Oil-free bearing liquid supply air-conditioning system and control method therefor

Abstract

Disclosed are an oil-free bearing liquid supply air-conditioning system and a control method therefor. The system includes a compressor, a condenser, an evaporator, a first refrigeration liquid supply path for bearing lubrication from the condenser to the compressor, a second refrigeration liquid supply path for bearing lubrication from the condenser to the compressor, and a communication pipeline arranged between the condenser and the evaporator, the communication pipeline including a first solenoid valve. At least two refrigeration liquid pumps are arranged in the second refrigeration liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps include a main refrigeration liquid pump and at least one standby refrigeration liquid pump.

What is claimed is: 
     
         1 . An oil-free bearing liquid supply air-conditioning system, comprising:
 a compressor comprising a bearing;   a condenser;   an evaporator;   a first refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor;   a second refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor, wherein at least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps comprise a main refrigeration liquid pump and at least one standby refrigeration liquid pump;   a communication pipeline connecting the condenser and the evaporator, the communication pipeline comprising a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline;   a controller configured to:   before the refrigeration system is started, open the first solenoid valve;   in a starting stage, turn on the main refrigeration liquid pump and close the first solenoid valve;   in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upward offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turn off the main refrigeration liquid pump; supply liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication;   in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintain the main refrigeration liquid pump turned on, and supply liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.   
     
     
         2 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 ,
 wherein the first refrigerant liquid supply path for bearing lubrication comprises a first section path, a front section path, a rear section path, and a last section path which are sequentially communicated;   the second refrigerant liquid supply path for bearing lubrication comprises a first section path, a front section path, a rear section path, and a last section path which are sequentially communicated;   the front section path of the first refrigerant liquid supply path for bearing lubrication and the front section path of the second refrigerant liquid supply path for bearing lubrication are arranged in parallel, the main refrigeration fluid pump and the at least one standby refrigeration fluid pump are arranged in parallel in the front section path of the second refrigerant liquid supply path for bearing lubrication, the rear section path of the first refrigerant liquid supply path for bearing lubrication and the rear section path of the second refrigerant liquid supply path for bearing lubrication are the same path, the first section path of the first refrigerant liquid supply path for bearing lubrication and the first section path of the second refrigerant liquid supply path for bearing lubrication are the same path and are communicated with the condenser, and the last section path of the first refrigerant liquid supply path for bearing lubrication and the last section path of the second refrigerant liquid supply path for bearing lubrication are the same path and are communicated with the compressor.   
     
     
         3 . The oil-free bearing liquid supply air-conditioning system according to  claim 2 , wherein the controller is further configured to:
 in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is smaller than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference and a downstream offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downstream offset value of the bearing liquid supply pressure difference and a duration thereof is less than a second set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.   
     
     
         4 . The oil-free bearing liquid supply air-conditioning system according to  claim 2 , wherein the controller is further configured to:
 in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is greater than the second set time, control the refrigeration system to give an alarm and be shut down.   
     
     
         5 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 ,
 wherein the pressure difference of the refrigeration system is a difference between a pressure value of the condenser and a pressure value of the evaporator, and the minimum bearing liquid supply pressure difference is a difference between a preset bearing liquid supply pressure value and a minimum allowable bearing lubrication liquid return or gas return pressure value.   
     
     
         6 . The oil-free bearing liquid supply air-conditioning system according to  claim 2 , further comprising:
 a bearing lubrication liquid return or gas return path from the compressor to the evaporator;   a first pressure sensor connected to the condenser and configured to collect a pressure value of the condenser;   a second pressure sensor connected to the evaporator and configured to collect a pressure value of the evaporator;   a third pressure sensor connected to the last section path of the first refrigerant liquid supply path for bearing lubrication and configured to collect a bearing liquid supply pressure value; and   a fourth pressure sensor connected to the bearing lubrication liquid return or gas return path and configured to collect a bearing lubrication liquid return or gas return pressure value.   
     
     
         7 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , wherein the controller is further configured to:
 in the stable running stage, in a case where the pressure difference of the refrigeration system is less than the difference of the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference, and a duration thereof is greater than the first set time, turn on the main refrigeration liquid pump, and supply the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;   when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is less than the second set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication;   in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is greater than the second set time, control the refrigeration system to give an alarm and be shut down,   wherein the bearing liquid supply pressure difference is a difference between a bearing liquid supply pressure value and a bearing lubrication liquid return or gas return pressure value which are measured in real time.   
     
