Patent Application
20220290906
The present application relates to the technical field of refrigeration systems, and more particularly, to a load balancing method for two compressors.
A refrigeration system typically makes use of external energy to transfer heat from a substance (or environment) of a lower temperature to a substance (or environment) of a higher temperature. Compressors are key equipment in a refrigeration system, which are often used to compress a gas of a lower pressure to a gas of a higher pressure, such that the volume of the gas is reduced, and the pressure thereof is increased, thereby converting the external mechanical energy into a pressure energy of the gas. When two compressors are used together in a refrigeration system, it is necessary to maintain load balance between the two compressors to ensure the normal operation of the refrigeration system.
For a refrigeration system that uses two driving devices to respectively drive two compressors, whether there is load balance between the two compressors can be directly determined by monitoring whether the two driving devices have the same rotational speed. When two compressors in a refrigeration system are driven coaxially by one driving device, the structural setting of coaxial driving keeps rotational speeds of the two compressors to be constantly the same. As a result, it is impossible to determine whether there is load balance between these two compressors by directly monitoring rotational speeds. The present application provides a load balancing method for two coaxially driven compressors, which can effectively monitor the load balancing states of the two coaxially driven compressors, thereby preventing the compressors from being damaged by unbalanced loads of the compressors.
The present application provides a load balancing method for two compressors. The two compressors are used in a refrigeration system, comprising a first compressor and a second compressor, wherein the first compressor and the second compressor are driven coaxially by the same driving device, suction sides of the first compressor and the second compressor are both connected with the same evaporator via a pipeline, and exhaust sides of the first compressor and the second compressor are both connected with the same condenser via a pipeline, characterized in that the method comprises the steps of obtaining parameters, determining balance, and controlling start/stop states. Here, the parameters in the step of obtaining parameters are parameters related to the first compressor and the second compressor, the step of determining balance comprises determining whether a balance is achieved between the first compressor and the second compressor according to the obtained parameters related to the first compressor and the second compressor, and the step of controlling start/stop states comprises controlling start/stop states of the first compressor and the second compressor according to whether the balance is achieved.
In the method described above, the suction side of the first compressor and the suction side of the second compressor are respectively provided with a pre-rotation guide vane, the pre-rotation guide vanes are used for regulating the flow rate of a refrigerant flowing into the first compressor and the second compressor, and the imbalance between the first compressor and the second compressor is caused by the pre-rotation guide vanes.
The method described above further comprises obtaining an operating mode, wherein operating modes of the first compressor and the second compressor are obtained according to current load demands of the first compressor and the second compressor, the operating modes comprise a hot gas bypass operating mode, a speed operating mode, and a PRV operating mode, and when the first compressor and the second compressor are running in the speed operating mode and the PRV operating mode, the steps of determining balance and controlling start/stop states are carried out.
In the method described above, the step of obtaining parameters comprises: obtaining the flow rate QA at the suction side of the first compressor and the flow rate QB at the suction side of the second compressor; or obtaining the flow rate QC at the exhaust side of the first compressor and the flow rate QD at the exhaust side of the second compressor; and the step of determining balance comprises: obtaining a flow rate deviation value δQ according to the flow rate QA and the flow rate QB or according to the flow rate QC and the flow rate QD.
In the method described above, the step of obtaining balance further comprises: when the first compressor and the second compressor are running in the PRV operating mode, determining whether the flow rate deviation value δQ is greater than or equal to a first preset value, and if yes, preliminarily determining that the first compressor and the second compressor are in an unbalanced state.
In the method described above, the step of obtaining balance further comprises: after preliminarily determining that the first compressor and the second compressor are in an unbalanced state, continuously monitoring the flow rate QA and the flow rate QB or monitoring the flow rate QC and the flow rate QD within a first preset time, determining whether the flow rate deviation δQ is always greater than or equal to the first preset value according to the monitored flow rate QA and flow rate QB or the monitored flow rate QC and flow rate QD, and if yes, determining that the first compressor and the second compressor are in an unbalanced state.
