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Viewing 70801 to 70830 of 109759
1991-09-01
Technical Paper
912193
David Macdonald
In 1962 British and French Governments committed funds for the design, testing and production of a supersonic airliner. Fourteen were completed. These aircraft are currently in their sixteenth year of passenger service and, judged on their reliability, have carved out a niche in the air transport market. Behind this success lay the problems of maintaining a radically different aircraft that operates in a radically different environment.
1991-09-01
Technical Paper
912234
Salvatore Cezar Pais
This paper deals with a thrust generation method which can be applied to nuclear as well as chemical propulsion systems. It takes into consideration both incompressible and compress-ible flow cases, however both of these cases are based on one dimensional flow within an ideal rocket framework. In the case of constant area duct steady state flow the obtained Induced Thrust (IT) formula is: where p1 and p2 are opposing pressure fields and u* is a function of u2, p2 and u1 (u1 and u2 being opposing gas efflux velocities). For the compressible and incompressible flow fields, IT formulas are obtained but they are not as reliable. One feasible application for this launch-propulsion method is the Joined-Ship model. In this model the combustion chamber pressure within one space vehicle acts as the back pressure of the joined space vehicle and vice-versa.
1991-09-01
Technical Paper
912231
M. Hashish, J. Whalen
This paper addresses an experimental investigation on the feasibility of using abrasive-waterjets (AWJs) for the precision drilling of small-diameter holes in advanced aircraft engine components. These components are sprayed with ceramic thermal barrier coating (TBC), and the required holes are typically 0.025 inch in diameter with a drilling angle of 25°. The parameters of the AWJ were varied to study their effects on both quantitative and qualitative hole drilling parameters. The unique techniques of assisting the abrasive feed process, ramping the waterjet pressure during drilling, and varying the jet dwell time after piercing were effectively implemented to control hole quality and size. The results of the experiments indicate the accuracy and repeatability of the AWJ technique in meeting the air flow and hole size requirements. Production parts were drilled for prototype engine testing.
1991-09-01
Technical Paper
912002
Makoto Kobayakawa, Ryoji Takaki, Yoshifumi Kawakami, Frederick B. Metzger
Abstract Applicability of a numerical code to aerodynamic design of a Prop-Fan is established by precise agreement of numerical results with experimental data, i.e., not only measured integrated performance indices, such as power coefficient or net efficiency but also pressure distribution on the blade surface should agree well with computed results. For this purpose, an Euler Code using the Total Variation Diminishing scheme has been developed. Numerical calculations are performed with this scheme for the SR-7L Prop-Fan at the freestream Mach number 0.5 and 0.78. The computed power coefficient, CP = 1.46 at M∞ = 0.5 shows good agreement with experimental data. At this computed CP, the computed pressure distributions on the blade surfaces show good agreement with the experimental results. For the 0.78M∞ case the computed CP of 0.87 also shows good agreement with the experimental results and the computed pressure distributions are in general agreement with the experimental data.
1991-09-01
Technical Paper
912004
Gizo Hasegawa, Hiroyuki Nakagawa, Takashi Sato, Tomoari Nagashima
Using a higher order vortex panel method, three dimensional free wake analyses for a rotor in hover are carried out. The purpose of this paper is to propose new methods being able to incorporate wake deformations due to wake-ground interactions into performance predictions. Both rotors at isolated and at close proximity to arbitrary shaped ground surfaces are investigated. The blade is modeled as a lifting surface with one row of cells (equivalent to Weissinger's L model). The wake is divided into the adjoining, near and far regions. The ground is approximated by the quadrilateral panels. The first two regions of the wake are modeled by triangular shaped panels with linear vorticity distribution which are adopted by their flexibility for roll up deformations of the wake. A semi-infinite vortex cylinder with the constant radius is substituted for the far wake to avoid instabilities of the wake geometry.
1991-09-01
Technical Paper
912029
Yoshiyuki Sugiyama
An Increase in jet penetration due to the wall boundary layer is determined in the flow field including an aerodynamic interference between the wall boundary layer and the jet. The aerodynamic effect of the wall boundary layer is replaced by that of a secondary vortex filament resulting from vorticity in the wall boundary layer. A differential equation governing the increase in jet penetration is derived using the circulation around the secondary vortex filaments, its induced velocity and the empirical decay law of the jet axial velocity along the jet centerline. The circulation around the secondary vortex filament is estimated according to Hawthorne's theory (1)* and expressed in terms of aerodynamic characteristics of the wall boundary layer. A numerical example of the present analysis shows a fairly good agreement with the experiment. This indicates that the used vortex flow model simulates the real flow conditions well.
