Search Results

High pressure fuel injection systems, such as common rail (CR) systems and electronically-controlled unit injector (EUI) systems, have been widely applied to modern heavy duty diesel engines. They are shown to be very effective for achieving high power density with high fuel efficiency and low exhaust gas emissions. However, the increased peak combustion pressure gives additional structural stress and thermal load to engine structure. Thus, proper material selection and thermal analysis of engine components are essential in order to meet the durability requirements of heavy-duty diesel engines adopting a high pressure injection system. In this paper, thermal analysis of a 12.9 ℓ diesel engine with an EUI system was studied. Temperatures were measured on a cylinder head, a piston and a cylinder liner. A specially designed linkage system was used to measure the piston temperatures. A radio-tracer technique was also used to verify the rotation of piston rings.

Spray tip penetration and dispersion in high pressure diesel engines have been simulated experimentally with a special emphasis on the effect of swirl. A constant volume chamber was designed to be rotatable in order to generate a continuous swirl and to have the flow field closely resembling a solid body rotation. Emulsified fuel was injected into the chamber and the developing process of fuel sprays was visualized. The effect of swirl on the spray tip penetration was quantified through modeling. Results show that the spray tip penetration is qualitatively different between low and high pressure injections. For high pressure injection, good agreement is achieved between the experimental results and the modeling accounting the effect of swirl on spray penetration. For low pressure injection, reasonable agreement is obtained. The modeling result can be used as basic design data in diesel injector development.