Design Of Ultrasonic Focused Igniter And Numerical Simulation Of Its Ignition

Interdisciplinary and knowledge intergration is an important driving factor for the development of combustion science,and it is also a significant feature of the application and development of power ultrasound in new fields.The power ultrasound in the field of acoustics is applied to the ignition and combustion processes in the field of engineering thermophysics,a spatial location non-contact ignition scheme of gas-liquid two-phase flow for flammable mixtures(GLP-FM)based on spherical focused is proposed.This scheme provides a new research direction for combustors such as internal combustion engines to solve the actual engineering bottleneck problems currently faced.This paper takes a sandwich piezoelectric transducer as a prototype,the electromechanical equivalent model of the piezoelectric transducer is constructed based on the equivalent circuit method,and the equivalent circuit and frequency equation of the transducer are derived.According to the target parameters,the geometric size and material selection of the ultrasonic focused igniter are determined,and the characteristic frequency analysis of the ultrasonic focused igniter is performed by using COMSOL Multiphysics to obtain the characteristic frequencies and corresponding mode diagrams of each order,analyze the error with the target parameter,and design the installation plan of the ultrasonic focused igniter.The structural design of the horn is carried out by combining numerical calculation and finite element analysis,it can realize the amplification of the amplitude value of the transmitting end of the ultrasonic focusing igniter and alleviate the disadvantages of stress concentration by adjusting the diameter of the horn and the radius of the transition arc.The finite element analysis method is used to obtain the characteristic frequency,mode shape and amplitude of the transmitting end of the ultrasonic focused igniter with the added horn,and the simulation results are compared with the target parameters.The thermo-acoustic multi-field coupling numerical simulation prediction model is established by using COMSOL Multiphysics to carry out spherical focused ultrasound GLP-FM spatial positioning and fire research,regardless of the specific structure of the constant volume bomb and the ultrasonic focused igniter,analyze the acoustic and thermodynamic characteristics of the GLP-FM focusing area under the ultrasonic heating effect of different parameters(frequency,amplitude),explore the ultrasonic parameters required by the ultrasonic focused igniter to trigger the ignition process of GLP-FM.