1991-09-01
Technical Paper
912032
Toyohiko Suzuki, Yoshitaka Ochiai, Seiichi Tanabe, Yuzuru Ohmori
Combustion of a liquid fuel spray distributed in a uniform stream was analyzed with a distributed source model. In this model, each fuel droplet of the spray is expressed mathematically by the moving source, of which the strength is to be determined by the relevant governing equations and boundary conditions. The main equation is an integral equation which expresses the inter- relation among strengths of fuel droplets in the spray. Given the assumptions of a uniform velocity of the stream and zero-relative velocity of fuel droplets, the spatial variation of the droplet radii can be expressed by a differential equation with respect to a spatial coordinate y. Thus, the set of coupled equations can be solved numerically and iteratively. Then nature of the distributed spray combustion in the convective flow is seen to be governed by two non-dimensional parameters, known to be group combustion numbers.
1991-09-01
Technical Paper
912039
Thomas L. Reynolds
This paper describes a multiphase technical study, currently under contract with the FAA Technical Center, that has defined two advanced inflight smoke/fire detection system approaches for commercial jet aircraft. Four specific areas are being studied; sensing, alerting, crew response and crew decision making. The objective of Phase I was to identify system concepts that would provide for accurate, timely, and complete guidance to the flight crew for their use in responding to inflight smoke and fire events within the pressurized fuselage. Phase II of this contract, currently in work, will result in the functional test and demonstration of the prototype system concepts defined in Phase I.
1991-09-01
Technical Paper
912180
G. A. Ganley
Abstract The Olympus 593 together with its reheat, primary nozzle and secondary nozzle systems was designed and developed jointly by Rolls-Royce in Britain and Snecma in France. The design objectives were met so that the Concorde aircraft still carries a full payload of 100 passengers between Europe and America. 600,000 hours of operational experience, over half at Mach 2.0, have shown the control philosophies adopted were correct and are showing that the most significant difference between civil subsonic and supersonic engines is the cruise at high inlet air temperatures which has produced some unexpected mechanical affects.
1991-09-01
Technical Paper
912192
E.B. Trubshaw
The certification of the Western world's first supersonic civil transport did not have the benefit of past experience as has been the case in the subsonic field. Supersonic experience was limited to military aircraft which possessed in the main a relatively short duration supersonic dash capability. Concorde has been in Airline service since 1976 and has built up over 150,000 hours of which over 112,000 are at supersonic speeds on a worldwide basis. This achievement came about following a flight development and certification programme covering approximately 5,500 hours over six and a half years. This wealth of experience creates a totally different scene to that existing at the time of Concorde's conception and many lessons are available for the next generation of supersonic civil transport.
1991-09-01
Technical Paper
912156
Thomas J. Yager
Abstract The capability of a runway pavement to rapidly drain water buildup during periods of precipitation is crucial to minimize tire hydroplaning potential and maintain adequate aircraft ground operational safety. Test results from instrumented aircraft, ground friction measuring vehicles, and NASA Langley's Aircraft Landing Dynamics Facility (ALDF) track have been summarized to indicate the adverse effects of pavement wetness conditions on tire friction performance. Water drainage measurements under a range of rainfall rates have been evaluated for several different runway surface treatments including the transversely grooved and longitudinally grinded concrete surfaces at the Space Shuttle Landing Facility (SLF) runway at NASA Kennedy Space Center in Florida. The major parameters influencing drainage rates and extent of flooding/drying conditions are identified.
1991-09-01
Technical Paper
911919
Anil Ananthakrishna
Abstract The present traffic and pollution situation in our large cities and the inefficient use of the internal combustion engine car in city traffic, has been for a long time the catalyst to develop specific city cars, which can reduce the burden on the environment and be more economical to operate. Several electric cars have been introduced in the past without success. The power/weight ratio of the present lead-acid batteries has been a limiting factor for the commercial success of an electric vehicle. In addition to this the high initial cost, limited range, and high operating cost have contributed to the low level of interest by the general public. This paper describes the development of a commercially viable electric car based on a range-extending battery system. This car is also designed to be utilised with quick-change battery modules.
