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Greener lean-burn engines

Nitric oxide (NO) and nitric dioxide (NO2) are often collectively referred to as NOx when discussing air pollution and emissions. An innovative project by EU-funded researchers led to development of greener lean-burn engines to reduce the NOx from fuel combustion.

Climate Change and Environment

NOx are by-products of combustion reactions such as those occurring during the ignition of fuel in a car’s engine. NO2 in particular contributes to ground-level ozone, the main component in smog, and is linked to a number of adverse effects on the respiratory system. The EU has set ambitious targets corresponding to an 80 % reduction in NOx emissions by 2020. The ‘Integrated lean low emission combustor design methodology’ (Intellect D.M.) project was designed to develop new technology for combustion engines based on lean-burn technology combined with low emissions and effusion cooling devices for leaner, greener engines. Lean-burn engines use less fuel for a given amount of air (hence, lean), thus being more cost-effective in terms of fuel consumption and releasing fewer greenhouse gases (GHG). However, the higher pressures and temperatures required increase NOx emissions. The research team set out to capitalise on the pros of the lean-burn engine while minimising the NOx emissions. Lean-burn engines, although using less fuel, are able to generate the same power output as standard combustion. They burn the fuel efficiently based on a combination of air swirl conditions at the intake and precise fuel injection, leading to more complete mixing of fuel and air. The researchers developed a knowledge-based engineering (KBE) tool key to applying lean, low-NOx design technology. They included a combustor, a parametric injector, computational fluid dynamics (CFD) simulations and optimisations reducing computer computation time. Turbomeca, a French manufacturer of gas turbine engines, has already used the results to enhance the performance of low-NOx injection technologies for small gas turbine applications. In summary, the Intellect D.M. project contributed an important modelling and simulation tool for design of lean-burn, low-NOx emission combustors capable of strengthening EU competitiveness by reducing development time and cost. In addition, the new combustors, both lean and green, should be particularly attractive to an increasingly environmentally sensitive consumer population. Turbomeca may be among the first to implement project outcomes, but they are certainly not going to be the last.

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