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MOLECULAR weight or volatility has been found to be the most important factor in determining the extent to which a lubricant contributes to combustion-chamber deposits and octane requirement. Bright stock appears to be particularly harmful. Crude source (or variation in predominating hydrocarbon type) seems to have little effect. These authors report further that commercially practical mineral-base oils have been developed that show a significant advantage over previously known conventional lubricants in their ability to prevent these deposits and octane requirement increase when used with a conventional leaded fuel. Moreover, they say that SAE 5W-20 motor oils can be made that give a 4-5-octane advantage over conventional motor oils in preventing detonation. They point out, further, that, although progress has been made, even better lubricants and fuels are needed, in this respect.

COMBUSTION-chamber deposits are the primary cause of preignition. This preignition may be silent or it may be manifested by a variety of engine noises ranging from light pings to violent explosions. Its occurrence, according to these authors, is favored by changes in engine operating conditions that result in the development of higher pressures and temperatures during compression, or that cause an increase in the concentration of oxygen available to support the combustion of carbonaceous material. Thus, increased compression ratio, supercharging, operation with retarded spark timing, and the combustion of lean mixtures are likely to increase the tendency for the occurrence of preignition. Some hydrocarbons have a greater tendency to be ignited by hot deposit particles than others. Preflame reactions of the fuel tend to sensitize it to ignition. Under certain conditions, the effect of these preflame reactions can be minimized by tetraethyl lead.

STUDIES of cars on the road show that both fuel and lubricant characteristics affect the occurrence of autoignition. For instance it is indicated that autoignition can be eliminated by increasing the fuel antiknock quality, although the Research octane number required may vary slightly depending on fuel composition. Limited evidence is also presented to indicate that aromatic constituents of gasoline are somewhat less effective in suppressing autoignition than are paraffin hydrocarbons. In addition, it is shown that differences in autoignition tendency are observed when different fuels and lubricants are used during the deposit buildup period. In one series of tests a difference of seven octane numbers was observed between autoignition tendencies resulting from operation with different lubricants.

DEPOSIT-induced ignition (the erratic ignition of the fuel-air mixture by combustion chamber deposits) is one of the problems hindering the development of higher compression, more efficient engines. Deposit-induced ignition results in uncontrolled combustion, which often is followed by knock. In some modern engines, the suppression of knock originating through this mechanism may require higher fuel antiknock quality than that required to suppress ordinary knock. Fuel composition and volatility have been found to affect the amount of deposit ignition. Reduction in fuel end point reduces deposit ignition. Among individual leaded hydrocarbons, aromatics produce by far the most deposit ignition, but the differences among full-boiling gasoline stocks of similar volatility do not appear to be related to their hydrocarbon-type proportions. Engine operating conditions favorable to carbon formation tend to increase deposit ignition and magnify differences among fuels.

THE study of engine life, carried out by investigating engine wear in typical service, and by then striving to find the most effective ways of controlling it, forms the basis of this paper on contaminants in lubricants. The investigation involved a study of engine wear in 20,000 miles of operation typical of the average driver. The average driver was selected by using test cars from an employee transportation car pool. At the conclusion of the tests it was found that the use of the full-flow oil filter proved to be the best method for restricting engine wear caused by contaminants that get inside the engine. It was also shown that after successfully eliminating large, solid particles, further restriction of engine wear would depend upon the ability of the oil to lubricate, and upon the engine design to provide the oil supply in a manner suitable for lubrication of each part of the engine.

THE author states that his purpose in presenting this paper before the Student Branch is to suggest a few unsolved problems concerning the diesel engine. His effort to stimulate student thinking into channels which may lead to acceptable solutions has been summarized in four pertinent points: 1. Stressing the importance of mixture formation to the end that each fuel particle, when properly prepared for the chemistry of combustion, may find its necessary equivalent of oxygen as quickly and conveniently as possible. 2. More definite controls for heat extraction of regions subject to thermal fatigue in combustion-chamber envelope. 3. Better knowledge of distortion control to give added life to critical parts required to channel heat or seal pressures. 4. Need to develop a real supercharger preeminently matched to diesel field operating conditions.