The method described above further comprises adjusting the compressors, wherein the step of adjusting the compressors comprises adjusting the opening degree of the pre-rotation guide vanes, and the step of adjusting the compressors is carried out after determining that the first compressor and the second compressor are in an unbalanced state; the step of controlling start/stop states comprises: waiting for a second preset time after the step of adjusting the compressors, re-obtaining the flow rate QA and the flow rate QB or re-obtaining the flow rate QC and the flow rate QD after the second preset time elapses, and determining the adjusted flow rate deviation value δQ according to the flow rate QA and the flow rate QB or according to the flow rate QC and the flow rate QD; determining whether the flow rate deviation value δQ is greater than or equal to a second preset value, and if yes, shutting down, wherein the second preset value is greater than the first preset value.
In the method described above, the step of determining balance further comprises: when the first compressor and the second compressor are running in the speed operating mode, determining whether the flow rate deviation δQ is greater than or equal to a third preset value, and if yes, determining that the first compressor and the second compressor are in an unbalanced state; and the step of controlling start/stop states comprises: after determining that the first compressor and the second compressor are in an unbalanced state, obtaining a shutdown time according to the flow rate deviation δQ, and shutting down when the shutdown time elapses.
In the method described above, the step of determining balance further comprises: the flow rate QA at the suction side of the first compressor is measured on a bypass pipeline at one side of the main pipeline between the first compressor and the evaporator, and the flow rate QB at the suction side of the second compressor is measured on a bypass pipeline at one side of the main pipeline between the second compressor and the evaporator; the flow rate QC at the exhaust side of the first compressor is measured on a bypass pipeline at one side of the main pipeline between the first compressor and the condenser, and the flow rate QD at the exhaust side of the second compressor is measured on a bypass pipeline at one side of the main pipeline between the second compressor and the condenser.
In the method described above, the flow rate deviation value δQ=2|QA−QB|/(QA+QB), or the flow rate deviation value δQ=2|QC−QD|/(QC+QD).
In the method described above, the step of obtaining parameters comprises: obtaining the temperature TA at the suction side of the first compressor and the temperature TB at the suction side of the second compressor; and the step of determining balance comprises: determining whether the temperature TA at the suction side of the first compressor or the temperature TB at the suction side of the second compressor is greater than a first preset temperature, and if yes, carrying out the step of controlling start/stop states to shut down the first compressor and the second compressor.
In the method described above, the top of the evaporator and the top of the condenser are in communication with each other through a hot gas bypass pipeline, and a hot gas bypass valve is provided in the hot gas bypass pipeline; the step of determining balance further comprises: after determining that neither the temperature TA at the suction side of the first compressor nor the temperature TB at the suction side of the second compressor is greater than the first preset temperature, obtaining the degree of superheat ΔTA at the suction side of the first compressor and the degree of superheat ΔTB at the suction side of the second compressor; determining whether the degree of superheat ΔTA at the suction side of the first compressor or the degree of superheat ΔTB at the suction side of the second compressor is greater than a second preset temperature, and if yes, determining whether the hot gas bypass valve is open; if determining that the hot gas bypass valve is open, determining whether it is the degree of superheat ΔTA at the suction side of the first compressor or the degree of superheat ΔTB at the suction side of the second compressor that is greater than the second preset temperature; if it is the degree of superheat ΔTA at the suction side of the first compressor that is greater than the second preset temperature, obtaining the degree of superheat ΔTC at the exhaust side of the first compressor, and determining whether the degree of superheat ΔTC at the exhaust side of the first compressor is lower than a third preset temperature; if yes, carrying out the step of controlling start/stop states to shut down the first compressor and the second compressor; if it is the degree of superheat ΔTB at the suction side of the second compressor that is greater than the second preset temperature, obtaining the degree of superheat ΔTD at the exhaust side of the second compressor, and determining whether the degree of superheat ΔTD at the exhaust side of the second compressor is lower than the third preset temperature; if yes, carrying out the step of controlling start/stop states to shut down the first compressor and the second compressor; if determining that the hot gas bypass valve is closed, carrying out the step of controlling start/stop states to shut down the first compressor and the second compressor.
In the method described above, the step of determining balance further comprises: determining whether the rotational speeds of the first compressor and the second compressor are greater than a predetermined rotational speed, and carrying out, only when the determination result is yes, the step of determining whether the temperature TA at the suction side of the first compressor or the temperature TB at the suction side of the second compressor is greater than the first preset temperature.
In the method described above, the degree of superheat ΔTA at the suction side of the first compressor is a temperature difference between the temperature at the suction side of the first compressor and the saturation temperature of the evaporator; and the degree of superheat ΔTB at the suction side of the second compressor is a temperature difference between the temperature at the suction side of the second compressor and the saturation temperature of the evaporator.
