scholarly journals Disc Thickness and Spacing Distance Impacts on Flow Characteristics of Multichannel Tesla Turbines

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 44 ◽  
Author(s):  
Wenjiao Qi ◽  
Qinghua Deng ◽  
Yu Jiang ◽  
Qi Yuan ◽  
Zhenping Feng
Keyword(s):  
High Efficiency ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Spacing Distance ◽  
One To One ◽  
The One ◽  
High Level ◽  
Isentropic Efficiency

Tesla turbines are a kind of unconventional bladeless turbines, which utilize the viscosity of working fluid to rotate the rotor and realize energy conversion. They offer an attractive substitution for small and micro conventional bladed turbines due to two major advantages. In this study, the effects of two influential geometrical parameters, disc thickness and disc spacing distance, on the aerodynamic performance and flow characteristics for two kinds of multichannel Tesla turbines (one-to-one turbine and one-to-many turbine) were investigated and analyzed numerically. The results show that, with increasing disc thickness, the isentropic efficiency of the one-to-one turbine decreases a little and that of the one-to-many turbine reduces significantly. For example, for turbine cases with 0.5 mm disc spacing distance, the former drops less than 7% and the latter decreases by about 45% of their original values as disc thickness increases from 1 mm to 2 mm. With increasing disc spacing distance, the isentropic efficiency of both kinds of turbines increases first and then decreases, and an optimal value and a high efficiency range exist to make the isentropic efficiency reach its maximum and maintain at a high level, respectively. The optimal disc spacing distance for the one-to-one turbine is less than that for the one-to-many turbine (0.5 mm and 1 mm, respectively, for turbine cases with disc thickness of 1 mm). To sum up, for designing a multichannel Tesla turbine, the disc spacing distance should be among its high efficiency range, and the determination of disc thickness should be balanced between its impacts on the aerodynamic performance and mechanical stress.

Aerodynamic performance and flow characteristics analysis of Tesla turbines with different nozzle and outlet geometries

2018 ◽  
Vol 233 (3) ◽  
pp. 358-378 ◽  
Author(s):  
Wenjiao Qi ◽  
Qinghua Deng ◽  
Yu Jiang ◽  
Zhenping Feng ◽  
Qi Yuan
Keyword(s):  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Flow Coefficient ◽  
Working Fluid ◽  
Rotating Disc ◽  
Characteristics Analysis ◽  
One To One ◽  
Nozzle Geometries ◽  
The One ◽  
Isentropic Efficiency

The aerodynamic performance and flow characteristics of a multichannel nozzled Tesla turbine were investigated numerically with different nozzle and outlet geometries at different rotational speeds. Two kinds of nozzle geometries were proposed: one nozzle channel to one disc channel (named as one-to-one turbine) and one nozzle channel to several disc channels (named as one-to-many turbine). Simplified radial outlet and real axial outlet geometries of the Tesla turbines were adopted to research the influence of outlet geometries. The results show that compared with the one-to-many turbine, the isentropic efficiency of the one-to-one turbine is much higher; while the flow coefficient is much lower. In addition, in the middle disc channels (DC1 and DC2) of which two walls are rotating disc walls, the flow fields are almost the same, but different from that in the side channel (DC3) of which one wall is a rotating wall and the other one is a stationary casing wall. DC1 and DC2 generate more torque with less working fluid, thus the disc spacing distance of DC3 should be narrower than that of DC1 and DC2. Compared to the one-to-many turbine, the working fluid flowing through DC1 and DC2 of the one-to-one turbine is much less, and the flow path lines are much longer. The results of different turbine outlet geometries show that compared with the turbines with radial outlet, the isentropic efficiency of the one-to-many turbine with axial outlet is a little higher, while that of the one-to-one turbine with axial outlet is lower. This is due to the larger torque on the disc hole walls, despite a lot more total pressure loss in the exhaust vent of the one-to-many turbine. Therefore, the contribution of disc hole walls to torque cannot be neglected in numerical simulations.

scholarly journals Influence of Disc Tip Geometry on the Aerodynamic Performance and Flow Characteristics of Multichannel Tesla Turbines

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 572 ◽  
Author(s):  
Wenjiao Qi ◽  
Qinghua Deng ◽  
Zhinan Chi ◽  
Lehao Hu ◽  
Qi Yuan ◽  
...  
Keyword(s):  
Tangential Velocity ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Small Scale ◽  
Relative Height ◽  
Turbine Efficiency ◽  
One To One ◽  
The One ◽  
Renewable Energy Generation ◽  
Isentropic Efficiency

