Search Results

With the big gains in automobile fuel economy already accomplished, primarily with off-shelf technology, further improvements above that expected by further downsizing will now require advanced technology. One area in which advancing the state of the art may not only benefit fuel economy but preserve drive-ability is in the fluid dynamic performance of torque converters. While lockup clutches may preclude the need for higher converter efficiency, improved performance in the primary gears where lockup is inhibited would still benefit fuel economy. The gains, however, would be less, but driveability would be improved by the higher coupling efficiency. Detailed fluid dynamic investigations were performed on a three-element torque converter. These investigations were based on computer solutions that have been successfully applied in the design of gas turbines. Using a numerical solution, surface velocities were computed along the reactor blade based on a two-dimensional flow field.

This paper discusses current powertrain matching methodology and its applications. Modular computer programs, which model each component of the vehicle/powertrain system, simulate the vehicle over specified driving cycles to project fuel economy and performance. Fuel economy opportunities due to better powertrain matching are discussed, including optimum engine sizing, torque converter matching, transmission gear ratio spacing and shift scheduling, axle ratio and vehicle weight effect. An emission projection technique utilizing time weighted engine speed/load points generated either by experiment or by analytical models is used to quantify fuel economy/emissions trade-offs.

In developing high speed swirl supported direct injection diesel engines it has been a general experience that different engine results (performance, smoke and emission) may be obtained when using different intake port designs, although the swirl numbers (stationary flow test rig) of the different ports were identical. Therefore, an in-cylinder flow investigation under motoring conditions using hot wire anemometry was performed for three different inlet port designs having the same swirl number. Special emphasis was drawn on the engine design parameters being as close as possible to reality. Thus, the flow investigation and the engine tests were carried out at a typical compression ratio of 18 : 1 using a standard combustion bowl in the piston as well as produceable inlet ports. All flow measurements were carried out under motoring conditions covering the speed range from 1100 to 2400 rpm.

The lower efficiency of the indirect-injection diesel engine, with respect to the direct injection type, is due to additional heat transfer from the combustion chamber, gas pumping between chambers, later injection timing and a different burning rate schedule. The paper describes a project to isolate and quantify these reasons for low efficiencies, using a mathematical model, supported by experimental verification. The model is based on a two-zone system (main and pre-chamber), with component models for heat transfer, gas flow through the passage etc. Experimentally derived heat release schedules in main and pre-chamber are used. It is shown that for a 0.1 m bore engine, with a Ricardo Comet Vb pre-chamber, the different burning rate schedule is the major contribution to the difference in efficiency, with injection timing and gas pumping being the least significant.

A continuously variable transmission with an overall ratio of 6 may be worked out on a purely hydrostatic basis. High power to weight ratio hydraulic pump and motors can be designed to avoid bulk and weight penalty. Mass production can be used. Materials and manufacturing processes are not more sophisticated than in conventional automobile manufacturing. Although lower than in gear transmission, efficiency of the hydrostatic transmission is suitable for automobile use.

Starting from a classification of car transmissions and from the manufacturers requirements, especially for fuel savings, the potential advantages of continuously variable transmissions permitting to associate low engine RPM with high vehicle speed, are shown. The control of the engine, transmission and clutch to reach a given optimum, is explained. Here are given results of simulation or testing of vehicles equipped with a Renault hydrostatic prototype transmission, a 2-mode hydromechanical transmission and a Van Doorne prototype Transmatic. Highway fuel economy trends are quantified in case of substitution of the conventional S.I. engine for Diesel and/or turbocharged engines.

The more detailed the performance specifications for diesel engine are defined, the more difficult is the task to find the best possible compromise in applying a fuel injection system. This paper outlines in detail the strategy, how the objectives can be achieved within a reasonable time frame. The application of this strategy is demonstrated using actual results of a study based on optimization of exhaust emissions and fuel economy.

The design, finite element analysis and fabrication of graphite fiber reinforced plastic (GrFRP) for the body of the 1979 Ford LTD concept vehicle is described in Part I. One-hundred and four (104) steel body-in-white parts, weighing 423 lbs., were replaced by forty-one (41) GrFRP parts, weighing 160 lbs., for a 62% reduction in weight. The floor and body side panels represent some of the largest and most complex GrFRP automotive parts produced to date. The methodology and analysis used in developing the graphite composite lay-up design of the front end for the concept vehicle is outlined in Part II. This assembly of GrFRP components weighs 30 lbs., compared with 95 lbs. for the steel counterparts, and represents a 68% weight reduction.

Light duty diesels are often criticised for their poor specific power but boosting can be used to improve the situation. An exercise was carried out in which the performance of a naturally aspirated diesel car was compared with identical vehicles fitted with turbocharged and Comprex® boosted engines. The measures necessary to apply the two boosting systems to the engines are described and the test bed performance obtained is shown for each case. Standard vehicle tests were made with each system and the performance, fuel consumption, noise and emissions results are compared.

Experimental data are presented to show how diesel combustion systems respond to increase of fuel injection rate. Concepts of a fuel spray entrainment parameter, a maximum useful injection rate, and a condition termed ‘impingement’ are introduced to correlate and interpret widely differing responses. Best possible smoke and BSFC values in swirl type direct injection engines are obtained for injection rates 15% to 33% higher than normal values, but in practice lower rates must be used to satisfy emissions and other requirements. Engines with a high swirl rate and impingement give a superior ‘retardability’ for normal injection rates. Computer model calculations also show that there is a maximum useful injection rate and explain the relative fuel economies for different diesel combustion systems.

