Abstract
A novel approach is proposed for precise control of two-phase spray evaporative cooling for thermal management of road vehicle internal combustion (IC) engines. A reduced-order plant model is first constructed by combining published spray evaporative cooling correlations with approximate governing heat transfer equations appropriate for IC engine thermal management. Control requirements are specified to allow several objectives to be met simultaneously under different load conditions. A control system is proposed and modeled in abstract form to achieve spray evaporative cooling of a gasoline engine, with simplifying assumptions made about the characteristics of the coolant pump, spray nozzle, and condenser. The system effectiveness is tested by simulation to establish its ability to meet key requirements, particularly concerned with precision control during transients resulting from rapid engine load variation. The results confirm the robustness of the proposed control strategy in accurately tracking a specified temperature profile at various constant load conditions, and also in the presence of realistic transient load variation.
Highlights
The development of new cooling strategies across a range of different application areas has resulted in a high degree of functionality for both component hardware and cooling systems
The focus of this paper is to find an appropriate control strategy to realise the full benefits of spray evaporative cooling for combustion engines that will mainly be used for automotive vehicle propulsion in the light-duty sector
A new control structure is proposed for the thermal management of road vehicle internal combustion engines using spray evaporative cooling
Summary
The development of new cooling strategies across a range of different application areas has resulted in a high degree of functionality for both component hardware and cooling systems. In the late 1980s, detailed studies on two-phase spray cooling were undertaken to understand and establish the effects on heat transfer of droplet size and velocity, mass flow rate, injector nozzle geometry, and the amount of sub-cooling [13,14,15,16,17] It was in this period that a maximum heat flux of around 12 MW/m2 was shown to be achievable with ‘superheating’ of only 20 C (where here the term ‘superheat’ refers to the difference between the temperature of the target surface and the coolant saturation temperature). Rybicki and Mudawar [36] undertook experimental studies to assess the effects of spray orientation on cooling performance, developing general correlations for single-phase heat transfer, nucleate boiling, and the critical heat flux They showed that regulation of spray mass flow rate, and Sauter mean diameter, are the key hydrodynamic parameters that influence spray cooling performance. The objective of the paper is to confirm the potential of the proposed cooling control methodology for spray evaporative cooling of highly-boosted automotive engines
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