1991-09-01
Technical Paper
911915
J.L. Sudworth, H. Böhm
Abstract Sodium nickel chloride batteries have been tested in electric cars over the past three years. Although the performance of the cars was satisfactory, reliability was inadequate and it became apparent that the cells needed to tolerate repeated discharges to 100% depth of discharge. A new cell design with an improved sodium electrode was developed and tests with 26 Volt modules of these cells have shown that it will tolerate hundreds of cycles to 100% depth of discharge. The capacity and resistance stability of the new cell design are described and the feasibility of rapid charging is discussed.
1991-09-01
Technical Paper
911917
J. Hampton Barnett, Harshad Tataria
The Electric Vehicle Test Facility (EVTF), operated by Electrotek Concepts, Inc., serves as a major research center to evaluate electric vehicles (EVs), batteries, and EV-component systems. The 9600 ft2 (890 m2) facility houses special test equipment and computer-controlled instrumentation which, with the adjoining one-mile (1.6 km) test track, is dedicated to EV testing. These research and testing activities have been primarily supported by the Electric Power Research Institute (EPRI) and the electric utility industry. Electric utility and consumer-related concerns were addressed in this effort. At present, the EVTF activities have been expanded to work with automotive and battery companies involved in introducing EVs in the 1998 time frame. Cooperative partnerships are being considered to assist EV development.
1991-09-01
Technical Paper
911775
Satoshi Ohkawa, Takashi Kuse, Nobuyuki Kawasaki, Akira Shibata, Masao Yamashita
From investigating the porosity and graphite effects on sintered bronze for wet clutch applications, it is clear that elasticity, as determined by the porosity and the graphite content, is important for both the friction coefficient and the power absorbing capacity. The apparent elastic modulus values, measured by a compression test of clutch disks, show a very good correlation with performances of various wet friction materials (sintered bronze, paper, graphitics and elastomerics) in both an inertia-brake type clutch testing machine and also on the full-size powershift transmission bench. The lower elastic modulus material has the higher friction coefficient and the better energy/power absorbing capacity. Effects of the material pores, the oil-groove patterns and also the material deterioration on friction performances and hot-spot size are discussed in conjunction with apparent elastic modulus.
1991-09-01
Technical Paper
912054
Masahiko Onda, Yasushi Morikawa
To tackle global environmental problems, the acquisition of plentiful and precise data is necessary, and a means of conducting long-lasting high-resolution measurements over broad areas is required. A feasibility study has been made on a high-altitude (about 20km), super-pressured, and helium-filled PLTA (Powered Lighter-Than-Air) vehicle as an ideal platform for environmental observation. It has a long service life and carries a larger payload than an artificial satellite. This PLTA platform, named HALROP (High Altitude Long Range Observational Platform), uses a solar-powered electric propulsion system to maintain its position in space against wind currents. The solar power is acquired from solar cells. For night use, solar energy is stored in regenerative fuel cells. This study examines energy balance and provides a structural analysis of the vehicle.
1991-09-01
Technical Paper
911944
Robert R. Wright, Thomas G. Carpenter, Frank H. Johnson, Randy Nelson
All-Terrain Vehicles, usually called ATVs, are small motorized vehicles operating on three, four, or five low-pressure, high flotation tires that are “designed” for off-road use on a variety of terrains. As the use of these ATVs increased through the 1980's, the number of accidents resulting in serious injuries and deaths associated with A N use increased dramatically. The U.S. Consumer Product Safety Commission (CPSC) along with other surveys have estimated that one out of every 25 ATVs being used will be involved in an accident requiring professional medical attention. These problems led to the federal government working out an agreement with the major manufacturers of these vehicles. One aspect of the agreement was that there would be safety and stability standards that all ATVs would have to meet to be sold in this country.
