The determination of the isentropic turbine efficiency under adiabatic and SAE boundary conditions is studied in this paper. The study is structured into two parts. The first part describes the possibility of measuring the isentropic turbine efficiency directly. Normally this is not possible in measurements conducted following the SAE J922 guidelines. Therefore, the experiments have been carried out under adiabatic conditions, and combined with improved measuring equipment. The results were compared with adiabatic computational fluid dynamics simulations of this turbocharger. In the second part, a new criterion is defined in order to evaluate the quality of the adiabatic measurements and compare them with standard measurements. The investigation has been carried out with multiple turbochargers ranging from very small to medium passenger car size turbochargers. In the end, a possible application for the criterion is given.
With conventional combustion processes there remain unused regions with air between the injection jets. To use these, a 14-hole-nozzle and a nozzle with six smaller and six larger spray hole diameters were developed. Both nozzles show strongly increased soot emissions. The optical analysis shows that the combustion zones of the 14-hole-nozzle overlap and create very rich local combustion zones. Furthermore, the small spray hole diameters reduce the spray momentum and a backflow from the piston bowl which would lead to improved air utilization cannot be created. The small spray holes of the 6?6-nozzle create a spray momentum that is too large to only use the air in the middle of the combustion chamber. At the same time the injection jets restrain the backflow generated by the larger spray holes.
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