Three-Dimensional Strains on Twisted and Swept Composite Rotor Blades in Vacuum

2020 ◽  
pp. 1-16
Author(s):  
Cheng Chi ◽  
Anubhav Datta ◽  
Inderjit Chopra ◽  
Renliang Chen
Keyword(s):  
Three Dimensional ◽  
Rotor Blades

Generation Mechanism of Broadband Whoosh Noise in an Automotive Turbocharger Centrifugal Compressor

2021 ◽  
pp. 1-35
Author(s):  
Rick Dehner ◽  
Pranav Sriganesh ◽  
Ahmet Selamet ◽  
Keith Miazgowicz
Keyword(s):  
Centrifugal Compressor ◽  
Combustion Engine ◽  
Three Dimensional ◽  
Leading Edge ◽  
Broadband Noise ◽  
Rotor Blades ◽  
Generation Mechanism ◽  
Primary Concern ◽  
Frequency Range ◽  
Modal Decomposition

Abstract The present study focuses on the acoustics of a turbocharger centrifugal compressor from a spark-ignition internal combustion engine. Whoosh noise is typically the primary concern for this type of compressor, which is loosely characterized by broadband sound elevation in the 4 to 13 kHz range. To identify the generation mechanism of broadband whoosh noise, the present study combines three approaches: three-dimensional (3D) computational fluid dynamics (CFD) predictions, experiments, and modal decomposition of 3D CFD results. After establishing the accuracy of predictions, flow structures and time-resolved pressures are closely examined in the vicinity of the main blade leading edge. This reveals the presence of rotating instabilities that may interact with the rotor blades to generate noise. An azimuthal modal decomposition is performed on the predicted pressure field to determine the number of cells and the frequency content of these rotating instabilities. The strength of the rotating instabilities and the frequency range in which noise is generated as a consequence of the rotor-rotating instability interaction, is found to correspond well with the qualitative trend of the whoosh noise that is measured several duct diameters upstream of the rotor blades. The variation of whoosh frequency range between low and high rotational speeds is interpreted through this analysis. It is also found that the whoosh noise primarily propagates along the duct as acoustic azimuthal modes. Hence, the inlet duct diameter, which governs the cut-off frequency for multi-dimensional acoustic modes, determines the lower frequency bound of the broadband noise.

Ingestion Into the Upstream Wheelspace of an Axial Turbine Stage

1994 ◽  
Vol 116 (2) ◽  
pp. 327-332 ◽  
Author(s):  
T. Green ◽  
A. B. Turner
Keyword(s):  
Pressure Distribution ◽  
Static Pressure ◽  
Three Dimensional ◽  
Computer Code ◽  
Rotor Blades ◽  
Rotor Speed ◽  
Turbine Stage ◽  
Flow Rates ◽  
Static Pressure Distribution ◽  
Axial Clearance

The upstream wheelspace of an axial air turbine stage complete with nozzle guide vanes (NGVs) and rotor blades (430 mm mean diameter) has been tested with the objective of examining the combined effect of NGVs and rotor blades on the level of mainstream ingestion for different seal flow rates. A simple axial clearance seal was used with the rotor spun up to 6650 rpm by drawing air through it from atmospheric pressure with a large centrifugal compressor. The effect of rotational speed was examined for several constant mainstream flow rates by controlling the rotor speed with an air brake. The circumferential variation in hub static pressure was measured at the trailing edge of the NGVs upstream of the seal gap and was found to affect ingestion significantly. The hub static pressure distribution on the rotor blade leading edges was rotor speed dependent and could not be measured in the experiments. The Denton three-dimensional C.F.D. computer code was used to predict the smoothed time-dependent pressure field for the rotor together with the pressure distribution downstream of the NGVs. The level and distribution of mainstream ingestion, and thus the seal effectiveness, was determined from nitrous oxide gas concentration measurements and related to static pressure measurements made throughout the wheelspace. With the axial clearance rim seal close to the rotor the presence of the blades had a complex effect. Rotor blades in connection with NGVs were found to reduce mainstream ingestion seal flow rates significantly, but a small level of ingestion existed even for very high levels of seal flow rate.

