of the downstream device is in communication with at least one turbine (4), so as to cause a discharged waste gas to enter the turbine (4) to expand and do work. Using the multiple stages of air compressors connected in series can realize a higher compressor pressure ratio and a higher turbine expansion ratio to meet the use requirements for high altitudes and high pressure ratios, thereby meeting multi-load operation requirements at different altitudes; moreover, the requirements for a low load on the ground and a high load at a high altitude are met, thereby realizing efficient operation under full operating conditions.

Description

Multi-stage series energy recovery air compressor unit Technical Field

[0001] The present invention relates to the field of air compressors, and in particular to a multi-stage series energy recovery air compressor unit. Background Art

[0002] Proton exchange membrane fuel cells, with their high efficiency and cleanliness, have become a popular technology in the energy and power sector. Following their widespread adoption in land transportation, fuel cell engines for aviation have also become a research hotspot. Typical aircraft cruise at altitudes approaching 10,000 meters, placing high demands on fuel cell engines' altitude adaptability to ensure reliable operation.

[0003] For fuel cell systems, the amount of air entering the stack and its absolute pressure are key parameters that affect the stack's operating state and output power. To maintain the same stack output power at different altitudes, the absolute pressure and air volume at the stack inlet must remain consistent. Therefore, the air compressor needs to operate under both high and low pressure ratio conditions. Aviation applications, in particular, typically require a pressure ratio as high as 10, placing high demands on the design of the air supply system. The single-stage or two-stage compression air compressors typically used in automotive fuel cell systems cannot meet the altitude requirements of aviation applications. Furthermore, the air compressor's power consumption increases rapidly as the pressure ratio increases, resulting in reduced efficiency in the fuel cell system. Therefore, designing an air compressor with high efficiency and strong altitude adaptability is of great significance to aviation fuel cell systems.

[0004] Summary of the Invention

[0005] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0006] The fuel cell air compressor in the related art is generally driven by a motor. It is impossible to achieve a pressure ratio requirement of up to 10 by increasing the motor power and the size of the compressor, and it is also impossible to achieve low-load ground operation and high-load high-altitude cruising conditions at the same time. In response to the above problems, the related art has proposed a solution of multi-stage air compressors running in series to increase the pressure ratio of the air compressor. For example, a three-stage compression solution is used to achieve high-pressure ratio operation, while a single-stage turbine is used to recover the energy of the fuel cell stack exhaust gas and reduce the power consumption of the air compressor. However, a single-stage turbine cannot achieve efficient operation at different altitudes, so the system cannot achieve energy recovery in all working conditions, affecting the system efficiency.

[0007] The present invention aims to solve one of the technical problems in the related art to at least a certain extent. To this end, an embodiment of the present invention provides a multi-stage series energy recovery air compressor unit.

[0008] The multi-stage series energy recovery air compressor unit of an embodiment of the present invention includes: at least two-stage air compressors, each stage of the air compressor includes a compressor, a motor and a turbine, the output end of the motor and the output end of the turbine are both connected to the compressor, the air source is connected to the inlet of the multi-stage compressor, the multi-stage compressors are connected in series, and a valve for cutting off the connection is provided between at least some adjacent two stages of the compressors; a heat exchanger, the outlet of the last stage compressor is connected to the hot side inlet of the heat exchanger, the compressed air is cooled by the heat exchanger and then input into the downstream device, and the exhaust gas outlet of the downstream device is connected to at least one of the turbines so that the exhausted exhaust gas enters the turbine to expand and perform work.

[0009] The multi-stage series energy recovery air compressor unit of an embodiment of the present invention includes a multi-stage air compressor. Each stage of the air compressor uses a turbine and a motor to simultaneously drive the compressor. The turbine can recover exhaust gas energy, reduce the power consumption of the air compressor unit, and improve the overall efficiency of the air compressor unit. When applied to a fuel cell system, it can improve the efficiency of the fuel cell system. The use of a multi-stage series air compressor can achieve a higher compressor pressure ratio and turbine expansion ratio, meeting the requirements of high altitude and high pressure ratio. At the same time, the number of operating air compressor stages can be flexibly selected to meet the multi-load operation requirements at different altitudes, simultaneously meeting the requirements of low load on the ground and high load at high altitude, and achieving efficient operation under all working conditions.

