Yoji Kurosawa

Emission Reduction of Fuel-Staged Aircraft Engine Combustor Using an Additional Premixed Fuel Nozzle

The Japan Aerospace Exploration Agency (JAXA) is conducting research and development on aircraft engine technologies to reduce environmental impact for the Technology Development Project for Clean Engines (TechCLEAN). As a part of the project, combustion technologies have been developed with an aggressive target that is an 80% reduction over the NOx threshold of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP)/4 standard. A staged fuel nozzle with a pilot mixer and a main mixer was developed and tested using a single-sector combustor under the target engines landing and takeoff (LTO) cycle conditions with a rated output of 40 kN and an overall pressure ratio of 25.8. The test results showed a 77% reduction over the CAEP/4 NOx standard. However, the reduction in smoke at thrust conditions higher than the 30% MTO condition and of CO emission at thrust conditions lower than the 85% MTO condition are necessary. In the present study, an additional fuel burner was designed and tested with the staged fuel nozzle in a single-sector combustor to control emissions. The test results show that the combustor enables an 82% reduction in NOx emissions relative to the ICAO CAEP/4 standard and a drastic reduction in smoke and CO emissions.

Combustion Characteristics of Fuel Staged Combustor for Aeroengines at LTO Cycle Conditions

In JAXA, combustion technologies have been developed with an aggressive target that is an 80% NOx reduction of CAEP/4. For the drastic reduction of NOx emissions, a fuel nozzle was designed based on the lean staged combustion concept. This paper describes single-sector combustor tests of a fuel staged combustor at ICAO LTO cycle conditions of an assumed engine with rated output of 40 kN and overall pressure ratio of 25.8. The results showed that the combustor enables a 77% reduction of the NOx standard of CAEP/4.Copyright

Performance of a Dry Low-NOx Gas Turbine Combustor Designed With a New Fuel Supply Concept

This paper describes the performance of a dry low-NO x gas turbine combustor designed with a new fuel supply concept. This concept uses automatic fuel distribution achieved by an interaction between the fuel jet and the airflow. At high loads, most of the fuel is supplied to the lean premixed combustion region for low-NO x , while at low loads, it is supplied to the pilot combustion region for stable combustion. A numerical simulation was carried out to estimate the equivalence ratio in the fuel supply unit. Next, through the pressurized combustion experiments on the combustor with this fuel supply unit using natural gas as fuel, it was confirmed that NO x emissions were reduced and stable combustion was achieved over a wide equivalence ratio range.

Investigations of a Staged Fuel Nozzle for Aeroengines by Multi-Sector Combustor Test

The reduction of NOx emissions from aeroengines is very important to protect the local air quality near the airports and prevent the climate change. ICAO CAEP has been stepped up the NOx standard frequently. Therefore, the engine manufacturers and national research institutes are actively working on the low-NOx technologies to meet the lower NOx emissions standard. JAXA is conducting research and development of the aeroengine technologies for the environmental adaptation in the TechCLEAN project. As a part of the project, combustion technologies have been developed with an aggressive target that is an 80% NOx reduction of CAEP/4. For the drastic reduction of NOx emissions, the fuel nozzles were designed based on the lean staged combustion concept. At first, five fuel nozzles were tested in a single-sector combustor at LTO cycle conditions of small aeroengine and it was confirmed that one fuel nozzle enabled 72% NOx reduction of CAEP/4. This lean low NOx fuel nozzle was tested in the present work in a multi-sector combustor at the same conditions with the single-sector combustor test. Test results showed that the combustor had combustion characteristics enabling 70% NOx reduction of CAEP/4, which was almost same with the single-sector combustor. For the improvement of combustion efficiency at middle power conditions, fuel staging among the main fuel injectors was also investigated at the MCL condition. The results showed that the fuel staging among the main fuel nozzles is effective to improve the combustion efficiency of the annular combustor.Copyright

Active control of combustion oscillations in a lean premixed gas-turbine combustor

Active control of combustion oscillations occurring in a methane-air lean premixed model combustor is accomplished by the method of secondary fuel injection. The main flame is sustained by an axial vane swirler. The central part of the swirler is endowed a function as the secondary fuel injector. The fuel jets from the injector enhance the flame stability by producing rich stable flames in the region of the flame base. Open-loop controls by secondary fuel injection with constant flow rates have been conducted on a naturally unstable condition. The results show sensitivity to the injection amount. It indicates that the flame base is very sensitive to the additional fuel distribution. A similar discussion is made on NOx emission also. Finally, a closed-loop control has been performed by implementing the mixed H2/H∞ controller. An obvious effect of the closed-loop control on the suppression of pressure oscillations is found without loosing an advantage for low NOx emissions.