     
         8 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , further comprising:
 a second solenoid valve arranged on a bearing lubrication liquid return or gas return path from the compressor to the evaporator;   the controller is further configured to:   when the refrigeration system is started, turn on the main refrigeration liquid pump, and close the first solenoid valve; in a case where the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference and a duration thereof is greater than the first set time, run the compressor, and supply the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;   a shutdown stage comprises a normal power-off shutdown stage and an abnormal power-off shutdown stage;   the controller is further configured to:   in the normal power-off shutdown stage:   in a case where the main refrigeration liquid pump is in a turned on state, after the compressor is powered off for a third set time, stop the main refrigeration liquid pump, and open the first solenoid valve; and   in a case where the main refrigeration liquid pump is in the stopped state, forcibly start the main refrigeration liquid pump; and after the compressor is powered off for the third set time, stop the main refrigeration liquid pump, and open the first solenoid valve; and   in the abnormal power-off shutdown stage:   close the second solenoid valve.   
     
     
         9 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , wherein the controller is further configured to:
 when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, turn on the standby refrigeration liquid pump; and   when the standby refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, control the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.   
     
     
         10 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , further comprising:
 an economizer;   a refrigerant supply path extending from the condenser to the economizer, the refrigerant supply path comprising a first electric regulating valve; and   a first liquid level sensor, the first liquid level sensor being configured to monitor a liquid level of the condenser;   the controller is further configured to:   when a value collected by the first liquid level sensor is greater than a minimum allowable liquid level of the condenser, keep an opening degree of the first electric regulating valve; and   when the value collected by the first liquid level sensor is less than or equal to the minimum allowable liquid level of the condenser, adjust the opening degree of the first electric regulating valve to reduce the opening degree of the first electric regulating valve.   
     
     
         11 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , further comprising:
 a subcooler, the subcooler being communicated with the rear section path of the first refrigerant liquid supply path for bearing lubrication and the last section path of the first refrigerant liquid supply path for bearing lubrication;   a heat exchange path from the condenser to the subcooler; the heat exchange path comprising an electronic expansion valve; and   a first temperature sensor, the first temperature sensor being configured to monitor a temperature of the last section path of the first refrigerant liquid supply path for bearing lubrication;   the controller is further configured to:   in a case where a subcooling degree of the refrigerant liquid is greater than a minimum allowable subcooling degree of the liquid supplied to bearing, control the refrigeration system to perform no action; and   in a case where the subcooling degree of the refrigerant liquid is less than or equal to the minimum allowable subcooling degree of the liquid supplied to bearing, adjust the electronic expansion valve to increase an opening degree of the electronic expansion valve;   wherein the subcooling degree of the refrigerant liquid is calculated according to a measured bearing liquid supply pressure value and a bearing liquid supply temperature, and the minimum allowable subcooling degree of the liquid supplied to bearing is a preset value.   
     
     
         12 . The oil-free bearing liquid supply air-conditioning system according to  claim 1 , wherein the minimum allowable bearing liquid supply pressure difference ranges from 0.05 MPa to 0.35 MPa;
 the upward offset value of the bearing liquid supply pressure difference ranges from 0 MPa to 0.35 MPa;   the first set time is 1 min.   
     
     
         13 . The oil-free bearing liquid supply air-conditioning system according to  claim 3 , wherein the downward offset value of the bearing liquid supply pressure difference ranges from 0 MPa to 0.35 Mpa, and the second set time is 30 seconds. 
     
     
         14 . The oil-free bearing liquid supply air-conditioning system according to  claim 8 , wherein the third set time is 3 minutes. 
     
