Title: A study on the amount of pilot injection and its effects on rich and lean boundaries of the premixed CNG/air mixture for a CNG/diesel dual-fuel engine

Authors: Zhiqiang Lin, Wanhua Su

Addresses: State Key Laboratory of Engines, Tianjin University, 92 Weijin Road, Nankai District, Tianjin University, Tianjin, China ' State Key Laboratory of Engines, Tianjin University, 92 Weijin Road, Nankai District, Tianjin University, Tianjin, China

Abstract: A sequential port injection, lean-burn, fully electronically-controlled compressed natural gas (CNG)/diesel dual-fuel engine has been developed based on a turbo-charged and inter-cooled direct injection (D.I.) diesel engine. During the optimisation of engine overall performance, the effects of pilot diesel and premixed CNG/air mixture equivalence ratio on emissions (CO, HC, NO_x, soot), knocking, misfire and fuel economy are studied. The rich and lean boundaries of the premixed CNG/air mixture versus engine load are also provided, considering the acceptable values of NO_x and THC emissions, respectively. It is interesting to find that there is a critical amount of pilot diesel for each load and speed point, which proved to be the optimum amount of pilot fuel. Any decrease in the amount of pilot diesel from this optimum amount results in an increase of NO_x emissions, because the premixed CNG/air mixture must be made richer, otherwise THC emissions would increase. However, the soot emissions remain almost unchanged at a very low level.

Keywords: air/CNG ratio; amount of pilot diesel; lambda boundary; pilot injection; dual-fuel engine; natural gas; diesel.

DOI: 10.1504/IJGEI.2003.003968

International Journal of Global Energy Issues, 2003 Vol.20 No.3, pp.290 - 301

Published online: 10 May 2004 *

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