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Increasing fuel injection pressure has enabled reduction of diesel emissions while retaining the advantage of the high thermal efficiency of diesel engines. With production diesel injectors operating in the range from 300 to 2400 bar, there is interest in injection pressures of 3000 bar and higher for further emissions reduction and fuel efficiency improvements. Fundamental understanding of diesel spray characteristics including very early injection and non-vaporizing spray penetration is essential to improve model development and facilitate the integration of advanced injection systems with elevated injection pressure into future diesel engines. Studies were conducted in an optically accessible constant volume combustion vessel under non-vaporizing conditions. Two advanced high pressure multi-hole injectors were used with different hole diameters, number of holes, and flow rates, with only one plume of each injector being imaged to enable high frame rate imaging.

Beginning with the interim Tier 4 legislation in the US, off-highway engines with 56 - 560 kW are required to reduce Particulate Matter (PM) emissions to less than 0.02 g/kWh. While this significant reduction in PM emissions represents a great new challenge for off-highway engines, it can be achieved with a combination of engine measures and PM aftertreatment technologies. An engine with high engine out PM emissions would require a wall flow filter which has to be frequently actively regenerated at temperatures above 600 degree C and requires measures to address ash collection. On the other hand, an engine with low to moderate engine out PM emissions could be fitted with a passively regenerated partial filter such as the PM-Metalit, with no need for frequent high temperature soot regeneration or ash removal maintenance [1, 2]. A PM-Metalit system is constructed solely from metal and thus is extremely robust against severe mechanical loads that are present in off-highway applications.

A Cummins B55 in3 350 bhp heavy-duty, turbocharged diesel engine was tested in fully cooled and uncooled modes over the EPA transient emission test cycles for comparison of gaseous and particulate emissions. The results are presented at the same fuel injection timing and at similar NOx emission levels. Also, steady state emission measurements and analysis of real-time transient emission data of selected runs are discussed. The uncooled engine does not represent an adiabatic (insulated) engine in its emission characateristics, but may indicate some trends. It may be useful in identifying design and/or operating parameters that need optimization.