Liquid fuel is the choice for volume-limited propulsion systems, including detonation-based propulsion. A liquid fuel with high vapor pressure has the advantage of more fuel vapor in the mixture, which supports the transition from deflagration to detonation. This paper reports on an experimental study of deflagration-to-detonation transition (DDT) in a pulse detonation engine with heterogenous mixtures of oxygen and ethanol or acetone. Single-cycle tests were taken for different fuels, equivalence ratios, and DDT enhancement methods. The size distribution of fuel droplets was characterized at the atomizer and engine exit. The effect of the fuel evaporation was dominant for the acetone spray only. Comparing the measured detonation velocities of the two mixtures, a lower velocity deficit relative to the theoretical Chapman–Jouguet detonation velocity was measured for the acetone–oxygen mixtures, and this behavior is related to the higher amount of fuel vapor that existed in the mixtures. Moreover, a shorter transition to detonation was observed in the acetone–oxygen mixture. The addition of a Shchelkin spiral reduced the DDT distance; however, the Chapman–Jouguet condition could be reached only downstream of the obstacle. The measured detonation cell size of the heterogeneous acetone–oxygen mixture was smaller than that of the ethanol–oxygen mixture, indicating that it is more detonable.
{"title":"Deflagration to Detonation Transition in Heterogeneous Mixtures Containing Ethanol/Acetone and Oxygen","authors":"H. Kadosh, D. Michaels","doi":"10.2514/1.b39154","DOIUrl":"https://doi.org/10.2514/1.b39154","url":null,"abstract":"Liquid fuel is the choice for volume-limited propulsion systems, including detonation-based propulsion. A liquid fuel with high vapor pressure has the advantage of more fuel vapor in the mixture, which supports the transition from deflagration to detonation. This paper reports on an experimental study of deflagration-to-detonation transition (DDT) in a pulse detonation engine with heterogenous mixtures of oxygen and ethanol or acetone. Single-cycle tests were taken for different fuels, equivalence ratios, and DDT enhancement methods. The size distribution of fuel droplets was characterized at the atomizer and engine exit. The effect of the fuel evaporation was dominant for the acetone spray only. Comparing the measured detonation velocities of the two mixtures, a lower velocity deficit relative to the theoretical Chapman–Jouguet detonation velocity was measured for the acetone–oxygen mixtures, and this behavior is related to the higher amount of fuel vapor that existed in the mixtures. Moreover, a shorter transition to detonation was observed in the acetone–oxygen mixture. The addition of a Shchelkin spiral reduced the DDT distance; however, the Chapman–Jouguet condition could be reached only downstream of the obstacle. The measured detonation cell size of the heterogeneous acetone–oxygen mixture was smaller than that of the ethanol–oxygen mixture, indicating that it is more detonable.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44185231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Experimental Characterization of a Hollow Cathode with Iridium–Cerium Alloy","authors":"Hiroki Watanabe, Shinatora Cho, Yoshiki Matsunaga, Yasushi Ohkawa, Yu Tao, Fumiaki Kudo, K. Koga, Satoshi Yabu","doi":"10.2514/1.b38511","DOIUrl":"https://doi.org/10.2514/1.b38511","url":null,"abstract":"","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41510330","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yunping Zhang, Lee Organski, A. Shashurin, K. Ostrikov
A coaxial low-energy surface flashover (LESF) ignitor for CubeSat electric propulsion systems was developed and tested. The ignitor features a coaxial geometry with copper electrodes directly bonded to the inner and outer surfaces of the alumina ceramic tubular insulator. The ignitor proved to be operational throughout (and after) an extended duration test of 10 million pulses. Characterization of a single LESF event via intensified charge-coupled device fast photography showed that the initial plasma was generated along the insulator surface, while the later plasma production was governed by the column attached to the copper electrodes. The plasma plume propagated primarily perpendicular to the insulator surface at around [Formula: see text]. Further investigation on the erosion of ceramic insulator and copper electrodes via energy-dispersive x-ray spectroscopy analysis of a witness plate exposed to LESF and scanning electron microscopy observation of the electrodes revealed that the ceramic erosion ([Formula: see text] molecules per pulse) was predominant over electrodes erosion ([Formula: see text] atoms per pulse or [Formula: see text]).
