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Статті в журналах з теми "Transcritical combustion":
1
Singla, G., P. Scouflaire, C. Rolon, and S. Candel. "Transcritical oxygen/transcritical or supercritical methane combustion." Proceedings of the Combustion Institute 30, no. 2 (January 2005): 2921–28. http://dx.doi.org/10.1016/j.proci.2004.08.063.
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Pons, L., N. Darabiha, S. Candel, G. Ribert, and V. Yang. "Mass transfer and combustion in transcritical non-premixed counterflows." Combustion Theory and Modelling 13, no. 1 (January 22, 2009): 57–81. http://dx.doi.org/10.1080/13647830802368821.
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ANTUNES, Eduardo, Andre SILVA, and Jorge BARATA. "Modelling of transcritical and supercritical nitrogen jets." Combustion Engines 169, no. 2 (May 1, 2017): 125–32. http://dx.doi.org/10.19206/ce-2017-222.
Анотація:
The present paper addresses the modelling of fuel injection at conditions of high pressure and temperature which occur in a variety of internal combustion engines such as liquid fuel rocket engines, gas turbines, and modern diesel engines. For this investigation a cryogenic nitrogen jet ranging from transcritical to supercritical conditions injected into a chamber at supercritical conditions was modelled. Previously a variable density approach, originally conceived for gaseous turbulent isothermal jets, imploying the Favre averaged Navier-Stokes equations together with a “k-ε” turbulence model, and using Amagats law for the determination of density was applied. This approach allows a good agreement with experiments mainly at supercritical injection conditions. However, some departure from experimental data was found at transcritical injection conditions. The present approach adds real fluid thermodynamics to the previous approach, and the effects of heat transfer. The results still show some disagreement at supercritical conditions mainly in the determination of the potential core length but significantly improve the prediction of the jet spreading angle at transcritical injection conditions.
4
Giacomazzi, Eugenio, Donato Cecere, and Nunzio Arcidiacono. "Flame Anchoring of an H2/O2 Non-Premixed Flamewith O2 Transcritical Injection." Aerospace 9, no. 11 (November 11, 2022): 707. http://dx.doi.org/10.3390/aerospace9110707.
Анотація:
The article is devoted to the analysis of the flame anchoring mechanism in the test case MASCOTTE C-60 RCM2 on supercritical hydrogen/oxygen combustion at 60 bar, with transcritical (liquid) injection of oxygen. The case is simulated by means of the in-house parallel code HeaRT in the three-dimensional LES framework. The cubic Peng–Robinson equation of state in its improved translated volume formulation is assumed. Diffusive mechanisms and transport properties are accurately modeled. A finite-rate detailed scheme involving the main radicals, already validated for high-pressure H2/O2 combustion, is adopted. The flow is analysed in terms of temperature, hydrogen and oxygen instantaneous spatial distributions, evidencing the effects of the vortex shedding from the edges of the hydrogen injector and of the separation of the oxygen stream in the divergent section of its tapered injector on the flame anchoring and topology. Combustion conditions are characterised by looking at the equivalence ratio and compressibility factor distributions.
5
Delplanque, J. P., and W. A. Sirignano. "Transcritical liquid oxygen droplet vaporization - Effect on rocket combustion instability." Journal of Propulsion and Power 12, no. 2 (March 1996): 349–57. http://dx.doi.org/10.2514/3.24035.
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Ricci, Daniele, Francesco Battista, and Manrico Fragiacomo. "Transcritical Behavior of Methane in the Cooling Jacket of a Liquid-Oxygen/Liquid-Methane Rocket-Engine Demonstrator." Energies 15, no. 12 (June 7, 2022): 4190. http://dx.doi.org/10.3390/en15124190.
Анотація:
The successful design of a liquid rocket engine is strictly linked to the development of efficient cooling systems, able to dissipate huge thermal loads coming from the combustion in the thrust chamber. Generally, cooling architectures are based on regenerative strategies, adopting fuels as coolants; and on cooling jackets, including several narrow axial channels allocated around the thrust chambers. Moreover, since cryogenic fuels are used, as in the case of oxygen/methane-based liquid rocket engines, the refrigerant is injected in liquid phase at supercritical pressure conditions and heated by the thermal load coming from the combustion chamber, which tends to experience transcritical conditions until behaving as a supercritical vapor before exiting the cooling jacket. The comprehension of fluid behavior inside the cooling jackets of liquid-oxygen/methane rocket engines as a function of different operative conditions represents not only a current topic but a critical issue for the development of future propulsion systems. Hence, the current manuscript discusses the results concerning the cooling jacket equipping the liquid-oxygen/liquid-methane demonstrator, designed and manufactured within the scope of HYPROB-NEW Italian Project. In particular, numerical results considering the nominal operating conditions and the influence of variables, such as the inlet temperature and pressure values of refrigerant as well as mass-flow rate, are shown to discuss the fluid transcritical behavior inside the cooling channels and give indications on the numerical methodologies, supporting the design of liquid-oxygen/liquid-methane rocket-engine cooling systems. Validation has been accomplished by means of experimental results obtained through a specific test article, provided with a cooling channel, characterized by dimensions representative of HYPROB DEMO-0A regenerative combustion chamber.
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DELPLANQUE, J. P., and W. A. SIRIGNANO. "Transcritical Vaporization and Combustion of LOX Droplet Arrays in a Convective Environment." Combustion Science and Technology 105, no. 4-6 (April 1995): 327–44. http://dx.doi.org/10.1080/00102209508907757.