     
         15 . A control method for an oil-free bearing liquid supply air-conditioning system applied to an oil-free bearing liquid supply air-conditioning system, the oil-free bearing liquid supply air-conditioning system comprising:
 a compressor comprising a bearing;   a condenser;   an evaporator;   a first refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor,   a second refrigerant liquid supply path for bearing lubrication extending from the condenser to the compressor, wherein at least two refrigeration liquid pumps are arranged in the second refrigerant liquid supply path for bearing lubrication, the at least two refrigeration liquid pumps are arranged in parallel, and the at least two refrigeration liquid pumps comprise a main refrigeration liquid pump and at least one standby refrigeration liquid pump;   a communication pipeline connecting between the condenser and the evaporator, the communication pipeline comprising a first solenoid valve, the first solenoid valve being configured to control connecting and disconnecting of the communication pipeline; wherein the control method comprises:   before the refrigeration system is started, opening the first solenoid valve;   in a starting stage, turning on the main refrigeration liquid pump and closing the first solenoid valve;   in a stable running stage, in a case where a pressure difference of the refrigeration system is greater than a sum of a minimum allowable bearing liquid supply pressure difference and an upstream offset value of a bearing liquid supply pressure difference, and a duration thereof is greater than a first set time, turning off the main refrigeration liquid pump; supplying liquid to a bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication;   in the stable running stage, in a case where the pressure difference of the refrigeration system is less than or equal to the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, or the pressure difference of the refrigeration system is greater than the sum of the minimum allowable bearing liquid supply pressure difference and the upward offset value of the bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, maintaining the main refrigeration liquid pump turned on; and supplying liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication.   
     
     
         16 . The control method for an oil-free bearing liquid supply air-conditioning system according to  claim 15 , further comprising:
 in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is smaller than the minimum allowable bearing liquid supply pressure difference, and the bearing liquid supply pressure difference is greater than or equal to a difference between the minimum allowable bearing liquid supply pressure difference and a downward offset value of the bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is smaller than the difference between the minimum allowable bearing liquid supply pressure difference and the downstream offset value of the bearing liquid supply pressure difference and a duration thereof is smaller than a second set time, controlling the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.   
     
     
         17 . The control method for an oil-free bearing liquid supply air-conditioning system according to  claim 15 , further comprising:
 in the stable running stage, when the main refrigeration liquid pump is stopped and the liquid is supplied to the bearing of the compressor with the first refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than the difference between the minimum allowable bearing liquid supply pressure difference and the downward offset value of the bearing liquid supply pressure difference and a duration thereof is larger than the second set time, controlling the refrigeration system to give an alarm and be shut down.   
     
     
         18 . The control method for an oil-free bearing liquid supply air-conditioning system according to  claim 15 ,
 wherein the pressure difference of the refrigeration system is a difference between a pressure value of the condenser and a pressure value of the evaporator, and the minimum bearing liquid supply pressure difference is a difference between a preset bearing liquid supply pressure value and a minimum allowable bearing lubrication liquid return or gas return pressure value.   
     
     
         19 . The control method for an oil-free bearing liquid supply air-conditioning system according to  claim 15 , wherein the oil-free bearing liquid supply air-conditioning system comprises a second solenoid valve arranged on a bearing lubrication liquid return or gas return path from the compressor to the evaporator,
 wherein the method further comprises:   when the refrigeration system is started, turning on the main refrigeration liquid pump, and closing the first solenoid valve; in a case where the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference and a duration thereof is greater than the first set time, running the compressor, and supplying the liquid to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication;   wherein a shutdown stage comprises a normal power-off shutdown stage and an abnormal power-off shutdown stage, and the control method further comprises:   in the normal power-off shutdown stage:   in a case where the main refrigeration liquid pump is in a turned on state, after the compressor is powered off for a third set time, stopping the main refrigeration liquid pump, and opening the first solenoid valve; and   in a case where the main refrigeration liquid pump is in the stopped state, forcibly starting the main refrigeration liquid pump; and after the compressor is powered off for the third set time, stopping the main refrigeration liquid pump, and open the first solenoid valve; and   in the abnormal power-off shutdown stage:   closing the second solenoid valve.   
     
     
         20 . The control method for an oil-free bearing liquid supply air-conditioning system according to  claim 15 , further comprising:
 when the main refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigeration liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, turning on the standby refrigeration liquid pump; and   when the standby refrigeration liquid pump is turned on and the liquid is supplied to the bearing of the compressor with the second refrigerant liquid supply path for bearing lubrication, in a case where the bearing liquid supply pressure difference is less than or equal to the minimum allowable bearing liquid supply pressure difference, or the bearing liquid supply pressure difference is greater than the minimum allowable bearing liquid supply pressure difference, and a duration thereof is less than or equal to the first set time, controlling the refrigeration system to give an alarm to hint to check the refrigerant liquid supply path for bearing lubrication.