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Japan Aerospace Exploration Agency

Aircraft engine combustor that uses a low-NOx fuel nozzle for high-pressure-ratio engines

The market needs environmentally friendly engines capable of complying with the stringent regulations that governments are beginning to apply to aircraft NOx (nitrogen oxide) emissions. JAXA has focused on the future aircraft engine market and developed combustors that use the lean-premixed method* of lean burn technology in an aim to meet the International Civil Aviation Organization (ICAO) standards (CAEP/4) for an 80% reduction in NOx emissions. In an experiment for a three-burner sector combustor (a multi-sector combustor that merges three combustors), JAXA confirmed a reduction of 82%, thus satisfying CAEP/4.

Although reduction in NOx has been confirmed, there are still issues which must be solved to realize practical implementation. One such example is technology for achieving stable engine combustion (performance at the time of oscillating combustion and low loads).

By realizing practical implementation of combustors which use low-NOx fuel nozzles made possible by lean burn technology developed by JAXA, in addition to acquiring important technology for the green engine technology being researched by JAXA, we will use this important technology to carve a new path for the Japanese aero-engine industry which has not been involved from the design stage for combustors and other core components in the development of private aircraft engines.

To realize this goal, JAXA is cooperating with manufacturers to overcome issues by revising the design for certain parts (liners, burners, etc.) of combustors and by verifying combustors in an annular shape (the same shape as actual aero-engines).

*Lean-premixed method
Burning fuel at a ratio that leaves no oxygen or fuel in the air after combustion creates high flame temperatures, which result in large NOx (nitrogen oxide) emissions. Lean-premixed combustion, which involves increasing the amount of air to ensure that the fuel and air mix at a ratio that does not exhaust the oxygen supply (a lean ratio), keeps flame temperatures down across the board and cuts NOx emissions by a sizable margin. As combustion of fuel with a uniform concentration tends to be unstable, JAXA has developed a lean-premixed combustion nozzle that places the main fuel mixers around the pilot mixer - the pilot light that serves to stabilize the arrangement.