Ottenwaelder, T., Raffius, T., Schulz, C., Adomeit, P. et al., "Optical Investigation of Biofuel Effects on NO and PAH Formation in Diesel-Like Jets," SAE Technical Paper 2015-24-2485, 2015, doi:10.4271/2015-24-2485.
In order to reduce engine out CO2 emissions it is a main subject to find new alternative fuels out of renewable sources. For this reason in this paper a blend out of 1-octanol and di-n-butylether and pure di-n-butylether are investigated in comparison to n-heptane as diesel-like fuel. The alternative fuels have a different combustion behavior particularly concerning important combustion parameters like ignition delay and mixture formation. Especially the formation of pollutants like nitrogen oxides in the combustion of alternative fuels is of global interest. The knowledge of the combustion behavior is important to design new engine geometries or implement a new calibration of the engine. In previous measurements in a single cylinder engine it was found out that both alternative fuels form nearly no soot emissions. For this reason now NOx is investigated optically to avoid the traditional soot NOx trade-off in diesel combustion. The three fuels are investigated in a High-Pressure Chamber (HPC) to avoid any influence of ambient- air turbulence on the combustion of the fuels. For the analysis of the fuels the optical measurement technique Laser Induced Fluorescence (LIF) was installed at the test bench. The measurement technique was implemented on the centerline of the fuel jet and positioned near the lift-off length of the flames. To investigate also the mixture formation of the fuels the rail pressure and the time of injection were varied. The measurements show the different behavior of NOx formation under mainly lean or rich conditions respectively which are caused by the different fuels.