Numerical Calculation Of Unsteady Temperature Field Based On Ultrasonic Transit Time And Research On Measuring Device

The firing process of artillery lasts for a very short time,which is characterized by instantaneity and instability.Barrel is one of the important parts of artillery,and the influence of ablation wear on barrel performance is one of the key factors that restrict the power of artillery.According to the study of ablation wear mechanism,among the many unfavorable conditions that restrict the life of artillery,the thermal shock of gas is the dominant one,so the heat transfer on the inner wall of artillery during firing is one of the important research objects to control the life and reliability of artillery.Because the interior ballistic process has the characteristics of high temperature,high pressure,electromagnetic interference,high shock wave and rapid change,it is difficult for traditional temperature measurement methods to ensure the accuracy of temperature measurement in this harsh environment.Based on the above considerations,this paper designs a new method for measuring and reconstructing the unsteady temperature field based on ultrasonic transit time.By using the relationship between ultrasonic propagation speed and elastic modulus in materials,combined with the numerical calculation of unsteady heat transfer process,a numerical calculation method for reconstructing the unsteady temperature field is put forward,which provides a calculation method and theoretical basis for solving the unsteady heat transfer problem and solving the temperature field process through ultrasonic transit time.Based on the method of solving temperature field by ultrasonic transit time,two sets of ultrasonic transit time measurement systems and necessary supporting software are designed,and the temperature and ultrasonic echo of nickel-based alloy under transient heat flow are measured,which realizes the calculation of temperature field change in unsteady heat conduction and provides an effective way for non-contact temperature measurement of metal materials.The curves of parameters such as bore pressure,temperature of propellant gas,forced convection heat transfer coefficient between gas and inner wall of barrel with time in the process of 57 mm artillery interior ballistic launch are simulated and calculated by classical interior ballistic equations.By use that gas temperature,convection heat transfer coefficient and the boundary conditions of one-dimensional unsteady heat conduction problem without internal heat source,the change rule of barrel temperature field with time in the course of interior ballistics is solved.On this basis,a simulation experiment method for measuring the temperature of gun barrel theory is designed,and the influence of the accuracy of transit time measured by ultrasonic transit time measurement system and the repetition frequency of ultrasonic pulse on the accuracy of temperature field reconstruction results is accurately analyzed by this method.According to this influence analysis,the recommended performance indexes and minimum performance requirements of the instruments required by this new temperature measurement method are given,which provides theoretical performance requirements for the development and design of barrel temperature field measurement instruments in the subsequent internal ballistic process.