This paper discusses the problems involved in the design and development of an ejector cooling system for the XR-10 Helicopter power plant. Basic design problems are reviewed. Test experience on exhaust stacks, nozzles, mixing chambers, diffusers, baffles, carburetors and engines are discussed in detail.
TESTS conducted on a full-scale aircraft engine show that satisfactory engine operation can be obtained at warmed-up conditions with low-volatility fuels of the safety type. The engine used in the tests was modified for direct cylinder fuel injection, as fuels of this type are not sufficently volatile to be satisfactorily vaporized by means of a carburetor induction system. Knock-limited performance, specific fuel consumption, and oil dilution characteristics were studied in these tests.
THIS discussion of the problems encountered in designing the installation for the TG-180 in the P-84 Thunderjet is presented in the hope that other engineers designing installations for other turbojets may benefit from Republic's experiences. Problems discussed include provision for quick engine replacement; reduction of losses in the long inlet duct; development of a strong, tight joint for the tail pipe and engine; choice of thermal protection for the fuselage; provision for adjusting tail pipe area; and design of the fuel system. Several suggestions are made for improving the design of the engine from the installation standpoint.
DESCRIBED here is an intake metering injection system suitable for low-horsepower aircraft engines. Gasoline injection is said to have many advantages over carburetion for this class of engines, such as: 1. Complete elimination of manifold icing-one of the most troublesome problems in light engines equipped with carburetors. 2. Better idling characteristics. 3. Faster engine acceleration. 4. Lower maximum cylinder-head temperatures. 5. Better fuel economy. 6. Higher power. 7. Longer periods between overhauls. 8. Simplified engine cooling. 9. Flatter engine designs are possible.
USERS of internal-combustion engines have long recognized the need for a fuel which possesses high-octane rating, resistance to detonation, and ideal combustion characteristics; a fuel which would minimize engine maintenance costs, and which would be plentiful enough to assure long-range price stability. This paper cites propane, a common liquefied petroleum gas, as possessing all these and many more advantages. The author points out the safety factors in the sealed fuel system, the lessening of noise resulting from smooth performance, and the elimination of exhaust smoke and odors from a fuel which burns carbon-free and smokeless. Comparative charts are provided covering fuel costs, storage costs, and fleet operating expenses.
THE author believes that the flexible bladder-cell tank may be a good, practical solution to the fuel tank crash fire problem. He reports further that this type of tank need not carry with it an unreasonably high weight penalty. These tanks have successfully withstood some simulated crash tests corresponding to approximately 20g, so they are undergoing further tests to determine their ultimate crash strength. The opinions expressed in this paper are those of the author and do not necessarily represent the opinions of the Civil Aeronautics Administration.
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.
As reason replaces instinct in the development of mankind, much is gained. However, when one reads of the meteorologist, snowbound in an unpredicted storm, or sees with wonder how the robin annually beats an unfaltering 2000-mile course without chart or compass, one ponders the dubious advantages of the rational mind. An engine, they tell us, is the product of cold mathematical design reasoning, as inflexible as Newton's Laws, and it should act that way. But, to the test engineer, it sometimes appears as flighty and unpredictable as a prima donna at a public relations conference. En masse, they are even more capricious, acquiring individualistic qualities that challenge the best efforts of the inspector, as though in a deliberate effort to disprove the assumed equality of mass production birth.
UNKNOWN factors regarding fuel-injector performance have handicapped diesel-engine combustion studies in the past. Rate at which fuel is introduced into the engine cylinder and quantity of fuel available for combustion at any instant were two basic unknowns hindering advance. This paper presents results of an investigation aimed at measuring fuel-injector performance in a firing engine, simultaneously with obtaining pressure-time curves and other needed data. Method and instrumentation developed covers three characteristics of injector performance: 1. Rate of fuel injection. 2. Fuel-injection timing. 3. Injection pressures. The method results in obtaining more comprehensive data, but has the disadvantage of added complexities requiring skilled handling.
THE increasing importance of aerodynamic heating at elevated Mach number in relation to aircraft system design is illustrated in this paper, which is a study of the effects of aerodynamic heating on aircraft fuel systems. The fundamental physical behavior of fuel at elevated temperatures and relative effects on fuel system components are discussed. Differentiation is made between steady-state and transient aerodynamic heating of the fuel. A broad correlation is established between airplane performance and transient heating, and the general severity of the problem is established as a function of Mach number and fuel system parameters.
THIS paper discusses first the theoretical relation between thermal efficiency and fuel-air ratio for assumed limited-pressure fuel-air cycles. Data on actual cycles are then presented showing the relation of indicated efficiency to fuel-air ratio. This and other relationships are then used in deriving equations for relating the power output of engines operated at constant speed and throttle setting to ambient conditions. The fundamental nature of the relation between thermal efficiency and fuel-air ratio is emphasized by showing the variation with fuel-air ratio of computed efficiency of assumed limited-pressure fuel-air cycles. This computed efficiency for a given cycle and compression ratio is determined solely by the thermodynamic properties of the fuel-air medium and is the maximum efficiency theoretically possible for the assumed conditions.