Date of Award

8-2007

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Wagner, John

Committee Member

Dawson , Darren

Committee Member

Mocko , Gregory

Abstract

The automotive cooling system has unrealized potential to improve internal combustion engine performance through enhanced coolant temperature control and reduced parasitic losses. Advanced automotive thermal management systems use controllable actuators (e.g., smart thermostat valve, variable speed water pump, and electric radiator fan) in place of conventional mechanical cooling system components to improve engine temperature tracking over most operating ranges. To optimize advanced cooling system performance, the electro-mechanical actuators must work in harmony to control engine temperature. The design and placement of cooling components should also be considered when attempting to maximize the performance.
In this research project, two distinct vehicle thermal management issues were explored. First, a set of nonlinear control architectures were proposed for transient temperature tracking while attempting to minimize overall cooling component power consumption. Representative numerical and experimental results have been discussed to demonstrate the functionality of the thermal management system in accurately tracking prescribed temperature profiles and minimizing electrical power usage. Second, four different thermostat configurations have been analyzed to investigate engine warm-up behaviors and thermostat valve operations. The configurations considered include factory, two-way valve, three-way valve, and no valve. In both studies, experimental testing was conducted on a steam-based thermal bench to simulate engine combustion events and examine the effectiveness of each valve configuration and control designs. A series of four real time thermal management controllers (backstepping robust, robust, normal radiator, and adaptive) were developed. Although they performed similarly in regulating coolant temperature, the backstepping robust control algorithm had the best performance when compared to the others. The test results demonstrate that in the normal radiator operation, steady state temperature errors may be reduced to less then 0.2¡K while consuming an average instantaneous power of 19.334 watts. The backstepping robust control had similar temperature tracking with the lowest overall instantaneous power consumption of 16.449 watts. Results for the thermostat valve study demonstrate that a three-way valve configuration provides optimal performance for engine warm-up, temperature tracking and instantaneous power consumption at 363.9 seconds, 0.175¡K, and 24.31 watts, respectively. In contrast, the factory wax-based thermostat with emulated mechanical actuators configuration never reached its operating temperature and consumed nearly four times the instantaneous power at 109.37 watts. Some recommendations for future work include in-vehicle and dynamometer testing of both the control algorithm and actuator design simultaneously.

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