JP7282561B2 - LIQUID-COOLED GAS COMPRESSOR AND LIQUID SUPPLY METHOD THEREOF - Google Patents

Description

The present invention relates to a liquid-cooled gas compressor, and to a liquid supply method thereof.

Among gas compressors that suck gas such as air and discharge high-pressure gas such as compressed air using a positive displacement compression mechanism, liquid-cooled gas compressors that supply liquid such as oil to the compression space of the compression mechanism are known. there is

The purpose of the liquid supply is to lubricate the compression mechanism, seal against gas leakage between the compression mechanisms, and cool the gas whose temperature rises due to compression. Conventionally, by supplying a liquid having a lower temperature than the compressed gas during the compression process to the main body of the compressor, the compressed gas has been cooled and the efficiency has been improved.

As a background art of this technical field, there is International Publication No. 2016/117037 (Patent Document 1). Patent Document 1 detects the degree of superheat of refrigerant gas sucked into a compressor, and includes a control device that controls oil temperature adjustment means based on the degree of superheat. of oil is supplied to the screw compressor. As a result, the expansion of the screw rotor is suppressed when the suction superheat is high, and the performance is improved.

WO2016/117037

In Patent Document 1, in an oil-cooled gas compressor, the compressed gas is cooled by supplying oil having a temperature lower than that of the compressed gas during the compression process to a working chamber during compression, thereby improving the efficiency. In this oil supply method, the time from when oil is supplied to the compressor body to when the oil is discharged is limited, and there is a limit to the cooling effect according to the heat exchange time between the compressed gas and the oil. In addition, the intake gas is heated and expanded by the compressed gas leaking from the high pressure side to the low pressure side during compression, so there is a problem that the amount of the intake gas is reduced.

In order to solve the above-mentioned problems, the present invention provides, for example, a liquid-supplying method for a liquid-cooled gas compressor that compresses suction gas sucked by a compressor body and cools the compressed gas with a liquid. The gas discharged from the compressor body is separated into compressed gas and cooling liquid, the separated liquid is cooled, and part of the cooled liquid is supplied to the compressed gas during the compression process of the compressor body. A part of the cooled liquid is cooled to a temperature equal to or lower than the intake gas, and the liquid whose temperature is equal to or lower than the intake gas is supplied to the intake space sucked by the compressor main body.

According to the present invention, the heat exchange time between the compressed gas and the cooling liquid can be made longer than before, further improvement of the cooling effect can be expected, and performance can be improved. In addition, by lowering the temperature of the gas in the suction space heated by the leak in the compressor and improving the gas density, the amount of suction gas increases, and the performance can be improved.

1 is a schematic configuration diagram of an oil-cooled gas compressor in Example 1. FIG. FIG. 5 is a diagram for explaining the suction performance improvement effect in Example 1; 2 is a schematic configuration diagram of an oil-cooled gas compressor in Example 2. FIG. FIG. 11 is a schematic configuration diagram of an oil-cooled gas compressor in Example 3; FIG. 11 is a schematic configuration diagram of an oil-cooled gas compressor in Example 4; 1 is a schematic configuration diagram of a conventional oil-cooled gas compressor; FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, an oil-cooled gas compressor using oil as a coolant will be described as an example.

First, a conventional oil-cooled gas compressor, which is the premise of this embodiment, will be described with reference to FIG. In FIG. 6, the gas sucked into the compressor main body 1 is cooled by oil because the pressure rises and the temperature rises during the compression process. In a conventional oil-cooled gas compressor, a gas mixture of compressed gas and cooling oil is separated by a separator 2, and the oil is cooled by a heat exchanger 3 to a lower temperature than the compressed gas during the compression process, and then compressed again. It is designed to cool the compressed gas by supplying oil during the process. That is, it has an oil supply path for supplying oil cooled in the heat exchanger to the compressed gas during the compression process of the compressor body.

Next, an oil-cooled gas compressor according to this embodiment will be described with reference to FIG. In FIG. 1, the difference between this embodiment and the conventional one is that while the conventional system supplies the oil cooled in the heat exchanger 3 during the compression process, some of the oil is further cooled in the oil cooler 4. and is supplied to the suction space at a lower temperature than the suction gas temperature. That is, a first oil supply path (liquid supply path) for supplying part of the oil cooled in the heat exchanger to the compressed gas during the compression process of the compressor main body, and part of the oil cooled in the heat exchanger. and a second oil supply path (liquid supply path) that supplies the oil cooled by the oil cooler to the suction space where the compressor body sucks the oil. is. The supply to the suction space is performed by spraying, for example. A control device (not shown) controls a part or all of the constituent processing units described above.

Two features of this embodiment are described below. The first point is that by supplying oil to the suction space, heat exchange between the compressed gas and the oil can be performed for a longer period of time than in the conventional oil supply method. The longer the heat exchange time, the more the compressed gas can be cooled, leading to improved performance. The second point is that the temperature in the suction space chamber can be made lower than before by supplying oil having a temperature lower than the temperature of the suction gas. As a result, the sucked gas contracts and the gas density improves, so that the suction performance can be improved.

