Effects of Recess Length on Discharge Coefficients of Swirl Coaxial Injectors

Ahn, Kun-Hyuck; Han, Youkyung; Choi, Hwan-Seok

doi:10.1080/00102202.2011.635615

Cited by 17 publications

(10 citation statements)

References 30 publications

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“…It indicates that the attached flame may appear at around 9800 ms, since the kerosene discharge coefficient of Hot-3 test decreases suddenly, as shown in Figure 11. The decrease of discharge coefficient is caused by the backpressure effects 15 arising from the attached flame.…”

Section: Flame Behaviorsmentioning

confidence: 99%

See 1 more Smart Citation

Extreme fuel-rich combustion characteristics of RBCC embedded rocket engine with gas-liquid shear coaxial injectors in continuously varying mixture ratios

Cheng

Kang

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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In order to achieve stable and effective transition between the operation modes in a rocket-based-combined-cycle engine (RBCC), the embedded rocket engine should be capable of throttling continuously in a wide range of operation conditions. A kerosene/GO 2 RBCC embedded rocket engine with gas-liquid shear coaxial injectors was designed to investigate the combustion characteristics under varying operation conditions. Throttling cold test, static hot test, and throttling hot tests in varying mixture ratios (0.102-0.221) were conducted with a throttleable venturi and a throttleable sonic nozzle. In these tests, the mixture ratio was adjusted in two ways: one is to linearly decrease the fuel mass flow rate with a constant oxygen mass flow rate, and the other is to increase the oxygen mass flow rate with a constant fuel mass flow rate. Results indicate that the combustion efficiency and the characteristic velocity increase along with the mixture ratio, but show a different growth rate depending on the mixture ratio adjustment method. To specify, characteristic velocity and combustion efficiency of hot test throttled by increasing oxygen mass flow rate grow faster. And in the range of mixture ratios (È<0.25), the combustion efficiency obtained by both adjustment methods is lower than 55%. The flame behaviors are influenced significantly by the oxygen mass flow rate, and a reasonable explanation is that increasing oxygen mass flow rate can significantly increase the spray angle and decrease the mean diameter. And the flame behaviors can influence the discharge coefficient of the kerosene injector. Furthermore, the discharge coefficient decreases along with the decrease of kerosene mass flow rate in both hot and cold tests.

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Section: Flame Behaviorsmentioning

confidence: 99%

“…In another paper, Ahn et al 14 investigated the effects of chamber pressure on combustion characteristics of kerosene/LO X rocket chamber under fuel rich condition. In addition, both Lim 11 and Ahn 15 found that the discharge coefficient of the injectors was influenced by the flame behavior.…”

Section: Introductionmentioning

confidence: 99%

Extreme fuel-rich combustion characteristics of RBCC embedded rocket engine with gas-liquid shear coaxial injectors in continuously varying mixture ratios

Cheng

Kang

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…Swirl injectors with tangential ports can be classified by their geometry, as follows: closed-type, open-type, or swirl coaxial (Ahn et al 2011). In addition, the swirl coaxial injector can be further divided into gasliquid swirl coaxial injectors and liquid-liquid biswirl coaxial injectors (Ahn et al 2012;Jeon et al 2011;Long 2004;Yang et al 2008). The bi-swirl coaxial injector, which structurally consists of two swirl injectors, has been widely used with the liquid rocket engines to simultaneously discharge the liquid-phase fuel and oxidizer (Ahn et al 2014;Gill and Nurick 1976).…”

Section: Introductionmentioning

confidence: 99%

“…Raghunandan (1998, 2003) investigated the droplet size and the merging characteristics of the liquid sheets. By performing the hot-firing tests, Ahn et al (2011Ahn et al ( , 2012Ahn et al ( , 2014 and found that the recess length affected the discharge coefficient, combustion performance, combustion stability, and heat flux in a combustion chamber. As the recess length was increased, the combustion performance and heat flux increased, and the discharge coefficient and combustion stability sometimes decreased.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Theoretical Study on Spray Angles of Bi-Swirl Coaxial Injectors

Yoon

Ahn

2018

JAFM

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An experimental and theoretical study was undertaken to investigate the effects of the recess length, swirl direction, and mixture ratio on the spray angles of the bi-swirl coaxial injectors with the inner, closed-type and outer, open-type swirl injectors. Eight bi-swirl coaxial injectors with a range of recess lengths and different swirl directions between the inner and outer swirl injectors were used. As the recess length was increased, each bi-swirl coaxial injector exhibited external-mixing, tip-mixing, or internal-mixing spray characteristics. To measure the spray angles, cold-flow tests for which the mass flow rates of the two injectors were varied were performed to capture the spray images. The single-injection results indicated that the spray cone angles of both the inner and outer swirl injectors were relatively unaffected by the mass flow rate and the swirl direction, with the recess length influencing the spray cone angles of the inner swirl injectors. The bi-injection tests show that the spray angles are significantly dependent on the recess length and the mixture ratio, while also being affected by the swirl direction, especially regarding the internal-mixing bi-swirl coaxial injectors. Theoretical models that can predict the spray angles were developed and compared using the experimental data. The theoretical models could approximate the combined spray angles of the internal-mixing bi-swirl coaxial injectors.

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“…The swirling motion induces outward spreading of the liquid film and produces a center toroidal recirculation zone downstream of the injector, thereby significantly improving mixing and combustion efficiency. Extensive experimental [4][5][6][7][8] studies have been conducted to examine the flow characteristics of swirl injectors, including spreading angle, liquid film thickness, and discharge coefficient, under various geometric and operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Study of Cryogenic Fluid Dynamics of Swirl Injectors at Supercritical Conditions

et al. 2017

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A comprehensive study is conducted to enhance the understanding of swirl injector flow dynamics at supercritical conditions. The formulation is based on full-conservation laws and accommodates real-fluid thermodynamics and transport theories over the entire range of fluid states of concern. Liquid oxygen at 120 K is injected into a supercritical oxygen environment at 300-600 K. Detailed three-dimensional flow structures are visualized for the first time in the pressure range of 100-200 atm. A smooth fluid transition from the compressed-liquid to light-gas state occurs, which is in contrast to a distinct interface of phase change at subcritical pressure. Dynamic behaviors of the oscillatory flowfield are explored using the spectral analysis and proper orthogonal decomposition technique. Various underlying mechanisms dictating flow evolution, including shear-layer, helical, centrifugal, and acoustic instabilities, are studied in depth. The hydrodynamic wave motions in the liquid-oxygen film are found to propagate in two different modes: one along the axial direction at the local wave speed; the other in the azimuthal direction and convected downstream at the mean flow velocity. Results show good agreement with the analytical prediction of the overall response transfer function of the swirl injector. The dominant mode of the azimuthal wave is triggered by the natural acoustic oscillation within the injector. Compared with the two-dimensional axisymmetric results, the calculated liquid-oxygen film is thicker and the spreading angle smaller due to the momentum loss and vortical dynamics in the azimuthal direction.

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Effects of Recess Length on Discharge Coefficients of Swirl Coaxial Injectors

Cited by 17 publications

References 30 publications

Extreme fuel-rich combustion characteristics of RBCC embedded rocket engine with gas-liquid shear coaxial injectors in continuously varying mixture ratios

Extreme fuel-rich combustion characteristics of RBCC embedded rocket engine with gas-liquid shear coaxial injectors in continuously varying mixture ratios

Experimental and Theoretical Study on Spray Angles of Bi-Swirl Coaxial Injectors

Comprehensive Study of Cryogenic Fluid Dynamics of Swirl Injectors at Supercritical Conditions

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