As a competitive small-scale turbomachinery option, Tesla turbines have wide potential in various fields, such as renewable energy generation systems and small power equipment. This paper investigates the influence of disc tip geometry, including its profile and relative height, on the aerodynamic performance and flow characteristics of one-to-one and one-to-many multichannel Tesla turbines. The results indicate that compared to the turbine with blunt tips, the isentropic efficiency of the one-to-one turbine with sharp tips has a little decrease, which is because the relative tangential velocity gradient near the rotational disc walls decreases a little and additional vortices are generated at the rotor inlet, while that of the one-to-many turbine with sharp tips increases significantly, resulting from an increase in the relative tangential velocity in the disc channels and a decrease in the low Mach number and vortex area; for instance the turbine efficiency for the former relatively decreases by 3.6% and that for the latter increases by 13.5% at 30,000 r/min. In addition, the isentropic efficiency of the one-to-many turbine with sharp tips goes up with increasing relative height due to increasing improvement of flow status, and its increment rate slows down. A circular or elliptic tip performs better with lower relative height and a triangular tip behaves better with higher relative height. To sum up, a blunt disc tip is recommended for the one-to-one turbine, and a sharp disc tip is for the one-to-many turbine. The relative height and tip profile of the one-to-many turbine should be determined according to their effects on turbine performance, manufacturing difficulty and mechanical deformation.

A Parametric Study of Surge and Flow Instabilities in Gas Pipeline Compression Systems: The Effect of Pipe Parameters on Surge Margins

2002 ◽  
Author(s):  
K. Albayrak ◽  
D. Burtaskiray ◽  
O. C. Eralp ◽  
K. M. Akyuzly
Keyword(s):  
Parametric Study ◽  
Gas Flow ◽  
Coupling Effect ◽  
Flow Characteristics ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Pipe Length ◽  
Compression System ◽  
One Dimensional ◽  
Numerical Experimentation

There is a need to understand the effect of coupling of the flow characteristics of a compressor with that of the pipeline and how this coupling effect the stability of the flow in a compression system. This study addresses such a need by carrying out a numerical simulation of the flow in the whole compression system including the compressor, the pipeline, and the other associated flow elements. A nonlinear, one-dimensional mathematical model is adopted for the present study. In this model, the gas flow inside the pipeline is assumed one-dimensional, viscous, and compressible. A parametric study is carried out using the proposed model, with air as the working fluid, to predict the surge margins for a subscale compression system and to study the effect of pipe length and diameter on these margins. Furthermore, the effect of these geometrical parameters on the amplitude and frequency of the flow oscillations are also established by numerical experimentation.

Investigations on Performance of Stirling Engine Regenerator Matrix

2011 ◽  
Author(s):  
D. J. Shendage ◽  
S. B. Kedare ◽  
S. L. Bapat
Keyword(s):  
Pressure Drop ◽  
Penetration Depth ◽  
High Efficiency ◽  
Stirling Engine ◽  
Operating Conditions ◽  
Dead Volume ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Wire Radius ◽  
Thermal Penetration Depth

Stirling engine technology has attracted attention due to recent environmental and energy problems. The regenerator is the main component in high efficiency Stirling engines. A suitable regenerator must be designed for each Stirling machine to provide high performance. The aim of the present work is to find a feasible number of screens in regenerator by taking into account the pressure drop, dead volume, the thermal penetration depth and geometry of regenerator. The second order cyclic analysis with realistic assumptions is carried out for a single cylinder, beta Stirling engine with rhombic drive for predecided operating conditions, such as pressure of 30 bar, hot side temperature of 750 K, speed of 1440 rpm and hydrogen as the working fluid. It is intended to design and develop the Stirling engine with capacity ≥ 1.5 kWe and the efficiency of drive mechanism and alternator is assumed as 85% each. Miyabe’s and Martini’s approaches are used to simulate regenerator performance considering non-sinusoidal motion of displacer and piston. The results reveal that the flow loss increases remarkably to attain higher value of regenerator effectiveness. However, increase in the speed results into an increase in the mass flow rate of the working fluid. It is observed that regenerator effectiveness decreases only marginally over the range of speeds considered. It is also ensured for selected regenerator screen that the thermal penetration depth (239 μm) should be greater than wire radius of mesh (20.5 μm). For present set of operating and geometrical parameters, length of regenerator is fixed as 22 mm which gives regenerator effectiveness as 0.965. Further, the practice to fill more screens than the designed number of screens in the regenerator, while assembling is not advantageous. It increases pressure drop which results in reduced power output. These are some of the important conclusions.