In the method described above, the degree of superheat ΔTC at the exhaust side of the first compressor is a temperature difference between the temperature at the exhaust side of the first compressor and the saturation temperature at the exhaust side of the first compressor; and the degree of superheat ΔTD at the suction side of the second compressor is a temperature difference between the temperature at the exhaust side of the second compressor and the saturation temperature at the exhaust side of the second compressor.
The present application creatively adopts three different manners, i.e., exhaust flow rate monitoring, suction flow rate monitoring, and suction temperature monitoring, to monitor load balance of two compressors that are coaxially driven, which can effectively avoid failure of a refrigeration system caused by unbalanced loads of the compressors. In addition, the three load balance monitoring methods adopted by the present application, i.e., exhaust flow rate monitoring, suction flow rate monitoring, and suction temperature monitoring, can also be combined for use in the same monitoring system.
Various implementation manners of the present application will be described below with reference to the accompanying drawings that form a part of this description.
The suction side 110 of the first compressor 101 is connected with the evaporator 103 via a first suction pipeline 121, the suction side 110 of the second compressor 102 is connected with the evaporator 103 via a second suction pipeline 122, the exhaust side 111 of the first compressor 101 is connected with the condenser 104 via a first exhaust pipeline 123, and the exhaust side 111 of the second compressor 102 is connected with the condenser 104 via a second exhaust pipeline 124. The above-described arrangement enables a refrigerant from the evaporator 103 to simultaneously enter the first compressor 101 and the second compressor 102, and after being compressed by the first compressor 101 and the second compressor 102, to be simultaneously discharged to the condenser 104. The suction sides 110 of both the first compressor 101 and the second compressor 102 are respectively provided with a pre-rotation vane (PRV) 105, and by adjusting the opening degrees of the two pre-rotation vanes (PRV) 105, the flow rates of the refrigerant into the first compressor 101 and the second compressor 102 can be respectively controlled. The two pre-rotation vanes (PRV) 105 in the present embodiment are respectively arranged inside the first compressor 101 and the second compressor 102, but for ease of description and illustration, the two pre-rotation vanes (PRV) are illustrated to be independent of the first compressor 101 and the second compressor 102 in the accompanying drawings of the present application. In addition, a hot gas bypass pipeline 125 is further provided between the top of the evaporator 103 and the top of the condenser 104, and a hot gas bypass valve 106 is provided on the hot gas bypass pipeline 125 for adjusting the capacity balance of the refrigeration system.
The load balance monitoring system 100 determines whether there is load balance between the first compressor 101 and the second compressor 102 by monitoring the flow rates at the exhaust sides of the first compressor 101 and the second compressor 102. To realize the monitoring of the flow rates at the exhaust sides 111 of the first compressor 101 and the second compressor 102, the load balance monitoring system 100 provides a first exhaust flow sensor 131 and a second exhaust flow sensor 132 at the exhaust sides 111 of the first compressor 101 and the second compressor 102, respectively. To reduce the impact of the flow sensors on the normal flow of the fluid in the main pipeline of the exhaust pipelines, a bypass pipeline for communicating with a sensor is provided at a side of each of the first exhaust pipeline 123 and the second exhaust pipeline 124 in the embodiments of the present application, wherein the bypass pipeline at the side of the first exhaust pipeline 123 is the first exhaust branch 133, and the first exhaust flow sensor 131 is arranged in the first exhaust branch 133; the bypass pipeline at the side of the second exhaust pipeline 124 is the second exhaust branch 134, and the second exhaust flow sensor 132 is arranged in the second exhaust branch 134. Since the first exhaust branch 133 is in communication with the first exhaust pipeline 123 in a parallel manner and the second exhaust branch 134 is in communication with the second exhaust pipeline 124 in a parallel manner, the difference between the exhaust flow rates of the first exhaust branch 133 and the second exhaust branch 134 can reflect the difference between the exhaust flow rates of the first exhaust pipeline 123 and the second exhaust pipeline 124.
