Experimental Study On The Characteristics Of Biodiesel Combustion Flame

The basic properties of biodiesel combustion flames and the relationship between OH and soot or CO generation,were studied by using OH-PLIF.At present,there are few studies carried out by this technique on the flame characteristics of biodiesel combustion in China.However,it is self-evident that the combustion process and the combustion products studied from the perspective of free radicals in combustion process are important.This article launches the research around this perspective.Firstly,The OH-PLIF system used in this research is introduced.The OH free radical excitation principle is discussed,and the key operation and precautions of PLIF system are discussed in detail;properties of combustion fuel were determined.These two steps are the prerequisites for the start of the experiment.Secondly,due to the use of OH-PLIF on biodiesel combustion will produce larger noise signal,so the OH signal of biodiesel combustion were analyzed.OH signals contain signals from OH,PAH,soot and fuel vapor scattering.The way to eliminate the noise signal is proposed.Control of fuel vapor scattering requires the control of non-combustible fuel vapor from entering the test area.For the control of the noise signal of PAH and soot,the excitation laser can be adjusted to make it far away from the optimal excitation wavelength of OH,and then subtract the signal collected under this condition.Thirdly,combustion flame characteristics of the rubber seed oil biodiesel,jatropha biodiesel and waste cooking oil biodiesel,such as flame height,focus on the distribution of OH and CO emissions,were studied,with the increase of fuel flow rate,the average OH free radical signal increases first and then decreases with the increase of fuel flow rate,while CO is the opposite.Finally,the combustion characteristics of blended fuels of waste cooking oil biodiesel and diesel oil and waste oil biodiesel and ethanol were studied.With the increase of the addition ratio of the waste oil biodiesel,the production of flame soot decreased,the soot channel narrowed,and the CO emission decreased,while the average OH signal intensity first increased and then decreased.Ethanol addition makes the average OH signal intensity of flame at different fuel flow rate tend to be consistent.Average OH signal intensity begins to weaken at larger fuel flow rate,which indicates that fuel flow rate of fuels blended with ethanol can change in larger range and does not significantly affect the uniformity of combustion.