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Wang, Siyuan, Haiou Wang, Kun Luo, and Jianren Fan. "The Effects of Differential Diffusion on Turbulent Non-Premixed Flames LO2/CH4 under Transcritical Conditions Using Large-Eddy Simulation." Energies 16, no. 3 (January 18, 2023): 1065. http://dx.doi.org/10.3390/en16031065.
Анотація:
In this paper, a large-eddy simulation (LES) of turbulent non-premixed LO2/CH4 combustion under transcritical conditions is performed based on the Mascotte test rig from the Office National d’Etudes et de Recherches Ae´rospatiales (ONERA), and the aim is to understand the effects of differential diffusion on the flame behaviors. In the LES, oxygen was injected into the environment above the critical pressure while the temperature was below the critical temperature. The flamelet/progress variable (FPV) approach was used as the combustion model. Two LES cases with different species diffusion coefficient schemes—i.e., non-unity and unity Lewis numbers—for generating the flamelet tables were carried out to explore the effects of differential diffusion on the flame and flow structures. The results of the LES case with non-unity Lewis numbers were in good agreement with the experimental data. It was shown that differential diffusion had evident impacts on the flame structure and flow dynamics. In particular, when unity Lewis numbers were used to evaluate the species diffusion coefficient, the flame length was underestimated and the flame expansion was more significant. Compared to laminar counterflow flames, turbulence in jet flames allows chemical reactions to take place in a wider range of mixture fractions. The density distributions of the two LES cases in the mixture fraction space were very similar, indicating that differential diffusion had no significant effects on the phase transition under transcritical conditions.
9
Liu, Liuchen, Qiguo Yang, and Guomin Cui. "Supercritical Carbon Dioxide(s-CO2) Power Cycle for Waste Heat Recovery: A Review from Thermodynamic Perspective." Processes 8, no. 11 (November 15, 2020): 1461. http://dx.doi.org/10.3390/pr8111461.
Анотація:
Supercritical CO2 power cycles have been deeply investigated in recent years. However, their potential in waste heat recovery is still largely unexplored. This paper presents a critical review of engineering background, technical challenges, and current advances of the s-CO2 cycle for waste heat recovery. Firstly, common barriers for the further promotion of waste heat recovery technology are discussed. Afterwards, the technical advantages of the s-CO2 cycle in solving the abovementioned problems are outlined by comparing several state-of-the-art thermodynamic cycles. On this basis, current research results in this field are reviewed for three main applications, namely the fuel cell, internal combustion engine, and gas turbine. For low temperature applications, the transcritical CO2 cycles can compete with other existing technologies, while supercritical CO2 cycles are more attractive for medium- and high temperature sources to replace steam Rankine cycles. Moreover, simple and regenerative configurations are more suitable for transcritical cycles, whereas various complex configurations have advantages for medium- and high temperature heat sources to form cogeneration system. Finally, from the viewpoints of in-depth research and engineering applications, several future development directions are put forward. This review hopes to promote the development of s-CO2 cycles for waste heat recovery.
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Farzaneh-Gord, Mahmood, Aliakbar Mirmohammadi, Mohammadreza Behi, and Amin Yahyaie. "Heat recovery from a natural gas powered internal combustion engine by CO2 transcritical power cycle." Thermal Science 14, no. 4 (2010): 897–911. http://dx.doi.org/10.2298/tsci1004897f.
Дисертації з теми "Transcritical combustion":
1
Rose, Evan Noah. "Autoignition Dynamics and Combustion of n-Dodecane Dropletsunder Transcritical Conditions." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1554288408975334.
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Ruiz, Anthony. "Unsteady Numerical Simulations of Transcritical Turbulent Combustion in Liquid Rocket Engines." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0009/document.