{"title":"Long-Duration Test of Coaxial Low-Energy Surface Flashover Ignitor","authors":"Yunping Zhang, Lee Organski, A. Shashurin, K. Ostrikov","doi":"10.2514/1.b39071","DOIUrl":"https://doi.org/10.2514/1.b39071","url":null,"abstract":"A coaxial low-energy surface flashover (LESF) ignitor for CubeSat electric propulsion systems was developed and tested. The ignitor features a coaxial geometry with copper electrodes directly bonded to the inner and outer surfaces of the alumina ceramic tubular insulator. The ignitor proved to be operational throughout (and after) an extended duration test of 10 million pulses. Characterization of a single LESF event via intensified charge-coupled device fast photography showed that the initial plasma was generated along the insulator surface, while the later plasma production was governed by the column attached to the copper electrodes. The plasma plume propagated primarily perpendicular to the insulator surface at around [Formula: see text]. Further investigation on the erosion of ceramic insulator and copper electrodes via energy-dispersive x-ray spectroscopy analysis of a witness plate exposed to LESF and scanning electron microscopy observation of the electrodes revealed that the ceramic erosion ([Formula: see text] molecules per pulse) was predominant over electrodes erosion ([Formula: see text] atoms per pulse or [Formula: see text]).","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46529812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dominic Gallegos, Henry Pace, Charles Arnold, L. Massa, Greg Young
Introducing cavity flameholders into a solid-fuel ramjet fuel grain demonstrated increased fuel loading with sustained combustion in previously unfavorable geometries. Volumetric fuel loading improvements of up to 26% were demonstrated to sustain combustion. Regression patterns of cavity fuel grains are presented and show that the effect of implementing a cavity flameholder is to change the location of maximum regression and the reattachment point. The addition of a cavity flameholder does not appear to have a significant effect on combustion efficiency. However, it is noteworthy that longer cavities increased the chamber pressure above what was observed for a center-perforated fuel grains as a result of the increased mass addition and higher equivalence ratio associated with the higher regression rate. Large-eddy simulation computations were performed using a fourth-order discontinuous Galerkin finite element solver with a novel flamelet and progress variable formulation. The predictions agree well with the experiments and point to the increased heat transfer for longer cavities as the main flameholder mechanism. The larger heat feedback is supported by the formation of a stronger recirculation region, which leads to increased coherent fluctuations due to the transition between local and global instabilities.
{"title":"Regression and Flame Structure in Cavity Flameholding Solid-Fuel Ramjet Fuel Grains","authors":"Dominic Gallegos, Henry Pace, Charles Arnold, L. Massa, Greg Young","doi":"10.2514/1.b39139","DOIUrl":"https://doi.org/10.2514/1.b39139","url":null,"abstract":"Introducing cavity flameholders into a solid-fuel ramjet fuel grain demonstrated increased fuel loading with sustained combustion in previously unfavorable geometries. Volumetric fuel loading improvements of up to 26% were demonstrated to sustain combustion. Regression patterns of cavity fuel grains are presented and show that the effect of implementing a cavity flameholder is to change the location of maximum regression and the reattachment point. The addition of a cavity flameholder does not appear to have a significant effect on combustion efficiency. However, it is noteworthy that longer cavities increased the chamber pressure above what was observed for a center-perforated fuel grains as a result of the increased mass addition and higher equivalence ratio associated with the higher regression rate. Large-eddy simulation computations were performed using a fourth-order discontinuous Galerkin finite element solver with a novel flamelet and progress variable formulation. The predictions agree well with the experiments and point to the increased heat transfer for longer cavities as the main flameholder mechanism. The larger heat feedback is supported by the formation of a stronger recirculation region, which leads to increased coherent fluctuations due to the transition between local and global instabilities.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41865905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a method for evaluating the risk of autoignition for the canonical problem of an enclosed hydrogen jet in crossflow (JICF), which is highly relevant to the design of mixing ducts. The proposed method is based on the separation of the underlying mixing pattern from the evolution of the chemical reactions, whereas the effect of mixing is maintained on the latter with the purpose of creating a reliable yet computationally efficient design tool for hydrogen gas turbines. Two variants of the incompletely stirred reactor network (ISRN) approach are proposed that provide the evolution of preignition radicals and autoignition kernel location, leveraging a nonreacting computational fluid dynamics solution or an analytical mixing pattern. The ISRN governing equations include all the salient features of hydrogen transport and lead to a conservative estimate of autoignition risk. Application to a few model problems with varied operating conditions suggests that radical buildup in the JICF can lead to autoignition in the vicinity of a most reactive mixture fraction, which is consistent with other laminar or turbulent hydrogen flows. However, the radical formation and autoignition kernel location strongly depend on the prediction of the underlying mixing field and the amount of differential diffusion within the JICF, which here primarily favors lower values of the composite mixture fraction and the transport of hydrogen and radicals away from the jet trajectory.
