Measurement Of Soot Particle Size Of Lminar Diffusion Flames At Elevated Pressure By Laser-induced Incandescence

The soot produced by incomplete combustion of fossil fuels not only poses a great threat to human health,but also affects the entire climate change and accelerates the melting of glaciers.With the energy crisis and environmental problems increasing,it is urgent to study the formation and oxidation mechanism of soot,improve combustion efficiency,and reduce soot emissions.The formation of soot in the flame is an extremely complex process.Knowing the soot particle size can more deeply evaluate and study the degree of hazard of soot,and help to understand the formation mechanism of soot,thereby reducing soot emissions.Based on the existing research,most of which are based on gaseous fuels,and mainly study the soot volume fraction in the flame,the research on the primary particle size distribution of typical liquid fuels has not been deepened.In this paper,Time-Resolved Laser-Induced Incandescence(Ti Re-LII)is used to measure the soot particle size distribution in n-heptane liquid fuel,and to analyze the effect of different fuel flow rate,different carrier gas flow rate and pressure on soot particle size.After some basic parameters are obtained through experiments,the theoretical attenuation curves of the LII signal of different soot particle sizes under different pressure are obtained based on the energy and mass conservation equation using LIISIM,and a set of Laser-Induced Incandescence experiments is constructed and improved.Uses ICCD to capture the two-dimensional distribution of LII signals at different delay time under different operating conditions,and then obtains the LII signal attenuation curve at different positions in the flame,and fits the theoretical curve to obtain the upper and lower limits of the soot particle size and estimates the soot particle size.The experimental results in this paper show that soot particle size at atmospheric pressure is in the range of 15-40 nm,and when the carrier gas flow rate and fuel flow rate are constant,the soot particle size is almost changeless of the flame center point,whether it is horizontal or vertical.While the fuel flow rate is constant and the carrier gas flow rate is increased,the soot distribution of the flame will increase,but the soot particle size will be almost constant,especially near the center point.At the same carrier gas flow rate soot particle size increases with the increase of the fuel flow rate,and the position of the soot particle size distribution also.Soot particle size is the largest near the center point of the flame.It is found that the particle size of the soot in the flame decreases significantly with the increase of pressure.