Influence of Shroud Seal Dimensions on Aerodynamic Performance of Steam Turbine Stages: Part I — Honeycomb Seal

2016 ◽  
Author(s):  
Xin Yan ◽  
Xiuxiu Chen ◽  
Kun He
Keyword(s):  
Steam Turbine ◽  
Aerodynamic Performance ◽  
Leakage Rate ◽  
Cell Diameter ◽  
Geometrical Parameters ◽  
Minor Effect ◽  
Honeycomb Seal ◽  
Wide Range ◽  
A Minor ◽  
Isentropic Efficiency

Effect of leakage flow in honeycomb shroud seals on the aerodynamic performance of steam turbine stages in the high-pressure cylinder was numerically investigated by using the commercial CFD (Computational Fluid Dynamics) software ANSYS CFX11.0. The geometrical parameters of the honeycomb shroud seal, including the sealing clearance, cell depth and cell diameter, were selected as the research objectives to compute the aerodynamic performance of turbine stages at a wide range of dimensions. The numerical results show that the leakage rate in the shroud honeycomb seal is almost linearly increased with increase of sealing clearance. Correspondingly, the total-total isentropic efficiency of turbine stages decreases as well. As the cell depth increases, the total-total isentropic efficiency of the turbine stages is firstly increased and then almost kept constant, and the leakage rate in the honeycomb shroud seal is firstly decreased and then almost kept constant as well. For different honeycomb cell diameters, the leakage rate and stage efficiency are mainly determined by the flow structures in the honeycomb cells and seal outlet region. The present studies also show that, as the cell diameter increases, the total-total isentropic efficiency increases whereas the leakage rate decreases. Among the studied geometrical parameters (i.e. sealing clearance, cell depth and cell diameter), the variation of sealing clearance has a pronounced influence on the mixing loss in the main flow paths, but the variation of cell diameter has less effect on the aerodynamic performance of the turbine stages than that of sealing clearance. If the cell depth is not very small, the variation of cell-depth has a minor effect on the aerodynamic performance in the turbine stages.

Non-Axisymmetric Turbine Endwall Aerodynamic Optimization Design: Part II — Turbine Stage Design and Unsteady Flow Characteristics Analysis

2014 ◽  
Author(s):  
Hao Sun ◽  
Liming Song ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Optimization Design ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Turbine Stage ◽  
Aerodynamic Optimization ◽  
Flow Losses ◽  
Unsteady Interaction ◽  
Isentropic Efficiency

Aerodynamic optimization design and experimental validation for the non-axisymmetric endwall profiles of the turbine cascade have been completed in the part I of this research work. Non-axisymmetric endwall profile optimization design of the turbine stage and corresponding steady and unsteady flow characteristics were presented in the part II. Aerodynamic optimization design for the non-axisymmetric endwall profile of the turbine stage was conducted when the maximization of the total-total isentropic efficiency was set as the design objective with constraint on the mass flow rate. The aerodynamic performance of the designed turbine stage was evaluated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions. The non-axisymmetric endwall profiles of the stator hub and shroud as well as the rotor hub in the turbine stage were optimized using developed endwall profile method in the part I. A total of 15 design variables were employed in the optimization for the stator and rotor endwalls. The global optimization method of the adaptive rang differential evolution algorithm was used to search the optimal non-axisymmetric endwall profile. The total-total isentropic efficiency of the turbine stage with the optimized non-axisymmetric endwall profile increases 0.26% by comparison of the referenced axisymmetric endwall design when the effects of the rotor tip clearance were also considered. The secondary flow losses of the stator and rotor were significantly reduced in the optimized non-axisymmetric endwall stage, as well as the tip leakage flow losses. In addition, the unsteady aerodynamic performance of the turbine stage with the optimized non-axisymmetric endwall profile and referenced axisymmetric endwall were numerically investigated and compared. The numerical results indicate that the fluctuating velocity in the rotor blade passage of the optimized non-axisymmetric endwall stage significantly decreases since the stator wake and secondary flow losses are reduced. Thus, the intensity of the unsteady interaction between the stator upstream flow and the flow in the rotor passage decreases. The time-averaged results indicated that the aerodynamic efficiency and output power of the turbine stage with the optimized non-axisymmetric endwall profile are higher than that of the referenced axisymmetric endwall stage. Meanwhile, the transient results at different time steps show that the periodic fluctuating amplitude of the efficiency and power of the optimized non-axisymmetric endwall stage were smaller than that of the referenced axisymmetric endwall stage due to the weaker stator/rotor unsteady interaction effects.

