Measurements on flame structure of bluff body and swirl stabilized premixed flames close to blow-off

Zhang, Weijie; Wang, Jinhua; Lin, Wenjun; Guo, Shenyang; Zhang, Meng; Li, Guohua; Ye, Jingfeng; Huang, Zuohua

doi:10.1016/j.expthermflusci.2019.02.010

Cited by 59 publications

(17 citation statements)

References 37 publications

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“…In addition, with the development of optical technology, laser diagnosis is widely used in the measurement of specie concentration, flame temperature and flame flow field in the combustion process. The planar laser induced fluorescence technology (PLIF) is often used in the combustion diagnosis of laminar and turbulent flames, and has a good reliability [13]. For the solid phase combustion, Vilmart et al [14] and Parr and Hanson-Parr [15] used Fe-PLIF and NO-PLIF to measure the combustion intermediate products of propellants and explosives, respectively, which assists the understanding of the chemical reaction process of energetic materials.…”

Section: Introductionmentioning

confidence: 99%

The Influence of AP Addition on the Combustion Characteristics of TKX‐50 with Concentrated Ignition

Yan

Cao

Tao

et al. 2022

Propellants Explo Pyrotec

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In order to study the influence of ammonium perchlorate (AP) addition on the combustion reaction process of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50), a concentrated ignition system was used to evaluate the ignition and combustion characteristics of the samples. The self-luminescence characteristics and the OH concentration distribution in the flame of TKX-50 and TKX-50/AP composites were captured by a high-speed camera and a planar laser induced fluorescence system (PLIF), respectively. The combustion products were then analyzed by a scanning electron microscope (SEM) and a X-ray energy dispersive spectrometer (EDS). The results show that the reaction of TKX-50 undergoes three stages with concentrated ignition, and a bright yellow color appears in the flame due to the formation of NH 2 α during the combustion process. When the materials of AP is added, there are preignition occurred for twice. The ignition delay time increases, and the reaction in the pyrolysis phase is more intense. Besides, the burning rate is faster and the flame brightness is significantly weakened due to the decrease of NH 2 α. During the combustion process, the high-concentration OH signal of the two samples distribute on the two wings of the flames, and the peak signals are similar under the 10 Hz laser excitation. For the samples before and after the combustion reaction, the morphology is quite different, and the specific residue composition needs be further analyzed.

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Section: Introductionmentioning

confidence: 99%

The Influence of AP Addition on the Combustion Characteristics of TKX‐50 with Concentrated Ignition

Yan

Cao

Tao

et al. 2022

Propellants Explo Pyrotec

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“…For flame stabilization provided by recirculation zones, various structures including cavities, , steps, , and bluff-bodies have served as a classic design , in the context of premixed − and partially premixed combustion , applications. The flame stabilizing principle of the bluff-body is to generate recirculation flow inside the wake zones to extend the residence time of reactants and achieve a stabilized flame .…”

Section: Introductionmentioning

confidence: 99%

Partially Premixed Ignition for a Bluff-Body Flameholder under Various Igniter and Inlet Conditions

Zhang

2021

ACS Omega

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This study applies experimental methods to investigate the partially premixed ignition characteristics of a bluff-body flameholder with a pilot stage. The ignition fuel–air ratio (FAR) under different igniter and inlet conditions is obtained, while the ignition process is recorded with a high-speed photography device. Numerical simulations are carried out to investigate the relationship between the flow field, fuel distribution, and ignition process. The results show that a higher total capacitance energy storage of the igniter, inlet Mach number, or total pressure inside the combustion chamber will help increase the ignition performance, accelerate the development of the flame, and shorten the ignition delay. The flame propagation routine of the flameholder is controlled by several pairs of symmetrical recirculation zones behind the flameholder structure and the specific uneven fuel distribution caused by the flow field. This study provides a detailed understanding of the ignition process for the bluff-body flameholder.

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“…As the incoming fuel-air mixture becomes leaner, δ=15%, stratified flames alter from a tulip shape to a more cylindrical shape and start the trailing edge starts to retreat to the recirculation zone, δ=5%. Just prior to extinction (δ=1%), the lift off height increases and flame forms a an inversely conical or spear shape [221].…”

Section: Chemiluminescence Imagingmentioning

confidence: 99%

“…Subsequently, in Figure 7-21, the OH* chemiluminescent signal intensities for δ=5% are presented for RIM2 baffle width cases. From the depicted measurements, it is apparent that combustion occurs mainly at the downstream shear layer zone, triggering the penetration of unburned reactants at the region close to the stagnation point, causing a gradual cooling, which quenches locally the flame kernel, until extinction [209,221].…”

Section: Chemiluminescence Imagingmentioning

confidence: 99%

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

Paterakis¹,

Πατεράκης²

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The current work describes an experimental investigation of isothermal and turbulent reacting flow field characteristics downstream of axisymmetric bluff body stabilizers under a variety of inlet mixture conditions. Fully premixed and stratified flames established downstream of this double cavity premixer/burner configuration were measured and assessed under lean and ultra-lean operating conditions. The aim of this thesis was to further comprehend the impact of stratifying the inlet fuelair mixture on the reacting wake characteristics for a range of practical stabilizers under a variety of inlet fuel-air settings. In the first part of this thesis, the isothermal mean and turbulent flow features downstream of a variety of axisymmetric baffles was initially examined. The effect of different shapes, (cone or disk), blockage ratios, (0.23 and 0.48), and rim thicknesses of these baffles was assessed. The variations of the recirculation zones, back flow velocity magnitude, annular jet ejection angles, wake development, entrainment efficiency, as well as several turbulent flow features were obtained, evaluated and appraised. Next, a comparative examination of the counterpart turbulent cold fuel-air mixing performance and characteristics of stratified against fully-premixed operation was performed for a wide range of baffle geometries and inlet mixture conditions. Scalar mixing and entrainment properties were investigated at the exit plane, at the bluff body annular shear layer, at the reattachment region and along the developing wake were investigated. These isothermal studies provided the necessary background information for clarifying the combustion properties and interpreting the trends in the counterpart turbulent reacting fields. Subsequently, for selected bluff bodies, flame structures and behavior for operation with a variety of reacting conditions were demonstrated. The effect of inlet fuel-air mixture settings, fuel type and bluff body geometry on wake development, flame shape, anchoring and structure, temperatures and combustion efficiencies, over lean and close to blow-off conditions, was presented and analyzed. For the obtained measurements infrared radiation, particle image velocimetry, laser doppler velocimetry, chemiluminescence imaging set-ups, together with Fouriertransform infrared spectroscopy, thermocouples and global emission analyzer instrumentation was employed. This helped to delineate a number of factors that affectcold flow fuel-air mixing, flame anchoring topologies, wake structure development and overall burner performance. The presented data will also significantly assist the validation of computational methodologies for combusting flows and the development of turbulence-chemistry interaction models.

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Measurements on flame structure of bluff body and swirl stabilized premixed flames close to blow-off

Cited by 59 publications

References 37 publications

The Influence of AP Addition on the Combustion Characteristics of TKX‐50 with Concentrated Ignition

The Influence of AP Addition on the Combustion Characteristics of TKX‐50 with Concentrated Ignition

Partially Premixed Ignition for a Bluff-Body Flameholder under Various Igniter and Inlet Conditions

Experimental investigation of isothermal and reacting flow characteristics downstream of axisymmetric bluff body stabilizers under stratified or fully premixed inlet mixture conditions

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