Screw air compressor with refrigeration dryer inlet air pre-cooling function

Abstract

The utility model relates to a screw type air compressor with an air inlet pre-cooling function of a freezing dryer, which is characterized in that the structure of the air compressor comprises a screw type air compressor main machine, the freezing dryer and an air inlet heat exchanger, the screw type air compressor main machine is provided with an air inlet and an air outlet; the air outlet is connected with the refrigeration dryer through a pipeline and is used for reducing the temperature of compressed air at the air outlet; the air inlet is connected with the air inlet heat exchanger, and the air inlet heat exchanger is used for exchanging heat with low-temperature air of the refrigeration dryer, so that the air inlet temperature of the air inlet is reduced, and the air enters the screw type air compressor main machine; according to the scheme, the air compressor has the advantages that an existing air compressor is combined with the freezing type drying machine, the air inlet temperature of the air compressor is reduced by means of the residual cooling capacity generated when the freezing type drying machine dries the compressed air, and therefore the energy consumption is reduced, and the energy-saving effect is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of oil-injected screw air compressors, and in particular to a screw air compressor with dryer intake air precooling. Background Art

[0002] At present, the existing compressed air system is composed of air compressors, cold dryers (cold dryers, full name refrigerated dryers, are indispensable air source processing components in pneumatic systems; they use the principle of refrigeration dehumidification to cool the saturated compressed air from upstream to a certain dew point temperature through heat exchange with the refrigerant, and condense a large amount of liquid water at the same time, which is then separated by a gas-liquid separator and automatically discharged outside the machine, thereby achieving the effect of dehydration and drying), filters and other post-processing equipment. The specific details are as follows: Figure 1 As shown in the figure, it is a typical existing compressed air system, whose structure includes an air compressor a, an air storage tank a1 and a cold dryer a2 connected in sequence, and a filter a3 is respectively arranged between the air storage tank a1 and the cold dryer a2 and at the exhaust port of the cold dryer a2; in this structure, the air compressor a and the cold dryer a2 are independent of each other and controlled separately, and the heat generated by the air compressor a during operation reduces the gas production efficiency of the air compressor, and the excess cold during the operation of the cold dryer is dissipated into the atmosphere and wastes, which increases the energy consumption of the entire compressed air system.

[0003] In addition, there are also solutions on the market for integrated design of air compressor and cold dryer, such as the attached Figure 2 As shown, the design idea is to use the remaining space inside the air compressor a to directly build the cold dryer a2 into the air compressor, but the working process of the air compressor and the cold dryer is the same as the above-mentioned attached Figure 1 The solutions in the example are similar and remain unchanged, and still run independently, so this simple built-in solution still cannot produce energy-saving effects. Utility Model Content

[0004] In view of the above-mentioned deficiencies in the prior art, the present application provides a screw air compressor with refrigerated dryer intake air precooling which combines an existing air compressor with a refrigerated dryer, utilizes the residual cold energy generated when the refrigerated dryer dries the compressed air to lower the intake temperature of the air compressor, thereby reducing energy consumption and achieving energy-saving effects.

[0005] In order to solve the above-mentioned technical problems, the technical solution adopted in the present application is: a screw air compressor with dryer inlet pre-cooling, whose structure includes a screw air compressor main unit, a dryer and an air intake heat exchanger, the screw air compressor main unit is provided with an air inlet and an air outlet, the air outlet is connected to the dryer through a pipeline, and is used to reduce the temperature of the compressed air at the outlet; the air inlet is connected to the air intake heat exchanger, and the air intake heat exchanger is used to exchange heat with the low-temperature gas of the dryer, so that the intake temperature of the air inlet is reduced and enters the screw air compressor main unit.

