| dc.description |
In the post most of the research work carried out in gas turbine
combustion was mainly concerned with performance problems arising at
high altitudes. these were primarily problems of trying to achieve
high combustion efficiency, adequate stability and good relighting
performance. This research necessitated the use of expensive test
facilities to provide large quantities of air at sub atmospheric pressure.
For this reason much effort was expended in trying to find methods of
simulating low combustion pressures, and in the development of
correlating parameters which would allow low pressure performance to be
predicted from experimental data obtained at more convenient levels
of pressure.
In recent years, however, there has been a marked trend towards
engines of higher compression ratio. This is illustrated in figure 1
which was reproduce& from a paper by Pearson. This trend has not
produced any new problems, with the possible exception of exhaust smoke,
but it has aggravated many problems which previously caused no great
concern, and it has exposed many deficiencies in our knowledge of
certain basic processes, particularly those affecting combustion and
heat transfer at high pressure. One object of this paper is to examine
the influence of pressure on various aspects of combustion performance.
Another object is to derive formulae from which the influence of
increasing pressure on various performance criteria can be estimated.
One important effect arising at high pressures is an increased
dependence of all aspects of combustion performance on fuel spray
characteristics. Because of their importance and because so far they
appear to have received comparatively little attention, much of this
paper is devoted to the effect of pressure on various spray properties
such as penetration, droplet size and cone angle. |
|