TENDENCY to detonate is probably the most important factor in determining the usefulness of fuels for internal-combustion engines. Although it is possible, by various means, to measure more or less accurately the relative knocking-characteristics of fuels, no way has heretofore been found of rating fuels that does not depend upon some arbitrary non-reproducible conditions and measurements. The general methods adopted have consisted in comparing one fuel with another, but no absolute standard has been available. Knocking is a function of several variables, the knocking characteristics of which have been found by keeping a certain number of them constant while certain others are varied, thus rating them in terms of load, the spark-advance necessary to produce knocking, the position of the throttle at which knocking begins, and the like.
ALL petroleum-oil cracking operations that have been developed to meet the quantity demand for engine fuel are liquid-phase processes, but the increasing demand for quality is now affording refiners an opportunity to develop distinctive products. In the opinion of the author, cracking processes of the future will be of the vapor-phase type, which gives a product possessing antiknock properties that are markedly superior to those of present fuels. The composition and distinguishing characteristics of the various families of petroleum oils are explained, including such groups as the paraffins, olefins, naphthenes, and aromatics, the last named including the naphthalenes.
THIS article reports a series of tests on the carbon-depositing tendencies of motor oils, supplementary to those reported at the 1926 Annual Meeting.4 The first investigation was concerned with conditions prevailing in passenger-car engines, the results leading to the formation by the authors of a theory explaining the relationship between certain characteristics of oils and their carbon-depositing tendencies. In the second series of tests the authors controlled the various factors to values commonly found in heavy-duty engines and in their findings confirmed the theory previously set forth. A tentative explanation offered for certain facts revealed by the tests as to the carbon-depositing tendencies of motor-oils rests on the volatility, in the combustion space of the engine, of the oils used. An approximately straight-line relationship also was established between the amount of carbon deposited per liter of oil consumed and the Conradson carbon-residue test.
A STUDY of the performance characteristics of journal bearings when an abrasive is in the lubricant was undertaken to obtain an indication as to what effect an increase in the viscosity of the lubricant might have on the performance of the bearings of automobile engines when diluted or low-viscosity crankcase-oil is contaminated with road dust or other solid matter. The general scheme of conducting the tests involves acceptance of the common theory of lubrication of complete journal-bearings and actual operation of bearings under conditions simulating practical applications, with oils of different viscosities and with and without the addition of an abrasive. During one series of runs, an attempt was made to measure the wear that occurred. The wear on the shaft was practically negligible, but the wear on the bearings was found to have been sufficient to change the average clearance-diameter value from 1/663 at the commencement of the test to 1/597 after the test was completed.
DETAILS are given of the method of control of the engine so that quantitative and reproducible measurements of detonation and comparisons with spectra can be made. Typical data are tabulated and photographs are shown of the free-burning flames of hydrogen, carbon monoxide, methane, gasoline in a blow-torch, and the like. The spectra of explosion and of detonation in the engine confirm earlier conclusions. By means of a synchronous shutter, the spectra of radiation during the four quarters of a stroke are obtained for straight-run gasoline under detonating and non-detonating conditions for the same fuel containing tetraethyl lead, aniline and iodine as knock suppressers and for cracked-gasoline blends. The outstanding result is that, during detonation, the first-quarter spectrum extends far into the ultra-violet, that of the second quarter, a somewhat less distance; the third and fourth quarters are characterized by very little radiation energy.
AS the title indicates, this paper comprises a description of the construction of an apparatus and the development of a method of operating it in determining the rating of motor fuels in the order of their detonation. A Delco-light unit, consisting of a single-cylinder internal-combustion engine directly connected to a direct-current generator, was the basic outfit used but it was changed in many ways in its course of development as a testing-machine. The changes made are explained in detail. The method of testing adopted for rating a motor fuel was to match it, by trial and error, with a blend of chemically pure benzene and selected straight-run Pennsylvania gasoline. Several series of experiments were made to determine what blend or blends of benzene and the standard gasoline match a given fuel under widely different conditions of compression-ratio and spark-setting.
THIS paper was prepared as part of the Cooperative Fuel Research program and presents mainly a review of published data on methods of measuring the anti-detonating qualities of motor fuels. Although detonation as a factor in gaseous explosive reactions is not a new subject, the general recognition of anti-knock value as an important quality of automotive engine-fuels is comparatively recent. Reference is made to bibliographies covering earlier work in this field, and an outline is given of work now in progress at various laboratories and universities. Ricardo's two test-engines and his methods of rating fuels in terms of highest useful compression-ratio and toluene value are described, and the applicability of his results to other engines is discussed. The British Air Ministry Laboratory, using a Ricardo variable-compression engine, compares fuels on the basis of percentage of increase in highest useful compression-ratio.
AN examination for detonating qualities of 18 petroleum gasolines was made by the authors, the methods used being those of direct engine-tests and of chemical analysis. A single-cylinder lighting-plant engine, suitably modified, and a direct-reading detonation-indicator were utilized and they are described. The method of Morrell and Egloff was followed in the chemical analysis. This consists in determining the proportions of paraffins, naphthenes, unsaturated and aromatic hydrocarbons and calculating the aromatic equivalence of the hydrocarbons so found by the use of data compiled by Ricardo on the relative knock-reducing tendency of unsaturated hydrocarbons, naphthenes and aromatic hydrocarbons. These data indicate an equivalence expressed by the ratio 5 to 4 to 1. Experiments were made in which a constant proportion of one hydrocarbon of each class was added to a gasoline, and the detonating tendency of the resulting mixture was determined by engine test.