Air compression device

Abstract

The invention provides an air compression device. The air compression device is provided with a buffer tank which is arranged at a preset position of an air return pipe and is used for temporarily storing return air.

Description

Technical Field

[0001] The present invention relates to an air compression device. Background Art

[0002] Patent document 1 discloses: "An oil-free rotary compression device, characterized in that a return gas pipe having a flow control mechanism is branched from the exhaust gas pipe and connected to the suction side of the rotary compressor in such a manner that the suction pressure is increased by returning a portion of the exhaust gas to the suction side of the rotary compressor, thereby maintaining a preset compression ratio and increasing the discharge pressure." (See paragraph 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 60-166785 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] The air compressor described in Patent Document 1 returns part of the exhaust air directly to the air intake side by means of a pipe, so the intake pressure becomes unstable.

[0008] An object of the present invention is to stabilize the suction pressure in an air compressing device.

[0009] Technical solutions to solve problems

[0010] An air compression device as one embodiment of the present invention is characterized in that it includes: a compressor that compresses intake air sucked in from an intake port via an air intake pipe; a heat exchanger that cools the compressed air; an air return pipe that returns a portion of the cooled air to the air intake pipe as return air; and a buffer tank arranged at a specified position on the air return pipe, which at least temporarily stores the return air.

[0011] Effects of the Invention

[0012] According to one embodiment of the present invention, a part or all of the above-mentioned problems can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram showing the structure of the air compressing device of Example 1.

[0014] Figure 2 This is a flow chart of the exhaust air return control of the first embodiment.

[0015] Figure 3It is a graph showing the pressure, flow rate, temperature and density of each part of the air compressing device of Example 1.

[0016] Figure 4 It is a diagram showing the structure of the air compressing device of Example 2.

[0017] Figure 5 This is a flow chart of the exhaust air return control of the second embodiment.

[0018] Figure 6 It is a graph showing the pressure, flow rate, temperature and density of each part of the air compressing device of Example 2.

[0019] Figure 7 It is a diagram showing the structure of the air compressing device of Example 3.

[0020] Figure 8 This is a flow chart of the exhaust air return control of the third embodiment.

[0021] Fig. 9 It is a graph showing the pressure, flow rate, temperature and density of each part of the air compressing device of Example 3.

[0022] Fig.10 This is a flowchart of another exhaust air return control of the first and third embodiments.

[0023] Fig.11 This is a flowchart of another exhaust air return control according to the second embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, embodiments will be described using the drawings.

[0025] Example 1

[0026] Below, according to Figure 1 , Figure 2 , Figure 3 Embodiment 1 of the present invention will be described.

[0027] Figure 1 1 is a diagram showing the structure of the air compressing device of Example 1. The solid line in the diagram shows the flow of air in the air compressing device.

[0028] The dotted line shown in 19 is the package of the air compression device. The external air taken in from the air intake port 1 is compressed by the compressor 7 (the first stage of the air compression device body) through the air filter 2, the check valve 3, and the buffer tank 4. The compressed high-temperature air is cooled by the intercooler (heat exchanger) 11 and further compressed to the target pressure by the compressor 8 (the second stage of the air compression device body).

[0029] The compressed air is cooled by an aftercooler (heat exchanger) 12 and then discharged to the outside from a discharge port 14. A part of the discharged air is returned to the buffer tank 4 via an air return pipe 10. The air return pipe 10 is provided with an orifice 9 and a regulating valve 5.

[0030] The suction pressure is measured by the pressure gauge 6, the intermediate pressure is measured by the pressure gauge 16, the discharge pressure is measured by the pressure gauge 13, and the return air is measured by the pressure gauge 20, and the control panel 15 obtains the values ​​through the control line shown by the single-dot chain line in the figure. The control of the regulating valve 5 is performed by the control panel 15 through the control line. The check valve 17 is a component for preventing the air on the customer side from flowing back when unloading, and 18 is a vent when unloading.

