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Upstream porthole injection in a 2-D scramjet model 总被引:1,自引:0,他引:1
Injection from portholes upstream of the combustion chamber was investigated as a method of delivering fuel into a scramjet.
This method reduces the viscous drag on a model by allowing a reduction in the length of the combustion chamber. At experimental
enthalpies of 3.0 MJ/kg in the T4 shock tunnel, there was no evidence of combustion in the intake, either by shadowgraph or
pressure measurements. Combustion was observed in the combustion chamber. A theoretical extension of these results is made
to a hot wall scenario.
Received 2 January 2001 / Accepted 3 August 2001 相似文献
3.
Mikaël Orain Frdric Grisch Eric Jourdanneau Bjorn Rossow Christian Guin Brigitte Trtout 《Comptes Rendus Mecanique》2009,337(6-7):373-384
Simultaneous measurements of PLIF-kerosene and PLIF-OH have been successfully performed in a multipoint injection system for various overall equivalence ratio, air inlet temperature between 480 and 730 K and pressure up to 2.2 MPa. Single shot 2D-maps of the spatial distribution of kerosene vapour and OH radical in the combustor have been recorded with good signal-to-noise ratio. Results show that depending on the split between the pilot and the main injectors, the flame front exhibits a single or a double structure. Good spatial correlation between the repartition of the kerosene vapour and the position of the flame front was observed; in particular, no “dark zone” is observed between the fuel and the flame front. As temperature and pressure increase, fuel evaporation improves and the spatial distribution of OH radical becomes more homogeneous in the combustor, suggesting a partially-distributed combustion. To cite this article: M. Orain et al., C. R. Mecanique 337 (2009). 相似文献
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In order to understand the effect of both the new homogeneous charge compression ignition (HCCI) combustion process and the use of biofuel, optical measurements were carried out into a transparent CR diesel engine. Rape seed methyl ester was used and tests with several injection pressures were performed. OH and HCO radical were detected and their evolutions were analyzed during the whole combustion. Moreover, soot concentration was measured by means the two colour pyrometry method. The reduction of particulate emission with biodiesel as compared to the diesel fuel was noted. Moreover, this effect resulted higher increasing the injection pressure. In the case of RME the oxidation of soot depends mainly from O2 content of fuel and OH is responsible of the NO formation in the chamber as it was observed for NOx exhaust emission. Moreover, it was investigated the evolution of HCO and CO into the cylinder. HCO was detected at the start of combustion. During the combustion, HCO oxidizes due to the increasing temperature and it produces CO. Both fuels have similar trend, the highest concentrations are detected for low injection pressure. This effect is more evident for the RME fuel. 相似文献
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Rajesh Sadanandan Peter Kutne Adam Steinberg Wolfgang Meier 《Flow, Turbulence and Combustion》2012,89(2):275-294
The effect of pressure on the characteristics of syngas flames is investigated under gas turbine relevant conditions using planar laser induced fluorescence of OH radicals and OH* chemiluminescence imaging. An optically accessible combustor fitted with a swirl burner was operated with two different syngas mixtures, preheated air at 700?K, and pressures ranging from 5 to 20?bars. The thermal load varied from 15 to 25?kW/bar at an equivalence ratios 0.5. The OH-PLIF measurements show that the flames under all conditions exhibited two reaction fronts, one at the shear layer between the inner recirculation zone and the fuel inlet, and one between the fuel inlet and the air nozzle. The more or less continuous reaction front at low pressure turned into a highly corrugated flame front at higher pressures, with isolated regions of ignition and extinction. The probability density distribution of the flame curvature for the mixtures studied showed that the inner and outer flame responded differently to the pressure increase, with the mean curvature magnitude also depending on the mixture composition and thermal load. The measurements clearly shows the limitations associated with the use of OH* chemiluminescence images as a marker for the heat release rate especially in case of syngas mixtures. 相似文献
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在JP10和煤油点火特性激波管实验的基础上,实验研究了硅烷对这两种典型高碳数碳氢燃
料点火特性的影响. 在预加热到70 C的激波管上,采用缝合运行条件获得了近7ms
的实验时间,将实验延伸至低温区. 采用气相色谱分析和高精度真空仪直接测定压力相结合
的方法,确定了燃料气相浓度,解决了高碳数碳氢燃料点火激波管实验时由于管壁吸附影响
燃料气相浓度确定的困难. 实验记录了点火过程中OH自由基发射强度变化,并作为判断点
火发生的标志. 实验温度范围880~1800K, 压力范
围0.16~0.53\,MPa. 当硅烷加入量约为燃料的10%~15%(摩尔比),
质量比为2%~3%, 观测到明显的点火促进作用. 该研究对超燃研究中发动机设计、
燃料选择等方面具有直接的工程意义,也可用于检验燃烧化学动力学模型的合理性. 相似文献
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An investigation of the leading edge characteristics in lifted turbulent methane-air (gaseous) and ethanol-air (spray) diffusion
flames is presented. Both combustion systems consist of a central nonpremixed fuel jet surrounded by low-speed air co-flow.
