Design Of Predictive Control For Waste Heat Driven Jet Refrigeration System On Automotive Air Conditioning

Under the current background of energy conservation and emission reduction,how to increase energy efficiency and reduce environmental pollution has become a research hotspot.As the automobile exhaust emits a large amount of waste heat in the discharge,recycling these low-grade energy is a good way to achieve multi-level energy utilization.The jet refrigeration system,which is constructed by ejector as the core component can use the low-grade heat source as the driving energy source,so it is a good direction to apply the jet refrigeration system in automobile air conditioning.However,the current domestic and foreign experts mostly focus on the mechanism of refrigeration refrigerants,structural design,and the other.There are relatively few studies on control.Based on the above conditions,this paper uses the predictive control method to study the control problem of the jet refrigeration system,through dynamic matrix control method to ensure the high performance.It mainly includes the following work:1.This paper proposes a waste heat driven jet refrigeration system that is used in automobile air conditioning,and analyzes the working cycle of this system based on the ejector characteristics,and then analyzes the feasibility of applying this system to automobiles.In the case of using conventional model data,theoretical analysis show that the vehicle’s cooling capacity is 4229w,while the car’s waste heat emission is 12.33kW.Therefore,the waste heat of the car is sufficient for the working requirements of the jet refrigeration system,and it is feasible to apply it to automobiles.The ejector as the core component is analyzed and studied.Based on obtaining the performance index and working mode of the ejector,the factors affecting the ejector performance are analyzed in a combination of experiments and simulations to obtain the optimal primary flow pressure model.The results show that under the condition that the back pressure is constant,the eject ratio will increase first and then decrease with the gradual increase of primary pressure.And there is a linear relationship between optimal primary pressure and critical back pressure.Therefore,in order to ensure the working performance,it is necessary to control the primary pressure at a position slightly larger than the optimal value to maintain a high eject ratio.Based on the determination of the control target,the circulation pump in this system was modeled,and the transfer function model was obtained.After the control model is determined,the predictive control algorithm is studied,the dynamic matrix control is deduced,and the off-line preparation and on-line calculation process are summarized.The simulation analysis of the control strategy shows that using the predictive control method and the PID control method at the same time,the control performance of predictive control is better.The adjustment time of the PID control is 26s,the overshoot is 3 and control process has a concussion.Predictive control adjustment time is 14s,no overshoot,steady control process,and better control robustness.Add an interference signal to test the anti-jamming ability during the control process and find that the control system has good anti-interference ability.Based on the simulation analysis of the parameters of predictive control,the adjustment direction of the prediction controller is summarized.Finally,combined with equipment selection,the experimental platform of the waste heat driven jet refrigeration system is introduced,and the ejector performance inquiry experiment was carried out,laying the foundation for the next planned refrigeration system control experiment.