| The Aircraft Engine is the aircraft’s power system,an essential manifestation of a nation’s scientific,industrial,and defence strength.As an essential part of the engine,the fuel nozzle directly impacts the performance and durability of the engines.In the fuel nozzle overhaul process,the nozzle’s atomisation quality is required for testing under multiple pressure points,so the pressure controlling accuracy determines the accuracy of nozzle performance test results.This research investigates the hydraulic system of the nozzle tester based on the technical testing requirements of the A(B)01 type nozzle of an aircraft engine and provides an in-depth discussion of the pressure closed-loop control system at the nozzle inlet.By reviewing relevant domestic and foreign literature and investigating the structural characteristics and working principles for various nozzle testers,this research first identifies a pressure closed-loop control solution based on servo directional valves,pressure sensors,and industrial computer.It then proposes hardware solutions to improve pressure control accuracies,such as grading oil supply pressure and adding auxiliary nozzles and accumulators.Finally,it designs a hydraulic control schematic diagram to calculate and select the main components of the hydraulic system.This research develops a transfer function model for this inlet pressure control system and plots its open-loop transfer function Bode diagram to evaluate the closed-loop system’s stability.To further investigate the dynamic response performance of the pressure control system,it builds a model of the servo valve and the fuel feed module using the software AMESim.On that basis,it creates an AMESim simulation model for the entire nozzle inlet pressure closed-loop control system.In the analysis of the uncorrected system,it is found that the system has problems concerning slow response and inaccuracy in pressure control.This research first introduces conventional PID control,eliminating steady-state errors,but the overshoot caused by the accumulated integral terms will lead to long system adjustment times.Following this,it uses integral separation PID control to alleviate the overshoot caused by the integral term.On this basis,it further improves the integral separation PID based on digital PID,and the corrected system is nearly overshoot-free,with better control performance in terms of dynamic response and steady-state accuracy.Apart from adopting the above control strategy,it also analysed the pressure control performance factors.As the results show,adding an auxiliary nozzle and accumulator at the nozzle inlet can improve steady-state pressure control accuracy.To ensure the project implementation,it studied the influence of the pressure sensor accuracy and the cycle of the controller on the pressure control.According to the above findings,this research designed and manufactured an nozzle performance tester.According to the output data of the pressure sensor at the nozzle inlet onsite,the steady-state pressure control accuracy was within ±0.007 MPa in the pressure range of 0.862～2.068 MPa,and the adjustment time for the pressure entering the steady-state was within 20 seconds,which satisfied the nozzle performance test requirements.The successful implementation of the hydraulic control system has provided valuable theoretical and practical experience for similar tester designs. |
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