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Technique of the electronic expansion valve


Closed-loop regulation is regulation, regulation is the open-loop feed-forward regulation, although the use of feed-forward regulation could,[link widoczny dla zalogowanych], in theory,[link widoczny dla zalogowanych], be transferred to interference on the barrier parameters are the Ministry of compensation, but it is only to compensate for the major interference, can not take into account other confounding factors. Therefore, feed-forward regulation usually used in conjunction with feedback control, feedforward plus feedback form complex regulation, to improve the tone and color Zhuo Gu a {_ 』Day 1) Figure 7 superheat adjustment transition process (feedforward plus feedback control) 8 store superheat adjustment transition process (feedforward plus feedback regulation of the disposal of interaction and frequency) section quality. Figure 7 is thus obtained by superheating transition curves. As shown in Figure 6, the quality of feedback regulation compared to the maximum superheat overshoot decreased by more than half, settling time is greatly shortened, the dynamic characteristics of control system was improved. 4.3 together with the compressor energy regulation if the electronic expansion valve regulate the flow and adjust the common use of gas compressor House, apparently better able to improve the quality of the superheat adjustment. Figure 8 shows the composite feedforward plus feedback regulation and interaction of the compressor variable speed decadent, the transition curves of superheat of the evaporator back to the mutation load Fung sudden increase in temperature l ~ C, the compressor speed increased by 20, the evaporation temperature reduction of approximately 1.3 ~ C, the maximum superheat overshoot and settling time are greatly reduced. Thus, refrigeration and air conditioning devices in the inverter-type electronic expansion valve in the pre-regulation by law to receive excellent control effect. 5 e-bang bang expansion and thermal expansion valve valve control system of air-conditioning unit in the same comparison, respectively, using thermal expansion valves and electronic expansion valves to control flow, compare their control performance. Reciprocating compressors used in the system, energy can not be adjusted, the electrical power 0.75kWj condenser and evaporator are all cross-flow finned tube heat exchangers. Condenser inlet air temperature. = 20.5. C, air volume Y. = 20m. / Mini evaporator inlet air temperature = lg. 6 ~ C, Feng Y amount of a 9m. , Min. When using thermal expansion valve,[link widoczny dla zalogowanych], air-conditioning system starts, the operating parameters change over time can be seen as shown in Figure g,, N Stone fluid engineering group of 60 started in July 1992 after the evaporator liquid supply has been a substantial change in G , evaporator inlet and outlet temperature and the refrigerant, but also constantly changing although the start four or five minutes for the liquid and superheating a brief period of relative stability,[link widoczny dla zalogowanych], but with the decline in air-conditioned room temperature, evaporator load With the change, for the fluid volume, evaporation temperature and the superheat and long oscillations up. Visible, thermal expansion valve system startup and variable-load performance is not ideal. In addition to the control system of the time lag and the ratio of the factors regulating law,[link widoczny dla zalogowanych], but also because of its superheat setting is given by the spring preload static superheat can only be adjusted at a given load in a better phase-matching relations. Load fluctuations, evaporation temperature, the system instability, decline in air quality, energy consumption increases. Add in1D regulation when asked in Figure l0 electronic expansion valve to switch from boot features electronic expansion valve, the operating parameters change at any time to ask as shown in Figure lO. 5rain start running after the superheat to the basic stable. Another system is stable and running, the evaporator inlet air temperature suddenly rose from 17c 23'c, conditioning systems can also 3rain superheat within the re-stabilized, as shown in Figure children. Electronic expansion valve superheat adjustment of good quality assurance system is stable, energy consumption significantly reduced. As the electronic expansion valve superheat adjustment in respect of the above advantages, the use of cold storage at low temperature can be adjusted to ensure the accuracy of control of superheat in the l. c do not have to worry for the compressor back to the liquid within, do not like the system used as the thermal expansion valve, to prevent the impact of return-air with liquid evaporator must be designed to allow sufficient margin. With the use of thermal expansion valve systems, it can evaporator utilization increased by about 2O%. 20l52i05O cited a hurry 5 thin dust temperature suddenly dirty Figure 11 PID regulator mutation load the system with electronic expansion valve 6 Conclusion dynamic characteristics of electronic expansion valve is the development of refrigeration equipment to adapt to requirements of mechanical and electrical integration of very promising spending components. It is fast response, wide range of flow control can be adjusted according to the default rules of complex movements, access to good quality of superheat adjustment to make the device start-up and much improved dynamic characteristics of load change. Equipment which can ensure the device (evaporator) the use of efficient, stable operation, low energy consumption, temperature control precision. Due to limited space, this article only focuses on the electronic expansion valve superheat control. Electronic expansion valve can not only accurately adjust the superheat, it's compressor with frequency control can also be implemented on a variety of other control devices, which will be discussed in another paper.

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