Design and Production of Innovative Turbomachinery Components via Topology Optimization and Additive ManufacturingRead the full article
International Journal of Rotating Machinery publishes original research articles as well as review articles on all types of rotating machinery employing gas, vapor, particle, liquid, and their mixtures (including slurry) as the working substances.
Chief Editor, Professor Amano, is based at the University of Wisconsin–Milwaukee and his research concentrates on the enhancement of energy production using wind, biomass, alternate fuels, and fossil energy sources.
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Effect of Rotation Friction Ratio on the Power Extraction Performance of a Passive Rotation VAWT
This paper performs a systematic numerical study to investigate the effect of rotation friction ratio on the power extraction performance of a passive rotation H-type vertical axis wind turbine (H-VAWT). In contrast to the previous literature, the present work does not impose rotation velocity on the turbine, and the rotation friction ratio which reflects the effect of external load characteristics on the turbine is introduced to the governing equation of the turbine. During each iteration, the rotation velocity of the turbine is computed after having determined the aerodynamic torque exerted on the blade of the turbine. This is more consistent with the actual working environment of the H-VAWT. A novel numerical coupling model was developed to simulate the interaction between the fluid and the passive rotation of the H-VAWT; then, the power extraction performance of the turbine with different rotation friction ratio was systematically analyzed. The results demonstrate that the power extraction performance of H-VAWT will be enhanced when the H-VAWT has appropriate rotation friction ratio. It is also found that the flow separation induced by large angle of attack is alleviated essentially if the H-VAWT has appropriate rotation friction ratio, which makes the H-VAWT have better energy extraction performance.
Investigation of Blade Number Effect on Hydraulic Performance of In-Pipe Hydro Savonius Turbine
Level of utilization of clean energy has grown dramatically in recent years due to increased pollution and environmental issues. For instance, the extra potential energy in water supply system is usually wasted, due to its low capacity. Design of a proper turbine has recently been given more attention by researchers to apply this clean energy. In the present paper, a modified Savonius turbine, suitable for use in a 4-inch pipe, is designed. Turbine with two blades is tested in a laboratory rig and also simulated with the FLUENT software. By matching numerical and laboratory results, simulations are expanded and the blades number effect on turbine performance is studied under determined hydraulic conditions. The flow field around the modified Savonius turbine is interpreted by the 3D streamlines and pressure contours. The obtained results indicate that increasing the turbine blade numbers up to 5 and more causes the turbine efficiency first to rise and then to fall, respectively.
Investigation on Lubrication State of Sliding Bearings in Low-Speed Rotor System Subjected to Torque Load
In order to study the influence of torque load on the lubrication and wear of the sliding bearing of the rigid rotor system, the theoretical and experimental researches on the single-span rotor system with low speed were carried out. A special force sensor was used to measure the bearing load under different torque excitations, and the oil film pressure was calculated. The oil film pressure and thickness of sliding bearing under low speed (210r/min) were simulated by combining the lubrication theory. Based on the film thickness ratio theory, the corresponding relationship between the lubrication state and the torque load value was deduced. In addition, the wear rate and abrasive grain morphology of sliding bearing with different torque values were analyzed by means of oil sample preparation to verify this correspondence. The results show that the film thickness ratio has a logarithmic function relationship with the constant torque load, and the film thickness ratio curve can be used to determine the corresponding torque values under different lubrication states. The wear rate under mixed lubrication state increases exponentially with the torque load, and the main wear mechanism is adhesive wear and abrasive wear. The research results have certain guiding significance to the adjustment of the actual running condition of sliding bearing and its life prediction.
Numerical Simulation of the Performance of a Twin Scroll Radial Turbine at Different Operating Conditions
Twin scroll radial turbines are increasingly used for turbocharging applications, to take advantage of the pulsating exhaust gases. In spite of its relevance in turbocharging techniques, scientific literature about CFD applied to twin scroll turbines is limited, especially in case of partial admission. In the present paper a CFD complete model of a twin scroll radial turbine is developed in order to give a contribution to literature in understanding the capabilities of current industrial CFD approaches applied to these difficult cases and to develop performance index that can be used for turbine design optimization purposes. The flow solution is obtained by means of ANSYS CFX ® in a wide range of operating conditions in full and partial admission cases. The total-to-static efficiency and the mass flow parameter (MFP) have been calculated and compared with the experimental database in order to validate the numerical model. The purpose of the developed procedure is also to generate a database for twin scroll turbines useful for future applications. A comparison between performances obtained in different admission conditions was performed. In particular the analysis focused on the characterization of the flow at volute outlet/rotor inlet section. A flow distortion index at rotor inlet was introduced to correlate the turbine performance and the flow nonuniformities generated by the volute. Finally the influence of the backside cavity on the performance parameters is also discussed. The introduction of these new nonuniformity indices is proposed for volute design and optimization procedures.
Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine
To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.
CFD Modelling of a Centrifugal Compressor with Experimental Validation through Radial Diffuser Static Pressure Measurement
This paper compares experimental static pressure measurement with CFD simulation in a centrifugal compressor at 12 points through the diffuser. Three mass flow rates are selected, each for three operating speeds giving nine total operating conditions. The results show that the CFD model generally slightly underpredicts the static pressure value as compared to the experimental results. The discrepancy between experimental and numerical results ranges between -8% and +6% and is fairly consistent for a given operating condition, except for close to the blade trailing edge where the pressure variation is less regular and where the pressure is increasing most rapidly with radial position. In the consistent region, where the pressure gradient is low, the discrepancy is around two percent or less for simulations close to the design operating point. Away from the design operating point the errors increase up to approximately 5%. The simulation results were also used to investigate the effect of the position (from the blade trailing edge) of the impeller-diffuser interface (a characteristic of the frozen rotor simulation approach). Here an optimal position for the interface was found to be 2% of the blade radius. This value gave improved agreement with the experimental result in the initial region of the diffuser up to a distance of approximately 10% of the radius. At greater distances the position of the interface became less important. The results also highlighted a change in the pressure along the spanwise direction close to the tips. A dip in the pressure, which was observed in the experimental results, was only observed in the simulations close to the shroud. Close to the hub the simulation results recorded a small local peak. The simulation approach was then applied to further study the flow characteristics by examining the full-field velocity and pressure contours in the impeller and diffuser regions to identify changes due to the different operating conditions.