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Design of a Feedback Controlled Thermostat for a Vehicle Cooling System
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Abstract
In traditional liquid cooled internal combustion engine systems, the coolant temperature is controlled by a thermostat which governs the coolant flow rate to the radiator. The thermostat is effectively a directional control valve in which the spool displacement is used to direct flow to the radiator. The coolant temperature is primarily a function of four parameters, namely radiator and thermostat characteristics, coolant flow rate and ambient temperature. By employing closed-loop feedback, the coolant temperature can be controlled according to environmental conditions. To achieve this goal the overall system must be correctly designed. That is the issue discussed in this paper.
The increasing use of simulation for both circuit and component analysis in the automtive industry has come about due to the requirement for acceptable transient as well as steady state system performance. The computer simulation package Bathfp, originally developed at the Fluid Power Centre, University of Bath, U.K., to simulate hydraulic systems, has been extended to incorporate models of components in engine cooling systems. Utilities are provided which allow a model of a complicated system or component to be built up from its elements, which can be introduced to the model library of components. Component models enable the individual effects on overall system behaviour to be assessed to a high degree of accuracy.
This paper describes the use of computer simulation to assess the capabilities of the closed loop themostat system using PID control to ensure precise and stable operation. Parametric variations are made in the simulation to obtain optimum performance and identify likely problems.
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Tomlinson, S. and Burrows, C., "Design of a Feedback Controlled Thermostat for a Vehicle Cooling System," SAE Technical Paper 961823, 1996, https://doi.org/10.4271/961823.Also In
References
- Shayler, PJ Christian, SJ Ma, T ‘A Model for the Investigation of Temperature, Heat Flow and Friction Characteristics During Engine Warm-Up’ Proceedings Vehicle Thermal Management Systems . SAE International Conference March-April 1993 Columbus, Ohio, U.S.A. 667 676
- Veshagh, A. Chen, C. ‘A Computer Model for Thermofluid Analysis of Engine Warm-Up Process’ Proceedings Vehicle Thermal Management Systems , SAE International Conference March -April 1993 Columbus, Ohio, U.S.A. 677 687
- Chiang, EC. Keller, JR. ‘The Thermostat Characteristics and Its Effect on Low-Flow Engine Cooling System Performance’ S.A.E International 41st Annual Earthmoving Industry Conference Peoria, Illinois, U.S.A. April 1990 1 7
- Richards CW Tilley DG Tomlinson SP Burrows CR ‘Type-Insensitive Codes for the Simulation of Fluid Power Systems’ Proc ASME WAM Paper No. 90-WA/FPST-6 Dallas, Texas. USA 1990 1 6
- Richards, CW Tilley, DG. Tomlinson, SP. Burrows, CR. ‘Bath ƒp - A Second Generation Package for Fluid Power Systems’ 9th International Symposium on Fluid Power Cambridge, UK 1990 315 322
- Tomlinson SP Hogan PA Burrows CR ‘Computer Simulation of Vehicle Cooling Systems’ ASME Int ME , ASME Int ME '94 Congress & Exposition ASME Chicago, Illinois. USA 1994