Browsing by Author "Norster, E. R."

Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    'A design method for the dilution zones of gas turbine combustion chambers'
    (College of Aeronautics, 1966-02) Lefebvre, Arthur Henry; Norster, E. R.
    Introduction and Summary Perhaps the most important and, at the same time, most difficult Problem in the design and development of gas turbine combustion chambers, is that of achieving a satisfactory and consistent distribution of temperature in the efflux gases discharging into the turbine. In the past, experience has played a major role in the determination of dilution-zone geometry, and trial and error methods have of necessity been employed in developing the temperature-traverse quality of individual combustor designs to a satisfactory standard. Experimental investigations into dilution-zone performance carried out on actual chambers have led to useful empirical-design data, but very often it has proved difficult or impossible to distinguish the separate influences of all the variables involved. Thus although it is now generally accepted that a satisfactory temperature profile is dependent upon adequate penetration of the dilution jets, coupled with the correct number of jets to form sufficient localized mixing regions, the manner in which the total dilution-hole area is Utilized in terms of number and size of holes is still largely a matter of experience. Unfortunately, more basic studies of jet mixing do not usually yield results that can readily be expressed in the parameters which are most familiar to those concerned with combustion-chamber design. However, some of these investigations can provide a useful guide to the relationships involved. One such investigation resulted in the accumulation of a large amount of data on the mixing of cold jets when injected into hot streams under conditions where the temperature and velocity of the hot and cold streams, the injection-hole diameter, the angle of injection, and the mixing length could be accurately controlled and varied over a wide range. These data are used here, firstly to demonstrate a logical method of dilution zone design and, secondly, to provide quantitative data on the rate of exchange between temperature traverse quality and the relevant design parameters such as dilution zone length, dilution hole diameter and pressure loss factor. The effects of chamber inlet velocity and inlet velocity profile are also examined. Finally, it is proposed that the aerodynamic performance and stability of a combustion chamber may, for most practical purposes, be adequately described in terms of a parameter p which is the ratio of the flametube pressure loss to the overall pressure loss. Evidence is presented in
  • Thumbnail Image
    ItemOpen Access
    Drum atomisation studies
    (College of Aeronautics, 1964-09) Norster, E. R.
    Studies have been made into the behaviour of rotating drums as a means of atomisation and fuel injection for gas turbine engines. Radial holes in the wall of the drum discharge liquid continuously, forming jets which atomise on contact with the surrounding air. The effects of rotational speed, drum diameter, liquid flow rate and hole proportions have been investigated using water and kerosine. The flow and atomisation characteristics have been established and are discussed in terms of application to the gas turbine. It is apparent that savings in complexity, weight and hence cost of fuel systems may be achieved with drum atomisers, but these may be offset to some extent by the increased costs of full scale annular combustion chamber development.
  • Thumbnail Image
    ItemOpen Access
    Improvements in petrol engine performance with ultrasonic fuel atomisation
    (College of Aeronautics, 1966-02) Norster, E. R.
    Initial studies of the effect of air-fuel mixture preparation on piston engine performance have been conducted on a four cylinder 1600 cc petrol engine using conventional carburation and ultrasonic fuel atomisation. The performance of the engine, under various conditions of operation, has been assessed on the basis of specific fuel consumption and brake mean effective pressure. Whereas only minor differences in performance were found under full power condition at part throttle running of the engine with ultrasonic fuel atomisation improvements in fuel consumption in excess of 10% were observed. These improvements appear to be the direct result of better mixture preparation. Indirect benefits of improved mixture preparation may be a reduction in exhaust smoke and hydrocarbon emission from the engine.
  • Thumbnail Image
    ItemOpen Access
    Some experimental techniques in the study of flame stabilization
    (College of Aeronautics, 1964-02) Norster, E. R.; Lefebvre, A. H.
    The purpose of this note is to describe one or two techniques which are currently being used at Cranfield in various investigations into the effects of flameholder geometry and flow parameters on the process of flame stabilization. Much of the report is concerned with a description of the nitrogen dilution technique as a means of simulating low combustion pressures, and a comparison is made between this and the now established water injection technique. It is shown that many aspects of flame stability can be effectively studied by local injection of nitrogen directly into the combustion zone, with appreciable economies in the amounts of nitrogen required. A further application of this local injection method is also described which has proved useful in an investigation of the factors governing the amount of air entrained in the recirculation zone.
  • Thumbnail Image
    ItemOpen Access
    Some notes on a light scattering technique for measuring the mean droplet size of sprays
    (College of Aeronautics, 19) Norster, E. R.
    There is often great difficulty in measuring mean droplet size and drop size distribution in sprays because of sampling problems. This is particularly true if the spray is produced in the practical environment, for example in a high pressure combustion chamber, and the spray density is high. In recent years there has been a greater need to evaluate the characteristics of atomisers under such conditions and hence greater interest shown in optical methods which present the most convenient means for examining spray characteristics. It is not intended in this brief note to discuss in detail the principles involved with diffractive scattering methods of measuring mean droplet size, - this has been done very effectively elsewhere - but merely to outline some of the practicalities of producing a reliable instrument based on one method which has considerable promise. One of the early papers describing and evaluating this method was published by Dobbins, Crocco and Glassman in 1963, but the theoretical background on which the method is based was available much earlier … [cont.].