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Viewing 163861 to 163890 of 187885
1972-02-01
Technical Paper
720811
Curtis F. Vail
The effect of viscoelastic damping on transfer function characteristics of structures is discussed. Three types of viscoelastic damping treatments were examined: free layer, constrained layer, and constrained layer spaced from the neutral axis. Structures were tested with and without damping treatments for slow sweep and fast transient sweeps at two amplitude levels. The transfer functions were calculated and used for determining the effectiveness of the treatment for reducing the response. Analysis was performed for the modal characteristics, inherent damping, additive damping, and transfer functions. Correlation between the predicted and test transfer function magnitudes showed the acceptability of the analysis method.
1972-02-01
Technical Paper
720810
A. M. Ellison, W. E. Jones
A method is presented for predicting the modal damping of structures using a combination of analysis and tests of substructures. Damping characteristics of simple substructures and joints are determined by the test program, and analysis is used to predict the modal damping coefficients as a function of the peak kinetic energy of vibration in the mode. Both the magnitude and the form of the damping can be predicted before full-scale test hardware becomes available.
1972-02-01
Technical Paper
720813
Gary C. Hart, Jon D. Collins
Several methods are presented for developing proportional substructure damping matrices from modal test data. Examples demonstrate the significance of the nonuniqueness of the resulting proportional damping matrices. Several alternate modal synthesis procedures are presented for the systematic calculation of system modal damping from substructure damping information. The relative merits of these procedures are discussed, and one procedure is recommended.
1972-02-01
Technical Paper
720812
Gregg K. Hobbs
A brief discussion of the sources of damping is given and methods of mathematically modeling the liner sources of damping are discussed. It is shown that the most general linear model corresponds to a system that is linearly viscoelastic. The techniques applied in problem formulation are based on finite element models which utilize lumped masses. Transform and state space methods of solution are discussed and compared. Transient solutions for forcing functions of exponential order or less are given.
1972-02-01
Technical Paper
720807
W. F. Wilhelm
A reusable, high-performance, liquid-propellant rocket engine is being developed for the Space Shuttle Orbiter vehicle. The engine is a high-pressure design based on the staged combustion cycle. Control is accomplished with an electronic digital system. This controller accepts vehicle commands for start, shutdown, mixture ratio, and thrust level, plus providing appropriate signals to five major propellant valves: main fuel, main oxidizer, chamber coolant, and two preburner oxidizer valves. Many unique design features, such as regenerative cooling at high chamber pressure, a high-efficiency three-stage fuel pump, a dual-inlet oxidizer pump, and an electric control system, are incorporated to satisfy the life, performance, and reliability requirements of the Space Shuttle Orbiter Main Engine.
1972-02-01
Technical Paper
720806
Robert W. Polifka
The orbit maneuvering engines provide the propulsive thrust to increase or decrease the velocity of the space shuttle orbiter while in earth orbit. The design and operational philosophy of the shuttle vehicle and orbital maneuvering system are discussed along with the design characteristic and selection rational for the current baseline orbit maneuvering system. The need for long life and economic reusability are the new shuttle requirements which must be considered along with traditional factors such as performance, reliability, and weight. Critical development issues and potential alternate designs are also discussed.
1972-02-01
Technical Paper
720809
Robert Plunkett
Porcelain enamel coatings give substantial amounts of damping at temperatures between 400-800 C depending on the particular enamel. Suitably chosen enamels can reduce the vibration amplitude at elevated temperatures and increase the fatigue life at all temperatures for those structures subject to forced vibration at resonance. Particularly suitable applications are gas turbine blades, combustion chambers, and aerodynamically heated plates and shells.
1972-02-01
Technical Paper
720808
R. T. Goe
Previous large liquid-rocket engine check-out and maintenance operations were mostly manual, time consuming, and costly. Using Saturn experience and guided by airline practice, the Space Shuttle Orbiter Main Engine has been designed for rapid turnaround and simple, low-cost maintenance. A streamlined operational concept and the addition of specific design features for easy maintenance were the prime factors in this accomplishment.