THIS paper discusses a number of factors involved in the problem of octane-number requirement increase due to combustion-chamber deposits. A laboratory single-cylinder engine test procedure, which evaluates the effects of various fuel and oil factors, is presented with data showing its correlation with passenger-car operation under light-duty, city-driving conditions. The influence of engine operating conditions during accumulation of deposits and the importance of engine conditions selected to evaluate the magnitude of the requirement increase are illustrated. It is indicated that organic materials formed from both fuel and oil are of major importance in deposit formation. Data are presented which show that tel added to pure hydrocarbons of different chemical types may have different effects. It is shown that the carbon/hydrogen ratio of leaded pure hydrocarbons influences the amount and composition of the deposit formed.

THE main steps to be taken in the design and development of an automobile body are outlined here. First, the art department, given the principal dimensions, produces several design studies for further consideration. Next after the necessary modifications are made, scale models are formed of wood and clay. Later, a full-size clay model is built up, from which full-size layouts can be drawn. Next, a full-size mockup is made, from which full-size drafts are made on aluminum sheets painted white. The lines on these drafts are used to make templates, from which mahogany die models are made of each part of the body. These models are then used in cutting the dies.

NODULAR cast iron, so called because the graphite is present as finely dispersed, well-rounded particles, is made in two stages: The first stage consists of the addition of magnesium or other carbide formers, which promote the formation of white iron in one normally solidifying gray. In the second stage a ferrosilicon type of inoculant overcomes the tendency toward white iron and causes the graphite to precipitate out in the form of small spherulites. The methods of making nodular iron, the effect of composition on physical properties, economic factors involved, and potential applications are discussed in this paper.

IN this paper, which was presented by Mr. Boyd when he received the Horning Memorial Award, the author outlines the story of the long search for a suitable antiknock compound that began in 1916 and attained success with the discovery of the effectiveness of tetraethyl lead. Mr. Boyd then goes on to relate how the study of fuels was continued, with the investigation of such phases as the structure of hydrocarbons, evaluation of the benefits of high compression, and combustion studies. Finally, he urges that research on fuels and engines be continued without abatement, for, he says, the development of more efficient fuels and engines would result in huge economic gains and in the conservation of our petroleum resources just as it has done in the past.

WARTIME emergency showed the inadequacy of existing off-the-road transport, and hurriedly organized research did not solve any of the basic problems. Postwar research has explained many fundamental ideas, such as that of ground pressure, and has stressed the importance of the concept of two-dimensional soil loading imposed by a vehicle. The principles of a quantitative relationship between the performance of a track and a wheel were formulated, and the soil properties responsible for vehicle performance have been defined. The effect of grouser action and tire tread was clarified, and new laboratory methods of working by means of scale models were developed. The limitations of present design trends were examined, and the necessity for new concepts has been emphasized. Only very slow progress toward this goal is anticipated unless active support for the necessary research program is given by interested agencies.

THE relation between fuel/air ratio and the products of incomplete combustion is discussed here, as well as the probable origin of these products. The authors observed a relation between concentration of aldehydes and the odorous and irritating character of diesel exhaust gas. This relation suggested to them that removal of aldehydes should reduce odor and irritation of the exhaust gases. Tests with water as a scrubbing medium showed that aldehydes cannot be removed completely by such a system. However, aqueous sodium sulfite solutions inhibited by the addition of hydroquinone to prevent oxidation of the sulfite remove substantially all of the aldehydes and effect significant reductions in odor and irritation for extended periods of time. The paper discusses also the application of data on exhaust-gas composition to the determination of operating and performance data on diesel engines.

THE only fuel property showing significant correlation with wear and deposits in these tests was sulfur content. Work on two engines: one operating at a moderate bmep and speed, the other at high bmep and high speed, showed that the more heavily loaded engine consumed three times more fuel per hour, per cylinder than the moderately rated engine and the increase in wear for a ½% increase in sulfur was also three times that encountered in the moderately rated engine. This indicates that high rates of wear and more deposits encountered at high bmep and speeds are not so much a function of the higher mechanical and thermal loading of the parts, but are primarily due to the fact that more fuel is required to carry the higher loads. It is the opinion of the authors that sulfur combines with the hydrocarbon molecules of the fuel in the combustion process and forms a black abrasive deposit that causes wear.