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Spotlight on Design: Sensors: Miniaturization and Testing

2015-04-15
“Spotlight on Design” features video interviews and case study segments, focusing on the latest technology breakthroughs. Viewers are virtually taken to labs and research centers to learn how design engineers are enhancing product performance/reliability, reducing cost, improving quality, safety or environmental impact, and achieving regulatory compliance. Accurate data is critical for the testing and development of parts and systems for cars, trucks, and airplanes. To obtain this data, engineers rely on high-end specialty sensors that can fit into cramped spaces and operate reliably under extreme heat and pressure. In the episode “Sensors: Miniaturization and Testing” (21:02), AVL engineers explain how a new crystalline material was developed to accurately measure the high pressures in the combustion chamber of turbocharged engines, and Meggitt Sensing Systems profiles the world’s smallest triaxial IEPE accelerometer.
Technical Paper

Standard Rating Needed for Fuels for High-Speed Oil-Engines

1933-01-01
330002
ONCE a method for standard Diesel-fuel knock-rating has been established, a standard for Diesel-fuel specifications should be set which will cover standard knock-rating, gravity, viscosity, pour point, Conradson carbon, water, sediment and sulphur content. The last three items have an important influence on the wear and depreciation of the engine as well as on the carbon formation in the combustion chamber. The foregoing conclusions are reached after the author has treated the subject in general as well as in particular, under the headings: Combustion process, delay period, turbulence, drop-size, variable delay-time, spontaneous and controlled combustion, chemical characteristics of the fuel and physical properties. Practical methods for oil-engine-fuel knock-ratings are also suggested.
Technical Paper

Appraising Diesel Engines by Air Capacity and Speed

1932-01-01
320054
BRAKE mean effective pressure is held by the author to be inadequate as a measure of Diesel-engine capacity, because it fails to distinguish between losses in capacity that are chargeable to low volumetric efficiency and losses resulting from imperfections in combustion. A study of air capacities assists in making this essential distinction and is advocated as a better basis for appraisal. Variation in effective air supply with speed is regarded as especially important, as acceleration and peak power depend on it. Experimental work cited had to do mainly with the determination of the percentage of carbon dioxide in the exhaust gas, and this is used as a basis for calculating the quantity of air passing through the engine. Conclusions are drawn also from some experiments in which the intake air was measured directly by an orifice-type meter.
Technical Paper

Influence Of Fuel Composition On Deposit Formation In High-Speed Diesel Engines

1948-01-01
480229
On the background of the wide speed and load variations to which high-speed Diesel engines are subjected, the author diagnoses the temperature conditions under which two different types of unburned fuel deposits may be formed. Solid carbon particles (“soot”) are predominantly the product of incomplete combustion at full throttle or high temperature operation while liquid polymerized fuel fractions are experienced in increasing amounts at the low combustion chamber temperatures synonymous with light loads and reduced speeds. Although some faulty engine conditions may be the cause of excessive soot formation, the author blames most deposits of this nature on the presence of high-boiling or even residual fractions and the poor burning quality of predominantly aromatic fuels. Large differences in the magnitude of low temperature fuel deposits were found by the author without much relation to the commonly used fuel inspection data.
Technical Paper

Humphreys Constant - Compression Engine

1952-01-01
520231
THE Humphreys engine is a conventional powerplant to which has been added a device for automatically varying the clearance volume of the combustion chamber. This allows the compression ratio to be varied so that: 1. At light loads the compression ratio is at a maximum, providing best thermal efficiency and therefore lowest fuel consumption. 2. At intermediate loads the compression ratio is somewhat lower but still high enough to provide good thermal efficiency and therefore low fuel consumption. 3. At full load the compression ratio is at its lowest point, so that the engine is able to operate without knock with fuels of quite low octane number.
Technical Paper

New Horizons in Engine Development

1952-01-01
520262
DEMONSTRATING the versatility of the hemi-U spherical or spherical segment combustion chamber, a series of carefully controlled tests has been completed in connection with experimental engine developments, as described by the author of this paper. Using regularly available fuels, or stimulated with super fuels, the engines showed power outputs far greater than the previous designs. The author points out that identical test engines, differing only in combustion-chamber design and valve layouts, showed that a hemispherical head design had a thermal efficiency equal to one full compression ratio better than the next best design, the conventional overhead valve type. The new engine, which develops more than 180 actual horsepower in the production version, using only nonpremium grades of fuel, is expected to respond to whatever demands may be made upon it when the anticipated quality fuels of the future become available.
Technical Paper

FUEL ADDITIVES AND ENGINE DURABILITY

1954-01-01
540125
The development of a successful fuel additive requires considerable effort, a large share of which must be expended on the effect of the additive on engine durability. Durability may be affected as soon as the fuel enters the fuel tank and the possibility of such good or bad effects continues until the exhaust gases have cleared the rear bumper. Some of the durability aspects which can be either improved or made more severe are listed, these include fuel system corrosion, carburetor and manifold deposits, combustion chamber and spark plug deposits, engine wear and general cleanliness and bearing, exhaust system and rear bumper corrosion. It is shown that of seven experimental additives tested in a fleet of passenger cars of one make operated under severe duty conditions, four additives decreased exhaust valve life while three increased exhaust valve life by from twenty-five to fifty per cent.
Technical Paper

