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Nan Z.,Beijing Aerospace Propulsion Institute
Proceedings of the International Astronautical Congress, IAC | Year: 2013

Because of its high specific impulse and environmental-friendly feature, LOX/LH2 engine has a special standing in aerospace propulsion domain, and has gained great attention worldwide. Since 1960's, China has been working on the development of LOX/LH2 engine. Developed from nothing, China has broken through a great number of key technologies and accumulated abundant experiences. In 1984, we successfully launched China's first geosynchronous communication satellite using 4 tonne thrust LOX/LH2 engine as the upper stage propulsion of CZ-3 Launch vehicle. Since then we developed 8 tonne thrust YF-75 engine with higher performance as the upper stage engine of CZ-3A launch vehicle. Preparing for the new generation launch vehicle CZ-5, we are developing 9 tonne thrust expander cycle upper stage engine YF-75D and 50 tonne thrust main engine YF-77. Till now we have made some major breakthrough in terms of their design, material, manufacture, and test. In the future, the developing of LOX/LH2 engine with higher thrust is inevitable. Thus, we are now having deep studies of key technologies concerning its system, thrust chamber, turbo pump, valves, etc. Copyright © 2013 by the International Astronautical Federation. All rights reserved. Source


Li X.X.,Beijing Aerospace Propulsion Institute
IOP Conference Series: Earth and Environmental Science | Year: 2012

To improve performance and design of the cryogenic pump, analyze and solve the pump fault, and ensure the reliability of design and operating, it is highly necessary to understand the cryogenic pump temperature profile. Regarding horizontal single cryogenic centrifugal pump as the studied object, the flow field and structural heat transfer is calculated and analyzed. Based on reasonable boundary condition, three dimensional steady state of the pump mesh model is calculated by finite-element method with the software of Fluent, the fluid pressure field and the whole structural temperature profile is obtained. The structural temperature profile by finite-element heat transfer calculation indicates that: in the operating range of the cryogenic pump, the pumping cryogenic liquid is unable to vaporize at the room temperature, and the low temperature area is unable to interfere with the gear case in normal operation. © Published under licence by IOP Publishing Ltd. Source


Zhu Y.,Tsinghua University | Jiang P.,Tsinghua University | Sun J.,Beijing Aerospace Propulsion Institute | Xiong Y.,Tsinghua University
Journal of Thermophysics and Heat Transfer | Year: 2013

Transpiration cooling coupled with combustion was investigated in an H 2/O2 liquid rocket thrust chamber with a transpiration-cooled injector plate.Anumericalmodelwasdevelopedusingthe real gas equationof state.TheH2 andO2 combustion process was modeled by the eddy dissipation concept model, which includes the detailed chemical reaction mechanismsin turbulent flows.The permeability and the inertia coefficient of themetalmesh, porousmedia used for the injector plate were obtained experimentally. The simulation results for the porous plate temperatures and H2 fluxes comparewellwithhot firing experiments, giving reliable predictions of the combustion, flow, andheat transfer processes in the liquid rocket thrust chamber.Themodelwas also used to investigate the effects of the inlet conditions and the plate material on the transpiration cooling. The results showthat locations near the chamberwall and the ignition hole on the plate surface have higher temperatures than other locations. The relatively small thermal conductivity of the porous media is also shown to decrease the plate surface temperature, but increase the thermal stress in the plate. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source


Liu J.,China University of Petroleum - Beijing | Li S.C.,Beijing Aerospace Propulsion Institute | Luo X.,China University of Petroleum - Beijing
Computational and Mathematical Methods in Medicine | Year: 2013

Support vector machine is an effective classification and regression method that uses machine learning theory to maximize the predictive accuracy while avoiding overfitting of data. L2 regularization has been commonly used. If the training dataset contains many noise variables, L1 regularization SVM will provide a better performance. However, both L1 and L2 are not the optimal regularization method when handing a large number of redundant values and only a small amount of data points is useful for machine learning. We have therefore proposed an adaptive learning algorithm using the iterative reweighted p-norm regularization support vector machine for 0 < p ≤ 2. A simulated data set was created to evaluate the algorithm. It was shown that a p value of 0.8 was able to produce better feature selection rate with high accuracy. Four cancer data sets from public data banks were used also for the evaluation. All four evaluations show that the new adaptive algorithm was able to achieve the optimal prediction error using a p value less than L1 norm. Moreover, we observe that the proposed Lp penalty is more robust to noise variables than the L1 and L2 penalties. © 2013 Jianwei Liu et al. Source


Liu Y.-Q.,Tsinghua University | Jiang P.-X.,Tsinghua University | Jin S.-S.,Tsinghua University | Sun J.-G.,Beijing Aerospace Propulsion Institute
International Journal of Heat and Mass Transfer | Year: 2010

The transpiration cooling mechanisms used for thermal protection of a nose cone was investigated experimentally and numerically for various cooling gases. The effects of injection rates, model geometry, inlet temperature and Reynolds number of the main stream were studied for air, nitrogen, argon, carbon dioxide and helium. The experiments used a hot gas wind tunnel with T∞ = 375 K and 425 K and Re∞ = 4630-10,000. The experimental results indicated that even a small amount of coolant injection drastically reduced the heat transfer from the hot gases with the cooling effectiveness increasing with increasing injection rate, although the increases became smaller as the gas injection rate was further increased. The temperature and cooling effectiveness distribution along the transpiration surface of the nose cone model exhibited similar tendencies for all the coolants employed in present experimental research. The temperature decreased from the stagnation point towards the downstream region, then increased because of the non-uniform mass flow distribution of the coolant and thermal conduction from the metal backplane, whereas the cooling effectiveness variation was the reverse. The local cooling effectivenesses and thermal capacities were found to depend on the coolant thermophysical properties. Two-dimensional numerical simulations using the RNG κ- turbulence model for the main stream flow and the Darcy-Brinkman-Forchheimer momentum equations and thermal equilibrium model for the porous zone compared well with the general features in the experiments. © 2010 Elsevier Ltd. All rights reserved. Source

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