Anthony Desclaux, M. Orain, J. Garaud, V. Bodoc, P. Gajan
An experimental method based on chemiluminescent measurements is developed to determine the heat release rate produced by a two-phase flow kerosene/air flame. This quantity is known to be proportional to the air mass flow rate and the equivalence ratio. Experimental studies are carried out downstream of a liquid fuel injector used in aeronautical combustion chambers. The chemiluminescent spectra of the flame are analyzed for different air mass flow rates and equivalence ratios ranging from 0.4 to 0.71 in the steady-state flame configuration. The broadband background emission due to [Formula: see text] emission (where [Formula: see text] indicates an electronically excited specie) and soot radiation is first evaluated. Then, the analysis of the chemiluminescent emission from [Formula: see text], [Formula: see text], and [Formula: see text] indicates that the [Formula: see text] may be used to determine both the instantaneous equivalence ratio and the air mass flow rate. An example of the application of this method to measure fluctuations in the heat release rate induced by acoustic excitation of the flame is shown.
{"title":"Heat Release Rate from a Two-Phase Kerosene/Air Flame Using Chemiluminescence","authors":"Anthony Desclaux, M. Orain, J. Garaud, V. Bodoc, P. Gajan","doi":"10.2514/1.b38851","DOIUrl":"https://doi.org/10.2514/1.b38851","url":null,"abstract":"An experimental method based on chemiluminescent measurements is developed to determine the heat release rate produced by a two-phase flow kerosene/air flame. This quantity is known to be proportional to the air mass flow rate and the equivalence ratio. Experimental studies are carried out downstream of a liquid fuel injector used in aeronautical combustion chambers. The chemiluminescent spectra of the flame are analyzed for different air mass flow rates and equivalence ratios ranging from 0.4 to 0.71 in the steady-state flame configuration. The broadband background emission due to [Formula: see text] emission (where [Formula: see text] indicates an electronically excited specie) and soot radiation is first evaluated. Then, the analysis of the chemiluminescent emission from [Formula: see text], [Formula: see text], and [Formula: see text] indicates that the [Formula: see text] may be used to determine both the instantaneous equivalence ratio and the air mass flow rate. An example of the application of this method to measure fluctuations in the heat release rate induced by acoustic excitation of the flame is shown.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42729835","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 Lagrangian framework is proposed to address liquid film and atomization modeling in large-eddy simulations (LESs) of aeronautical air-blast injectors. The Lagrangian liquid film model of O’Rourke and Amsden (“A Spray/Wall Interaction Submodel for the KIVA-3 Wall Film Model,” SAE International TP 2000-01-0271, Warrendale, PA, 2000) is improved by introducing a subgrid contact angle to better predict the film height and the resulting film dynamics. Next, the phenomenological the primary atomization model for prefilming air-blast injectors (PAMELA) proposed by Chaussonnet et al. (“A New Phenomenological Model to Predict Drop Size Distribution in Large-Eddy Simulations of Airblast Atomizers,” International Journal of Multiphase Flow, Vol. 80, April 2016, pp. 29–42) for primary atomization at the prefilmer edge is enhanced to deal with complex geometries. This model is able to predict the droplet-size probability density function from the prefilmer height and flow conditions. The original formulation relied on correlations valid for flat plates to determine the gas boundary-layer thickness, and it required a gas velocity at film height to be set by the user. These two points make its use difficult for complex configurations where there is no simple correlation for the gas boundary-layer thickness and the gas velocity at film height cannot be a priori estimated. An embedded methodology, named the automatic PAMELA, is therefore proposed in this work to automatically determine these two quantities in the simulation. For each cell of the prefilmer edge where atomization occurs, the gas boundary-layer thickness is estimated by analyzing the local velocity profile thanks to Lagrangian probes; and the gas velocity is computed from the local film height by assuming a logarithmic velocity profile. Finally, the film and primary atomization models are coupled to a secondary atomization model, and they are assessed on an industrial air-blast aeronautical injector. The average droplet velocity profiles and Sauter mean diameters are compared against experimental phase Doppler particle analyzer measurements, and they demonstrate the ability of the proposed framework to perform Lagrangian LESs of liquid injection in complex geometries.
