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An advanced low heat rejection engine concept has been selected based on a trade-off between thermal insulating performance and available technology. The engine concept heat rejection performance is limited by available ring-liner tribology and requires cylinder liner cooling to control the piston top ring reversal temperature. This engine concept is composed of a titanium piston, headface plate and cylinder liner insert with thermal barrier coatings. Monolithic zirconia valve seat inserts, and thermal barrier coated valves and intake-exhaust ports complete the insulation package. The tribological system is composed of chrome oxide coated cylinder, M2 steel top piston ring, M2 steel valve guides, and an advanced polyol ester class lubricant.

In our prior analytical work concerning a finite element methodology for thermal stress analysis of minimum cooled low heat rejection (LHR) engine cylinder heads, a very fine mesh with strict aspect ratio and element density criteria was used. In this current study, these criteria were relaxed and two other finite element models with different element densities were used to solve the same thermal stress problem. The thermal and stress results of the relaxed models are compared to those of the earlier very fine mesh results. It is the aim of this paper to show in a semi-quantified manner, how mesh density can affect thermal stress solutions in LHR engine heads. Hopefully this will enable other analysts working in this area to make some judgement on mesh density before starting an actual modelling effort, resulting in a savings of time and manpower resources.

In common with other owners and operators of large fleets of vehicles, the U.S. Army is faced with a major maintenance task. A significant part of this task is the correct and timely diagnosis of the vehicle faults which cause down time and those which can propagate into secondary, and usually more serious, damage. The Army, of course, has two operational situations which differ in type and degree from those of commercial fleets. First, the duty cycle for Army vehicles is less predictable and instant availability is essential. The second is that Army vehicles are armored, shielded and waterproofed (fordable) to an extent that test point access is severely limited in comparison to commercial vehicles. To grapple with this situation, the U.S.

The requirements for Army vehicular gas turbines are reviewed and various concepts are compared. A novel boundary-layer ballistic type separator specifically designed for gas turbines demonstrates high efficiency at low pressure drop and low specific size.