Influence of Rim Run-Out on the Nonuniformity of Tire-Wheel Assemblies

1994 ◽  
Vol 22 (2) ◽  
pp. 99-120 ◽  
Author(s):  
T. B. Rhyne ◽  
R. Gall ◽  
L. Y. Chang
Keyword(s):  
Finite Element ◽  
Radial Force ◽  
Membrane Model ◽  
Model Experiments ◽  
Force Variation ◽  
One To One ◽  
The One

Abstract An analytical membrane model is used to study how wheel imperfections are converted into radial force variation of the tire-wheel assembly. This model indicates that the radial run-out of the rim generates run-out of the tire-wheel assembly at slightly less than the one to one ratio that was expected. Lateral run-out of the rim is found to generate radial run-out of the tire-wheel assembly at a ratio that is dependent on the tire design and the wheel width. Finite element studies of a production tire validate and quantify the results of the membrane model. Experiments using a specially constructed precision wheel demonstrate the behavior predicted by the models. Finally, a population of production tires and wheels show that the lateral run-out of the rims contribute a significant portion to the assembly radial force variation. These findings might be used to improve match-mounting results by taking lateral rim run-out into account.

Relations between carbon removal rates, biofilm size and density of a novel anaerobic reactor: the inverse turbulent bed

2000 ◽  
Vol 41 (4-5) ◽  
pp. 253-260 ◽  
Author(s):  
P. Buffière ◽  
R. Moletta
Keyword(s):  
Removal Rate ◽  
Removal Rates ◽  
Carbon Removal ◽  
Biofilm Growth ◽  
Loading Rates ◽  
Biomass Activity ◽  
High Turbulence ◽  
The One ◽  
High Level ◽  
Very High

An anaerobic inverse turbulent bed, in which the biogas only ensures fluidisation of floating carrier particles, was investigated for carbon removal kinetics and for biofilm growth and detachment. The range of operation of the reactor was kept within 5 and 30 kgCOD· m−3· d−1, with Hydraulic Retention Times between 0.28 and 1 day. The carbon removal efficiency remained between 70 and 85%. Biofilm size were rather low (between 5 and 30 μm) while biofilm density reached very high values (over 80 kgVS· m−3). The biofilm size and density varied with increasing carbon removal rates with opposite trends; as biofilm size increases, its density decreases. On the one hand, biomass activity within the reactor was kept at a high level, (between 0.23 and 0.75 kgTOC· kgVS· d−1, i.e. between 0.6 and 1.85 kgCOD·kgVS · d−1).This result indicates that high turbulence and shear may favour growth of thin, dense and active biofilms. It is thus an interesting tool for biomass control. On the other hand, volatile solid detachment increases quasi linearly with carbon removal rate and the total amount of solid in the reactor levels off at high OLR. This means that detachment could be a limit of the process at higher organic loading rates.

Effects of Varying Geometrical Parameters on Boiling From Microfabricated Enhanced Structures

2003 ◽  
Vol 125 (1) ◽  
pp. 103-109 ◽  
Author(s):  
C. Ramaswamy ◽  
Y. Joshi ◽  
W. Nakayama ◽  
W. B. Johnson
Keyword(s):  
Heat Dissipation ◽  
Layer Structure ◽  
Single Layer ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Small Range ◽  
Two Phase ◽  
Wall Superheat

The current study involves two-phase cooling from enhanced structures whose dimensions have been changed systematically using microfabrication techniques. The aim is to optimize the dimensions to maximize the heat transfer. The enhanced structure used in this study consists of a stacked network of interconnecting channels making it highly porous. The effect of varying the pore size, pitch and height on the boiling performance was studied, with fluorocarbon FC-72 as the working fluid. While most of the previous studies on the mechanism of enhanced nucleate boiling have focused on a small range of wall superheats (0–4 K), the present study covers a wider range (as high as 30 K). A larger pore and smaller pitch resulted in higher heat dissipation at all heat fluxes. The effect of stacking multiple layers showed a proportional increase in heat dissipation (with additional layers) in a certain range of wall superheat values only. In the wall superheat range 8–13 K, no appreciable difference was observed between a single layer structure and a three layer structure. A fin effect combined with change in the boiling phenomenon within the sub-surface layers is proposed to explain this effect.

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