Rocket

About: Rocket is a research topic. Over the lifetime, 14018 publications have been published within this topic receiving 95852 citations. The topic is also known as: rockets.

Pseudo-boiling and heat transfer deterioration while heating supercritical liquid rocket engine propellants

Abstract: Heating 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.

Compact model based on a lumped parameter approach for the prediction of solid propellant micro-rocket performance

Abstract: The development of a lumped parameter model is described for the performances prediction of a solid propellant micro-scale rocket. A micro-scale rocket consists of a combustion chamber containing the propellant, a converging and a diverging part to accelerate the gas generated by the propellant combustion. The input modelling parameters are the geometrical features of the rockets, the propellant characteristics and the ambient conditions. The output results are the temperature, the pressure, the volumic mass of the gas in the combustion chamber and the resulting thrust as a function of time. To illustrate the computational results, the performances of one micro-rocket investigated at LAAS for micro-propulsion application have been evaluated. The micro-rocket has a throat diameter of 108 μm, a chamber diameter of 850 μm, a chamber length of 1500 mm, a convergent length of 500 μm and a diverging length of 500 μm. The computational results give a chamber pressure of ∼5 bar and a thrust value of ∼3 mN at steady state. To illustrate the capabilities of the model, Section 3.3 discussed two points: • The influence of the heat loss on the thrust force; • The influence of the diverging part design on the thrust force. Results show that the divergent length has an interest and must be optimised when the external pressure is closed to vacuum, whereas the diverging part length has no effect on the thrust results when the external pressure is atmospheric.

Nonlinear Effects in Instability of Solid-Propellant Rocket Motors

Abstract: This paper is in two parts. The first section discusses briefly the various kinds of nonlinear effects associated with instability in solid-propell ant rockets and attempts to provide brief surveys of the ways in which various nonlinear phenomena may manifest themselves. The second section reviews and extends some of the work that has been carried out at the Applied Physics Laboratory on nonlinear instability phenomena arising from erosion. This work has been concerned with effects of erosion on stability and with the waveform of finite amplitude oscillations in motors with cylindrical propellant charges. In this connection, it is found that, especially for axial modes, significant waveform distortion may develop even for relatively small amplitudes of the pressure oscillation and that the wave shape tends to be a rather sensitive function of the time dependent response of the propellant.

Transcritical Liquid Oxygen Droplet Vaporization; Effect on Rocket Combustion Instability

Abstract: The response of a liquid oxygen droplet to oscillatory ambient conditions consistent with liquid-rocket engines over a wide range of frequencies is computed. Two configurations are considered: 1) isolated droplets and 2) droplets in an array. The consequences of nonuniformities introduced in the gas phase by neighboring droplets on the droplet response are evaluated. The potential of gasification as the ratecontrolling mechanism was evaluated through the computation of a response factor derived from the Rayleigh criterion. Computations show that the peak frequency for the computed response factor is mainly correlated to the droplet lifetime and also depends on the type of flow that the droplet is experiencing (with or without reversal). Consequently, droplet secondary atomization, which causes a substantial droplet lifetime reduction, induces a significant (one order of magnitude) shift in the peak frequency. As a result, the frequency of the maximum response factor is too high to correspond to the acoustic frequencies of the typical modes for standard cryogenic rocket engine chambers. Since droplets are likely to undergo secondary atomization in the stripping regime for most of their lifetime in these engines, this phenomenon explains the observed better stability of such engines compared to storable propellant engines. It was also shown that the droplet gasification process, whether undergoing stripping or not, can drive combustion instabilities for the longitudinal mode, under certain simplifying assumptions. The effects of mean pressure and pressure fluctuations on the droplet response were also evaluated.