Effects of self-pulsation on the spray characteristics of gas–liquid swirl coaxial injector

Kang, Zhongtao; Li, Qinglian; Cheng, Peng; Zhang, Xinqiao; Wang, Zhenguo

doi:10.1016/j.actaastro.2016.05.038

Cited by 36 publications

(7 citation statements)

References 23 publications

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“…It has been confirmed that the high-frequency oscillation of flame is caused by self-pulsation spray. The main factors affecting self-pulsation spray are the recess length , and the gas–liquid ratio. , …”

Section: Results and Discussionmentioning

confidence: 99%

“…In general, the study on the combustion characteristics of gas–liquid swirl coaxial injectors is still relatively macroscopic, mainly analyzing and comparing the combustion performance and combustion stability of this kind of injectors, but there are few studies on the flame structure, flame stability mechanism, and flame dynamic characteristics of them. As swirl coaxial injector self-pulsation will occur under specific operating and structural parameters, − the self-pulsation spray will lead to flame oscillation, which may in turn cause unstable combustion. Kawashima et al established that the flame shows an annular vortex structure during unstable combustion.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study on the Unsteady Spray Combustion Process of a Liquid Oxygen/Methane Swirl Coaxial Injector

Cao

Bai

et al. 2021

ACS Omega

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The present study experimentally investigated the dynamic spray combustion process of a liquid-centered swirl coaxial injector using liquid oxygen/ methane in an optically accessible liquid rocket engine. Data were obtained at combustor pressures from 0.4 to 1.8 MPa and the ratio of the oxidizer mass flow rate to the fuel rate between 1.32 and 1.55. Liquid oxygen was injected at 120 K, and the injection temperature of gaseous methane was about 285 K. Based on the obtained spatial distribution and oscillation characteristics of liquid oxygen/ methane flame, the combustion process was described by four subprocesses: ignition, low-frequency oscillation combustion, quasi-steady state combustion, and shutdown. In the quasi-steady state combustion subprocess, both the flame length and the normalized flame area are the largest, and the flame expansion angle is the smallest. At the initial stage of combustion, the instability of the liquid oxygen phase state leads to flame instability, which generates low-frequency unstable combustion with a dominant frequency of 93.74 Hz. In addition, the highfrequency (2500−3000 Hz) oscillation of the flame appeared in the whole combustion process. It has been confirmed to be caused by the self-pulsation of spray. Furthermore, with the increase in liquid oxygen manifold pressure, the liquid oxygen phase state changes from a two-phase mixture of liquid and gaseous oxygen to a liquid phase, which increases the mass flow rate of liquid oxygen entering into the combustor, thus generating the increase in the high oscillation frequency of the flame through the whole combustion process.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Unsteady Spray Combustion Process of a Liquid Oxygen/Methane Swirl Coaxial Injector

Cao

Bai

et al. 2021

ACS Omega

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“…Schröder et al 2013 [7] found that increasing pulsation frequency decreased the Sauter mean diameter (SMD) and corresponding standard deviation. By contrast, Im et al 2009 [10] and Kang et al 2016 [11] showed that self-pulsation of a gas-liquid swirl coaxial injector led to an increase of the SMD.…”

Section: Introductionmentioning

confidence: 95%

Analysis of Paint Flow Pulsations during High-Speed Rotary Bell Atomization

Oswald¹,

Lauk²,

Gödeke

et al. 2019

Coatings

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High-speed rotary bell atomization is the preeminent coating technique in the automotive industry. It is widely accepted that a narrow droplet size distribution and constant spray are necessary in order to guarantee uniform film thickness and high-quality appearance. This may be deteriorated by paint flow pulsations. So far, however, no studies exist regarding such fluctuations quantitatively for this type of atomizers. We fill this gap using image analysis of high-speed recordings close to the bell edge. We could show that the fundamental pulsation frequency increases linearly with rotational speed. A ratio of pulsation frequency and true rotational speed of about 3 was found, indicating that pulsations were initiated mainly by the three struts of the distributor disc. The coefficient of variation, i.e., the amplitude of fluctuation increased with decreasing liquid volume rate and rotational speed. Beyond that, we could show that the formation of droplets larger than 100 µm, which are assumed to cause paint defects, is promoted by the degree of fluctuation. These findings may stimulate development of bell cups showing less paint flow pulsations.

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“…Thus, this pulsation can amplify unsteady combustion. Kang (Zhongtao et al, 2016) compared a stable spray with a self-pulsation spray and found that the latter could reach a farther radial region. From the perspective of the spatial distribution of the spray, self-pulsation is beneficial for combustion.…”

Section: Introductionmentioning

confidence: 99%

Influence of Self-Pulsation on Atomization Characteristics of Gas-Centered Swirl Coaxial Injector

et al. 2021

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There is a lack of understanding of the spray characteristics of gas-centered swirl coaxial (GCSC) injectors during self-pulsation occurs. Therefore, the self-pulsation of a GCSC injector was investigated experimentally in this study. Experiments were conducted at atmospheric pressure with filtered water and dried air supplied through a propellant feed system. A back-lighting high-speed photography technique was used to capture unsteady spray features. A laser-based particle size analyzer (LPSA) was used to measure the size of the droplets in the spray. The effects of recess and gas-liquid ratio on spray self-pulsation were analyzed. It was found that the recess of the injector strongly determines the spray pattern. When spray self-pulsation occurs without recess, both the center and periphery of the spray oscillate. With an increase in the mass flow rate of the gas, the boundary between the center and the periphery of the spray becomes more noticeable. Meanwhile, small droplets in the spray center oscillate, with the periphery of the spray being characterized by a periodic “shoulder.” Under the same operating conditions but with a small recess (2 mm), the spray adheres to the injector faceplate. With a larger recess (7 mm), when spray self-pulsation occurs, the spray periodically forms “shoulder” and “neck,” similar to the behavior of self-pulsation in a liquid-centered coaxial injector. Therefore, it can be concluded that spray self-pulsation enhances atomization at the center of the spray to a certain extent. However, atomization becomes worse in the periphery with an oscillating spray.

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Effects of self-pulsation on the spray characteristics of gas–liquid swirl coaxial injector

Cited by 36 publications

References 23 publications

Experimental Study on the Unsteady Spray Combustion Process of a Liquid Oxygen/Methane Swirl Coaxial Injector

Experimental Study on the Unsteady Spray Combustion Process of a Liquid Oxygen/Methane Swirl Coaxial Injector

Analysis of Paint Flow Pulsations during High-Speed Rotary Bell Atomization

Influence of Self-Pulsation on Atomization Characteristics of Gas-Centered Swirl Coaxial Injector

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