提出了一个拉格朗日框架来解决航空空气喷射器大涡模拟中的液膜和雾化建模问题。O 'Rourke和Amsden的拉格朗日液膜模型(“KIVA-3壁膜模型的喷雾/壁相互作用子模型”，SAE International TP 2000-01-0271，宾夕法尼亚州沃伦代尔，2000)通过引入子网格接触角来更好地预测膜高度和所产生的膜动力学，从而改进了拉格朗日液膜模型。接下来，Chaussonnet等人提出的预膜空气喷射器(PAMELA)的初级雾化模型(“预测大涡模拟空气喷射器滴度分布的新现象学模型”，《国际多相流杂志》，第80卷，2016年4月，第29-42页)在预膜器边缘的初级雾化得到增强，以处理复杂的几何形状。该模型能够根据预膜高度和流动条件预测液滴大小的概率密度函数。最初的公式依赖于对平板有效的相关性来确定气体边界层厚度，并且需要用户设置膜高度处的气体速度。这两点使得它很难用于复杂的结构，因为气体边界层厚度没有简单的相关性，而在膜高度处的气体速度不能先验地估计。因此，在这项工作中提出了一种嵌入式方法，称为自动PAMELA，以自动确定仿真中的这两个量。对于发生雾化的预膜边缘的每个单元，利用拉格朗日探针通过分析局部速度分布来估计气体边界层厚度;通过假设一个对数速度剖面，从局部膜高度计算气速。最后，将膜状雾化模型和一次雾化模型与二次雾化模型进行了耦合，并在一个工业鼓风航空喷油器上进行了评价。将平均液滴速度分布和Sauter平均直径与实验相位多普勒粒子分析仪的测量结果进行了比较，证明了所提出的框架在复杂几何形状下进行液体注入的拉格朗日LESs的能力。
{"title":"Lagrangian Simulation Methodology for Large-Eddy Simulations of Prefilming Air-Blast Injectors","authors":"Julien Carmona, N. Treleaven, N. Odier, B. Cuenot","doi":"10.2514/1.b39057","DOIUrl":"https://doi.org/10.2514/1.b39057","url":null,"abstract":"A Lagrangian framework is proposed to address liquid film and atomization modeling in large-eddy simulations (LESs) of aeronautical air-blast injectors. The Lagrangian liquid film model of O’Rourke and Amsden (“A Spray/Wall Interaction Submodel for the KIVA-3 Wall Film Model,” SAE International TP 2000-01-0271, Warrendale, PA, 2000) is improved by introducing a subgrid contact angle to better predict the film height and the resulting film dynamics. Next, the phenomenological the primary atomization model for prefilming air-blast injectors (PAMELA) proposed by Chaussonnet et al. (“A New Phenomenological Model to Predict Drop Size Distribution in Large-Eddy Simulations of Airblast Atomizers,” International Journal of Multiphase Flow, Vol. 80, April 2016, pp. 29–42) for primary atomization at the prefilmer edge is enhanced to deal with complex geometries. This model is able to predict the droplet-size probability density function from the prefilmer height and flow conditions. The original formulation relied on correlations valid for flat plates to determine the gas boundary-layer thickness, and it required a gas velocity at film height to be set by the user. These two points make its use difficult for complex configurations where there is no simple correlation for the gas boundary-layer thickness and the gas velocity at film height cannot be a priori estimated. An embedded methodology, named the automatic PAMELA, is therefore proposed in this work to automatically determine these two quantities in the simulation. For each cell of the prefilmer edge where atomization occurs, the gas boundary-layer thickness is estimated by analyzing the local velocity profile thanks to Lagrangian probes; and the gas velocity is computed from the local film height by assuming a logarithmic velocity profile. Finally, the film and primary atomization models are coupled to a secondary atomization model, and they are assessed on an industrial air-blast aeronautical injector. The average droplet velocity profiles and Sauter mean diameters are compared against experimental phase Doppler particle analyzer measurements, and they demonstrate the ability of the proposed framework to perform Lagrangian LESs of liquid injection in complex geometries.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46240830","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}
Controlling rocket thrust may be done via propellant burning rate catalysts and enhancers. This paper presents an experimental investigation on increasing the thrust of hybrid and solid motors by adding a small fraction of expandable graphite (EG) within the binder matrix to enhance burning rate. EG is a form of intercalated graphite flakes that upon heating change their appearance to elongated fibers/strings of substantially larger length and volume. The elongated EG strings at the burning surface are hypothesized to conduct heat from the hot surroundings to the bulk, thereby increasing the burning rate. High-speed photography of the surface phenomena of fuel slabs containing EG additive subjected to flame supports the greater effect on burning rate enhancement (up to twofold) for polyester versus hydroxyl-terminated polybutadiene or paraffin wax fuels in hybrid motors. Similar investigation on the burning of ammonium perchlorate–polymer solid propellant strands revealed different surface phenomena and substantial burning rate increase (60% and more) for hydroxyl-terminated polybutadiene versus polyester binder with 5% EG additive. It can be concluded that EG can serve as a novel burning rate and thrust enhancer without deterioration of the mechanical properties of the polymeric fuel/binder for hybrid (including solid fuel ramjet) and solid propellant motors.