Effects of Air Jets Through Combustor Liner Holes on Emissions of Lean Staged Combustor

In JAXA, combustion technologies have been developed with a target that is an 80% NOx reduction of the CAEP/4 standard. A lean staged fuel nozzle with a pilot mixer and a main one in a coaxial arrangement has been developed by single-sector combustor tests under LTO cycle conditions of the target engine with a total pressure ratio of 25.8.In this study, effects of air jets through combustion liner holes on combustion characteristics was investigated. Combustion tests were conducted by using four single-sector combustor liners with different air holes, no air holes, six air holes with short distance from the fuel nozzle, six air holes with long distance from the fuel nozzle, and one air flow path with three swirlers. From these results, air jets affect NOx emissions and combustion efficiency. Numerical analyses are also conducted by using a commercial large eddy simulation code, Front Flow Red. Quench of high temperature of pilot burned gas and NOx generation by air jets are captured by numerical simulations.© 2014 ASME

Evaluation of Lean Axially Staged Combustion by Multi-Sector Combustor Tests Under LTO Cycle Conditions of a Small Aircraft Engine

JAXA is conducting research and development on aircraft engine technologies to reduce environmental impact in the Technology Development Project for Clean Engines (TechCLEAN). As a part of the project, combustion technologies have been developed with an aggressive target that is an 80% reduction over the NOx threshold of the fourth Committee on Aviation Environmental Protection (CAEP/4) of the International Civil Aviation Organization (ICAO). Lean staged fuel nozzles have been developed and tested using a single-sector combustor under Landing and Take-off (LTO) cycle conditions of the target engine with a rated output of 40 kN and an overall pressure ratio of 25.8. A reduction of 82.2% in LTO NOx emissions relative to the ICAO CAEP/4 standard and drastic reductions in smoke and carbon monoxide (CO) emissions were resulted by single-sector combustor tests of a lean staged combustor with an additional premixed fuel nozzle (ECF: Emission Control Fuel nozzle). After the test, the pilot mixer of the single-sector combustor was improved and an additional 2.5% NOx reduction was achieved by combustion tests. As a next step, a multi-sector combustor with ECF was developed and tested. The test results show that the combustor enables a reduction of 82.2% in LTO NOx emissions relative to the ICAO CAEP/4 standard, though unburnt hydrocarbons (HC) and CO emissions are increased. Temperature distributions in the combustor exit plane were also evaluated.Copyright

Research and Development of Staging Fuel Nozzle for Aeroengine

Research and development of combustion technologies to reduce NOx emission of aero-engines to 20% of ICAO CAEP4 is progressing as a part of a project of JAXA (Japan Aerospace Exploration Agency), the Technology Development for Clean Engine (TechCLEAN). To realize such low NOx level on aero-engines, it is necessary to use not conventional combustion system such as rich-lean combustion but advanced one such as premixed combustion. We are conducting research and development of staging fuel nozzles that use diffusion combustion for the pilot nozzle and premixed combustion for the main nozzle. As the first step, five fuel nozzles were tested experimentally in the form of single-sector combustor. Test conditions were selected as the LTO cycle of presumed small-class engines. From the result of tests, to combine the combustion efficiency in low engine power condition and low NOx emission in high power one, fuel nozzle models that have triple contrary swirler are suitable. However, the combustion efficiency in 7%MTO is lower than that of current engines. It is necessary to decrease the emission of CO.Copyright

Emission Characteristics Through Rich–Lean Combustor Development Process for Small Aircraft Engine

Following increasing awareness of aircraft emissions and demand for technologies to reduce NOx emissions, experimental research has been conducted to develop a combustor for a small aircraft engine in the TechCLEAN of Japan Aerospace Exploration Agency project. The combustor was tuned to produce rich–lean combustion behavior through combustion tests, including full annular combustion experiments, under atmospheric and actual operating conditions of the target engine. Excellent combustion performance was observed. The final, optimized full annular combustor achieved a reduction of NOx emissions below 40% of the standard regulated by Committee on Aviation Environmental Protection/4 of International Civil Aviation Organization while maintaining low CO and total hydrocarbon emissions and showing superior exit temperature profiles and lean blow-out performance. Through the combustor development process, the dependence of combustion characteristics on combustor configuration was also clarified.

Influence of Injection Ratio of Dual-Injection Type Air-Blast Fuel Nozzle on Emission Characteristics Applied to Rectangular Single-Sector Combustor Under Atmospheric Condition

In the TechCLEAN project of JAXA, experimental research had been conducted to develop a combustor for a small aircraft engine. The combustor was tuned to show the behavior of the Rich-Lean combustion through tests under atmospheric and practical conditions. Finally, through full annular combustion experiments under practical conditions, the combustor was tuned to reduce NOx emissions to almost 40% of the ICAO CAEP4 standard, also sustaining low CO and THC emissions. In the developing process of above combustors, to simplify the combustor system, air blast type fuel nozzles with single fuel injection and dual swirlers were applied. Successively, in this report, the fuel nozzle is modified to dual fuel injection type with triple swirlers, aiming to control combustion performance under varying load conditions. Fuel is injected from inner and outer injection circuits, and the injection ratio between them is treated as one of the parameters.The combination of swirl direction of the three swirlers is selected at first through ignition and blowout tests. Secondly, spray patterns of the selected fuel nozzle are observed with different fuel injection ratios. Thirdly, the nozzle is applied to a rectangular single-sector combustor, and tested under atmospheric pressure with inlet temperature of 500K. NOx, CO, CO2, THC and O2 compositions in the exhaust gas are measured, and correlation among measured emissions data and fuel injection ratio is estimated to examine the influence of the injection ratio on combustion characteristics of the Rich-Lean type aero engine combustor.Copyright