Since the main pipelines of the suction pipelines and the exhaust pipelines have relatively large diameters, the installation of a large flow sensor will impact the suction or exhaust pressure drop, and the installation cost will be high. To prevent a flow sensor from impacting the flow of a refrigerant on the main pipelines and to lower the cost, flow sensors in the load balance monitoring systems according to the first embodiment, the second embodiment, the fourth embodiment, and the fifth embodiment are all provided on bypass pipelines added to one side of the main pipelines. The bypass pipelines are flow pipelines have small diameters and are arranged side by side with the main pipelines that have gas flow rates to be measured. The installation of flow sensors on the bypass pipelines having small diameters not only can detect a difference in flow rates at the suction or exhaust sides of the compressors, but also can minimize the pressure drop on the suction or exhaust pipelines, and in addition, the cost is low. In other embodiments, flow sensors may also be directly provided on the main pipeline of an exhaust pipeline or a suction pipeline if the impact caused by the above-described factors is not considered.
To ensure load balance between two coaxially driven compressors, it is required to simultaneously ensure that the opening degrees of pre-rotation guide vanes (PRV) of the compressors are consistent in command outputs, and the actual opening degrees of the pre-rotation guide vanes (PRV) controlled by actuators are consistent with the received opening degree commands. However, when a transmission failure occurs between an actuator and a pre-rotation guide vane, or when a pre-rotation guide vane fails itself, the two coaxially driven compressors will consequently have unbalanced loads. When the failure is serious, one of the compressors in the refrigeration system cannot operate normally. At this point, the two compressors have very different loads, and the exhaust from the normally operating compressor interferes with the compressor that operates abnormally. Here, the exhaust from the normally operating compressor flows backward, via a condenser, to the compressor that has stopped operations or operates with a failure, and in serious cases, the overall temperature of the compressor that has stopped operations or operates with a failure increases, leading to damage to the compressor that operates abnormally. To avoid damage to a compressor due to unbalanced loads of two coaxially driven compressors, the inventors of the present application have invented three different monitoring manners, i.e., exhaust flow rate monitoring, suction flow rate monitoring, and suction temperature monitoring, and the adoption of any one thereof can effectively determine whether two compressors that are coaxially driven are in a balanced loading state. In addition, on the basis of the three monitoring manners, i.e., exhaust flow rate monitoring, suction flow rate monitoring, and suction temperature monitoring, the present application can adopt a manner that combines the exhaust flow rate monitoring and the suction temperature monitoring or adopt a manner that combines the suction flow rate monitoring and the suction temperature monitoring, which can also determine whether there is load balance between two compressors that are coaxially driven.
As shown in
After the expected current mode of the refrigeration system has been determined in step 701, the method proceeds to step 702 to determine whether the expected current mode is the hot gas bypass operating mode, the PRV operating mode, or the speed operating mode. For the three different operating mode designs, the load balance monitoring system 100 has three different balance determination and control logics.
If a determination result in step 702 is the hot gas bypass operating mode, the method returns to step 702 to re-determine the expected current mode of the refrigeration system, so as to re-enter the control logic 700 for determining the balance of compressors without proceeding to the subsequent balance determination logic. This is because, in the hot gas bypass operating mode, the top of the evaporator 103 and the top of the condenser 104 are in direct communication with each other through the hot gas bypass pipeline 125, and at this moment, the air flow inside the refrigeration system is turbulent. As a result, it is impossible to determine whether the two compressors are balanced by monitoring the flow rates at the exhaust sides of the compressors, and therefore, there is no need to proceed to the subsequent logic for determining the balance of compressors. In addition, since the duration of the hot gas bypass operating mode is typically short, no major impact on the overall operating situation of the refrigeration system even no determination of the balance of two compressors is conducted in this mode.
If a determination result in step 702 is the PRV operating mode, the method returns to step 703. In step 703, the processor 602 of the control device 600 obtains the gas flow rate QC at the exhaust side 111 of the first compressor 101 and the gas flow rate QD at the exhaust side 111 of the second compressor 102 from the input interface 603 via the bus 601. After step 703 is completed, the control device 600 turns the operation to step 704. In step 704, the processor 602 calculates the flow rate deviation percent δQ=2×|QC−QD|/(QC+QD) according to the obtained gas flow rates QC and QD. Subsequently, the method proceeds to step 705.
