Optimisation of a High Pressure Ratio Radial-Inflow Turbine: Coupled CFD-FE Analysis

2015 ◽  
Author(s):  
Mohsen Modir Shanechi ◽  
Mostafa Odabaee ◽  
Kamel Hooman
Keyword(s):  
Power Efficiency ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Von Mises Stress ◽  
Fe Method ◽  
Cfd Simulations ◽  
Turbine Wheel ◽  
Blade Thickness ◽  
Radial Inflow Turbine

The optimisation of a 5.7 air pressure ratio single stage radial-inflow turbine applied in the Sundstrand Power Systems T-100 Multipurpose Small Power Unit (MPSPU) is performed using coupled CFD-FE method. The commercial software ANSYS-Vista RTD along with a built-in module, BladeGen, is used to conduct a meanline design and, consequently, create the 3D geometry of the flow passage. Carefully examining the proposed design against the geometrical and experimental data, ANSYS-TurboGrid is applied to generate computational mesh. CFD simulations are then performed with ANSYS-CFX in which three-dimensional Reynolds-Averaged Navier-Stokes equations are solved subject to appropriate boundary conditions. Conducting the CFD simulations, the pressure and temperature distributions are imported to the ANSYS-FE module. The von Mises stress σv distribution is then calculated taking into account the centrifugal force acting on the turbine wheel. To obtain the optimised geometry, 25 major design points are regenerated where the meridional parameters, tip clearance, and blade thickness distribution are systematically changed. Furthermore, constraints are defined as high aerothermodynamic performance and acceptable vibration with a stress distribution less than yield limit of the turbine material. Results of coupled CFD-FE method show the power, efficiency, stress and deformation. Finally, performance of the optimised radial-inflow turbine indicates enhanced aero-thermodynamics (ηTS and) and structural performance (σv) compared to the MPSPU turbine design.

Effect of Tip Clearance Size on the Ram-Rotor Performance

2014 ◽  
Author(s):  
Ji-ang Han ◽  
Jing-jun Zhong ◽  
Zhen-sheng Pan ◽  
Ling Yang ◽  
Jian Guan
Keyword(s):  
Shock Wave ◽  
Power Systems ◽  
High Performance ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Energy System ◽  
Tip Clearance ◽  
Performance Parameters ◽  
Flow Parameters ◽  
And Performance

The ram-rotor presented by Ramgen Power Systems, Inc. is a new kind of compression system based on shock wave compression technology commonly used in supersonic intakes. Compared to conventional axial and centrifugal compressors, it has a simple and compact configuration, and also has advantages of the higher single stage pressure ratio, small volume and light weight. However, its efficiency should be further improved. Based on its inherent advantages, the ram-rotor can be widely used in small aero-engine, medium and small shipping power system, micro gas turbine employed by distributed energy system and power plant in the future. In this paper, the flow field and performance of a ram-rotor with different tip clearance sizes are simulated numerically by adopting the three dimensional Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulent model at the design condition. The purpose of numerical simulation is to investigate the flow details and performance parameters of the ram-rotor under different tip clearance sizes, including the structure of the shock wave, the size and location of flow separation zone, radial distribution of flow parameters at the outlet of the ram-rotor, the characteristics of tip clearance leakage flow, and so on. It has been found that the performance of the ram-rotor is very sensitive to the tip clearance size. The overall performance parameters of the ram-rotor decrease greatly with the increase of the tip clearance size. So, the selection of suitable tip clearance size is one of the key issues in obtaining a high performance of the ram-rotor in the design process. For the ram-rotor with tip clearance, the reflection structure of the shock wave will be destroyed. The flow loss of tip region will be increased with the increase of the tip clearance size. For the ram-rotor with and without tip clearance, the flow parameters distribution trend along the radial direction at the outlet is different.

