Power plants – Combustion products used as motive fluid – Combustion products generator
Patent
1991-02-19
1993-02-23
Bertsch, Richard A.
Power plants
Combustion products used as motive fluid
Combustion products generator
60759, F23R 304
Patent
active
051879379
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to gas turbine engine combustors having improved arrangements for the provision of air to the interior of the combustion chambers, especially improved arrangements for the provision of that air required for the cooling of the combustion products in the downstream zones within the combustion chamber but not solely these.
2. Discussion of Prior Art
The commercial drive for improved gas turbine engine performance, especially in aircraft engines, renders desirable an increase in turbine inlet temperatures for this would convey an increase in cycle efficiency. The scope for increasing engine efficiency by increase in turbine inlet temperature would seem to dwarf that which could be secured by improvements in aerodynamic design in the compressor and turbine sections. However in current generation engines, particularly advanced military aircraft engines, turbine inlet temperatures are already such as to impose a severe restriction on the useful life of turbine section components despite the use of the best of current generation materials and cooling arrangements within the turbine section. Moreover, at the same time as there is a drive for improved engine performance (as measured by specific fuel consumption) there is a parallel drive for improved component life both in current engines as well as those at the development stage. It is obvious that these two goals will be mutually incompatible unless there is some considerable improvement in engine materials or engine design.
One way in which significant improvements might be achieved without revolutionary change to engine designs or step advances in materials, is by providing a more uniform temperature within the turbine entry flow through improvement in the combustor. Certainly, it has been recognised for some time by those in the art that current generation engines (especially those of the annular combustor design) convey to the turbine a flow of gases having significant variations of temperature from point to point within the turbine entry. A consequence of this is that either the temperature capability of turbine section components, or their endurance, is not utilized to the full but wasted by local hotspots or the like which do not contribute in any way to cycle efficiency. Even when the mean turbine entry temperature is not excessive, stationary hot spots can damage individual turbine guide vanes and a poor radial temperature profile (i.e. across the annulus) can cause uneven degradation of aerodynamic components from root to tip. Considerable progress has already been made in the area of combustion chamber design having regard to those features of earlier designs which produced traceable and detrimental results. Despite these improvements made to date it would be typical for a current generation aircraft engine of the annular combustor type to exhibit an overall temperature distribution factor (OTDF) of say 25%. OTDF is a measure of the highest point temperature less the mean of point temperatures. A figure of 25% obviously means there is still room for improvement in this regard. It is likely however that a new approach to this aspect of performance will be required if any significant reduction of the 25% figure is to be secured.
It has been noticed in the art that in addition to those irregularities in temperature within the turbine entry flow of an annular combustor engine which are traceable to particular known origins within the combustor and can be avoided--such as problems caused by disruption of boundary layers--there is a significant degree of variation which has not been ascribed to any known origin. The term `randomness` has been coined to describe these variations. It is known for example that a particular engine might produce a hot spot (or spots) within the turbine entry field which is consistent in location from engine run to engine run and yet another engine made to the same construction might have its own peculiar hot spots different in location or intensity to th
REFERENCES:
patent: 2826039 (1958-03-01), Ashwood
patent: 2916878 (1959-12-01), Wirt
patent: 3919840 (1975-11-01), Markowski
patent: 4653279 (1987-03-01), Reynolds
patent: 4875339 (1989-10-01), Rasmussen et al.
Carrotte Jonathan F.
Stevens Stanley J.
Bertsch Richard A.
The Secretary of State for Defence in Her Britannic Majesty's Go
Thorpe Timothy S.
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