1972-02-01
Technical Paper
720757
Harry E. Dietzmann, Karl J. Springer, Ralph C. Stahman
The use of diesel exhaust-emissions measurements to predict the observed odor from diesel engine exhaust has been studied, using a group of 31 trucks and buses powered by a variety of diesel engines. Regression analysis of gaseous emissions at a variety of conditions has resulted in equations for use in predicting odor. Acrolein, carbon dioxide, total hydrocarbons, selected light hydrocarbons, nitric oxide, carbon monoxide, and aliphatic aldehydes have been related to perceived odor. Some of these exhaust products are odorous and some are nonodorous yet indicative of the completeness of combustion. The empirical method, however, is somewhat less reliable than the observed odor based on a trained panel rating supra-threshold levels in terms of the PHS Quality-Intensity Odor Rating kit. In general, the greater variety of measurements and the fewer type of engines will increase odor prediction accuracy.
1972-02-01
Technical Paper
720756
Rudolf Pischinger, Wolfgang Cartellieri
Exhaust emission characteristics of a production automotive diesel engine were studied. The particular engine was chosen because it is being marketed with a prechamber as well as with a direct-injection combustion system and, in both configurations, either naturally aspirated or turbocharged. In addition, an aftercooler was fitted to the turbocharged direct-injection engine. Methods for reducing exhaust emissions are discussed. A brief survey is given of potential emission control by catalytic converter, exhaust recirculation, and LPG dual-fuel operation. Basic investigations, conducted on single-cylinder direct-injection (DI) engines are reported. It is concluded that direct injection is the most promising combustion system for low-emission commercial automotive diesel engines, particularly when turbocharged and aftercooled, and that this type of engine can satisfy the 1975 California standards.
1972-02-01
Technical Paper
720804
James B. Odom
The evolution of the booster system for the space shuttle is traced from the initial concepts employing liquid propellant,reusable boosters to the final selection of recoverable, solid rocket motors. The rationale associated with each of the several major decisions in the evolution process is discussed.
1972-02-01
Technical Paper
720758
S. G. Liddle, D. C. Sheridan, C. A. Amann
Concern over exhaust emissions has revived interest in the gas turbine as a powerplant for passenger cars, and concern over cost has stimulated interest in the single-shaft version of this engine. A novel transmission is needed to compensate for the inherently poor output characteristics of the single-shaft engine. The rated power and response time of the engine and the efficiency and power split of the transmission are shown to be the primary parameters influencing vehicle acceleration. Some factors affecting engine response time are reviewed. Transmission parameters are studied by considering standing-start accelerations of an automobile powered by a fixed-geometry single-shaft engine using versions of three of the many types of possible transmissions.
1972-02-01
Technical Paper
720605
Mark Sherbinsky
The heaviest class of intercity trucks is examined using the 1967 Census of Transportation to establish a representative sample of vehicles with truck-miles as the major delineator. Representative road types and vehicle loading factors are selected. Computer simulation of the vehicle and road is used to establish histograms of percent engine load versus engine RPM. The above is then combined with modal emission levels to allow projection on a weighted truck-mile basis, to the entire intercity population of this class vehicle. Heavy class is defined as over 26000 lb. GVW.
1972-02-01
Technical Paper
720606
Irving J. Rubin
A reduction in truck emissions in metropolitan areas can be accomplished through 1) the installation of pollution control devices, and 2) the more efficient utilization of trucks in the movement of goods. This paper discusses the government-mandated standards for truck emission control, and reviews the various methods employed or suggested for improving the efficiency of trucks -- such as the “off-hours” delivery system -- as well as alternative vehicle modes for moving goods. The conclusion is that improving the efficiency of trucks can reduce congestion -- and costs to both truckers and shippers -- and, at the same time, it also can reduce pollution.
1972-02-01
Technical Paper
720600
E. E. Hood,
The impact of the gas turbine on safety, reliability, and airline profitability; impact of the jet aircraft on international trade and development; new aircraft engines beget new and more productive airplanes; new technology has enhanced air transportation progress; and air transportation progress is benefitting the airlines; national interests, and all in our society, including the neighbors of our airports.
1972-02-01
Technical Paper
720604
Max Ephraim,
The diesel electric locomotive as a source of gaseous emissions is reviewed. Locomotive operation is outlined to provide an understanding of diesel engine application, operation, and controls. Methods of evaluating gaseous emissions are offered for consideration as industry standards. Present-day exhaust emission levels are presented. Specific recommendations are offered to the locomotive manufacturers, the railroads, and to governmental regulating bodies to effect improved exhaust emission levels.
1972-02-01
Technical Paper
720594
George W. James
In 1967 the airline industry embarked on a new forecasting project -- an Airport Demand Forecast Study to determine future traffic demands at individual airports as well as future nationwide air traffic. The study, involving many complex problems, has recently been completed. It will be used for airport planning purposes at major hubs across the country. The study forecasts demand far enough into the future to enable needed airport developments to be accomplished in time.
