Search Results

This paper describes the technical approach and development of methodologies used to conduct design trade studies from a Life Cycle Cost standpoint. A discussion of computer program capability is followed by a general discussion of several engine design trade studies. The potential for influencing engine design using a Life Cycle Cost methodology is emphasized.

Aircraft turbine engine development is requiring more and more spool data to be recorded during testing. This data, which normally consists of thermocouple and strain gage type signals, demands so many channels of quality transmission as to preclude bulky and costly telemetry devices. Miniature slip ring capsule assemblies, originally developed for inertial navigation equipment, have been adapted and used in turbine applications at speeds in excess of 30,000 revolutions per minute. These slip ring and brush contacts are characterized by low resistance variation or other electrical interference. The principal adaptation required to achieve these life times is the provision of an adequate coolant/lubricant supply.

An analysis was conducted on a total of 106,000 turbojet and turbofan engines procured by the United States Air Force to ascertain if an aircraft turbine engine's cost can be effectively correlated to its technical performance. Results indicate that such technical parameters are not valid and other factors such as military situation, economic conditions, and procurement situation should be investigated.

Delivery of high quality fuels to commercial turbine engine aircraft may become more critical for supersonic transport operation. This paper presents high temperature stability test results on current aviation turbine fuel samples taken from refineries and airports throughout the world. Transportation methods involve combinations of tanker, barge, multiproduct pipeline, and truck movements. Data show that, through the application of proper handling techniques, fuels can be transported from refinery to aircraft, through complex distribution systems, with no significant loss in thermal stability. Data also indicate that current aviation turbine fuels are well above the minimum thermal stability specification limits for present subsonic jet aircraft.

Impacts of mission-related requirements on design of the J402-CA-400 missile propulsion turbojet engine are reviewed. Small-engine cost scaling rationale is presented in relation to engine thrust and functional requirements. The application of current casting technology toward achieving low cost is reviewed.

Some of the trends in gas turbine technology are traced with two central themes. Materials and process technology is seen to be the major contributor to past advancements and often fails to receive the credit which is due. And, second, projections are made of the major future technology steps which will continue the historic fast pace of advancement in aircraft propulsion.

Analytical predictions and laboratory measurements were made for the relative total temperature experienced at the tip diameter of a radial-inflow turbine used in an air turbine starter (ATS). The predictions showed that at freerun conditions the blade tip temperature would be significantly higher than the turbine inlet temperature. Tests to confirm this prediction were performed on an ATS modified to accept an optical pyrometer. The pyrometer was focused on the suction side of the blade at the tip radius. Blade temperature measurements conducted at the maximum attainable speed of the ATS verified the prediction to be within the error of the pyrometer measuring system.

The search for clean, compact, cost effective energy sources isn't new. In fact it is as old as humanity. Over the past decade AlliedSignal has focused its attention developing TurboGenerator™ Power Systems that can be used in industrial, automotive and aerospace applications, AlliedSignal's creation was inspired by meshing its best aerospace technology with its high-volume manufacturing capability. The TurboGenerator™ Power System was first developed as an electric power and water heating cogeneration system for the US Gas Research Institute. The technology next found its way into an under armor APU installed in US army tanks including being tested on the US Army's main battle tank, the M1A1. From there, the technology was applied to hybrid electric vehicles in the US with the Department of Energy and Ford and in France with Renault and Peugeot.

Many advantages can be realized by utilization of direct bleed air from the engine exhaust-driven turbosupercharger for pressurization of the cabin on buisness and utility aircraft powered with piston engines. Combining cabin supercharging and engine supercharging from the same compressor included as part of the engine package provides compactness and simplicity which leads to low cost and light weight.

The Turboelectric Distributed Propulsion (TeDP) concept uses gas turbine engines as prime movers for generators whose electrical power is used to drive motors and propulsors. For this NASA N3-X study, the motors, generators, and DC transmission lines are superconducting, and the power electronics and circuit breakers are cryogenic to maximize efficiency and increase power density of all associated components. Some of the protection challenges of a superconducting DC network are discussed such as low natural damping, superconducting and quenched states, and fast fault response time. For a given TeDP electrical system architecture with fixed power ratings, solid-state circuit breakers combined with superconducting fault-current limiters are examined with current-source control to limit and interrupt the fault current.

This paper reports the results of a study, sponsored by the NASA-Ames Advanced Concepts and Missions Division, of the applicability of small turbofan engines to general-aviation airplanes. Because of its high overall propulsion system efficiency, the turbofan engine is now being chosen for most military and commercial airplanes. To evaluate the turbofan's further applicability to smaller general-aviation airplanes, NASA-Ames and AiResearch have performed a study to establish engine and engine/airplane performance, weight, size, and cost interrelationships, and to evaluate the effects of specific engine noise constraints. The methods whereby these interrelationships and effects were determined, and the results of synthesis and sensitivity analyses are described. In addition to engine cost, engine performance quality was found to be a very important determinant of airplane size and resultant price and operating cost.

A concept for obtaining substantial amounts of shaft power from conventional two-spool turbofan engines will be introduced. The concept shows promise of alternatively providing rotor drive power and cruise thrust from the same engine for composite (stowed rotor) helicopter applications. The effects of varying several engine design features, including bypass ratio, compressor split, and variable geometry, on the amount of power available will be explored. Data on a specific engine will be used to investigate the installation, performance, and control characteristics of the engine in relation to the requirements of a typical composite helicopter.

The aircraft jet engine is one of the most complex multivariable systems with multiple inputs and multiple outputs. To attempt to optimize control functions or to address diagnostic problems, a detailed knowledge of all jet engine design parameters and performances is required. Although jet engines have been around for almost a century, there are only a few companies in the world presently designing and manufacturing them; as such these companies possess detailed knowledge of all relevant design characteristics and performance parameters. In the event where jet engine technical details are unknown, or only a few of them are known from manufacturer’s catalogues, the challenge becomes how to calculate and extrapolate critical performance parameters based on only fuel flow, jet exhaust temperature and total thrust.

Aircraft hydraulic systems have progressed from simple to complex, reliable systems, and in the future, with the Mach 3 aircraft, will be called upon to perform even more tasks. A review of past accomplishments, with a presentation of areas where progress is needed is examined in this paper.

SOME of the aerodynamic and mechanical problems of jet engines designed for supersonic flight speeds are discussed in this paper. The aerodynamic problems considered include the required range of operation of the compressor, the thermal efficiency of the cycle, the inlet-engine airflow match, and jet nozzle design. Structural difficulties due to high operating pressures and temperatures and the bearing and lube problems arising from high temperatures are also presented.

Many papers have been written showing that Computational Fluid Dynamics (CFD) codes can yield results that match experimental data. These papers are presenting results which are post-diction. By this it is meant that the CFD results were obtained after the experimental data was acquired. The true test of the predictive capability of a CFD code is being able to predict what will be observed prior to the test being run. In particular predicting the aero-performance of the initial build of a turbomachine whose aero design parameters lie outside the range of previous machinery. This paper addresses our ability to successful execute such simulations and also of equal importance calling attention to sensitivities of aero performance parameters to geometrical features as well as poorly understood inflow and outflow leakages. Thus the title ‘Turbomachinery Aero Design; Getting It Right the First Time’.