Pengjin Cao, Chengchao Cui, Peng Cheng, Xiao Bai, Qinglian Li
{"title":"关于液氧/甲烷漩涡同轴喷射器的喷雾和火焰稳定性的研究","authors":"Pengjin Cao, Chengchao Cui, Peng Cheng, Xiao Bai, Qinglian Li","doi":"10.1016/j.combustflame.2024.113532","DOIUrl":null,"url":null,"abstract":"<div><p>Variable-thrust cryogenic propellant rocket engines are gaining significant research interest in space exploration. However, low-frequency unstable combustion is still a challenging scenario, especially in fuel-rich preburner and low-thrust operating conditions of deep variable thrust. To deeply understand the mechanism of low-frequency unstable combustion, chemiluminescence images of CH* and background light images of the spray were obtained synchronously by chemiluminescence imaging and laser background light imaging, respectively. Both the spray and flame stabilization of liquid oxygen/methane swirl coaxial injector were studied through the continuous regulation of liquid oxygen mass flow rate. The results showed that low-frequency unstable combustion occur in both the start-up stage and the throttled stage under the fuel-rich condition at a frequency of 39.1∼48.1 Hz and an amplitude of 30% of the average combustor pressure. It is found that the two-phase flow instability of liquid oxygen is likely to induce spray and flame instability, resulting in low-frequency unstable combustion. The dimension subcooling degree of liquid oxygen is an important factor affecting unstable combustion. When the dimensionless subcooling degree is larger than 0.7, the low-frequency unstable combustion is suppressed. On the other hand, as the mixing ratio decreases, the flame oscillation mode gradually transforms from the longitudinal oscillation mode to contraction/expansion mode. Flame filling up and flashback processes can be observed in both flame oscillation modes, and the entropy coupling mechanism of the oscillation mode is explained in detail. Furthermore, an oscillation period is determined to include four processes: propellants filling up and flame liftoff; heat release of the combustion products and entropy disturbance; acceleration of the entropy wave through the nozzle creating an acoustic disturbance; and flame flashback, in which the heat release time of combustion products and entropy disturbance is the longest.</p></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":null,"pages":null},"PeriodicalIF":5.8000,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Investigation on spray and flame stabilization of a LOX/methane swirl coaxial injector\",\"authors\":\"Pengjin Cao, Chengchao Cui, Peng Cheng, Xiao Bai, Qinglian Li\",\"doi\":\"10.1016/j.combustflame.2024.113532\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Variable-thrust cryogenic propellant rocket engines are gaining significant research interest in space exploration. However, low-frequency unstable combustion is still a challenging scenario, especially in fuel-rich preburner and low-thrust operating conditions of deep variable thrust. To deeply understand the mechanism of low-frequency unstable combustion, chemiluminescence images of CH* and background light images of the spray were obtained synchronously by chemiluminescence imaging and laser background light imaging, respectively. Both the spray and flame stabilization of liquid oxygen/methane swirl coaxial injector were studied through the continuous regulation of liquid oxygen mass flow rate. The results showed that low-frequency unstable combustion occur in both the start-up stage and the throttled stage under the fuel-rich condition at a frequency of 39.1∼48.1 Hz and an amplitude of 30% of the average combustor pressure. It is found that the two-phase flow instability of liquid oxygen is likely to induce spray and flame instability, resulting in low-frequency unstable combustion. The dimension subcooling degree of liquid oxygen is an important factor affecting unstable combustion. When the dimensionless subcooling degree is larger than 0.7, the low-frequency unstable combustion is suppressed. On the other hand, as the mixing ratio decreases, the flame oscillation mode gradually transforms from the longitudinal oscillation mode to contraction/expansion mode. Flame filling up and flashback processes can be observed in both flame oscillation modes, and the entropy coupling mechanism of the oscillation mode is explained in detail. Furthermore, an oscillation period is determined to include four processes: propellants filling up and flame liftoff; heat release of the combustion products and entropy disturbance; acceleration of the entropy wave through the nozzle creating an acoustic disturbance; and flame flashback, in which the heat release time of combustion products and entropy disturbance is the longest.</p></div>\",\"PeriodicalId\":280,\"journal\":{\"name\":\"Combustion and Flame\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":5.8000,\"publicationDate\":\"2024-05-31\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Combustion and Flame\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0010218024002414\",\"RegionNum\":2,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ENERGY & FUELS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Combustion and Flame","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0010218024002414","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENERGY & FUELS","Score":null,"Total":0}
Investigation on spray and flame stabilization of a LOX/methane swirl coaxial injector
Variable-thrust cryogenic propellant rocket engines are gaining significant research interest in space exploration. However, low-frequency unstable combustion is still a challenging scenario, especially in fuel-rich preburner and low-thrust operating conditions of deep variable thrust. To deeply understand the mechanism of low-frequency unstable combustion, chemiluminescence images of CH* and background light images of the spray were obtained synchronously by chemiluminescence imaging and laser background light imaging, respectively. Both the spray and flame stabilization of liquid oxygen/methane swirl coaxial injector were studied through the continuous regulation of liquid oxygen mass flow rate. The results showed that low-frequency unstable combustion occur in both the start-up stage and the throttled stage under the fuel-rich condition at a frequency of 39.1∼48.1 Hz and an amplitude of 30% of the average combustor pressure. It is found that the two-phase flow instability of liquid oxygen is likely to induce spray and flame instability, resulting in low-frequency unstable combustion. The dimension subcooling degree of liquid oxygen is an important factor affecting unstable combustion. When the dimensionless subcooling degree is larger than 0.7, the low-frequency unstable combustion is suppressed. On the other hand, as the mixing ratio decreases, the flame oscillation mode gradually transforms from the longitudinal oscillation mode to contraction/expansion mode. Flame filling up and flashback processes can be observed in both flame oscillation modes, and the entropy coupling mechanism of the oscillation mode is explained in detail. Furthermore, an oscillation period is determined to include four processes: propellants filling up and flame liftoff; heat release of the combustion products and entropy disturbance; acceleration of the entropy wave through the nozzle creating an acoustic disturbance; and flame flashback, in which the heat release time of combustion products and entropy disturbance is the longest.
期刊介绍:
The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on:
Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including:
Conventional, alternative and surrogate fuels;
Pollutants;
Particulate and aerosol formation and abatement;
Heterogeneous processes.
Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including:
Premixed and non-premixed flames;
Ignition and extinction phenomena;
Flame propagation;
Flame structure;
Instabilities and swirl;
Flame spread;
Multi-phase reactants.
Advances in diagnostic and computational methods in combustion, including:
Measurement and simulation of scalar and vector properties;
Novel techniques;
State-of-the art applications.
Fundamental investigations of combustion technologies and systems, including:
Internal combustion engines;
Gas turbines;
Small- and large-scale stationary combustion and power generation;
Catalytic combustion;
Combustion synthesis;
Combustion under extreme conditions;
New concepts.