The Relationship Between Nitric Oxide and Work as Influenced by Engine Operating Conditions and Combustion System Parameters for a Direct Injection Diesel Engine

The objective of the work was to conduct a parametric study using the major combustion system variables to investigate the parameters controlling the nitric oxide and fuel economy trade-off, identify the major basic in-cylinder physical processes responsible, and relate these processes to the hardware features. The study was conducted using a multizone, fuel and air jet mixing model with a temperature and concentration dependent fuel reaction rate, and nitric oxide kinetics. The effect of engine variables on the relationship between nitric oxide emissions and work during the valve closed part of the engine cycle was studied by systematically changing twelve engine variables. Selected parameter variations were also repeated experimentally using a single cylinder engine. For the conditions simulated in this work, it is shown that parameters controlled by the engine air system, such as the in-cylinder state at intake valve closure, can be specified in a manner that results in nearly constant or increasing work with a decrease in nitric oxide. Fuel system variables, also for the conditions simulated, result in decreasing work with decreasing nitric oxide. Several groupings of engine variables were found which characterized the basic in-cylinder processes and related them to the nitric oxide emissions produced and the work levels achieved.