Research On Thermal Protection And Its Effects In Dynamic Pressure Testing Of Artillery

The dynamic pressure test of artillery is often accompanied by heat transfer.The change of temperature causes great error of pressure sensor and affects the accuracy of pressure measurement.In order to solve this problem,this paper puts forward the method of thermal protection.For the pressure sensor,the measures of smearing grease and sticking plastic film are used.For the pressure sensitive components,the diaphragm pressure sensor and PVDF pressure measuring device are designed.Using the temperature rise theory of single-layer plate,the thermal protection measures designed are analyzed.According to different thermal protection measures and material properties,the variation of temperature rise on the surface and back of oil,plastic and metal materials with material thickness and heat flow time is obtained.The dissipation model of cavityless pipeline and its approximate algorithm are deduced,and the influence of the thickness of silicone grease coating on its amplitude-frequency characteristics is analyzed.It is concluded that the thicker the silicone grease coating is,the lower the resonant frequency is and the narrower the effective bandwidth is.The natural frequency expression of the clamped circular thin plate is derived to estimate the natural frequency of the diaphragm pressure sensor;ANSYS is used to solve the modals of the clamped circular plate and the diaphragm pressure sensor,respectively.It is found that the vibration modes of each order of the two are corresponding and the frequencies are similar,which verifies the feasibility of simplifying the diaphragm pressure sensor into the clamped circular plate in vibration analysis.The acoustic-solid coupling method and virtual mass method for solving the fluid-solid coupling modal are compared.The dry and wet modal analysis of the simplified model of PVDF pressure measuring device is carried out by ANSYS.The results show that the existence of liquid not only reduces the natural frequency of each order mode,but also changes the order of modal vibration modes.The influence of liquid depth and internal pressure on its natural frequency is further studied by simulation.The thermal shock experimental device is designed and the thermal shock experimental study on thermal protection measures is carried out.It is found that the pressure sensor and the pressure sensitive element would respond to the thermal shock,and the thermal protection measures have a certain role in delaying heat transfer and reducing thermal shock response.Two pulse pressure generators,pendulum and piston-hydraulic,are designed,and the dynamic characteristics of the thermal protection measures are experimentally studied.It is found that the dynamic characteristics of the thermal protection measures themselves would have a certain impact on the dynamic pressure measurement,which would limit the full play of the excellent characteristics of the pressure sensor.Therefore,the dynamic characteristics of thermal protection measures should be improved as much as possible in thermal protection design.This paper explores the thermal protection of pressure sensors and pressure sensitive components,and provides a solution to the problem of temperature influence in artillery dynamic pressure test.In the experiment,the pressure and temperature are separated and studied respectively,which has certain reference significance.