This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine. Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are define...This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine. Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are defined. All losses within the hydro turbine are divided into four types and the loss coefficients are defined accordingly. Expressions or characteristic descriptions of these losses as well as the calibration method of the loss coefficients are presented. Furthermore,the torque model of the hydro turbine where the inner energy loss takes place is established. The developed model has been used to calculate the power loss due to the mechanical friction generated by the units’ rotation to solve the difficulty of measurements of the mechanical friction loss in the hydro turbine. The definition of the impact loss explains the phenomenon that the loss of no-load is greater than that of the rated operation. A set of conversion coefficients are defined using the characteristic parameters at the rated operation,which are used to transform the parameters in the torque model into those that are easily measured. Therefore,the expression of the hydro turbine power is converted into a function that has the main servomotor displacement as its single variable. This makes the proposed model be convenient to use. Finally,the proposed model and methods are calibrated and verified using the measured data of a hydropower plant. Good agreement between the modeled results and the measurements indicates that the proposed model can represent the inner energy loss characteristics of the hydro turbine.展开更多
Single-phase and gas-liquid two-phase pressure drops caused by a sudden con-traction in microtubes were experimentally investigated at room temperature and atmospheric pressure,using nitrogen and water. The experiment...Single-phase and gas-liquid two-phase pressure drops caused by a sudden con-traction in microtubes were experimentally investigated at room temperature and atmospheric pressure,using nitrogen and water. The experimental results on pressure drop with a novel measurement method,the tiny gaps on the tubes,were used to characterize the sudden contraction pressure drop for tube diameters from 850 to 330 μm. The ranges of the gas and liquid superficial velocity were 2.55―322.08 and 0.98―9.78 m/s in the smaller tube respectively. In single-phase flow experiments,the contraction loss coefficients were larger than the experimental results from conventional tubes in the laminar flow. While in the turbulent flow,the contraction loss coefficients were slightly smaller than those from conventional tubes and predicted well by Kc=0.5×(1-σ2)0.75. In two-phase flow experiments,the slip flow model with a velocity slip ratio S=(ρL/ρG)1/3 showed a good prediction that reveals the occurrence of velocity slip. An empirical correlation for two-phase flow pressure drops caused by the sudden contraction was developed based on the proposed contraction loss coefficients correlation for single-phase flow and Mar-tinelli factor.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.50839003,50949037)the Natural Science Foundation of Yunnan Province(Grant No.2008GA027)partly by the Talent Training Foundation of Kunming University of Science and Technology(Grant No.KKZ3200906019)&University of Aberdeen
文摘This paper presents the result and analysis of the composition of energy loss occurring in the hydro turbine. Two new types of energy losses,namely the hydraulic loss in the flow channel and the impact loss,are defined. All losses within the hydro turbine are divided into four types and the loss coefficients are defined accordingly. Expressions or characteristic descriptions of these losses as well as the calibration method of the loss coefficients are presented. Furthermore,the torque model of the hydro turbine where the inner energy loss takes place is established. The developed model has been used to calculate the power loss due to the mechanical friction generated by the units’ rotation to solve the difficulty of measurements of the mechanical friction loss in the hydro turbine. The definition of the impact loss explains the phenomenon that the loss of no-load is greater than that of the rated operation. A set of conversion coefficients are defined using the characteristic parameters at the rated operation,which are used to transform the parameters in the torque model into those that are easily measured. Therefore,the expression of the hydro turbine power is converted into a function that has the main servomotor displacement as its single variable. This makes the proposed model be convenient to use. Finally,the proposed model and methods are calibrated and verified using the measured data of a hydropower plant. Good agreement between the modeled results and the measurements indicates that the proposed model can represent the inner energy loss characteristics of the hydro turbine.
基金the National Key Basic Research Program (Grant No. G2000026300)Beijing Open Fund
文摘Single-phase and gas-liquid two-phase pressure drops caused by a sudden con-traction in microtubes were experimentally investigated at room temperature and atmospheric pressure,using nitrogen and water. The experimental results on pressure drop with a novel measurement method,the tiny gaps on the tubes,were used to characterize the sudden contraction pressure drop for tube diameters from 850 to 330 μm. The ranges of the gas and liquid superficial velocity were 2.55―322.08 and 0.98―9.78 m/s in the smaller tube respectively. In single-phase flow experiments,the contraction loss coefficients were larger than the experimental results from conventional tubes in the laminar flow. While in the turbulent flow,the contraction loss coefficients were slightly smaller than those from conventional tubes and predicted well by Kc=0.5×(1-σ2)0.75. In two-phase flow experiments,the slip flow model with a velocity slip ratio S=(ρL/ρG)1/3 showed a good prediction that reveals the occurrence of velocity slip. An empirical correlation for two-phase flow pressure drops caused by the sudden contraction was developed based on the proposed contraction loss coefficients correlation for single-phase flow and Mar-tinelli factor.