[0010] Therefore, the multi-stage series energy recovery air compressor unit of the embodiment of the present invention has the characteristics of high efficiency and strong altitude adaptability.

[0011] In some embodiments, the outlet of the turbine connected to the exhaust gas outlet is connected to the cold side inlet of the heat exchanger, and the low-temperature gas after expansion and work enters the heat exchanger to exchange heat with the compressed air.

[0012] In some embodiments, multiple stages of the turbines are connected in series, and in two adjacent stages of the turbines, the outlet of the lower stage turbine is connected to the inlet of the upper stage turbine, and the heat exchanger is connected between the two adjacent stages of the turbines.

[0013] In some embodiments, in two adjacent stages of compressors, the outlet of the upper-stage compressor is connected to the inlet of the lower-stage compressor, and the energy recovery air compressor unit includes at least one intercooler, which is connected in series between the two connected stages of compressors for cooling the compressed air.

[0014] In some embodiments, the air compressor includes a low-pressure stage air compressor and a high-pressure stage air compressor, the low-pressure stage air compressor includes a low-pressure compressor, a low-pressure stage motor and a low-pressure turbine, the output end of the low-pressure stage motor and the output end of the low-pressure turbine are both connected to the low-pressure compressor, the high-pressure stage air compressor includes a high-pressure compressor, a high-pressure stage motor and a high-pressure turbine, the output end of the high-pressure stage motor and the output end of the high-pressure turbine are both connected to the high-pressure compressor, the outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor, a low-pressure compressor outlet valve is provided on the connecting pipeline between the low-pressure compressor and the high-pressure compressor, the outlet of the high-pressure compressor is connected to the hot side inlet of the heat exchanger, and the exhaust gas outlet of the downstream device is connected to the high-pressure turbine.

[0015] In some embodiments, the outlet of the high-pressure turbine is in communication with the cold-side inlet of the heat exchanger, and the cold-side outlet of the heat exchanger is in communication with the inlet of the low-pressure turbine.

[0016] In some embodiments, the low-pressure turbine bypass line, the cold side outlet of the heat exchanger is also connected to one end of the low-pressure turbine bypass line, the other end of the low-pressure turbine bypass line is emptied, and the cold side outlet of the heat exchanger can be selectively connected to the low-pressure turbine or the low-pressure turbine bypass line.

[0017] In some embodiments, the multi-stage series energy recovery air compressor unit further includes: an intercooler, which is connected in series between the low-pressure compressor and the high-pressure compressor, and is used to cool the compressed air output by the low-pressure compressor; and / or, a filter, the outlet of the air source is connected to the filter, and the outlet of the filter is connected to the inlet of each of the low-pressure compressor and the high-pressure compressor.

[0018] In some embodiments, at least one of the low-pressure turbine and the high-pressure turbine is a variable geometry turbine.

[0019] In some embodiments, the multi-stage series energy recovery air compressor unit further includes a motor cooling air pipeline, one end of which is connected to the outlet of the air source, and the other end is connected to the cooling inlet of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a multi-stage series energy recovery air compressor unit according to an embodiment of the present invention.

[0021] FIG2 is a multi-stage series energy recovery air compressor unit according to another embodiment of the present invention.