Анотація:
Ces cinquantes dernières années, la majorité des paramètres de conception des moteurs cryotechniques ont été ajustés en l'absence d'une compréhension détaillée des phénomènes de combustion, en raison des limites des diagnostiques expérimentaux et des capacités de calcul. L'objectif de cette thèse est de réaliser des simulations numériques instationnaires d'écoulements réactifs transcritiques de haute fidélité, pour permettre une meilleure compréhension de la dynamique de flamme dans les moteurs cryotechniques et finalement guider leur amélioration. Dans un premier temps, la thermodynamique gaz-réel et son impact sur les schémas numériques sont présentés. Comme la Simulation aux Grandes Echelles (SGE) comporte des équations filtrées, les effets de filtrages induits par la thermodynamique gaz-réel sont ensuite mis en évidence dans une configuration transcritique type et un opérateur de diffusion artificiel, spécifique au gaz réel, est proposé pour lisser les gradients transcritiques en SGE. Dans un deuxième temps, une étude fondamentale du mélange turbulent et de la combustion dans la zone proche-injecteur des moteurs cryotechniques est menée grâce à la Simulation Numérique Directe (SND). Dans le cas non-réactif, les lâchers tourbillonnaires dans le sillage de la lèvre de l’injecteur jouent un rôle majeur dans le mélange turbulent et provoquent la formation de structures en peigne déjà observées expérimentalement dans des conditions similaires. Dans le cas réactif, la flamme reste attachée à la lèvre de l'injecteur, sans extinction locale, et les structures en peigne disparaissent. La structure de flamme est analysée et différents modes de combustion sont identifiés. Enfin, une étude de flamme-jet transcritique H2/O2, accrochée à un injecteur coaxial avec et sans retrait interne, est menée. Les résultats numériques sont d'abord validés par des données expérimentales pour l'injecteur sans retrait. Ensuite, la configuration avec retrait est comparée à la solution de référence sans retrait et à des données experimentales pour observer les effets de ce paramètre de conception sur l'efficacité de combustionIn the past fifty years, most design parameters of the combustion chamber of Liquid Rocket Engines (LREs) have been adjusted without a detailed understanding of combustion phenomena, because of both limited experimental diagnostics and numerical capabilities. The objective of the present thesis work is to conduct high-fidelity unsteady numerical simulations of transcritical reacting flows, in order to improve the understanding of flame dynamics in LRE, and eventually provide guidelines for their improvement. First real-gas thermodynamics and its impact on numerical schemes are presented. As Large-Eddy Simulation (LES) involves filtered equations, the filtering effects induced by real-gas thermodynamics are then highlighted in a typical 1D transcritical configuration and a specific real-gas artificial dissipation is proposed to smooth transcritical density gradients in LES. Then, a Direct Numerical Simulation (DNS) study of turbulent mixing and combustion in the near-injector region of LREs is conducted. In the non-reacting case, vortex shedding in the wake of the lip of the injector is shown to play a major role in turbulent mixing, and induces the formation of finger-like structures as observed experimentally in similar operating conditions. In the reacting case, the flame is attached to the injector rim without local extinction and the finger-like structures disappear. The flame structure is analyzed and various combustion modes are identified. Finally, a LES study of a transcritical H2/O2 jet flame, issuing from a coaxial injector with and without inner recess, is conducted. Numerical results are first validated against experimental data for the injector without recess. Then, the recessed configuration is compared to the reference solution and to experimental results, to scrutinize the effects of this design parameter on combustion efficiency
3
Gaillard, Pierre. "Interfaces diffuses et flammes transcritiques LOX/H2." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066510/document.
Анотація:
Dans les moteurs cryotechniques, les ergols sont refroidis pour être stockés sous forme liquide et limiter ainsi la taille des réservoirs. Ils sont ensuite mis sous pression, grâce à une turbopompe, avant d’être injectés dans la chambre de combustion. Pour augmenter les rendements des moteurs, la pression de chambre est augmentée et peut dépasser les pressions critiques des ergols. Le régime de combustion supercritique est alors appelé transcritique lorsque l’oxygène est injecté à une température inférieure à sa température critique avec une densité équivalente à celle d’un liquide. Ce régime possède certaines propriétés des injections diphasiques avec un dard dense mais sans présenter de phénomène d’atomisation ce qui le rapproche des injections gaz-gaz. L’étude de la transition dense-dilué de l’oxygène a été le dénominateur commun de cette thèse. En régime supercritique, l’épaisseur de cette transition diminue avec la pression jusqu’à devenir infiniment fine à la pression critique. Le manque de discrétisation des zones à forts gradients conduit à des instabilités numériques. Cette situation est analogue numériquement au cas d’une interface liquide vapeur subcritique. C’est pourquoi nous avons étendu dans cette thèse des méthodes d’interface diffuse au régime supercritique. La méthode dite de second gradient introduite par van der Waals a permis de simuler des flammes étirées subcritiques et supercritiques. Tandis que l’approche multifluide a été utilisée pour réaliser des simulations aux grandes échelles du banc d'essai MASCOTTE en régime supercritique avec le code CEDREIn cryogenic engines, the propellants are refrigerated and stored liquid in order to limit the dimension of the tanks. They are pressurized by turbopumps before their injection in the combustion chamber. To increase the efficiency of the engines, the chamber pressure is increased and can be above the critical pressure of the propellants. This combustion regime is called transcritical. It exhibits some properties of diphasic injection with a high density core jet but does not have a phenomenon of atomization. The study of the oxygen transition from dense to light has been the main objectives of this thesis. In supercritical regime, the width of this transition decreases with the pressure till it reaches the critical pressure where it becomes infinitely thin. The lack of discretization in the zone of strong gradients leads to numerical instabilities. This situation is analog from a numerical point of view to a liquid-vapor interface. Thus, in this thesis we have extented the diffuse interface methods to the supercritical regime. The second gradient method introduced by van der Waals has allowed the simulation of subcritical and supercritical flames. The multifluid approach has been implemented in the solver CEDRE for the computation of a large eddy simulation of the experimental bench MASCOTTE in supercritcal conditions
4
Lechner, Valentin. "Experimental study of LOX/CH4 flames in rocket engines." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST040.
