Ethanol and ethanol-gasoline mixtures exhibit specific physical and chemical properties that govern the processes chain of atomization,evaporation,mixing,combustion and soot formation.Especially for conditions with short mixing times the soot formation is intensified which is a severe issue for DISI(direct injection sparkignition)conditions with late injection timing.In particular the high enthalpy of evaporation(physical fuel property)of ethanol may have an effect on soot formation,but also the oxygen content(chemical fuel property)may play a dominant role.In this study a constant volume spray chamber(CVC)was equipped with a spark ignition system for the investigation of spray combustion.The effects of fuel properties and blending on sooting combustion are analyzed at different injection conditions by changing the time of ignition,chamber pressure and temperature as well as the fuel pressure.Furthermore,a spray formation investigation was carried out in order to evaluate the fuel evaporation process at different conditions.The spray combustion and sooting behavior of ethanol-isooctane mixtures are studied by simultaneous high speed imaging of OH*-chemiluminescence and soot luminosity.This approach allows for the visualization and evaluation of premixed and sooting combustion.The results indicate that depending on the operation conditions(especially for varied ambient gas temperatures)either the chemical or the physical properties of the fuel dominate the combustion and sooting behavior.At special conditions(0.8 MPa,473 K)the ethanol mixture E20 shows increased soot radiation compared to the reference fuel isooctane.For much higher ethanol concentrations the soot radiation is reduced indicating that chemical effects become dominant.