Hideshi Yamada

Visualization of pilot flame of an optically-accessible coaxially-staged aero-engine lean-burn fuel injector

The visualization of the pilot flame of a coaxially-staged aero-engine lean-burn fuel injector, notxa0only downstreambut also inside of the pilot nozzle, was successfully performed at realistic aero-enginexa0conditions. Optical access toward the inside of the nozzle was achieved through the inner and outerxa0shrouds, both of which were made of transparent quartz. The image distortion caused by complexxa0contours of the two shrouds was corrected by a method based on optical ray tracing, which realizedxa0precise determination of spatial intensity distribution of optical signals. Line-of-sight OHxa0chemiluminescence, cross-sectional OH-LIF, kerosene LIF and kerosene Mie scattering were employedxa0as diagnostic tools. The effects of pilot local air-to-fuel ratio on spray flame structure werexa0revealed, both inside and downstream of the pilot nozzle under stable combustions. As the pilotxa0mixture got rich, the main reaction zone moved from inside of the pilot nozzle to the region nearxa0the injector lip downstream of the injector exit. The OH-LIF signal was detected near the centralxa0axis surrounded by the fuel spray. It was also observed near the back-step of the pilot nozzle forxa0the rich cases. The experiments under combustion oscillation were also conducted and thexa0correlation of phenomena inside and downstream of the pilot nozzle was captured. It was clarifiedxa0that the reaction enhancement in the outer part of the lip vortex region was caused by thexa0convectionof rich mixture, which appeared near the pilot atomizer lip at 150~210deg earlier oscillation phasexa0angle. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4752

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

Detailed Research on Rich-Lean Type Single Sector Combustor for Small Aircraft Engine Tested Under Practical Conditions Up to 3MPa

In the TechCLEAN project of JAXA, experimental research has 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. To investigate the performance of the combustor in detail, parametric experiments were conducted with single-sector combustors under additional test conditions in addition to design conditions of the target engine. Also the performance as a combustor for higher-efficient aircraft engine is examined by increasing inlet air pressure and temperature up to 3MPa and 825K in combustion tests. Obtained results of emission characteristics are discussed in this report.Copyright

Verification of Low NOx Performance of Simple Primary Rich Combustion Approach by a Newly Established Full Annular Combustor Test Facility

In the TechCLEAN project of JAXA, experimental research has been being conducted to develop a combustor for a small aircraft engine (with pressure ratio of about 20). The combustor was tuned to show the behavior of the Rich-Lean combustion through tests under atmospheric and practical conditions. And in 2006, by a designed multi-sector combustor, NOx emissions were reduced to lower than 42% of the ICAO CAEP4 standard. Based on the tuned combustor, full annular combustors were designed. In parallel, an experimental facility to test the full annular combustors under practical conditions was newly constructed in the spring of 2007. The inlet air conditions were set to the ICAO LTO cycle conditions of the target engine; 0.3–1.8MPa for pressure, 400–700K for temperature and 4–18kg/s for air mass flow rate. Through the full annular combustion experiments under practical conditions, the combustors were tuned to keep good combustion performance which was verified by the multi-sector combustors. The optimized full annular combustor finally achieved the following performance; NOx emissions were reduced to lower than 40% of the ICAO CAEP4 standard, maintaining low CO and THC emissions, good exit temperature profiles (P.T.F. = 0.19 at the take-off condition) and good lean blow-out performance (AFR>200 at the idle condition). The process of the optimization is discussed in this report.Copyright

Optimization of a Small Aircraft Combustor to Reduce NOx Emissions Under Practical Conditions

