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Technical Paper

Ventilation of Motorcoach and Motor-Truck Bodies

This report of the S.A.E Subcommittee on Motorcoach and Motor-Truck Ventilation states that, to the motor-vehicle operator, ventilation means the elimination of gas odors from the coach body or truck cab; but to the public it means, no doubt, simply proper interior ventilation. Adequate interior ventilation becomes a necessity because of the stigma against buses which has arisen due to their characteristic odor. The investigation of the Subcommittee over millions of miles of operation indicates that there is no one cause of fumes, and certainly no single cure. In the report, discussion is included relating to the causes of gas fumes, such as fumes due to leaks and to engine condition; exhaust-pipe location; carbureter adjustment; the importance of proper driving; engine maintenance and body ventilation. Ten causes of “gassing” are listed.
Technical Paper


The efficiency of internal-combustion engines increases with the pressure of the charge at the time of ignition. Therefore, a compression at full load just below that of premature ignition is ordinarily maintained. But when such an engine is controlled by throttling, the efficiency drops as the compression is reduced, and as automobile engines use less than one-quarter of their available power the greater part of the time, the fuel consumption is necessarily high for the horsepower output. On account, also, of the rarefaction due to throttling, more power must be developed than is necessary to drive the car; automobile engines in which the fuel is introduced during the induction stroke, would be more efficient, therefore, if the maximum compression were constant during all ranges of load.
Technical Paper


The term “natural gasoline” has been accepted generally by the petroleum industry as applying to the gasoline product extracted by any process from natural gas. Two processes are in use. The older one is the compression process applied to casinghead gas, which is produced from the oil-bearing sands of oil wells and carries vapors from the oil with which it has been in contact. This process of subjecting the relatively rich gas to a high pressure and then cooling it to or below atmospheric pressure, results in the direct condensation of gasoline which is weathered later to remove the “wild” unusable vapors. The later method is the absorption process in which the gas is brought into contact with a heavy oil, originally of no gasoline-content, which absorbs the gasoline. The enriched oil is then heated to distill off the gasoline, and these two operations of absorption and distillation are repeated continuously within a closed system.
Technical Paper


This report deals with further progress in the cooperative fuel-research. General factors underlying starting ability are discussed and experiments showing the effect of changes in spark character and of gas leakage are described. The probable mechanism of crankcase-oil dilution is treated, and further experiments with reference to this subject are explained. One experiment deals with operation with oil as a cooling medium to obtain high jacket-temperatures. Other experiments show the effect of change in piston clearance and in the number of piston-rings employed. Factors influencing the rate at which the diluent is eliminated from the diluted oil are shown to be of importance, and methods of examining these factors are stated.
Technical Paper

Fuel-Mixture Distribution

AFTER outlining the effects of improper distribution of fuel mixture in an internal-combustion engine and stating how the distribution of a gas is governed, the author discusses motor-fuel condensation and states that, since preheating the air is objectionable and hot-spots do not supply sufficient heat to vaporize the fuel completely, the induction system must distribute wet mixtures; and the partial or complete solution of this problem ordinarily is the result of experimenting with different designs for any particular engine. Regarding the manifold action with wet fuel-mixtures, it is stated that the phenomena occurring in manifolds which distribute such mixtures are complicated and unstable but some insight into them can be obtained by studying the action in a two-cylinder engine. Analysis shows that the even distribution of wet mixtures is extremely difficult.
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

Vapor-Pressure Data on Motor Gasolines

THE REPORT deals specifically with that part of the Bureau of Standards' program involving vapor-pressure measurements. A description is given of a method and apparatus for the removal of dissolved gases from dried gasolines, without appreciably affecting the propane content and without otherwise changing their composition. Vapor-pressure measurements with a small bubble of vapor present have been made on 10 motor gasolines over a considerable temperature range. Log p, 1/T plots of these data were found to be linear in the case of all the fuels within 1 to 2 mm. on the average, p representing the pressure and T the absolute temperature. The normal bubble-points (p = 760 mm.) of the 10 gasolines were shown to be equal to the 10-per cent A.S.T.M. temperatures, corrected for loss, within the accuracy of determining the latter.
Technical Paper