[0006] By adopting the above scheme, the present application connects the low temperature of the low-temperature gas cooled by the cold dryer to the intake air heat exchanger, thereby lowering the temperature of the air entering the screw air compressor main unit, and the cooling capacity of the intake air heat exchanger is provided by the compressed air in a low-temperature state after being cooled and dehydrated by the cold dryer evaporator. This scheme can effectively utilize the low temperature of the low-temperature gas cooled by the cold dryer to avoid the waste of its cooling capacity, and the temperature of the air entering the screw air compressor main unit is cooled by the heat exchanger before entering the main unit, thereby reducing the energy consumption of the air compressor main unit at the same time; therefore, the adoption of the above scheme of the present application not only utilizes the cooling capacity of the cold dryer but also reduces The energy consumption of the air compressor is reduced. Research shows that a large amount of electrical energy is consumed when the air compressor produces compressed air. Lowering the air intake temperature of the air compressor can reduce the power consumption of the air compressor. For example, a 1°C decrease in the air intake temperature can reduce the energy consumption of the air compressor by about 0.29%. The effective combination of the air compressor and the cold dryer can not only reduce the air intake temperature of the air compressor, but also make full use of the cold energy generated by the cold dryer. On the premise of reducing the moisture content in the compressed air to meet the quality requirements of the compressed air used, the excess cold energy of the cold dryer is used to cool the air inlet of the air compressor, forming a technical solution for a compressed air system containing a cold dryer that can save energy.

[0007] Furthermore, a filter is provided on the air inlet of the main unit of the screw air compressor, and the filter is used for filtering and purifying the air; adopting this solution can ensure the purity of the air entering the main unit and prevent impurities from affecting the operation of the main unit.

[0008] Furthermore, the filter is located at the rear end of the intake heat exchanger, that is, the air first enters the intake heat exchanger to exchange heat with the low-temperature gas cooled by the cold dryer, and then is filtered and purified by the filter before entering the main unit.

[0009] Furthermore, the filter is located at the front end of the air intake heat exchanger, that is, the air is first filtered and purified by the filter, and then enters the air intake heat exchanger to exchange heat with the low-temperature gas cooled by the cold dryer, and then enters the main unit.

[0010] Furthermore, the filter is integrated with the intake heat exchanger; that is, the filter and the intake heat exchanger are combined into a whole, so that the air is filtered while entering the intake heat exchanger, and then enters the main unit of the screw air compressor. This arrangement can further save the space occupied by the equipment.

[0011] Furthermore, filters are provided at the front and rear ends of the air intake heat exchanger; that is, the air is first filtered and purified by the filter, then enters the air intake heat exchanger to exchange heat with the low-temperature gas cooled by the cold dryer, and then enters the filter for secondary filtration before entering the main unit, which further improves the purification effect of the gas entering the main unit of the air compressor.

[0012] Furthermore, the cold dryer includes an evaporator, an air-water separator, a refrigerant compressor (refrigeration compressor) and a condenser; the evaporator is connected to the air outlet of the screw air compressor host through a pipeline, the outlet of the evaporator is connected to the air-water separator, and the low-temperature gas outlet of the air-water separator is connected to the intake heat exchanger; the refrigerant compressor and the condenser are connected to the evaporator; by adopting the above structure, the high-temperature gas coming out of the screw air compressor host can be effectively cooled, thereby separating the moisture in the gas to obtain a drier low-temperature gas (2-10 degrees), the low-temperature gas exchanges heat with the intake heat exchanger, and the intake air entering the screw air compressor host is effectively cooled, thereby reducing the energy consumption of the air compressor host and making full use of the cooling capacity of the low-temperature gas generated by the cold dryer.

[0013] Furthermore, the gas-water separator is provided with an automatic drainer. By adopting the above scheme, when the water separated from the cooled gas reaches a certain volume, it can be automatically discharged without affecting the operation of the gas-water separator.

[0014] Furthermore, a refrigerant filter is provided between the condenser and the evaporator. By adopting this solution, the refrigerant can be effectively filtered to remove impurities, making the refrigerant entering the evaporator purer, thereby ensuring the effective operation of the evaporator.

[0015] Furthermore, a hot gas bypass valve is provided between the condenser and the evaporator. By adopting this solution, the system can be kept to operate normally under a given minimum suction pressure by bypassing the high-pressure refrigerant to the low-pressure side of the system; it can also prevent the compressor from short-circuiting, prevent the compressor from operating under very low suction pressure, and prevent the evaporator from freezing at low load.