[0031] The air compressing device is provided with a thermometer 21, a thermometer 22, a thermometer 23 and a thermometer 24. The thermometer 21 measures the intake air temperature. The thermometer 22 measures the return air temperature. The thermometer 23 measures the primary discharge temperature. The thermometer 24 measures the discharge temperature.

[0032] The buffer tank 4 is a place where air sucked in from the outside is mixed with a part of the exhaust air and the intake air after the pressure is increased is stored. By temporarily storing the air in the buffer tank 4, the air with stable pressure can be sent to the compressor 7 (first stage). In this way, the flutter of the control valve 5 is prevented. Here, flutter refers to the situation where the control valve 5 is repeatedly opened and closed slightly to finely adjust the return air volume due to the change in the use amount of exhaust air and the change in the exhaust pressure. Due to the flutter, the life of the control valve 5 is shortened, and errors in control occur.

[0033] Furthermore, in order to prevent a part of the exhaust air sent to the buffer tank 4 from flowing back from the air intake port 1 , a check valve 3 is installed at the inlet of the buffer tank 4 .

[0034] The regulating valve 5 is installed in the air return pipe 10 for returning part of the exhaust air, and the return amount to the buffer tank 4 can be adjusted by opening and closing the regulating valve 5. However, if the exhaust air is sent to the regulating valve 5 as it is, the valve is opened and closed while being subjected to high-pressure air, which easily causes the degradation and failure of the regulating valve 5. In order to prevent this, the throttle hole 9 is provided in the air return pipe 10. In addition, the throttle hole 9 also has the function of preventing the regulating valve 5 from opening and closing with excessive frequency due to slight changes in the exhaust pressure when controlling the return flow rate.

[0035] Figure 2 The control flow of the regulating valve 5 of the first embodiment is shown. A series of the regulating valves 5 are controlled by the control panel 15. The control flow is described below.

[0036] After the compressor is started (S201), it is first operated normally with the regulating valve 5 in the closed state (S202). The control panel 15 determines the exhaust air pressure (P d ) is near a preset target pressure (target value) (e.g., within ±10% of the target pressure) (S203). d If the pressure is close to the target pressure (S203: Yes), normal operation S202 is continued, and P is adjusted every predetermined time. d Whether the pressure is close to the target pressure is determined in step S203.

[0037] If the result of determination in S203 is not near the target pressure (S203: No), the regulating valve 5 is adjusted (S204). Specifically, for example, when the target pressure is 90% or less, the regulating valve 5 is opened by a predetermined amount to increase the amount of compressed air returned to the buffer tank 4, and when the target pressure is 110% or more, the regulating valve 5 is closed by a predetermined amount to reduce the amount of compressed air returned to the buffer tank 4.

[0038] Through S204, the compressed air returns to the buffer tank 4, the primary suction air pressure of the compressor 7 rises, and the air pressure (suction pressure P s ) is near a preset target pressure (target value) (for example, within ±10% of the target pressure) (S205).

[0039] If the pressure is not near the target pressure (S205: No), the regulating valve 5 is further adjusted (S204). Specifically, for example, when the pressure is below 90% of the target pressure, the regulating valve 5 is opened by a predetermined amount to increase the amount of compressed air returned to the buffer tank 4, and when the pressure is above 110% of the target pressure, the regulating valve 5 is closed by a predetermined amount to reduce the amount of compressed air returned to the buffer tank 4, thereby adjusting the primary suction air pressure of the compressor 7 to be near the target pressure.

[0040] When the air pressure out of the buffer tank 4 measured by the pressure gauge 6 reaches the preset target value (S205: Yes), the compression ratio πi2 (ratio of intermediate pressure to discharge pressure: Pd / P1) of the compressor 8 (two-stage unit) is measured to determine whether it exceeds the preset reference value (S206). This is because if the compression ratio becomes too high, the compressed air will be overheated and the compressor 8 may be damaged.

