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Technical Paper

Design of CROSS - FLOW HEAT EXCHANGERS from Tested Core Sections

THIS paper presents a simple and rapid method of determining the performance of cross-flow intercoolers, oil coolers, or Prestone radiators from laboratory tests of a model or basic unit of the cooler. The method lends itself equally as well to the determination of the size of a cooler of any set performance. Due to the comparative rapidity with which these calculations can be made, it becomes, with the use of this method, an easy matter to make a series of calculations to determine the relations between lengths, cooling air flow, and pressure drops, for any desired performance.
Technical Paper

The Influence of Engine Oils on Aircraft-Engine Performance

OIL cooling of aircraft powerplants is increasingly difficult. The weight and drag of the oil coolers necessary with the present maximum “Oil-in” temperature of 185 deg. fahr. (85 deg. cent.) are both decidedly objectionable. It appears possible to increase the “oil-in” temperature to about 220 deg. fahr. (104 deg. cent.) with oils which can be produced by the newer refining methods. The use of an “oil-in” temperature of 220 deg. fahr. would render possible a material reduction in weight, size and drag of oil coolers in comparison with present practice. Oils suitable for use at 220 deg. fahr. “oil-in” temperature would not be likely to cause a material increase of engine-starting difficulty, as they would only be used in summer when the shearing resistance of the oil has slight influence on engine starting. The approximate temperature cycle encountered by the oil in its passage through a modern aircraft-engine is discussed.
Technical Paper

High-Output Aircraft Engines

INDIRECT or liquid-cooled aircraft engines fit into the picture of future aircraft types better than do the direct or air-cooled engines, the authors contend. As reasons for their belief they draw attention to the small frontal area of this type; the heat capacity of the liquid in equalizing temperatures; and greater freedom in cylinder design because large heat-transfer surfaces are unnecessary. Rolls-Royce has been producing liquid-cooled aero engines for 23 yr, they announce, and has concentrated a large staff on installation problems. One of the results of this work, they report, has been the development of the interchangeable powerplant in which the engine-mounting auxiliaries and bulkhead form a complete detachable unit. These units, the authors explain, are interchangeable within 48 hr, and provide interchangeability between air-cooled and liquid-cooled engines.
Technical Paper


The development of air-cooled engines for aircraft never made much progress until the war, when the British attempted to improve the performance of existing engines by a series of experiments leading eventually to the development of aluminum cylinders with steel liners and aluminum cylinder-heads with a steel cylinder screwed into the head. The advantages of these constructions and the disadvantages of other types are discussed. Results are reported of tests at McCook Field on a modern cylinder-design of this type showing good results, that lead to the belief that large air-cooled engines will be produced in the near future, equal in performance to water-cooled engines of the same power.
Technical Paper

Effective Combustion as Determined from the Indicator Diagram

THE paper sets forth a simple and rapid method of obtaining from the indicator diagram data on how, when, and at what pressure combustion takes place in an internal-combustion engine. An indicator diagram predicated upon time-pressure is analyzed by superimposing on the normal diagram a diagram taken without ignition of fuel. This is done either by shutting off the fuel, or by short-circuiting the ignition, as the case may require, and immediately recording a second diagram on the card. Polytropic curves are then constructed on the card and their intersections with the curves of the ordinary diagram indicate the several percentages of effective combustion. Mr. Slonneger uses the term “effective combustion” to distinguish it from “complete chemical combustion” and from combustion losses due to conduction, radiation and leakage. A more technical analysis of Mr. Slonneger's method, according to thermodynamics and chemistry, is given in the Appendix.
Technical Paper

Ice Formation in Aircraft-Engine Carburetors

ICE formation in the carburetor must depend on, at least, the factors (a) volatility and heat of vaporization of the fuel; (b) mixture ratio; (c) humidity, pressure, and the temperature of the intake air; and (d) heat transfer between the carburetor and its surroundings, especially the engine, according to the authors. Small-scale and full-scale tests were made, descriptions of the seven fuels used and of the testing apparatus being given. The procedures for both sets of tests are outlined and the results are analyzed. Other subjects treated are the heat necessary to melt ice, and correlation with the A.S.T.M. distillation. Five conclusions are stated. Appendix 1 refers to calculation of the relation between intake and mixture temperatures when ice formation occurs. Appendix 2 treats of the construction of equilibrium-air-distillation curves for a series of supplied mixture ratios. Appendix 3 is concerned with engine operation near the danger zone and definition of border conditions.
Technical Paper

Fin and Cylinder-Baffle Design for Air-Cooled Engines

THE National Advisory Committee for Aeronautics has undertaken a research to determine the effect of the fundamental factors influencing the cooling of air-cooled radial engines. This paper presents some of the results of an investigation made to obtain information that can be used in the design of fins for the cooling of heated cylindrical surfaces in an airstream. An equation has been developed for calculating the quantity of heat dissipated by a given fin-design, using experimentally determined heat-transfer coefficients. The agreement between the quantity of heat dissipated, as determined by experiment and calculated by the equation, was found to be sufficiently close to justify its use. A method has been developed for determining the fin dimensions, utilizing a minimum of material for a variety of conditions of heat transfer, airflow, and metals.
Technical Paper

