Experimental and numerical study on the combustion characteristics of partially premixed charge compression ignition engine with dual fuel q Chang Sik Lee a, * , Ki Hyung Lee a , Dae Sik Kim b a Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791, South Korea b Graduate School of Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791, South Korea Received 1 April 2002; accepted 10 September 2002; available online 22 October 2002 Abstract The objective of this work is to investigate the effect of premixed fuel ratio on the combustion and emission characteristics in diesel engine by the experimental and numerical method. In order to investigate the effect of various factors such as the premixed ratio, EGR rate, and equivalence ratio on the exhaust gas from the premixed charge compression ignition diesel engine, the injection amount of premixed fuel is controlled by electronic port injection system. The range of premixed ratio between dual fuels used in this study is between 0 and 0.85, and the exhaust gas is recirclulated up to 30 percent of EGR rate. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: Premixed charge diesel combustion; Combustion characteristics; Exhaust emissions 1. Introduction During the last years diesel engines are used for automotive applications because they have a lower specific fuel consumption and superior efficiency compared to spark ignition engines. However, in spite of these advantages, NO x and particulate emissions from diesel engines have caused serious environmental problems in some applications. In conventional diesel engine, because the fuel is injected into the cylinder, spatial distribution of air–fuel ratio in the combustion chamber varies widely from rich to lean. To solve these problems in diesel engine, a lot of researches on the premixed charge compression ignition engine to supply homogeneous charge with combustion chamber before ignition have been performed in various ways, by using natural gas [1,2], methane [3], butane [4,5], and gasoline [6–8] as a premixed fuel. Also, there are some efforts to predict the combustion characteristics of homogeneous charge compression ignition engine (HCCI) with single zone model to treat the entire charge in combustion chamber as being completely uniform during compression and expansion stroke [9,10]. From these previous works, it was found that single zone model is a useful tool for investigating certain fundamental aspects of HCCI combustion and allows the full chemical-kinetic mechanisms with relatively short computational time. These previous studies on homogeneous charge com- pression ignition engine showed that it can be regarded as one of the most useful method for simultaneous reduction of NO x and soot emission. However, the combustion mechan- ism of HCCI engine and the emission control of diesel and premixed fuel in the combustion chamber are still unknown and there is still uncertainty about the reduction of the hydrocarbon emission. In this sense, the objective of this work is to experimen- tally and numerically obtain the effect of premixed fuel ratio on the combustion characteristics and reduction of nitric oxide and particulate matter emissions in diesel engine. In order to investigate the effect of premixed ratio on NO concentration and smoke in a direct-injection diesel engine, gasoline fuel was used as the premixed fuel to be supplied additionally, because the premixed charge compression ignition engine with gasoline fuel has some advantages that the injection system for gasoline can be supplemented in conventional diesel engine easily with modification of an intake port and combustion chamber and it is simple to control the fuel injection, compared with other fuels [6–8]. 0016-2361/03/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S0016-2361(02)00319-8 Fuel 82 (2003) 553–560 www.fuelfirst.com q Published first on the web via Fuelfirst.com_http://www.fuelfirst.com * Corresponding author. Tel.: þ 82-2-2290-0427; fax: þ82-2-2281-5286. E-mail addresses: cslee@hanyang.ac.kr (C.S. Lee), hylee@hanyang. ac.kr (K.H. Lee), kimd@ihanyang.ac.kr (D.S. Kim).