The purpose of this study was to improve the fuel efficiency in vehicles based on the performance characteristic analysis of AC(Air Conditioning) compressor. So the simulation test mode in the AC bench system instead of vehicle was developed for the SC03 fuel economy evaluation. Additionally, a compressor torque sensor measuring driving torques of compressor in vehicle was developed and the torque sensor was useful on analysis of vehicle fuel economy and characteristics of AC system.
The characteristic analysis of AC compressor was performed on a compressor calorimeter test stand using the 2nd refrigerant calorimeter method and the compressor bench test stand was featured to control temperature and humidity in each chamber for compressor, condenser and evaporator prepared separately in bench. Compressor RPM(Revolution Per Minute) and air flow rate into condenser were also controlled in bench for the fuel economy bench simulation test.
The torque sensor was prepared by installing a strain gauge on the clutch of AC compressor considering reliability of measuring data. The fuel consumption of vehicle in CWT(Climate Wind Tunnel), calculated by flowmeter method, was compared with the results of the bench simulation test mode. The results of the study are summarized as follows.
In the experimental study on the performance characteristics of compressor, the pressure pulsation characteristics depending on numbers of cylinder were found and the internal pressure measured in cylinders was higher with 50% than in pipes. In addition, we also found that automotive AC compressors had been developed to meet the requirements of automotive market trend. The improvement results of this study, caused by refrigerant flow rate increase into AC compressor and dead volume decrease of AC compressor, showed that about 3.2% performance improvement, about 5.8% improvement in COP(Coefficient of Performance) and about 3 ℃ drop in discharge temperature under low speed conditions.
The test conditions for bench simulation test mode substituting the SC03 mode, the North America fuel economy certification mode with AC on condition, were developed through this study and the bench simulation test was performed with the torque sensor for the SC03 modes and vehicle test modes under various conditions. The test results showed that differences of compressor performance were about 9.8∼13.9% in the vehicle test and about 10.4∼13.5% in the bench simulation test under 12.7% difference of the compressor discharge displacement. The test results showed that about 2.0∼3.0% performance improvements of AC compressor in the calorimeter test stand brought about 1.2∼2.0% performance improvements in the vehicle cooling down test and about 5.0% decrease of AC compressor in power consumption in the calorimeter test stand caused about 1.0% decrease in vehicle fuel efficiency. Additionally about 12.5∼12.7% differences of AC compressor discharge displacement caused about 2.2∼2.8% decrease of fuel efficiency in vehicle under constant speed conditions.
Therefore, the results of this study on compressor characteristics can be useful not only for design standards regarding refrigerant passage sizes, leak rate and internal robust design of compressors but also for prediction of vehicle cooling down performance and fuel efficiency based on AC compressor performance. So the cost and time saving could be expected due to the reliable bench simulation test mode suggested in this study by substituting the SC03 mode which had tested with vehicles in CWT.