A small cubic closed vessel with schlieren measurement technique combined with high-speed video camera were used to study limit flame properties under microgravity conditions at atmospheric pressure and room temperatu...A small cubic closed vessel with schlieren measurement technique combined with high-speed video camera were used to study limit flame properties under microgravity conditions at atmospheric pressure and room temperature.The rich flammability limit of C3H8/air was determined to be 9.2% C3H8.Stretched flame propagation speeds,stretched laminar burning velocities and unstretched laminar burning velocities near rich C3H8/air flammability limits were measured at different equivalence ratios.Outwardly propagating spherical flames were used to study the sensitivities of the flame propagation speeds and laminar burning velocities to flame stretch using Markstein lengths.Unstretched laminar burning velocity at rich flammability limit was determined to be 1.09cm/s.Lewis numbers were less than unity in rich C3H8/air and negative Markstein lengths were concluded.Absolute values of Markstein lengths were found to decrease linearly with equivalence ratios increase.展开更多
In order to illustrate the combustion characteristics of RP-3 kerosene which is widely used in Chinese aero-engines, the combustion characteristics of RP-3 kerosene were experimentally inves- tigated in a constant vol...In order to illustrate the combustion characteristics of RP-3 kerosene which is widely used in Chinese aero-engines, the combustion characteristics of RP-3 kerosene were experimentally inves- tigated in a constant volume combustion chamber. The experiments were performed at four different pressures of 0.1 MPa, 0.3 MPa, 0.5 MPa and 0.7 MPa, and three different temperatures of 390 K, 420 K and 450 K, and over the equivalence ratio range of 0.6-1.6. Furthermore, the laminar combus- tion speeds of a surrogate fuel for RP-3 kerosene were simulated under certain conditions. The results show that increasing the initial temperature or decreasing the initial pressure causes an increase in the laminar combustion speed of RP-3 kerosene. With the equivalence ratio increasing from 0.6 to 1.6, the laminar combustion speed increases initially and then decreases gradually. The highest laminar combustion speed is measured under fuel rich condition （the equivalence ratio is 1.2）. At the same time, the Markstein length shows the same changing trend as the laminar com- bustion speed with modification of the initial pressure. Increasing the initial pressure will increase the instability of the flame front, which is established by decreased Markstein length. However, different from the effects of the initial temperature and equivalence ratio on the laminar combustion speed, increasing the equivalence ratio will lead to a decrease in the Markstein length and the stability of the flame front, and the effect of the initial temperature on the Markstein length is unclear. Further- more, the simulated laminar combustion speeds of the surrogate fuel agree with the corresponding experimental datas of RP-3 kerosene within ~10% deviation under certain conditions.展开更多
基金Supported by the Research Foundation of Beijing Institute of Technology(20070242004)
文摘A small cubic closed vessel with schlieren measurement technique combined with high-speed video camera were used to study limit flame properties under microgravity conditions at atmospheric pressure and room temperature.The rich flammability limit of C3H8/air was determined to be 9.2% C3H8.Stretched flame propagation speeds,stretched laminar burning velocities and unstretched laminar burning velocities near rich C3H8/air flammability limits were measured at different equivalence ratios.Outwardly propagating spherical flames were used to study the sensitivities of the flame propagation speeds and laminar burning velocities to flame stretch using Markstein lengths.Unstretched laminar burning velocity at rich flammability limit was determined to be 1.09cm/s.Lewis numbers were less than unity in rich C3H8/air and negative Markstein lengths were concluded.Absolute values of Markstein lengths were found to decrease linearly with equivalence ratios increase.
基金financial supports from the National Natural Science Foundation of China(No.51376133 and No.51506132)
文摘In order to illustrate the combustion characteristics of RP-3 kerosene which is widely used in Chinese aero-engines, the combustion characteristics of RP-3 kerosene were experimentally inves- tigated in a constant volume combustion chamber. The experiments were performed at four different pressures of 0.1 MPa, 0.3 MPa, 0.5 MPa and 0.7 MPa, and three different temperatures of 390 K, 420 K and 450 K, and over the equivalence ratio range of 0.6-1.6. Furthermore, the laminar combus- tion speeds of a surrogate fuel for RP-3 kerosene were simulated under certain conditions. The results show that increasing the initial temperature or decreasing the initial pressure causes an increase in the laminar combustion speed of RP-3 kerosene. With the equivalence ratio increasing from 0.6 to 1.6, the laminar combustion speed increases initially and then decreases gradually. The highest laminar combustion speed is measured under fuel rich condition （the equivalence ratio is 1.2）. At the same time, the Markstein length shows the same changing trend as the laminar com- bustion speed with modification of the initial pressure. Increasing the initial pressure will increase the instability of the flame front, which is established by decreased Markstein length. However, different from the effects of the initial temperature and equivalence ratio on the laminar combustion speed, increasing the equivalence ratio will lead to a decrease in the Markstein length and the stability of the flame front, and the effect of the initial temperature on the Markstein length is unclear. Further- more, the simulated laminar combustion speeds of the surrogate fuel agree with the corresponding experimental datas of RP-3 kerosene within ~10% deviation under certain conditions.
