Numerical Study On Multi-physical Field Of Plasma Ignition Generator

Plasma ignition is a new type of gas turbine ignition technology with the advantages ofdecreased the ignition delay time，enhanced ignition energy and activated combustionproducts．Due to the presence of the high-speed rotation of the combustion chamber airflow，plasma ignition jet length is inadequate and even can’t be stable to ignite the fuel-airmixture．Therefore in this dissertation in-depth research is carried out on a certain type of oilfree plasma igniter，which aims at improving the plasma jet rigidity and enhancing theignition performance in severe environment．The chemical reaction of the air in the plasma ignition generator is theoreticallycalculated and the plasma activation combustion characteristics are studied．Based on thesecondary development of Fluent，plasma ignition field coupling characteristics of the electricfield，magnetic field，flow field and temperature field are calculated，the structure of theigniter also is optimized．Based on the interaction between plasma and the magnetic orelectric field，a magnetic lens and immersion objective lens device is designed to improve theigniter’s performance．It is assumed that high temperature air chemical reaction reachs chemical equilibriumstate，using the standard chemical potential to solve out the reaction equilibrium constant，the10000K temperature high temperature air balance composition is calculated and theactivation particle concentration is analyzed． Fluent software has been developed toinveatigate the interaction between the electromagnetic field and the flow field．RNGturbulence model for the low Reynolds number is considered; the equations also contain theinfluence of radiation， electron mobility heat， Joule heat and self-induced Lorentzforce．Comparative studies on the operating current of the igniter，the intake air flow rate andthe structure size such as the nozzle radius and length，the cathode shrinkage have beencarried on，finally the optimal working parameters and the size of the electrode structure aredesigned．Based on ANSYS electromagnetism module，a magnetic lens device containing amagnetic shielding is designed．The results show that：in the igniter working temperature range，chemical reaction takesplace for the high temperature air in jet region，and the producing oxygen ingredients on the burning of fossil fuels have combustion-supporting effect．Through comparative analysis，the RNG turbulent model that considers low Reynolds number can accurately predictthe flowcharacteristics in igniter internal and jet areas．Higher working current can significantlyimprove the jet rigidity and strength；however it will lead to an increase the of electrodeerosion speed．Good jet rigidity and low electrode temperature could be achieved byincreasing the intake air flow rate．The size of the anode radius plays a decisive role on thespeed of the plasma jet，the smaller the anode radius，the greater the jet velocity．With theincreasing cathode shrinkage， the speed and temperature of plasma jet is alsoimproved．Reducing the anode length can increase the igniter temperature while imposing asmall impact on the speed of the jet．Applying the axial and radial magnetic field at the sametime can significantly improve the performance of the plasma generator．The shieldedmagnetic lens designed by the ANSYS software and the designed electric lens briefly haveachieved the purpose of improving generator’s jet temperature and speed．...