Advanced Turboprop Engines for Long Endurance Naval Patrol Aircraft

Long endurance naval patrol aircraft of the future will require more efficient advanced turboprop powerplants. Engines used in this kind of application will have performance requirements emphasizing prolonged endurance and very low specific fuel consumption for cruise and part-power loiter operation. Regenerative, regenerative/intercooled and advanced conventional cycle screening studies were carried out to select the cycle pressure ratio and turbine temperature for each type, considering the effects on installed performance and weight. Design and cycle choices were studied in each engine category including recuperator types, effectiveness, pressure drop, bypass bleed and variable area turbine nozzle. The engine characteristics of each type were then compared using a representative mission. The advanced conventional engine showed the largest potential, the regenerative second and the regenerative/intercooled the least promise for lower installed fuel consumption and improved mission performance.

Regenerated Marine Gas Turbines: Part II — Regenerator Technology and Heat Exchanger Sizing

Analytical studies are currently being conducted by the David Taylor Naval Ship R&D Center to assess the suitability of regenerative-cycle and intercooled, regenerative-cycle gas turbines for naval applications. This paper is the second part of a two-part paper which discusses results of initial investigations to identify attractive engine concepts based on existing turbomachinery and to consider the regenerator technology required to develop these engine concepts. Part I of the paper analyzed existing and next generation engines for performance improvement. Part II includes: definitions of performance parameters such as effectiveness and pressure drop, a discussion of regenerator types, and comments on regenerator materials, life, maintenance, and fouling. Tradeoffs between size, weight, and performance of plate-fin recuperators are examined using two of the hypothetical engines from Part I as examples. Results are compared for several different recuperator matrices to illustrate the effects of air-side and gas-side fin density and plate spacing on size, weight, and performance.

A Method for Determining the Main Requirements of Outlet Gas Temperature Profile of Marine Gas Turbine Combustors

Taking account of the marine gas turbine operation features, the author has chosen the hot corrosion peak temperature of materials as the guide vane material limiting temperature while evaluating the overall temperature distribution factor. Along with the blade cooling effectiveness a safety margin factor has been introduced during its evaluation. The gas temperature distribution along blade height is assumed to satisfy the condition that approximately equal safety factor in respect of strength prevails along blade height. Once the gas radial temperature profile becomes known, the radial temperature distribution factor can be readily determined.

Next Generation Turboprop Gearboxes

A new generation of fuel-efficient turboprop propulsion systems is under consideration now that fuel is a significant portion of the direct operating cost of aircraft. Systems in the 5000- to 15,000-hp (3730- to 11,185-kW) range that use conventional propellers or the new propfan are being studied. Reduction gearing for this next generation of turboprops is of significant interest due to new requirements for cruise speed life, and reliability. Detroit Diesel Allison’s past experience with the T56 family of turboprop reduction gearboxes is recounted. Probable requirements of the next generation of reduction gearboxes are discussed since new requirements for gearboxes combined with past experience should determine the profile of the next generation of gearboxes. A discussion of gearbox general arrangement and its impact on airframe installation is included, along with comments on reduction ratio, gear arrangement, accessory drives, reliability goals, and probable technology needs.

The AGT101 Advanced Automotive Gas Turbine

The Garrett/Ford Advanced Gas Turbine Powertrain System Development Project, authorized under NASA Contract DEN3-167, is sponsored by and is part of the United States Department of Energy Gas Turbine Highway Vehicle System Program. Program effort is oriented at providing the United States automotive industry the technology base necessary to produce gas turbine powertrains competitive for automotive applications having: (1) reduced fuel consumption, (2) multi-fuel capability, and (3) low emissions. The AGT101 powertrain is a 74.6 kW (100 hp), regenerated single-shaft gas turbine engine operating at a maximum turbine inlet temperature of 1644 K (2500 °F), coupled to a split differential gearbox and Ford automatic overdrive production transmission. The gas turbine engine has a single-stage centrifugal compressor and a single-stage radial inflow turbine mounted on a common shaft. Maximum rotor speed is 10,472 rad/sec (100,000 rpm). All high-temperature components, including the turbine rotor, are ceramic. AGT101 powertrain development has been initiated, with testing completed on many aerothermodynamic components in dedicated test rigs and start of Mod I, Build 1 engine testing.

The Influence of Engine Characteristics on Patrol Aircraft Life Cycle Cost Optimization

A conceptual design study has been conducted for an all-new, land-based patrol aircraft for the U.S. Navy. The selected propulsion system was a conceptual high-speed turboprop. An antisubmarine warfare mission was chosen for the design flight profile. Probable peacetime utilization was postulated so that the engine duty cycle could be estimated. Aircraft designs were optimized for minimum takeoff gross weight (TOGW) and for minimum life cycle cost (LCC). It was shown that the aircraft performance requirements and design constraints bound the optimization process so tightly that the same point design is obtained for both TOGW and LCC criteria. The contribution of the engine costs to the overall life cycle costs was examined. The sensitivity of the aircraft optimization to the engine characteristics — specific fuel consumption (SFC), length, diameter, and cost — was analyzed. It was determined that SFC is the most significant engine characteristic.

CFD Technology for Propulsion Installation Design-Forecast for the 80’s

Competition for the world aerospace market will continue to be intense through this decade. The aircraft industry will use CFD in this period to gain an advantageous market position by reducing the cost and risk of achieving viable configurations and removing the test derived data base as a design constraint. Use of CFD for design implies that parametric analysis will reduce reliance on parametric testing as the basis for configuration selection. Industry will increasingly emphasize development of the technology necessary to support this. Most of the industry will follow a zonal modeling strategy and take advantage of the large vector processing computers now commercially available. Areas which will pace the development of the necessary flow analysis technology include turbulence modeling, numerical error assessment and mesh generation, and experiments for code validation.

Application of High Bypass Turbofan Computer Simulation to Flight and Test Data Processing

This paper describes the computer program used to compare gas turbine engine flight and static test results with a predicted standard engine computer simulation model. The program is conceived not only for a final presentation of engine performance, but also as a research tool to further analyze the validity of measurements and the assumptions used in data reduction.

Experience Gained in Operation of the GTS Finnjet Gas Turbines and Improvements in Ship’s Fuel Economy

This paper briefly describes the use of gas turbines of the GTS Finnjet, matters concerned with maintenance and repair as a result of four years’ experience (45,000 engine hours) in service, using light distillate fuel. The research and modifications required for changeover to blended residual fuel oils in gas turbines are then reviewed, as well as the first experiences (4,000 engine hours) in using the blended fuel oils during the summer of 1981. Finally we describe how the fuel economy was further improved by installing a diesel-electric machinery on the car deck to be used for manoeuvring and low season journeys.

F-14 Inlet Development Experience

This paper reviews the F-14 inlet design and discusses the wind tunnel and flight test results of investigations that can contribute to more advanced inlet designs.