[0022] Figure numerals: filter 1, compressor 2, low-pressure compressor 2a, high-pressure compressor 2b, motor 3, low-pressure stage motor 3a, high-pressure stage motor 3b, turbine 4, low-pressure turbine 4a, high-pressure turbine 4b, intercooler 5, heat exchanger 6, fuel cell stack 7, intake bypass line 8, inlet bypass valve 81, low-pressure compressor outlet valve 9, low-pressure turbine bypass line 10, low-pressure turbine bypass valve 101, motor cooling air line 11. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] As shown in Figures 1 and 2, the multi-stage series energy recovery air compressor unit provided by the embodiment of the present invention includes: at least two stages of air compressors and a heat exchanger 6. Each stage of the air compressor includes a compressor 2, a motor 3 and a turbine 4. The output end of the motor 3 and the output end of the turbine 4 are both connected to the compressor 2 to drive the compressor 2 to compress air. The air source is connected to the inlet of the multi-stage compressor 2. The multi-stage compressors 2 are connected in series, that is, in two adjacent stages of compressors 2, the outlet of the upper compressor 2 is connected to the inlet of the lower compressor 2. The compressed air compressed by the upper compressor 2 enters the lower compressor 2 for further compression. A valve for cutting off the connection is provided between at least some of the adjacent two stages of compressors 2. Under certain working conditions, the valve is closed and the compressor 2 located upstream of the valve is shut down.

[0025] Heat exchanger 6 has a hot side and a cold side. The medium flowing through the hot side exchanges heat with the medium flowing through the cold side, causing the hot side medium's temperature to drop and cool, while the cold side medium's temperature to rise and heat. The outlet of the final-stage compressor 2 is connected to the hot side inlet of heat exchanger 6. Compressed air enters the hot side of heat exchanger 6, is cooled by heat exchanger 6, and then fed into downstream devices for reaction. The exhaust outlet of these downstream devices is connected to at least one turbine 4, allowing excess exhaust gas to enter the connected turbine 4 and expand to produce work.

[0026] The following description uses a multi-stage series energy recovery air compressor assembly in a fuel cell system as an example. In this embodiment of the present invention, the downstream device is a fuel cell stack 7, and the air compressor assembly is used to provide the fuel cell stack 7 with compressed air for the reaction. The air and hydrogen react within the stack. The exhaust outlet of the fuel cell stack 7 is connected to at least one turbine 4. Excess air and water vapor discharged from the exhaust outlet of the fuel cell stack 7 enter the connected turbine 4, where they expand and produce work.

[0027] Because the air source is connected to the inlet of the multi-stage compressor 2, air can be selectively introduced into any compressor 2. The valve upstream of the compressor 2 directly connected to the air source is closed to shut down the remaining compressors 2 located upstream of that compressor 2. After being compressed by this compressor 2, the air flows to the downstream compressors 2. The compressed air discharged from the last-stage compressor 2 enters the hot side of the heat exchanger 6, cools down, and enters the fuel cell stack 7 to participate in the reaction. By changing the position of the compressor 2 directly introduced by the air, the number of air compression stages is adjusted, and the pressure ratio is changed. When the fuel cell is operating at high load, the number of operating compressors 2 is increased, the air pressure ratio is increased, and the air compressor group operates under a high-pressure ratio condition. When the fuel cell is operating at low load, the number of operating compressors 2 is reduced, the air pressure ratio is reduced, and the air compressor group operates under a low-pressure ratio condition.

[0028] The multi-stage series energy recovery air compressor unit of an embodiment of the present invention includes a multi-stage air compressor. Each stage of the air compressor uses a turbine and a motor to simultaneously drive the compressor. The turbine can recover exhaust gas energy, reduce the power consumption of the air compressor unit, and improve the overall efficiency of the air compressor unit. When applied to a fuel cell system, it can improve the efficiency of the fuel cell system. The use of a multi-stage series air compressor can achieve a higher compressor pressure ratio and turbine expansion ratio, meeting the requirements of high altitude and high pressure ratio. At the same time, the number of operating air compressor stages can be flexibly selected to meet the multi-load operation requirements at different altitudes, simultaneously meeting the requirements of low load on the ground and high load at high altitude, and achieving efficient operation under all working conditions.

[0029] Therefore, the multi-stage series energy recovery air compressor unit of the embodiment of the present invention has the characteristics of high efficiency and strong altitude adaptability.

