Proceedings of the International Conference on Power Engineering-09 (ICOPE-09) November 16-20, 2009, Kobe, Japan EXPERIMENTAL INVESTIGATIONS OF USING WATER-GASOLINE EMULSIONS AS A NOx TREATMENT AND ITS EFFECTS ON PERFORMANCE AND EMISSIONS OF LEAN-BURN SPARK-IGNITION ENGINE Quang-Anh Nguyen, Yuh-Yih Wu Dept. of Vehicle Eng., National Taipei University of Technology, 1, Sec. 3, Jhongsiao E. Rd., Taipei, Taiwan ABSTRACT Automotive emission regulations are becoming more and more stringent. The NOx standards still pose a formidable challenge. As we known, lean combustion is one of the best ways to reduce fuel consumption at part engine load. However, it produces higher NOx emissions. The reasons are high combustion temperature and excess of oxygen in cylinder. Both water-gasoline fuel emulsions and exhaust gas recirculation (EGR) are used to absorb the heat in cylinder and reduce the combustion temperature. This paper introduces the process of intake port modification to develop a lean burn system. It also studies about applicable technique –water-gasoline emulsions - used in this engine for reducing the NOx. To reach the lean combustion, the original intake port of a four-stroke spark-ignition (SI) engine was modified to generate tumble by using various flow control baffles. The in-cylinder air motion generated by each configuration was characterized using swirl and tumble flow bench to choose the optimum one. The first test is trying to reach the lean-limit of both original engine and modified one using pure gasoline. After that, this lean burn engine was tested with three different water concentrations of water-gasoline emulsions – 5%, 10% and 15% respectively. Test conditions are based on vehicle running at 90 km/h on the high way. The engine torque, fuel consumption, exhaust emissions, and combustion characteristics of all tests were investigated. Water-gasoline emulsion has a positive effect on NOx reduction with a suitable water concentration at 5% by mass. The NOx emissions has been decreased 35.0% approximately in comparison with lean-burn engine using pure gasoline Keywords: Water-gasoline emulsion; lean burn; SI engine. 1. INTRODUCTION Today’s car makers all over the world are joining in huge competitions that technology is a key factor for the winners. In addition, the application of more strict regulations concerning the level of exhaust emissions urges research efforts. Actually, lean-burn spark-ignition engine technology with a long history of development is one of major directions. There are several ways to reach lean combustion. Kim et al [1] used intake air control valve and independent helical port to extend lean limit. Swamy et al [2] used pre-chamber – a turbulence generating port and advanced technologies such as special ignition system, coating combustion chamber etc. to reach get lean combustion without deterioration of engine performance and emission. Summarily, Yamamoto [3] gave a general view of relationship between thermal efficiency and NOx formation- major concerns-in ultra-lean combustion. This research also mentioned about the potential of emulsified fuel with positive factors when using on lean-burn engine. During lean-burn engine development process, modification always takes great concerns from researchers. Originally, the experiment engine is stoichiometric-burning type. To extend lean limit, stratified charge was chosen as the method to improve combustion. As mentioned by Floch et al [4], high tumble intensity shows a high potential to improve combustion stability while creates a region of relatively rich (strictly, less lean) mixture close to spark plug. That is the reason of using tumble flow control baffles in our research. Moreover, lean combustion can be achieved without any change of intake port or cylinder head. As mentioned by previous researches [5], [6] the increase of NOx emissions can be a negative effect of lean combustion. Some techniques that have been under widen research and discussion like using of EGR, water additions to the combustion chamber or three-way catalyst. The second technique which is widely applied in diesel engine can be evaluated into three types: water-fuel emulsion, water injection using separated injector and addition of water at the engine intake manifold. In this paper, we only mention about the using of water-gasoline emulsion. The key for decreasing NOx emissions level while using water-fuel emulsion is the reduction of peak combustion temperature in combustion chamber. Bruce et al. [7] has investigated the effects of water-gasoline fuels on SI Engine emission and performance. The results showed that water-gasoline emulsion can decrease NOx following with the definite antiknock characteristics. Manuel et al. [8] experimented on diesel engine and found that due to the lower energy content of the diesel water fuel blends, the engine produced less power when mapped at full load, compared to base fuel. The number of researches on water-fuel emulsion has grown rapidly but basically on diesel engine. Because of this reason, an experimental research of water-gasoline emulsions in the specific area as lean-burn SI engine is presented in this paper. The first section introduces the experimental process of lean-burn engine development which includes flow bench test of various tumble baffles