Combustors with Low Emission Levels for Aero Gas Turbine Engines

Abstract

The aircrafts are responsible for emitting several types of pollutants, especially the pollutants in the form of NOX, CO2, CO, UHC, SOX and Particulate Matter PM (smoke/soot). The impact of aviation emissions on the global is well known, where these emissions modify the chemical and microphysical properties of the atmosphere resulting in changes of earth’s climate system, which can ultimate in critical changes in our planet fragile ecosystem, also the pollutants produced by aircraft engines cause many health problems. This is why the International Civil Aviation Organisation (ICAO) is seriously seeking to control the emission levels by issuing new standards during the successive meetings of the Committee on Aviation Environmental Protection CAEP (CAEP/01 in 1986, CAEP/2, CAEP/4, CAEP/6, CAEP/8, etc). The new regulations include more stringent standards aimed to reduce emission levels, this led to increased interest in low emission technologies. In this paper, a comprehensive review of low emissions combustion technologies for modern aero gas turbines is represented. The current low emission technologies include the high Technologies Readiness Level (TRL) including RQL, TAPS, DAC and LDI. Also, there are advanced technologies at lower TRL including LPP, ASC and VGC.

Overview of low emission combustors of aircraft turbine drive units

“…The last combustor zone is the exhaust-air mixing and cooling zone. It can be concluded that throughout the combustion process in the combustor, the fuel-air mixture created and burned is in a lean state, which has a lower combustion temperature as a consequence, which permits to reduce the emissivity of the these combustors [6]. The LPP combustors must be adequately shaped to form a stable recirculation zone.…”

“…Compared to the LPP combustion chamber, the TAPS combustion chamber is characterized by greater flame stabilization safety by using a pilot flame on the low load of the drive unit. In addition, the combustion chamber is characterized by very low emissions of nitrogen oxides (NO x ); the third generation of TAPS combustors has reduced around 75% of nitrogen oxide (NO x ) emissions planned in the CAEP/6 [6]. Figure 4 shows the work principle of the TAPS combustor.…”

“…Given the structure and principle of work, its name "Rich-Burn, Quick-Mix, Lean-Burn" (RQL) can be justified. The result of this combustion process design is the reduced nitrogen oxide emissions (NOx) [6]. Figure 5 shows the scheme of the described combustor.…”

“…In turn, the lean combustion zone permits the elimination of hydrocarbons (HC) and carbon monoxide (CO) coming from the rich combustion zone. The combustor is designed in the way that the combustion process is either rich or lean, in order to reduce the stoichiometric combustion zone, which causes a higher combustion temperature and therefore greater emissions of nitrogen oxides (NO x ) [6]. Figure 6 shows the combustor analyzed above.…”

Experimental investigation into the effect of main stage swirl on flow and spray characteristics inside a stratified partially premixed combustor

“…Due to the increasingly stringent regulations for pollutant emissions published by International Civil Aviation Organization (ICAO), high efficiency and low pollution combustion have become important design standards for aeroengine gas turbine combustors. 1 Among numerous low pollution solutions, aeroengine manufacturers prefer the lean combustion technology due to its superior capability in reducing pollutants especially for thermal NOx. 2 Oriented by the lean combustion concept, several innovative combustors were invented and explored, such as GEnx TAPS (Twin Annular Premixing Swirler combustors) combustor, 3 Rolls Royce LDI (Lean Direct Injection combustors) combustor, 4 JAXA low NOx combustor 5 and Beihang TeLESS (Technology of Low Emission of Stirred Swirl) combustor.…”