[0030] In some embodiments, the outlet of the turbine 4 connected to the outlet of the fuel cell stack 7 is connected to the cold side inlet of the heat exchanger 6. The exhaust gas discharged from the fuel cell stack 7 enters the turbine 4 to expand and do work. The low-temperature gas after expansion enters the cold side of the heat exchanger 6 and exchanges heat with the high-temperature compressed air on the hot side to reduce the temperature of the compressed air. At the same time, the temperature of the exhaust gas increases, thereby fully utilizing the cold energy in the exhaust gas discharged from the fuel cell stack 7. This part of the cold energy is used to cool the compressed air before entering the fuel cell stack 7 to meet the compressed air temperature requirement of the fuel cell stack 7.

[0031] In some embodiments, multiple turbine stages 4 are connected in series. The outlet of the lower turbine stage 4 is connected to the inlet of the upper turbine stage 4 between two adjacent turbine stages 4. After the exhaust gas expands and generates work in the lower turbine stage 4, it enters the upper turbine stage 4 to continue expanding and generating work, and is ultimately discharged into the atmosphere. A heat exchanger 6 is connected between the two adjacent turbine stages 4. Before entering the upper turbine stage 4, the low-temperature exhaust gas enters the heat exchanger 6 to exchange heat with the high-temperature compressed air, thereby reducing the compressed air temperature.

[0032] The pressure of the exhaust gas decreases after expansion and work, so in the adjacent two-stage turbine 4, there is a high-pressure turbine with relatively high pressure and a low-pressure turbine with relatively low pressure, wherein the high-pressure turbine is located at the lower stage of the low-pressure turbine, that is, the high-pressure turbine is the lower-stage turbine 4 of the above-mentioned adjacent two-stage turbine 4, and the low-pressure turbine is the upper-stage turbine 4 of the above-mentioned adjacent two-stage turbine 4. The exhaust gas first enters the high-pressure turbine, expands and does work in the high-pressure turbine, and then enters the low-pressure turbine to further expand and do work, thereby fully recovering the exhaust gas energy of the fuel cell stack, further reducing the power consumption of the air compressor unit, improving the overall efficiency of the air compressor unit, and thereby improving the efficiency of the fuel cell system.

[0033] The heat exchanger 6 is connected between two adjacent stages of the turbine 4. The temperature of the exhaust gas increases as it passes through the heat exchanger 6, which helps to improve the recovery work of the low-pressure turbine and improve the efficiency of the unit. At the same time, it avoids icing at the low-pressure turbine outlet, thereby improving the reliability of the unit. It is particularly suitable for high-altitude and low-temperature working conditions, so that the air compressor unit of the embodiment of the present invention can ensure efficient and reliable application in the aviation field.

[0034] As an example, as shown in FIG1 , the heat exchanger 6 is connected between two adjacent turbines 4. In other embodiments, the air compressor unit includes more than two turbines 4, for example, the air compressor unit includes three turbines 4, and the heat exchanger 6 can be connected between any two adjacent turbines 4, preferably between the last two stages of turbines 4.

[0035] In some embodiments, in two adjacent stages of compressors 2, the outlet of the upper-stage compressor 2 is connected to the inlet of the lower-stage compressor 2, and the energy recovery air compressor unit includes at least one intercooler 5, which is connected in series between the two connected stages of compressors 2 and is used to cool the compressed air. The temperature of the compressed air is reduced to reduce the compression work of the lower-stage compressor 2 and improve the efficiency of the air compressor unit.

[0036] The pressure of air increases after being compressed by the compressor 2. Therefore, in the two adjacent stages of the compressor 2, there is a high-pressure compressor with relatively high pressure and a low-pressure compressor with relatively low pressure. The high-pressure compressor is located below the low-pressure compressor, that is, the high-pressure compressor is the lower-stage compressor 2 of the two adjacent stages of the compressor 2, and the low-pressure compressor is the upper-stage compressor 2 of the two adjacent stages of the compressor 2. The air first enters the low-pressure compressor, is compressed by the low-pressure compressor, and then enters the high-pressure compressor for further compression. Before entering the high-pressure compressor, the air is cooled by the intercooler 5 to reduce the temperature of the compressed air. The provision of the intercooler 5 helps to reduce the compression work of the high-pressure compressor.

