Aerodynamic Damping Analysis for Radial Turbine Featuring a Multi-Channel Casing Design

2020 ◽  
Author(s):  
Ahmed Farid Hassan ◽  
Tobias Müller ◽  
Markus Schatz ◽  
Damian M. Vogt
Keyword(s):  
Damping Ratio ◽  
Full Model ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Damping Behavior ◽  
Ansys Cfx ◽  
Partial Admission ◽  
Time Marching ◽  
Opening And Closing ◽  
Spiral Casing

Abstract Radial turbine featuring a Multi-channel Casing (MC) is a new design under investigation for enhancing the turbine controllability. The idea behind this new design is to replace the traditional spiral casing with a MC, which allows controlling the mass flow by means of opening and closing control valves in each channel. The arrangement of the closed and opened channel is called the admission configuration, while the ratio between the counts of the open channels to the total number of channels is called the admission percentage. Among several aspects, when applying different admission configurations, the aerodynamic damping during resonant excitation is considered during the design of the turbine. The present study aims at investigating the effect of different MC admission configurations on the aerodynamic damping as an extension to an aerodynamic forcing study, which already assessed the different forcing patterns associated with these different admission configurations. Due to the asymmetry of the flow in circumferential direction resulting from the different partial admission configurations, the computational model is solved as full 3D time-marching, unsteady flow using ANSYS CFX in a one-way fluid-structure analysis. Two different modeling approaches have been considered in this study to investigate their capability of predicting the damping ratio for different MC admission configurations: a) the conventional isolated rotor approach and b) a full model consisting of the rotor and its casing. The results show that the casing affects the aerodynamic damping behavior, which can only be captured by the full model. Furthermore, the damping ratios for all different admission configurations have been calculated using the full stage model.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines, a sustainable demand for radial turbine wheels has come along. Despite those blisks being state of the art, a number of fundamental problems, mainly referring to fluid-structure-interaction and, therefore, to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels, a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step, the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes, and the rotor blades of the entire turbine stage. In a second step, the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result, a measured low engine order excitation was found by modeling the spiral casing. Furthermore, a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to the measured data.

Forced Response Analyses of Mistuned Radial Inflow Turbines

2012 ◽  
Author(s):  
Thomas Giersch ◽  
Peter Hönisch ◽  
Bernd Beirow ◽  
Arnold Kühhorn
Keyword(s):  
Numerical Method ◽  
Fluid Structure Interaction ◽  
Industrial Applications ◽  
Forced Response ◽  
Blade Vibration ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerodynamic Damping ◽  
Radial Turbine ◽  
Spiral Casing

Radial turbine wheels designed as blade integrated disks (blisk) are widely used in various industrial applications. However, related to the introduction of exhaust gas turbochargers in the field of small and medium sized engines a sustainable demand for radial turbine wheels has come along. Despite those blisks are state of the art, a number of fundamental problems, mainly referred to fluid-structure-interaction and therefore to the vibration behavior, have been reported. Aiming to achieve an enhanced understanding of fluid-structure-interaction in radial turbine wheels a numerical method, able to predict forced responses of mistuned blisks due to aerodynamic excitation, is presented. In a first step the unsteady aerodynamic forcing is determined by modeling the spiral casing, the stator vanes and the rotor blades of the entire turbine stage. In a second step the aerodynamic damping induced by blade vibration is computed using a harmonic balance technique. The structure itself is represented by a reduced order model being extended by aerodynamic damping effects and aerodynamic forcings. Mistuning is introduced by adjusting the modal stiffness matrix based on results of blade by blade measurements that have been performed at rest. In order to verify the numerical method, the results are compared with strain-gauge data obtained during rig-tests. As a result a measured low engine order excitation was found by modeling the spiral casing. Furthermore a localization phenomenon due to frequency mistuning could be proven. The predicted amplitudes are close to measured data.

scholarly journals Numerical Simulation of the Performance of a Twin Scroll Radial Turbine at Different Operating Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Carlo Cravero ◽  
Davide De Domenico ◽  
Andrea Ottonello
Keyword(s):  
Operating Conditions ◽  
Inlet Section ◽  
Flow Distortion ◽  
Experimental Database ◽  
Design And Optimization ◽  
Radial Turbine ◽  
Ansys Cfx ◽  
Wide Range ◽  
Partial Admission ◽  
Turbine Design

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.

Performance Characterization of a Twin Scroll Volute for Turbocharging Applications

2018 ◽  
Author(s):  
Carlo Cravero ◽  
Mario La Rocca ◽  
Andrea Ottonello
Keyword(s):  
Experimental Data ◽  
Scientific Literature ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Automatic Design ◽  
Cfd Model ◽  
Radial Turbine ◽  
Wide Range ◽  
Partial Admission

The use of twin scroll volutes in radial turbine for turbocharging applications has several advantages over single passage volute related to the engine matching and to the overall compactness. Twin scroll volutes are of increasing interest in power unit development but the open scientific literature on their performance and modelling is still quite limited. In the present work the performance of a twin scroll volute for a turbocharger radial turbine are investigated in some detail in a wide range of operating conditions at both full and partial admission. A CFD model for the volute have been developed and preliminary validated against experimental data available for the radial turbine. Then the numerical model has been used to generate the database of solutions that have been investigated and used to extract the performance. Different parameters and indices are introduced to describe the volute aerodynamic performance in the wide range of operating conditions chosen. The above parameters can be used for volute development or matching with a given rotor or efficiently implemented in automatic design optimization strategies.