1991-09-01
Technical Paper
911883
P. Zagrodzki
Temperatures and thermal stresses in multiple disc clutches (brakes) are greatly affected by normal pressure distributions on particular friction surfaces. When the pressure distributions are non-uniform, the distributions of heat flux generated on friction surfaces are also non-uniform. This can result in high local temperatures and high thermal stresses. The pressure distributions depend on a number of design and material factors. They can also be subject to changes during the clutch engagement due to the thermal deformations. The paper presents a theoretical model of a multiple disc clutch (brake). Using this model, the initial distributions of normal pressure have been examinated as well as their changes which occur due to the thermal deformations. Then temperatures and stresses in the cross-sections of friction discs have been calculated.
1991-09-01
Technical Paper
911762
Maria E. Pettersson, Kenneth G. Weddfelt, Jan-Ove S. Palmberg
Abstract Noise emission is often considered to be one of the major drawbacks of fluid power systems. One of the main sources of noise is flow ripple caused by positive displacement pumps. This paper is concerned with the problems of modelling and measurement of flow ripple with emphasis on analyses with theoretical techniques. A simulation model of a piston pump has been used in this investigation. Simulation has proved to be a useful tool for optimization of the portplate geometry and for developing new methods to reduce pump flow ripple. Different conventional methods are compared with unconventional ones. A new method which gives very low flow ripple over a large operating range is included in this study.
1991-09-01
Technical Paper
912204
Paul R. Leckman
Abstract An Enhanced Vision System (EVS) displays sensor derived information to the pilot, usually on a Head Up Display (HUD). The use of at least one on-board sensor would allow the pilot to visualize the runway environment when conventional flight visibility would not permit this. The components of the system are integrated in a way that takes into account the specific task to be accomplished and the associated human factors. The technology for EVS appears to be available. There is a potential for EVS to provide added situational awareness for flight crews. One challenge is to determine whether EVS can be economically justified. However, its potential for improving situational awareness may outweigh any economic disadvantage. Airport capacity during fog conditions could be improved. Additionally, the pilot's ability to avoid runway incursions under night/low visibility conditions could be substantially improved.
1991-09-01
Technical Paper
911782
Edward A. Fritz, J.I. Case, William G. Switalski
: The Equipment Manufacturers Institute (EMI) sponsored a literature search conducted by Triodyne, Inc. which attempted to identify all “Operator Protective Zones” ever utilized in the world. This effort was intended to determine whether published information existed to define a more compact Operator Protective Zone than those of current SAE (ASAE) standards for possible utilization in developing a new standard for a more compact design of Rollover Protective Structures (ROPS) for small agricultural tractors. The research has led Triodyne to conclude that the Operator Protective Zones upon which the current SAE (ASAE) ROPS standards are based are the only substantiated zones available for possible application to small agricultural tractors.
1991-09-01
Technical Paper
911946
Mike Burleson, Al Bruton, Edward W. Karnes
Safety considerations in the operation of personal watercraft and related design concerns are discussed. Accident statistics, hazard analyses, and preliminary testing data have identified potential safety deficiencies and accident causation factors that require further analysis.
1991-09-01
Technical Paper
911805
Robert W. Burrahm, Jeff J. White, James N. Carroll
Recent legislation including the California Clean Air Act of 1988 and the Federal Clean Air Act Amendment of 1990 will regulate exhaust emissions from small utility, lawn, and garden equipment engines. In an attempt to gain as much understanding as possible in a short time, SwRI has conducted a series of tests to investigate the effectiveness of late 1960's automotive emission reduction technology on small engines. Experiments were conducted utilizing air injection into the exhaust, exhaust gas recirculation (EGR), and ignition timing changes. The test engine was a 4 stroke generator set engine rated 5.88 Kw at 3600 rpm. Results show these technologies to be very effective in reducing hydrocarbons (HC), oxides of nitrogen (NOx), and carbon monoxide (C0).
1991-09-01
Technical Paper
911723
F.V. Tinaut, A. Melgar, A.A. Rahman Ali
The present study has been performed in order to characterize the compact plate-type heat exchangers that are used to cool the lubricating oil of Internal Combustion Engines. During the work an evaluation model has been developed for water/engine-oil heat exchangers. The evaluation model uses experimental data such as coolant and oil flow rates and the heat exchanger inlet and outlet temperatures. Also a predictive model has been developed, based on the application of the fluid flow and heat transfer equations of the real heat exchanger geometry. This model permits the performance calculation of the heat exchangers in arbitrary conditions. Simultaneously an experimental facility has been projected and built for testing the heat exchangers. The test facility allows to fix oil and coolant flow rates and temperatures over a wide range.