DETECTION OF ABNORMAL FLAME FRONTS IN ROAD TESTS WITH AN ENGINE USING INDEPENDENT IONIZATION GAPS

1954-01-01
540099
FOREWORD Recently, a number of investigators (1), (2), and (3) have reported detection by means of ionization gaps of flame fronts other than those initiated by the spark discharge. Since some of the findings in these studies appeared to be contrary to road-test experience at the General Motors Research Laboratories, the significance of ionization-gap data was questioned. For example, Reference (1) shows abnormal flame fronts occurring in an engine in the absence of combustion chamber deposits, whereas in road testing, it is usually necessary to accumulate deposits before abnormal flame fronts become noticeable. Reference (2) shows data wherein abnormal combustion was unaffected by fuel octane number, while in road testing, objectionable abnormal combustion is usually eliminated by increasing fuel octane number. In order to investigate these apparent anomalies, engine tests were made using special independent ionization gaps.
Technical Paper

NEW BUICK V-8 ENGINE OFFERS MANY ADVANTAGES

1953-01-01
530248
AIMS and objectives behind the decision to adopt the V-type design for the large Buick engine in 1953 models are set forth in this paper. From 1903 until the present time Buick produced cars powered by engines utilizing the overhead-valve principle. The authors cite four main reasons for departing from this long tradition: 1. Newer styling, based on extremely low lines, demands an engine proportioned to fit within allotted space under the hood. 2. A compact V-engine is inherently light in weight, especially in larger sizes. Weight reduction improves car balance, handling, and performance. 3. Improved combustion chambers and fuels permit higher compression ratios. Resulting higher explosion pressures call for a more rigid engine structure, which can be achieved on the V-type. 4. Great strides in engine manufacturing made old tooling obsolete. Since new tooling was needed on the larger engine, the advantage of a type change was indicated.
Technical Paper

Mode of Formation of Lead Deposits in Gasoline Engines

1953-01-01
530245
DEVELOPMENT of an effective technique for the study of the formation of combustion chamber deposits is described in this paper. The method is based on the extraction of samples from the end gas of an engine cylinder by means of an electromagnetic sampling valve, arranged to open over a narrow range of crank angles. Lead compounds in the sample are deposited on a nickel foil placed in the body of the valve. Subsequently, they are identified by X-ray diffraction or, if necessary, by analytical chemical methods. The samples provide data on the mechanism of scavenging, particularly on the various steps occurring between the first breakdown of tetraethyl lead and the formation of the final products. The technique also provides data on the exact mechanism of the antiknock action of tel.
Technical Paper

Effect of Combustion Time on Knock in a Spark-Ignition Engine

1953-01-01
530242
IF combustion of fuel-air mixtures is completed in an engine before chemical reactions have had time to take place, no knock-producing materials are formed - thus solving a chronic, critical problem. Knock can be controlled by using fuels in which reactions proceed at a slow rate. It can be reduced by speeding up the burning of the charge. The author of this paper has explored the relationship between combustion time and knocking tendency, and has reported the results of a number of new tests. He used a single-cylinder engine equipped with 17 spark plugs which were especially designed and fabricated for these tests. He shows how far octane requirements can be reduced under certain conditions. The decrease was found to be significant when combustion time was reduced by firing 17 spark plugs simultaneously instead of firing one plug in the normal location. The decrease was less when the combustion chamber contained deposits than when no deposits were present.
Technical Paper

Development of an Improved Automotive Diesel Combustion System

1954-01-01
540238
INCREASING fuel prices and fuel taxes have forced engine builders to find ways to better engine specific fuel consumption in order to help operators survive the onslaught of increased operating costs. This paper explains how an improved combustion system has yielded up to 15% improvement in fuel consumption. This system was arrived at by analysis of those previous combustion systems which held most promise. The resulting direct-injection open combustion chamber is described here.
Technical Paper

Occurrence of Preignition in Present-Day Cars in Normal Service

1954-01-01
540221
PREIGNITION is defined by Mr. Winch as the initiation of a flame front by some means other than the spark discharge at some point in the combustion chamber prior to the arrival of the normal flameat that point. He believes that wild ping is actually a combination of preignition and knock. His study of both 1952 and 1953 cars indicates that preignition has become a very serious problem. Moreover, in some cases, the problem was found to be more serious in the 1953 car of a particular make than in the 1952 model. In these studies preignition and wild ping were identified by a technique that makes use of the spark plug as an ionization gap.
Technical Paper

Deposit-Induced Ignition-Evaluation in a Laboratory Engine

1954-01-01
540220
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.
Technical Paper

THE EVALUATION OF THE EFFECT OF PROPYLENE IN PROPANE USED AS A MOTOR FUEL

1954-01-01
540185
The results of LPG motor fuel service tests in city busses of the Wichita Transportation Company are given which indicate that the inclusion of appreciable percentages of propylene in LPG motor fuel had no detrimental effects on the operation of city bus engines. Comparison tests between test fuel containing 15 per cent propylene and the fleet LPG motor fuel were conducted in six city busses operated for approximately 25,000 miles each in regular city route service. Evaluation of results in terms of change in Knock-limited spark advance during the test period and visual inspection of combustion chamber deposits were the basis of the conclusion that LPG motor fuels containing 15 per cent propylene afforded wholly satisfactory performance in this city bus service.
Technical Paper

A “QUICK LOOK” AT ENGINE COMBUSTION

1954-01-01
540193
High speed photographs of the combustion process in an engine equipped with a quartz window, in the cylinder head are described. The optical path was so arranged that direct and shadowgraph images of flames could be separately photographed on the same film at the same time in conjunction with flywheel timing marks. Simultaneous pressure-time records were also obtained. The photographs confirm the well-known fact that knock occurs immediately after the portion of fuel still unreached by the flame spreading from the spark plug spontaneously ignites and begins to burn very rapidly. Cylinder pressure then rises so fast that acoustic resonance develops in the combustion gases and is heard as knock. Four types of combustion phenomena in the engine were investigated: normal flames, “cool” flames, “hot” flames, and knock. With no spark ignition, cool flames start at the valve end of the L-head combustion chamber and end at the far side over the piston.
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