Cycle-Controlled Water Injection for Steady-State and Transient Emissions Reduction From a Heavy-Duty Diesel Engine

A system for coinjecting mixtures of diesel fuel and water into a heavy-duty diesel engine has been developed and evaluated at the Southwest Research Institute. This system features prototype Lucas electronically controlled injectors, full electronic control, and can vary the percentage of water in the mixture on a cycle-resolved basis. Tests of this system were conducted on a production Volvo D-12 engine, and have produced reduced $NOx$ and smoke emissions over steady-state and transient conditions. Water-diesel coinjection yielded a considerable improvement in $NOx$-smoke and $NOx$-BSFC trade-offs under steady-state engine operation. In addition, control of the water percentage on a cycle-resolved basis was shown to be an effective method for mitigating $NOx$ and smoke emissions over step-load transients. Results from this work show that a combination of aggressive EGR and $diesel+water$ coinjection is very promising for producing very low levels of engine-out exhaust emissions, reducing the water storage requirements, and improving fuel efficiency. Further refinement of this injection technology is in progress.