Emissions Measurements in a Steady Combusting Spray Simulating the Diesel Combustion Chamber

In-cylinder control of particulate emissions in a diesel engine depends on careful control and understanding of the fuel injection and air/fuel mixing process. It is extremely difficult to measure physical parameters of the injection and mixing process in an operating engine, but it is possible to simulate some diesel combustion chamber conditions in a steady flow configuration whose characteristics can be more easily probed. This program created a steady flow environment in which air-flow and injection sprays were characterized under non-combusting conditions, and emissions measurements were made under combusting conditions. A limited test matrix was completed in which the following observations were made.

• Grid-generated air turbulence decreased particulates, CO, and unburned hydrocarbons, while CO₂ and NO_x levels were increased. The turbulence accelerated combustion, resulting in more complete combustion and higher temperatures at the measurement location.
• Increased injection pressure at equivalent fuel flowrates reduced particulate, CO, CO₂, and NO_x levels, while unburned hydrocarbon levels increased. The higher injection pressures resulted in more complete fuel/air mixing although combustion was not as complete because the spray reached the measurement location in a shorter period of time.