In step 705, the processor 602 determines whether the flow rate deviation percent δQ is greater than or equal to a first preset value. If no, that is, the flow rate deviation percent δQ is smaller than the first preset value, the processor preliminarily determines that the first compressor and the second compressor are in a balanced state, and at this moment, the processor 602 returns the operation to step 701 to re-enter the control logic 700 for determining the balance of compressors. If yes, that is, the deviation percent δQ is greater than or equal to the first preset value, the processor preliminarily determines that the first compressor and the second compressor are in an unbalanced state and enters step 706, so as to further confirm whether the two compressors are balanced. In the present embodiment, the first preset value is 3%, and in other embodiments, the first preset value may also be other values, for example, any value between 2% and 5%.
In step 706, the processor 602 starts timing so as to continuously obtain the gas flow rate Qc at the exhaust side of the first compressor and the gas flow rate QD at the exhaust side of the second compressor within a first preset time, continuously calculate the flow rate deviation percent δQ according to the obtained gas flow rates QC and QD, and determine whether the flow rate deviation percent δQ is maintained above the first preset value during the first preset time. If a situation occurs during the first preset time that the constantly updated flow rate deviation percent δQ is smaller than the first preset value, it is determined that the first compressor 101 and the second compressor 102 are in a balanced state, and the method returns to step 701 to re-enter the control logic 700 for determining the balance of compressors. If the flow rate deviation percent δQ constantly updated during the first preset time is always maintained above the first preset value, it is further determined that the first compressor 101 and the second compressor 102 are in an unbalanced state, so as to enter the subsequent leveling and observing step. In the present embodiment, the first preset time is 5 min, and in other embodiments, the first preset time may also be other values, for example, any value between 2 min and 10 min.
After determining that the two compressors are in an unbalanced state in step 706, the control device 600 turns the steps to step 707, so as to carry out the subsequent leveling and observing step. In the PRV operating mode, the opening degrees of the pre-rotation vanes at the exhaust sides of the compressors are in a dynamic adjustment state. Therefore, to prevent misjudgment as a result of the opening degree adjustment by the PRVs of the compressors themselves, the opening degrees of the two compressors need to be re-adjusted after it is determined in step 706 that the two compressors are in an unbalanced state, so as to determine whether the adjusted two compressors are still in an unbalanced state. If they are still in an unbalanced state, it is ultimately determined that the two compressors are in an unbalanced state. In step 707, the processor 602 compares the gas flow rate QC at the exhaust side of the first compressor and the gas flow rate QD at the exhaust side of the second compressor that are obtained previously. If the processor 602 determines that QC is smaller than QD, the operation is turned to step 708, so as to increase the opening degree of the pre-rotation guide vane 105 of the first compressor 101; and if QC is greater than QD, the operation is turned to step 709, so as to increase the opening degree of the pre-rotation guide vane 105 at the exhaust side of the second compressor 102. In step 708 and step 709, the opening degrees of the pre-rotation guide vanes 105 of the first compressor 101 and the second compressor 102 are both adjusted by the flow rate deviation percent δQ obtained previously. After obtaining an opening degree compensation being equal to the percent of δQ, the opening degree of the pre-rotation guide vane 105 of the compressor with the lower exhaust flow rate would be easier to obtain an exhaust flow rate that is the same as that of the compressor with the higher exhaust flow, thereby achieving the correction of the unbalanced state of the compressors. It is easy for the compressor with the lower exhaust flow rate to experience surge. Therefore, to avoid safety issues in the refrigeration system caused by the compressor surge, the control device 600 always increases the pre-rotation guide vane 10 of the compressor corresponding to the lower exhaust flow rate, while decreases the opening degree of the pre-rotation guide vane of the compressor with the higher exhaust flow rate. To realize the adjustments of the pre-rotation guide vanes 105, the processor 602 transmits a control signal to the output interface 604 via the bus 601, and the control signal is transmitted, via the output line 614, to the pre-rotation guide vanes 105 of a compressor in need of adjustments (that is, the compressor with the lower exhaust flow rate), such that the pre-rotation guide vanes 105 that receives the signal can increase its opening degree according to the δQ percent.