1972-02-01
Technical Paper
720598
Harry Pearson
The paper briefly reviews the evolution of modern aero engines and analyzes the forces which motivate continued technical development, especially the interaction with growth in traffic and aircraft size. The contribution of improved propulsion systems to the economics and regularity of air transport is examined, with particular reference to developments during the past decade. There is some discussion of the environmental factors, particularly noise, raised by civil aviation, the progress already made to deal with them, and the possibilities for the future. The overall benefits of powerplant technical development, particularly as they affect the general and traveling public, are summarized. Examples are drawn from both the United States and European scenes.
1972-02-01
Technical Paper
720523
Michel J. W. Coenen
This paper discusses how to turn a 3-point inertia belt into a passive seat-belt system. The main objectives of the program were to prove that it would be possible to use existing seatbelt systems to cope with future requirements for occupant restraints and that therefore existing anchor points (or at least the existing systems) could be used. The aim was to use only existing techniques in order to reach a high reliability standard and to design a system that also could meet current homologation requirements. A prototype was developed with a combination of a 3-point seat belt with running loop with an inertia reel at the central lap belt, in combination with loops around the webbing of the seat belt running along cable-operated tracks. The prototype met all the objectives.
1972-02-01
Technical Paper
720580
C. Dewey Havill, Louis J. Williams
An exploratory study has been conducted to assess the performance potential of buoyant airships and parawings in short-haul passenger transportation. Results show that such systems can be used effectively, from a performance standpoint, in a VTOL or STOL mode of operation. A supplementary assessment of potential applications of such vehicles is examined, with a brief look at economic factors and an examination of missions for which they might be effectively used.
1972-02-01
Technical Paper
720511
John C. Chipman, John Y. Chao, Ray M. Ingels, Roy G. Jewell, Wendell F. Deeter
The California Air Resources Board conducted an extensive field test program to evaluate a vehicle exhaust recirculation system for control of oxides of nitrogen. The system utilized hot exhaust gases from the crossover and included certain modifications to the carburetion, choke, and crank case ventilation system. It was tested on two fleets of automobiles equipped wtih California approved HC and CO emission control devices. The test program involved periodic measurements of exhaust emissions and fuel consumption. The effect of the system on vehicle drivability, engine deposits, wear, and oil deterioration was also studied. The Atlantic Richfield Company, under contract to the Air Resources Board, equipped the vehicles with the recirculation system and performed the final engine inspection.
1972-02-01
Technical Paper
720520
John L. Harned
Performance of packed bed type catalytic converters in controlling hydrocarbon (HC)-carbon monoxide (CO) mass emissions is investigated using a one-dimensional plug flow math model. Converter operation is explained, and the effects that some gas stream conditions and basic parameter values have on converter emission control performance during warmup are evaluated. It is shown that total mass emissions passed by the converter during warmup can be minimized by maintaining gas mass flow and HC-CO concentrations at low values. Converter warmup performance is highly sensitive to changes in bead diameter and catalyst kinetics, but it is relatively insensitive to changes in bed area/length ratio and bed void fraction. New information is presented dealing with the modeling of platinum kinetics, bead temperature stability, and mass and heat transfer j-factors for packed beds.
1972-02-01
Technical Paper
720518
C. Henault
Because of low nitrogen oxide emissions, a version of the Renault R17 TS equipped with a high-performance engine was selected for the American market. This paper discusses problems encountered in adapting a Bosch electronic fuel injection system to a 1600 cm3 engine to meet American standards up to 1974. The principal problems solved were those posed by intermediary operating speeds. This study also gives an idea of the pollution limits which can be obtained with an injection system which incorporates various important adjustment factors. Engine specifications are presented, as are decriptions of the electric regulation, electric and pneumatic cold-start, and fuel feeding circuits. The various modifications to the engine are also described.
1972-02-01
Technical Paper
720509
James G. Hansel
A wide range of air/fuel ratios and exhaust gas recycle rates were examined in an automotive test engine for the purpose of reducing NOx emissions to low levels. A minimum NOx level of 0.4 g/mile on the 1972 Federal Test Procedure was obtained at a rich A/F of 12 and a recycle rate of 25%. With this combination, the fuel consumption increased approximately 15% and the wide open throttle (WOT) power decreased about 30%. Combustion in the cylinders was good and the vehicle operated smoothly. Comparable results were not obtained with lean mixtures. The results of this study do not establish the feasibility of meeting the 1976 NOx standard with the rich mixture, high recycle technique. Further, the increased CO and HC emissions would have to be controlled by exhaust gas treatment.