1991-09-01
Technical Paper
911800
Paul E. Duffy
A small sample lot of Conrad type ball bearings fabricated of silicon nitride have been fatigue tested under full film liquid lubrication conditions. Analysis of the failed bearings points to a failure mechanism which is different than that of steel bearing fatigue. A failure model has been developed based on the static strength of the material, manufacturing process effects and basic contact mechanics. The failure mode found identifies one limitation of the use of ceramic bearings. The limitation is dictated by the tensile stresses produced in operation and the strength of the finished component. It was demonstrated that silicon nitride fails by mechanical fatigue when subject to high Hertzian contact stress. It must be clearly understood, however, that the high Hertzian contact stresses (above 350 k.s.i.) used in this test program are greater than those of recommended design practice. The bearing manufacturing, testing and failure analysis are discussed.
1991-09-01
Technical Paper
911772
Masaru Ogura
This report is concerned with the theory and experiment of reducing the exciting force in piston-crank mechanism by the using of an eccentric gear trains during in a non-uniform velocity balancer system. For the experiment, we desinged a special apparatus to measure the exciting force at X and Y directions, and the rolling moment M causing form crankshaft, in an unloaded single-cylinder diesel engine. The obtained results supported our theory, and were compared with that of a conventional engine, too.
1991-09-01
Technical Paper
911758
John H. Tanzer
Artificial intelligence (AI) is the branch of computer science committed to attaining and exceeding the intelligence of the human brain, primarily by innovative software technology. Following significant accomplishments in all phases of human endeavor are proof of its potential: medical diagnostics and treatments, military weapon and space technology, learning and teaching, plus manufacturing and expert systems, robotics, etc. The objective of this paper is to provide an overview of AI applications, tools and techniques and to assist and encourage renewed initiative in research, development and applications of AI enhanced expert systems and robotics for the benefit of our industry.
1991-09-01
Technical Paper
912229
Robert F. Handschuh, Robert C. Bill
The U.S. Army Aviation Systems Command (AVSCOM), through the Propulsion Directorate at NASA Lewis Research Center, has recently sponsored projects to advance the manufacturing process for spiral bevel gears. This type of gear is a critical component in rotary-wing propulsion systems. Two successfully completed contracted projects are described. The first project addresses the automated inspection of spiral bevel gears through the use of coordinate measuring machines. The second project entails the computer-numerical-control (CNC) conversion of a spiral bevel gear grinding machine that is used for all aerospace spiral bevel gears. The results of these projects are described with regard to the savings effected in manufacturing time.
1991-09-01
Technical Paper
911827
Jack Ambuel, Thomas S. Colvin, Kandiah Jeyapalan
A satellite-based positioning system is being developed to determine the location of farm equipment while working in the field. A satellite receiver mounted in a moving tractor or combine calculates position coordinates based on signals received from a selection of satellites in the Department of Defense Global Positioning System (GPS). The position coordinates are retrieved from the receiver by a computer and combined in a common data base with additional information collected by the computer such as yield, soil fertility, soil moisture, temperature, implement draft, and fuel consumption. There are a number of possible applications for this system. One is the automation of position information and data collection for research purposes. Comparison of results between years can be easily made. Another application is the optimized and automated application of manure, fertilizers and chemicals. Profits can be increased and environmental damage minimized.
1991-09-01
Technical Paper
911929
Katumasa Azami, Hidenori Hosoi, Masaaki Takahashi, Takeo Takahashi
Several field problems are anticipated with HFC-134a systems. To be evaluated and clarified are the impacts upon: compressors and systems of chlorine based solvents left in the system from flushing or parts cleaning; mixing in CFC-12; mixing the new lubricants with mineral oil; the effects of certain lubricants and HFC-134a's high hygroscopicity and others. The whole industry should share information and endeavor to maintain the reliability of the new systems from a service engineering standpoint. STARTING IN 1991 the ozone safe HFC-134a refrigerant is expected to replace the conventional CFC-12 in car air conditioning systems and in model years 1994-1995 the major portion of the market will be the new systems. The components/elements and parts used in the new air conditioning systems will embody different designs with new materials which are now considered to be compatible with the new refrigerant-lubricant mixtures.