[0016] Furthermore, the cold dryer is built into the vacant space inside the screw air compressor; by adopting this method, a cold dryer is placed inside the air compressor by utilizing the space inside the air compressor, and the cold dryer realizes heat exchange connection between its cooling gas and the intake heat exchanger, thereby reducing the intake temperature of the air compressor host to reduce energy consumption.

[0017] Furthermore, the screw air compressor includes an oil-injected screw air compressor or an oil-free screw air compressor; that is, the solution of the present application of utilizing the cooling capacity of the installed cold dryer to reduce the inlet temperature of the air compressor can be applied to multiple types of screw air compressors, not limited to oil-injected screw compressors. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a compressed air system in the prior art.

[0019] Figure 2 The present invention is a schematic diagram of the structure of an air compressor and a cold dryer integrated into one body in the prior art.

[0020] As shown in the figure: a. Air compressor, a1 air storage tank, a2. Cold dryer, a3. Filter.

[0021] Figure 3 This is a schematic structural diagram of a screw air compressor with dryer inlet air precooling according to Example 1 of the present application.

[0022] Figure 4 This is a schematic structural diagram of a screw air compressor with dryer inlet air precooling according to Example 2 of the present application.

[0023] Figure 5 This is a schematic structural diagram of a screw air compressor with dryer inlet air precooling according to Example 3 of the present application.

[0024] Figure 6 This is a schematic structural diagram of a screw air compressor with dryer inlet air precooling according to Example 4 of the present application.

[0025] As shown in the attached figure: 1. Screw air compressor main unit, 101. Air inlet, 102. Air outlet, 103. Oil and gas barrel, 104. Oil and gas separator, 2. Cold dryer, 201. Evaporator, 202. Gas-water separator, 203. Refrigerant compressor (refrigeration compressor), 204. Condenser, 205. Expansion valve, 206. Capillary tube, 207. Automatic drainer, 3. Inlet heat exchanger, 4. Filter, 5. Refrigerant filter, 6. Hot gas bypass valve, 7. Cooler, 8. Temperature sensor, 9. Pressure sensor, 10. Motor. DETAILED DESCRIPTION

[0026] The following will combine the embodiments and drawings to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only preferred embodiments, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention;

[0027] It should also be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be another intermediate component, fixed through the intermediate component. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0028] As attached Figure 3-6 As shown, a screw air compressor with dryer inlet air precooling of the present application has a structure including a screw air compressor main unit 1, a dryer 2 and an air intake heat exchanger 3 (such as a commercially available air-to-air heat exchanger that can realize temperature heat exchange of two gases at different temperatures), and the screw air compressor main unit 1 is provided with an air inlet 101 and an air outlet 102, and the air outlet 102 is connected to the dryer 2 through a pipeline and is used to reduce the temperature of the compressed air at the air outlet 102; the air inlet 101 is connected to the air intake heat exchanger 3, and the air intake heat exchanger 3 is used to exchange heat with the low-temperature gas of the dryer 2, so that the intake temperature of the air inlet 101 is reduced and enters the screw air compressor main unit 1.

[0029] By adopting the above scheme, the present application connects the low temperature of the low-temperature gas cooled by the cold dryer to the intake air heat exchanger, thereby lowering the temperature of the air entering the screw air compressor main unit, and the cooling capacity of the intake air heat exchanger is provided by the compressed air in a low-temperature state after being cooled and dehydrated by the cold dryer evaporator. This scheme can effectively utilize the low temperature of the low-temperature gas cooled by the cold dryer to avoid the waste of its cooling capacity, and the temperature of the air entering the screw air compressor main unit is cooled by the heat exchanger before entering the main unit, thereby reducing the energy consumption of the air compressor main unit at the same time; therefore, the adoption of the above scheme of the present application not only utilizes the cooling capacity of the cold dryer but also reduces The energy consumption of the air compressor is reduced. Research shows that a large amount of electrical energy is consumed when the air compressor produces compressed air. Lowering the air intake temperature of the air compressor can reduce the power consumption of the air compressor. For example, a 1°C decrease in the air intake temperature can reduce the energy consumption of the air compressor by about 0.29%. The effective combination of the air compressor and the cold dryer can not only reduce the air intake temperature of the air compressor, but also make full use of the cold energy generated by the cold dryer. On the premise of reducing the moisture content in the compressed air to meet the quality requirements of the compressed air used, the excess cold energy of the cold dryer is used to cool the air inlet of the air compressor, forming a technical solution for a compressed air system containing a cold dryer that can save energy.