After step 708 or step 709, the control device 600 turns the operation to step 710. In step 710, the processor 602 starts timing, and when the timing reaches a second preset time, the control device 600 turns the operation to step 711. In step 711, the processor 602 re-obtains the gas flow rate QC at the exhaust side of the first compressor and the gas flow rate QD at the exhaust side of the second compressor from the input interface 603 via the bus 601. After step 711 is completed, the control device 600 turns the operation to step 712. In step 712, the processor 602 re-calculates the flow rate deviation percent δQ according to the re-obtained gas flow rates QC and QD. Subsequently, the control device 600 turns the operation to step 713. In step 713, the processor 602 determines whether the re-calculated flow rate deviation percent δQ is greater than or equal to a second preset value. If yes, it indicates that the two compressors are still in an unbalanced state after the compensation and adjustment in step 708 or step 709, and at this moment, it is ultimately confirmed that the two compressors are unbalanced, and step 720 is carried out to perform the shutdown operation. In step 720, the processor 602 transmits a control signal for shutdown to the output interface 604 via the bus 601, and the control signal is transmitted, via the output line 614, to the driving device 107, such that the driving device 107 that receives the control signal performs the shutdown operation. If it is determined in step 713 that the re-calculated flow rate deviation percent δQ is smaller than the second preset value, it indicates that the two compressors are in a balanced state after the compensation and adjustment in step 708 or step 709. In the present embodiment, the second preset value is 15%, and in other embodiments, the second preset value may also be other values, for example, any value between 10% and 25%. By comparison with the first preset value in step 705, it can be seen that the second preset value is greater than the first preset value. This is because the first preset value is a parameter used to preliminarily determine whether two compressors are balanced and plays an early warning role, while the second preset value is a parameter used to ultimately determine whether two compressors are balanced and plays a role of determination.
In the operating mode determination in step 702, if the determination result is the speed operating mode, the control device 600 turns the operation to step 714 and step 715 sequentially. Step 714 is the same as step 703 in the PRV operating mode, where the processor 602 obtains the gas flow rate QC at the exhaust side of the first compressor and the gas flow rate QD at the exhaust side of the second compressor from the input interface 603 via the bus 601. Step 715 is the same as step 704 in the PRV operating mode, where the processor 602 calculates the flow rate deviation percent δQ=2×|QC−QD|/(QC+QD) according to the obtained gas flow rates QC and QD.
After step 714 and step 715 are completed sequentially, the control device 600 turns the operation to step 716. In step 716, the processor 602 determines whether the calculated flow rate deviation percent δQ is greater than or equal to a third preset value. If no, that is, δQ is smaller than the third preset value, it is determined that the first compressor 101 and the second compressor 102 are in a balanced state, and at this moment, the processor 602 returns the operation to step 701 to re-enter the control logic 700 for determining the balance of compressors. If yes, that is, δQ is greater than or equal to the third preset value, it is determined that the first compressor 101 and the second compressor 102 are in an unbalanced state, and at this moment, the processor 602 returns the operation to step 717. In step 717, the processor 602 obtains a corresponding shutdown time t according to the calculated flow rate deviation value δQ, and then turns to step 718. In step 718, the processor 602 starts timing, and when the timing reaches the shutdown time t, the processor 602 turns the operation to step 720 to control the driving device 107 to stop the operation.
To accurately determine the shutdown time in cooperation with real-time changes of the flow rate deviation, the present application may also make improvements to the above embodiments. In an improved embodiment, in the process of waiting for the shutdown time t in step 718, the processor 602 also continuously obtains, from the input interface 603, the gas flow rate QC at the exhaust side of the first compressor and the gas flow rate QD at the exhaust side of the second compressor that correspond to δQ, and calculates and updates the flow rate deviation percent δQ according to the flow rates QC and QD. When the current actual δQ obtained through continuous update and calculation is greater than the δQ value first obtained in step 715, the processor 602 obtains time Δt that has been waited after the timing starts in step 718, re-starts timing, and re-obtains a shutdown time t′. When the re-started timing reaches the re-obtained shutdown time t′, the processor 602 turns the operation to step 720 to control the driving device 107 for shutdown. Here, the re-obtained shutdown time t′=(t−Δt)×(current actual δQ/(the fourth preset value−the third preset value)).