Анотація:
Utiliser le méthane comme carburant dans les moteurs fusées présente beaucoup d'avantages mais la combustion avec de l'oxygène pur à haute pression reste mal comprise. D'un point de vue thermodynamique, le méthane et l'oxygène partagent des valeurs de point critique très similaires, ce qui rend difficile la prédiction du mélange des ergols, l'accrochage, la stabilité et la structure de la flamme. De plus, quand le méthane est injecté en excès, des aérosols peuvent être produits, pouvant obstruer les lignes, endommager la turbine et réduire le rendement.Une mise à jour approfondie des connaissances sur la combustion LOX/CH4 est donc nécessaire. Ce défi est relevé au sein du consortium composé du laboratoire EM2C, de l'ONERA, du CNES et d'ArianeGroup. Deux campagnes d'essais sont menées sur le banc MASCOTTE de l'ONERA visant à étudier trois sujets centraux : la structure de la flamme, les transferts thermiques aux parois et la production d'aérosols. Dans ce but, divers diagnostics expérimentaux sont mis en œuvre simultanément pendant des essais à feu à haute pression.Différents diagnostics d'imagerie sont mis en place pour analyser la structure de la flamme et des jets liquides. Malgré les difficultés d'acquisition rencontrées dans ces conditions extrêmes, les analyses révèlent une structure de flamme complexe. En régime subcritique, les mécanismes d'atomisation et d'évaporation dominent. La flamme est alors bien plus ouverte et plus longue qu'à de plus hautes pressions, où les mécanismes de mélange diffusifs prévalent. Caractériser l'accrochage de la flamme reste un défi. En effet, un anneau de glace, probablement d'eau, entoure et masque le pied de la flamme. Des mécanismes de formation sont proposés et un cycle temporel de croissance/destruction est mis en avant. Sa présence affecte fortement la visualisation de la flamme, et peut conduire à des interprétations erronées de sa topologie.Pour la première fois à MASCOTTE, la phosphorescence induite par laser (LIP) est mise en place. Diverses méthodes LIP existent mais ne sont pas bien adaptées aux conditions de MASCOTTE : large gamme de températures, transitoires thermiques et environnement diphasique. C'est pourquoi une méthode spécifique a été mise au point (Full Spectrum Fitting method). Elle exploite la dépendance spectrale à la température, permettant des mesures instantanées de 100 à 900 K avec une précision de 17 K, sans dépendance à l'énergie d'excitation laser. Une analyse détaillée des données met en évidence les modes de transfert de chaleur prédominants, étudie l'influence des points de fonctionnement et compare les données expérimentales avec un modèle de transferts thermiques de paroi, particulièrement bien adapté pour déduire les caractéristiques convectives de l'écoulement à la paroi.Différents diagnostics sont mis en œuvre pour caractériser les aérosols. Une sonde intrusive prélève les particules et les gaz brûlés en aval de la flamme. Les particules sont prélevées sur des grilles adaptées à des analyses par microscopie électronique à transmission (TEM). Les images détaillées de leurs morphologies révèlent qu'il s'agit de suies. Les gaz sont analysés par chromatographie en phase gazeuse. Ceci permet d'identifier des molécules précurseurs des suies comme le benzène et l'acétylène. Les suies sont quantifiées temporellement par extinction laser. Des post-traitements dédiés sont développés et diverses hypothèses sont discutées pour expliquer les variations spatiales de production de suiesUsing methane as a fuel in rocket engines would have many advantages but the combustion with pure oxygen at high pressure remains poorly understood. From a thermodynamic point of view, methane and oxygen share very similar critical point values, making it challenging to predict propellant mixing, flame anchoring, stability and structure. Moreover, when methane is injected in excess, aerosols can be produced, which can clog the lines, damage the turbine, and reduce the efficiency.Therefore, a thorough update of the knowledge of LOX/CH4 combustion is necessary. These challenges are tackled within the consortium composed of EM2C laboratory, ONERA, CNES, and ArianeGroup. Two test campaigns are carried out at the MASCOTTE facility from ONERA, aiming to study three central topics: the flame structure, wall heat transfers, and aerosol production. To this end, various experimental diagnostics are implemented simultaneously during high-pressure hot-fire tests.Various imaging diagnostics are implemented to analyze the flame structure and the dense liquid jets. Despite the acquisition difficulties encountered in these extreme conditions, the analyses reveal a complex flame structure. In the subcritical regime, atomization and evaporation mechanisms dominate. The flame is much more opened and longer than at higher pressures, where diffusive mixing mechanisms prevail. Characterizing flame anchoring remains a challenge. A water ice ring surrounding, and masking, the flame foot has been identified. Formation mechanisms are proposed, and a growth/destruction temporal cycle is highlighted. Its presence strongly affects flame visualizations, and may lead to misinterpretations of its topology.Laser-induced phosphorescence (LIP) is implemented for the first time at MASCOTTE. Various LIP methods exist, but they are not well suited to the MASCOTTE conditions: wide temperature range, thermal transients, and two-phase flow environment favoring laser absorption/diffusion. Therefore, a specific method, the Full Spectrum Fitting method (FSF method), has been developed. It exploits the spectral dependence on temperature, enabling instantaneous measurements from 100 to 900 K with a precision of 17 K, with no dependence on the laser excitation energy. A detailed data analysis highlights the predominant wall heat transfer modes, studies the influence of the operating points, and compares the experimental data with a wall heat transfer model, which is particularly well suited for deducing the convective properties of the flow.Three diagnostics are used to characterize aerosols. An intrusive probe samples particles and burnt gases downstream of the flame. The particles are sampled on TEM grids and analyzed by Transmission Electron Microscopy. Detailed images of the aerosol morphology reveal that the particles are soot. Combustion products are analyzed by gas chromatography. This makes it possible to identify soot precursor molecules such as benzene and acetylene. Soot are quantified temporally by laser extinction. A dedicated post-processing method is developed and various hypotheses are discussed to explain the spatial variations of the soot production downstream of the flame
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Gonzalez, Flesca Manuel. "Contributions en simulation, expérimentation et modélisation destinées à l’analyse des instabilités de combustion hautes fréquences des moteurs fusées à ergols liquides." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC088/document.