[0041] If the compression ratio πi2 exceeds the reference value (S206: No), the intermediate pressure is reduced by opening the regulating valve 5 (S204). If the compression ratio πi2 does not exceed the preset reference value (S206: Yes), the control returns to the normal operation of S202 while maintaining the open / closed state of the regulating valve 5.

[0042] As described above, by opening and closing the regulating valve 5 according to the discharge air pressure Pd, the primary machine intake air pressure Ps, and the compression ratio πi2 of the secondary machine, the compressor 8 can be protected and the intake pressure can be stabilized with a simple structure.

[0043] Next, refer to Fig.10 The control process used to Figure 2 Here, the control panel 15 controls a series of regulating valves 5 .

[0044] and Figure 2 The control process of the regulating valve 5 shown is substantially the same, except that step 206 is omitted. Figure 2 The control flow shown is substantially the same, so the description thereof is omitted.

[0045] exist Figure 2 In the process of setting the opening and closing amount of the regulating valve 5 to a predetermined value, there is a concern that it may take time to determine whether the pressure of each part reaches the target pressure after the regulating valve 5 is opened and closed.

[0046] In particular, when the compression ratio πi2 exceeds the reference value and reaches the alarm value, the air compression device must be stopped to prevent damage to the compressor 8 and to notify an alarm, so high-speed processing is useful. Fig.10 In the control flow, step 206 is omitted to achieve high-speed processing.

[0047] By adopting this aspect, the opening and closing amount of the regulating valve 5 for making the pressure of each part the target pressure can be calculated, and it is not necessary to measure the pressure of each part again after opening and closing the regulating valve 5, thereby speeding up the processing.

[0048] First, an example will be described regarding what amount of compressed air needs to be returned out of the discharge flow rate. Figure 3 The pressure P, volume flow rate Q, mass flow rate G, temperature T, and air density ρ at each position in the package 19 of the air compressing device are shown.

[0049] The primary suction flow rate is the total value of the suction flow rate and the return flow rate, and can be expressed by the following equation (1) based on Boyle-Charles' law.

[0050] Here, as calculation conditions, the intake air pressure Ps=80 [kPa] (atmospheric pressure at an altitude of approximately 2000 m) is set, and the primary intake pressure Ps+r is increased to 100 [kPa] by the return air.

[0051] [Formula 1]

[0052]

[0053] If the equation (1) is converted into an equation for the return flow rate Qr, it can be expressed as the following equation (2).

[0054] [Formula 2]

[0055]

[0056] Here, it is assumed that the suction air pressure is Qs = 80 kPa, the suction temperature is Ts = 303.15 K, and the density is ρs = 0.92 kg / m 3 , the return air pressure is Pr = 780 kPa, the return temperature is Tr = 423.15 K, and the density is ρr = 6.43 kg / m 3 The first-stage suction air pressure is Ps+r=100kPa, and the first-stage suction flow rate is Qs+r=50m 3 / min, suction temperature Ts+r=303.15K, density ρs+r=1.15kg / m 3 , the intake air volume Qs is equal to the intake air volume Qs+r at the end of the first-stage air, then the return flow rate Qr can be calculated as shown in the following formula (3).

[0057] [Formula 3]

[0058]

[0059] Here, the mass flow rate is constant regardless of temperature, so the first-stage machine suction mass flow rate Gs+r is equal to the discharge mass flow rate Gd. It can be seen that the ratio of the return mass flow rate Gr to the first-stage machine suction mass flow rate Gs+r is the flow rate to be returned.

[0060] [Formula 4]

[0061] G s+r =G s +G r =ρ s Q s +ρ r Q r

[0062]

[0063] According to formula (4), the return mass flow Gr needs to be about 20% of the discharge mass flow Gd. Here, the control panel 15 stores a table or a mathematical formula that associates the opening and closing amount of the regulating valve 5 with the return mass flow Gr in a storage unit (not shown), and can calculate the opening and closing amount of the regulating valve 5 required to return the required return mass flow Gr to the buffer tank 4.