Effects of Tip Clearance on Hot Streak Migration in a High-Subsonic Single-Stage Turbine

2000 ◽  
Author(s):  
Daniel J. Dorney ◽  
Douglas L. Sondak
Keyword(s):  
Experimental Data ◽  
Three Dimensional ◽  
Single Stage ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Radial Spreading ◽  
Rotor Surface ◽  
Hot Streak ◽  
Turbine Airfoils

Experimental data have shown that combustor temperature non-uniformities can lead to the excessive heating of first-stage rotor blades in turbines. This heating of the rotor blades can lead to thermal fatigue and degrade turbine performance. The results of recent studies have shown that variations in the circumferential location, or clocking, of the first-stage vane airfoils can be used to minimize the adverse effects of the hot streaks due to the hot fluid mixing with the cooler fluid contained in the vane wake. In addition, the effects of the hot streak/airfoil count ratio on the heating patterns of turbine airfoils have been quantified. In the present investigation, three-dimensional unsteady Navier-Stokes simulations have been performed for a single-stage high-pressure turbine geometry operating in high subsonic flow to study the effects of tip clearance on hot streak migration. Baseline simulations were initially performed without hot streaks to compare with the experimental data. Two simulations were then performed with a superimposed combustor hot streak; in the first the tip clearance was set at the experimental value, while in the second the rotor was allowed to scrape along the outer case (i.e., the limit as the tip clearance goes to zero). The predicted results for the baseline simulations show good agreement with the available experimental data. The simulations with the hot streak indicate that the tip clearance increases the radial spreading of the hot fluid, and increases the integrated rotor surface temperature compared to the case without tip clearance.

scholarly journals The Development of Fast Response Aerodynamic Probes for Flow Measurements in Turbomachinery

1994 ◽  
Author(s):  
Roger W. Ainsworth ◽  
John L. Allen ◽  
J. Julian M. Batt
Keyword(s):  
Mach Number ◽  
Large Scale ◽  
Flow Direction ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Fast Response ◽  
Rotor Blades ◽  
Small Scale ◽  
Hot Wire ◽  
Flow Measurements

The advent of a new generation of transient rotating turbine simulation facilities, where engine values of Reynolds and Mach number are matched simultaneously together with the relevant rotational parameters for dimensional similitude (Dunn et al [1988], Epstein et al [1984]. Ainsworth et al [1988]), has provided the stimulus for developing improved instrumentation for investigating the aerodynamic flows in these stages. Much useful work has been conducted in the past using hot-wire and laser anemometers. However, hot-wire anemometers are prone to breakage in the high pressure flows required for correct Reynolds numbers, Furthermore some laser techniques require a longer runtime than these transient facilites permit, and generally yield velocity information only, giving no data on loss production. Advances in semiconductor aerodynamic probes are beginning to fulfil this perceived need. This paper describes advances made in the design, construction, and testing of two and three dimensional fast response aerodynamic probes, where semiconductor pressure sensors are mounted directly on the surface of the probes, using techniques which have previously been successfully used on the surface of rotor blades (Ainsworth, Dietz and Nunn [1991]). These are to be used to measure Mach number and flow direction in compressible unsteady flow regimes. In the first section, a brief review is made of the sensor and associated technology which has been developed to permit a flexible design of fast response aerodynamic probe. Following this, an extensive programme of testing large scale aerodynamic models of candidate geometries for suitable semiconductor scale probes is described, and the results of these discussed. The conclusions of these experiments, conducted for turbine representative mean and unsteady flows, yielded new information for optimising the design of the small scale semiconductor probes, in terms of probe geometry, sensor placement, and aerodynamic performance. Details are given of a range of wedge and pyramid semiconductor probes constructed, and the procedures used in calibrating and making measurements with them. Differences in performance are discussed, allowing the experimenter to choose an appropriate probe for the particular measurement required. Finally, the application of prototype semiconductor probes in a transient rotor experiment at HP turbine representative conditions is described, and the data so obtained is compared with (PD solutions of the unsteady viscous flow-field.

Three-Dimensional Solutions for Rotor Blades Using High-Order Geometrical Nonlinear Beam Finite Elements

2019 ◽  
Vol 64 (3) ◽  
pp. 1-10
Author(s):  
Matteo Filippi ◽  
Alfonso Pagani ◽  
Erasmo Carrera
Keyword(s):  
Finite Elements ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Shear Deformation Theory ◽  
High Order ◽  
Rotor Blades ◽  
Constitutive Law ◽  
Displacement Fields ◽  
Cross Sectional ◽  
The Cross

This paper proposes a geometrically nonlinear three-dimensional formalism for the static and dynamic study of rotor blades. The structures are modeled using high-order beam finite elements whose kinematics are input parameters of the analysis. The displacement fields are written using two-dimensional Taylor- and Lagrange-like expansions of the cross-sectional coordinates. As far as the Taylor-like polynomials are concerned, the linear case is similar to the first-order shear deformation theory, whereas the higher-order expansions include additional contributions that describe the warping of the cross section. The Lagrange-type kinematics instead utilizes the displacements of certain physical points as degrees of freedom. The inherent three-dimensional nature of the Carrera unified formulation enables one to include all Green–Lagrange strain components as well as all coupling effects due to the geometrical features and the three-dimensional constitutive law. A number of test cases are considered to compare the current solutions with experimental and theoretical results reported in terms of large deflections/rotations and frequencies related to small amplitude vibrations.

