Single Crankshaft Opposed Piston Heat Rejection Measurement and Simulation on High Power Density Engines for Future Ground Combat Vehicle Power Pack Configurations

This paper discusses inherent advantages and additional design changes that can be made to a single crankshaft opposed piston engine (SCOPE) in order to satisfy military engine heat rejection-to-power requirements of 0.45.

The paper starts off with a discussion of the currently demonstrated heat rejection to power levels being obtained with the commercial version of the SCOPE configuration. Here, it is seen that heat rejection-to-power ratios are approximately 0.69. Tests are ongoing and this value is considered preliminary in nature.

Analytical results are then presented that decompose where the heat is being generated - for the intake air system, the coolant system, and also the oil lubrication system. The model includes consideration of heat generated from the engines turbochargers, cylinders, pistons, and gear train. The model is anchored to measurements made with a commercial version of the SCOPE engine. Engine heat rejection results for this baseline configuration (experimentally measured and/or predicted values) are made for all of the critical heat rejection areas of interest, including a decomposition of heat rejection areas within the gear train.

The heat rejection model is then extended to an engine configurations of military interest – those satisfying the 0.45 heat generation to power ratio. To facilitate various options available, identification of potential reductions in various heat generating areas of the engine are reviewed, including identification of technology limitations in each areas. In every particular heat generating regime, various design options, features and considerations are described, and the down-selected configuration is selected

Finally, a SCOPE engine configuration is presented that satisfies military engine heat rejection-to-power ratio requirement of 0.45, while at the same time utilizing engine design and manufacturing technologies that are of relatively low development risk.

The paper highlights that SCOPE engines offer lower heat rejection than conventional V-shaped reciprocating engines, in addition to their inherent packaging efficiency and power density. Additionally, design modifications that improve the heat rejection-to-power ratio of the engine tend to be more advantageous for the SCOPE engine than a V-shaped engine, thereby resulting in the ability to meet military engine heat rejection requirements without the need to pursue high risk technologies or design concepts.