The spray and flow structures generated from the injectors of the lean premixed prevaporized(LPP)combustor are essential to the research and development of modern aero-engines.In this work,we develop an optical model ...The spray and flow structures generated from the injectors of the lean premixed prevaporized(LPP)combustor are essential to the research and development of modern aero-engines.In this work,we develop an optical model combustor featuring five linearly arranged LPP injectors and a laser diagnostics system based on high-repetition-rate and high-energy pulse lasers to study the spray and flow field characteristics.The effects of varying fuel and airflow rates on the spray cone area and droplet spatial distribution as well as on the mean flow structures and dynamics are experimentally investigated using high-speed particle image velocimetry(PIV),planar laser-induced fluorescence(PLIF),and planar MIE scattering(PMIE).The results demonstrate that the impingement of adjacent sprays is crucial to the formation of the outer recirculation zones(ORZ)among injectors.The fuel-to-air ratio(FAR)has an overall significant effect in controlling the flow and spray characteristics.The combined analysis of the velocity fluctuations and spray reveals that,with increasing FAR,the turbulent intensity diminishes in the shear layer,contributing to an inhibition of the liquid fuel breakup and eventually a deteriorated atomization performance characterized by the denser distribution of large-size droplets in the central recirculation zone.展开更多
Swirl combustion serves as a helpful flame stabilization method,which also affects the combustion and emission characteristics.This article experimentally investigated the effects of CO_(2)microjets on combustion inst...Swirl combustion serves as a helpful flame stabilization method,which also affects the combustion and emission characteristics.This article experimentally investigated the effects of CO_(2)microjets on combustion instability and NO_(x)emissions in lean premixed flames with different swirl numbers.The microjets’control feasibility was examined from three variables of CO_(2)jet flow rate,thermal power,and swirl angles.Results indicate that microjets can mitigate the combustion instability and NO_(x)emissions in lean premixed burners with different swirl numbers and thermal power.Still,the damping effect of microjets in low swirl intensity is better than that in high swirl intensity.The damping ratio of pressure amplitude can reach the maximum of 98%,and NO_(x)emissions can realize the maximum reduction of 10.1×10^(−6)at the swirl angle of 30°.Besides,the flame macrostructure switches from an inverted cone shape to a petal shape,and the flame length reduction at low swirl intensity is higher than that of high swirl intensity.This research clarified the control differences of mitigation of combustion instability and NO_(x)emissions by microjets in lean premixed flames with different swirl numbers,contributing to the optimization of microjets control and the construction of high-performance burners.展开更多
A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate ...A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate the emission performance of a liquid-fueled trapped vortex combustor （TVC） under lean premixed prevaporized （LPP） mode. When operating as an LPP system, a TVC is fueled both in the cavities and in the main stream. The correlations between the emission performance and the total ex- cess air ratio, the positions （4 positions） of the fuel injectors in the main stream, and the inlet temperature are obtained. Experimental results show that both the volume concentrations of unburnt hydrocarbon （UHC） and NOv （NO, NOxusually grouped together as NOx） increase with the increase of total excess air ratio from 1.5 to 3.0; the emission performance relies heavily on the position of the main stream injector, and the best perfomlance is achieved at Position 4 in the experiments, the increase of the inlet temperature impacts on the emission performance positively： the smallest volume concentrations of UHC and NO,. obtained in the experiment are 94×10^-6 and 2.3× 10 ^-6 respectively. This paper validates the feasibility of low emissions for an LPP/TVC and provides a reference for further optimization of TVCs.展开更多
This study is concerned with the experimental and theoretical investigation of the combustion instabilities in a premixed swirl combustor.It is focused on the effects of the swirl mixing distance on the intrinsic ther...This study is concerned with the experimental and theoretical investigation of the combustion instabilities in a premixed swirl combustor.It is focused on the effects of the swirl mixing distance on the intrinsic thermoacoustic mode.The swirler as an origin of the swirling flow is also the source of the flow disturbance,which has effects on the flame response.The location of the swirler is varied in the experiment to study the effect on combustion instabilities and flame transfer functions.A low order model is built to analyze the thermoacoustic instabilities of the combustion system.The experimental results show that the ITA switches from an unstable state to a stable state as the swirl mixing distance changes with an increment of 15 mm;while the instability of the quarter-wave mode is not varied.The measured Flame Transfer Functions(FTFs)show that the gain curves of the frequency-dependent FTFs seem to be stretched or compressed with the modulation of the swirler position,which has effects on frequencies and instabilities of thermoacoustic modes.With the low order model,the effects of flame response on combustion instabilities are analyzed and the flame dominant nature of the ITA mode is confirmed.展开更多
Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics ...Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.展开更多
ZK2000 is a newly developed 2 MW all radial gas turbine with an annular combustor. In this paper, the authors present the atmospheric test results of the combustor on test rig. Evaluation of several RANS turbulence mo...ZK2000 is a newly developed 2 MW all radial gas turbine with an annular combustor. In this paper, the authors present the atmospheric test results of the combustor on test rig. Evaluation of several RANS turbulence models and reaction models were used in order to determine which model was the most appropriate combination for comparison with the test results. FGM with SST were selected because of the better agreement with test results in terms of combustor temperature rise, primary zone temperature, liner metal temperature, and NO_x emission predictions.展开更多
The residual gas and remained raw gas in dual gas resources polygeneration system are quite complex in components(mainly CH_(4),CO,and H_(2)),and these results to the distinguished differences in combustion reaction.E...The residual gas and remained raw gas in dual gas resources polygeneration system are quite complex in components(mainly CH_(4),CO,and H_(2)),and these results to the distinguished differences in combustion reaction.Experimental investigations on basic combustion characteristics of syngas referred above are conducted on a laboratory-scale combustor with flame temperature and flue gas composition measured and analyzed.Primary air coefficient(PA),total air coefficient(TA),and components of the syngas(CS)are selected as key factors,and it is found that PA dominates mostly the ignition of syngas and NOx formation,while TA affects the flue gas temperature after high temperature region and NOx formation trend to be positive as H_(2)/CO components increase.The results provide references for industrial utilization.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.52206163,22227901,and 52006139)AECC Commercial Aircraft Engine Company,Ltd.
文摘The spray and flow structures generated from the injectors of the lean premixed prevaporized(LPP)combustor are essential to the research and development of modern aero-engines.In this work,we develop an optical model combustor featuring five linearly arranged LPP injectors and a laser diagnostics system based on high-repetition-rate and high-energy pulse lasers to study the spray and flow field characteristics.The effects of varying fuel and airflow rates on the spray cone area and droplet spatial distribution as well as on the mean flow structures and dynamics are experimentally investigated using high-speed particle image velocimetry(PIV),planar laser-induced fluorescence(PLIF),and planar MIE scattering(PMIE).The results demonstrate that the impingement of adjacent sprays is crucial to the formation of the outer recirculation zones(ORZ)among injectors.The fuel-to-air ratio(FAR)has an overall significant effect in controlling the flow and spray characteristics.The combined analysis of the velocity fluctuations and spray reveals that,with increasing FAR,the turbulent intensity diminishes in the shear layer,contributing to an inhibition of the liquid fuel breakup and eventually a deteriorated atomization performance characterized by the denser distribution of large-size droplets in the central recirculation zone.
基金This work was supported by the National Science Fund for Distinguished Young Scholars(Grant 51825605).
文摘Swirl combustion serves as a helpful flame stabilization method,which also affects the combustion and emission characteristics.This article experimentally investigated the effects of CO_(2)microjets on combustion instability and NO_(x)emissions in lean premixed flames with different swirl numbers.The microjets’control feasibility was examined from three variables of CO_(2)jet flow rate,thermal power,and swirl angles.Results indicate that microjets can mitigate the combustion instability and NO_(x)emissions in lean premixed burners with different swirl numbers and thermal power.Still,the damping effect of microjets in low swirl intensity is better than that in high swirl intensity.The damping ratio of pressure amplitude can reach the maximum of 98%,and NO_(x)emissions can realize the maximum reduction of 10.1×10^(−6)at the swirl angle of 30°.Besides,the flame macrostructure switches from an inverted cone shape to a petal shape,and the flame length reduction at low swirl intensity is higher than that of high swirl intensity.This research clarified the control differences of mitigation of combustion instability and NO_(x)emissions by microjets in lean premixed flames with different swirl numbers,contributing to the optimization of microjets control and the construction of high-performance burners.
