高温柱塞阀曲柄滑块机构热变形分析与卡涩故障预测

A positive offset crank-slider mechanism composed of a piston (slider), rocker arm (crank), and connecting rod was used to regulate flow in the plunger valve for a certain altitude test facility. The guide rod was prone to bending, and the piston was prone to deformation when the test airflow temperature was high and the temperature difference was significant, which often led to jam faults, and directly affected the safety of aero-engine testing. So the influences of inlet temperature differences (20 °C to 360 °C) and opening angles (30°, 60°) on the thermal deformation of the mechanism were analyzed through numerical simulation. Aiming to establish a predictive basis for thermal deformation induced sticking faults. The results showed that the thermal deformation of the guide rod and piston increased with the final inlet temperature, and the maximum thermal deformation increased linearly with the inlet temperature difference. The thermal deformation expressions for the cylindrical shaft and cylindrical shell were revised, and a mathematical model for the maximum thermal deformation of the guide rod and piston was established. By combining the theoretical fundamentals of shaft-hole fit clearance, a critical temperature rise mathematical model was developed to predict sticking faults between the guide rod and bushing, as well as between the piston and sleeve. The relative errors of the predicted value of critical temperature rise were 7% and 11%, respectively, when the guide rod was matched with the shaft sleeve, and the piston was matched with the sleeve. Thus these errors met the requirements of allowable deviation in engineering application. Therefore, this critical temperature rise model could be used to predict the thermal deformation-induced jam faults for high-temperature plunger valve mechanisms, helping to provid a theoretical basis for reducing the probability of operational faults in high-temperature plunger valves during high-altitude simulation tests of aero-engines.