Fuel Injection and Spray Research

Diesel Sprays

Christopher Powell, an engine research scientist, fits a specially designed X-ray pressure window to a high-pressure chamber used in diesel spray research. These windows allow Argonne researchers to use X-rays to probe diesel sprays under the high-density conditions found in diesel engines.

Diesel engines are significantly more fuel-efficient than their gasoline counterparts, so wider adoption of diesels in the U.S. would decrease the nation’s petroleum consumption. However, diesels emit much higher levels of pollutants, especially particulate matter and NOx (nitrogen oxides). These emissions have prevented more manufacturers from introducing diesel passenger cars.

Researchers are exploring ways to reduce pollution formation in the engine by using clean combustion strategies. A key component to the development of clean combustion is controlling the fuel spray and fuel/air mixing.

Argonne’s studies of diesel sprays have led to several new discoveries. For the first time, quantitative measurements of the mass distribution within fuel sprays have been obtained with very precise time resolution. In addition, the density of the fuel can be calculated at any position and time within the spray. This result proved for the first time that sprays from modern diesel injectors are atomized only a few millimeters from the nozzle.

Sprays from nozzles with different internal structures have also been quantitatively measured under identical experimental conditions. The resulting differences in the mass distributions of the sprays will prove very useful to spray modelers trying to understand the effects of nozzle geometry on the structure of sprays.

Spray structure is important since it determines how the fuel and air mix together in the engine combustion chamber. A spray that poorly atomizes fuel will lead to fuel-rich regions in the cylinder, while a spray that is overly dispersed will lead to a mixture that is too lean. At both of these extremes, combustion either cannot take place, burns inefficiently or it generates high levels of emissions.

A spray that distributes the fuel optimally will lead to engine combustion that is clean and efficient. The results of this project help in understanding how various factors (injector design, fuel pressure, cylinder pressure, temperature, etc.) affect the fuel distribution, and how these variables might be manipulated to develop clean, efficient engines.

Funding

This work is supported by the U.S. Department of Energy’s Vehicle Technologies Program under Gurpreet Singh.

More

• X-ray Measurements of the Mass Distribution in the Dense Primary Break-Up Region of the Spray from a Standard Multi-Hole Common-Rail Diesel Injection System (1.1 MB pdf)
• X-ray Radiography Measurements of Diesel Spray Structure at Engine-Like Ambient Density (672 kB pdf)
• Near Field Characterization of Direct Injection Gasoline Sprays from Multi-Hole Injector Using Ultrafast X-Tomography (980 kB pdf)

April 2010