As shown in
After step 904 is completed, the processor 602 turns the operation to step 905. In step 905, the processor 602 determines whether ΔTA and ΔTB that are obtained from the calculation have a value greater than an early warning temperature. If yes, the processor 602 turns the operation to step 906 for carrying out an alarm operation; if no, the processor 602 turns the operation directly to step 907. In combination with
In step 907, the processor 602 receives from the input interface 603 the rotational speed w from the driving device 107. Subsequently, the processor 602 turns the operation to step 908. In step 908, the processor 602 determines whether the obtained rotational speed w is greater than or equal to a predetermined rotational speed, wherein the predetermined rotational speed is the minimum rotational speed at which a compressor can start a normal operating state. If no, that is, w is slower than the predetermined rotational speed, the processor 602 returns the operation to step 901 to re-enter the determination procedure of the control logic 900; if yes, that is, w is greater than or equal to the predetermined rotational speed, the processor 602 turns the operation to step 909. When the rotational speed w of the driving device 107 is slower than the predetermined rotational speed, the compressor has not started a normal operating state, and at this moment, there is no need to perform the subsequent balance determining control logic 900. Only when the two compressors meet the minimum rotational speed for normal operations, is it necessary to perform the subsequent balance determination. In the present embodiment, the predetermined rotational speed is 3,400 rpm, and in other embodiments, the predetermined rotational speed may also be other values according to the operating state of the refrigeration system, such as any value between 3,200 rpm and 3,800 rpm.
In step 909, the processor 602 determines whether the suction temperature TA of the first compressor and the suction temperature TB of the second compressor obtained in step 903 have a value greater than a first preset temperature. If yes, that is, any value in the values of TA and TB is greater than the first preset temperature, it is determined that the two compressors are in an unbalanced state, and at this moment, the processor 602 turns the operation to step 920 to carry out a shutdown operation. If no, that is, all the values of TA and TB are smaller than or equal to the first preset temperature, it is preliminarily determined that the two compressors are in a balanced state, and at this moment, the processor 602 turns the operation to step 910. When the two compressors are in an unbalanced state, that is, at least one compressor is not in the normal operating state, the high ambient temperature from the condenser 104 is transferred to the suction side 110 through the exhaust side 111 of the abnormally operating compressor. At this moment, the suction side 110 of the abnormally operating compressor is in a state with overly high temperature. Therefore, when a high suction temperature appears at the suction side 110 of a compressor, it can be determined that the two compressors are in an unbalanced state. In the present embodiment, the first preset temperature is 75° C., and in other embodiments, the first preset temperature may also be other values, such as any value between 70° C. and 80° C. The parameter of the first preset temperature value is typically set to be a high temperature value, it is necessary to enter the subsequent control logic to perform further balance determination even if it is preliminarily determined that the two compressors are in a balanced state in step 909.
In step 910, the processor 602 determines whether a temperature greater than a second preset temperature occurs according to the degrees of superheat ΔTA and ΔTB at the suction sides of the first compressor and the second compressor obtained in step 904. If no, that is, the values of the two are all smaller than or equal to the second preset temperature, it is determined that the two compressors are in a balanced state, and at this moment, the processor 602 returns the operation to step 901 to re-enter the control logic 900 for balance determination. If yes, that is, any value in the values of the two is greater than the second preset value, the processor 602 turns the operation to step 911 at this moment. In the present embodiment, the second preset temperature is 15° C., and in other embodiments, the second preset temperature may also be other values, such as any value between 10° C. and 20° C. In the embodiments of the present application, the value of the second preset temperature is greater than the value of the early warning temperature.
In step 911, the processor 602 transmits a signal to the output interface 604 via the bus 601, the signal is transmitted, via the output line 614, to the hot gas bypass valve 106, and upon receiving the signal, the hot gas bypass valve 106 transmits a signal regarding the open/close situation of the hot gas bypass valve 106 to the input interface 603 via the input line 613. Upon receiving the signal, the input interface 603 transmits the signal to the processor 602 via the bus 601, and the processor 602 determines whether the hot gas bypass valve 106 of the current refrigeration system is open. If no, the hot gas bypass valve 106 is in a closed state, and the processor 602 turns the operation to step 920 to carry out a shutdown operation. If yes, the processor 602 turns the operation to step 912 to further confirm whether the two compressors are unbalanced. The top of the condenser 104 and the top of the evaporator 103 are in communication with each other through the hot gas bypass pipeline 125. Therefore, if the hot gas bypass valve 106 is in an open state, the high-temperature gas from the condenser 104 directly flows to the top of the evaporator 103, and the high-temperature gas flowing into the top of the evaporator 103 then flows to the suction sides 110 of the first compressor 101 and the second compressor 102, causing the suction sides 110 of the compressors to have a high temperature. In other words, when the hot gas bypass valve 106 closes the hot gas bypass pipeline 125, it can be determined that the two compressors are in an unbalanced state only according to the high temperature condition at the suction side 110 of a compressor. Under the condition that the hot gas bypass pipeline 125 is in communication, however, the high temperature condition may occur at the suction side 110 of a compressor even if the two compressors are in a balanced state. Therefore, when the hot gas bypass valve 106 is open, the two compressors cannot be determined to be in an unbalanced state only according to the condition that high temperature occurs at the suction side 110 of a compressor. It is necessary to further determine the degree of superheat at the exhaust side 111 of a corresponding compressor having the high temperature situation.
