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With control of oxides of nitrogen from automobile exhaust scheduled for 1971 in California, and expected to be applied nationwide in the future, the recirculation of exhaust gas appears promising as a method of lowering NOx emissions. This paper discusses work done to evaluate effects of exhaust gas recirculation on intake system cleanliness and crankcase lubricant performance. Intake system effects were evaluated with respect to the formation of deposits in the carburetor, intake manifold and ports, and intake valve tulips. Crankcase lubricant performance was evaluated with respect to both low-temperature deposition and high-temperature oxidation and copper lead bearing corrosion characteristics.

A general analog computer procedure is presented for the dynamic analysis of a selected realistic model of an automobile or truck vehicle wheel-frame system. The elements of the model are assigned a set of values based on a preselected vehicle, and the model is then subjected to a number of inputs which correspond to test track road disturbances at various speeds. This procedure is successively applied to a number of typical vehicles. Time-varying values of wheel spindle and frame reaction “g” loads, acclerations, and displacements are recorded, and illustrative waveshapes are depicted. Tables indicating extreme values of these quantities are also included.

In the continuing search for reduced exhaust emissions from automotive engines, tighter controls on production carburetor fuel-air ratio delivery became necessary. Idle fuel and airflow measurement assumed major importance due to the influence of idle set points on exhaust emissions and on the part throttle flow curve of the carburetor. This paper details the development of idle fuel and airflow measurement transfer systems to correlate data between test stations, including the use of carburetors locked in the idle position. Matched sets of sonic flow nozzles are currently in use at each test location as a basis for defining carburetor idle airflow. Fuel flow, using a test fluid developed specifically for this application, is defined by a simple, accurate weight time calibrator. The current system requires only the transmittal of data between test locations and is now entering its second year of production application.

Misfire and cycle-to-cycle combustion variation are both serious problems in securing good engine performance and low exhaust emissions in the case of using extremely lean mixtures. Making some modifications in the ignition system and in the combustion chamber, and increasing the mixture turbulence, we examined their effects upon the lean limit, the engine performance, and the exhaust emissions. It was found that gap width and gap projection of a spark plug and spark energy as well as mixture turbulence had a great effect on extending the lean limit and improving engine performance with lean mixtures. A compact combustion chamber is preferable for lean mixture operation. Smooth operation of the engine can be maintained even at retarded spark timing by applying the above-mentioned items and providing hot intake air to the engine. Consequently, exhaust emissions, including hydrocarbons and oxides of nitrogen, can be substantially reduced.

A novel earthmoving machine making use of fuel-air explosions for the displacement of soil is presently under development. This paper discusses the mechanics of operation of the device, and reviews operating experiences and test results.

The effect of travel rate on force response of soil cutting blades is considered and found to include inertial, shear strength, and failure mode phenomena. The inertial effect is related to the acceleration of the cut soil mass and a simple equation is extracted from the literature and shown to correlate with the test results of flat inclined blades. The blade cutting force of saturated clay is found to exhibit a pronounced shear strength-rate effect which can be predicted from cone penetrometer measurements. Travel rate is found to change the mode of failure of certain soil-blade systems.

As part of a general program of work on opposed piston compression ignition engines operating at high output, it was considered that the scavenging of the engine merited separate attention. Scavenging is of vital importance in the achievement of high output and no information on the operation of opposed piston engines at high boost was available. Further, some idea of the scavenging efficiency was needed for theoretical work proceeding in parallel with the experimental investigation. For the two reasons given above, it was decided that the scavenging of the opposed piston engine operating at elevated pressure should be examined experimentally and an attempt made to relate the measurements to the various theoretical models available. An introduction to scavenging theory will be given, followed by a discussion of experimental methods. A description of the apparatus and a comparison between experimental results and the various theoretical models will complete the paper.

A computer program package is described for use in simulating the unsteady gas dynamic processes occurring in a reciprocating engine system. The program package is written in Fortran IV and utilizes the Method of Characteristics to solve the general equations of one-dimensional unsteady flow in the presence of heat transfer, wall friction, and entropy gradients. It is arranged in a generalized form to allow ready application to a variety of engine and duct configurations. A subroutine library of standard engine/duct boundary conditions has been developed which, together with the unsteady flow program, can model a desired system configuration with no further programming required from the designer. The paper describes the development of the program package and of some of the duct boundary subroutines. A single cylinder two stroke engine model with intake and exhaust ducts is used to demonstrate the application of the package.

Two comprehensive programs for the complete cycle synthesis for compression ignition engines are briefly described. The programs include the intake pipes, the exhaust pipes, and the turbocharger if this is fitted. The combustion in the power cycle is represented by a simple heat release model as described by Whitehouse, et al, and the heat transfer is computed by the method of Annand. The wave action in the intake and exhaust system and the gas exchange process in the cylinder are computed by methods described by the author in earlier papers. Recent improvements include heat transfer in the pipe system, supersonic flow, and the exact dimensioning of the pipe system. The matching of the turbocharger within the engine is described, based on quasi steady methods, and a discussion of the possible limitations of this approach is given. Comparison of experimental results taken on engine tests with the computed predictions, are given.