{"title":"Increasing Burning Rate and Motor Thrust by Expandable Graphite Additives","authors":"Gabriele T. Muller, A. Gany","doi":"10.2514/1.b39126","DOIUrl":"https://doi.org/10.2514/1.b39126","url":null,"abstract":"Controlling rocket thrust may be done via propellant burning rate catalysts and enhancers. This paper presents an experimental investigation on increasing the thrust of hybrid and solid motors by adding a small fraction of expandable graphite (EG) within the binder matrix to enhance burning rate. EG is a form of intercalated graphite flakes that upon heating change their appearance to elongated fibers/strings of substantially larger length and volume. The elongated EG strings at the burning surface are hypothesized to conduct heat from the hot surroundings to the bulk, thereby increasing the burning rate. High-speed photography of the surface phenomena of fuel slabs containing EG additive subjected to flame supports the greater effect on burning rate enhancement (up to twofold) for polyester versus hydroxyl-terminated polybutadiene or paraffin wax fuels in hybrid motors. Similar investigation on the burning of ammonium perchlorate–polymer solid propellant strands revealed different surface phenomena and substantial burning rate increase (60% and more) for hydroxyl-terminated polybutadiene versus polyester binder with 5% EG additive. It can be concluded that EG can serve as a novel burning rate and thrust enhancer without deterioration of the mechanical properties of the polymeric fuel/binder for hybrid (including solid fuel ramjet) and solid propellant motors.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44129222","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}
Paulo G. C. Martins, Kesiany M. de Souza, Rene F. Boschi, Leonardo H. Gouvêa, C. Martins
This paper discusses the performance characteristics of a paraffin-based blend of liquid ethanol with paraffin as compared to pure paraffin in a hybrid rocket motor. Since the disclosure of the high regression rates of liquefying fuels as compared to classic fuels such as hydroxyl-terminated polybutadiene (HTPB), many studies using paraffin have been reported in the literature. Although pure paraffin regresses three to four times faster than HTPB, it is not an ideal fuel for launcher applications for the following reasons: it does not provide the optimum mechanical strength, it may suffer from combustion instability, and it offers low combustion efficiency. The proposed blend is biphasic, with drops of liquid ethanol trapped in a paraffin binder; and a nonionic surfactant was employed to emulsify the ethanol into paraffin wax. The results indicated that at a mean prefiring [Formula: see text] of 0.6 and a [Formula: see text] of 60, both the P95E05 and P90E10 fuels demonstrated no significant statistical difference compared to pure paraffin in terms of thrust, specific impulse, fuel mass flow rate, characteristic velocity, and combustion efficiency. However, the P95E05 and P90E10 fuels did show damping in the pressure oscillations relative to paraffin, indicating a reduction in the low-frequency combustion instability observed in the ballistic responses of paraffin.
