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For the gas turbine to find acceptance in the hybrid electric automotive market its major features must be dominated by the following considerations, low cost, high performance, low emissions, compact size and high reliability. Not meeting the first two criteria has been nemesis of earlier attempts to introduce the gas turbine for automotive service. With emphasis on the design simplicity for low cost and high performance, this paper addresses design considerations for the major components, and overall turbogenerator configuration. Initially all metallic engines will be introduced in hybrid electric vehicles, but their high cost will likely preclude them from the high volume commercial market. To match or better the performance and cost of advanced automotive piston engines, the success of the very small turbogenerator is viewed as being dependent upon the use of ceramic components in the hot-end, including the turbine, combustor, recuperator and ducts.

Current gas turbine auxiliary power units (APUs) for aircraft main engine starting and secondary power operation are configured with pneumatic and electric links, and in some applications with a direct shaft power link. Respective examples are the pneumatic/electric link used in the S-70B helicopter and the shaft power link in the FSX fighter aircraft. Future high performance aircraft will require more compact and lighter weight APUs. These APUs will require higher thermal efficiency and durable self-sufficient secondary power equipment, capable of reliable faster starting over a wider aircraft operating range. Gas turbine auxiliary power design configurations and technology requirements to meet these objectives are examined here for both commercial and military aircraft applications.

Future fighters will require more compact, lighter weight, small gas turbine auxiliary power units (APUs) capable of faster starting, and operation, up to altitudes of 50,000 ft. The US Air Force is currently supporting an Advanced Components Auxiliary Power Unit (ACAPU) research program to demonstrate the technologies that will be required to accomplish projected secondary power requirements for these advanced fighters. The requirements of the ACAPU Program represent a challenging task requiring significant technical advancements over the current state-of-the-art, prominent among which are: Small high heat release high altitude airbreathing combustors. High temperature monolithic ceramic and metallic small turbines. Capability to operate, and transition from non-airbreathing to airbreathing modes. This paper discusses these challenging requirements and establishes technology paths to match and exceed the required goals.

Advanced military fixed and rotary wing aircraft will require more compact, lighter weight small gas turbine auxiliary power units (APU's) and jet fuel starters (JFS), capable of faster starting and delivering high specific power outputs over wider operating envelopes. APU start system weights can be a significant fraction of the total installed APU weight, especially if fast starts are demanded under sub-Arctic environments. It is shown that both start system weight, and rotor containment armor weight are proportional to the product of rotational speed squared and rotating assembly inertia. Significant weight savings are therefore feasible with rotating assemblies using lower density materials such as ceramics and composites. This paper discusses the results of analytical studies supported by current development efforts and research paths to implement fast start technology for small gas turbine APU's.

This paper discusses the results of analytical studies supported by current development efforts and research paths to implement fast start technology for small gas turbine APU's, using non-metallic rotor components. APU start system weights can be a significant fraction of the total installed APU weight, especially if fast starts are demanded under sub-Arctic environments. It is shown that both start system weight, and rotor containment armor weight are proportional to the product of rotational speed squared and rotating assembly inertia. Significant weight savings are therefore feasible with rotating assemblies using lower density materials such as ceramics and composites. Recent tests are described at the authors affiliation wherein a modified T20 small gas turbine was accelerated from zero to 100% speed in 2 1/2 seconds.

Emergency standby generator systems require rapid start characteristics capable of providing on-line operation within 10 seconds under a wide range of environmental conditions. This paper describes the design and development of a fast start, air impingement system for a 200-kW, single-shaft, gas turbine generator set. The conventional electric start system was replaced by a high pressure, air start system which reduced the total start-to-load time from 21 to 9 seconds.

A study was conducted to assess the feasibility of an advanced technology High Pressure Intercooled Turbine (HIPIT) engine for prime propulsion applications. A cycle performance analysis was conducted for a hypothetical HIPIT gas turbine sized to deliver 1000 hp output with and without a reheat combustor. Selection of candidate designs with an overall compressor pressure ratio of 41.7 were predicted to have respective specific fuel consumptions of 0.358, and 0.434 lb/hp.hr with corresponding weights of 503 lb., and 374 lb. Three conceptual HIPIT engine preliminary mechanical design configurations were studied, and part load performance characteristics of the HIPIT are also presented. As a result of the high pressure ratio, reheating was predicted to provide a power boost of 35%, ideal for emergency power demands.

During the development of the Solar Titan T-62, small gas turbine engine, for the U.S. Navy, a two-shaft version was performance tested incorporating a unique turbine configuration in which the exducer portion of the radial inflow turbine was employed as a nozzleless free power turbine. This paper reviews the development of this interesting small gas turbine and presents the performance results obtained while operating the engine over a range of compressor and power turbine speeds.