Experimental And Mechanism Study Of Plasma Ignition Of Low Calorific Value Gas Fuel

With the continuous growth of China’s economic scale,the economic and social demand for energy continues to increase.At the same time,the economic and social transition to sustainable development and efficient use of energy puts forward higher requirements for the adjustment of energy structure.Low calorific value gas fuel such as blast furnace gas has become a hot issue because of its large output and low utilization rate.Because of the low calorific value and many non-combustible components,it is difficult to adopt the conventional ignition method in blast furnace gas turbine.Plasma enhanced ignition can well solve these problems.The hot jets of high temperature,high speed and high activity particles generated during plasma ignition can provide stable,continuous and high-energy ignition energy,improve the characteristics of local combustion flow field,and enhance the ignition process.Its strong jet effect can penetrate the combustion chamber flow field,so that the enhanced ignition effect ACTS on the best ignition position,thus improving the ignition reliability.In this paper,the working characteristics of gas turbine plasma igniter are studied by experimental methods,and the discharge process,hot jet morphology and active particle composition of the igniter in atmospheric environment are analyzed.The ignition and combustion characteristics of low calorific value gaseous fuel were studied by numerical simulation and experiment.The ignition and flame propagation characteristics of a miniature gas turbine combustor are studied numerically.The main conclusions are as follows:（1）The experimental study of air plasma hot jet was carried out and the discharge characteristics of plasma igniter were measured by oscilloscope.High speed camera was used to capture the shape of air plasma hot jet.The active particle components produced during ignition were analyzed by spectrometer.The results show that the plasma igniter USES the low-resistance path formed by the high-pressure breakdown air to conduct capacitor discharge,and in the pulsed discharge process,the air plasma hot jet with high temperature,high speed and high activity particles is generated（2）The combustion mechanism and ignition boundary of low calorific value gas fuel were studied by means of numerical simulation and experiment.The results show that the equivalent ratio and the inlet flow both affect the ignition process.Using the Davis mechanism can better simulate the experimental data of combustion characteristics of low calorific value gas with fewer reaction steps.（3）The numerical simulation method was used to establish the plasma thermal jet numerical model reversely based on the experimental data.The plasma ignition process was coupled to the low-calorie-value gas fuel combustion,and the mechanism of thermal effect,aerodynamic effect and chemical reaction kinetic effect on the enhanced ignition process was studied.The characteristic parameters₀T,₀V and?₀ were used to control the jet temperature,jet length and distribution of active particles respectively,so as to realize the decoupling control of thermal effect,aerodynamic effect and chemical reaction dynamic effect.According to the low calorific value gas combustion characteristic to improve and simplify the prototype chamber,ignition process simulation,found that plasma ignition mechanism is:the low heat value gas in the process of the plasma ignition pneumatic effect directly determines the depth of jet and jet temperature distribution,active particles,which influence the ignition performance,and different ignition position because of the different flow field distribution on the depth of jet impact;The thermal effect directly determines the temperature and energy of the jet,which affects the chemical reaction process in the high temperature zone and intensifies the ignition process.The active particles can directly affect the chemical reaction intensity at the initial fire core,and then change the temperature in the high temperature zone,which can promote the ignition process.