Reduction of cooling fan usage through control applications in automotive air-conditioning systems

摘要

This paper examines the findings of a prototype automotive fan control strategy that was developed and subsequently tested in a climatically controlled wind tunnel. Vehicle under-bonnet cooling is provided by two basic components as shown in figure 1, mass flow rate of ram-air and air drawn from engine cooling fan. At low vehicle speeds, the fan is crucial in ensuring adequate under-bonnet airflow to generate cooling of radiator, air conditioning (A/C) condenser, inter-cooler and also to ensure adequate component heat protection. Common industry practice is to engage electric cooling fans at all times of A/C use. It was hypothesized that at certain vehicle speeds and ambient temperatures, the ram air alone would be sufficient to meet the A/C requirements without any perceived degradation in performance. Therefore this study investigated the feasibility of cycling the cooling fan according to vehicle speed and A/C system line pressure/temperature conditions. A prototype control strategy was developed, with variable parameters, and a program of tests was undertaken in a climatically controlled, solar simulated, dynamometer wind tunnel. This confirmed that the fan could be switched off at various speeds and ambient temperatures, yielding a reduction of 60% of fan duty cycle on a standard Northern European Drive Cycle. By analysing real-world customer usage profiles, it was estimated that disengaging the fan above approximately 30kph during A/C use could have a significant positive effect on the fuel consumption of most driving profiles without the need to install costly hardware upgrades.