基金Aeronautical Science Foundation of China(2008ZB52013)Funding of Jiangsu Innovation Program for Graduate Education(CXLX11_0211)
文摘A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate the emission performance of a liquid-fueled trapped vortex combustor （TVC） under lean premixed prevaporized （LPP） mode. When operating as an LPP system, a TVC is fueled both in the cavities and in the main stream. The correlations between the emission performance and the total ex- cess air ratio, the positions （4 positions） of the fuel injectors in the main stream, and the inlet temperature are obtained. Experimental results show that both the volume concentrations of unburnt hydrocarbon （UHC） and NOv （NO, NOxusually grouped together as NOx） increase with the increase of total excess air ratio from 1.5 to 3.0; the emission performance relies heavily on the position of the main stream injector, and the best perfomlance is achieved at Position 4 in the experiments, the increase of the inlet temperature impacts on the emission performance positively： the smallest volume concentrations of UHC and NO,. obtained in the experiment are 94×10^-6 and 2.3× 10 ^-6 respectively. This paper validates the feasibility of low emissions for an LPP/TVC and provides a reference for further optimization of TVCs.
基金supported the National Natural Science Foundation of China(Nos.51676126 and 51776191)。
文摘This study is concerned with the experimental and theoretical investigation of the combustion instabilities in a premixed swirl combustor.It is focused on the effects of the swirl mixing distance on the intrinsic thermoacoustic mode.The swirler as an origin of the swirling flow is also the source of the flow disturbance,which has effects on the flame response.The location of the swirler is varied in the experiment to study the effect on combustion instabilities and flame transfer functions.A low order model is built to analyze the thermoacoustic instabilities of the combustion system.The experimental results show that the ITA switches from an unstable state to a stable state as the swirl mixing distance changes with an increment of 15 mm;while the instability of the quarter-wave mode is not varied.The measured Flame Transfer Functions(FTFs)show that the gain curves of the frequency-dependent FTFs seem to be stretched or compressed with the modulation of the swirler position,which has effects on frequencies and instabilities of thermoacoustic modes.With the low order model,the effects of flame response on combustion instabilities are analyzed and the flame dominant nature of the ITA mode is confirmed.
文摘Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.
基金funded by the Key Programs of the Chinese Academy of Sciences (Project No. ZDRW-CN2017-2)National Natural Science Foundation of China No. 51306199
文摘ZK2000 is a newly developed 2 MW all radial gas turbine with an annular combustor. In this paper, the authors present the atmospheric test results of the combustor on test rig. Evaluation of several RANS turbulence models and reaction models were used in order to determine which model was the most appropriate combination for comparison with the test results. FGM with SST were selected because of the better agreement with test results in terms of combustor temperature rise, primary zone temperature, liner metal temperature, and NO_x emission predictions.
基金supported by the National Basic Research Program of China(No.2005CB221206).
文摘The residual gas and remained raw gas in dual gas resources polygeneration system are quite complex in components(mainly CH_(4),CO,and H_(2)),and these results to the distinguished differences in combustion reaction.Experimental investigations on basic combustion characteristics of syngas referred above are conducted on a laboratory-scale combustor with flame temperature and flue gas composition measured and analyzed.Primary air coefficient(PA),total air coefficient(TA),and components of the syngas(CS)are selected as key factors,and it is found that PA dominates mostly the ignition of syngas and NOx formation,while TA affects the flue gas temperature after high temperature region and NOx formation trend to be positive as H_(2)/CO components increase.The results provide references for industrial utilization.
