1,721,031 research outputs found
COUPLED ANALYSIS OF FLOW AND SURFACE ABLATION IN CARBON-CARBON ROCKET NOZZLES, AIAA Paper 2008-3912
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Pseudo-boiling and heat transfer deterioration while heating supercritical liquid rocket engine propellants
No full textHeating of liquid propellants used as the coolant in rocket engines may lead to undesired phenomena such as pseudo-boiling or heat transfer deterioration under specific conditions. This can be an issue for propellants characterized at the same time by relatively low critical pressure and temperature. Light hydrocarbons, as for instance methane, belong to this family. In the present paper, a critical review is made of the main results obtained by Authors and their coworkers for the present application. Focus is on the correlations and trends inferred by their numerical simulations mainly carried out considering methane as the coolant, perhaps the most challenging one
Numerical investigation on the role of thermal radiation in hybrid rocket fuel pyrolysis
No full textThermal radiation is expected to play a non–negligible role on hybrid rocket fuel pyrolysis and overall motor internal ballistics. The way such a role is related to different operating conditions needs to be investigated through dedicated analyses involving computational fluid dynamics and radiative heat transfer simulations. In the present paper a computational fluid dynamics solver with gas–surface interaction capabilities is coupled to a radiative heat transfer code relying on the discrete transfer method. The importance of modeling thermal radiation in the prediction of hybrid rocket internal ballistics is first shown by rebuilding a literature experimental test campaign. A numerical parametric analysis is then carried out allowing a clear identification of the effects of mass flux, chamber pressure and port diameter on both radiative wall heat flux and its relative magnitude with respect to the total wall heating
A sensitivity study on a cfd model for paraffin-based hybrid rockets
No full textA recently validated numerical approach based on Reynolds-averaged Navier-Stokes simulations for paraffin-based hybrid rocket engines is here considered. The model is evaluated in terms of its sensitivity to specific parameters, such as paraffin’s melting temperature and radiation emissivity coefficient, and Schmidt numbers. Moreover, a simulation performed at the average port diameter is confronted with a series of simulations at increasing port diameters. Finally, oxidizer-rich test cases are considered, and the effect of the post-chamber length on the combustion efficiency is investigated
Conjugate heat transfer applied to transitory analysis for rocket engine cooling systems design
No full textThis study investigates the use of an in-house Conjugate Heat Transfer (CHT) numerical solver for the modelling of transient phenomena in liquid rocket engines active cooling systems. Heat transfer considerations place great limitations in the development of rocket engines and transient operative conditions are amongst the most critical. The current lack of models and numerical tools capable of accounting for the complexities of this time-dependent multi-physics problem, results in oversized cooling systems, long development times and increased risk of failure. The fine modelling of all the involved phenomena and their interaction with each other is crucial to achieve a correct prediction of the thermal fluxes and wall temperatures involved. Hence, CHT simulations are the state-of-the-art for this application. The CHT solver proposed in this work utilizes a partitioned coupling strategy where two extensively validated single-physics solvers exchange information through their interfaces at discrete time steps. A simplified version of the RL-10A-3-3A regenerative cooling jacket is considered as reference to test the strengths and the limits of this approach. Both a complete chilldown of the engine and part of the start-up transient have been simulated. The analyses performed show the ability of the solver proposed to deal with transient phenomena where fluid-structure interaction occurs. In addition, they provide a complete overview of the numerical issues related to the partitioned coupling approach. These preliminary results pave the way for further developments aimed at increasing the reliability of the solutions and extending the application field of the software developed
Graphite nozzle erosion trends in paraffin/oxygen hybrid rockets
No full textNozzle erosion predictions are fundamental to increase the technology readiness level of hybrid rocket engines. In this work, Reynolds-averaged Navier–Stokes simulations of the internal ballistics of paraffin/oxygen engines coupled with graphite nozzle ablation are performed under various operating conditions. Additional simulations considering uniform inlet conditions at the postchamber entrance underline the complex interaction between nozzle erosion and the radially nonuniform flowfield originating from incomplete mixing and combustion. Moreover, the favored combustion efficiency resulting from an increase of the postchamber length is evaluated in terms of nozzle erosion in a wide range of oxidizer-to-fuel ratios. Because of the interaction between wall and gas-phase reactions, erosion mass fluxes are observed to monotonically grow with decreasing equivalence ratios
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