Анотація:
Cette recherche se focalise sur les problèmes d’instabilités de combustion hautes fréquences dans les moteurs fusées. Ces instabilités sont connues pour avoir des effets néfastes et peuvent, dans certains cas, causer la destruction du système propulsif. Pour éviter l’apparition de ces instabilités, il est important de connaître les mécanismes qui entretiennent ces phénomènes dynamiques et de comprendre le couplage complexe entre l’injection, la combustion et la résonnance acoustique du système. Ce travail comprend trois parties.La première partie traite de la simulation numérique de jets non-réactifs et réactifs soumis à différentes conditions de modulation afin de comprendre les interactions entre les jets, les flammes et leur environnement. Les calculs numériques de jets ronds non-réactifs ainsi que des flammes plus complexes formées par des injecteurs coaxiaux dans des conditions transcritiques ont été effectuées avec des simulations aux grandes échelles (SGE), adaptées aux conditions gaz réels à l’aide du solveur AVBP-RG. Les jets ronds ont été soumis à des fluctuations de vitesse transverse. Il a été trouvé que pour toutes les amplitudes et fréquences de modulation, le jet est déformé et oscille dans la direction transverse. Ce comportement peut être représenté par un modèle. Les flammes coaxiales ont été soumises à une modulation de débit et de pression. La modulation induit des variations du dégagement de chaleur global. Un modèle mathématique reliant les paramètres modulés au dégagement de chaleur est proposé.La seconde partie contient les travaux expérimentaux. Dans ce cadre, un nouveau banc expérimental a été développé pour l’étude de cavités couplées pressurisées (NPCC). Le couplage entre le plénum (ou dôme) et la chambre a été étudié. Un modèle reliant les fluctuations de pression et de vitesse en sortie des injecteurs a été développé et comparés aux données d’essais. Le banc NPCC a aussi été utilisé pour acquérir plus de connaissances sur le niveau d’amortissement. Les coefficients d’amortissement ont été déterminés.La dernière partie de ce document traite du développement d’un modèle ordre réduit qui représente des mécanismes qui entretiennent et amortissent les instabilités de combustion hautes fréquences. Cette description dynamique a été incorporée dans un code de stabilité haute fréquence (STAHF). Ce code a été utilisé pour étudier un moteur à ergols liquides d’une puissance de 87 MW (le banc BKD du DLR en Allemagne) qui présente des instabilités hautes fréquences. Après le recalage de certains paramètres de contrôle, STAHF a été capable de retrouver des résultats obtenus d’essais au DLRThis research concerns some of the issues raised by high frequency combustion instabilities in rocket engines. These instabilities are known to have detrimental effects leading, in some cases, to the destruction of the propulsion system. To avoid the appearance of such instabilities it is important to gain an understanding of the processes driving such dynamical phenomena. One has to consider the complex coupling between injection, combustion and the acoustic resonances of the system. The present work contributes to this objective by developing three items.The first deals with numerical simulations of non-reactive and reactive jets submitted to different modulation conditions to understand the interaction between jets, flames and their environment. Numerical simulations of non-reactive round jets as well as more complex flames formed by coaxial injectors operating under transcritical conditions were carried out using large eddy simulation (LES) adapted to real gas situations by making use of the AVBP-RG flow solver. Round jets were submitted to transverse velocity fluctuations. It has been found that for all amplitudes and frequencies of modulation, the modulated jet is deformed and oscillates. This behavior can be represented by a model. The coaxial flames were submitted to mass flow rate and pressure modulation. For these cases it has been found that the modulation induces variations of the global heat release rate. A mathematical relationship between the modulated parameters and the heat release rate has been proposed.The second item includes experimental investigations. For this purpose a New Pressurized Coupled Cavities (NPCC) laboratory test rig has been developed. The possible coupling between the plenum and the thrust chamber was studied. A model, linking pressure and velocity fluctuations between the plenum and the thrust chamber, has been developed. The laboratory test rig was also used to gather some knowledge on the levels of damping and the damping coefficients could be determined.The last item of this document deals with the development of a reduced order dynamical model which includes some of the driving and damping mechanisms of high frequency combustion instabilities. This dynamical description was implemented in a high frequency stability code (STAHF). This code was used to examine a 87 MW liquid rocket engine (BKD operated at DLR, Germany) exhibiting high frequency oscillations. After the adjustment of some control parameters, STAHF was able to retrieve some the features observed in experiments carried out at DLR
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Yang, Songzhi. "Modeling of Diesel injection in subcritical and supercritical conditions." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC045/document.