Non-intrusive laser-based diagnostic techniques have been applied to each system to provide information regarding the behavior
of the combustion structures and turbulent flow field in the regions of flame stabilization. Simultaneous sequential CH-PLIF/particle
image velocimetry and CH-PLIF/Rayleigh scattering measurements are presented for the lifted gaseous flame. The CH-PLIF data
for the lifted gas flame reveals the role that ``leading-edge' combustion plays as the stabilization mechanism in gaseous
diffusion flames. This phenomenon, characterized by a fuel-lean premixed flame branch protruding radially outward at the flame
base, permits partially premixed flame propagation against the incoming flow field. In contrast, the leading edge of the ethanol
spray flame, examined using single-shot OH-PLIF imaging and smoke-based flow visualization, does not exhibit the same variety
of leading-edge combustion structure, but instead develops a dual reaction zone structure as the liftoff height increases.
This dual structure is a result of the partial evaporation (hence partial premixing) of the polydisperse spray and the enhanced
rate of air entrainment with increased liftoff height (due to co-flow). The flame stabilizes in a region of the spray, near
the edge, occupied by small fuel droplets and characterized by intense mixing due to the presence of turbulent structures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Laser Doppler Anemometry (LDA) and Planar Laser-Induced Fluorescence (PLIF) measurements have been performed in a turbulent nonpremixed jet flame. One of the features of this configuration is a central co-axial fuel jet surrounded by a turbulent annular air flow. The whole is placed within a low-speed coflowing air stream. This three-flow system with turbulent primary air differs from flow systems used for nonpremixed jet flames reported in the literature and is very useful for obtaining information on the mixing process between fuel and primary air. Next to the characterization of the velocity field, special attention has been paid to the conditional seeding of the central fuel jet and of the annular air flow. Together with visualizations of the OH radical, an important combustion intermediate which is formed during combustion, and the NO radical, which is seeded to the central jet flow, the resulting statistics reveal the properties of small- and large-scale structures in the flame. 相似文献
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不同舱室结构内航空油料的燃爆参数存在差异,为了解和掌握不同结构舱室内航空油料的燃爆危害性,运用计算流体动力学(computational fluid dynamics,CFD)方法对不同结构航空油料舱室内的航空油料蒸汽燃爆问题进行了数值模拟。结果表明:密闭航空油料舱中的航空油料蒸汽预混燃爆时,油舱各处压力分布较均匀,无隔板密闭舱室和含不完全分割隔板密闭舱室内航空油料的最大燃爆压力分别为0.76、0.74 MPa,即舱室内的不完全分割隔板对航空油料燃爆时所产生的最大压力无显著影响;隔板等特殊结构的存在使舱室内部产生了气流漩涡,增大了燃料消耗的速率,导致火焰面传播速度及压力上升速率增大,舱室内各处燃料的质量分数由火焰面决定。 相似文献
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Simulations of an experimental hydrogen-fueled scramjet combustor are conducted using a novel dynamic hybrid Reynolds-averaged Navier-Stokes/large-eddy simulation (DHRL) modeling framework. The combustor has a Mach 2 core flow with a ramp fuel injector resulting in an equivalence ratio of 0.17. Three grid resolutions are obtained using local refinement by a factor of two in each direction in the fuel mixing and combustion region, and results from the three grids are used to understand the effect of grid refinement. Simulations reproduce temperature, pressure, velocity, and fuel concentrations in reasonable agreement with experimental measurements. Although heat release decreases on average, as the mesh is refined, peaks of heat release are intensified causing locally elevated temperatures. Spectral analysis of turbulence kinetic energy and heat release suggests stringent resolution requirements for reacting simulations capable of accurately resolving the effects of chemical reactions. Using the medium grid the DHRL model is compared to the improved delayed detached eddy simulation (IDDES) model and two Reynolds-averaged Navier-Stokes (RANS) models. Overall, the DHRL framework significantly outperforms other methods when compared to the experimental pressure rise. Additionally, spectral analysis suggests that the current framework is capable of accurately resolving turbulent structures at frequencies higher than IDDES. The study is the first documenting the use of DHRL for supersonic reacting flow and results suggest that it is a viable alternative to existing turbulence treatments for these types of flows. 相似文献
13.
