Leakage flow characteristic of radial inflow turbine adopted in CAES system: Review on progress

2021 ◽  
pp. 095440622110276
Author(s):  
Xing Wang ◽  
Xuehui Zhang ◽  
Yangli Zhu ◽  
Ziyi Shao ◽  
Wen Li ◽  
...  
Keyword(s):  
Energy Storage ◽  
Power Output ◽  
Flow Characteristic ◽  
Tip Clearance ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Operation Condition ◽  
Loss Mechanism ◽  
Flow Loss ◽  
Radial Inflow Turbine

Compressed Air Energy Storage (CAES) System is an important power output component of the energy storage technology. Radial inflow turbine is the main power output device in CAES system, it is operated at extraordinary operation condition (inlet pressure ≥ 75 bar and inlet temperature < 500 K) which is different from gas turbine and other turbomachinery. Therefore, clearance existing in the CAES radial inflow turbine will result in special leakage flow characteristic and higher flow loss, which decreases the aerodynamic performance and the economic efficiency of the CAES system. However, most of researches for CAES radial inflow turbine mainly focus on the performance prediction of CAES system with one-dimensional model, the detailed leakage flow loss mechanism based on three-dimensional analysis, which significantly influences the flow structure and efficiency, are still needed to be further conducted. In present study, the progress on leakage flow characteristic in the CAES radial inflow turbine is reviewed. The effects of tip clearance, case-shroud clearance and back cavity of rotors are summarized, the leakage flow mechanism and loss reduction method are also analyzed and discussed. Suggestions for the future work on leakage flow of CAES radial inflow turbine are also proposed. The present review can provide a guide for new design and optimization of the radial inflow turbine adopted in CAES system.

Investigation Into the Effects of Hub Rotation on the Hub Leakage Flow of Cantilever Stator in a Transonic Axial Compressor

2020 ◽  
Author(s):  
Botao Zhang ◽  
Bo Liu ◽  
Xin Sun ◽  
Hang Zhao
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Leading Edge ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Root ◽  
Flow Loss ◽  
Total Pressure Ratio

Abstract In order to explore the similarities and differences between the flow fields of cantilever stator and idealized compressor cascade with tip clearance, and to extend the cascade leakage model to compressors, the influence of stator hub rotation to represent cascade and cantilever stator on hub leakage flow was numerically studied. On this basis, the control strategy and mechanism of blade root suction were discussed. The results show that there is no obvious influence on stall margin of the compressor whether the stator hub is rotating or stationary. For rotating stator hub, the overall efficiency is decreased while the total pressure ratio is increased. At peak efficiency point and near stall point, the efficiency is reduced by about 0.43% and 0.34% individually, while the total pressure ratio is enlarged by about 0.23% and 0.27%, respectively. The gap leakage flow is promoted due to stator hub rotation, and the structure of the leakage vortex is weakened obviously. In addition, the hub leakage flow originating from the blade leading edge of rotating hub may contribute to double leakage near the trailing edge of the adjacent blade. However, the leakage flow directly out of the blade passage with stationary stator hub. The stator root loading and strength of the leakage flow increase with the rotation of the hub, and the leakage vortex is further away from the suction surface of the blade and is stretched to an ellipse closer to the endwall under the shear action. The rotating hub makes the flow loss near the stator gap increase, while the flow loss in the upper part of the blade root is decreased. Meanwhile, the total pressure ratio in the end area is increased. Blade root suction of cantilever stator can effectively control the hub leakage flow, inhibit the development of hub leakage vortex, and improve the flow capacity of the passage, thereby reducing the flow loss and modifying the flow field in the end zone.

Loss analysis of the shrouded radial-inflow turbine for compressed air energy storage

2020 ◽  
pp. 095765092094784
Author(s):  
Ziyi Shao ◽  
Wen Li ◽  
Aiting Li ◽  
Xing Wang ◽  
Xuehui Zhang ◽  
...  
Keyword(s):  
Energy Storage ◽  
Entropy Generation ◽  
Velocity Ratio ◽  
Compressed Air ◽  
Compressed Air Energy Storage ◽  
Suction Surface ◽  
Loss Mechanism ◽  
Cross Sectional ◽  
Radial Turbine ◽  
Radial Inflow Turbine

The shrouded radial-inflow turbine is widely employed as a power generation device in the compressed air energy storage (CAES) system. The loss mechanism and off-designed performance of the shrouded radial turbine are lesser known hitherto and should be deeply understood. Loss analyses of a shrouded radial turbine are conducted numerically based on the first and second laws of thermodynamics in the current study. The relationship between losses and the secondary flow has been discussed in detail. A high proportion of loss in the rotor and outblock passage is found under off-designed conditions. The secondary vortex cores and wake are the primary sources of energy dissipation, while the entropy generation mainly appears at the edge of secondary vortices. The suction-surface separation expands as the velocity ratio is decreased, making the high entropy generation scope on the cross-sectional plane wider. Reducing the seal clearance and avoiding the low velocity ratio conditions are quite necessary to reduce losses. It is recommended the outlet passage should be designed longer than the length of rotor axial chord for a uniform outflow.