{"title":"Performance Comparison of Paraffin/Ethanol Fuel Blends in a Laboratory-Scale Hybrid Rocket Motor","authors":"Paulo G. C. Martins, Kesiany M. de Souza, Rene F. Boschi, Leonardo H. Gouvêa, C. Martins","doi":"10.2514/1.b39051","DOIUrl":"https://doi.org/10.2514/1.b39051","url":null,"abstract":"This paper discusses the performance characteristics of a paraffin-based blend of liquid ethanol with paraffin as compared to pure paraffin in a hybrid rocket motor. Since the disclosure of the high regression rates of liquefying fuels as compared to classic fuels such as hydroxyl-terminated polybutadiene (HTPB), many studies using paraffin have been reported in the literature. Although pure paraffin regresses three to four times faster than HTPB, it is not an ideal fuel for launcher applications for the following reasons: it does not provide the optimum mechanical strength, it may suffer from combustion instability, and it offers low combustion efficiency. The proposed blend is biphasic, with drops of liquid ethanol trapped in a paraffin binder; and a nonionic surfactant was employed to emulsify the ethanol into paraffin wax. The results indicated that at a mean prefiring [Formula: see text] of 0.6 and a [Formula: see text] of 60, both the P95E05 and P90E10 fuels demonstrated no significant statistical difference compared to pure paraffin in terms of thrust, specific impulse, fuel mass flow rate, characteristic velocity, and combustion efficiency. However, the P95E05 and P90E10 fuels did show damping in the pressure oscillations relative to paraffin, indicating a reduction in the low-frequency combustion instability observed in the ballistic responses of paraffin.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41635911","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}
Yunzhen Zhang, John Z. G. Ma, Kevin Wu, Miao Cheng, Zhaohua Sheng, Guangyao Rong, D. Shen, Jian-ping Wang, Shu-jie Zhang
In the present study, an experimental performance analysis of hollow rotating detonation engines (RDEs) with Laval nozzles is carried out for the first time. Experiments of a hollow rotating detonation engine with a Laval nozzle were performed with a modular RDE at a backpressure condition of 1 atm. Two configurations with area ratios of the outlet throat to the inlet of [Formula: see text] and 2.7 have been tested with gaseous methane/oxygen as propellants. Three normalized metrics, usually used for evaluating the performance of conventional rocket engines, are introduced to analyze the performance deficit between the measured value of an RDE and the ideal value of an isobaric-combustion-based engine. These metrics allow for assessing the entire engine and each component separately. The metric analysis suggests a small outlet-to-inlet area ratio ([Formula: see text]) is detrimental to the propulsive performance. To explain the mechanism, a gas-stratification flowfield model is further proposed. It is found that the unchoked region in the combustible gas layer, which is caused by unchoked injection on the injecting plate, is responsible for the performance deficit of the combustion chamber. This model is then validated by one-dimensional numerical simulations and experimental data. In addition, we also focus on the global performance, including the gross thrust, the specific impulse, and the utilization of the supplied stagnation pressure. The result implies a tradeoff space when choosing an appropriate [Formula: see text].