[0064] Therefore, in Figure 2 In S204 of FIG. 1 , by opening and closing the regulating valve 5 only by the obtained opening and closing amount, the suction pressure can be stabilized at a higher speed.

[0065] Example 2

[0066] Below, according to Figure 4 , Figure 5 , Figure 6 Embodiment 2 of the present invention will be described.

[0067] Figure 4 1 is a diagram showing the structure of an air compressing device according to Example 2. The solid line in the diagram shows the flow of air in the air compressing device.

[0068] Embodiment 2 is a structure in which a part of the exhaust air is returned between the compressor 7 (primary unit) and the compressor 8 (secondary unit) (between the heat exchanger 11 and the secondary suction port).

[0069] and Figure 1 The air compressing device of the first embodiment shown has different structures in the configuration of the buffer tank 4 and the check valve 3. In addition, in the second embodiment, a pressure sensor 25 and a thermometer 26 are newly configured. The pressure sensor 25 is a sensor for measuring the secondary suction pressure (Pc+r), and is connected to the control unit 15 by a single-dot chain line. The thermometer 26 is a thermometer for measuring the secondary suction air temperature (Tc+r), and is connected to the control unit 15 by a single-dot chain line.

[0070] The outlet of the air from the buffer tank 4 is provided between the compressor 7 and the compressor 8. The buffer tank 4 temporarily stores the return air and sends the return air to the compressor 8. At this time, the check valve 3 is provided on the outlet side of the buffer tank 4 to prevent the air cooled by the heat exchanger 11 from flowing back to the buffer tank 4.

[0071] By temporarily storing air in the buffer tank 4, air with a stable pressure can be fed to the compressor 8. This prevents the control valve 5 from fluttering.

[0072] Other structures and Figure 1 The structure of the air compressing device of the illustrated embodiment 1 is substantially the same, and therefore detailed description thereof will be omitted.

[0073] Figure 5 The control flow of the regulating valve 5 according to the second embodiment is shown.

[0074] and Figure 2 The control process of the regulating valve 5 of the embodiment 1 shown is substantially the same, except that the reference pressure after adjusting the regulating valve 5 is the secondary suction pressure P1+r (refer to S205). Figure 2 The illustrated embodiment 1 is substantially the same, and therefore its description is omitted.

[0075] Next, refer to Fig.11 The control process used to Figure 5 Here, the control panel 15 controls a series of regulating valves 5 .

[0076] and Figure 5 The control process of the regulating valve 5 shown is substantially the same, except that step S206 is omitted. Figure 5 The control flow shown is substantially the same, so the description thereof is omitted.

[0077] exist Figure 5 In the process of setting the opening and closing amount of the regulating valve 5 to a predetermined value, there is a concern that it takes time to determine whether the pressure of each part reaches the target pressure after the regulating valve 5 is opened and closed.

[0078] In particular, when the compression ratio πi2 exceeds the reference value and reaches the alarm value, the air compression device must be stopped to prevent damage to the compressor 8 and to notify an alarm, so high-speed processing is useful. Fig.11 In the control flow, step 206 is omitted to achieve high-speed processing.

[0079] Next, similarly to the first embodiment, an example will be described regarding the extent to which the return within the discharge flow rate is necessary. Figure 6 The pressure P, volume flow rate Q, mass flow rate G, temperature T, and air density ρ at each position are shown. The primary suction flow rate is the total value of the suction flow rate and the return flow rate, and can be expressed by the following equation (5) based on Boyle-Charles' law.

[0080] Here, it is assumed that the intermediate pressure Pc+r is increased from 200 kPa to 250 kPa. According to the calculation result, the return amount is 20% of the discharge. Tc is the outlet temperature of the intercooler (heat exchanger) 11.

[0081] [Formula 5]

[0082]

[0083] As in Example 1, if the formula (5) is converted into a formula for the return flow rate Qr, it can be expressed as the following formula (6), and the return flow rate Qr can be calculated as shown in the following formula (7). According to formula (8), it is necessary to make the return flow rate about 20% of the discharge flow rate, and as in Example 1, it can be used to determine the opening and closing amount of the regulating valve 5 for regulating the return flow rate in S204.

