During the 3 year interim phase of the programme three selected concepts
will be investigated in detail,
their potential of NOx reduction will be measured and
an evaluation of these methods concerning air worthiness will be performed.
Theme I: Rich Burn, Quick Quench, Lean Burn Combustion (RQL)
The design and development of a rich burn combustor (RQL) were supported by tubular combustor tests, by flow visualization in perspex models and by extensive measurements in a rectangular sector combustor. The specific problems resulting from extreme temperatures in the rich burning zone and the need for rapid quench in the zone to follow were addressed by a specific cooling task.
Theme II: The Lean, Premixed and Prevaporized Combustion (LPP)
For the development of a lean premixed, prevaporized combustor (LPP), fundamental investigations were concentrated on prevaporizer ducts and the premix systems. Because of the particular problems caused by reverse flow layout and the requirements for small size and low cost inherent with small engines, the combustor investigations were split into two tasks: ducts for large engines and ducts for small engines.
Theme III: The Double Annular Combustor (DAC)
The investigations of the double annuar combustor (DAC) such as lean stability, altitude relight, low power efficiency and NOx control, fuel staging and combustor exit temperature distribution were of more basic nature. While these fundamental tests were carried out in low pressure and intermediate pressure rigs, the final configuration experiments were conducted under engine relevant conditions.
Theme IV: Validation of CFD-Combustion Models (CFD)
The results of selected measurements were added to a common database which could be used to evaluate the tests, compare the different combustor standards and to numerically predict and optimize the behaviour of the different combustors with advanced CFD methods.
The results from the Low NOx II programme confirm that assuming the requisite research work is continued in future and the development of appropriate combustors is initiated and progress demonstrated, a reduction of 60 % to 80 % in nitrogen oxides from current levels appears to be feasible by the end of the century.
Further objectives of the low emission combustor programme in the interim phase comprise
the strengthening of the scientific and technological basis for the development of ultra low NOx combustion methods and
the provision of new or improved tools and techniques for analysis, prediction and control of aero engine exhaust emissions.
However, the major long term objective for the Low Emission Combustor team is the translation of the best suited concepts into a practical combustor and to test it at engine operating conditions, which requires both a reliable continuation of the research work and sufficient financial support of the partners involved.
Funding SchemeCSC - Cost-sharing contracts
80038 Pompigliano D'arco
MK43 0AL Cranfield - Bedfordshire
86961 Chasseneuil Du Poitou
SW1E 6AT London
GU14 0LS Farnborough