{"title":"Low-Order Autoignition Modeling for Hydrogen Transverse Jets","authors":"S. Gkantonas, E. Mastorakos","doi":"10.2514/1.b39142","DOIUrl":"https://doi.org/10.2514/1.b39142","url":null,"abstract":"This paper presents a method for evaluating the risk of autoignition for the canonical problem of an enclosed hydrogen jet in crossflow (JICF), which is highly relevant to the design of mixing ducts. The proposed method is based on the separation of the underlying mixing pattern from the evolution of the chemical reactions, whereas the effect of mixing is maintained on the latter with the purpose of creating a reliable yet computationally efficient design tool for hydrogen gas turbines. Two variants of the incompletely stirred reactor network (ISRN) approach are proposed that provide the evolution of preignition radicals and autoignition kernel location, leveraging a nonreacting computational fluid dynamics solution or an analytical mixing pattern. The ISRN governing equations include all the salient features of hydrogen transport and lead to a conservative estimate of autoignition risk. Application to a few model problems with varied operating conditions suggests that radical buildup in the JICF can lead to autoignition in the vicinity of a most reactive mixture fraction, which is consistent with other laminar or turbulent hydrogen flows. However, the radical formation and autoignition kernel location strongly depend on the prediction of the underlying mixing field and the amount of differential diffusion within the JICF, which here primarily favors lower values of the composite mixture fraction and the transport of hydrogen and radicals away from the jet trajectory.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45467165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mark E. Noftz, Andrew J. Shuck, Joseph S. Jewell, Jonathan Poggie, Andrew N. Bustard, Thomas J. Juliano, Nicholas J. Bisek
The design of an inward-turning high-speed three-dimensional streamline-traced intake is presented from osculating axisymmetric theory. To satisfy the osculating intake design criteria, a stitched Busemann diffuser and internal conical flow-A solution are used as the basic isentropic compressive streamline. This new contour provides efficient compression, high flow uniformity, and straight leading-edge shocks of equal strength. Additionally, a novel method for constructing the inlet cowl is presented. The combined process leads to a new method of high-speed intake design. A generic shape-transitioned intake is constructed and named the Indiana inlet for the Indiana universities that contributed to the project. Computational fluid dynamic results are assessed to validate the design method for the two-dimensional parent flowfields and the full three-dimensional design.
