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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.

Cylinder head and piston temperatures and heat fluxes were measured in a DOHC engine. Measurements for the combustion chamber were made at different engine speeds and engine loads. Twenty-one instantaneous temperature probes were totally embedded in a cylinder head and a piston. Major conclusions of this research include; 1) the instantaneous temperature on the cylinder head was affected by flame traveling distance, gas flow characteristics, and cooling passage; 2) all temperatures at the exhaust valve heads with different engine loads are much higher than those at the intake valve heads; 3) the instantaneous surface temperature at around exhaust valve pocket is higher than that at piston crown center; 4) the instantaneous temperatures of the top-ring groove and the second land are also varied; and 5) heat flux in the piston crown is largely occurred during the expansion stroke and the heat flux has dissimilar trend to the temperature distribution.

The change of spray shape under different ambient pressure and the size distribution of fuel droplets from swirl injector were investigated. And, for the stratified-mixture operation in the vicinity of spark plug, fuel distribution after impingement on piston in motoring engine was examined in the cases of two different injector positions. Also, the influence of intake port geometry and piston top shape on in-cylinder air flow during intake to compression stroke was investigated. This paper concludes that, in tumble-based combustion strategy, locating swirl injector at intake side of cylinder head and making counter-rotating tumble increased in intake port geometry and conserved on bowl piston surface would be very effective for stratified combustion of spark-ignited direct injection engine.