The vehicle industry in general and the trucking industry in particular have found that mechanical power conversion of gas turbine engines for prime mover needs requires the use of an automatic transmission. Multiple gear ratios are required to keep the engine running within its most efficient operating range. Power shifting is required to prevent engine runaway during shifts and eliminate the attendant difficulty in matching of engine and transmission speeds for smooth shifting. The HT-740T automatic transmission was designed to provide optimum usage of gas turbine engines in trucks and buses. In this paper a description of the transmission gearing arrangement and controls is presented to show how the transmission functions and utilizes signals from the gas turbine engine. Other transmission features peculiar to gas turbine applications are also presented. In addition, the extensive development program to which this product has been subjected is described.

An engineering evaluation conducted by the International Lead Zinc Research Organization, Inc. (ILZRO) has produced data which verify that die cast zinc is stronger, stiffer, and more thermally resistant than five major engineering thermoplastics-polycarbonate, polyacetal, nylon, ABS (acrylonitrile-butadiene-styrene), and polypropylene-under identical test procedures. However, since zinc is five to eight times more dense than the polymers tested (and most other unfilled polymers), the plastics industry often stresses the high strength-to-weight ratios and low cost per cubic inch of plastics as more than offsetting advantages. The question facing the design engineer, therefore, is: which material is the best choice for the particular application; that is, which will provide the required strength and stiffness at lowest cost?

A study was made of the influence of adjacent loaded areas on the performance of rolling aircraft tires on soil runways. These tire/soil interaction effects which occur in multiple tire landing gears were evaluated based on sinkage and drag. The total study consisted of four parts. Three of the parts have been completed. The fourth part, which is an experimental effort, is still in progress. The first part consisted of an evaluation of existing full scale field test data from aircraft or test carts operating with multiple tire configurations. The second part was a Dual Plate Vertical Load Test Program which yielded sinkage interaction effects from single and dual plate load tests in sand and clay. An analytical study was made in the third part using a lumped parameter iteration technique together with an elastic-plastic soil model for studying adjacent load interaction effects.

Several basic heat transfer equations have been utilized to enable the calculation of the thermal performances of vehicle radiator cores. The application of the calculation procedure to the two types of radiator matrix in general use has been shown in some detail, and results using these methods have been compared with experimental values. These correlations have shown that the calculation procedure can be used with confidence to predict matrix dissipations for Reynolds numbers in the water tubes of less than 1000, as found in automobile heater cores, as well as for the larger Reynolds numbers in the water tubes typical of automobile radiator cores.

A series of analyses and experiments has been carried out on the problem of poor air/fuel ratio characteristics at the transition region from the idle system to the main system. The fuel supply characteristic of the idle system, as well as that of the main system, has been treated as a function of intake air-flow rate. It has been shown theoretically that the behavior of the fuel in the transition region results from the fuel passage construction of the conventional type of carburetor, and that a uniform air/fuel ratio can never be supplied in the transition region without a main air-bleed system. The effects of the main air-bleed system on fuel supply characteristics at the transition region have been investigated quantitatively. The mechanism of fuel supply at the transition region has been confirmed through experiments made on actual parts.

There are many sound reasons, both economic and mechanical, for using an automatic transmission if it has high efficiency. The G.K.N.-S.R.M. transmission links an epicyclic gear train with an unconventional converter blade system to change conditions of fluid flow and give a very high stall torque ratio. Hydraulic efficiencies in the converter stages are discussed and torque distribution in the system is analysed. Use is made of existing elements to give hydraulic braking at negligible additional cost. Simple modifications to the blade system allow accurate matching of the transmission to the engine while auxiliary gearing may be provided to give a wider ratio spread if required. The transmission control system is described. Another version of the converter with variable pitch impeller blades has been designed for use with turbine engines up to 400 hp which may, with advantage, be of single-shaft type.

This paper discusses the components and systems incorporated in the design of the LM2500 marine gas turbine. The discussion describes the novel and high performance features of this second generation marine gas turbine which include a high pressure ratio compressor, high temperature gas generator turbine, gas generator turbine cooling system, and high performance power turbine. The paper describes the materials used and the features incorporated which enable the LM2500 to operate successfully in a marine environment. The LM2500 marine gas turbine derived from the General Electric TF39/CF6 turbofan engine family incorporates many engineering advances which are not available in the first generation marine gas turbines. These advanced features enable the LM2500 marine gas turbine to achieve performance levels unmatched by any first generation marine gas turbines now in service.

After several years of negative experience using conventional commercial water dynamometers directly driven at free power turbine speed, the author's company undertook an in-house design of a noncavitating dynamometer with the objectives of long life and low maintenance cost. The paper is a review of the design and performance of the dynamometer, utilizing smooth disk and stator elements and employing viscous shear variable immersion torque control.

This paper discusses the advantages of closed type and open type working sections of a wind tunnel designed for aerodynamic tests on full-scale vehicles. Analyses of economic considerations, component efficiency, and applicability to the specific purpose of testing were the deciding factors in choosing the open type working section for this wind tunnel being erected by Pininfarina at Torino, Italy. Preliminary design work and supporting research are described.

The term triple safe is used to identify an air brake system with three separate circuits, two of which are service brake systems of virtually equal effectiveness; the third is a spring parking brake system. The paper reviews the spring parking brake chamber capability and describes a triple-safe air brake system and chambers that have similar service and emergency capacities, and parking capabilities, to meet future requirements of trucks and buses.