[0037] The following describes a multi-stage series energy recovery air compressor unit in a specific embodiment of the present invention according to Figure 1, wherein the energy recovery air compressor unit is a two-stage series energy recovery air compressor unit, including a two-stage air compressor and a heat exchanger 6, the two-stage air compressors are respectively a low-pressure air compressor and a high-pressure air compressor, the low-pressure air compressor is the upper-stage air compressor, and the high-pressure air compressor is the lower-stage air compressor.

[0038] As shown in Figure 1, the low-pressure air compressor includes a low-pressure compressor 2a, a low-pressure motor 3a, and a low-pressure turbine 4a. The output ends of the low-pressure motor 3a and the output ends of the low-pressure turbine 4a are both connected to the low-pressure compressor 2a. The low-pressure motor 3a and the low-pressure turbine 4a are used to drive the low-pressure compressor 2a. Specifically, one end of the output shaft of the low-pressure motor 3a is connected to the low-pressure compressor 2a, and the other end is connected to the low-pressure turbine 4a. The low-pressure turbine 4a drives the low-pressure compressor 2a via the output shaft of the low-pressure motor 3a.

[0039] The high-pressure air compressor includes a high-pressure compressor 2b, a high-pressure motor 3b, and a high-pressure turbine 4b. The output ends of the high-pressure motor 3b and the high-pressure turbine 4b are both connected to the high-pressure compressor 2b. The high-pressure motor 3b and the high-pressure turbine 4b are used to drive the high-pressure compressor 2b. Specifically, one end of the output shaft of the high-pressure motor 3b is connected to the high-pressure compressor 2b, and the other end is connected to the high-pressure turbine 4b. The high-pressure turbine 4b drives the high-pressure compressor 2b via the output shaft of the high-pressure motor 3b.

[0040] The structure in which the low-pressure turbine 4a is coaxially connected to the low-pressure compressor 2a and the high-pressure turbine 4b is coaxially connected to the high-pressure compressor 2b can directly use the exhaust gas energy recovered by the turbine 4 to drive the compressor 2, reduce the power consumption of the two-stage air compressor, and improve the overall efficiency of the unit.

[0041] As shown in Figure 1, the energy recovery air compressor unit includes an intercooler 5 and a filter 1. The outlet of the air source (atmosphere) is connected to the filter 1, and the outlet of the filter 1 is connected to the inlet of each of the low-pressure compressor 2a and the high-pressure compressor 2b. The filter 1 is used to filter the air. Specifically, the filter 1 is located adjacent to the low-pressure compressor 2a and is connected to the high-pressure compressor 2b via an intake bypass line 8. The intake bypass line 8 is equipped with an inlet bypass valve 81 for controlling air flow. The outlet of the low-pressure compressor 2a is connected to the inlet of the high-pressure compressor 2b. A low-pressure compressor outlet valve 9 is provided on the connecting line between the low-pressure compressor 2a and the high-pressure compressor 2b. Under high pressure ratio conditions, the inlet bypass valve 81 is closed, the low-pressure compressor outlet valve 9 is opened, and the air enters the low-pressure compressor 2a through the filter 1. After being output from the low-pressure compressor 2a, it enters the high-pressure compressor 2b for further compression. Under low pressure ratio conditions, the inlet bypass valve 81 is opened, the low-pressure compressor outlet valve 9 is closed, and the air enters the high-pressure compressor 2b through the filter 1 and directly enters the high-pressure compressor 2b for compression.

[0042] Intercooler 5 is connected in series between low-pressure compressor 2a and high-pressure compressor 2b. It uses low-temperature ambient air to cool the compressed air output by low-pressure compressor 2a, reducing the compression work of the high-pressure compressor and improving unit efficiency. In the embodiment shown in Figure 1, the low-pressure compressor outlet valve 9 is located downstream of intercooler 5.

