Effect of Dump Gap on Velocity Distribution and Flow Split in a Prototype Reverse-Flow Gas Turbine Combustor

Bharani, Sanjeev; Singh, Santokh; Agrawal, D. P.

doi:10.1515/tjj.1998.15.2.141

“…The presence of an imposed stream wise adverse pressure gradient promotes more rapid mixing and spreading of the shear layer in the initial mixing region, elevated turbulent normal stresses and shear stress levels in the outer portion of the mixing layer after the inner and annular streams have merged [9]. Bharani et al [5] have reviewed literature on experimental studies -both isothermal and combustion -and prediction studies on coaxial jets, transverse jets and realistic liner geometries. In respect of coaxial jets, though mostly on swirling flows, they have listed the findings with regard to development of flow.…”

Section: Introductionmentioning

confidence: 99%

Flow Development of Multi-Annular Jets in a Confinement: Effect of Expansion Ratio

Tarnacha,

Singh,

Rai

2023

joast

1

0

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Confined coaxial jets have been widely used in gas turbine combustors, where the requirement is to achieve better mixing between two streams - fuel and air - prior to ignition so as to provide stable and complete combustion. Two shear layers, one between the central jet and the annular jet and other between the annular jet and the stagnant fluid outside the annular jet help in the mixing process for confined coaxial jets. Therefore, for improved mixing, a configuration of one central jet and two co-annular jets, called multi-annular or multicoaxial jets, has been considered. To understand mixing of these streams in a confinement (mixing chamber), the mean axial velocity profiles at different axial locations of the mixing chamber and the static pressure along the wall of the mixing chamber are measured for expansion ratio of 1 and 1.3. These quantities are also computed using CFD software, FLUENT, with Standard k-ε turbulence model. After validation of the CFD code, parametric studies have been carried out for different expansion ratios. The results provide a good understanding of the mixing process and flow development in expanding confinement.

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“…The compact reaction zone causes the fuel evaporation distance to be shortened, which affects combustion efficiency and stability. The study of reverse-flow combustors has attracted the attention of many scholars [6][7][8][9][10][11][12][13][14]. For example, Bharani et al [9] showed that the flow characteristics and flow distribution of the jet holes of a reverse-flow combustor change when the flow characteristics of the outer annulus were altered.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Flow Characteristics of a Reverse-Flow Combustor

Hu

¹

,

Li

²

,

Wu

³

et al. 2022

International Journal of Aerospace Engineering

2

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Reverse-flow combustor is widely used for small engines to overcome high speed shaft whirling problem and to provide a low frontal area. An experimental investigation was carried out to research the flow field characteristics of a reverse-flow combustor in this paper. Different aerodynamic conditions were studied using PIV to reveal the characteristics of both the nonreacting and reacting flow fields. The structure of the nonreacting flow field in the central section shows similarity as the total pressure loss coefficient increases. The penetrating depth, jet angle, recirculation zone position, and the flow streamlines are similar, while the velocity value of the flow field increases. The structure of the reacting flow field on the central section is different from that of nonreacting flow field, but the variation trend of the reacting flow field under different pressure loss coefficient is similar to that of the nonreacting flow field. By examining the nonreacting and reacting flow fields under the same total pressure loss conditions, marked differences were observed in the primary zone close to the swirler outlet. The relative motion between fuel injection, airflow, and combustion affects the flow field in this zone. The velocity with combustion is faster than that of the nonreacting flow because of the increased temperature and heat release.

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“…In addition, the authors clarified the flow characteristics of the inlet airflow with different swirling intensities in the outer circular channel of the reserve-flow combustor. Lastly, they investigated the effects on jets from different jet holes [9,10]. Currently, on account of compact structures, researchers mainly adopt probes and numerical simulations to examine the flow field characteristics and combustion performance in the reverse-flow combustor.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on Flame Chemiluminescence and Flow Characteristics of a Reverse-Flow Combustor

Hu

¹

,

Li

²

,

Wu

³

et al. 2022

International Journal of Aerospace Engineering

0

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The reverse-flow combustor is extensively applied in small engines due to its compact structure. The cold-state flow characteristics, the ignition process, and flame chemiluminescence characteristics of the reserve-flow combustor were investigated experimentally. Using the particle imaging velocimeter, the cold-state time-averaged flow fields at three different total pressure loss coefficients ζ B are examined. The ignition processes of the combustor, as well as flame characteristics during stable combustion at different equivalent ratios φ , are analyzed based on flame chemiluminescence imaging when ζ B is 3%. As ζ B increases from 1% to 5%, the flow field of the combustor remains almost unchanged while the flow velocity increases. For ζ B =3%, the ignition time T drops from 26 ms to 16 ms with an increase of φ . In addition, the ignition performance is enhanced. Proportions of the T2 phase (quasi-stable phase) are 73%, 68%, and 66%, respectively, suggesting that the quasi-stable phase is the key to successful ignition. As φ increases, the flame becomes thinner and shorter. Furthermore, standard deviations of continuous image areas of CH ∗ and OH ∗ drop from 0.0143 and 0.0132 to 0.0115 and 0.0109, respectively, which indicates the enhancement of combustion stability. According to the brightness distributions of CH ∗ and OH ∗ along the axial direction of the combustor at different equivalent ratios, the production of OH ∗ is significantly affected by the temperature. It can be adopted as an important sign of heat release during combustion.

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Effect of Dump Gap on Velocity Distribution and Flow Split in a Prototype Reverse-Flow Gas Turbine Combustor

Cited by 4 publications

References 2 publications

Flow Development of Multi-Annular Jets in a Confinement: Effect of Expansion Ratio

Flow Development of Multi-Annular Jets in a Confinement: Effect of Expansion Ratio

Experimental Investigation on Flow Characteristics of a Reverse-Flow Combustor

Experimental Investigation on Flame Chemiluminescence and Flow Characteristics of a Reverse-Flow Combustor

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