Bio-diesel effects on combustion processes in an HSDI diesel engine using advanced injection strategies

An optically accessible single-cylinder high-speed direct-injection (HSDI) diesel engine was used to investigate the combustion process using different fuels including European low sulfur diesel and bio-diesel fuels with advanced multiple injection strategies. Influences of injection timings and fuel types on combustion characteristics and emissions were studied under similar loads. In-cylinder pressure was measured and used for heat release analysis. High-speed combustion videos were captured for all the studied cases using the same frame rate. NO(x), emissions were measured in the exhaust pipe. Different combustion modes including conventional diesel combustion and low-temperature combustion were observed and confirmed from the heat release rates and the combustion images. Natural luminosity was found consistently lower for bio-diesel than the European low sulfur diesel fuel for all the cases. However, for NO(x), emissions, Under conventional combustion cases Such as cases 2 and 3, it was found that bio-diesel leads to increased NO(x) emissions. Under a certain injection strategy with retarded main injections like case 4 and 5, it is possible to have up to 34% lower NO(x) emissions for B100 than B0 for case 4 with low-temperature combustion mode. Simultaneous reduction of NO(x) and natural luminosity was achieved for advanced low-temperature combustion mode. It is hypothesized based on the results that the lower soot generation for bio-diesel fuel is believed due to a lower soot formation rate and a higher soot oxidation rate. The NO(x), increase problem for bio-diesel fuel can be amended by employing advanced injection strategies with low-temperature combustion modes. (c) 2009 The Combustion Institute. Published by Elsevier Inc. All rights reserved.