An Investigation on the Efficiency Correction Method of the Turbocharger at Low Speed

Abstract

Abstract:The heat transfer in the turbocharger occurs due to the temperature difference between the exhaust gas and intake air, coolant, and oil. This heat transfer causes the efficiency of the compressor and turbine to be distorted, which is known to be exacerbated during low rotational speeds. Thus, this study proposes a method to mitigate the distortion of the test result data caused by heat transfer in the turbocharger. With this method, the representative compressor temperature is defined and the heat transfer rate of the compressor is calculated by considering the effect of the oil and turbine inlet temperatures at low rotation speeds, when the cold and the hot gas test are simultaneously performed. The correction of compressor efficiency, depending on the turbine inlet temperature, was performed through both hot and cold gas tests and the results showed a maximum of 16% error prior to correction and a maximum of 3% error after the correction. In addition, it shows that it is possible to correct the efficiency distortion of the turbocharger by heat transfer by correcting to the combined turbine efficiency based on the corrected compressor efficiency.

Study on the Effect of Turbine Inlet Temperature and Backpressure Conditions on Reduced Turbine Flow Rate Performance Characteristics and Correction Method for Automotive Turbocharger

“…The WGT tests in this study included very low turbine inlet temperature conditions (313.15 K) and high-temperature (573.15-873.15 K) experiments. Therefore, additional compressor power correction was performed because the measured compressor power at high turbine inlet temperature conditions presented relatively large distortions due to heat transfer from the turbine [11,13,17].…”

“…In the case of WGT, various turbine inlet temperature condition gas bench tests were performed, and the construction of the heat transfer equation using the temperature change test results was possible. The relevant method is briefly presented below [11,13].…”

“…Coefficients α and γ are values related to heat conduction that can be determined as minimizing differences when the compressor efficiency was corrected using turbine inlet variation tests. The representative temperature of the compressor T comp is the algebraic average of the inlet and outlet temperature of air [11,13]: Figure 7a shows the effective turbine efficiency obtained from the gas bench test of WGT for the expansion ratio, which is a general expression method. As shown in the results, under the conditions of an expansion ratio of 1.6 or higher is confirmed, and similar and constant efficiency characteristics are presented despite the turbine inlet temperature and rotation speed changes.…”

“…This heat transfer causes temperature measurement errors in the after compressor temperature and the before and after turbine temperature in the middle and low speed ranges (in particular, the range of up to approximately 0.4 to 0.5 times the maximum rotational speed of the compressor is relatively small before and after the temperature difference), which is the turbocharger condition during actual engine operation. These measurement errors make it impossible to perform accurate measurements of isentropic efficiency [11].…”

“…Therefore, a cold gas test, which sets the turbine inlet temperature as similar to the compressor temperature, has been used to investigate the distortion of the compressor efficiency due to heat exchange with the goal of correcting the efficiency [11,12].…”