The two main problems confronted in diesel engine are emissions of particle matter (PM) and nitrogen oxides (NO x). The approaches to improving emission performance of diesel engine include variable injecting timing (VIT), exhaust gas recirculation (EGR), variable air component in combustion, DME/diesel blended fuel, selective catalytic reduction (SCR) and so on. Reducing emissions by using water is a new technique developed in recent year, which can optimize combustion performance of diesel engine and low...