Experimental Study of Inlet Manifold Water Injection on a Common Rail HSDI Automobile Diesel Engine, Compared to EGR with Respect to PM and Nox Emissions and Specific Consumption

This paper presents an experimental study of a water injection (WI) application where water fog is added in the intake of a common rail High-Speed Direct Injection (HSDI) automobile Diesel engine in order to reduce pollutant emissions Nitrogen Oxides and Particulate Matter (NOx and PM) for future emissions standards. Also studied are the physical parameters of the engine (in-cylinder pressure, air inlet temperature, air mass flow, specific fuel consumption etc). The results are compared with those obtained with low-pressure dry Exhaust Gas Recirculation (LP EGR) on the same engine. Tests performed with the water injection system show that a much better NOx / PM trade-off (reduced NOx emission levels at constant PM emission levels) is obtained than with EGR especially at points of high engine loads. In addition, tests are performed with EGR in parallel with water injection to investigate the reduction of NOx emissions while potentially reducing water consumption. Quantities of water injected are between 3 and 21 kg/h which correspond to water / fuel ratios of up to 400 percent depending on the engine operating point.