[0043] The outlet of high-pressure compressor 2b is connected to the hot-side inlet of heat exchanger 6, and the outlet of fuel cell stack 7 is connected to high-pressure turbine 4b. The outlet of high-pressure turbine 4b is connected to the cold-side inlet of heat exchanger 6, and the cold-side outlet of heat exchanger 6 is connected to the inlet of low-pressure turbine 4a, so that the exhaust gas after heat exchange enters low-pressure turbine 4a for further expansion and work.

[0044] The exhaust from high-pressure compressor 2b is at a higher temperature, while the exhaust from high-pressure turbine 4b is at a lower temperature. Heat exchange between the two occurs in heat exchanger 6, raising the exhaust temperature of high-pressure turbine 4b. This increases the energy content of the exhaust gas, improving the recovery work of low-pressure turbine 4a, further reducing power consumption and improving efficiency. Furthermore, the increased inlet temperature of low-pressure turbine 4a also increases the outlet temperature of low-pressure turbine 4a, preventing icing in the low-temperature environment of high altitude and improving the reliability of the unit's operation.

[0045] As shown in Figure 1, the multi-stage series energy recovery air compressor unit also includes a low-pressure turbine bypass line 10. The cold-side outlet of the heat exchanger 6 is also connected to one end of the low-pressure turbine bypass line 10, and the other end of the low-pressure turbine bypass line 10 is exhausted. The cold-side outlet of the heat exchanger 6 can selectively be connected to the low-pressure turbine 4a or the low-pressure turbine bypass line 10. Under high-pressure ratio conditions, the low-pressure stage air compressor operates, and the cold-side outlet of the heat exchanger 6 is connected to the inlet of the low-pressure turbine 4a. The exhaust gas after heat exchange enters the low-pressure turbine 4a for further expansion and work. Under low-pressure ratio conditions, the low-pressure stage air compressor does not operate, and the cold-side outlet of the heat exchanger 6 is connected to the low-pressure turbine bypass line 10. The exhaust gas after heat exchange is exhausted through the low-pressure turbine bypass line 10. As shown in Figure 1, the low-pressure turbine bypass line 10 is provided with a low-pressure turbine bypass valve 101 for controlling gas flow.

[0046] The following describes the operation method of the multi-stage series energy recovery air compressor unit based on Figure 1 as an example.

[0047] When the fuel cell system is operating at high load, air from the atmosphere passes through filter 1 and enters low-pressure compressor 2a. After being compressed in low-pressure compressor 2a, it enters intercooler 5 for cooling. The cooled compressed air then enters high-pressure compressor 2b for further compression. The secondary compressed air exits high-pressure compressor 2b and enters heat exchanger 6 for cooling. The cooled compressed air then enters fuel cell stack 7 for a chemical reaction. The remaining air and some of the generated water vapor (exhaust gas) are discharged from the fuel cell stack 7 and enter high-pressure turbine 4b for expansion and work. The low-temperature exhaust gas enters heat exchanger 6 to exchange heat with the hot-side compressed air, raising its temperature. It then enters low-pressure turbine 4a for further expansion and work, and is discharged into the atmosphere through the outlet of low-pressure turbine 4a. The high-pressure turbine 4b and high-pressure stage motor 3b jointly drive the high-pressure compressor 2b, while the low-pressure turbine 4a and low-pressure stage motor 3a jointly drive the low-pressure compressor 2a.

[0048] When the fuel cell system is operating at low load, the inlet bypass valve 81 is opened, the low-pressure compressor outlet valve 9 is closed, and the low-pressure turbine bypass valve 101 is opened. Air enters the high-pressure compressor 2b directly from the outlet of the filter 1 through the air intake bypass line 8. After compression, it passes through the heat exchanger 6 and enters the fuel cell stack 7. The exhaust gas from the fuel cell stack 7 enters the high-pressure turbine 4b and expands. After passing through the heat exchanger 6, it enters the low-pressure turbine bypass line 10 and is discharged into the atmosphere through the low-pressure turbine bypass line 10. At this time, the low-pressure stage air compressor is not running, and the high-pressure stage air compressor operates independently to supply air to the fuel cell stack 7, realizing the single-stage compression operation scheme of the high-pressure stage air compressor.