The author first compares mineral oils with certain other liquids in order to point out clearly certain of their characteristics. He then shows the economic benefits that would result from making more of the crude available for use as fuels. He discusses such topics as cracking methods in use, advantages of dry gas, initial flame propagation, gas producers, hot mixtures, wet mixtures and difficulties of correcting existing engines. He concludes by proposing as a solution of the gasoline problem the more general use of superheated homogeneous fixed dry gases made in vaporizing devices independent of engine cylinders, and outlines means for attaining this end. Performance data covering the use of mixtures of kerosene and gasoline on several cars are included in a table, and several charts throughout the paper illustrate many of the topics discussed.
Technical Paper


The author states that the objects of the paper are to define and trace the development of the various processes of carburetion, and to offer such suggestions along these lines as may assist the investigator in developing motorboats, automobiles and self-contained unit motor cars for railway purposes. The surface carburetor is mentioned chiefly as of historic interest. In considering the jet carbureter the author discusses the proportion of gas desired, the effect of the varying inertia of the air and the liquid gasoline and the breaking up of the combustible needed. Following sections review the devices for using kerosene, such as gasoline jet carbureters to which heat is applied, devices of the fixed gas type, the introduction of combustible directly into the cylinder, forcing combustible directly upon a hot surface in the cylinder and devices which raise the combustible to the boiling point.
Technical Paper


DESCRIBED here are the detailed characteristics of two series of synthetic lubricants, one essentially insoluble and the other soluble in water at room temperature. These lubricants are synthesized from natural or other hydrocarbon gases as raw materials. Results of laboratory and field tests indicate that the lubricants can be successfully used in internal-combustion engines. In fact, the authors report that one of them has already been used extensively in aircraft engines by the Army Air Forces and the Air Transport Command.
Technical Paper


AN instrument for the accurate measurement of cylinder wear is described by the authors. The instrument consists of a diamond indenting tool, an indentation locator, and a microscope. To determine wear, the length of an indentation is observed with the microscope before and after periods of operation. Wear, which is reflected by changes in the depth of the indentation, is calculated from changes in the length of the indentation. Using this instrument in their experiments, the authors found that most cylinder wear is due to corrosion and occurs during warmup, when cylinder temperatures are low. It appears that corrosive gases condense on cool cylinder walls and attack the surface. Then the corroded film and lubricating oil are wiped away by the piston, leaving the walls ready for further corrosion.
Technical Paper


POWER recovery from the exhaust gases of aircraft reciprocating engines is analyzed both for the cases where blowdown from each cylinder is used separately and for the cases where it is collected in an exhaust manifold and discharged in an essentially steady flow stream. Performance and design considerations indicate that the blowdown system offers more advantages for compounding than the steady flow system.
Technical Paper

Coating Steel by the Aldip Process

CLADDING of steel parts or assemblies with aluminum, through the use of a recently developed process which has been in commercial operation for two years, is described in this paper. Successful plant and field experience indicates that it can be applied at room and elevated temperatures in various types of atmospheres. This new process was originally designed to offer corrosion resistance caused by the collection of leaded fuel gas condensates in exhaust systems, and for other parts requiring high-temperature oxidation resistance up to 1600 F. However, it has since been used in a wide variety of applications.
Technical Paper

Some Factors Affecting Precombustion Reactions in Engines

USE of a motored engine as a convenient method for studying precombution reactions is described in this paper. Preliminary investigations of this technique were made in 1950, and this paper covers the work accomplished since then in establishing a better understanding of chemical reactions preceding knock. Extent and type of precombustion reactions which occur in the unburned charge ahead of the flame front determine the tendency of a fuel-air mixture to knock. Use of a motored engine substitutes compression of the unburned charge by the piston for compression of the end gas by the flame front. The buildup of knock-producing materials is considered in studies of mixture compositions and time factors. Observed precombustion reactions are related to problems concerning the adaptation of fuels to engines.
Technical Paper

Compression and End-Gas Temperatures from Iodine Absorption Spectra

THIS paper discusses a method of measuring compression temperature by means of the absorption of light. An optical-electronic system measures the change in color of a trace of iodine gas that has been added to the intake mixture. From these measurements the temperature of the iodine and by inference, the temperature of the gases, is determined. The apparatus used is described briefly and the test results obtained in measuring compression and end-gas temperatures in a spark-ignition engine are also presented.