The impending scarcity of fossil fuel in the future requires continued development in hydrocarbon combustion research. Biofuels
offer a promising alternative to traditional fossil fuel-based combustion. To optimize engine design for biofuels, adequate
combustion characteristics for new fuels have to be known. In this study, a new high pressure stainless steel shock tube for
measuring ignition delay times is presented. When compared with other shock tubes for investigating ignition delays, the new
tube provides superior maximum working pressures and geometric properties. Shock tube performance is determined by reference
experiments with air as driven gas. These experiments allow to determine the available test time and the influence of shock
attenuation. Owing to the large inner diameter of the shock tube, shock attenuation is <1% as it is typical for low pressure
shock tubes. However, contrast to typical low pressure shock tubes, non-diluted fuel–air mixtures at high pressures can be
investigated in the new shock tube due to the high allowable working pressure. First experiments concerning the ignition delay
time have been performed with methane and n-heptane. The results of these experiments show a good agreement to literature
data. As a first biofuel ethanol has been investigated at elevated pressures up to 40 bar. 相似文献
14.
Dynamic processes in gas turbine (GT) combustors play a key role in flame stabilization and extinction, combustion instabilities
and pollutant formation, and present a challenge for experimental as well as numerical investigations. These phenomena were
investigated in two gas turbine model combustors for premixed and partially premixed CH4/air swirl flames at atmospheric pressure. Optical access through large quartz windows enabled the application of laser Raman
scattering, planar laser-induced fluorescence (PLIF) of OH, particle image velocimetry (PIV) at repetition rates up to 10 kHz
and the simultaneous application of OH PLIF and PIV at a repetition rate of 5 kHz. Effects of unmixedness and reaction progress
in lean premixed GT flames were revealed and quantified by Raman scattering. In a thermo-acoustically unstable flame, the
cyclic variation in mixture fraction and its role for the feedback mechanism of the instability are addressed. In a partially
premixed oscillating swirl flame, the cyclic variations of the heat release and the flow field were characterized by chemiluminescence
imaging and PIV, respectively. Using phase-correlated Raman scattering measurements, significant phase-dependent variations
of the mixture fraction and fuel distributions were revealed. The flame structures and the shape of the reaction zones were
visualized by planar imaging of OH distribution. The simultaneous OH PLIF/PIV high-speed measurements revealed the time history
of the flow field–flame interaction and demonstrated the development of a local flame extinction event. Further, the influence
of a precessing vortex core on the flame topology and its dynamics is discussed. 相似文献
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双模态发动机的模态鉴别方法 总被引:1,自引:0,他引:1
双模态冲压发动机的不同燃烧模态具有不同的稳焰机制和流态特征,并且在模态转换时伴随着显著的推力变化. 因此,准确判断燃烧模态,对于捕捉发动机的燃烧区位置/范围、释热分布特征,以及为进一步优化燃烧室的设计(流道结构和供油布局) 具有重要意义. 目前尚无鉴别模态的有效试验方法,本文提出了一种模态鉴别的试验方法,并在超燃直连台上开展验证试验. 试验中使用的测量技术包括:壁面静压、高速阴影/纹影、多通道可调谐二极管吸收光谱和高能态碳氢自由基CH* 自发光成像. 利用多种测量方法的组合,可以同时获得燃烧室中气流静温、速度、马赫数分布,释热分布以及燃烧区位置/范围. 这些试验数据能够用于判别模态,并获得不同模态的流动和火焰特征. 相似文献
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Mixing processes between main flow and effusion cooling air are investigated in an effusion cooled, swirl-stabilized pressurized single sector gas turbine combustor using advanced laser diagnostics. Quantitative planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and planar laser-induced fluorescence of nitric oxide, seeded to the effusion cooling air, (NO-PLIF) are employed in the primary zone and close to the effusion cooled liner. This data is used to identify mixing events at three stages of premixed combustion, i.e. mixing before reaction, mixing during reaction and mixing after reaction. A parametric study of swirl and cooling air mass flow is conducted to investigate the mutual interaction between flame and cooling air. Within the primary zone, a significant radial asymmetry of OH concentration is observed. This asymmetry is partly explained by the presence of effusion cooling air within the unburned fresh gas, leading to lowered OH concentration within local reaction zones and their post-flame equilibrium concentration. Near the effusion cooled liner, adiabatic mixing after reaction is the dominant process across all investigated operating conditions. Notable mixing before reaction is only observed for the first effusion hole on the center line at low swirl conditions. 相似文献
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高马赫数超燃冲压发动机技术研究进展 总被引:1,自引:0,他引:1
吸气式高超声速飞行在空间运输和国家空天安全领域具有极高价值,超燃冲压发动机是其核心动力装置.目前飞行马赫数4.0~7.0超燃冲压发动机技术日趋成熟,发展更高速的飞行动力技术成为今后临近空间竞争焦点之一.本文对飞行马赫数8.0~10.0的高马赫数超燃冲压发动机技术进行了分析和综述.首先论述其亟待解决的关键问题和技术,分别包括高焓离解与热化学非平衡效应、超高速气流燃料增混与燃烧强化技术、高超声速燃烧与进气压缩的匹配及工作模态、高焓低雷诺数边界层流动及其控制方法、高焓低密度流动/燃烧的热防护技术,以及高马赫数发动机的地面试验风洞技术.然后,进一步介绍了国内外高焓激波风洞与驱动技术以及国内外典型的地面和飞行试验进展.进而针对推进和热防护的总体性能评估、高马赫数发动机内凸显的高焓离解与热化学非平衡效应、超高速气流燃料增混和燃烧强化技术综述了相关研究进展及结论,讨论了高马赫数超燃冲压发动机的可行性以及各关键技术的特点.最后进行了总结并对后续研究提出了几点建议. 相似文献
18.
