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A study has been undertaken to demonstrate the use and potential benefits of actively controlled coolant jets in a vehicle. Results have shown that active control of cooling jets has the potential to regulate the temperature of thermally critical areas of the cylinder head, in this case the exhaust valve bridge. In addition the temperature gradient across the head from the exhaust valves to the inlet valves is directly influenced. These capabilities offer improved control of the combustion process and enhanced durability. Furthermore the system allows heat to be rejected at much lower overall coolant flow rates than with a conventional arrangement. The technique relies on an adequate supply of coolant at a lower temperature than that within the engine and on the availability of a suitable measurement technology within the thermally critical region. Unlike passive precision cooling the active jets allow optimization of the cooling at all engine speed / load points.

An experimental investigation, using a Design of Experiments approach, has sought to quantify the potential CO2 savings that could be made by the electrification of certain mechanical devices as part of the Front End Auxiliary Drive (FEAD) on a 2.4 litre DI diesel engine. The experiments considered the electrification of the cooling fan; power assisted steering system, and the vacuum pump. A number of different build configurations have been evaluated on a dynamic testbed over the New European Drive Cycle (NEDC). The overall conclusion is that the move towards electrification of the devices listed would result in a 6-7% saving in CO2 over the NEDC. These benefits however, need to be considered alongside other issues such as increased on-cost, more control complexity and reliability implications of adopting electrically driven devices.

A proof-of-concept study has been undertaken to demonstrate the use and potential benefits of actively controlled coolant jets in an IC engine cooling gallery simulator. Results have shown that substantial reductions in coolant volumes are possible and that the control of the liquid/metal surface temperature can be achieved within +/- 0.2°C in response to transient heat flux conditions.

Non-air-breathing diesel engine systems have, and continue to be developed for underwater applications. When the engine is operated in such an environment the intake oxidant mixture consists of a combination of oxygen and recycled exhaust gas. The latter will contain combustion gaseous products and may also include additional inert diluents. Since its initial conception in the late nineteenth century, a major problem encountered in the operation of the recycle diesel engine has been the detrimental effect of the recirculated exhaust carbon dioxide upon the engine's performance. To avoid this problem exhaust gas scrubbing systems have been developed to remove the carbon dioxide from the exhaust gases. In addition, inert gases such as argon and helium have been added to the non-air mixture to improve its thermodynamic and transport properties and hence engine performance.

The findings presented in this paper are part of a long term project aimed at raising the science of heat transfer in internal combustion engine cooling galleries. Initial work has been undertaken by the authors and an experimental facility is able to simulate different sizes of coolant passages. External heat is applied and data for the forced convective, nucleate boiling and transition or critical heat flux (CHF) regimes has been obtained. The results highlighted in this paper attempt to quantify the effects of cooling passage surface roughness on the nucleate boiling regime. Tests have been conducted using aluminium test pieces with surface finishes described as smooth, intermediate and as-cast. It has been found that the as-cast surface increases the heat flux density in the nucleate boiling region over that of the smooth and intermediate surfaces.

Although successful “precision cooled” prototype engines have been demonstrated, the design of most mainstream coolant jackets has evolved only cautiously, and lacked this major change in approach. The achievements and potential of precision cooling are reviewed, along with an extension into nucleate boiling based heat transfer. It is demonstrated that ideas for advanced “external” cooling systems with low flowrates are in fact extremely compatible with the “internal” precision engine cooling philosophy, and in combination promise even larger benefits.