[0049] This embodiment adopts a two-stage series energy recovery air compressor unit, which can achieve a higher compressor pressure ratio and turbine expansion ratio to meet the use requirements of high altitude and high pressure ratio; the turbine and motor are used to drive the compressor at the same time to recover the exhaust gas energy of the fuel cell stack, reduce the power consumption of the two-stage air compressor, improve the overall efficiency of the unit, and improve the efficiency of the fuel cell system; an intake bypass line is set, and two schemes of single-stage air compressor operation and two-stage air compressor series operation can be flexibly selected to meet the needs of low load on the ground and high load at high altitude, and achieve efficient operation under all working conditions; the intercooler and heat exchanger can help reduce the compression work of the high-pressure compressor, increase the recovery work of the low-pressure turbine, improve the efficiency of the unit, and avoid icing at the low-pressure turbine outlet, thereby improving the reliability of the unit.

[0050] Furthermore, in some embodiments, the motor 3 adopts an air-cooling solution, and the energy recovery air compressor unit also includes a motor cooling air pipeline 11, one end of the motor cooling air pipeline 11 is connected to the outlet of the air source, and the other end is connected to the cooling inlet of the motor 3, and the motor cooling air pipeline 11 is used to introduce air to cool the motor 3.

[0051] As an example, as shown in Figure 2, both the low-voltage motor 3a and the high-voltage motor 3b adopt an air-cooling solution. A cooling air pipeline is provided in the unit. One end of the motor cooling air pipeline 11 is connected to the outlet of the filter 1, and the other end is connected to the cooling inlet of the low-voltage motor 3a. The cooling outlet of the low-voltage motor 3a is connected to the cooling inlet of the high-voltage motor 3b. After the air cools the low-voltage motor 3a in the low-voltage motor 3a, it enters the high-voltage motor 3b for cooling and is finally discharged into the atmosphere.

[0052] In some embodiments, at least one of the low-pressure turbine 4a and the high-pressure turbine 4b is a variable geometry turbine, which can flexibly adapt to the high and low load operating conditions of the system, improve the exhaust gas energy recovery efficiency, and reduce the overall power consumption of the unit.

[0053] In some optional embodiments, the low-pressure turbine 4a is a fixed-geometry turbine, and the high-pressure turbine 4b is a variable-geometry turbine. When the high-pressure stage air compressor operates independently under low-load conditions, the geometry of the high-pressure turbine 4b can be adjusted to flexibly adapt to different fuel cell stack operating points. During high-load operation, the high-pressure turbine 4b combines with the fixed-geometry low-pressure turbine 4a to achieve high expansion ratio operation.

[0054] In other optional embodiments, the low-pressure turbine 4a is a variable-geometry turbine, and the high-pressure turbine 4b is a fixed-geometry turbine. During low-load operation, when the high-pressure stage air compressor operates independently, the high-pressure turbine 4b operates independently with fixed geometry, facilitating fuel cell system control. During high-load operation, the high-pressure turbine 4b operates in conjunction with the variable-geometry low-pressure turbine 4a, flexibly adapting to different operating points.

[0055] In other optional embodiments, both the low-pressure turbine 4a and the high-pressure turbine 4b are variable-geometry turbines. When the high-pressure stage air compressor operates independently under low-load conditions, the geometry of the high-pressure turbine 4b can be adjusted to flexibly adapt to different fuel cell stack operating points. During high-load operation, the variable-geometry high-pressure turbine 4b operates in conjunction with the variable-geometry low-pressure turbine 4a, flexibly adapting to different operating points.

