1,721,035 research outputs found
Flow Field and Heat Transfer Analysis of Oxygen/Methane Liquid Rocket Engine Thrust Chambers
Full text linkThis study is devoted to the characterization and analysis of the flow field and heat transfer in oxygen/methane liquid rocket engines. Attention is focused on the hot gas side of the thrust chamber, where highly energetic flows have to be managed en-
suring the safe operation of the thrust chamber and of the entire engine. Different technological solutions to handle such flows are here investigated by means of CFD numerical simulations. As a compromise between details and computational cost, the attention is focused on capturing the basic phenomena involved which drive the main heat transfer processes, to allow full scale engine analysis as support to the engine
design phase. The simplified approaches are defined, verified and validated against experimental data in different rocket engine conditions, such as film cooled and regeneratively cooled thrust chambers, and expander cycle engine thrust chambers with
heat transfer enhancement devices. Hence, parametric analyses are finally carried out for each configuration. Finally, the simplified approaches are adopted in the thermal analysis of the LM-10 MIRA oxygen/methane expander cycle engine thrust chamber
Procedure di localizzazione per rimozione di outlier in dati laserscanning grigliati
No full textNel seguito viene presentata una metodologia per la identificazione e rimozione di outlier in dati grigliati e i risultati ottenuti su dati laserscanning. Per outlier si intende qui una osservazione isolata che si discosti in maniera sospetta da quelle che la circondano. Il criterio di reiezione può dunque basarsi sul confronto tra questa e il valore che dovrebbe assumere sulla base delle osservazioni circostanti e in particolare quelle comprese in una finestra di dimensioni opportune che scorre sull’intero grigliato. La verifica si esegue sul dato centrale della finestra. Si stima la superficie che meglio interpola le osservazioni via via in esame, escluso il candidato outlier, ai minimi quadrati o in alternativa con una interpolazione alla Wiener o con uno stimatore robusto; quindi si esegue la verifica tramite procedure di inferenza classiche o appositamente costruite. Per l’archiviazione, la gestione, l’analisi e la visualizzazione dei dati in maniera ottimizzata e in un unico ambiente di lavoro si è deciso di ricorrere ad un sistema informativo geografico. Si è scelto di impiegare il sistema GRASS sia perché disponibile in rete gratuitamente, sia perché consente di sviluppare in un linguaggio standard (C) al suo interno il codice necessario alla esecuzione di nuove procedure
Coupled analysis of hot-gas and coolant flows in LOX/methane thrust chambers
No full textThe analysis of the flow-behavior and the heat transfer characteristics in a regeneratively cooled thrust chamber is of paramount importance for the development of a high-performance liquid rocket engine and to guarantee its structural thermal design. The accurate analysis of such a problem can only be obtained by costly experiments or by complex numerical simulations, because of the three-dimensional shape of the cooling channels and of the coupling among evolution in hot-gas flow, coolant flow and wall heat transfer. However, parametric investigations of rocket thrust chambers thermal environment can also be efficiently made by accurate engineering tools. An example of the latter approach is provided in the present study: a computational procedure able to describe the typical hot-gas/wall/coolant environment of liquid rocket engines. This procedure provides a quick and reliable prediction of thrust-chamber wall temperature and heat flux. The coupled analysis is performed by means of an accurate CFD solver of the Reynolds-Averaged Navier-Stokes (RANS) equations for the hot-gas flow and a simplified “quasi-2D” approach, which widely relies on semi-empirical relations, to study the problem of coolant flow and wall structure heat transfer in the cooling channels. Numerical results, relevant to a sample engine fed with oxygen and methane are presented and discussed
Hydrogen storage materials for microthrusters: Basic performance analysis
No full textThe increasing market request for mini and microsatellites has led in the recent years to the development of small propulsion devices referred to as microthrusters. In the realm of microthruster different classifications have been made which help understanding the possible solutions depending on the satellite mass class and on the required thrust level. The present paper addresses thrusters for the class of microsatellites, that is that of satellites of 10100 kg mass. A novel solution is proposed for microthruster which is based on hydrogen storage by chemical bond in hydrogen rich materials. Hydrogen microthrusters are studied resorting to basic rocket science. The results allow one to get a first evaluation of the possible advantages achievable once the proposed materials will be made safely available. © 2012 Elsevier Ltd
Numerical Modeling of Combustion Chamber and Nozzle Flow in HTPB/GOX Hybrid Rocket Motors
No full textNumerical simulations of the flow in a GOX/HTPB hybrid rocket engine are carried out with a Reynolds averaged Navier-Stokes solver including detailed gas surface interaction modeling based on mass and energy balances. Fuel pyrolysis and heterogeneous reactions at the nozzle wall are modeled via finite-rate Arrhenius kinetics. Global mechanisms are considered for the gas-phase chemistry for the combustion of 1,3-butadiene in oxygen. Results show the role of the gas-phase chemistry modeling and surface boundary condition modeling on the solution. The coupling between the mixing and combustion processes in the flowfield and the thermochemical erosion of a graphite nozzle is finally discussed, showing the effect of the temperature and chemical species distributions in the wall region as well as the effects of mixture ratio shifting
Verifica della potenzialità dell'utilizzo di ricevitori GPS a singola frequenza per il controllo: raccolta dati e primi risultati
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A parametric study on the role of near wall chemical reactions in O2/CH4 combustion chamber heat flux evaluation
No full textDealing with oxygen/methane thrust chambers, in case of extremely cooled walls, the near wall recombination plays a non-negligible role in predicting the wall heat transfer from the hot gas to the wall. Assuming as a reference test case the ISP1 oxygen/methane calorimetric thrust chamber in the case without film cooling, a parametric analysis is carried out varying chamber pressure, wall temperature and mixture ratio. In particular, for each test case the numerical solution obtained under the frozen flow assumption is compared to that of reacting flow taking into account the recombination of dissociated species. Comparing the numerical solution
obtained by means of different kinetic mechanisms with increasing detail levels, the results show that the global Jones-Lindstedt kinetic mechanism including recombination reactions is able to capture the recombination heat
increase and gives insight of boundary layer details
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