Research On The Influence Of Ignition Scheme On Ignition Performance Of Combustor

A combustor can be ignited by various ignition modes,such as spark ignition,hot jet ignition,plasma ignition and laser ignition.In order to improve ignition reliability and stability,it is important to understand the law of different ignition modes.In this paper,the ignition performance of two different kinds of ignition modes of spark ignition and laser ignition are numerical simulated and experimental investigated in a square tube with a stabilizer.The main work includes:In spark ignition simulations,the spark is spherical and fixed and it does not change with time.In laser ignitions,the energy deposition model is used.The energy deposition region is a sphere with the ignition position as the center,and the energy is decayed with the sphere radius.By validating the numerical simulation results of two ignition modes with experimental results,the credible numerical simulation method of the ignition process is determined.The effect on ignition performance of spark ignition and laser ignition at different ignition positions,ignition energy,velocity gradient,inlet velocity and fuel distribution are studied and the ignition performances under different schemes are compared.The simulation results of spark ignition show that the increase of ignition energy will speed up the flame propagation and accelerate the developing process of flame.The increase of velocity gradient increases the heat dissipation from the flame to the surrounding,which reduces the local chemical reaction rate and is unfavorable for ignition.High turbulent kinetic energy and turbulence intensity enhance the energy and mass transportation between gas parcels.It can accelerate the heat exchange between the ignited zone and the surrounding mixture in ignition process,which speeds up the spread of flame while increases the heat dissipation.So the ignition process can be accelerated by turbulent kinetic energy and turbulence intensity only in a certain range.The local equivalence peak value and the surrounding distribution near the ignition location influence the flame propagation and development after the kernel forming.The simulation results of laser ignition show that,in different ignition position,ignition energy,velocity gradient,inlet velocity and fuel distribution,the development rules and trends are basically the same,but the size and shape of the flame front are different.The initial kernel formation,flame development and spreading in laser ignition are faster than that in spark ignition under the same conditions.Flame can be ignited in higher turbulence intensity and leaner condition with laser ignition than that with spark ignition.Based on the test system of spark ignition and laser ignition,the influence of kernel development,ignition limits and flame propagation under different ignition parameters including ignition energy and inlet velocity of spark ignition and laser ignition are studied with high speed camera system and ion probe testing system.The experimental results show that the flame develops faster and more violent.Increased ignition energy helps expand ignition limits and the local equivalence ratio near ignition location changes the lean rich ignition limits.The lean ignition limit in laser ignition is lower than that in spark ignition.The flame spreads fastest in the vicinity of stoichiometric ratio both in spark ignition and laser ignition.At the same position behind the ignition location,the flame spreads faster in laser ignition than that in spark ignition.