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Technical Paper

Fundamentals of Automotive Lubrication

SATISFACTORY performance of a lubricant depends upon characteristics of the lubricant, operating conditions and design of the device in which the lubricant is used. Applied lubrication requires a study of the relation among these factors in their effect upon performance. The authors treat journal bearings, ball and roller bearings and gears. Equations are given for journal bearings operating under various conditions of design, lubrication, friction and heat dissipation. The authors conclude that neither ZN/P nor PV alone is adequate as a measure of the power dissipated by a bearing, a composite relation involving both terms being required over a large part of the operating range. They show that each bearing has a minimum value of ZN/P below which it may get into the unstable region of thin-film lubrication and fail.
Technical Paper


The development of intake-manifolds in the past has been confined mainly to modifications of constructional details. Believing that the increased use of automotive equipment will lead to a demand for fuel that will result in the higher cost and lower quality of the fuel, and being convinced that the sole requirement of satisfactory operation with kerosene and mixtures of the heavier oils with alcohol and benzol is the proper preparation of the fuel in the manifold, the authors have investigated the various methods of heat application in the endeavor to produce the minimum temperature necessary for a dry mixture. Finding that this minimum temperature varied with the method of application of the heat, an analysis was made of the available methods on a functional rather than a structural basis.
Technical Paper


In the first part of the paper, a general quantitative comparison of air, water and oil-cooled cylinders is given as it relates to the subject of heat-transfer and temperature drop. Unfortunately, the discussion does not include experimental data, but the assumptions are stated clearly and a large range of values is covered in Table 2 so that any desired values can be chosen. A thorough and comprehensive discussion of the steam or the radio-condenser type of cooling is given under the headings of Steam Cooling Systems, Characteristics of Steam Cooling Systems, Cooling Capacity of Radiators Used To Condense Steam and Present State of Development. In the second part, an attempt is made to give a thorough but brief discussion of the performance or of the operating characteristics of radiators from the point of view of the car, truck or tractor designer. The cooling of aircraft engines is not considered.
Technical Paper


Annual Meeting Paper - The heat-dissipating properties of three types of radiator core have been investigated at the Mason Laboratory, Yale University. These include the fin-and-tube, the ribbon and the air-tube groups, so classified according to the flow of the water and the air. The ratio of the cooling surface to the volume is shown to be nearly the same in the fin-and-tube and the air-tube cores, while that of the ribbon core is somewhat greater. A formula is derived for computing the heat-transfer coefficient, which is defined as the number of heat units per hour that will pass from one square foot of surface per degree of temperature-difference between the air and the water and is the key to radiator performance, as by it almost any desired information can be obtained. When the heat-transfer coefficients have been found for a sufficiently wide range of water and air-flows the cooling capacity of a radiator can be computed for any desired condition.
Technical Paper


Wide differences of opinion are expressed by automobile builders regarding crankcase-oil dilution. The theories advanced in explanation of dilution fail to elucidate some important facts and must therefore be regarded as unsatisfactory. From a theoretical investigation, the author determines the conditions under which the vapors of various fuels condense during the compression stroke of the engine and, as a result of such analysis, presents the theory that “surface condensation,” or the aggregation of the liquid fuel-particles on the cylinder-walls, is chiefly responsible for crankcase-oil dilution. First, suggested explanations of the dilution are presented, references to previous experiments by several authorities are stated and these are discussed. The effect of jacket-water temperature is analyzed, and whether any condensation of fuel takes place during the compression stroke of a carbureter engine is debated.
Technical Paper

Combustion Control by Cylinder-Head Design

DETONATION and shock, the two principal barriers to increased compression, are subject to a degree of control which can readily make possible the use of compression ratios in the neighborhood of 6-1 on commercial fuel without objectionable effects and without sacrifice of output. Since detonation depends primarily upon the temperature attained by the residual unburned gas, it can be controlled by combustion-chamber design which intensifies the heat transfer from the unburned gas to the walls. The shock tendency, which originates in the pressure-time characteristic of combustion, can be controlled only by deliberate incorporation of the desirable anti-shock characteristic in the chamber design by a method of calculation which is explained in detail.
Technical Paper

Interpretation of the Indicator Card

TRUE thermodynamic interpretation of the indicator card must be based upon the properties of the actual medium working in the engine and must take into account the actual nature of the heat liberation. The temperature-energy diagram for the working combustible mixture and for the resultant combustion products provides for this interpretation a foundation that is universally applicable to engines using a given type of fuel. This diagram automatically includes the effect of variation in specific heat with temperature, because the entire energy content of a gas at any temperature is the energy required to raise it, at constant volume, from absolute zero to that temperature. The work done during the actual changes of state, as determined from the indicator card, can readily be represented on the same diagram, and the heat interchanges involved can be determined quantitatively by comparison with the adiabatic criterion.
Technical Paper

Development and Application of HEATED WINGS

THIS report, a discussion of the design problems in heated surface anti-icing equipment, consolidates and compiles all of the heat transfer data known to be available from past experimentation and considered to be required for current and future designs. Consequently, the author believes that the discussion contained herein will be of assistance in some degree to designers and engineers confronted with problems relating to heated surface anti-icing. The report deals with a rapid means of calculating heated wing requirements, charts of heat transfer coefficients, a discussion of instrumentation techniques, and a method of calculating surface temperatures in dry air.
Technical Paper