Casing Treatment for Desensitization of Compressor Performance and Stability to Tip Clearance

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Mert Cevik ◽  
Huu Duc Vo ◽  
Hong Yu
Keyword(s):  
Pressure Ratio ◽  
Tip Clearance ◽  
Design Strategies ◽  
Tip Leakage Flow ◽  
Cfd Simulations ◽  
Stall Margin ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Compressor Performance ◽  
Nominal Performance

This paper presents the development of a novel casing treatment to reduce compressor performance and stall margin sensitivities to tip clearance increase. A linked research project on blade design strategies for desensitization had discovered two flow features that reduce sensitivity to tip clearance, namely increased incoming meridional momentum in the rotor tip region and reduction/elimination of double tip leakage flow. Double tip leakage flow is the flow that exits one tip clearance and enters the tip clearance of the circumferentially adjacent blade instead of convecting downstream out of the blade passage. A new and practical casing treatment was developed and analyzed through Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) simulations to decrease double tip leakage and reduce or even eliminate performance and stall margin sensitivity to tip clearance size. The casing treatment design consists of sawtooth-shaped circumferential indentations placed on the shroud over the rotor with a depth on the order of the tip clearance size. A detailed analysis of the flow field allowed for the elucidation of the flow mechanism associated with this casing treatment. A computational parametric study gave preliminary design rules for minimizing both performance/stall margin sensitivity to tip clearance and nominal performance loss. An improved casing indentation design was produced for which CFD simulations showed a complete desensitization of pressure ratio and stall margin while reducing efficiency sensitivity significantly for the tip clearance range studied with only a very small penalty in nominal pressure ratio. Further simulations showed that this casing treatment can be combined with desensitizing blade design strategies to further reduce tip sensitivity and reduce/eliminate/reverse nominal performance penalty. Lastly, preliminary CFD simulations on an axial compressor stage indicate that this shallow indentations' casing treatment strategy remains effective in a stage environment.

Open Design of High Pressure Ratio Radial-Inflow Turbine for Academic Validation

2012 ◽  
Author(s):  
Emilie Sauret
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Cfd Simulations ◽  
Commercial Software ◽  
High Pressure Ratio ◽  
Open Set ◽  
Wide Range ◽  
Radial Inflow Turbine ◽  
Radial Turbines

Computational Fluid Dynamics (CFD) simulations are widely used in mechanical engineering. Although achieving a high level of confidence in numerical modelling is of crucial importance in the field of turbomachinery, verification and validation of CFD simulations are very tricky especially for complex flows encountered in radial turbines. Comprehensive studies of radial machines are available in the literature. Unfortunately, none of them include enough detailed geometric data to be properly reproduced and so cannot be considered for academic research and validation purposes. As a consequence, design improvements of such configurations are difficult. Moreover it seems that well-developed analyses of radial turbines are used in commercial software but are not available in the open literature especially at high pressure ratios. It is the purpose of this paper to provide a fully open set of data to reproduce the exact geometry of the high pressure ratio single stage radial-inflow turbine used in the Sundstrand Power Systems T-100 Multipurpose Small Power Unit. First, preliminary one-dimensional meanline design and analysis are performed using the commercial software RITAL from Concepts-NREC in order to establish a complete reference test case available for turbomachinery code validation. The proposed design of the existing turbine is then carefully and successfully checked against the geometrical and experimental data partially published in the literature. Then, three-dimensional Reynolds-Averaged Navier-Stokes simulations are conducted by means of the Axcent-PushButton CFD® CFD software. The effect of the tip clearance gap is investigated in detail for a wide range of operating conditions. The results confirm that the 3D geometry is correcty reproduced. It also reveals that the turbine is shocked while designed to give a high-subsonic flow and highlight he importance of the diffuser.