scholarly journals An Experimental Study of Tip Clearance Flow in a Radial Inflow Turbine

1998 ◽  
Author(s):  
R. Dambach ◽  
H. P. Hodson ◽  
I. Huntsman
Keyword(s):  
Tip Clearance ◽  
Leakage Flow ◽  
Hot Wire ◽  
Tip Leakage Flow ◽  
Axial Turbine ◽  
Tip Clearance Flow ◽  
Tip Leakage ◽  
Radial Turbine ◽  
Clearance Flow ◽  
Radial Inflow Turbine

This paper describes an experimental investigation of tip clearance flow in a radial inflow turbine. Flow visualisation and static pressure measurements were performed. These were combined with hot-wire traverses into the tip gap. The experimental data indicates that the tip clearance flow in a radial turbine can be divided into three regions. The first region is located at the rotor inlet, where the influence of relative casing motion dominates the flow over the tip. The second region is located towards midchord, where the effect of relative casing motion is weakened. Finally a third region exists in the exducer, where the effect of relative casing motion becomes small and the leakage flow resembles the tip flow behaviour in an axial turbine. Integration of the velocity profiles showed that there is little tip leakage in the first part of the rotor because of the effect of scraping. It was found that the bulk of tip leakage flow in a radial turbine passes through the exducer. The mass flow rate, measured at four chordwise positions, was compared with a standard axial turbine tip leakage model. The result revealed the need for a model suited to radial turbines. The hot-wire measurements also indicated a higher tip gap loss in the exducer of the radial turbine. This explains why the stage efficiency of a radial inflow turbine is more affected by increasing the radial clearance than by increasing the axial clearance.

Unsteady Analysis on the Effects of Tip Clearance Height on Hot Streak Migration Across Rotor Blade Tip Clearance

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Zhaofang Liu ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotor Blade ◽  
Tip Clearance ◽  
Inlet Temperature ◽  
Leakage Flow ◽  
Blade Tip ◽  
Hot Streak ◽  
Blade Tip Clearance

This paper presents an investigation on the hot streak migration across rotor blade tip clearance in a high pressure gas turbine with different tip clearance heights. The blade geometry is taken from the first stage of GE-E3 turbine engine. Three tip clearances, 1.0%, 1.5%, and 2.5% of the blade span with a flat tip were investigated, respectively, and the uniform and nonuniform inlet temperature profiles were taken as the inlet boundary conditions. A new method for heat transfer coefficient calculation recommended by Maffulli and He has been adopted. By solving the unsteady compressible Reynolds-averaged Navier–Stokes equations, the time dependent solutions were obtained. The results indicate that the large tip clearance intensifies the leakage flow, increases the hot streak migration rate, and aggravates the heat transfer environment on the blade tip. However, the reverse secondary flow dominated by the relative motion of casing is insensitive to the change of tip clearance height. Attributed to the high-speed rotation of rotor blade and the low pressure difference between both sides of blade, a reverse leakage flow zone emerges over blade tip near trailing edge. Because it is possible for heat transfer coefficient distributions to be greatly different from heat flux distributions, it becomes of great concern to combine both of them in consideration of hot streak migration. To eliminate the effects of blade profile variation due to twist along the blade span on the aerothermal performance in tip clearance, the tested rotor (straight) blade and the original rotor (twisted) blade of GE-E3 first stage with the same tip profile are compared in this paper.

Numerical Study on Unsteadiness of Tip Clearance Flow and Performance Prediction of Axial Compressor

2011 ◽  
Author(s):  
Yoojun Hwang ◽  
Shin-Hyoung Kang
Keyword(s):  
Flow Characteristic ◽  
Numerical Study ◽  
Axial Compressor ◽  
Wave Pattern ◽  
Performance Data ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Blade Passage ◽  
Rotating Speed ◽  
Rotating Instability

Numerical calculations were performed to investigate unsteady features of tip clearance leakage flow in an axial compressor. The first stage rotor of a low speed axial compressor with a large tip clearance was examined. It was confirmed that the numerically calculated performance data were in good agreement with the experimentally measured performance data. Using frequency analysis, the flow characteristic near the casing induced by tip clearance leakage flow was found to be not associated with the rotating speed of the rotor. This characteristic is called rotating instability or self-induced unsteadiness. We found that the circumferential length scale of the rotating instability of the compressor was longer than a pitch of a blade passage; therefore, a multi-blade passage was adopted to study the flow structure more precisely. The flow characteristic was described by the frequency, the circumferential length, and the phase velocity, and was changed by operating points toward stall. The behavior of the flow was characterized by circumferentially traveling waves. Hence, the mechanism governing the development of the unsteady feature was further examined in terms of the rotating wave pattern of the pressure distribution. Furthermore, the unsteady feature of the tip clearance leakage flow affected the prediction of compressor performance by altering blockage, flow turning, and loss near the casing.

scholarly journals Flow characteristic of a multistage radial turbine for supercritical compressed air energy storage system

