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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’.

This paper presents a new methodology for analytically evaluating the natural frequencies and mode shape of a turbomachinery blade in an environment where friction phenomenon occurs. The blades analyzed in this study are unshrouded and located in the high-pressure turbine found in turbofan engines, and in the compressor turbine found in turboprop engines. The goal of this method is to correctly predict the modal parameters of the blade in order to determine whether there will be any resonance in the running range of the turbomachinery, and to more accurately predict the stresses at the blade-disc interface. This study was performed using ANSYS® contact elements. After comparison, the analytical results were found to agree with the experimental results. A convergence study was also performed, and it was found that only the friction coefficient and the surface contact stiffness had a considerable effect on the natural frequencies and mode shape convergence.

The two major factors that affect auxiliary power system design decisions are: the working fluid to be used, and vehicle mission requirements. It has been found that optimum turbine designs will be similar for the two working fluids (hydrazine or hydrogen-oxygen) considered for the shuttle orbiter system due to the constraints imposed by geometrical and mechanical design limitations. As a consequence, variations in power level and/or working fluid selection can be efficiently accommodated by relatively minor modifications to turbine nozzle design. Analytical techniques for optimization of turbine aerodynamic design parameters have been developed. These techniques can be extended to include transient-state simulation and design optimization of the other system components, including the turbine controller, in a manner similar to that used for development of control systems for multi-spool fan-jet engines.

Considerable operational experience has been acquired in South America, Africa, Europe, Southeast Asia, and in other remote areas in STOL type aircraft operating from extremely short, primitive, unimproved fields. This type operation not only makes certain special demands of the engine, but also exposes it to a rather hostile environment. The engine is subjected to all types of foreign object ingestion, as well as the fine sand and dust that is stirred up by propeller reversing. This paper describes this type of operation, emphasizing those aspects which make life difficult for the engine. Solutions to some of these special problems are described, as well as activities now in process seeking further improvement.

This technical paper discusses the evolution of turbopumps designed for U.S. rocket engines, starting with the Thor, Jupiter, and Atlas missiles, which were developed in the 1950s; the F-1 and J-2 engines, which were developed in the 1960s for the Saturn V vehicle to put man on the moon; and the Space Shuttle Main Engine (SSME), which was developed in the 1970s for the United States' first reusable space vehicle. Technology development in the 1980s that will influence the design of turbopumps for the National Launch System (NLS), the National Aero-Space Plane (NASP), and Orbital Transport Vehicles (OTV) are also discussed.

The civil aircraft market frequently employs propulsion systems originally developed and qualified for military aircraft applications. When this occurs, the civil sector benefits greatly from the lessons learned during the military engine development and qualification process. This paper presents the unique test experiences and lessons learned during development of the T406-AD-400 turboshaft engine that the GMA2100 turboprop, GMA3007 turbofan, and GMA1107 turboshaft engines will profit from for years to come. Some of these valuable T406 test experiences include: 1) development of engine attitude capabilities, 2) integration with a fly-by-wire control system, 3) incorporation of flight test experience into the engine design, and 4) utilization of unique test facilities.

The turbulent impinging jet flows associated with vertical or short take-off and landing (VTOL) aircraft hovering in ground effect can have a critical effect on aircraft performance, and they are modeled very poorly by existing models. Three flow phenomena representative of VTOL ground effects flows, the upwash fountain, the ground vortex, and the impingement zone of a round jet, are considered. Extensions to the k-ϵ model are presented which are designed to account for streamline curvature, large scale mixing, and anisotropy. The extensions significantly improve the model's ability to predict some aspects of these flows. Requirements for further model development are identified.

Enhanced turbulence in an upwash fountain and fluid/acoustic resonance of an impinging axisymmetric jet are investigated by numerical simulations of the mean flow and the largest scales of the unsteady fluid motion. In the planar upwash, the simulated shear stress and spreading rate are three times greater than in a normal jet and are in good agreement with experimental data. Reynolds-stress transport mechanisms which lead to the enhanced turbulence are discussed, and a qualitative description of the large scale turbulent motions is proposed. A model for the pressure-strain term is determined to be a major source of error in Reynolds-stress transport modeling of the upwash. In an axisymmetric impinging jet at Mj = 0.9, resonant-like behavior with elevated levels of pressure fluctuations and dominance of a single frequency of vortex generation are observed. Vortex stretching is observed to be critical to the generation of noise in the impingement zone.

The Turret Head Fastening System is an enhancement of current three position “C-frame” wing riveting machines. It was designed and built by Boeing as a fully instrumented research machine in 1991 for the 777 Airplane, and as a potential retrofit package for conventional drill, rivet, shave wing assembly machines. It was designed to automatically install rivets and bolts and perform the required hole preparation prior to fastener installation. In its current form, it will clamp a panel; and then as the fastener requires, drill, coldwork, ream, countersink the hole; inspect the hole; apply sealant when required; install threaded fasteners or rivets; torque the nut, swage the collar or upset the rivet as required; shave the rivet to ensure flushness; and finally unclamp the part - all within the current working envelope of a drill, rivet shave machine. Currently, switching from rivets to bolts requires a 5 minute tool change.

About 20 years ago, the existence of a new miniature turbojet engine inspired an imaginative designer to create a small unmanned aircraft for reconnaissance missions. This marked the beginning of a new era of turbojet development. Visionary designers predicted that miniature engines would someday perform missions comparable to those of larger unmanned aircraft. The WR2/WR24 series of engines has grown from the original 50-lb thrust to over 200-lb thrust. Unique challenges were encountered during the early period as the engine developers found themselves pioneering a specialized field. Innovative concepts were necessary to maintain simplicity, light weight and high performance.

This paper describes the second government-conducted, piloted flight simulation of the Grumman Design 698 V/STOL (vertical and short takeoff and landing) aircraft. Emphasis is on the aircraft's handling qualities as rated by various NASA, Navy, and GAC pilots with flight experience ranging from CTOL (conventional takeoff and landing) to V/STOL aircraft. The Design 698 had been modified to resolve the flight problems that were of most concern to the pilots in the first investigation (Phase I). Those problems included an adverse nonminimum phase (NMP) acceleration response in both the longitudinal and lateral axes, a large thrust-response lag, and adverse ground effects. The adverse NMP acceleration is an attribute of the vertical vanes (a Grumman patent) positioned in the fan exhaust flow.