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Inhaltsverzeichnis

Frontmatter

1. Introduction

Abstract
Aviation has become firmly established internationally both as a prime mover of passengers and a significant handler of freight. Journey times benefit from the characteristically high flight speeds, and also from direct routeing unimpeded by coastlines or mountain ranges. The high operating altitudes, while imposing their own problems of atmospheric conditions, minimise the costly and uncomfortable effects of weather. Since the vehicle has to be supported as well as propelled, the energies involved in aviation are high in comparison with slower forms of transport, with values of payload-range per fuel litre reaching only 0.06 and less than 0.01 respectively of the corresponding values for buses and supertanker ships. The impact of recent turbulences within the oil world has underlined the key role of the fuel element in airline technical accounting, and in effective military operations. In civil aircraft, for example, the (fuel/direct operating) cost ratios have increased from 0.25 in the early 1970s to about 0.60 today. The cost effectiveness of aviation fuels is therefore a key factor in the future viability of aviation in general, and the airline industry in particular.
Eric Goodger, Ray Vere

2. Current Aero Engine Types

Abstract
Propulsion within a fluid environment is generally achieved by the thrust created as a reaction to the rearward acceleration of a fluid jet. Fluid acceleration can arise either by driving a system of rotating vanes, or by releasing heat directly into the fluid flow within a duct coupled with change in cross-sectional area along the axis of the duct. The former method is employed with the combination of aero piston engine and propeller, and the latter with the various types of ramjet and rocket engine. Turbopropeller, turbofan and turbojet engines, in that order, represent gradation from the former to the latter method. Although a claim for being ‘first’ with any development in aeronautics can lead to controversy, since it depends largely on the definitions of ‘flight’ (height reached, distance covered, time airborne, speed attained etc.), the following years mark notable early uses of the different aero propulsion engine types:
1232
Rockets, Kai Feng, China
1903
Piston engine in Wright Flyer, U.S.A.
1939
Turbojet (von Ohain) in Heinkel He 178, Germany
1942
Pulsejet (Schmidt-Argus) in V1 weapon, Germany
1945
Turboprop (Derwent 2) in converted Gloster Meteor, U.K.
1947
Ramjet (Leduc 0–10), France
Eric Goodger, Ray Vere

3. Current Aviation Fuel Types

Abstract
The nature of the fuel best suited to each type of propulsive engine is determined principally by the characteristics of combustion in that engine, but all aviation fuels must also meet the requirements of the aircraft fuel system, the distribution system, and the financial climate generally. The two major groups of aviation fuels that have developed in the above context are discussed below.
Eric Goodger, Ray Vere

4. Production

Abstract
Aviation fuels can be produced from most crude oils, but the yields will vary according to the source. Crude oils consist of mixtures of many thousands of hydrocarbons, each of which has its own discrete chemical and physical properties. The physical property that is used initially in the refining of crude oil is boiling point. It is clearly not practicable to separate hydrocarbons individually, but they are divided by a process of distillation into product groups or ‘fractions’ boiling within pre-determined temperature ranges. These fractions are described as ‘straight-run’, and various processes are then used to refine the properties to meet their required quality. As seen in the previous chapter, the two major groups of product concerned in this study are the various grades of aviation gasoline, blended for use in aero piston engines, and of aviation kerosines for use in aero gas turbine engines. The initial distillation process, and the subsequent process routes for these two fuel groups, are discussed below.
Eric Goodger, Ray Vere

5. Specification Test Methods

Abstract
The combined expertise derived from fuel production, handling and use permits a pattern of property limitations to be specified which together help balance the opposing demands for satisfactory performance, production availability and cost control. In the event of a problem in service, the tightening of existing limits and/or the need for limits on additional properties are investigated. Conversely, fuel availability and costs are generally improved if easement of existing limits is found to be practicable.
Eric Goodger, Ray Vere

6. Operational Handling

Abstract
In the previous two chapters, production methods were dealt with and the resulting product was isolated, tested and certified as meeting the required specification. The product, however, is still within the refinery, and the next stage is to move the product towards the aircraft where it will be used. In doing so, it is most important that it does not become contaminated with dirt, water or any other product. To ensure that this does not happen or, should it do so, that the contamination is detected and the product not used in aircraft, a strict handling procedure is observed.
Eric Goodger, Ray Vere