The suction performance improvement effect obtained by this embodiment will be described below. As an example, the compressed gas is air, and in an oil-cooled gas compressor with a discharge air volume of 10 m ³ /min, 10 L / min of the total oil volume of 50 L / min is sucked in and the gas temperature is lower than 20 ° C. Consider the case of feeding into space. In order to calculate the effect, it is assumed that the oil diffuses uniformly in the suction space and exchanges heat.

FIG. 2 shows the effect of improving the air volume suction performance when the average particle diameter of the oil supplied to the suction space is 0.1 mm and 0.3 mm. The horizontal axis of FIG. 2 represents the difference between the intake gas temperature and the oil temperature. As shown in FIG. 2, the effect of increasing the amount of air with respect to the temperature difference is roughly proportional. As a specific amount of effect, when the temperature difference is 10 ° C, it was a trial calculation that an air amount increase effect of 0.5% with an average particle size of 0.3 mm and 1.9% with an average particle size of 0.1 mm was obtained. .

As described above, according to the present embodiment, the heat exchange time between the compressed gas and the oil can be made longer than in the conventional art, and further improvement of the cooling effect can be expected, thereby improving the performance. In addition, by lowering the temperature of the gas in the suction space heated by the leak in the compressor and improving the gas density, the amount of suction gas can be increased and the performance can be improved.

FIG. 3 shows a schematic configuration diagram of the oil-cooled gas compressor in this embodiment. In FIG. 3 , the difference from Example 1 is that part of the oil cooled by the heat exchanger 3 is cooled not by the oil cooler 4 but by the heat exchanger (evaporator) 5 .

In this embodiment, the heat exchanger 5 is a component of a Rankine cycle composed of an expander 6, a condenser 7 and a pump 8. FIG. That is, the exhaust heat generated when the oil is sucked in and cooled below the gas temperature is used to heat the working fluid of the Rankine cycle in the heat exchanger 5, and the vaporized working fluid drives the expander 6 (for example, a turbine, etc.). generate electricity. The generated power can be used for auxiliary equipment such as the cooling fan in the compressor unit to improve the energy-saving performance of the unit.

Although the Rankine cycle is described as a representative example of the thermal cycle for power generation, it is also possible to use other power generation cycles.

FIG. 4 shows a schematic configuration diagram of the oil-cooled gas compressor in this embodiment. In FIG. 4, the difference from Example 2 is that the oil is not branched after passing through the heat exchanger 3, but is branched after passing through the separator 2 and part of the oil is cooled in the heat exchanger 5. It is a point.

In this embodiment, the amount of oil cooled by the heat exchanger 3 is smaller than in the second embodiment, so the number of revolutions of the cooling fan used in the heat exchanger 3 can be reduced more than before, resulting in energy saving of the compressor. This leads to improved performance. In addition, since more exhaust heat can be recovered than in the second embodiment in the oil supply route to the suction side, more power can be generated.

In the above-described embodiment, when the temperature of the oil is lower than the temperature of the intake gas, there is a concern that more drainage may occur than in the conventional case.

FIG. 5 shows a schematic configuration diagram of the oil-cooled gas compressor in this embodiment. In FIG. 5, in this embodiment, the cooling oil temperature sensor (THY) 9, the suction gas temperature sensor (THX) 10, the oil cooler 4 and the control valve (three-way control valve) 11 are controlled so that the drain accumulates in the pipeline. configured to prevent

Table 1 describes a method of controlling the oil cooler 4 and the control valve 11 by a control device (not shown).

In Table 1, when the compressor is started, the oil cooler 4 is started Δt1 seconds after the compressor is started, thereby preventing the oil temperature from being cooled more than necessary and causing drainage. Further, since the oil is not cooled at the time of start-up, the control valve 11 is set to NO-COM so that the oil is returned to the route for oil supply during the compression process.

When the operating state of the compressor becomes load operation, the oil supply path is changed according to the magnitude relationship between the intake gas temperature THX and the cooling oil temperature THY. When the cooling oil temperature THY is higher than the intake gas temperature THX, the control valve 11 is set to NO-COM, and the cooling oil is returned to the route for oil supply during the compression process. When the cooling oil temperature THY is lower than the intake gas temperature THX, the control valve 11 is set to NC-COM to supply oil to the intake space.

During the unloading operation, the effect of increasing the amount of sucked gas cannot be obtained, so the oil cooler 4 is stopped to prevent the oil from being cooled and drain more than necessary. The control valve 11 is set to NC-COM regardless of the oil temperature to supply oil to the suction space and prevent low-temperature oil from remaining in the pipeline.

When the compressor is stopped, the oil cooler 4 is stopped first, and the electric motor is stopped after Δt2 seconds have passed. The control valve 11 is NC-COM regardless of the oil temperature. By continuing the operation of the motor for Δt2 seconds after the oil cooler 4 is stopped, low-temperature oil is prevented from remaining in the pipeline.

