Improvements in the performance and pollutant emissions for stoichiometric diesel combustion engines using a two-spray-angle nozzle

An experimental and numerical study was conducted to investigate the effect of the nozzle layout on the combustion and emission characteristics for stoichiometric diesel combustion. In order to improve fuel-air mixing, a new concept of nozzle layout was studied. The nozzle has two spray angles, one heading for the bowl and the other targeting the squish area (two-spray-angle nozzle (2SAN)). The spray included angles of the nozzle layout are 150 degrees (upper holes) and 70 degrees (lower holes), and the start-of-injection timings were swept from -33 degrees to -9 degrees after top dead centre. The results of the 2SAN were compared with those of a well-characterized baseline single-hole nozzle (SHN) with a 130 degrees spray included angle. The experimental results showed that the engine performance and carbon monoxide emissions were reduced significantly by using the 2SAN instead of the SHN with stoichiometric diesel combustion. However, hydrocarbon emissions were increased owing to fuel-film formation. In addition, the range of optimal injection timings for reduced fuel consumption for the 2SAN is wider than that of the SHN because the upper spray of the 2SAN utilizes oxygen in the squish area more efficiently.The authors acknowledge support from the Engine Research Center's Diesel Engine Research Consortium (formerly the Diesel Emission Reduction Consortium). This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (Grant 2009-0072881). Denso is thanked for providing injector nozzle support