EMICOPTER

Emission analysis. Tools required to perform the emission analysis and evaluation methodology

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 Obiettivo del progetto (Objective)

'The project aims to define an effective procedure to determine pollutant emission from helicopter engines during different flying conditions. The basis strategy is to couple detailed kinetics, needed to determine those components which are present in a low or very low concentration, with detailed fluidynamics necessary to describe in an accurate way the thermal and fluid flow fields, which control the pollutant formation/reduction. After an accurate analysis of the state of the art, starting point of the activity is the definition of the helicopter surrogate fuel and the development, tuning and validation of their combustion kinetics. The resulting detailed mechanism is the starting point for the construction of an optimized global few step kinetic mechanism to be used in CFD computations. The CFD simulations are based on the global mechanism, the combustor geometry and flying conditions. The temperature and flow field coming from CFD and the detailed kinetic scheme are the input for the postprocessing activity for the pollutant emission estimation. Effective and parallel numerical algorithms increase the performances of such a time consuming activity. Several CFD and postprocessing computations in the different flying allow to compare with experimental results. In this procedure some iterations could be necessary. The fluidynamic results can show the need of detailed and/or global kinetic refinements. As a consequence, the output of CFD computations can impact on detailed kinetic scheme development and validation and/or to the global few step mechanism. Again, over- or under-estimations of the emissions from postprocessor could require to revise either the kinetics or the CFD.'

Introduzione (Teaser)

EU-funded scientists developed a novel tool to evaluate pollutant emissions from helicopter engines.

Descrizione progetto (Article)

A European strategic research agenda has highlighted the role of rotorcraft as a competitive and affordable transportation mode for point-to-point connection. Gas turbine engines have therefore been subjected to stringent emission regulations regarding pollutant release.

As emissions are attracting increasing attention, researchers are working on developing computational tools that predict exhaust gas emission levels at varying flying and operating conditions. Against this backdrop, EU-funded scientists initiated the 'Emission analysis. Tools required to perform the emission analysis and evaluation methodology' (EMICOPTER) project to develop a powerful tool to predict emissions. This tool does not require tuning parameters making it more reliable, especially for predictions in conditions where no experimental information is available.

The project produced detailed models based on data from coupling fluid dynamics and kinetics that were used for computational fluid dynamic (CFD) simulations. CFD data was post-processed by a kinetic tool to accurately describe and predict pollutant formation during combustion. Detailed kinetics were also used to better describe the temperature field inside the combustor, thus improving emission calculation. As these computations require a significant amount of processing time, specific numerical algorithms were developed.

After an accurate analysis of state of the art, scientists defined a surrogate fuel and developed and validated its combustion kinetics. The resulting kinetic mechanism was the springboard for constructing a database for CFD computations. These were based on the combustor geometry of a specific helicopter engine. This particular engine was studied to characterise unburned hydrocarbon formation that reduces combustion efficiency and consequently increases fuel consumption and nitric oxide (NOx) emissions. NOx engine emissions were calculated for idle to take-off conditions and were compared to available experimental measurements.

Project results showed satisfactory agreement with experimental data and highlighted the importance of the kinetic mechanism used in the CFD simulation. The proposed approach can be used not only to evaluate the emissions from existing engines, but also to design new combustors with lower emissions.