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A Glow-Plug Assisted Direct-Injection Diesel Engine Using Low- Ignitability Fuels
Published January 01, 1990 by Associazione Tecnica Dell'Automobile in Italy
A glow plug assisted direct-injection diesel engine using low- ignitability fuels was studied. Tests were conducted on an experimental single-cylinder four-cycle engine having a high-swirl deep-bowl combustion chamber. The test results showed that less noisey and less smokey operation can be achieved under certain compression ratios and injection timings that cannot be achieved with ordinary diesel engines. This characteristic is caused by a two- staged combustion; a lower rate of heat release in the earlier burning stage and a higher rate in the later stages. In this combustion system, the ignition-assisted spray ignites with a short delay and the remaining sprays have a long ignition delay due to poor autoignitability. The low smoke concentration is attributed to a long ignition-delay contributing to the fuel-air mixing. The effects of engine parameters on thermal efficiency, smoke, oxides of nitrogen, and unburned hydrocarbons were investigated for butane, neat methanol and pure aromatic fuel. The test results showed that a higher thermal efficiency and a lower smoke concentration were achieved. However, a high concentration of unburned hydrocarbons at a partial load is a crucial factor that requires attention.