[0056] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0058] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0059] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0060] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0061] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A multi-stage series energy recovery air compressor unit, characterized in that: include: At least two-stage air compressor, each stage of the air compressor comprises a compressor, a motor and a turbine, the output end of the motor and the output end of the turbine are connected to the compressor, the air source is connected to the inlet of the multi-stage compressor, the multi-stage compressor is connected in series, and a valve for cutting off the connection is provided between at least two adjacent stages of the compressor; The outlet of the last-stage compressor is connected to the hot side inlet of the heat exchanger, and the compressed air is cooled by the heat exchanger and then input into the downstream device. The exhaust gas outlet of the downstream device is connected to at least one of the turbines so that the exhausted exhaust gas enters the turbine to expand and perform work.

2. The multi-stage series energy recovery air compressor unit according to claim 1 is characterized in that: The outlet of the turbine communicated with the exhaust gas outlet is communicated with the cold side inlet of the heat exchanger, and the low-temperature gas after expansion and work enters the heat exchanger to exchange heat with the compressed air.

3. The multi-stage series energy recovery air compressor unit according to claim 2 is characterized in that: The multiple stages of turbines are connected in series, and in two adjacent stages of turbines, the outlet of the lower stage turbine is connected to the inlet of the upper stage turbine, and the heat exchanger is connected between the two adjacent stages of turbines.

4. The multi-stage series energy recovery air compressor unit according to any one of claims 1 to 3, characterized in that: In two adjacent compressor stages, the outlet of the upper compressor is connected to the inlet of the lower compressor, and the energy recovery air compressor unit includes at least one intercooler, which is connected in series between the two connected compressor stages for cooling the compressed air.

5. The multi-stage series energy recovery air compressor unit according to any one of claims 1 to 4, characterized in that: The air compressor includes a low-pressure stage air compressor and a high-pressure stage air compressor. The low-pressure stage air compressor includes a low-pressure compressor, a low-pressure stage motor and a low-pressure turbine. The output end of the low-pressure stage motor and the output end of the low-pressure turbine are both connected to the low-pressure compressor. The high-pressure stage air compressor includes a high-pressure compressor, a high-pressure stage motor and a high-pressure turbine. The output end of the high-pressure stage motor and the output end of the high-pressure turbine are both connected to the high-pressure compressor. The outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor. A low-pressure compressor outlet valve is provided on the connecting pipeline between the low-pressure compressor and the high-pressure compressor. The outlet of the high-pressure compressor is connected to the hot side inlet of the heat exchanger, and the exhaust gas outlet of the downstream device is connected to the high-pressure turbine.

6. The multi-stage series energy recovery air compressor unit according to claim 5, characterized in that: The outlet of the high-pressure turbine is communicated with the cold-side inlet of the heat exchanger, and the cold-side outlet of the heat exchanger is communicated with the inlet of the low-pressure turbine.

7. The multi-stage series energy recovery air compressor unit according to claim 6, characterized in that: A low-pressure turbine bypass pipeline, the cold side outlet of the heat exchanger is also connected to one end of the low-pressure turbine bypass pipeline, the other end of the low-pressure turbine bypass pipeline is emptied, and the cold side outlet of the heat exchanger can be selectively connected to the low-pressure turbine or the low-pressure turbine bypass pipeline.

8. The multi-stage series energy recovery air compressor unit according to any one of claims 5 to 7, characterized in that: Also includes: an intercooler, the intercooler being connected in series between the low-pressure compressor and the high-pressure compressor and being used for cooling the compressed air output by the low-pressure compressor; and / or, A filter, an outlet of the air source is in communication with the filter, and an outlet of the filter is in communication with an inlet of each of the low-pressure compressor and the high-pressure compressor.

9. The multi-stage series energy recovery air compressor unit according to any one of claims 5 to 8, characterized in that: At least one of the low-pressure turbine and the high-pressure turbine is a variable geometry turbine.

10. The multi-stage series energy recovery air compressor unit according to any one of claims 1 to 9, characterized in that: It also includes a motor cooling air pipeline, one end of which is connected to the outlet of the air source, and the other end of which is connected to the cooling inlet of the motor.

Images