Damping Behavior of Blades From Small Radial Turbines

2015 ◽  
Author(s):  
David Hemberger ◽  
Dietmar Filsinger ◽  
Hans-Jörg Bauer
Keyword(s):  
Numerical Analysis ◽  
Dynamic Properties ◽  
Forced Response ◽  
Operating Conditions ◽  
Fe Model ◽  
Structural Damping ◽  
Aerodynamic Damping ◽  
Damping Behavior ◽  
Aerodynamic Properties ◽  
Radial Turbines

Next to excitation forces and the dynamic properties of mistuned structures the damping behavior is a key feature to evaluate the dynamic turbine blade response and thus the HCF life of a bladed disk (blisk). Just as the determination of the mistuning properties and the assessment of the vibration excitation, the evaluation of damping is also subject to uncertainty especially considering the wide operating range of a small radial turbine of a turbocharger. Since the total damping is composed of material damping, structural damping and aerodynamic damping, which are affected by parameters, like the eigenform of the vibration, the magnitude of the vibration amplitude and aerodynamic properties, the total damping can be strongly dependent on the operating conditions. The study at hand provides results from investigations that allow estimating the contribution of aerodynamic damping on the total damping. Experimental and numerical analysis of radial turbines from turbochargers for vehicular engines with variable turbine inlet vanes were performed. Measurements under different environmental conditions such as at rest and during operation, as well as unsteady CFD calculations and, coupled flow and structural calculations were carried out. A change in total damping could be found depending on the density of the surrounding gas by vibration measurements in operation on the hot gas test bench. But it was also shown that the total damping is decisively influenced by the mistuning of the structure. On one side the structural damping is varied by the variation in mistuned blade vibration amplitudes and otherwise the aerodynamic damping is influenced by the different inter blade phase angles (IBPA ) due to the mistuning, which is a symptom of geometric differences and material inhomogeneity in the wheels. Finally, the estimated total damping values were utilized in forced response calculations using a mistuned FE-model of a real turbine and excitation forces from unsteady CFD calculation. The magnitudes of the measured vibration amplitudes were compared with results from numerical analysis to validate the numerical model with focus on the investigation about the total damping. The deviation between the results was ±10% for different eigenforms and excitation orders.

Aeroelastic Flutter Investigation and Stability Enhancement of a Transonic Axial Compressor Rotor Using Casing Treatment

2017 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
Sankar Kumar Jeyaraman ◽  
Ajay Pratap ◽  
Kishore Prasad Deshkulkarni
Keyword(s):  
Flow Separation ◽  
Aerodynamic Force ◽  
Damping Ratio ◽  
Axial Compressor ◽  
Casing Treatment ◽  
Aerodynamic Damping ◽  
Compressor Rotor ◽  
Aeroelastic Flutter ◽  
Blade Tip ◽  
Transonic Axial Compressor

This study discusses in detail the aeroelastic flutter investigation of a transonic axial compressor rotor using computational methods. Fluid structure interaction approach is used in this method to evaluate the unsteady aerodynamic force and work done of a vibrating blade in CFD domain. Energy method and work per cycle approach is adapted for this flutter prediction. A framework has been developed to estimate the work per cycle and aerodynamic damping ratio. Based on the aerodynamic damping ratio, occurrence of flutter is estimated for different inter blade phase angles. Initially, the baseline rotor blade design was having negative aerodynamic damping at part speed conditions. The main cause for this flutter occurrence was identified as large flow separation near blade tip region due to high incidence angles. The unsteadiness in the flow was leading to aerodynamic force fluctuation matching with natural frequency of blade, resulting in excitation of the blades. Hence axially skewed slot casing treatment was implemented to reduce the flow separation at blade tip region to alleviate the onset of flutter. By this method, the stall margin and aerodynamic damping of the test compressor was improved and flutter was avoided.

Advanced Calculation Flutter Procedure Developed for Ultra-Long Last Stage Blades for Steam Turbines

2019 ◽  
Author(s):  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Ales Macalka ◽  
Jiri Ira ◽  
Antonin Zivny
Keyword(s):  
Stokes Equations ◽  
Damping Ratio ◽  
Rotor Blades ◽  
Numerical Code ◽  
Navier Stokes ◽  
Steam Turbines ◽  
Navier Stokes Equations ◽  
Time Marching ◽  
Last Stage ◽  
The Time Domain

Abstract An advanced in-house procedure, which is based on a commercial numerical code, to predict a potential danger of unstalled flutter has been developed and validated. This procedure using a one way decoupled method and a full-scale time-marching 3D viscous model in order to obtain the solution of the Unsteady Reynolds-Averaged Navier-Stokes equations in the time domain thus calculate an aerodynamic work and a damping ratio is used as an essential tool for developing ultra-long last stage rotor blades in low pressure turbine parts for modern steam turbines with a large operating range and an enhanced efficiency. An example is shown on a development of the last stage blade for high backpressures.