7. Fuel Characteristics within Aircraft Fuel Systems

Abstract
The development of aircraft and aero engines has not been without its problems. Some of these have been overcome by design and engineering modifications, but others needed modification of the fuel, normally by tightening the specification and making it more restrictive.
Eric Goodger, Ray Vere

8. Fuel Combustion Performance

Abstract
The overall process of combustion of fuel for the generation of power by an open-circuit heat engine comprises the metering of the fuel to the combustion chambers, the preparation of the fuel-oxidant mixture, initiation of ignition, propagation and/or stabilisation of the flame, and subsequent emission of the products. The devices or complete systems used for engine fuel metering represent a separate study, and are covered elsewhere. The remaining topics are determined largely by the type of engine and combustion adopted, and are outlined individually in the following sections.
Eric Goodger, Ray Vere

9. Development of Specifications

Abstract
The history of aviation fuel specifications, both gasoline for piston engines and turbine fuel for gas turbine engines, is based on operational need and on petroleum technology to supply the quality and quantity required.
Eric Goodger, Ray Vere

10. Relaxation of Specifications

Abstract
Specifications, as stated in chapter 5, are formed by balancing the demands of satisfactory performance, production availability and cost control that arise from the combined experience of fuel production, intermediate handling and use. As long as crude oil was readily available at reasonably low cost, the fuel quality tended to be a performance specification.
Eric Goodger, Ray Vere

11. Aviation Fuels from Alternative Sources

Abstract
Since the earliest days of powered flight, aviation fuels have invariably been derived from petroleum, hence both the continuity of petroleum supply, and the subsequent availability of suitable alternative sources, are of concern for the long-range future of aviation itself. The events of 1973 and 1979 brought sharply into focus the finite extent of fossil fuels, together with the vulnerability of extraneous sources of supply. The fuel embargo of 1973 did, in fact, give rise to shortfalls in suitable crudes, and supplies of commercial aviation turbine fuels were maintained only by the adoption of temporary waivers, as discussed in chapter 8 which, in the event, showed no significant differences in combustion chamber liner temperatures or smoke formation1. These waivers were then seen to be incorporated in the subsequent specifications.
Eric Goodger, Ray Vere

12. Aviation Fuel Substitutes

Abstract
Previous chapters have indicated that petroleum, the main source material for aviation fuels, must be expected to approach exhaustion within the next few decades, and that comparable fuels may well be derivable from such alternative sources as shale, tar and coal. Much development work awaits completion before these ‘alternative-source’ fuels become available in sufficient economic quantities to supplement effectively the conventional aviation gasolines and kerosines. Furthermore, the price differential will clearly remain unfavourable until quantity production is established and, probably, conventional fuels continue to become more expensive.
Eric Goodger, Ray Vere

13. Fuels for High-Performance Flight

Abstract
In aircraft propulsion, ‘high performance’ generally represents a particularly high engine thrust sustainable for such purposes as high rate of climb, high altitude operation, supersonic or hypersonic aircraft speed, or any other special condition where engine power takes precedence over fuel economy. The discussion in chapter 2 illustrated the logical progression in aero engine design from piston engine through turbine, ramjet and rocket engines, and this chapter therefore is concerned with the latter members of the range. The operating regimes of these aero engine types were shown in figure 2.1.
Eric Goodger, Ray Vere

14. Conclusions and Prospects

Abstract
This study has reviewed the current situation with regard to aviation fuel quality arising as the dynamic resultant between the constraints of supply and the requirements of demand. It also comments briefly on both the immediate historical background to this situation, and the alternatives that offer future potential. Aviation fuel quality and availability are seen to be influenced by such technological factors as production techniques, component control, measurement precision and the various aspects of service performance. Additional factors include the supply and demand of non-aviation fuels, particularly motor gasoline and diesel fuels, and thus the relative cost values of each of these products. In turn these costs, which have become of crucial importance in airline finances, are dominated by taxes, regulations and matters of a political, and possibly military, nature. An accurate prediction of the fuel quality likely to be available from the year 2000 is needed now to give the direction for future engine, fuel system and airframe design, research and development programmes. A new design concept started now will not be ready for commercial production until after the turn of the century. This prediction could also determine the potential life of existing equipment since it will highlight those modifications that will need to be carried out to operate on these fuels.
Eric Goodger, Ray Vere

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