Анотація:
Pour satisfaire aux dernières réglementations en matière d'émissions, des progrès importants sont encore attendus des moteurs à combustion interne. De plus, améliorer l'efficacité du moteur pour réduire les émissions et la consommation de carburant est devenu plus essentiel qu'auparavant. Mais, de nombreux phénomènes complexes restent mal compris dans ce domaine, tels que le processus d'injection de carburant. Nombreux logiciels pour la dynamique des fluides numérique (CFD) prenant en compte le changement de phase (comme la cavitation) et la modélisation de l’injection ont été développés et utilisés avec succès dans le processus d’injection. Néanmoins, il existe peu de codes CFD capables de simuler avec précision des conditions d’injection transcritiques, à partir d'une condition de température de carburant sous-critique vers un mélange supercritique dans la chambre de combustion. En effet, la plupart des modèles existants peuvent simuler des écoulements à phase unique, éventuellement dans des conditions supercritiques, ou des écoulements diphasiques dans des conditions sous-critiques. Par conséquent, il manque un modèle complet capable de traiter les conditions transcritiques, y compris la transition de phase possible entre les régimes souscritiques et supercritiques, ou entre les écoulements monophasiques et diphasiques, de manière dynamique. Cette thèse a pour objectif de relever ce défi.Pour cela, des modèles d'écoulement diphasique compressible de fluide réel basés sur une approche eulérienne-eulérienne avec prise en compte de l'équilibre de phase ont été développés et discutés dans le présent travail. Plus précisément, un modèle à 6-équation entièrement compressibles incluant les équations de bilan des phases liquide et gazeuse résolues séparément ; et un modèle à 4-équation qui résout les équations des bilans liquide et gazeux en équilibre mécanique et thermique sont proposés dans ce manuscrit. L’équation d’état Peng-Robinson EoS est sélectionné pour fermer les deux systèmes et pour faire face aux éventuels changements de phase et à la transition ou à la séparation des phases. En particulier, un solveur d'équilibre de phase a été développé et validé. Ensuite, une série de tests académiques 1D portant sur les phénomènes d'évaporation et de condensation effectués dans des conditions sous-critiques et supercritiques a été simulée et comparée aux données de la littérature et aux résultats académiques disponibles. Ensuite, les modèles d'écoulement en deux phases entièrement compressibles (systèmes à 6-équation et à 4- équation) ont été utilisés pour simuler les phénomènes de cavitation dans une buse 3D de taille réelle afin d'étudier l'effet de l’azote dissous sur la création et le développement de la cavitation. Le bon accord avec les données expérimentales prouve que le solveur proposé est capable de gérer le comportement complexe du changement de phase dans des conditions sous-critiques. Enfin, la capacité du solveur à traiter l’injection transcritique à des pressions et températures élevées a été validée par la modélisation réussie de l’injecteur Spray A du réseau de combustion moteur (ECN)To satisfy latest stringent emission regulations, important progress is still be expected from internal combustion engines. In addition, improving engine efficiency to reduce the emission and fuel consumption has become more essential than before. But many complex phenomena remain poorly understood in this field, such as the fuel injection process. Numerous software programs for computational fluid dynamics (CFD) considering phase change (such as cavitation) and injection modelling, have been developed and used successfully in the injection process. Nevertheless, there are few CFD codes able to simulate correctly transcritical conditions starting from a subcritical fuel temperature condition towards a supercritical mixture in the combustion chamber. Indeed, most of the existing models can simulate either single-phase flows possibly in supercritical condition or two-phase flows in subcritical condition; lacking therefore, a comprehensive model which can deal with transcritical condition including possible phase transition from subcritical to supercritical regimes, or from single-phase to two-phase flows, dynamically. This thesis aims at dealing with this challenge. For that, real fluid compressible two-phase flow models based on Eulerian-Eulerian approach with the consideration of phase equilibrium have been developed and discussed in the present work. More precisely, a fully compressible 6-equation model including liquid and gas phases balance equations solved separately; and a 4-equation model which solves the liquid and gas balance equations in mechanical and thermal equilibrium, are proposed in this manuscript. The Peng-Robinson equation of state (EoS) is selected to close both systems and to deal with the eventual phase change or phase transition. Particularly, a phase equilibrium solver has been developed and validated. Then, a series of 1D academic tests involving the evaporation and condensation phenomena performed under subcritical and supercritical conditions have been simulated and compared with available literature data and analytical results. Then the fully compressible two-phase flow models (6-Equation and 4-Equation systems) have been employed to simulate the cavitation phenomena in a real size 3D nozzle to investigate the effect of dissolved N2 on the inception and developing of cavitation. The good agreement with experimental data proves the solver can handle the complex phase change behavior in subcritical condition. Finally, the capability of the solver in dealing with the transcritical injection at high pressure and temperature conditions has been further validated through the successful modelling of the engine combustion network (ECN) Spray A injector
Частини книг з теми "Transcritical combustion":
1
Olmeda, Raffaele, and Christian Stemmer. "LES of N2/H2 Transcritical Injection in a Rocket Combustion Chamber." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 569–78. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-79561-0_54.
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"Chapter 10. Spray Modeling of GCH4/LOx Combustion at Transcritical Condition." In Advances in Multiphase Flows. Begell House Inc., 2022. http://dx.doi.org/10.1615/978-1-56700-504-2.228.
Тези доповідей конференцій з теми "Transcritical combustion":
1
Williams, Forman. "Transcritical acoustic response in hydrogen-oxygen combustion." In 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-3539.
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Crua, Cyril, Julien Manin, Scott Skeen, and Lyle M. Pickett. "Transcritical mixing of fuels at reactive conditions." In 2023 JSAE/SAE Powertrains, Energy and Lubricants International Meeting. 10-2 Gobancho, Chiyoda-ku, Tokyo, Japan: Society of Automotive Engineers of Japan, 2023. http://dx.doi.org/10.4271/2023-32-0117.