Aerodynamic Design and Finite Element Modelling of Mixed Aerofoil Wind Turbine Blades

2012 ◽  
Vol 608-609 ◽  
pp. 698-703
Author(s):  
Xin Zi Tang ◽  
Rui Tao Peng ◽  
Xiong Wei Liu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Aerodynamic Characteristics ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Wind Turbine Blades ◽  
Fe Method ◽  
System Service ◽  
Wind Turbine System ◽  
Blade Thickness

Both rotor aerodynamic characteristics and structural performance of the blade are critical to the wind turbine system service life; an accurate loading model of the blade is extraordinary complex due to the complexity of the geometry shape and variety of blade thickness. In this paper, a 10KW fixed-pitch variable-speed wind turbine blade with five different thickness of aerofoil shape along the span of the blade is presented as a case study, main parameters of the wind turbine rotor and the blade aerodynamic geometry shape are determined based on the principles of the blade element momentum (BEM) theory, a specific blade internal structure and layup schedule are designed. Based on the FE method, deflections and strain distributions of the designed blade under extreme wind conditions are numerically predicted. Theoretical and numerical results indicate that aerodynamic characteristics of the designed blade meet the requirement, the tip clearance is sufficient to prevent collision with the tower, and the blade material is linear and safe.

CFD Simulation of a Supercritical Carbon Dioxide Radial-Inflow Turbine, Comparing the Results of Using Real Gas Equation of Estate and Real Gas Property File

2016 ◽  
Vol 846 ◽  
pp. 85-90 ◽  
Author(s):  
Mostafa Odabaee ◽  
Emilie Sauret ◽  
Kamel Hooman
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Cfd Simulation ◽  
Pressure Ratio ◽  
Computational Cost ◽  
Real Gas ◽  
Table Method ◽  
Radial Inflow Turbine ◽  
Solar Resource ◽  
Supercritical Carbon

The present study explores CFD analysis of a supercritical carbon dioxide (SCO2) radial-inflow turbine generating 100kW from a concentrated solar resource of 560oC with a pressure ratio of 2.2. Two methods of real gas property estimations including real gas equation of estate and real gas property (RGP) file - generating a required table from NIST REFPROP - were used. Comparing the numerical results and time consumption of both methods, it was shown that equation of states could insert a significant error in thermodynamic property prediction. Implementing the RGP table method indicated a very good agreement with NIST REFPROP while it had slightly more computational cost compared to the RGP table method.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

Detached Eddy Simulation of Transonic Rotor Stall Flutter Using a Fully Coupled Fluid-Structure Interaction

2011 ◽  
Author(s):  
Hongsik Im ◽  
Xiangying Chen ◽  
Gecheng Zha
Keyword(s):  
Stokes Equations ◽  
Rotating Stall ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Weno Scheme ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Stall Flutter ◽  
Fully Coupled

Detached eddy simulation of an aeroelastic self-excited instability, flutter in NASA Rotor 67 is conducted using a fully coupled fluid/structre interaction. Time accurate compressible 3D Navier-Stokes equations are solved with a system of 5 decoupled modal equations in a fully coupled manner. The 5th order WENO scheme for the inviscid flux and the 4th order central differencing for the viscous flux are used to accurately capture interactions between the flow and vibrating blades with the DES (detached eddy simulation) of turbulence. A moving mesh concept that can improve mesh quality over the rotor tip clearance was implemented. Flutter simulations were first conducted from choke to stall using 4 blade passages. Stall flutter initiated at rotating stall onset, grows dramatically with resonance. The frequency analysis shows that resonance occurs at the first mode of the rotor blade. Before stall, the predicted responses of rotor blades decayed with time, resulting in no flutter. Full annulus simulation at peak point verifies that one can use the multi-passage approach with periodic boundary for the flutter prediction.

Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

2014 ◽  
Author(s):  
Yo Han Jung ◽  
Young Uk Min ◽  
Jin Young Kim
Keyword(s):  
Performance Test ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Tip Clearance ◽  
Low Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Flow Rates ◽  
Suction Performance ◽  
Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

A Proposal for Passive Wall Treatment Applied in High Performance Axial Flow Compressors

2020 ◽  
Author(s):  
Rubén Bruno Díaz ◽  
Jesuino Takachi Tomita ◽  
Cleverson Bringhenti ◽  
Francisco Carlos Elizio de Paula ◽  
Luiz Henrique Lindquist Whitacker
Keyword(s):  
Stokes Equations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Smooth Wall ◽  
Tip Leakage Flow ◽  
Viscous Effects ◽  
Stall Margin ◽  
Tip Leakage

Abstract Numerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

Sign in / Sign up

Export Citation Format

Share Document