{"title":"Analysis on Propulsive Performance of Hollow Rotating Detonation Engine with Laval Nozzle","authors":"Yunzhen Zhang, John Z. G. Ma, Kevin Wu, Miao Cheng, Zhaohua Sheng, Guangyao Rong, D. Shen, Jian-ping Wang, Shu-jie Zhang","doi":"10.2514/1.b38830","DOIUrl":"https://doi.org/10.2514/1.b38830","url":null,"abstract":"In the present study, an experimental performance analysis of hollow rotating detonation engines (RDEs) with Laval nozzles is carried out for the first time. Experiments of a hollow rotating detonation engine with a Laval nozzle were performed with a modular RDE at a backpressure condition of 1 atm. Two configurations with area ratios of the outlet throat to the inlet of [Formula: see text] and 2.7 have been tested with gaseous methane/oxygen as propellants. Three normalized metrics, usually used for evaluating the performance of conventional rocket engines, are introduced to analyze the performance deficit between the measured value of an RDE and the ideal value of an isobaric-combustion-based engine. These metrics allow for assessing the entire engine and each component separately. The metric analysis suggests a small outlet-to-inlet area ratio ([Formula: see text]) is detrimental to the propulsive performance. To explain the mechanism, a gas-stratification flowfield model is further proposed. It is found that the unchoked region in the combustible gas layer, which is caused by unchoked injection on the injecting plate, is responsible for the performance deficit of the combustion chamber. This model is then validated by one-dimensional numerical simulations and experimental data. In addition, we also focus on the global performance, including the gross thrust, the specific impulse, and the utilization of the supplied stagnation pressure. The result implies a tradeoff space when choosing an appropriate [Formula: see text].","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49018101","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}
An optimized engine start procedure is critical to the successful operation of a liquid rocket engine in launch vehicles. A solid propellant gas generator is widely adopted for the turbine starter during engine startup, and ammonium nitrate and ammonium perchlorate propellants are conventionally used for this purpose. However, these propellants have shortcomings such as high flame temperature, corrosive combustion residues, and low ignitability. In this study, a dihydroxyglyoxime (DHG)-based propellant was applied to turbine starters. The burning rate, characteristic velocity, and combustion temperature of the DHG propellant were evaluated using motor tests. The DHG-based propellant burned 3–11% slower in motor firing tests than that in strand burner tests, and an inversely proportional relationship was observed between the strand burn rate and the burning rate factor (ratio between motor burning rate measurement and strand burner prediction). The temperature sensitivity of the burning rate factor was found to be 0.23–0.24%/°C, and the pressure sensitivity of the characteristic velocity was 0.48–0.50%/MPa. These burning characteristics of the DHG-based propellant from static evaluations provide the evolution of the chamber pressure and the mass flow rate versus the time of the motor using internal ballistic analysis.
{"title":"Prediction of Burning Characteristics of Dihydroxyglyoxime Composite Propellant","authors":"Jesun Jang, Sejin Kwon","doi":"10.2514/1.b38882","DOIUrl":"https://doi.org/10.2514/1.b38882","url":null,"abstract":"An optimized engine start procedure is critical to the successful operation of a liquid rocket engine in launch vehicles. A solid propellant gas generator is widely adopted for the turbine starter during engine startup, and ammonium nitrate and ammonium perchlorate propellants are conventionally used for this purpose. However, these propellants have shortcomings such as high flame temperature, corrosive combustion residues, and low ignitability. In this study, a dihydroxyglyoxime (DHG)-based propellant was applied to turbine starters. The burning rate, characteristic velocity, and combustion temperature of the DHG propellant were evaluated using motor tests. The DHG-based propellant burned 3–11% slower in motor firing tests than that in strand burner tests, and an inversely proportional relationship was observed between the strand burn rate and the burning rate factor (ratio between motor burning rate measurement and strand burner prediction). The temperature sensitivity of the burning rate factor was found to be 0.23–0.24%/°C, and the pressure sensitivity of the characteristic velocity was 0.48–0.50%/MPa. These burning characteristics of the DHG-based propellant from static evaluations provide the evolution of the chamber pressure and the mass flow rate versus the time of the motor using internal ballistic analysis.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46578831","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}
The competing flames model, also termed the Beckstead–Derr–Price model, for steady-state heterogeneous propellant combustion has been widely used but has not been sufficiently updated in decades or compared to modern propellant combustion databases. In the current study, historical competing flames modeling approaches were thoroughly documented; and an improved framework was outlined and updated to include several improvements, such as variable flame temperatures, specific heat capacities, and latent heat terms. Model parameters were initially taken from previous literature, but the fuel and diffusion flame parameters were optimized based on a compiled database of unimodal propellant burning rates from the literature spanning a wide range of ammonium perchlorate (AP) particle sizes ([Formula: see text]), AP mass concentrations (70–87.5%), and combustion pressures (0.7–20.7 MPa). The improved model was compared to AP monopropellant, unimodal, and multimodal propellant burning rate databases from the literature. General dependencies of the burning rate-to-oxidizer concentration and size were accurately captured. The predictive capability of the improved model for AP monopropellant burning rates and unimodal propellant formulations was excellent, where the only significant discrepancies were noted for very fine AP particles ([Formula: see text]). Model predictions for multimodal formulations were moderate and could be improved by alternative pseudopropellant apportionment and statistical accounting schemes.