Анотація:
<div class="section abstract"><div class="htmlview paragraph">Although progress has recently been made to characterise the transition of microscopic liquid fuel droplets from classical evaporation to a diffusive mixing regime, still little is known about the transition from one to the other under reactive conditions. The lack of experimental data for microscopic droplets at realistic operating conditions impedes the development of phenomenological and numerical models for droplet mixing, ignition, combustion and soot formation. In order to address this issue we performed systematic measurements using high- speed long-distance microscopy, for n-dodecane into gas at elevated temperatures (from 750 to 1,600 K) and pressures up to 13 MPa. We describe these high- speed visualizations at the microscopic level, including the time evolution of the liquid droplets, reaction wave, and soot distribution. Our measurements show that these parameters are influenced by the operating conditions (gas pressure, gas temperature, oxygen content) as well as the physical properties of the fuel.</div></div>
3
Srinivasan, Navneeth, Hongyuan Zhang, and Suo Yang. "A VLE-Based Reacting Flow Solver for High-Pressure Transcritical Two-Phase Combustion." In AIAA SCITECH 2023 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2023. http://dx.doi.org/10.2514/6.2023-1858.
4
Müller, H., and M. Pfitzner. "Large-eddy simulation of transcritical liquid oxygen/methane jet flames." In Progress in Propulsion Physics – Volume 11. Les Ulis, France: EDP Sciences, 2019. http://dx.doi.org/10.1051/eucass/201911177.
Анотація:
A numerical method to perform large-eddy simulations (LES) of nonpremixed liquid oxygen/methane (LOx/CH4) combustion at supercritical pressures is presented and the computational results are compared with available experimental data. The injection conditions of the considered test case resemble those in typical liquid-propellant rocket engines (LRE). Thermodynamic nonidealities are modeled using the Peng–Robinson (PR) equation of state (EoS) in conjunction with a novel volume-translation method to correct deficiencies in the transcritical regime. The resulting formulation is more accurate than the standard cubic EoS's without deteriorating their good computational efficiency. The real-gas thermodynamics model is coupled with the steady laminar flamelet model (SLFM) for turbulent nonpremixed combustion to incorporate chemical reactions at reasonable computational cost in the LES. A reduced reaction mechanism, which is validated with respect to the full mechanism, is used to generate a flamelet library. A comparison of the LES result with available OH* measurements shows that important flow features are well predicted.
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Manin, Julien, Cyril Crua, and Lyle M. Pickett. "Transcritical mixing of sprays for multi-component fuel mixtures." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5065.
Анотація:
The mixing of fuels with oxidizer has been an increasingly interesting area of research with new engine technologiesand the need to reduce emissions, while leveraging efficiency. High-efficiency combustion systems such as diesel engines rely on elevated chamber pressures to maximize power density, producing higher output. In such systems, the fuel is injected under liquid state in a chamber filled with pressurized air at high temperatures. Theoretical calculations on the thermodynamics of fuel mixing processes under these conditions suggest that the injected liquid can undergo a transcritical change of state. Our previous experimental efforts in that regard showed through high- speed imaging that spray droplets transition to fluid parcels mixing without notable surface tension forces, supporting a transcritical process. Only mono-component fuels were used in these studies to provide full control over boundary conditions, which prevented extrapolation of the findings to real systems in which multi-component fuels are injected. Multi-component fuels add another layer of complexity, especially when detailed experiments serve model development, requiring the fuels to be well characterized. In this work, we performed high-speed microscopy in the near-field of high-pressure sprays injected into elevated temperature and pressure environments. A reference diesel fuel and several multi-component surrogates were studied and compared to single component fuels. The results support that a transition occurs under certain thermodynamic conditions for all fuels. As anticipated, the transition from classical evaporation to diffusive mixing is affected by ambient conditions, fuel properties, droplet size and velocity, as well as time scales. Analogous to previous observations made with the normal alkane sprays, the behavior of the multi-component fuels correlate well with their bulk critical properties.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5065
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Rodriguez, Carlos, Alvaro Vidal, Phoevos Koukouvinis, and Manolis Gavaises. "Supercritical and transcritical real-fluid mixing using the PC-SAFT EOS." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.5000.
Анотація:
A numerical framework has been developed to simulate the mixing of supercritical and transcritical fluids using anequation of state based on statistical associating fluid theory. In a Diesel engine the liquid fuel is injected into supercritical air. After the injection, the Diesel is heated over its critical temperature reaching a supercritical state. Modelling real-fluid effects is critical in order to properly characterize the air/fuel mixing in the combustion chamber. By using the PC-SAFT EoS (Perturbed Chain Statistical Association Fluid Theory Equation of State) real fluids effects can be taken into account in a CFD simulation. The PC-SAFT EoS shows best results than cubic EoS computing liquid density, compressibility, speed of sound, vapor pressures and density derivatives. Unlike cubic EoS, this model accounts for the shape and size of the molecules. Gas, liquid, supercritical and vapor-liquid equilibrium states can be simulated. PT FLASH (Isothermal Multiphase Flash Calculation) is applied to compute the phase diagram used by the code. Shock tube problems were conducted in a wide range of pressures and densities using n-dodecane to show the capability of the developed algorithm. The results were compared with the solution of an exact Riemann solver which has the PC-SAFT EoS implemented showing a high degree of agreement. In addition, a two-dimensional simulation of supercritical nitrogen jet mixing was carried out to checkthe multidimensional capability of the code.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5000
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Ricci, D., F. Battista, M. Ferraiuolo, V. Salvatore, and M. Fragiacomo. "Methane Transcritical Behavior in the Cooling System of the HYPROB-BREAD LOX/LCH4 Demonstrator Rocket Engine." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51554.