A. F. Latypov 《Journal of Applied Mechanics and Technical Physics》2015,56(5):799-812
A functional mathematical model of a hydrogen-driven combustion chamber for a scramjet is described. The model is constructed with the use of one-dimensional steady gas-dynamic equations and parametrization of the channel configuration and the governing parameters (fuel injection into the flow, fuel burnout along the channel, dissipation of kinetic energy, removal of some part of energy generated by gases for modeling cooling of channel walls by the fuel) with allowance for real thermophysical properties of the gases. Through parametric calculations, it is found that fuel injection in three cross sections of the channel consisting of segments with weak and strong expansion ensures a supersonic velocity of combustion products in the range of free-stream Mach numbers M∞ = 6–12. It is demonstrated that the angle between the velocity vectors of the gaseous hydrogen flow and the main gas flow can be fairly large in the case of distributed injection of the fuel. This allows effective control of the mixing process. It is proposed to use the exergy of combustion products as a criterion of the efficiency of heat supply in the combustion chamber. Based on the calculated values of exergy, the critical free-stream Mach number that still allows scramjet operation is estimated. 相似文献
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R. Giezendanner-Thoben U. Meier W. Meier M. Aigner 《Flow, Turbulence and Combustion》2005,75(1-4):317-333
The phenomenon of periodic combustion instabilities has been investigated in a gas turbine model combustor by application
of two-line planar laser induced fluorescence (PLIF) of OH for the determination of temperature distributions. The measurement
technique has been evaluated using laser Raman scattering for comparison. The results showed that even with a lower accuracy
compared to single-point techniques like CARS or Raman, valuable information concerning the stabilization mechanism can be
drawn from the phase-locked mean temperature. The fact that the 2D technique is less time consuming compared to single-point
techniques makes it attractive for phase-resolved measurements. The investigation showed that the two-line OH-PLIF thermometry
technique can very well contribute to the understanding of combustion instabilities phenomena and assist the validation and
the improvement of CFD models. 相似文献
20.
Experimental investigation of combustion mechanisms of kerosene-fueled scramjet engines with double-cavity flameholders 总被引:2,自引:0,他引:2
Yu Pan Jian-Guo Tan Jian-Han Liang Wei-Dong Liu Zhen-Guo Wang 《Acta Mechanica Sinica》2011,27(6):891-897
A scramjet combustor with double cavitybased flameholders was experimentally studied in a directconnected test bed with the inflow conditions of M = 2.64,Pt = 1.84 MPa,Tt = 1 300 K.Successful ignition and selfsustained combustion with room temperature kerosene was achieved using pilot hydrogen,and kerosene was vertically injected into the combustor through 4×φ 0.5 mm holes mounted on the wall.For different equivalence ratios and different injection schemes with both tandem cavities and parallel cavities,flow fields were obtained and compared using a high speed camera and a Schlieren system.Results revealed that the combustor inside the flow field was greatly influenced by the cavity installation scheme,cavities in tandem easily to form a single side flame distribution,and cavities in parallel are more likely to form a joint flame,forming a choked combustion mode.The supersonic combustion flame was a kind of diffusion flame and there were two kinds of combustion modes.In the unchoked combustion mode,both subsonic and supersonic combustion regions existed.While in the choked mode,the combustion region was fully subsonic with strong shock propagating upstream.Results also showed that there was a balance point between the boundary separation and shock enhanced combustion,depending on the intensity of heat release. 相似文献