AviTech Reader

Well, its not like green is my favorite color…okay. It may be yours but it’s mother’s favorite. Did I just say mother? I meant Mother Earth! Under the social responsibility of corporate institution, is environmental responsibility and since most use already manufactured products, the buck stops with manufacturers in terms of materials and configurations used in component manufacture. However, the information has to be passed to consumers like airlines to ensure that the maintenance is done well to conserve and improve upon the parameters already included.

We know that Carbon (IV) oxide emissions is a function of the quantity of fuel burned. We need to focus more on the combustor where oxygen and fuel are mixed and burned if we have to reduce the noxious emissions that remain close to the ground like NO_X, uncombusted hydrocarbons, particulate emissions and aerosols and smoke . To address this, we have to look at injectors, swirlers and atomization of fuel. NASA’s Glenn Research Center has been at the forefront of work on improving injector combustion efficiency. At this center, engineers have been trying several injector configurations and air –mixing methods and have developed the Lean Direct Multi-point Injection (LDMPI).

Among the burning goals has been how to put maximum numbers of injectors in minimum areas to improve combustion-the more completely combusted the fuel, the less the emissions. Multi-point refers to the many different entry points of fuel into the combustor. Regulatory agencies like ICAO have set up stringent rules and standards for pollution that have to be met.

NASA has also gone ahead to burn three different types of fuel in LDMPI testing including two Fischer-Tropsch(F-T) and one biofuel. Although they didn’t really significantly change emission quantities, they solved the issue of clogging in combustors due to tinier injector tips as kerosene is burned. The tests were done at NASA’s Dryden Aircraft Facility and used DC-8 engines both main and auxiliary Power units.

Still, under Environmentally Responsible Aviation(ERA) program, there is a need to reduce cooling air necessary to regulate temperature of metallic combustion liner that can easily melt it if not for the cooling breeze. But then, the less air used for this cooling, the more we can utilize in combustion.

GE Aviation is using the lean/burn combustion to run the GEnx engine that powers the 787 and 747-8. GEnx-1B was meant to power the first flight of the Boeing 787, another variant of the engine being the Trent 1000 by Rolls-Royce based at Derbie. The other important feature of the GEnx is the Twin-Annular Premixing Swirler (TAPS) combustor whose efficiency at converting fuel to energy cuts polluting constituents. The most ideal conditions would be presence of infinite number of injector points for a very fine atomization but the reality is that engineers are limited by the number of injectors hence there will still be liquid droplets. Again, the fuel goes through the process in very few milliseconds that it can’t be converted to gas in such a short time. This is where TAPS comes in-to enable maximum vaporization to maintain lower temperatures and limit Nitrogen oxides whose generation are an exponential function of temperature(According to Steve Csonka-Technical Director of Advanced Programs and Environmental Strategy at GE Aviation).