Contribution of carbon nanotubes to vibration damping behavior of epoxy and its carbon fiber composites

2020 ◽  
Vol 39 (7-8) ◽  
pp. 311-323
Author(s):  
Esma Avil ◽  
Ferhat Kadioglu ◽  
Cevdet Kaynak
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Carbon Fiber ◽  
Damping Ratio ◽  
Vibration Damping ◽  
Matrix Composites ◽  
Fiber Reinforced ◽  
Damping Behavior ◽  
Continuous Carbon Fiber ◽  
Carbon Fiber Reinforced

The main objective of this study was to investigate contribution of the non-functionalized multi-walled carbon nanotubes on the vibration damping behavior of first neat epoxy resin and then unidirectional and bidirectional continuous carbon fiber reinforced epoxy matrix composites. Epoxy/carbon nanotubes nanocomposites were produced by ultrasonic solution mixing method, while the continuous carbon fiber reinforced composite laminates were obtained via resin-infusion technique. Vibration analysis data of the specimens were evaluated by half-power bandwidth method; and the mechanical properties of the specimens were determined with three-point bending flexural tests, including morphological analyses under scanning electron microscopy. It was generally concluded that when even only 0.1 wt% carbon nanotubes were incorporated into neat epoxy resin, they have contributed not only to the mechanical properties (flexural strength and modulus), but also to the vibration behavior (damping ratio) of the epoxy. When 0.1 or 0.5 wt% carbon nanotubes were incorporated into continuous carbon fiber reinforced epoxy matrix composites, although they have no additional contribution to the mechanical properties, their contribution in terms of damping ratio of the composites were significant.

The Effects of Fiber Volume Fraction on the Vibration Damping Characteristics of Three-Layer-Connected Biaxial Weft Knitted Fabric Reinforced Composite Materials

2012 ◽  
Vol 602-604 ◽  
pp. 49-52
Author(s):  
Jing Xue Liu ◽  
Jia Lu Li
Keyword(s):  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Damping Ratio ◽  
Vibration Damping ◽  
Knitted Fabric ◽  
Vibration Modes ◽  
Fiber Volume ◽  
Damping Behavior ◽  
Weft Knitted Fabric ◽  
Vibration Parameters

The paper presents an analysis of the vibration damping properties of three-layer-connected biaxial weft knitted fabric (TBWK), which are constituted of carbon fibers as inserted yarns and polyester yarns as knitted yarns impregnated in an epoxy matrix with resin transfer molding (RTM) technique. Damping parameters were investigated using beam test specimens and an impulse technique. Several vibration parameters were varied to characterize the damping behavior in different amplitudes, natural frequencies and vibration modes. The results obtained show that the damping ratio of TBWK composites decreases with the increasing of fiber volume fraction in all the three vibration modes. The vibration test also indicates that the natural frequency of the TBWK composites increases with the increasing of fiber volume fraction (Vf) in all the three modes.

Paper 23: An Experimental Investigation of Non-Steady Flow in a Radial Gas Turbine

1965 ◽  
Vol 180 (10) ◽  
pp. 74-85 ◽  
Author(s):  
R. S. Benson ◽  
K. H. Scrimshaw
Keyword(s):  
Steady Flow ◽  
Mass Flow ◽  
Pulse Generator ◽  
Flow Analysis ◽  
Pulse Frequency ◽  
Exhaust Pipe ◽  
Transient Pressure ◽  
Radial Turbine ◽  
Admission Data ◽  
Partial Admission

Comprehensive steady and non-steady flow tests on a small radial turbine turbo-charger are given. Steady flow tests included both full admission and partial admission over the whole speed and pressure range from zero flow to maximum flow. Non-steady flow tests were carried out over a pulse frequency range from 30 to 70 pulses/s and turbine speeds from 30 000 to 60 000 rev/min with the turbine coupled to the exhaust system of a six-cylinder pulse generator under partial admission conditions. Extensive transient pressure and temperature measurements were taken upstream and downstream (pressure only) of the turbine. The total mass flow and power were also measured. A quasi-steady flow analysis was carried out using the steady flow test data. The tests results showed that for a six-cylinder exhaust pipe configuration, with two exhaust pipes entering separate nozzle segments in the radial turbine, the quasi-steady flow analysis using partial admission data grossly underestimated the mass flow and power output of the turbine. Using full admission data the ratio of measurement mass flow and horsepower to the calculated mass flow and horsepower was nearly always greater than unity. Furthermore, the average turbine efficiency was greater under non-steady flow than under steady flow. The magnitude of the recorded effects was dependent on the pulse frequency and turbine speed.

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