In step 912, the processor 602 determines, according to ΔTA and ΔTB obtained in step 904, whether the degree of superheat at the suction side corresponding to the first compressor 101 is greater than the second preset temperature or the degree of superheat at the suction side corresponding to the second compressor 102 is greater than the second preset temperature. If it is the degree of superheat at the suction side corresponding to the first compressor 101 that is greater than the second preset temperature, the processor 602 turns the operation to step 913. In step 913, the processor 602 receives, from the input interface 603 via the bus 601, the pressure Pc at the exhaust side of the first compressor from the first exhaust pressure sensor 305. Subsequently, the processor 602 turns the operation to step 914. In step 914, the processor 602 obtains, according to the pressure PC at the exhaust side of the first compressor obtained in step 913, an exhaust side saturation temperature TE corresponding thereto. After obtaining the exhaust side saturation temperature TE of the first compressor 101, the processor 602 turns the operation to step 915. In step 915, the processor 602 obtains, from the input interface 603 via the bus 601, the temperature TC at the exhaust side of the first compressor from the first exhaust temperature sensor 303. Subsequently, the processor 602 turns the operation to step 916. In step 916, the processor 602 calculates the degree of superheat ΔTC at the exhaust side of the first compressor, wherein ΔTC=TC−TE, and determines whether ΔTC is lower than a third preset temperature. If yes, the processor 602 determines that the two compressors are in an unbalanced state, and turns the operation to step 920 to carry out a shutdown operation on the driving device 107; if no, the processor 602 determines that the two compressors are in a balanced state, and at this moment, the processor 602 turns the operation to step 901 to re-enter the control logic 900 for balance determination.
If it is the degree of superheat at the suction side corresponding to the second compressor 101 that is greater than the second preset temperature, the processor 602 turns the operation sequentially to steps 917, 918, 919, and 921, where steps 917, 918, 919, and 921 are respectively similar to steps 913, 914, 915, and 916. Step 917 is used to obtain the pressure PD at the exhaust side of the second compressor, step 918 is used to obtain the saturation temperature TE at the exhaust side of the second compressor according to the obtained PD, and step 919 is used to obtain the temperature TD at the exhaust side of the second compressor. Step 921 is used to calculate the degree of superheat ΔTD at the exhaust side of the second compressor according to TE obtained in step 918 and TD obtained in step 919, and determines, through the processor 602, whether ΔTC is lower than the third preset temperature, wherein ΔTD=TD−TF. If yes, the processor 602 determines that the two compressors are in an unbalanced state, and enters step 920 to carry out a shutdown operation on the driving device 107; if no, the processor 602 determines that the two compressors are in a balanced state, and returns to step 901 to re-enter the control logic 900 for balance determination. In other words, in the hot gas bypass mode, it can be determined that the two compressors are in an unbalanced state only when the degree of superheat at the suction side corresponding to a compressor being greater than the second preset temperature and the degree of superheat at the corresponding exhaust side of the same compressor being lower than the third preset temperature are simultaneously satisfied. In the present embodiment, the third preset temperature is 5° C., and in other embodiments, the third preset temperature may also be other values, such as any value between 3° C. and 10° C.
The load balance monitoring system 100 according to the first embodiment as shown in
The load balance monitoring system 400 as shown in
Similar to the load balance monitoring system 400 as shown in
Only some features of the present application are illustrated and described herein, and a variety of improvements and variations may be made by those skilled in the art. Therefore, it should be understood that the appended claims intend to encompass all the above improvements and variations that fall within the scope of the essential spirit of the present application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910939939.7 | Sep 2019 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2020/117844 | 9/25/2020 | WO |