Анотація:
The HYPROB Program, developed by the Italian Aerospace Research Centre, has the aim of increasing the Italian system design and manufacturing capabilities on liquid oxygen-hydrocarbon rocket engines; the most important activity is represented by the development and testing of a ground engine demonstrator of three tons thrust based on methane as propellant. The demonstrator baseline concept is featured by 18 injectors and is regeneratively cooled by using liquid methane. The cooling system has a counter-flow architecture and is made by 96 axial channels; methane enters the channels in the nozzle region in supercritical liquid condition, is heated by the combustion gases along the cooling jacket and then is injected into the combustion chamber as a supercritical gas. The goal of the present paper is to describe the activities supporting the cooling jacket design, aiming at identifying the optimal configuration of the cooling channels. 3-D CFD analyses have been performed on different cooling channel arrangements, in terms of channel height and rib width. Moreover, simulations described the thermo-fluid dynamic behavior of methane by means of NIST real gas modeling and they were necessary to give the proper input to the thermo-structural analyses in order to verify the most critical sections of the cooling jacket.
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Keding, Marcus, Piotr Dudzinski, Alexander Reissner, Stefan Hummel, and Martin Tajmar. "Improved µ-Scale Turbine Expander for Energy Recovery." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22296.
Анотація:
Micro power converters for energy recovery are increasingly important for a number of future applications. The Austrian Institute of Technology (AIT) is presently developing an innovative μ-scale turbine expander for work recovery in transcritical CO2 heat pumps. The main drawback of a lower COP (coefficient of performance) of transcritical CO2 heat pumps compared to conventional heat pump systems can be compensated by utilizing the pressure difference between the high pressure and low pressure part of the pump for work recovery. Work recovery can be realized by substituting the expansion valve between the high and low pressure side by a Pelton turbine with specific two phase flow turbine blades. In order to increase the power output, the generator was integrated into the turbine to reduce the friction losses and hence increase the overall efficiency. An important aspect is that the generator is directly connected with the high pressure part of the turbine. One part of the project is the optimization of the turbine geometry via simulation tools. The paper will give an overview about our microturbine development as well as a comparison of the power output of each turbine generation. Furthermore the present paper discusses a concept that utilizes our microturbine together with a micro combustion module that enables a micro power generator with very high power-to-weight ratios based on green fuels.
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Riedmann, H., D. Banuti, B. Ivancic, O. Knab, and K. Hannemann. "Modeling of H2/O2 single-element rocket thrust chamber combustion at sub- and supercritical pressures with different computational fluid dynamics tools." In Progress in Propulsion Physics – Volume 11. Les Ulis, France: EDP Sciences, 2019. http://dx.doi.org/10.1051/eucass/201911247.
Анотація:
This paper derives from the cooperation between DLR and Airbus DS within the work package “CFD Modeling of Combustion Chamber Processes” conducted in the frame of the Propulsion 2020 project. In a joint strategy, DLR Göttingen and Airbus DS Ottobrunn have identified a number of test cases with gradually growing complexity where adequate test data are available for proper successive validation of the computational fluid dynamics (CFD) tools to be used in an industrial environment. This work highlights the simulation results for the Mascotte A-10 and A-60 test cases as presented at the 2nd International Workshop on Rocket Combustion Modeling in Lampoldshausen 2001 by ONERA and SNECMA [1]. These two test cases are characterized by different chamber pressures (10 and 60 bar) and, consequently, by oxygen injection conditions which are subcritical in one case and transcritical in the other case. The test cases are treated with three different CFD codes: the DLR TAU Code (only A-60 case), the Airbus DS in-house tool Rocflam3, and the commercial CFD tool ANSYS CFX incorporating several modeling extensions by Airbus DS. To the knowledge of the authors, this paper is the first one which covers both the A-10 and the A-60 test cases.
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Sirignano, William A., and Albert Jorda Juanos. "Analytical / Computational Approach to Liquid Spray Heating and Vaporization at Supercritical Pressures." In ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems. Valencia: Universitat Politècnica València, 2017. http://dx.doi.org/10.4995/ilass2017.2017.4615.
Анотація:
Our findings from two areas of background research will define an approach to the study of liquid spray heating andvaporization in gases at supercritical pressure: (i) vaporizing droplets at supercritical pressure and (ii) supercritical combustion in simple configurations, e.g., counterflow. The a priori conclusion that only one phase exists at super- critical pressure is based on false “lore” and not physical law. The question about the phases must be left open until the analysis reaches a conclusion; a proper approach will be defined. Proper equations of state for density and en- thalpy and the determination of phase equilibrium, liquid composition due to dissolved gas, energy of vaporization, surface tension, and transport properties for high pressures will be discussed. The case of an isolated droplet will be reviewed and origin of the transcritical concept will be explained. A counterflow spray configuration at pressures above the liquid critical pressure will be analyzed. The concept of shifting phase equilibrium will be applied as the droplets in the spray heat. Hydrocarbon liquids and oxidizing gaseous environments will be studied. Differences between real fluids and ideal fluids at high pressures will be emphasized. Proper rules for gaseous mixtures andliquid solutions will be discussed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4615