The Design of Metal Fins for Air-Cooled Engines

THIS paper gives the results of an analysis made to determine the proportions of aluminum and steel fins to dissipate maximum quantities of heat for several pressure differences across a finned cylinder. The power required to force the cooling air between the fins and the relative weights of the various designs are presented. The calculation of the heat flow in the fins is based on an experimentally verified, theoretical equation and the surface heat-transfer coefficients and pressure differences were taken from previously reported experiments. In particular, the analysis concerns fin proportions for minimum pressure drop, minimum power, and minimum weight.
Technical Paper


EVERY plow in use should have 10 b.-hp. available. Every tractor engine should deliver continuously at least 33 hp. If the 330-cu. in. engine mentioned were as good as a Liberty airplane engine, it could deliver 57 hp. at 1000 r.p.m. The horsepower actually obtained is as follows: 41.5 in the laboratory 33.0 at the factory 29.0 when burning gasoline 23.0 when burning kerosene 21.0 with poor piston-rings 19.0 with poor spark-plugs 9.5 available at the drawbar The great engineering problem of the future lies between the 57 and the 23 hp. From 19 to 9.5 hp. is the manufacturer's problem. The main difficulties, as outlined by the figures given, lie in the combustion chamber and its ability to dissipate the surplus heat, and in the limitations of fuel. There will be no need for refiners to continue to break up the heavier fuels by processes already so successful, if by ingenuity and good understanding of thermodynamics these can be made to burn in present-day engines.
Technical Paper


War service demanded that gasoline engines be absolutely reliable in minor as well as major details of construction; lightness of construction was second in importance. The war scope of the gasoline engine was so wide that engineers were forced toward the solution of unexpected and unrealized problems and a vast amount of valuable data resulted. This information includes recent determination of the quantitative nature of the factors governing thermodynamic performance in respect to mean effective pressure, compression ratio and the effect of volumetric efficiency; mechanical performance in regard to mechanical efficiency and internal friction; and engine balancing.
Technical Paper

Engine Types and Requirements for Preparation of Fuels

THERE are two main requirements as to proper preparation of the fuel charge for rapid combustion in our present engines: (1) The fuel must be vaporized, or in a similarly small order of subdivision, before ignition. (2) The fuel and air must be intimately mixed. Light fuels, such as our present aviation gasoline, may be vaporized in the carburetor and supercharger to quite a satisfactory degree, providing that the intake air is heated when flying at low temperatures. With this system, as we know, the air and fuel mixing is quite thorough. Heavier fuels, if released in the carburetor, may not vaporize in the intake-air flow, but instead may puddle and trickle on the side walls. Under such conditions, not only does the fuel fail to reach the cylinders in metered charges but also, if and when it should do so and if it vaporizes in the cylinder rather than getting on the cylinder wall, there is usually inadequate means for mixing the vapor with the air charge.
Technical Paper


THE Free-Piston Engine Program described in this paper was concerned with determining thermodynamic relationships of small, high-speed engines. The purpose was to establish proper engine geometry and mechanical design which could then be applied to developing larger automotive engines. The author outlines the problems encountered during the Program's beginnings: starting system, powerplant assembly, cooling system, and lubrication. The results indicated that the free-piston engine would be particularly applicable to the farm tractor. The author thinks that such a powerplant may equal or better the diesel engine in economy.
Technical Paper

Fuel Heat Gain and Release in Bomb Autoignition

NET interchange of heat between injected fuels and the atmospheres into which they were injected has been studied in a constant-volume combustion-bomb. These studies were undertaken to gain more information on the factors that govern the heating of injected fuels and the release of chemical energy in the autoignition process. The data show that chemical heat release occurs only after an appreciable interval of time during which the fuel is heated and may be partly or wholly vaporized. The rapidity of this heating — and associated ignition delay — are influenced markedly by the physical properties of the surrounding gas. Fuel volatility and chemical structure have relatively little influence on the rate of heat transfer to the fuel in the pre-reaction period.

Climate Control, 2010

Climate control is a defining vehicle attribute that has strong interaction with other vehicle systems. Also, performance and quality of the climate control system are critical to customer satisfaction. The 10 papers in this technical paper collection cover alternative A/C systems, multi-zone climate control, cabin air filtration, automatic controls, and optimized energy consumption.

Thermal Systems & Management Systems, 2007

Providing thermal comfort to the occupants and thermal management of components in an energy efficient way has challenged the automotive industry to search for new and innovative approaches to thermal management. Hence, management of heat flow, coolant flow, oil flow, and airflow is extremely important as it directly affects the system performance under full range of vehicle operating conditions. The 31 papers in this technical paper collection describe methods or concepts to increase efficiency, improve occupant comfort, improve test methodology and minimize the environmental impact of the climate control system; and thermal management components addressing design and/or application topics.

Climate Control, 2011

Climate control is a defining vehicle attribute. Performance and quality of the climate control system are critical to customer satisfaction. The 10 papers in this technical paper collection discuss recent advances in climate control. Topics covered include: alternative A/C systems, multi-zone climate control, cabin air filtration, automatic controls, and optimized energy consumption.

Thermal Systems Modeling and Simulation, 2011

The 13 papers in this technical paper collection focus on thermal systems modeling and simulation. Topics covered include: localized heating and cooling strategies for energy efficient HVAC system; interpretation tools and concepts for heat management in the drive train of the future; thermal management of lead acid battery (Pb-A) in electric vehicle; physics based approach of heat exchanger models for vehicle thermal simulation; and more.

Energy Efficiency of Thermal Systems, 2015

Proper thermal management can significantly contribute to overall system energy efficiency. This technical paper collection highlights the latest developments in thermal management energy efficiency.