A study on the combustion and emission characteristics of diesel fuel blended with ethanol in an HCCI engine

Abstract

As the exhaustion of petroleum resources and air pollution problems are getting more serious day by day, demands for low emission levels and higher thermal efficiency of vehicle engines have been increased. In light of this, the diesel engine has many advantages such as high thermal efficiency, a cheaper price of fuel, and what is more it has a low CO2 exhaustion level well known as the factor of ‘Global Warming’, therefore the use of diesel engines is getting increased. However in the case of diesel engine, NOx increases in the local high temperature region, and particulate matter increases in fuel rich regions. That is why, getting down the peak temperature to reduce NOx emission and making better air-fuel mixing to minimize particulate matter formation are required and Homogeneous Charge Compression Ignition (HCCI) is a technique which can make those conditions. In the HCCI engine, a largely premixed lean mixture is burned by compression ignition and in this way, it has the advantages of both thermal efficiency and emission reduction. However it also has got a limited operating region because of difficulties of reducing the droplet collision with the cylinder wall and controlling the ignition timing. The present study builds on the narrow spray cone angle concept and investigates its use in conjunction with early multiple injection to help reduce wall wetting and create a more homogeneous mixture. In addition many methods to control the ignition timing are now under study as well. For the reason, in this research, the effect of injection strategies on spray, mixture formation, the combustion and emission characteristics were verified with an HCCI engine and simulation for 100% diesel fuel first, and then diesel fuel blended with ethanol using the optimized injection conditions acquired from the earlier research was used to investigate the effects of mixed fuel on the ignition timing and engine efficiency.