By a special test rig the flow and efficiency characteristics of turbocharger radial turbines with partial admission are determined. A considerable deviation from the full admission behaviour is found. The flow rig results are used in a mathematical model to predict the performance of a turbocharged automotive diesel engine. Reasonable agreement between calculation and measurements is obtained, which prove the validity of the method. The flow rig method described above in combination with the mathematical model is a valuable instrument for assessment of turbocharger characteristics and their improvement. For example the influence of different flow characteristics on engine performance can be predicted. Thereby recommendations can be worked out for the designer of a turbocharger, in which direction the characteristics should be developed. It is well known that the turbocharger efficiency has an important influence on the engine efficiency and also the torque characteristic. It is interesting to examine the range of turbine efficiencies for different engine speeds. As an example this has been done for the above mentioned engine. It should be recalled that the mean pressure level is calculated on base of the two inlet pressures of the turbine and varies over the working cycle. It can be seen that with high engine speed the turbine efficiencies do not deviate noticeably from those with full admission throughout the whole working cycle. As the main energy flow to the turbine occurs in the range of maximum mean pressure level the efficiency of the turbine could still be improved, in that range by modifying the turbine adaptation. For an automotive diesel engine the torque characteristic is often regarded nearly as important as low fuel consumption. For a good torque characteristic high turbine efficiencies should be realized at low engine speed. The efficiencies during the important part of the working cycle (with high mean inlet pressures) are markedly smaller than with full admission.
The characteristic behaviour of radial turbines and its influence on the turbocharging process
Die Eigenschaften von Radialturbinen und ihr Einfluss auf die Turboaufladung
1977
24 Seiten, 17 Bilder, 2 Tabellen, 12 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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