Reliability design method for steam turbine bladesShi, Jinyuan
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0073-7
Abstract Based on theories of probability and statistics, and taking static stresses, dynamic stresses, endurance strength, safety ratios, vibration frequencies and exciting force frequencies of blades as random variables, a reliability design method for steam turbine blades is presented. The purport and calculation method for blade reliability are expounded. The distribution parameters of random variables are determined after analysis and numerical calculation of test data. The fatigue strength and the vibration design reliability of turbine blades are determined with the aid of a probabilistic design method and by interference models for stress distribution and strength distribution. Some blade reliability design calculation formulas for a dynamic stress design method, a safety ratio design method for fatigue strength, and a vibration reliability design method for the first and second types of tuned blades and a packet of blades on a disk connected closely, are given together with some practical examples. With these methods, the design reliability of steam turbine blades can be guaranteed in the design stage. This research may provide some scientific basis for reliability design of steam turbine blades.
Optimization of Venturi tube design for pipeline pulverized coal flow measurementsWu, Zhansong;Xie, Fei
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0072-8
Abstract A Venturi flow meter was designed to accurately measure the mass flow rate of pulverized coal in power plant pipelines. Numerical simulations of the dilute turbulent gas-solid two-phase flow in a horizontal Venturi tube were used to study the effects of Venturi tube geometry on the pressure distribution in the mixture. The results show that Venturi tube geometry strongly influences the metering of the dilute gas-particle two-phase flow. The geometry can be optimized to improve the precision of the measurement and ensure stable measurements. Furthermore, the geometries of three types of Venturi tubes were optimized for an experimental study of pulverized coal mass flow rate measurements.
Sensitivity analysis and numerical experiments on transient test of compact heat exchanger surfacesRen, Hesheng;Lai, Lingjun;Cui, Yongzheng
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0079-1
Abstract A single-blow transient testing technique considering the effect of longitudinal heat conduction is suggested for determining the average convection heat transfer coefficient of compact heat exchanger surface. By matching the measured outlet fluid temperature variation with similar theoretical curves, the dimensionless longitudinal conduction parameter λ1, the time constant of the inlet fluid temperature τ+, and the number of heat transfer units N tu can be determined simultaneously using the Levenberg-Marquardt nonlinear parameter estimation method. Both sensitivity analysis and numerical experiments with simulated measurements containing random errors show that the method in the present investigation provides satisfactory accuracy of the estimated parameter N tu, which characterizes the heat transfer performance of compact heat exchanger surfaces.
Optimal r/b ratio of bend channel in centrifugal compressorWen, Suping;Hu, Xiaowen;Zhang, Yong;Wang, Jun;Li, Tingbin
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0084-4
Abstract A numerical investigation on the flow in a bend channel by coupling the impellerwith the vaneless diffuser in a centrifugal compressor with different r/b ratios (bend radius r to bend channel width b) is presented. The jet-wake effect of the impeller outlet is considered and flow pattern in the bend channel and the performance of the centrifugal compressor stage are investigated. The results indicate that there is an optimal r/b ratio for increasing the stage efficiency to the highest for a specific compressor stage. The change in r/b ratio significantly affects the flow angle of the bend channel outlet. The prime reason for the total pressure loss in the bend channel is the wall friction in the bend channel.
Computation model for corrosion resistance of nanocrystalline zircaloy-4Zhang, Xiyan;Shi, Minghua;Zhu, Yutao;Liu, Qing;Luan, Baifeng;Huang, Guangjie;Li, Cong;Liu, Nianfu
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0102-6
Abstract A computation model of the corrosion rate versus grain size of nanocrystalline zircaloy-4 was presented. The influence of the second phase on the conductivity of alloy was considered. By this model, the corrosion rate of nanocrystalline zircaloy-4 at different temperature was calculated. The results show that the corrosion rate constant and weight gain of nanocrystalline zircaloy-4 decrease with the decrease of grain size, and that the corrosion weight gain of nanocrystalline zircaloy-4 is less than that of zircaloy-4 of coarse grain. The computational result is coincident with the experimental result.
Effect of inlet box on performance of axial flow fansLi, Jingyin;Tian, Hua;Yuan, Xiaofang
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0087-1
Abstract Numerical investigations on 3D flow fields in an axial flow fan with and without an inlet box have been extensively conducted, focusing on the variation of fan performance caused by the internal flow fields and the velocity evenness at the exit of the inlet box. It is interesting to find that although the inlet box is well designed in accordance with basic design principles, there is a flow separation region in it. Furthermore, this flow separation and the resulting uneven velocity distribution at the exit lead to some decrease in the efficiency and an increase in the total pressure rise of the fan. This research shows that the inlet box needs further improvement and such a check on the flow fields is of value for the design of inlet boxes.
Combustion characteristics of SI engine fueled with methanol-gasoline blends during cold startSong, Ruizhi;Hu, Tiegang;Liu, Shenghua;Liang, Xiaoqiang
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0081-7
Abstract A 3-cylinder port fuel injection (PFI) engine fueled with methanol-gasoline blends was used to study combustion and emission characteristics. Cylinder pressure analysis indicates that engine combustion is improved when methanol is added to gasoline. With the increase of methanol, the flame developing period and the rapid combustion period are shortened, and the indicated mean effective pressure increases during the first 50 cycles. Meanwhile, a novel quasi-instantaneous sampling system was designed to measure engine emissions during cold start and warm-up. The results at 5°C show that unburned hydrocarbon (UHC) and carbon monoxide (CO) decrease remarkably. Hydrocarbon (HC) reduces by 40% and CO by 70% when fueled with M30 (30% methanol in volume). The exhaust gas temperature is about 140°C higher at 200 s after operation compared with that of gasoline.
Analysis of flow and heat transfer characteristics of porous heat-storage wall in greenhouseOuyang, Li;Liu, Wei
2008 "Frontiers in Energy"
doi: 10.1007/s11708-008-0094-2
Abstract The flow and heat transfer characteristics of porous heat-storage wall in greenhouse are studied by using the one-dimensional steady energy two-equation model for saturated porous medium. The results show that the heat exchange between the air and the solid matrix of the porous heat-storage wall depends upon the inlet air velocity, the porosity and the permeability of porous medium, and the thermal conductivity of the solid matrix. Because the incidence of solar radiation on the porous heat-storage wall is not uniform, the new composite porous solar wall with different porosity is proposed to reduce the disadvantageous effect.