Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter

Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene

Dual-Mode Combustion Experiments with an Integrated Aeroramp-Injector/Plasma-Torch Igniter

Results from combustion experiments in a direct-connect supersonic combustor facility are presented. Successful ignition and sustained combustion of both hydrogen and ethylene fuels were achieved using an integrated aeroramp-injector/plasma-torch igniter configuration. A Mach 2 nozzle was used to obtain How simulating Mach approximate to 4 flight conditions at 27 km, at a total temperature of 1000 K and a static pressure of 42 kPa. Combustion was achieved at (global) equivalence ratios between 0.08 and 0.31 for hydrogen and 0.13 and 0.47 for ethylene, with corresponding maximum combustor pressure rises of about a factor of 4.0. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 75% for both fuels, in the leanest conditions tested. Off-design flight conditions were tested by varying the freestream air total temperature. Supersonic combustion was achieved at total temperatures as low as 530 K with hydrogen and 680 K with ethylene

Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part II: Supersonic Flow

Fundamental aspects of mixing between two gaseous streams in a complex geometry are studied and discussed. In the present paper, a supersonic top-stream is expanded over a 30° ramp, through which a secondary lower-stream is injected. The mass flux through the secondary stream is purposely insufficient to provide the entrainment requirements of the resulting shear layer, causing it to attach to the lower guidewall. Part of the shear layer fluid is directed upstream forming a recirculation zone, with enhanced mixing characteristics. The pressure coefficient of the device is quantified as a function of velocity ratio. The effect of heat release on the pressure coefficient is also reported. Molecular mixing was measured employing “flip” experiments based on the hypergolic hydrogen-fluorine chemical reaction. The amount of mixing for the expansion-ramp geometry is found to be higher than in classical free shear layers. However, as in free shear layers, the level of mixing decreases with increasing top-stream velocity. Results for a similar configuration with subsonic/transonic flow in the top stream are reported in Part I of this two-part series

Molecular Mixing and Flowfield Measurements in an Expansion-Ramp Combustor: Supersonic Flow

This paper studies the level of molecular mixing and aerodynamic effects for supersonic flow in an "air" stream, with variable "fuel" mass injection and chemical heat release, in a flow configuration that has potential utility in dual-mode ramjet/scramjet combustors. "Fuel" is injected through a backward-facing expansion ramp at a rate insufficient to provide the entrainment requirements of the shear layer produced by the flow separation, which attaches to the lower guide wall. Part of the shear layer flow is directed upstream forming a recirculation zone that enhances mixing and provides flameholding benefits. Significant (passive) control authority over the flow is demonstrated by using variable mass injection through the ramp, and also by varying the level of heat release in the flow. molecular mixing was measured employing the hypergolic hydrogen-fluorine chemical reaction. The amount of mixing for the expansion-ramp geometry is found to be higher than in classical free shear layers. However, as in free shear layers, the level of mixing is found to decrease with increasing top-stream velocity

Molecular Mixing and Flowfield Measurements in an Expansion-Ramp Combustor: Supersonic Flow

This paper studies the level of molecular mixing and aerodynamic effects for supersonic flow in an "air" stream, with variable "fuel" mass injection and chemical heat release, in a flow configuration that has potential utility in dual-mode ramjet/scramjet combustors. "Fuel" is injected through a backward-facing expansion ramp at a rate insufficient to provide the entrainment requirements of the shear layer produced by the flow separation, which attaches to the lower guide wall. Part of the shear layer flow is directed upstream forming a recirculation zone that enhances mixing and provides flameholding benefits. Significant (passive) control authority over the flow is demonstrated by using variable mass injection through the ramp, and also by varying the level of heat release in the flow. molecular mixing was measured employing the hypergolic hydrogen-fluorine chemical reaction. The amount of mixing for the expansion-ramp geometry is found to be higher than in classical free shear layers. However, as in free shear layers, the level of mixing is found to decrease with increasing top-stream velocity

Molecular Mixing and Flowfield Measurements in a Recirculating Shear Flow. Part I: Subsonic Flow

The mixing and flowfield of a complex geometry, similar to a rearward-facing step flow but with injection, is studied. A subsonic top-stream is expanded over a perforated ramp at an angle of 30°, through which a secondary stream is injected. The mass flux of the second stream is chosen to be insufficient to provide the entrainment requirements of the shear layer, which, as a consequence, attaches to the lower guidewall. Part of the flow is directed upstream forming a re-entrant jet within the recirculation zone that enhances mixing and flameholding. A control-volume model of the flow is found to be in good agreement with the variation of the overall pressure coefficient of the device with variable mass injection. The flowfield response to changing levels of heat release is also quantified. While increased heat release acts somewhat analogously to increased mass injection, fundamental differences in the flow behaviour are observed. The hypergolic hydrogen-fluorine chemical reaction employed allows the level of molecular mixing in the flow to be inferred. The amount of mixing is found to be higher in the expansion-ramp geometry than in classical free-shear layers. As in free-shear layers, the level of mixing is found to decrease with increasing top-stream velocity. Results for a similar configuration with supersonic flow in the top stream are reported in Part II of this two-part series