A Studv Of Laminar Burning Velocity And Turbulent Flame Structure Of Oxygentated Bio-fuel

Large scale application of biofuels entered the world stage because of the fossil fuel crisis and the developing attention paid to environment.Biofuels refers to any combustible materials that are or made from biomass,existing as solid,liquidor,gaseous.Biofuels have different traits from hydrocarbon fuels contributing to the oxygenated components.Therefore,to efficiently and cleanly utilize the biofuels,it’s of great significance to acquire knowledge of the combustion characteristic,such as laminar flame speed,intermediate distribution and its various,pollutant emissions.Simple alcohols and 30%H2+30%CO+40%N2 were selected on behalf of liquid biofuels and gaseous biofuels,respectively,to investgate the combustion characteristic of biofuel.Adiabatic burning velocity and turbulent flame structure were measured as a starting point.Presently,one of the major applications of bio-alcohol is mixed into the gasoline as motor fuels,to improve combustion and explosion proof.Therefore,the effect of alcoholic additives on the combustion of gasoline and its mechanism has received wide attention.A major utilization of biomass syngas is turbulent premixed combustion,which is influenced by burner structure,fuel dilution and turbulence intensity.Burner lip influence was focus on in this project to study the turbulent flame characteristics of biomass syngas.A simple pre-evaporation premixed combustion system was built to measure the laminar flame speed of(m)ethanol-TRF,using Heat Flux method and Bunsen method.Results showed that alcohol additives improve the combustion of gasoline,with faster burning velocity with more alcohol content.Laminar flame speed increases when the temperature of unburnt gas increases.To understand the kinetic mechanism of alcohol additives influence over gasoline,CHEMKIN3.7 was employed to simulate the combustion of(m)ethanol-n-heptane.It was found that concentration of radicals that trigger branched-chain reaction,such as OH,H,increses when(m)ethanol was added to n-heptane,while CH3 and C2H3,which are radicals connected to chain termination reaction,were inhibited.Ten key reactions of laminar burning velocity change under different equivalence ratio,with reaction H+O2<=>O+OH(R291)keeping maximum positive sensitivity factor in any condition.Sensitivity factor of R291 increases with the increasing equivalence ratio,which explains the greater affect of added alcohol in richer conditions.Sandia standard flame B,along with two other nonstandard flames with the variation of the wall thickness of the nozzle,was employed to study the turbulent flame structure and extinction characteristics of biomass syngas.Transient flame figure was capured using OH planar laser induced fluorescence technology,revealing more sophisticated flame front with increasing flame height because of the flame whirlling and air entrainment.As the height keeps increasing,there are phenomen of discontinuous distribution of OH signal,which is a local extinction.Image analysis of the region closest to the jet rim showed little difference between the flames other than an inverse relationship between the jet rim thickness and the initial growth rate of the flame wall width.Extinction events were similar in all three with a slight shift of extinction events downstream as the jet rim thickness increased.