DYNAMICS AND BUCKLING OF THIN PRE-TWISTED BEAMS UNDER AXIAL LOAD AND TORQUE

2010 ◽  
Vol 10 (05) ◽  
pp. 957-981 ◽  
Author(s):  
A. Y. T. LEUNG
Keyword(s):  
Strain Energy ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Initial Stresses ◽  
Beam Columns ◽  
Nonlinear Part ◽  
Straight Beam ◽  
Natural Boundary Conditions ◽  
Twisted Beam

Free vibration and buckling of pre-twisted beams exhibit interesting coupling phenomena between compression, shears, moments and torque and have been the subject of extensive research due to their importance as models of wind turbines and helicopter rotor blades. The paper investigates the influence of axial compression and torque on the natural vibration of pre-twisted straight beam based on the Euler-Bernoulli theory. The derivation begins with the three-dimensional Green strain tensor. The nonlinear part of the strain tensor is expressed as a product of displacement gradient to derive the strain energy due to initial stresses. The Frenet formulae in differential geometry are employed to treat the pre-twist. The strain energy due to elasticity and the linear kinetic energy are obtained in classical sense. From the variational principle, the governing equations and the associated natural boundary conditions are derived. To the best knowledge of the author, the buckling of pre-twisted beam due to initial torque has not been studied in details. The major contribution of the paper is in the consideration of the influence of initial stresses caused by initial shears, moments and torques for pre-twisted beam-columns by means of the Frenet formulae and second order strains. A number of numerical examples are given. Some particular cases are compared with existing results. It is noted that the first mode increases together with the rate of twist but the second decreases seeming to close the first two modes together. The gaps close monotonically as the rate of twist increases for natural frequencies and buckling compressions.

Pressure feedback-based blade–vortex interaction noise controller for helicopter rotors

2018 ◽  
Vol 17 (3) ◽  
pp. 295-318 ◽  
Author(s):  
Sara Modini ◽  
Giorgio Graziani ◽  
Giovanni Bernardini ◽  
Massimo Gennaretti
Keyword(s):  
High Harmonic ◽  
Three Dimensional ◽  
Rotor Blades ◽  
Aerodynamic Noise ◽  
Vortex Interaction ◽  
Noise Sources ◽  
Power Requirement ◽  
Blade Vortex Interaction ◽  
Pressure Feedback ◽  
Helicopter Main Rotor

With the aim of alleviating the noise annoyance emitted by blade–vortex interactions occurring on helicopter main rotors, the present work presents a methodology suitable for the identification of a multi-cyclic harmonic controller based on the actuation of rotor blades equipped with Miniature Trailing Edge Effectors. The objective of the control methodology is the direct suppression of the aerodynamic noise sources by generation of localized high-harmonic blade–vortex interaction counter-actions. The set-up of control devices is selected on the basis of the blade–vortex interaction scenario, taking into account a trade-off between effectiveness and power requirement. The control law is efficiently identified by means of an optimal controller synthesized through suitable two-dimensional multi-vortex, parallel blade–vortex interaction problems. The proposed methodology is validated by the application to realistic helicopter main rotors during low-speed descent flights, numerically simulated through high-fidelity aerodynamic and aeroacoustic solvers based, respectively, upon a three-dimensional free-wake boundary element method to solve the potential flow around rotors in blade–vortex interaction conditions and the Farassat 1A formulation. Results concerning the capability of the proposed controller to alleviate the blade–vortex interaction noise emitted by a realistic helicopter main rotor are presented and discussed.