Experimental or observed rolling resistance data can be utilized to develop an empirical model that accurately depicts tire rolling resistance as a function of load and pressure over a wide range of load and pressure variations. This method allows the development of a graphical expression (carpet plot) or mathematical expression (computer modeled) to depict rolling resistance on three “control tires.” When the graphical or computer modeled systems are combined with a basic control tire correlation concept, a rather accurate inter-test facility prediction system does not have to rely on the sometimes inaccurate correction equations developed from theoretical modeling techniques.

A TECHNIQUE using an exponential least squares fit to analyze the behavior of measured nonsteady-state rolling resistance data and to compute the equilibrium rolling resistance force is discussed. Raw data are filtered analytically to reduce amplitude fluctuations prior to applying the technique. The method has been applied to rolling resistance tests conducted at the Calspan Tire Research Facility on tires in a free-rolling straight-ahead condition, under constant velocity and load. The use of the prediction technique is demonstrated for 12 passenger car tires that were tested under equilibrium conditions.

The U.S. Postal Service operates approximately 400 electric vehicles; predominantly AM General DJ-5E vehicles with a 1300-pound (590 kilogram), 3.22 cubic foot (9 x 10-2 cubic meter), 54-volt Gould propulsion battery. A number of the vehicles were assigned to delivery routes in low ambient temperatures which affected battery performance. The field installation of foil-faced insulation on in-service batteries maintained a 15°F (-9.5°C) to 18°F (-7.75°C) higher electrolyte temperature than unwrapped batteries exposed to 15°F (-9.5°C) ambient temperatures. Overnight “cold-soak” in 15°F (9.5°C) ambient temperature did not significantly reduce battery capacity because of the heat retained after completion of the charging cycle. Weekend “cold-soak” in 15°F (-9.5°C) ambient temperature, however, reduced battery capacity such that the vehicles could not complete assigned routes.

A formula is developed for computing the energy loss per unit distance (or the “rolling loss”) of tires operating under transient conditions. The formula is applied to two transient test schedules - a warm-up test with constant speed and zero torque (free-rolling), and an urban driving test with rapidly varying speeds and braking/driving torques. Test results indicate that the average rolling loss during warm-up is 9%, and during urban driving, 26 to 47% higher than the steady-state rolling loss. Equipment problems associated with transient testing are indicated.

The performance, reliability and maintenance and running costs of 62 battery electric delivery vans, supplied by three manufacturers, in daily use in the Greater London area are being assessed over a three year period in comparison with closely equivalent conventional vehicles on similar duties. The primary purpose is to obtain independent operational experience covering a wide variety of suitable applications over an extended period and provide reliable factual information about the performance of the vehicles in normal daily use with typical loads and drivers. Information of value to operators, the industry and Government will be produced.

ENEL, the Italian Electricity Board, has launched extensive programs of research, development and demonstration in the field of battery-powered vehicles, as the widespread use of electric vehicles should have a positive effect on the energy picture and the environment. Moreover, overnight battery recharging would contribute to the levelling of the electrical load -profile. Possible near-term applications of electric vehicles have already been pinpointed within the framework of the activities of ENEL and other important Italian utilities. Electric vans have been or are being developed in co-operation with Italian manufacturers. More than 50 electric vehicles of different types have been already assigned to ENEL operational units for demonstration purposes. Laboratory and on-the-road tests are planned to improve the vehicle and battery performance.

The developmental and operational experience with a foil air bearing in the 58,500 rpm gas generator of the Chrysler Upgraded automotive gas turbine is presented. Simulator work encompassed mating the 500°F air foil with oil-lubricated foil bearings, which then evolved into the final air bearing - rigid oil bearing engine system. Over two years of testing in engines and cars has shown the foil air bearing to have the performance requirements. Work on foil material and coating life problems is discussed. The potential of the bearing to meet the 1200°F and low power loss needs of future engines and current technology support work is presented.

The emerging national effort to commercialize electric vehicles (EVs) has significant potential for impact on utility load curves and distribution feeder systems. With the implementation of national energy goals, utilities recognize the need to identify the interactions between large-scale use of EVs and utility operations. Since utilities will have to provide the needed energy and “live with the impact”, it is appropriate and desirable that utilities participate actively in the national effort to accelerate evaluation and introduction of EVs. This paper discusses the Electric Power Research Institute (EPRI)/Tennessee Valley Authority (TVA) demonstration program, describing the initial testing and evaluation of non-prototype EVs in a real-world environment, the demonstration design, and finally the data acquisition and reporting plans.

Elimination of oil from the hot section of the engine, very low running losses and potential cost reductions are incentives to develop air bearings for the high speed rotors of automotive gas turbines. Low air bearing stiffness, start-stop wear and high starting torque are design challenges in this application. This paper outlines analytical and experimental programs undertaken by the Power Systems Department of the General Motors Research Laboratories to evaluate air bearing usage in vehicular gas turbines. Air bearing operation has been demonstrated in engine dynamometer tests. A better understanding of the many factors which affect the performance of cantilevered-leaf air bearings has been realized through extensive rotor dynamics rig testing coupled with development of bearing analysis computer programs. Measured running losses of the air bearing are much lower than those of the oil jet lubricated ball bearing it is replacing.

The feasibility of using hot pressed silicon nitride (HPSN) for rolling elements and for races in ball bearings and roller bearings has been explored. HFSN offers opportunities to alleviate many current bearing problems including DN and fatigue life limitations, lubricant and cooling system deficiencies and extreme environment demands. The history of ceramic bearings and the results of various element tests, bearing tests in rigs and bearing tests in a turbine engine will be reviewed. The advantages and problems associated with the use of HPSN in rolling element bearings will be discussed.