{"title":"Modern Competing Flames Model for Composite Ammonium Perchlorate/Hydroxyl-Terminated Polybutadiene Propellant Combustion","authors":"James C. Thomas, E. Petersen","doi":"10.2514/1.b38925","DOIUrl":"https://doi.org/10.2514/1.b38925","url":null,"abstract":"The competing flames model, also termed the Beckstead–Derr–Price model, for steady-state heterogeneous propellant combustion has been widely used but has not been sufficiently updated in decades or compared to modern propellant combustion databases. In the current study, historical competing flames modeling approaches were thoroughly documented; and an improved framework was outlined and updated to include several improvements, such as variable flame temperatures, specific heat capacities, and latent heat terms. Model parameters were initially taken from previous literature, but the fuel and diffusion flame parameters were optimized based on a compiled database of unimodal propellant burning rates from the literature spanning a wide range of ammonium perchlorate (AP) particle sizes ([Formula: see text]), AP mass concentrations (70–87.5%), and combustion pressures (0.7–20.7 MPa). The improved model was compared to AP monopropellant, unimodal, and multimodal propellant burning rate databases from the literature. General dependencies of the burning rate-to-oxidizer concentration and size were accurately captured. The predictive capability of the improved model for AP monopropellant burning rates and unimodal propellant formulations was excellent, where the only significant discrepancies were noted for very fine AP particles ([Formula: see text]). Model predictions for multimodal formulations were moderate and could be improved by alternative pseudopropellant apportionment and statistical accounting schemes.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49523384","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}
Louis M. Edelman, M. Gamba, Robin L. Hunt, A. Auslender
A highly confined shock train is investigated in a direct-connect isolator facility with a Mach 2 inflow and a constant-area low-aspect-ratio rectangular test section. High-speed schlieren imaging, wall static pressure measurements, surface oil-flow visualization, and particle image velocimetry from this isolator are synthesized into a three-dimensional schematic of the shock train structure. Against this, the prevailing pseudoshock models in the literature are assessed to evaluate the validity of their underlying assumptions. None of the prevailing pseudoshock models are found to simultaneously model the pressure and Mach number profiles, indicating a gap in the model formation and underlying assumptions when applied to the experimental isolator of interest. The presence of distortion in the isolator flowfield, such as a wall-bounded vortex, is found to skew the structure of the shock train, altering the strength and distribution of the compressive pressure gradient. It is further observed that the separated flow morphology surrounding the shock train is not monolithic, as is typically assumed, adjusting the balance of compressive forces within the shock cells. These findings lead to the conclusion that existing flux-conserved modeling approaches require modification to be effective in distorted and highly confined cases, including closure models that capture the three-dimensional distorted structure of the approach flow and its evolution along the shock train.
{"title":"Assessment of Pseudoshock Models Against Experiment in a Low-Aspect-Ratio Isolator","authors":"Louis M. Edelman, M. Gamba, Robin L. Hunt, A. Auslender","doi":"10.2514/1.b38913","DOIUrl":"https://doi.org/10.2514/1.b38913","url":null,"abstract":"A highly confined shock train is investigated in a direct-connect isolator facility with a Mach 2 inflow and a constant-area low-aspect-ratio rectangular test section. High-speed schlieren imaging, wall static pressure measurements, surface oil-flow visualization, and particle image velocimetry from this isolator are synthesized into a three-dimensional schematic of the shock train structure. Against this, the prevailing pseudoshock models in the literature are assessed to evaluate the validity of their underlying assumptions. None of the prevailing pseudoshock models are found to simultaneously model the pressure and Mach number profiles, indicating a gap in the model formation and underlying assumptions when applied to the experimental isolator of interest. The presence of distortion in the isolator flowfield, such as a wall-bounded vortex, is found to skew the structure of the shock train, altering the strength and distribution of the compressive pressure gradient. It is further observed that the separated flow morphology surrounding the shock train is not monolithic, as is typically assumed, adjusting the balance of compressive forces within the shock cells. These findings lead to the conclusion that existing flux-conserved modeling approaches require modification to be effective in distorted and highly confined cases, including closure models that capture the three-dimensional distorted structure of the approach flow and its evolution along the shock train.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44522288","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}
N. Yamamoto, Naoya Kuwabara, D. Kuwahara, Shinatora Cho, Y. Kosuga, Guilhem Dif Pradalier
To understand anomalous electron transport in a Hall thruster, plasma turbulence inside the acceleration channel was observed using a 76 GHz microwave interferometer. The dependence of the amplitude of the 100–500 kHz turbulence on magnetic flux density, and the relationships between the turbulence and other plasma instabilities and between the turbulence and the discharge current were investigated through spectral density and bicoherence analysis. The amplitude of electron number density fluctuations of the turbulence, integrating the spectral density from 100 to 500 kHz, is [Formula: see text], or almost 10% of the time-averaged electron number density. The amplitude of the turbulence decreases with increase in weak magnetic field strength (coil current less than 0.6 A) and then increases with increase in magnetic field strength. The amplitude of the turbulence has a positive relation to the discharge current, leads to anomalous electron transport inside the acceleration channel, and is coupled with ionization instability. In addition, low-frequency perturbations of several hundred hertz were observed, with a positive relation to the turbulence and coupled with both ionization instability and turbulence.