[0084] [Formula 6]

[0085]

[0086] [Formula 7]

[0087]

[0088] [Formula 8]

[0089] G 1+r =G c +G r =ρ c Q 1 +ρ r Q r

[0090]

[0091] Example 3

[0092] Below, according to Figure 7 , Figure 8 , Fig. 9 Embodiment 3 of the present invention will be described.

[0093] Figure 7 1 is a diagram showing the structure of an air compressing device according to a third embodiment, and a solid line shows the flow of air in the air compressing device.

[0094] and Figure 1 The main difference between the air compressing device of the first embodiment shown is that the air compressing device does not have the compressor 8 (two-stage machine) and the heat exchanger 12 of the air compressing device body. Thus, the air compressing device of the third embodiment is a single-stage air compressing device.

[0095] like Figure 7 As shown, external air is sucked in from an air intake port 1, passes through an air filter 2, a check valve 3, and a buffer tank 4, and is compressed by a compressor 7. The compressed high-temperature air is cooled by a heat exchanger 11, and is then discharged from an outlet 14 to the outside.

[0096] Other structures and Figure 1 The structure of the air compressing device of the illustrated embodiment 1 is substantially the same, and therefore the description thereof will be omitted.

[0097] Figure 8 The control flow of the control valve 5 of the third embodiment is shown.

[0098] and Figure 2 The control flow of the regulating valve 5 of the embodiment 1 shown is substantially the same, except that the reference value of the compression ratio is πi1 (refer to S206). πi1 refers to the compression ratio of the first stage, which represents the ratio of the discharge pressure to the suction pressure Pd / P1. The other steps are the same as Figure 2 The illustrated embodiment 1 is substantially the same, and therefore its description is omitted.

[0099] Next, regarding the Figure 8 The control flow and Figure 2 The control flow of is substantially the same, so the description thereof is omitted. Here, the control panel 15 controls a series of regulating valves 5.

[0100] exist Figure 8 In the process of , the opening and closing amount of the regulating valve 5 is set to a predetermined value, and there is a concern that it takes time to determine whether the pressure of each part reaches the target pressure after the regulating valve 5 is opened and closed.

[0101] In particular, when the compression ratio πi1 exceeds the reference value and reaches the alarm value, an alarm is issued to prevent damage to the compressor 8 and the air compression device must be stopped, so high-speed processing is useful. Figure 2 In the control flow, step 206 is omitted to achieve high-speed processing.

[0102] Next, similarly to the first embodiment, an example will be described regarding the extent to which the return within the discharge flow rate is necessary. Fig. 9 The pressure P, volume flow rate Q, mass flow rate G, temperature T, and air density ρ at each position are shown. The primary suction flow rate is the total value of the suction flow rate and the return flow rate, and can be expressed by the following equation (9) based on Boyle-Charles' law.

[0103] Here, as calculation conditions, the intake air pressure Ps=80 [kPa] (atmospheric pressure at an altitude of approximately 2000 m) is set, and the intake pressure Ps+r is increased to 100 [kPa] by the return air. The target discharge pressure Pd=Pr=330 [kPa].

[0104] [Formula 9]

[0105]

[0106] As in Example 1, when the formula (9) is converted into a formula for the return flow rate Qr, it can be expressed as shown in the following formula (10), and the return flow rate Qr can be calculated as shown in the following formula (11). According to formula (12), it is necessary to make the return flow rate about 20% of the discharge flow rate. As in Example 1, it can be used to determine the opening and closing amount of the regulating valve 5 for regulating the return flow rate in S204.

[0107] [Formula 10]

[0108]

[0109] [Formula 11]

[0110]

[0111] [Formula 12]

[0112] G s+r =G s +G r =ρ s Q s +ρ r Q r

[0113]

[0114] As described in the first to third embodiments, regardless of the single-stage machine, the two-stage machine, and the air return position, the target exhaust air pressure can be maintained by returning the exhaust air in an amount calculated to increase the pressure.