{"title":"Design of an Internal Osculating Waverider Intake","authors":"Mark E. Noftz, Andrew J. Shuck, Joseph S. Jewell, Jonathan Poggie, Andrew N. Bustard, Thomas J. Juliano, Nicholas J. Bisek","doi":"10.2514/1.b38916","DOIUrl":"https://doi.org/10.2514/1.b38916","url":null,"abstract":"The design of an inward-turning high-speed three-dimensional streamline-traced intake is presented from osculating axisymmetric theory. To satisfy the osculating intake design criteria, a stitched Busemann diffuser and internal conical flow-A solution are used as the basic isentropic compressive streamline. This new contour provides efficient compression, high flow uniformity, and straight leading-edge shocks of equal strength. Additionally, a novel method for constructing the inlet cowl is presented. The combined process leads to a new method of high-speed intake design. A generic shape-transitioned intake is constructed and named the Indiana inlet for the Indiana universities that contributed to the project. Computational fluid dynamic results are assessed to validate the design method for the two-dimensional parent flowfields and the full three-dimensional design.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135399846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Filip Sazeček, Ondřej Vodochodský, R. Matyáš, Petr Stojan, J. Zigmund, J. Pachman
{"title":"Bicyclo-HMX as an Energetic Additive for Composite Propellants","authors":"Filip Sazeček, Ondřej Vodochodský, R. Matyáš, Petr Stojan, J. Zigmund, J. Pachman","doi":"10.2514/1.b38977","DOIUrl":"https://doi.org/10.2514/1.b38977","url":null,"abstract":"","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42038419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A flowpath geometry was computed that improves the specific impulse of a dual-mode scramjet engine in a generic X-51 hypersonic vehicle. Six parameters were varied: inlet contraction ratio, the diameters and numbers of fuel injectors, divergence angle of the combustor wall, nozzle flap deflection angle, and flight Mach number. The maximum specific impulse [Formula: see text] was 2296 s in the ram mode and 832 s in the scram mode. A reduced-order model simulates the finite-rate chemistry of JP-7 fuel and the unstart limits. Results show that both combustion efficiency and [Formula: see text] drop to unacceptably low levels when the finite-rate chemical reaction rates are weakened by flame strain-out due to the large air velocities, or when the flame becomes longer than the combustor. Small [Formula: see text] occurs when the following are too small: the inlet contraction ratio, the inlet compression ratio, the number of fuel injectors, and the diameter of fuel injectors. When these parameters are too large, excessive heat release causes unstart. The operating range was identified between these limits. For JP-7 fuel, it was found that the inlet should raise the pressure to above 5 atm. Results are explained by the interactions between reactions, mixing, and flame strain-out.
{"title":"Scramjet Engine Flowpath That Improves Specific Impulse Using JP-7 Fuel","authors":"Yunseok Choi, J. Driscoll","doi":"10.2514/1.b38931","DOIUrl":"https://doi.org/10.2514/1.b38931","url":null,"abstract":"A flowpath geometry was computed that improves the specific impulse of a dual-mode scramjet engine in a generic X-51 hypersonic vehicle. Six parameters were varied: inlet contraction ratio, the diameters and numbers of fuel injectors, divergence angle of the combustor wall, nozzle flap deflection angle, and flight Mach number. The maximum specific impulse [Formula: see text] was 2296 s in the ram mode and 832 s in the scram mode. A reduced-order model simulates the finite-rate chemistry of JP-7 fuel and the unstart limits. Results show that both combustion efficiency and [Formula: see text] drop to unacceptably low levels when the finite-rate chemical reaction rates are weakened by flame strain-out due to the large air velocities, or when the flame becomes longer than the combustor. Small [Formula: see text] occurs when the following are too small: the inlet contraction ratio, the inlet compression ratio, the number of fuel injectors, and the diameter of fuel injectors. When these parameters are too large, excessive heat release causes unstart. The operating range was identified between these limits. For JP-7 fuel, it was found that the inlet should raise the pressure to above 5 atm. Results are explained by the interactions between reactions, mixing, and flame strain-out.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44272316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liquid-fuel ramjets (LFRJs) exhibit high specific impulse (compared to rockets) due to ambient air intake for combustion and rely on storable liquid fuel at controllable mass flow rates. In this investigation, we perform a similarity analysis of an LFRJ combustor in order to determine parameters that can be applied to predict the behavior of an engine of any magnitude on the basis of test results obtained from engines of different scales. Similarity analysis accounting for geometry, transport phenomena, liquid-fuel dynamics, and chemistry is conducted. It defines a series of similarity rules resulting in pressure–diameter scaling. The scaling model was evaluated using Cantera chemical kinetics software and the Hybrid Chemistry Jet Propellant-8 liquid-fuel reaction mechanism, transport properties, and thermodynamic data. It simulates the combustion dynamics as those of a perfectly stirred reactor in order to determine the effects of the pressure and combustor size on combustion efficiency via the degree of reaction completion at various residence times. The simulation confirmed our scaling prediction that, for operating conditions where chemical kinetics are the main factor affecting combustion efficiency, we require pressures that are inversely proportional to the combustor dimensions.
