TURBINE ENGINE SCIENCE AND TECHNOLOGY OVERVIEW

Until 2005, U.S. turbine engine research was guided by the Integrated High Performance Turbine Engine Technology (IHPTET) program. IHPTET was initiated in 1987 with very aggressive technical goals, essentially achieving a 100 percent improvement in turbine engine capability based on a 1987 state-of-the-art baseline engine by the turn of the century. IHPTET featured specific goals in each of three engine classes—namely, turbofan/turbojet, turboprop/turboshaft, and expendable engines. For the turbofan class, the primary goal of IHPTET was to double the engine thrust to weight ratio (T/W). Although IHPTET made significant progress toward its goals, the program focused on low-bypass-ratio, fighter/attack-class engines, and payoffs for large-bypass-ratio, transport-class engines occurred primarily as a spin-off from the fighter/attack application. Thrust-specific fuel consumption (TSFC) was regarded as important, but not as critical as T/W.

With the conclusion of IHPTET in 2005, the Versatile Affordable Advanced Turbine Engines (VAATE) program became the nation’s premier turbine engine S&T program.2 VAATE has been structured to take advantage of the features that made IHPTET successful. These include coordination between DoD, NASA, academia, and industry, with the Federal Aviation Administration (FAA) and DOE joining the effort as well. The breadth of this integrated team allows the VAATE program to coordinate gas turbine technology development strategy at the national level while leveraging funding of the constituent organizations. A fundamental goal of VAATE is to advance overall air system capability with a capability-focused investment strategy. The scope of VAATE is thus significantly greater than the rotating machinery focus of IHPTET and will encompass the entire propulsion/power system, including inlet/nozzle integration, thermal and power management, integrated controls, and prognostics and health management. This approach requires optimization of integrated propulsion capability at the aircraft system level, rather than optimization of just the engine turbomachinery. To this end, the major aircraft manufacturers are full partners on the VAATE industry team.

The VAATE program goal is to realize a 10-fold improvement in the affordable capability of a turbine-engine-based propulsion system. Here, “affordable capability” is defined as the ratio of propulsion system capability to cost. Capability in this context measures technical performance parameters, including thrust, weight, and fuel consumption. Cost is the total cost of ownership and includes development, procurement, and life-cycle maintenance cost (excluding fuel). These improvements are to be realized relative to a baseline representative of year 2000 state-of-the-art systems.

Specific measurable technical improvements, such as thrust, weight, TSFC, and life-cycle cost, are called “goal factors” in the VAATE lexicon. The overall VAATE goal, expressed as a capability-to-cost index (CCI), is defined by the following function of the goal factors, where each factor is expressed as a ratio between the subject and a contractor-chosen reference system:

While each VAATE contractor is free to determine the specific combination of goal factors and product application that comprise its offering to achieve the CCI goal, it is important to note that the fundamental physics-based turbine engine technology barriers, such as temperature, pressure ratio, and

2

For additional information on the VAATE program, please see the American Institute of Aeronautics and Astronautics (AIAA) VAATE position paper at http://pdf.aiaa.org//downloads/publicpolicypositionpapers//VAATE.pdf. Last accessed on September 11, 2006.



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