A series of research experiments under practical conditions has been conducted to develop a combustor for a small-class aircraft engine (with the pressure ratio of about 20). In the previous research experiments, including ignition and emission tests under atmospheric pressure, we applied a single airblast fuel nozzle and utilized the rich-burn quick-quench lean-burn (RQL) combustion approach. The combustor was tuned to show the behavior of the RQL under the atmospheric condition. In this paper, the results of single-sector combustor experiments under the practical temperature and pressure conditions are presented, in which RQL behavior is observed and NOx emissions in the ICAO (International Civil Aviation Organization) LTO (Landing and Take-Off) cycle are reduced to 45% of the ICAO CAEP4 (Committee on Aviation Environmental Protection 4) standard. Also the results of successive multi-sector combustor tests to optimize combustion performances with a more practical combustor configuration under the practical conditions are presented. The emission characteristics which are obtained are compared with those of the single-sector tests, and combustor size and configuration, air mass flow ratio and air hole positions are tuned through a series of multi-sector experiments. After the optimization, the combustor achieved the following performances; NOx emissions are reduced to less than 42% of the ICAO CAEP4 standard, CO and THC (Total Hydrocarbon) are reduced to those of 2% and 50% respectively, the lean blowout limit is kept over 220 AFR (Air to Fuel Ratio) at the idle condition and the exit temperature profile at the full load condition is sufficiently uniform (P.T.F.<0.15). The process of optimization will be discussed in this report.Copyright

Preliminary Experimental Research to Develop a Combustor for Small Class Aircraft Engine Utilizing Primary Rich Combustion Approach

A series of experimental researches, including ignition and combustion tests at atmospheric pressure conditions, were conducted to develop a combustor for a small class aircraft engine (with pressure ratio about 20). Under restrictions of the combustor size and cost, in order to satisfy the requirement for ignition and blowout performance with sufficient combustion efficiency and NOx reduction for wide range of operating conditions, we applied single fuel nozzles and utilized the rich-burn-quick quench-lean-burn (RQL) combustion approach. Preliminary combustion tests were conducted to optimize the ignition and blowout characteristics, approximately determining positions of air holes and igniter, and selecting fuel nozzle parameters. Consequently, tubular combustor tests with exhaust gas analysis were also conducted to optimize the air mass flow ratio and the air holes’ positions to suppress NOx emissions. Obtained results showing the RQL characteristics of the combustion, decreasing NOx emissions at high equivalence ratio range, are presented in this report, and the optimized air mass flow ratio and position of air holes, which will be applied to a single sector combustor for the testing at practical pressure and temperature conditions, are also presented.© 2006 ASME

Development of a Liquid-Fueled Dry Low Emissions Combustor for 300kW Class Recuperated Cycle Gas Turbine Engines

The authors have developed a liquid-fueled, low-emissions, and single can combustor for the RGT3R, Niigata’s 300 kW class industrial gas turbine engine, with the goal of satisfying the most stringent environmental requirements for distributed power generation systems in Japan. This paper describes these development efforts, which included non-reacting Computational Fluid Dynamics (CFD) analysis and component and engine tests. The emissions target is less than 24 ppm nitrogen oxides (NOx), 60 ppm carbon monoxide (CO) and 60 ppm unburned hydrocarbons (UHCs) at dry 15% O2 correction for kerosene, while operating above 50% load. A lean premixed, pre-vaporized, axially staged combustion concept is used to minimize emissions levels to the strictest emissions regulations in urban areas such as Tokyo, Chiba, Saitama, Yokohama, and Osaka. This combustion system involves two pilot burners and two main mixture injection tubes that are extending into the combustion chamber to inject lean to ultra-lean premixed mixtures into the hot burned gas from pilot burners. Counter rotational swirl vanes are provided to pilot burners and main mixture injection tubes to prevent flashback into the premixing tubes. The RGT3R gas turbine engine operates smoothly with the developed DLE combustion system from idle to full load without combustion-driven pressure oscillations. A two-stage fuel control system employs liquid fuel supply for the pilot and main atomizers. As this paper describes, the emissions data from this engine meet the emissions goals.© 2005 ASME

Low-NOx Emissions Over an Enlarged Range of Overall Equivalence Ratios by Staged Lean Premixed Tubular Flame Combustion

One of the inherent problems of lean premixed combustion is a narrow range of combustion-zone fuel-air ratios where low NOx emissions and complete combustion can be simultaneously achieved. The use of the reaction of lean to ultra-lean mixtures injected into the hot burned gas produced in the upstream lean-burn combustion zone can alleviate the abovementioned problem. The combustion characteristics of staged model gas turbine combustors with arranging two or three cylindrical swirl combustion chambers in series were investigated at atmospheric pressure. Tubular flame was stabilized in the primary stage and homogeneous mixture was injected into the burned gas from the upstream stage. It is shown that the lean multi-staged premixed tubular flame combustion has a potential to extend the range of gas turbine operation where both complete combustion and ultra-low NOx emissions can be achieved.Copyright