EVENDALE, Ohio - With its GEnx jet engine, General Electric Company (GE) engineers are introducing breakthrough combustion technology that will dramatically reduce emissions in jet travel.
The GEnx engine is being developed for the new Airbus A350 and Boeing 787 aircraft. The GEnx enters airline service in 2008, and has already received more than $2 billion in orders on the strength of new technologies that make it the most fuel efficient, quiet, and low-emissions jet engine that GE has ever introduced for large jet aircraft.
The GEnx is part of GE's "ecomagination" products portfolio - GE's commitment to develop new, cost-effective technologies that will enhance customers' environmental and operating performance.
Lowering exhaust emissions in jet engines, especially oxides of nitrogen (NOx), will continue to be a worldwide requirement. With the GEnx, GE is at the forefront of that technology with a unique combustor called the Twin Annular, Pre-mixing Swirler (TAPS) combustor.
The combustor is the section of an engine where fuel is burned. GE has been maturing TAPS combustor technologies for almost a decade, and rig tests this year on the GEnx TAPS combustor have demonstrated very promising results. Here's how the TAPS combustor works:
The key to TAPS is how air and fuel are pre-mixed before they are burned in the combustor. Air from the high-pressure compressor is directed into the combustor through two high-energy swirlers adjacent to the fuel nozzles. This swirl creates a more homogeneous and leaner mix of fuel and air, which burns at lower temperatures than in previous jet engine designs.
The vast majority of NOx is formed by the reaction of oxygen and nitrogen at high temperatures; NOx levels are driven by the time that the burning fuel/air mixture stays at high temperatures.
The lower temperatures generated in the TAPS combustor results in significantly lower NOx levels. For example, at comparative thrust levels, GEnx NOx emissions will be more than 30 percent lower than the NOx emissisons of GE's highly popular CF6 engines powering commercial widebody aircraft today.
International jet engine emission standards will be lowered again in 2008. The GEnx emissions goal at entry into service is to be about 50 percent below the new established limits.
In addition to lowering ozone-depleting NOx emissions, GEnx's TAPS combustor will produce low levels of carbon monoxide, and unburned hydrocarbons. TAPS also has the potential to significantly reduce soot and related exhaust particulates. Also, because the TAPS combustor burns at lower temperatures, it will improve the life of components further downstream in the GEnx engine.
Although aircraft are only a minor source of the world's total level of NOx (EPA estimates aircraft at low-altitude operations created about seven-tenths of one percent of all NOx emissions in the USA) it is important to develop efficient and cost-effective, NOx-reduction technology for all sources.
The first full-engine testing of a TAPS combustor was completed on a CFM56-7B engine earlier this decade. The engine completed a grueling 4,000-cycle endurance test, after which the hardware remained in excellent condition. During component testing, the TAPS combustor demonstrated re-light capability at pressures equivalent to altitudes in excess of 30,000 feet. All of this experience was brought to the GEnx engine.
In February of this year, GE completed an extensive full-annular rig test with the GEnx TAPS combustor. It met all expectations in terms of emissions, efficiency, ignition, and durability. Using data from this test, the design has been further improved and will be validated in a second full-annular combustor test in the third quarter of 2005, paving the way for a full engine test in 2006.
Based on the architecture of the renowned GE90, the GEnx is the next-generation of engine technology to succeed GE's CF6, the best-selling engine for wide-body aircraft. Compared to the CF6 family, the GEnx will improve specific fuel consumption by 15 percent.
The GEnx is the world's only jet engine with a front fan case and fan blades made of composites for greater durability and weight reduction. It will operate with 18 fan blades (50 percent fewer than the CF6), which helps provide noise levels lower than any large commercial engine developed by GE.
To visually experience the GEnx TAPS combustor, click here to visit the GEnx Theater.