{"title":"Observation of Plasma Turbulence in a Hall Thruster Using Microwave Interferometry","authors":"N. Yamamoto, Naoya Kuwabara, D. Kuwahara, Shinatora Cho, Y. Kosuga, Guilhem Dif Pradalier","doi":"10.2514/1.b38711","DOIUrl":"https://doi.org/10.2514/1.b38711","url":null,"abstract":"To understand anomalous electron transport in a Hall thruster, plasma turbulence inside the acceleration channel was observed using a 76 GHz microwave interferometer. The dependence of the amplitude of the 100–500 kHz turbulence on magnetic flux density, and the relationships between the turbulence and other plasma instabilities and between the turbulence and the discharge current were investigated through spectral density and bicoherence analysis. The amplitude of electron number density fluctuations of the turbulence, integrating the spectral density from 100 to 500 kHz, is [Formula: see text], or almost 10% of the time-averaged electron number density. The amplitude of the turbulence decreases with increase in weak magnetic field strength (coil current less than 0.6 A) and then increases with increase in magnetic field strength. The amplitude of the turbulence has a positive relation to the discharge current, leads to anomalous electron transport inside the acceleration channel, and is coupled with ionization instability. In addition, low-frequency perturbations of several hundred hertz were observed, with a positive relation to the turbulence and coupled with both ionization instability and turbulence.","PeriodicalId":16903,"journal":{"name":"Journal of Propulsion and Power","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47766074","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}
In the present work, we discuss the employment of a computational fluid dynamics approach to evaluate the specific impulse of solid rocket motors. Particular care is focused on two-phase flow and divergence losses, which represent the most important contributions to the overall nozzle performance loss. A comprehensive parametric study is performed on the Zefiro 9A nozzle with the aim to evaluate the detrimental influence of relevant key features, such as alumina particle dimension, polydispersion, crystallization, and motor operating conditions. The capability of the present model to represent, with good accuracy, the overall performance of solid rocket motors is demonstrated by comparing the experimental specific impulse of several motors with numerical predictions.
{"title":"Multiphase Effects on Solid Rocket Nozzle Performance","authors":"M. Grossi, Alessio Sereno, D. Bianchi, B. Favini","doi":"10.2514/1.b39096","DOIUrl":"https://doi.org/10.2514/1.b39096","url":null,"abstract":"In the present work, we discuss the employment of a computational fluid dynamics approach to evaluate the specific impulse of solid rocket motors. Particular care is focused on two-phase flow and divergence losses, which represent the most important contributions to the overall nozzle performance loss. A comprehensive parametric study is performed on the Zefiro 9A nozzle with the aim to evaluate the detrimental influence of relevant key features, such as alumina particle dimension, polydispersion, crystallization, and motor operating conditions. The capability of the present model to represent, with good accuracy, the overall performance of solid rocket motors is demonstrated by comparing the experimental specific impulse of several motors with numerical predictions.","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":"47421267","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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