{"title":"Similarity and Scaling in a Liquid-Fuel Ramjet Combustor","authors":"Elisabeth Riska, A. Gany","doi":"10.2514/1.b38934","DOIUrl":"https://doi.org/10.2514/1.b38934","url":null,"abstract":"Liquid-fuel ramjets (LFRJs) exhibit high specific impulse (compared to rockets) due to ambient air intake for combustion and rely on storable liquid fuel at controllable mass flow rates. In this investigation, we perform a similarity analysis of an LFRJ combustor in order to determine parameters that can be applied to predict the behavior of an engine of any magnitude on the basis of test results obtained from engines of different scales. Similarity analysis accounting for geometry, transport phenomena, liquid-fuel dynamics, and chemistry is conducted. It defines a series of similarity rules resulting in pressure–diameter scaling. The scaling model was evaluated using Cantera chemical kinetics software and the Hybrid Chemistry Jet Propellant-8 liquid-fuel reaction mechanism, transport properties, and thermodynamic data. It simulates the combustion dynamics as those of a perfectly stirred reactor in order to determine the effects of the pressure and combustor size on combustion efficiency via the degree of reaction completion at various residence times. The simulation confirmed our scaling prediction that, for operating conditions where chemical kinetics are the main factor affecting combustion efficiency, we require pressures that are inversely proportional to the combustor dimensions.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44144843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Flow–flame interactions were investigated in an optically accessible solid fuel ramjet combustor. Experiments were performed with a single hydroxyl-terminated polybutadiene fuel slab located downstream of a backward-facing step in a rectangular chamber. To emulate flight-relevant combustor conditions, unvitiated heated air was directed through the combustion chamber with an inlet temperature of [Formula: see text], chamber pressures of 450–690 kPa, and port Reynolds number of [Formula: see text]. To characterize the heat-release distribution and velocity field, 20 kHz [Formula: see text]-chemiluminescence and 10 kHz particle imaging velocimetry measurements were used. Comparison between the mean [Formula: see text] chemiluminescence images acquired at three flow conditions indicates reduction in flame height above the grain with increasing air mass flow rate. Dominant heat-release coherent structures in the statistically stationary flow are identified using the spectral proper orthogonal decomposition technique implemented on time series of instantaneous images. The spatial mode shapes of the chemiluminescence and velocity field measurements indicated that the flow–flame interactions were dominated by vortex shedding generated at the backward-facing step in the combustor, at Strouhal numbers of 0.06–0.10. The frequency corresponding to these modes is shown to be invariant of air mass flux, indicating that system dynamics are primarily dependent on the backward-facing step geometry and the bulk velocity in the combustor.
{"title":"Flame Dynamics in an Optically Accessible Solid Fuel Ramjet Combustor","authors":"Will C. Senior, Rohan M. Gejji, C. Slabaugh","doi":"10.2514/1.b39078","DOIUrl":"https://doi.org/10.2514/1.b39078","url":null,"abstract":"Flow–flame interactions were investigated in an optically accessible solid fuel ramjet combustor. Experiments were performed with a single hydroxyl-terminated polybutadiene fuel slab located downstream of a backward-facing step in a rectangular chamber. To emulate flight-relevant combustor conditions, unvitiated heated air was directed through the combustion chamber with an inlet temperature of [Formula: see text], chamber pressures of 450–690 kPa, and port Reynolds number of [Formula: see text]. To characterize the heat-release distribution and velocity field, 20 kHz [Formula: see text]-chemiluminescence and 10 kHz particle imaging velocimetry measurements were used. Comparison between the mean [Formula: see text] chemiluminescence images acquired at three flow conditions indicates reduction in flame height above the grain with increasing air mass flow rate. Dominant heat-release coherent structures in the statistically stationary flow are identified using the spectral proper orthogonal decomposition technique implemented on time series of instantaneous images. The spatial mode shapes of the chemiluminescence and velocity field measurements indicated that the flow–flame interactions were dominated by vortex shedding generated at the backward-facing step in the combustor, at Strouhal numbers of 0.06–0.10. The frequency corresponding to these modes is shown to be invariant of air mass flux, indicating that system dynamics are primarily dependent on the backward-facing step geometry and the bulk velocity in the combustor.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44075304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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