US Army Tank Automotive Command Engine Program

Dr. Walter Bryzik

U.S. Army Tank-Automotive Command

ABSTRACT:

Future military vehicles possess requirements which necessitate aggressive research and development in a number of advanced technology areas. Military vehicle requirements in areas such as improved compactness, decreased weight, reduced cooling system requirements, improved fuel economy, upgraded performance, enhanced survivability, reduced maintenance, improved multifuel characteristics, and reduced life cycle costs are strong drivers of advanced component development thrusts .

Within the propulsion systems area, engine technology comprises one of the most critical categories of payoff for application to future generations of Army combat and tactical vehicles. A number of engine types are continually considered for military vehicle application; however, our current engine thrusts are concentrated within the advanced diesel and gas turbine areas. In addition, other promising government and industrial programs which address advanced engine systems with relevance to military vehicles are closely monitored by the Army.

Because of the established thrusts of this conference, emphasis during this briefing will be applied to advanced diesel engine technology. Having been pioneered by TACOM, low heat rejection "adiabatic type" engines form a critical building block for future military propulsion systems over a wide range of power levels and vehicle applications. Examples of past, present, and projected work in the adiabatic diesel area by TACOM will be covered. Representative examples of current activities in this area include: (1) a 600 hp engine demonstrator for possible M2 Bradley Fighting Vehicle use, (2) an early adiabatic technology spinoff for application within the M109 Howitzer vehicle, (3) evaluation of low heat rejection technology for military truck application, and (4) developments for application to future classes of main battle tanks.

Technology barriers in the areas of (1) high temperature tribology, (2) insulated materials, with emphasis on technology voids, in the advanced coatings area, and (3) designing with ceramic materials from performance and stress limitation standpoints are particularly critical. Future advances in the adiabatic diesel engine area are directly tied to removing these types of technical barriers. Discussion of goals and current efforts in these areas will be covered .

INTRODUCTION :

The U.S. Army Tank-Automotive Command (TACOM) conducts research, development, and acquisition programs on a wide variety of tactical and combat vehicle types. The spectrum of possible engines for use in these vehicles is very broad (Figure 1). Available resources for the research and development (R&D) of candidate engines, however, are far more limited and further, not all the possibilities are equally promising at any given time. Consequently, there is a need for a. strategy by which TACOM can more effectively direct its R&D resources to those programs which will provide the greatest benefit to the overall effectiveness of the Department of Defense (DoD). Through a weighted study of performance and cost considerations, TACOM devieloped the following R&D strategy (Figure 2). Below 500 hp, because of the lower cost and readily available commercial engines, the Army will use commercial base engines. However, in some cases, the Army must develop modification kits in order to meet DoD goals of high efficiency and multifuel capability. In the 500-1000 hp range, one might use either a highly modified engine or a military designed engine. In the over-1000 hp range, compact commercial engines for vehicle application are nonexistent, and the Army must develop unique military engines for main battle tank application. Combat vehicle engines are required to operate over wide ranges of performance/environment including operation: (1) from -6OF to 120F ambients, (2) within deep water fording conditions, (3) within environments of severe dust, mud, snow, and ice, (4) at altitudes to 15000 ft, (5) at a 60% slope condition, (6) with minimum detectability (i.e., noise, smoke, and IR signature), and (7) under severe shock load and vibration conditions. Combat vehicles which possess advanced military engines strive to produce characteristics which enhance: (1) survivability, (2) mobility and agility, (3) range, (4) energy conservation, and (5) multifuel capability. Advanced military engines which contribute to advanced vehicle performance possess technical goals such as: (1) increased power density, (2) improved fuel economy, (3) better RAM-D, and (4) better reliability and maintainability. All performance goals are weighted against cost goals which include: (1) increased commonality of engines, (2) exploitation of commercial engines and tooling, (3) lower operation and support, and (4) increased NATO rationalization, standardization, and interoperability. The performance/cost tradeoffs innerent to prioritizing military engine R&D are continually assessed by the Army as R&D tasks are selected for pursuit.

ADIABATIC ENGINE OVERVIEW:

Because of the thrusts of this workshop, an emphasis on advanced (adiabatic) diesel engine technology will be made.

An adiabatic engine is one in which no heat is added or subtracted during a thermodynamic process. Obviously, a true adiabatic engine with zero heat loss is not possible. However, a 50% to 60% reduction of heat loss can be achieved with the use of advanced ceramic materials.

The problems of ceramic material reliability and cost continue to be extremely significant. Designing with ceramic/metal Interfaces over the load and speed range of the engine remains a difficult obstacle to overcome. High temperature tribology, including friction, wear and lubrication, remains a hurdle to successful implementation of adiabatic engine concepts. Volumetric efficiency penalties of the high

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