Research on optimization design method of actuator parameters with stepless capacity control system for reciprocating compressor

Actuator and hydraulic system parameters have great influence on the performance,safety and reliability of the stepless capacity control system of reciprocating compressor.Due to the diversity and complex relationship of parameters,traditional parameters selected and calculated based on feasibility can’t make the system run efficiently,have limitations,and may have adverse effects on the system or compressor.Therefore,taking the spring stiffness of the actuator and the impact velocity of ejection,the inlet oil pressure of the hydraulic system,and the indicated power deviation of the compressor as objective functions,the multi-parameter and multi-objective optimization research of the actuator and hydraulic system with the stepless capacity control system based on non-dominated sorting genetic algorithm II(NSGA-II)is carried out.Based on fuzzy analytic hierarchy process(FAHP),the optimal solution is selected from the Pareto front,and compared with the traditional design value,the result is better than that obtained by the traditional design method.

A novel flow control scheme for reciprocating compressor based on adaptive predictive PID control

In the process of capacity regulation of reciprocating compressor, the frequent change of inlet temperature and pressure makes the control of exhaust flow unstable, resulting in the high pressure ratio of the intermediate stage. At last the compressor cannot operate safely. To solve the problem, a novel flow control scheme based on inlet temperature and pressure ratio is proposed. In this scheme, the intake model of the cylinder under the capacity regulation condition is established to calculate the load of the first cylinder. Then, the adaptive predictive PID(APPID) controller is designed to control the pressure ratio of other stages, and the grey prediction model is used to predict the pressure output to overcome the system delay. To solve the problem of control parameters tuning, an improved particle swarm optimization(PSO) algorithm is adopted to obtain the optimal control parameters.The effectiveness of the adaptive predictive PID control method is verified by a two-stage compressor model simulation.Finally, the flow control scheme is applied to the actual four-stage air reciprocating compressor flow control system. Although the temperature difference is greater than 15 ℃, the compressor exhaust flow is maintained at the set value and the pressure ratio is also maintained stable. At the same time, the compressor pressure ratio can be quickly adjusted without overshoot. The application result further verifies the feasibility and effectiveness of the scheme.

Research on gas leakage through suction valves of reciprocating compressor under varying load conditions

A research concerning the coupling conditions of gas leakage through suction valves and capacity regulation is performed in an industrial reciprocating compressor.Both internal flow and thermodynamic characteristic are discussed in detail.The results show that the capacity of compressor can be regulated steplessly by controlling suction valve closure moment.And then the quantitative relationship between the capacity load and the closing angle of suction valve is revealed.The capacity load and valve leakage rate show obvious different features in P-V diagrams,which makes it easier to define appropriate features for detecting cracked or broken reciprocating compressor valves under varying load conditions.A set of curves of compression work and discharge gas mass are obtained and a method for rating thermal performance of a compressor is presented using these curves.

A novel none once per revolution blade tip timing based blade vibration parameters identification method

The vibration caused blade High Cycle Fatigue(HCF)is seriously affects the safety operation of turbomachinery especially for aero-engine.Thus,it is crucial important to identify the blade vibration parameters and then evaluate the dynamic stress amplitude.Blade Tip Timing(BTT)method is one of the promising method to solve these problems.While,it need a high resolution Once Per Revolution(OPR)signal which is difficult to get for the aero-engine.Here,a Coupled Vibration Analysis(CVA)method for identifying blade vibration parameters by a none OPR BTT is proposed.The method assumes that every real blade has its own vibration performance at a given speed.Whereby,it can take any blade as the reference blade,and the other blades using the reference blade as the OPR for vibration displacement calculating and further parameter identifying.The proposed method is validated by numerical model.Also,experimental studies are carried out on a straight blade and a twisted three dimensional blade test rig as well as a large industrial axial compressor respectively.The results show that the proposed method can accurately identify the blade synchronous vibration parameters and quantitatively evaluate the mistuning in bladed disks,which lays a foundation for the reliability improvement of aero-engine.