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Wang J.,Xian Jiaotong University | Yan Z.,Xian Jiaotong University | Wang M.,Xian Jiaotong University | Ma S.,Xian Jiaotong University | And 2 more authors.
Energy | Year: 2013

Organic Rankine cycle can effectively recover the low grade heat source due to its distinctive thermodynamic performance. Based on the thermodynamic mathematical models of an ORC (organic Rankine cycle) system, this study examines the effects of key thermodynamic design parameters, including turbine inlet pressure, turbine inlet temperature, pinch temperature difference and approach temperature difference in (heat recovery vapor generator) HRVG, on the net power output and surface areas of both the HRVG and the condenser using R123, R245fa and isobutane. Considering the economic factor for the system optimization design, a ratio of net power output to total heat transfer area is selected as the performance evaluation criterion to predict the system performance from the view of both thermodynamics and economics. Genetic algorithm is employed to optimize the system performance. The results show that turbine inlet pressure, turbine inlet temperature, pinch temperature difference and approach temperature difference have significant effects on the net power output and surface areas of both the HRVG and the condenser. By parametric optimization, the ORC system with isobutane has the best system performance than that with R123 or R245fa. The optimum pinch temperature difference and approach temperature difference are generally located at upper boundary over their parametric design ranges. © 2012 Elsevier Ltd.


Wang J.,Xian Jiaotong University | Sun Z.,Xian Jiaotong University | Dai Y.,Xian Jiaotong University | Ma S.,Dongfang Turbine Co.
Applied Energy | Year: 2010

Supercritical CO2 power cycle shows a high potential to recover low-grade waste heat due to its better temperature glide matching between heat source and working fluid in the heat recovery vapor generator (HRVG). Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the cycle performance and exergy destruction in each component. The thermodynamic parameters of the supercritical CO2 power cycle is optimized with exergy efficiency as an objective function by means of genetic algorithm (GA) under the given waste heat condition. An artificial neural network (ANN) with the multi-layer feed-forward network type and back-propagation training is used to achieve parametric optimization design rapidly. It is shown that the key thermodynamic parameters, such as turbine inlet pressure, turbine inlet temperature and environment temperature have significant effects on the performance of the supercritical CO2 power cycle and exergy destruction in each component. It is also shown that the optimum thermodynamic parameters of supercritical CO2 power cycle can be predicted with good accuracy using artificial neural network under variable waste heat conditions. © 2009 Elsevier Ltd. All rights reserved.


Ma D.,Dongfang Turbine Co. | Ma D.,State Key Laboratory of Long Life High Temperature Materials
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2015

Based on the analysis of solidification processing in complex turbine blades, a new idea of 3- dimensional and precise control of single crystal (SC) growth was proposed. A series of new techniques were presented, exhibiting the new development in the production of SC blades of superalloys. The heat conductor (HC) technique was developed to minimize the hot barrier effect which hindered the lateral SC growth. This method promotes the successful transition of SC growth from the blade body into the platform extremity prior to the nucleation of stray grains. To achieve symmetric thermal conditions for solidifying the SC blades, the PHC (parallel heating and cooling) system has been employed. With this technique, both sides of a shell mold can be both symmetrically heated in the heating zone as well as cooled in the cooling zone. The negative shadow effect in the current Bridgman process and the related defects are hence removed. With the H&D (dipping and heaving) technique using thin shell, the main problems of the Bridgman process, such as the ineffective radiative heat exchange and the large thermal resistance in thick ceramic molds, can be effectively resolved. This technique enables the establishment of a high temperature gradient at solidification front. By combining targeted cooling and heating technique, a 3-dimensional control of SC growth in large components can be achieved. © All right reserved.


Liu H.,Xian Jiaotong University | Liu Y.,Xian Jiaotong University | Wang W.,Dongfang Turbine Co.
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2011

Using a rough body-rigid plane contact model, the accuracy of the general normal stiffness equivalent method of contact interface is analyzed under both elastic and elastic-plastic material. The results show that there is a significant error while dealing with elastic-plastic materials, and the essential reason is that the general equivalent method cannot consider the plastic effect of materials completely. By making the elastic-plastic contact system equivalent to an interfacial contact layer and a non-interface block, the original system can be accurately equivalent, because the contact layer includes all the plastic effect. However, introducing the contact layer with a certain thickness can bring the problem of enlarging more elements and inconvenience for practical engineering. In order to overcome the weakness, a new equivalent method of normal contact stiffness is presented by separating the normal stiffness of the contact layer further. Using this method, the contact system is equivalent to non-thickness homogeneous spring and an elastic-plastic block with original size. In this way, the original system can be accurately equivalent, and the plastic effect of the contact body can be taken into account completely. Furthermore, the new equivalent method has nothing with the thickness of plastic zone, so it is convenient for meshing the original system. The results of typical example show the accuracy and effectiveness of the new method. © 2011 Journal of Mechanical Engineering.


Wang J.,Xian Jiaotong University | Yan Z.,Xian Jiaotong University | Ma S.,Xian Jiaotong University | Ma S.,Dongfang Turbine Co. | Dai Y.,Xian Jiaotong University
International Journal of Hydrogen Energy | Year: 2012

A new integrated power generation system driven by the solid oxide fuel cell (SOFC) is proposed to improve the conversion efficiency of conventional energy by using a Kalina cycle to recover the waste heat of exhaust from the SOFC-GT. The system using methane as main fuel consists an internal reforming SOFC, an after-burner, a gas turbine, preheaters, compressors and a Kalina cycle. The proposed system is simulated based on the developed mathematical models, and the overall system performance has been evaluated by the first and second law of thermodynamics. Exergy analysis is conducted to indicate the thermodynamic losses in each components. A parametric analysis is also carried out to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that as compressor pressure ratio increases, SOFC electrical efficiency increases and there is an optimal compressor pressure ratio to reach the maximum overall electrical efficiency and exergy efficiency. It is also found that SOFC electrical efficiency, overall electrical efficiency and exergy efficiency can be improved by increasing air flow rate. Also, the largest exergy destruction occurs in the SOFC followed by the after-burner, the waste heat boiler, the gas turbine. The compressor pressure ratio and air flow rate have significant effects on the exergy destruction in some main components of system. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

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