Although the present invention has been specifically described above based on the embodiments, it goes without saying that the present invention is not limited to the above-described embodiments and can be variously modified without departing from the scope of the invention. For example, the above embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. Also, although an oil-cooled gas compressor is used as an example, any liquid other than oil, such as water, may be used as long as the liquid can be used for cooling. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. Further, the control device may be realized by software by interpreting and executing a program for realizing each function, or may be realized by hardware such as an integrated circuit.

1: Compressor body, 2: Separator, 3: Heat exchanger, 4: Oil cooler, 5: Heat exchanger (evaporator), 6: Expander, 7: Condenser, 8: Pump, 9: Cooling oil temperature sensor, 10: intake gas temperature sensor, 11: control valve (three-way control valve)

Claims (6)

A liquid-cooled gas compressor that compresses suction gas sucked by a compressor body and cools the compressed gas with a liquid,
a separator for separating the gas discharged from the compressor main body into compressed gas and cooling liquid;
a heat exchanger that cools the liquid separated by the separator;
a first liquid supply path for supplying part of the liquid cooled in the heat exchanger to the compressed gas during the compression process of the compressor body;
a liquid cooler that cools part of the liquid cooled in the heat exchanger to a temperature equal to or lower than the temperature of the intake gas;
a second liquid supply path that supplies the liquid cooled by the liquid cooler to a suction space that is sucked by the compressor body;
a coolant temperature sensor that measures the coolant temperature of the liquid cooled by the liquid cooler;
a suction gas temperature sensor for measuring the temperature of the suction gas;
A control valve is provided for changing a route for supplying the liquid cooled by the liquid cooler to a suction space sucked by the compressor main body and a route for supplying the liquid to the compressed gas during the compression process of the compressor main body. ,
A liquid-cooled gas compressor, comprising a control device for controlling the control valve according to the magnitude relationship between the cooling liquid temperature and the intake gas temperature. A liquid-cooled gas compressor according to claim 1,
When the temperature of the coolant is higher than the temperature of the intake gas during load operation of the compressor body, the control device causes the control valve to move the liquid cooled by the liquid cooler to the temperature of the compressor body. When the coolant temperature is lower than the temperature of the intake gas, the control valve is switched to a path for supplying liquid to the compressed gas during the compression process, and the liquid cooled by the liquid cooler is sucked by the compressor main body. A liquid-cooled gas compressor, characterized in that it switches to a path that supplies a suction space where the liquid is cooled. A liquid-cooled gas compressor according to claim 1,
The control device stops the operation of the liquid cooler when the compressor body is in an unloaded operation, and operates the control valve to control the liquid from the liquid cooler to the compressor body regardless of the coolant temperature. When the compressor body is stopped, the liquid cooler is stopped first, the electric motor driving the compressor body is stopped after a predetermined time has elapsed, and the control valve is closed. 1. A liquid-cooled gas compressor characterized by switching to a path for supplying liquid from said liquid cooler to a suction space into which liquid is sucked by said compressor body regardless of said coolant temperature. A liquid-supplying method for a liquid-cooled gas compressor for compressing suction gas sucked by a compressor body and cooling the compressed gas with a liquid, comprising:
separating the gas discharged from the compressor body into compressed gas and cooling liquid;
cooling the separated liquid;
A part of the cooled liquid is supplied to the compressed gas in the compression process of the compressor main body,
making a part of the cooled liquid lower than the temperature of the suction gas, and supplying the liquid whose temperature is lower than the suction gas to a suction space sucked by the compressor main body;
Depending on the magnitude relationship between the cooling liquid temperature of the liquid below the temperature of the suction gas and the temperature of the suction gas, supplying the liquid below the temperature of the suction gas to the suction space sucked by the compressor main body; A liquid supply method for a liquid-cooled gas compressor, characterized by switching whether to supply liquid to the compressed gas during the compression process of the compressor main body. A liquid supply method for a liquid-cooled gas compressor according to claim 4,
When the temperature of the cooling liquid is higher than the temperature of the intake gas when the compressor body is in load operation, liquid having a temperature equal to or lower than the temperature of the intake gas is supplied to the compressed gas during the compression process of the compressor body. and when the temperature of the cooling liquid is lower than the temperature of the suction gas, the cooling liquid is switched to the route for supplying the liquid having a temperature equal to or lower than the temperature of the suction gas to the suction space where the compressor body sucks the liquid. A method of supplying liquid to a liquid-cooled gas compressor. A liquid supply method for a liquid-cooled gas compressor according to claim 4,
When the compressor main body is in unloading operation, the operation of lowering the temperature of the suctioned gas or lower is stopped, and the liquid whose temperature is lower than the suctioned gas is sucked by the compressor main body regardless of the temperature of the cooling liquid. When the compressor main body is stopped, the operation of reducing the temperature to below the suction gas temperature is stopped first, and after a predetermined time has elapsed, the electric motor for driving the compressor main body is stopped, and the cooling is performed. A method of supplying liquid to a liquid-cooled gas compressor, characterized by switching to a path for supplying a liquid whose temperature is equal to or lower than that of the suction gas to a suction space sucked by the compressor body regardless of the liquid temperature.

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