[0030] As attached Figure 3-6 As shown, a filter 4 is also provided on the air inlet 101 of the main unit 1 of the screw air compressor described in the present application, and the filter 4 is used for filtering and purifying the air; adopting this solution can ensure the purity of the air entering the main unit and prevent impurities from affecting the operation of the main unit.

[0031] As Example 1, Figure 3 As shown, the filter 4 described in this example is located at the rear end of the intake heat exchanger 3, that is, the air first enters the intake heat exchanger 3 to exchange heat with the low-temperature gas cooled by the cold dryer 2 (absorbing the cold energy of the low-temperature gas to lower its own temperature), and then is filtered and purified by the filter before entering the main unit of the screw air compressor.

[0032] As Example 2, as shown in the attached Figure 4 As shown, the filter 4 described in this example is located at the front end of the intake heat exchanger 3, that is, the air is first filtered and purified by the filter, and then enters the intake heat exchanger to exchange heat with the low-temperature gas cooled by the dryer, and then enters the main unit.

[0033] As Example 3, Figure 5As shown, the filter 4 described in this example is integrated with the intake heat exchanger 3; that is, the filter and the intake heat exchanger are combined into a whole, so that the air is purified and filtered by the filter while entering the intake heat exchanger for heat exchange and cooling, and then enters the main unit of the screw air compressor. This arrangement can integrate the filter and the intake heat exchanger together and further save the space occupied by the equipment.

[0034] As Example 4, Figure 6 As shown, the front and rear ends of the intake heat exchanger 3 described in this example are provided with filters 4; that is, the air is first filtered and purified by the filter, and then enters the intake heat exchanger to exchange heat with the low-temperature gas cooled by the cold dryer, and then enters the filter for secondary filtration before entering the main unit, which further improves the purification effect of the gas entering the main unit of the air compressor.

[0035] As attached Figure 3-6As shown, the cold dryer 2 described in the present application includes an evaporator 201, a gas-water separator 202, a refrigerant compressor 203 (refrigeration compressor) and a condenser 204; the evaporator 201 is connected to the air outlet 102 of the screw air compressor host 1 through a pipeline, the outlet of the evaporator 201 is connected to the gas-water separator 202 (the high-temperature gas from the host is cooled through the evaporator, and the water and low-temperature gas are separated and enter the gas-water separator), and the low-temperature gas outlet of the gas-water separator 202 is connected to the The air intake heat exchanger 3 is connected; the refrigerant compressor 203 and the condenser 204 are connected to the evaporator 201; the above structure can effectively cool the high-temperature gas coming out of the screw air compressor host, so as to separate the moisture in the gas and obtain a drier low-temperature gas (2-10 degrees), which exchanges heat with the air intake heat exchanger and effectively cools the air intake entering the screw air compressor host, thereby reducing the energy consumption of the air compressor host and making full use of the cold capacity of the low-temperature gas generated by the cold dryer; in the cold dryer The evaporator is the main heat exchange component of the cold dryer. The compressed air is forced to cool in the evaporator, and most of the water vapor is cooled and condensed into liquid water, thereby drying the compressed air. The low-pressure refrigerant liquid undergoes a phase change in the evaporator and becomes low-pressure refrigerant steam. During the phase change, it absorbs the surrounding heat, thereby cooling the compressed air. The gas-water separator collects the liquid water from the evaporator and outputs the low-temperature dry gas. The refrigerant compressor is the core of the refrigeration system, which inputs the refrigerant into the evaporator for cooling to realize the circulation of the refrigerant. ring; the function of the condenser is to cool the high-pressure, superheated refrigerant vapor discharged from the refrigerant compressor into a liquid refrigerant, and its heat is taken away by cooling water or cooling air, so that the refrigeration process can be carried out continuously; in addition, the cold dryer of the present application also includes an expansion valve, that is, a thermal expansion valve (capillary tube), etc., which is a throttling mechanism of the refrigeration system. In the cold dryer, the supply of evaporator refrigerant and its regulation are realized by the throttling mechanism. The throttling mechanism allows the refrigeration to enter the evaporator from the high-temperature and high-pressure liquid. The specific positions of the expansion valve 205 and the capillary tube 206 are as shown in the attached figure. Figure 3-6 As shown, on the output pipe of the condenser.