Aero-thermodynamic and chemical process interactions in an axial high-pressure turbine of aircraft engines

2018 ◽  
Vol 20 (6) ◽  
pp. 653-669 ◽  
Author(s):  
Trung Hieu Nguyen ◽  
Phuong Nguyen-Tri ◽  
Xavier Vancassel ◽  
Francois Garnier
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Chemical Processes ◽  
Rotor Blades ◽  
Rotor Speed ◽  
High Pressure Turbine ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Speed Effect ◽  
Flow Vortex

Precise investigation of aero-thermodynamic and chemical processes relating to environmental precursor pollutants in an aircraft turbine is challenging because of the complexity of transformation processes at high temperature and high pressure. We present here, for the first time, new insights into the study of aero-thermodynamic processes, formation of nitrate and sulfate aerosol precursors, and investigate the influence of chemical processes on aero-thermodynamics. We also shed light on the effect of three-dimensional blade profile, radial spacing, and rotor speed on the performance of a high-pressure turbine. We highlight that flow vortex and the variation of chemical formation which appear in both rear stator blades and rear rotor blades. We found that the chemical processes were affected by the evolution of temperature (maximum of 16.9%) and flow velocity (maximum of 38.8%). Contrary to the conservative one-dimensional and two-dimensional modeling, which provide only the flow trends and flow evolution at cylindrical surface, respectively, our three-dimensional modeling approach offers the possibility of combining information on radial spacing and rotor-speed effect by providing three-dimensional images of spatial-geometry effect on aero-thermodynamic and chemical processes. Quantitatively, the magnitude of change in aero-thermodynamics and nitrogen oxidation may be expected to be up to 17% and 48%, respectively, over a stage of the high-pressure turbine.

Investigation of Unsteady Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages

2002 ◽  
Author(s):  
Bjo¨rn Laumert ◽  
Hans Ma˚rtensson ◽  
Torsten H. Fransson
Keyword(s):  
Rotor Blade ◽  
Three Dimensional ◽  
Relative Strength ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Pressure Perturbation ◽  
Blade Surface ◽  
Excitation Mechanisms ◽  
Transonic Turbine ◽  
Exit Mach Number

This paper presents a study of the blade pressure perturbation levels and the resulting rotor blade force in three high-pressure transonic turbine stages, based on three-dimensional unsteady viscous computations. The aim is to identify stage characteristics that correlate with the perturbation strength and degree of force realization on the rotor blades. To address the effects of off-design operation, the computations were performed at high subsonic, design and higher vane exit Mach number operating conditions. Furthermore spanwise variations in pressure levels and blade force are addressed. In our investigation the RMS of the pressure perturbations integrated in both time and along the blade surface is utilized as a global measure of the blade pressure perturbation strength on the rotor blade surface. The relative strength of the different pressure perturbation events on the rotor blade surface is also investigated. To obtain information about the relative strength of events related to the blade passing frequency the pressure field is Fourier decomposed in time at different radial positions along the blade arc-length. With the help of the observations and results from the blade pressure study, the radial variations of the unsteady blade force are addressed.

Unsteady Interaction of Labyrinth Seal Leakage Flow and Downstream Stator Flow in a Shrouded 1.5 Stage Axial Turbine

2005 ◽  
Author(s):  
P. Peters ◽  
J. R. Menter ◽  
H. Pfost ◽  
A. Giboni ◽  
K. Wolter
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Numerical Data ◽  
Labyrinth Seal ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Experimental Program ◽  
Leakage Flow ◽  
Axial Turbine ◽  
Flow Phenomena

This paper presents the results of experimental and numerical investigations into the flow in a 1.5-stage low-speed axial turbine with shrouded rotor blades and a straight through labyrinth seal. The paper focuses on the time dependent influence of the leakage flow on the downstream stator flow field. The experimental program consists of time accurate measurements of the three-dimensional properties of the flow through ten different measurement planes in the stator passage. The measurements were carried out using pneumatic five-hole probes and three dimensional hot-wire probes at the design operating point of the turbine. The measurement planes extend from the shroud to the casing. The complex three-dimensional flow field is mapped in great detail by 4,800 measurement points and 20 time steps per blade passing period. The time-accurate experimental data of the ten measurement planes was compared with the results of unsteady, numerical simulations of the turbine flow. The 3D-Navier-Stokes Solver CFX-TASCflow was used. The experimental and numerical results correspond well and allow detailed analysis of the flow phenomena. Additionally numerical data behind the rotor is used to connect the entry of the leakage flow with the flow phenomena in the downstream stator passage and behind it. The leakage flow causes strong fluctuations of the flow in the downstream stator. Above all, the high number of measurement points reveals both the secondary flow phenomena and the vortex structures within the blade passage. The time-dependence of both the position and the intensity of the vortices influenced by the leakage flow is shown. The paper shows that even at realistic clearance heights the leakage flow influences considerable parts of the downstream stator and gives rise to negative incidence and flow separation. Thus, labyrinth seal leakage flow should be taken properly into account in the design or optimization process of turbines.

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