1972-02-01
Technical Paper
720510
E. N. Cantwell, R. A. Hoffman, I. T. Rosenlund, S. W. Ross
Exhaust manifold thermal reactors, exhaust gas recirculation, exhaust particulate trapping systems, and appropriate engine adjustments have been combined to produce total emission control systems which reduce all gaseous and exhaust particulate emissions from passenger vehicles. The first generation system was developed to meet the former United States and State of California emission standards for 1975. Field service tests demonstrated that the emission standards were met, but unexpected operational problems were encountered. Solutions to these problems have been found. Second generation total emission control systems are being developed in an attempt to meet the current United States emission standards for 1975 - 1976. These systems in their present state of development produce very low exhaust emission levels; the hydrocarbons are well below the standards and the carbon monoxide and nitrogen oxide levels are quite close to the 1975 - 1976 standards.
1972-02-01
Technical Paper
720507
J. D. Shedlowsky
In its treatment of acoustical leaks in passenger car bodies, this paper considers the general principle of noise control in a passenger compartment, the concept of acoustical leaks, examples of such leaks, and design guidelines for acoustical isolation. The paper states that the basic problems can actually be designed into vehicles through lack of understanding of acoustical principle, and various examples are given in illustration. Remedies for some of these deficiences are also proposed. Finally, design principles formulated to eliminate acoustic leaks are presented.
1972-02-01
Technical Paper
720672
E. N. Cantwell, E. S. Jacobs, W. G. Kunz, V. E. Liberi
Exhaust particulate lead trapping systems and devices designed to reduce airborne lead emissions by 65 percent or more have been developed and tested on vehicles. Tests of up to 60,000 miles indicate that these devices should retain their effectiveness and last the lifetime of a passenger vehicle without maintenance. The traps reduced the total amount of lead emitted from production vehicles operated on leaded gasoline by 82 to 91 percent. They also reduced by 64 to 84 percent the amount of lead in the air after driving both production and trap-equipped vehicles through a vehicular tunnel. When a trapping system was combined with a gaseous emission control system, consisting of exhaust manifold thermal reactor and exhaust gas recirculation systems, the total lead emitted was reduced by 85 percent and the amount of lead found in the air of the vehicular tunnel was reduced by 71 percent when compared with production vehicles.
1972-02-01
Technical Paper
720670
Marc S. Newkirk, James L. Abel
International Materials undertook to develop an inherently low-polluting automobile, the “Boston Car,”* with two fixed design parameters: the use of an internal combustion engine and the use of gasoline fuel. On-board production of carbon dioxide-hydrogen mixtures to fuel the engine was the approach undertaken; gasoline was reacted with steam to produce a “reformed” fuel upstream from the engine. Initial efforts to develop an engine to burn the mixture revealed problems with respect to starting reliability and high rpm carburetor flashback. Starting reliability was achieved by providing accurate air/fuel ratios at cranking speeds. It was necessary to employ a spark distributor lacking any provisions for spark advance in order to guarantee elimination of flashback at advanced rpms. These modifications have resulted in extremely fine road performance from the test vehicle, comparable to the production model prior to modification.
1972-02-01
Technical Paper
720661
Robert U. Ayres
The basis for formulating so-called “uniform” emission standards for motor vehicles is examined and found to be inconsistent with the widely accepted principle that “the polluter should pay,” if consideration is given to the problems caused by pollution rather than the sources of emissions. Atmospheric pollution problems are geographically limited and also depend upon other variables such as time of day, and weather conditions. The major problems are associated with Southern California and other cities of the southwest, and congested urban areas. It is proposed that emissions standards should be made flexible in order to reflect these environmental variations, and thus to achieve the maximum environmental improvement for the least total cost to vehicle owners and users.
1972-02-01
Technical Paper
720644
E. J. Croke, K. G. Croke, J. E. Norco
The significance of the impact of transportation system characteristics on the urban quality has resulted in a need to evaluate certain transportation air quality-oriented policy statements regarding the effect of present efforts to reduce emissions from automobile operation or to design transportation systems that do not constitute a danger to air quality. The evaluation of these policies requires the integration of planning techniques from both transportation and environmental fields. The classical transportation system planning process involves a well-established sequence of data acquisition and systems analysis activities. Likewise, the regional air pollution planning procedures also depend on the use of a sequence of empirical models that require a substantial data base.

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