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Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The staged combustion cycle provides the highest performance of conventional chemical rocket engines. Turbine power is derived from a separate combustor or preburner which also utilizes the same propellants as the main system. In bipropellant systems, the hot gas is routed through the turbopump turbines to the main injector where it is mixed with the other propellant and is combusted in the main chamber Pump discharge pressures are set by chamber pressure plus pressure losses in the cooling circuit, turbine, injector, valves, and ducting. Thrust chambers are regeneratively cooled. Staged combustion cycle engines developed in the U.S. have utilized a fuel-rich preburner. Several rocket engine systems developed in Russia have utilized an oxidizer-rich preburner. In the former case, the fuel-rich hot gases are mixed with oxidizer in the main chamber. In the latter, oxidizer-rich hot gases are mixed with fuel in the main chamber. The staged combustion cycle utilizes all propellants in the main combustion chamber, which provides maximum performance. A schematic of a simple staged combustion system is given in Figure 197.4.
Extended Eddy-Dissipation Model for Modeling Hydrogen Rocket Combustors
Published in Combustion Science and Technology, 2020
The configuration of the experimental setup corresponds to a staged combustion cycle operating with gaseous oxygen and hydrogen propellants (Pal et al., 2006). The experimental setup consisted of two preburners and a main combustion chamber. The main combustion chamber has a single co-axial injector and is fueled by fuel-rich and oxygen-rich preburner gases. Within this test case, the results of wall heat flux measurements are supposed to be a target of simulations.
Numerical Investigation on Unstable Direct Contact Condensation of Steam in Subcooled Water
Published in Heat Transfer Engineering, 2021
K. N. Jayachandran, Arnab Roy, Parthasarathi Ghosh
Direct contact heat transfer devices have gathered the attention of researchers and industrialists due to the increased efficiency and lower cost associated with them, in comparison with the conventional heat exchangers [1, 2]. In typical emergency cooling and pressure containment systems of nuclear reactors, steam is discharged into a stagnant pool of subcooled water which leads to condensation of steam jets [3]. The steam jets are classified as stable or unstable depending upon (i) steam mass flux and (ii) pool subcooling [4]. Stable jets are usually observed at high steam mass flux (typically sonic and supersonic) and high pool subcooling, whereas unstable jets are seen at low steam mass flux (typically subsonic) and low pool subcooling. Stable jets provide average heat transfer coefficients of about 5 to 10 times higher than the typical unstable jets [5]. Unstable condensation regimes are further sub-divided as chugging and oscillatory bubble regimes. At minimal steam mass fluxes, small amounts of water may enter the steam pipe/nozzle leading to steam chugging regimes [6]. At higher steam mass fluxes (still subsonic), the vapor jets show a periodic oscillatory behavior comprising of the bubble formation, elongation, necking, separation, and collapsing phenomena [5]. The unstable oscillatory condensing jets differ from the stable jets in the fact that the unstable jets after growing to the maximum length exhibit bubble characteristics such as necking and separation, and finally, the detached jets collapse due to condensation [5]. Unstable oscillatory direct contact condensation (DCC) is usually observed at the surplus steam relief process in the operation of pressure containment vessels in boiling water reactors and due to perturbations induced by loss of coolant accidents [4]. It leads to a decline in heat transfer characteristics and generates pressure oscillations, which may affect the structural integrity of the containment [7]. So, there is a need to study the behavior of steam jets under unstable conditions to obtain the operational safety limits of the direct contact condenser. In addition to this, unstable oscillatory DCC is a preferred mode of operation for condensing hot turbine gas (predominantly oxygen with small amounts of combustion products) with liquid oxygen (LOX) in the LOX booster turbopump of a typical staged combustion cycle based rocket engine [8–10]. The selection of unstable DCC in this application is due to the issues of rapid solidification of the combustion products at higher heat transfer coefficients and the pressure drop constraints, associated with the stable DCC regime [11, 12]. This is a special case of DCC of vapor jets in flowing liquid which has been studied by many researchers [12–17].