[0115] According to the above embodiment, by returning part of the exhaust air to the buffer tank provided on the suction side, the suction pressure can be stably increased, and the flutter of the regulating valve 5 attached to the air return pipe can be prevented.

[0116] Description of Reference Numerals

[0117] 1 Air intake

[0118] 2 Suction filter

[0119] 3 Check valve

[0120] 4 Buffer tank

[0121] 5 Flow control valve

[0122] 6 Suction pressure sensor

[0123] 7Compressor (primary unit)

[0124] 8 compressor (two-stage machine)

[0125] 9 throttle hole (pressure reducing valve)

[0126] 10 Air return piping

[0127] 11 Intercooler

[0128] 12 Aftercooler

[0129] 13 Discharge pressure sensor

[0130] 14 Exhaust port

[0131] 15 Control Panel

[0132] 16 Intermediate pressure sensor

[0133] 17 Check valve

[0134] 18 Purge the piping.

Claims

1. An air compression device, characterized in that: include: A compressor that compresses intake air sucked in from an intake port through an air intake pipe; a heat exchanger for cooling the compressed air; returning a portion of the cooled air as return air to the air return pipe of the air intake pipe; and A buffer tank is provided at a predetermined position of the air return pipe and at least temporarily stores the return air.

2. The air compression device according to claim 1, characterized in that: The buffer tank temporarily stores the intake air sucked from the air intake pipe and the return air, and sends mixed air formed by mixing the intake air and the return air to the compressor.

3. The air compression device according to claim 1, characterized in that: The buffer tank is arranged at the inlet side of the compressor. The heat exchanger is disposed on an outlet side of the compressor.

4. The air compression device according to claim 1, characterized in that: It also includes a regulating valve provided at a predetermined position of the air return pipe and a control panel for controlling the regulating valve. The control panel adjusts the flow rate of the return air to the buffer tank by opening and closing the regulating valve.

5. The air compression device according to claim 1, characterized in that: A throttle hole is further provided at a predetermined position of the air return pipe.

6. The air compression device according to claim 1, characterized in that: The invention further includes a check valve provided at a predetermined position of the air intake pipe to prevent the return air stored in the buffer tank from flowing back to the air intake pipe.

7. An air compression device, characterized in that: include: a first compressor for compressing air sucked from the air intake port; a second compressor for further compressing the air compressed by the first compressor; a first heat exchanger for cooling the air compressed by the first compressor; a second heat exchanger for cooling the air compressed by the second compressor; an air return pipe for returning a portion of the air cooled by the second heat exchanger to an air intake side as return air; and A buffer tank connected to the air return pipe at least temporarily stores the return air.

8. The air compression device according to claim 7, characterized in that: The buffer tank is provided at the inlet side of the first compressor, temporarily stores the intake air and the return air sucked from the air intake port, and sends mixed air formed by mixing the intake air and the return air to the first compressor.

9. The air compression device according to claim 8, characterized in that: A check valve is further provided at the inlet side of the buffer tank, which prevents the return air from flowing back to the air intake side.

10. The air compression device according to claim 7, characterized in that: The buffer tank is disposed between the first compressor and the second compressor, temporarily stores the return air, and sends the return air to the second compressor.

11. The air compression device according to claim 10, characterized in that: A check valve is further provided at the outlet side of the buffer tank to prevent the air cooled by the first heat exchanger from flowing back to the buffer tank.

12. The air compression device according to claim 7, characterized in that: It also includes a regulating valve provided at a predetermined position of the air return pipe and a control panel for controlling the regulating valve. The control panel adjusts the return amount of the return air to the buffer tank by opening and closing the regulating valve.

13. The air compression device according to claim 7, characterized in that: The invention further includes a throttle hole provided at a predetermined position of the air return pipe to prevent the regulating valve from being deteriorated or malfunctioning due to the return air.

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