Christopher Chadwell

Effect of Diesel and Water Co-injection with Real-Time Control on Diesel Engine Performance and Emissions

A system for injection of diesel fuel and water with realtime control, or real-time water injection (RTWI), was developed and applied to a heavy-duty diesel engine. The RTWI system featured electronic unit pumps that delivered metered volumes of water to electronic unit injectors (EUI) modified to incorporate the water addition passages. The water and diesel mixed in the injector tip such that the initial portion of the injection contained mostly diesel fuel, while the balance of the injection was a water and diesel mixture. With this hardware, realtime cycle-by-cycle control of water mass was used to mitigate soot formation during diesel combustion. Using RTWI alone, NOx emissions were reduced by 42%. Using high-pressure-loop exhaust gas recirculation (EGR) and conventional diesel combustion with RTWI, the NOx was reduced by 82%. Perhaps the most promising results obtained with the RTWI system were the simultaneous NOx and smoke reductions during a load step transient while realizing a faster torque rise than otherwise obtainable within smoke limits.

The Effect of Water on Soot Formation Chemistry

A combined, experimental and numerical program is presented. This work summarizes an internal research effort conducted at Southwest Research Institute. Meeting new, stringent emissions regulations for diesel engines requires a way to reduce NO x and soot emissions. Most emissions reduction strategies reduce one pollutant while increasing the other. Water injection is one of the few promising emissions reduction techniques with the potential to simultaneously reduce soot and NO x in diesel engines. While it is widely accepted that water reduces NO x via a thermal effect, the mechanisms behind the reduction of soot are not well understood. The water could reduce the soot via physical, thermal, or chemical effects. To aid in developing water injection strategies, this projects goal was to determine how water enters the soot formation chemistry. Linked burner experiments and modeling of a rich premixed flame were used to determine the magnitude of the thermal and chemical effect of water on soot formation and identify a possible kinetic mechanism to explain it. Following Decs model for diesel combustion processes (Dec, 1997; Flynn, et al., 1999) [1,19] , soot inception results from rich premixed combustion; thus the rich premixed flame provides an appropriate venue in which to isolate the influence of water on the kinetics. Open flame, burner experiments have been performed to quantify the soot inception point and the relative amounts of soot formation in premixed flames with and without water addition. These results have been used to expand and compliment data available in the published literature. Subsequent modeling has been used to predict trends in soot inception using currently accepted kinetic soot mechanisms. Results from this effort led to a revised kinetic mechanism for the process. Comparison of the experimental and modeling data has been used to assess the accuracy of soot formation mechanisms and ultimately has yielded a new understanding of the soot formation chemistry and the role of added water.

Measurement of Laminar Burning Velocity of Multi-Component Fuel Blends for Use in High-Performance SI Engines

A technique was developed for measuring the Laminar Burning Velocity (LBV) of multi-component fuel blends for use in high-performance spark-ignition engines. This technique involves the use of a centrally-ignited spherical combustion chamber, and a complementary analysis code. The technique was validated by examining several single-component fuels, and the computational procedure was extended to handle multi-component fuels without requiring detailed knowledge of their chemical composition. Experiments performed on an instrumented high-speed engine showed good agreement between the observed heat-release rates of the fuels and their predicted ranking based on the measured LBV parameters.