[0036] As attached Figure 3-6 As shown, the gas-water separator 202 described in the present application is provided with an automatic drainer 207 (commercially available products are sufficient). By adopting the above scheme, when the water separated from the cooled gas reaches a certain volume, it can be automatically discharged without affecting the operation of the gas-water separator.

[0037] As attached Figure 3-6As shown, a refrigerant filter 5 is also provided between the condenser 204 and the evaporator 201 described in the present application. Specifically, the refrigerant filter is arranged on the condenser output pipeline and is located at the front end of the expansion valve. By adopting this solution, the refrigerant can be effectively filtered to remove impurities, so that the refrigerant entering the evaporator is purer, thereby ensuring the effective operation of the evaporator.

[0038] As attached Figure 3-6 As shown, a hot gas bypass valve 6 is also provided between the condenser 204 and the evaporator 201 described in the present application; the specific hot gas bypass valve is connected in parallel with the refrigerant filter and is respectively arranged at the input and output ends of the condenser; by adopting this scheme, the system can be kept to work normally under a given minimum suction pressure by bypassing the high-pressure refrigerant to the low-pressure side of the system; and it can also prevent the compressor from short-circuiting and operating at a very low suction pressure, and prevent the evaporator from freezing at low load.

[0039] As an example, the cold dryer 1 described in the present application is built into the empty space inside the screw air compressor (a general screw air compressor has a box structure, and the various components of the air compressor are assembled in the box, and there is an empty space in the box, and the cold dryer is arranged in it to realize the integration of space); adopting this method, that is, placing a cold dryer in the remaining space inside the air compressor, and according to the attached Figure 3-6 The scheme shown connects the cold dryer with the intake air heat exchanger through the cooling of the low-temperature gas, thereby reducing the intake air temperature of the air compressor host to reduce energy consumption; the traditional common cold dryer is the cold dryer, and the air compressor is the air compressor, but the cold dryer is installed inside the air compressor, and the two still operate independently, and no scheme for utilizing cold capacity is adopted. Moreover, since the existing scheme is just a simple built-in assembly, it has an adverse effect on the operation of the air compressor and the cold dryer. For example, since the cold dryer is built into the air compressor, the distance between the two is closer. The heat generated during the operation of the air compressor increases the power consumption of the cold dryer. The heat generated during the operation of the cold dryer will also increase the operating temperature of the air compressor and reduce energy efficiency. The present application also arranges a cooler 7 between the air compressor host and the cold dryer (see attached for details). Figure 3-6 ), can overcome the above shortcomings and can also make full use of the cooling capacity.

[0040] The most critical innovation of this application is to exchange the cold energy of the low-temperature gas coming out of the cold dryer with the gas entering the compressor host through a heat exchanger, thereby reducing the temperature of the gas entering the compressor host; the air compressor consumes a lot of electricity when it works to produce compressed air, and lowering the air compressor inlet temperature can reduce the power consumption of the air compressor, and the energy consumption of the air compressor can be reduced by about 0.29% for every 1°C reduction in the air intake temperature of the host; this application cleverly uses the cold dryer to dry the compressed air after it comes out of the air compressor to reduce the moisture content in the compressed air to meet the quality requirements of the compressed air used, and the excess cold energy generated by the cold dryer in this process is used for the air compressor inlet The air is cooled to reduce the energy consumption of the compressor; the present application can place the cold dryer inside the space of the air compressor to obtain an air compressor with a cold dryer function, and use the residual cold energy generated by the cold dryer to cool the air intake of the air compressor to reduce the air intake temperature of the air compressor, thereby achieving the purpose of reducing the power consumption of the air compressor, and the compressed air generated by the air compressor is processed by the heat exchanger and comes out as processed dry compressed air, which does not require additional processing and can be directly used in industrial terminals; the present application makes full use of the internal space of the air compressor, reduces the floor space of the cold dryer, so that the area of ​​the air compressor room can be reduced, the installation is simpler, and the corresponding engineering costs will also be reduced.