2017 ◽  
Vol 232 (6) ◽  
pp. 622-640 ◽  
Author(s):  
Xing Wang ◽  
Wen Li ◽  
Xuehui Zhang ◽  
Yangli Zhu ◽  
Wei Qin ◽  
...  
Keyword(s):  
Energy Storage ◽  
Storage System ◽  
Energy Storage System ◽  
Ideal Gas ◽  
Tip Clearance ◽  
Compressed Air ◽  
Compressed Air Energy Storage ◽  
Suction Surface ◽  
Flow Loss ◽  
Relative Differences

Compressed air in supercritical compressed air energy storage system expand from supercritical to atmospheric conditions at lower inlet temperature (<500 K) to generate MW scale power. Therefore, a new multistage radial turbine is adopted and the flow characteristic is investigated by numerical simulation. Effects of ideal gas model and tip clearance on the performance and flow field of the multistage turbine are revealed. Results show that ideal gas model can reveal flow pattern under supercritical condition correctly while leading to obvious deviation of isentropic enthalpy drop, entropy, and inlet-to-exit total temperature ratio. Relative differences for mass flow and efficiency are less than 2%, while the relative differences for output power reaches to 9.36%. For shrouded rotor, mixing of working fluid near hub, blade suction surface, and shroud is the main influencing factor of the flow loss in the rotor. For unshrouded rotor, leakage vortex promote mixture of the fluid deriving from the hub, shroud, and suction surface, and causes much higher flow loss in the channel of rotor. The rotors, which have higher blade height variation rate, present higher efficiency reduction when the tip clearance height is increased, which is because the proportion of tip clearance in blade inlet height increases with the increase of average aspect ratio, resulting in the increase of leakage flow at the leading edge of rotor blade. The pressure fluctuation near the tip clearance and efficiency reduction is also increased. The present study provides a reference for further design and optimization of the multistage radial turbines in compressed air energy storage.

Impact of Skin Friction, Tip Clearance and Trailing Edge Losses on Small Scale Cryogenic Axial Turbine Performance

2016 ◽  
Author(s):  
Khalil M. Khalil ◽  
S. Mahmoud ◽  
R. K. Al-Dadah ◽  
Ayad Al Jubori ◽  
K. Rahbar
Keyword(s):  
Surface Roughness ◽  
Energy Storage ◽  
Power Output ◽  
Major Effect ◽  
Tip Clearance ◽  
Small Scale ◽  
Direct Expansion ◽  
Trailing Edge ◽  
Turbine Performance ◽  
And Performance

Cryogenic Energy Storage (CES) technology which uses liquid air/nitrogen as energy carrier has attracted considerable attention recently due to its high exergy density (762kJ/kg) compared to other energy storage technologies. Liquid air/nitrogen occupies about 1/700 of the volume of its gaseous phase making it easier to store and transport. The stored energy can be recovered through a direct expansion process where the expander design and performance have a major effect on the efficiency of the energy conversion process. In this work the effects of surface roughness, tip clearance and trailing edge thickness on the performance of a small scale (tip diameter 40mm, mass flow rate 0.3 kg/s) axial cryogenic turbine have been investigated using mean line 1D analysis and ANSYS CFX 3D modelling where limited data available in the literature. Results showed that stator surface roughness has the highest impact on the turbine performance, where power output and turbine efficiency were significantly reduced as the roughness increased. For example at 20000RPM (design point) with stator roughness value of 0.5mm the efficiency and power output were 87.2% and 1197.7 W while for the same roughness on rotor blade the efficiency and power output were 89.34% and 1198.59 W. Regarding the effect of tip clearance, the efficiency decreases by 2% as the tip clearance increases from 0.35mm to 1mm.

scholarly journals Parametric Performance of Ultra-light Gas Turbine Power Plant for Heavy Lift Multicopters Flight Systems Using Astra - Russian Aviation Engine Optimization Software

2018 ◽  
Vol 220 ◽  
pp. 03011
Author(s):  
T. Aurthur Vimalachandran ◽  
Andrey Yurievich Tkachenko ◽  
Viktor Nikolaevich Rybakov
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Power Output ◽  
Thermal Efficiency ◽  
Parametric Analysis ◽  
Fuel Efficiency ◽  
Inlet Temperature ◽  
Maximum Output ◽  
Operation Condition ◽  
Gas Turbine Power Plant

A detailed parametric analysis was performed on entire performance cycle model of micro gas turbine power plant. The parametric analysis was studied using Russian Software named ASTRA. Evaluation of parameters on both design and operation condition was performed. The parameters focused here are power output, compression work, specific fuel consumption and thermal efficiency. Various stages such as use of Intercooler, Pre-heater and their optimal influence on thermodynamics were performed. The task was to optimize the maximum output in free turbine power by simulating various cycles of compressor pressure ratios for centrifugal compressor, ambient temperature in various altitude; air-fuel mix ratio and turbine inlet temperature. The results are analysed and presented in this article, the Analysis known as on-design analysis. The compressor uses 66% of turbine work output. The research analysis focuses on reducing the use of power output by compressor and maximizes the power output by free turbine. The results could be summarized as increase in gas turbine thermal efficiency does not always improve the gas turbine efficiency. Optimum power increase of up to 3% was improved and improvement in fuel efficiency improved about 4%.

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