A Hydraulic Actuated Thermal Management System For Large Displacement Engine Cooling Systems

The performance of automotive cooling systems can be improved by replacing the traditional mechanically driven radiator fan and water pump assemblies with computer controlled components. The introduction of electric servo-motors to drive the cooling components can improve temperature tracking, which should increase fuel efficiency and decrease tailpipe emissions. However, the power requirement for these electric motors increases with greater cooling demands if the radiator surface area remains constrained. For heavy-duty applications, where engines are subjected to significant cooling loads, electric motors may become impractical due to their increased size and power requirements; in these situations, hydraulic-based components are advantageous due to their high power density. The off-road equipment industry currently uses hydraulic radiator fan drives for cooling applications, while the coolant pump remains mechanically driven. Therefore, an opportunity exists to integrate the radiator fan and coolant pump into hydraulic circuits to actively meet cooling demands. In this research project, an automotive thermal management system, which features a computer controlled hydraulically actuated fan and coolant pump, was investigated. A series of analytical mathematical models were derived for the hydraulic and thermal system components. An experimental test bench was constructed, which implements a hydraulic based radiator fan and water pump, as well as electric immersion heaters to simulate the heat of engine combustion. The test bench was used to validate the mathematical models and study the proposed cooling system's ability to regulate engine temperature. Classical control methods have been applied to control the coolant temperatures by integrating the temperature, shaft speed, and hydraulic pressure feedback information. Further, the performance of two types of hydraulic flow control valves has been studied to offer design engineers insight into actuator behavior. The dynamic hydraulic and thermal system models displayed good correlation with data obtained from the experimental test bench (steady-state errors below 1.6%). Additionally, the experimental system demonstrated excellent temperature tracking results (maximum 0.20¡K steady-state set point deviation) when using servo-solenoid valves to control the speed of the hydraulic motor driven radiator fan and water pump. However, when using the more cost effective solenoid poppet valves, the system exhibited limited temperature tracking abilities (maximum 2.48¡K steady-state set point deviation). Still, each valve displayed minimal power usage (by the pump and fan motors) with the servo valves consuming on average 58-160 Watts and the poppet valves consuming on average 66-128 Watts. The hydraulic actuated thermal management system has the ability to effectively regulate engine temperatures while offering the potential for power minimization to increase fuel efficiency and reduce emissions. Despite their higher cost, servo-solenoid hydraulic control valves may be a good choice for controlling actuator speeds and regulating engine temperatures. Solenoid poppet valves offer a lower cost alternative to the servo-solenoid valves, but temperature tracking performance may be sacrificed. To study the power saving potential of hydraulic based thermal management systems, future experiments should include on-vehicle comparisons of the traditional and hydraulic based thermal management approaches.