[0041] It should be noted that the screw air compressor of the present application may be an oil-injected screw compressor, as shown in the attached Figure 3-6 As shown, a motor is arranged on it to drive the compressor host to generate compressed gas; and an oil pipeline is connected to the host to transport oil to the host to ensure the stability of the host operation; it can also be an oil-free screw air compressor, that is, the solution of using the cooling capacity of the set cold dryer to reduce the inlet temperature of the air compressor in the present application can be applied to many types of screw air compressors, not limited to oil-injected screw compressors. In addition, when it is an oil-injected screw compressor, an oil-gas barrel 103, an oil-gas separator 104, a cooler 7, and various safety valves, check valves, pressure differential switches, temperature control valves, pressure maintaining valves, solenoid valves, pressure gauges, etc. are also arranged on its host (the host is driven to run by a motor 10), and a temperature sensor 8 and a pressure sensor 9 are also arranged; matching control lines, air lines, oil lines, etc. are arranged according to the needs of this application, and there are corresponding arrangements in the accompanying drawings, such as in the accompanying drawings To control the pipeline, For gas pipelines, It is an oil pipeline, and the arrow indicates the flow direction of the medium. Without special explanation, the above-mentioned parts can be combined with corresponding positions using corresponding commercially available parts. For example, parts that can be used in the operation process of conventional screw compressors in the industry will not be described in detail here.

Claims

1. A screw air compressor with dryer inlet air precooling, characterized in that: The structure of the air compressor includes a screw air compressor main unit, a cold dryer and an air intake heat exchanger. The screw air compressor main unit is provided with an air inlet and an air outlet. The air outlet is connected to the cold dryer through a pipeline and is used to reduce the temperature of the compressed air at the air outlet; the air inlet is connected to the air intake heat exchanger, and the air intake heat exchanger is used to exchange heat with the low-temperature gas of the cold dryer so as to reduce the intake temperature of the air at the air inlet and enter the screw air compressor main unit.

2. The screw air compressor with dryer inlet air precooling according to claim 1, characterized in that: A filter is also provided on the air inlet of the main engine of the screw air compressor, and the filter is used for filtering and purifying the air.

3. The screw air compressor with dryer inlet air precooling according to claim 2, characterized in that: The filter is located at the rear end of the intake heat exchanger.

4. The screw air compressor with dryer inlet air precooling according to claim 2, characterized in that: The filter is located at the front end of the intake heat exchanger.

5. The screw air compressor with dryer inlet air precooling according to claim 2, characterized in that: The filter is integrally arranged with the air intake heat exchanger.

6. The screw air compressor with dryer inlet air precooling according to claim 2, characterized in that: Filters are arranged at the front end and the rear end of the air intake heat exchanger.

7. The screw air compressor with dryer inlet air precooling according to claim 1, characterized in that: The cold dryer includes an evaporator, an air-water separator, a refrigerant compressor and a condenser; the evaporator is connected to the air outlet of the screw air compressor host through a pipeline, the outlet of the evaporator is connected to the air-water separator, and the low-temperature gas outlet of the air-water separator is connected to the air intake heat exchanger; the refrigerant compressor and condenser are connected to the evaporator.

8. The screw air compressor with dryer inlet air precooling according to claim 7, characterized in that: The gas-water separator is provided with an automatic drainer; a refrigerant filter is also provided between the condenser and the evaporator; and a hot gas bypass valve is also provided between the condenser and the evaporator.

9. The screw air compressor with dryer inlet air precooling according to claim 7, characterized in that: The cold dryer is built into the vacant space inside the screw air compressor.

10. The screw air compressor with dryer inlet air precooling according to claim 1, characterized in that: The screw air compressor includes an oil-injected screw air compressor or an oil-free screw air compressor.

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