THE RAMJET as a Supersonic Propulsion Plant

THE ramjet excels all other powerplants for sustained propulsion at supersonic speeds. Ramjets feature high power per unit frontal area and per unit weight and high specific impulse. In compensation for mechanical simplicity, the ramjet presents a number of aerodynamic and thermodynamic problems. Because supplying air-streams for studying these problems with full-scale models would require enormous amounts of power, their solution must be found through improved understanding of the fundamentals of the process.
Technical Paper


IN this discussion of vapor cycles and powerplants for motor vehicles, the author recognizes that a new approach is essential to their serious consideration. He shows how accepted cycles can be modified for automotive purposes with advantage. He suggests that automotive principles of design and construction be used in preference to earlier designs utilized for engines of the vapor type. Rather than attempting to revive steam vehicles, Mr. Neil aims to show that unless new knowledge is applied to the design of vapor powerplants and adequate consideration given to the thermodynamic and other factors involved, their advantages cannot be fully realized. The paper summarizes a part of the research work incidental to the design of powerplants of the vapor type carried out before the war and since that time. The author, therefore, does not intend to present any complete and final conclusions, but rather to indicate the lines along which the work has so far progressed.
Technical Paper


IN this paper the authors present results of their study of precombustion reactions - which are chemical changes occurring in the fuel-air mixture ahead of the flame front - based on thermodynamic analysis of engine data. A single-cylinder, knock-test engine, operated at a fixed compression ratio, was used in conjunction with balanced pressure equipment for obtaining experimental data. The thermodynamic analysis showed that simplification in computation of the heat of precombustion reactions would be possible if ignition timing were retarded, so that the normal flame would be initiated after completion of the precombustion reaction. Therefore, tests were run both at normal ignition timing and with retarded spark. Another series of tests were made to determine the effects of precombustion reactions on the power developed by the engine.
Technical Paper

Effectiveness of the BURNING PROCESS in NON-KNOCKING Engine Explosions - (The Use of Thermodynamic Charts in the Analysis of Flame-Picture and Pressure Data)

COMBUSTION was found to be approximately 81% effective in five different explosions which were recorded by means of high-speed motion pictures and pressure cards while running the engine on iso-octane and benzene, the authors report. The term “81% effective,” they explain, means that, according to modern thermodynamic data, only 81% of the liberated heat energy is accounted for by the pressures observed during combustion; in other words, 19% of the liberated heat energy is apparently lost from the working fluid. The flame-picture and pressure data together with the Hottel thermodynamic charts make possible a comparison of the actual rate of inflammation of the charge with the rate of combustion required by the thermodynamic analysis for developing the observed pressures. These two rates of combustion are approximately equal during the inflammation of the first 10% of the weight of the charge and during the inflammation of the last 50%.
Technical Paper

OIL COOLING - Its Relation to Bearing Life

IN his discussion of oil cooling and its relation to bearing life the author attempts to answer four questions: (1) Why temperature affects bearing life; (2) What the actual bearing temperatures are in service; (3) What factors cause high oil and bearing temperatures to be generated; and (4) How to reduce these temperatures most conveniently and effectively. The best method of cooling the oil, he finds, is by the use of radiators in the air blast. Heat exchangers utilizing the engine cooling water, he believes, are not practical for engines where oil temperature control to 180 F maximum is desired. Also, jacketing the oil pan or employing cooling-water coils in the oil pan are not considered feasible methods.
Technical Paper


THIS paper discusses the free-piston engine which is being investigated by Ford. The analytic method for calculating free-piston-gasifier thermodynamic performance over the complete operating range is discussed for the given limitations and conditions. Using these analytical methods, an automotive-size free-piston and matched turbine was designed, built, and tested.
Technical Paper

Design and Development Considerations of a BIMETALLIC BRAKE DRUM

ANALYSIS of dynamometer and field tests leads the author to suggest the following criterion for determining when to use bimetallic brake drums: When cooling air is available, the bimetallic drum will outperform the standard all-cast-iron drum. When cooling air is not available, then its use, except to eliminate squeal, gives only a dubious advantage. Cooling air is of little help to the standard cast-iron drum, he explains, because this type acts merely as a heat reservoir. The bimetallic drum, on the other hand, functions as a heat exchanger, for the heat is rapidly conducted from the friction surfaces to the aluminum fins, where it is dissipated by the cooling air. Thus, the brakes can be used steadily without their getting so hot as to become ineffective.
Technical Paper


It is the purpose of this paper to discuss some of the gains in knock-limited engine performance to be made through utilization of fuels of improved antiknock quality, and also to consider a method of approach to the problem of the quantitative evaluation of these gains in terms of the antiknock quality of the fuel. Thermodynamic approaches to the problem of knock-limited power and economy in a gasoline engine have often been made in terms of compression ratio or supercharge. The translation of these relationships, however, into terms of fuel antiknock quality as measured by currently used standards presents some difficulties at present. It is well-known that fuel antiknock quality is one property of a fuel that determines its potential usefulness, but the question is: how much more antiknock quality makes it how much more valuable?
Technical Paper


ADEQUATE fuel feeding at altitude, these authors point out, is a matter of vapor elimination, either by preventing its formation or by removing it from the system in the event that its formation cannot be prevented. The effect of vapor is invariably to cause failure of the fuel flow if it forms in sufficient quantity in any part of the fuel system that lies between the fuel tank and the carburetor. This paper gives the results of a study of the conditions that bring about this type of fuel failure, and describes means of exploring the phenomena experimentally so that it can be ascertained in advance of manufacture if remedial steps are necessary. The greatly accelerated rate at which designs of military aircraft with increased performance have been developed, they explain, has added materially to the difficulty of feeding vapor-free fuel to the carburetors at the higher altitudes.