Experimental And Simulation Study Of High-pressure Plasma Discharge

Our country’s heavy-duty gas turbine industry continues to develop.Nowadays,heavy-duty gas turbines are widely used in power generation and drive fields.At the same time,many new problems need to be solved.Heavy-duty gas turbines face the problem of flameout and re-ignition under extreme operating conditions,at this time,they are mostly high-pressure and high-speed operating conditions.Compared with normal ignition,high-pressure ignition is more difficult and requires more stringent ignition conditions.The ignition boundary range of extreme ignition conditions is smaller and the ignition success rate is higher.Therefore,the ignition conditions need to be improved.Plasma ignition technology can effectively solve these problems,the plasma generator generates plasma thermal jets through discharge.The high-temperature,high-speed plasma thermal jets contain a large number of active particles,the high-speed plasma thermal jet can improve the flow field characteristics in the combustion chamber,so that the high-temperature ignition energy can reach the inside of the combustion chamber,and the active particles produced by ionization will also promote the chemical reaction process.The plasma ignition method achieves enhanced ignition through thermal effect,aerodynamic effect and chemical kinetic effect,and widens the ignition boundary,improves ignition reliability,and realizes the ignition under high pressure and the flameout and reignition process.In this dissertation,the high-pressure air discharge test bench is designed,and the self-developed plasma igniter is researched on the discharge under high pressure through experimental methods.The characteristics of plasma discharge under different pressures and electrode gaps,the development process of plasma thermal jet and the composition of active particles are analyzed;the discharge characteristics of the plasma generator and the formation process of the plasma thermal jet are studied through the multi-physics coupling method of numerical simulation,constructed a plasma generator model,simulated the development characteristics of the unsteady plasma thermal jet under high pressure,compared the simulation and the development process of the experimental plasma thermal jet,and verified the reliability of the numerical simulation method;the steady-state numerical simulation of air plasma discharge is carried out,the electric field,magnetic field and flow field results are analyzed,and the influence of inlet velocity,voltage,electrode gap,air pressure and electrode material on the discharge result is analyzed.The main conclusions are as follows:(1)The experimental results of high-pressure air discharge show that: as the increase of air pressure,the breakdown voltage of the plasma generator increases,the breakdown current is basically unchanged,the development time of the plasma thermal jet increases,the development length is basically unchanged,and the luminous intensity decreases;as the electrode gap increases,the breakdown voltage of the plasma generator increases,the breakdown current decreases,the development time and development length of the plasma thermal jet increase,and the luminous intensity and active particle composition increase.(2)The unsteady-state numerical simulation results of high-pressure air discharge show that: as the air pressure increases,the development speed of the plasma thermal jet decreases;as the electrode gap increases,the development speed of the plasma thermal jet increases,and the overall temperature decreases;as the discharge time increases,the overall temperature of the plasma thermal jet increases,and the duration increases.The development time of the plasma thermal jet obtained from the experiment and the simulation is basically the same,the development trend in the early stage is basically the same,the development trend after the discharge is different,and the numerical simulation method has certain reliability.(3)The steady-state numerical simulation results of high-pressure air discharge show that:as the inlet velocity increases,the overall velocity of the plasma thermal jet increases and the temperature decreases;as the voltage increases,the input energy increases,and the temperature and velocity of the plasma thermal jet show an upward trend;as the electrode gap increases,electrode breakdown becomes more difficult,the temperature of the plasma thermal jet is decreasing,the resistance of the wall to the air flow decreases,and the velocity of the plasma thermal jet from the nozzle becomes larger;as the air pressure increases,the speed and temperature of the plasma thermal jet show a decreasing trend;there is little difference in the speed and temperature of the plasma thermal jet using different electrode materials,indicating that the electrode material is not the main factor affecting the characteristics of the plasma thermal jet.