Combustion instability of pilot flame has been investigated in a model pilot bluff body stabilized combustor by running the pilot flame only. The primary objectives are to investigate the pilot flame dynamics and to p...Combustion instability of pilot flame has been investigated in a model pilot bluff body stabilized combustor by running the pilot flame only. The primary objectives are to investigate the pilot flame dynamics and to provide bases for the study of the interaction mechanisms between the pilot flame and the main flame. Dynamic pressures are measured by dynamic pressure transduc- ers. A high speed camera with CH＊ bandpass filter is used to capture the pilot flame dynamics. The proper orthogonal decomposition （POD） is used to further analyze the high speed images. With the increase of the pilot fuel mass flow rate, the pilot flame changes from stable to unstable state grad- ually. The combustion instability frequency is 136 Hz when the pilot flame is unstable. Numerical simulation results show that the equivalence ratios in both the shear layer and the recirculation zone increase as the pilot fuel mass flow rate increases. The mechanism of the instability of the pilot flame can be attributed to the coupling between the second order acoustic mode and the unsteady heat release due to symmetric vortex shedding. These results illustrate that the pilot fuel mass flow rate has significant influences on the dynamic stability of the pilot flame.展开更多
A direct performance comparison between the four-hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted.The mixing characteristics of two injectors were calculated by so...A direct performance comparison between the four-hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted.The mixing characteristics of two injectors were calculated by solving the three-dimensional(3-D)compressible Reynolds-averaged Navier-Stokes equations(RANS),with the help of the shear-stress-transport(SST)k-ωturbulence model.The numerical results show that the far field mixing efficiency of the aero-ramp injector is higher than that of the single transverse injector.High enthalpy vitiated air was heated to a total temperature of 1 200Kby hydrogen-oxygen combustion, entering the isolator entrance at a Mach number of 2.0.Non-reacting experimental conditions involved sonic injection of nitrogen to safely simulate ethylene injected into the combustor at a jet-to-free stream momentum flux ratio of 2.6.Schlieren photographs were obtained to analyze the shock structure around the injectors.Reacting test conditions involved sonic injection of ethylene at the jet-to-free stream momentum flux ratios ranging from 0.5to 2.7.High speed camera was used to capture the flame structures in the near-field combustion. The experimental results show that the aero-ramp injector produce sustained combustion over a wider range of fuel-air ratios than the single transverse injector.At the identical jet-to-free stream momentum flux ratio,the aero-ramp has a larger isolator margin than the single transverse injector,demonstrating a better ability for avoiding overflows.However,the air specific impulse and total temperature recovery of two injectors,which are calculated by the one-dimensional(1-D)performance analysis code,are almost identical.展开更多
The direct-connected supersonic combustor experiment is finished for kerosene fuel ignition in H_2/O_2 preheated impulse facility. The entrance parameter of combustor corresponds to scramjet flight Mach number 3.5. Ke...The direct-connected supersonic combustor experiment is finished for kerosene fuel ignition in H_2/O_2 preheated impulse facility. The entrance parameter of combustor corresponds to scramjet flight Mach number 3.5. Kerosene ignition is realized by using hydrogen as pilot flame. Wall pressure distributions of combustion are measured and flame photographs of ultraviolet ray are got. Experiment indicates that it is very difficult for kerosene fuel to realize self-ignition at low entrance temperature (below 900K) in supersonic combustor. Hydrogen pilot flame is one of the efficient methods for realizing kerosene ignition.展开更多
文摘Combustion instability of pilot flame has been investigated in a model pilot bluff body stabilized combustor by running the pilot flame only. The primary objectives are to investigate the pilot flame dynamics and to provide bases for the study of the interaction mechanisms between the pilot flame and the main flame. Dynamic pressures are measured by dynamic pressure transduc- ers. A high speed camera with CH＊ bandpass filter is used to capture the pilot flame dynamics. The proper orthogonal decomposition （POD） is used to further analyze the high speed images. With the increase of the pilot fuel mass flow rate, the pilot flame changes from stable to unstable state grad- ually. The combustion instability frequency is 136 Hz when the pilot flame is unstable. Numerical simulation results show that the equivalence ratios in both the shear layer and the recirculation zone increase as the pilot fuel mass flow rate increases. The mechanism of the instability of the pilot flame can be attributed to the coupling between the second order acoustic mode and the unsteady heat release due to symmetric vortex shedding. These results illustrate that the pilot fuel mass flow rate has significant influences on the dynamic stability of the pilot flame.
文摘A direct performance comparison between the four-hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted.The mixing characteristics of two injectors were calculated by solving the three-dimensional(3-D)compressible Reynolds-averaged Navier-Stokes equations(RANS),with the help of the shear-stress-transport(SST)k-ωturbulence model.The numerical results show that the far field mixing efficiency of the aero-ramp injector is higher than that of the single transverse injector.High enthalpy vitiated air was heated to a total temperature of 1 200Kby hydrogen-oxygen combustion, entering the isolator entrance at a Mach number of 2.0.Non-reacting experimental conditions involved sonic injection of nitrogen to safely simulate ethylene injected into the combustor at a jet-to-free stream momentum flux ratio of 2.6.Schlieren photographs were obtained to analyze the shock structure around the injectors.Reacting test conditions involved sonic injection of ethylene at the jet-to-free stream momentum flux ratios ranging from 0.5to 2.7.High speed camera was used to capture the flame structures in the near-field combustion. The experimental results show that the aero-ramp injector produce sustained combustion over a wider range of fuel-air ratios than the single transverse injector.At the identical jet-to-free stream momentum flux ratio,the aero-ramp has a larger isolator margin than the single transverse injector,demonstrating a better ability for avoiding overflows.However,the air specific impulse and total temperature recovery of two injectors,which are calculated by the one-dimensional(1-D)performance analysis code,are almost identical.
文摘The direct-connected supersonic combustor experiment is finished for kerosene fuel ignition in H_2/O_2 preheated impulse facility. The entrance parameter of combustor corresponds to scramjet flight Mach number 3.5. Kerosene ignition is realized by using hydrogen as pilot flame. Wall pressure distributions of combustion are measured and flame photographs of ultraviolet ray are got. Experiment indicates that it is very difficult for kerosene fuel to realize self-ignition at low entrance temperature (below 900K) in supersonic combustor. Hydrogen pilot flame is one of the efficient methods for realizing kerosene ignition.
