scholarly journals Composite UHBR Fan for Forced Response and Flutter Investigations

2021 ◽  
Author(s):  
Torben Eggers ◽  
Jens Friedrichs ◽  
Jan Goessling ◽  
Joerg R. Seume ◽  
Nunzio Natale ◽  
...  
Keyword(s):  
Forced Response ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Future Research ◽  
Test Case ◽  
Composite Blade ◽  
Wide Range ◽  
Open Test ◽  
Performance Specifications ◽  
Transonic Fan

Abstract In the CA3ViAR (Composite fan Aerodynamic, Aeroelastic, and Aeroacoustic Validation Rig) project, a composite low-transonic fan is designed and tested. The aim is a scaled ultra-high bypass ratio (UHBR) fan with state-of-the-art aerodynamic performance and composite rotor blades, which features aeroelastic phenomena, e.g. forced response by inlet distortions and flutter, under certain operating points within the wind tunnel. In this paper, the aerodynamic and aeroelastic design process starting from the overall performance specifications to a threedimensional numerical model is described. A target of eigen-frequency and twist-to-plunge ratio is specified such that flutter occurs at desired operating conditions with a sufficient margin with respect to the working line. Different materials and layups of the composite blade are analyzed to reach the structural target. The fan should serve as an open test case to advance the future research on aerodynamic, aeroelastic, and aeroacoustic performance investigations in a wide range of operating conditions. A preliminary fan stage design is presented in this paper.

Wake Induced Time-Variant Aerodynamics Including Rotor-Stator Axial Spacing Effects

1981 ◽  
Vol 103 (1) ◽  
pp. 59-66 ◽  
Author(s):  
S. Fleeter ◽  
R. L. Jay ◽  
W. A. Bennett
Keyword(s):  
Large Scale ◽  
Primary Source ◽  
Forced Response ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Experimental Program ◽  
Axial Distance ◽  
Spacing Effects ◽  
Spacing Ratio ◽  
Wide Range

The overall objective of this experimental program was to quantify the effects of rotor-stator axial spacing on the fundamental time-variant aerodynamics relevant to forced response in turbomachinery. This was accomplished in a large-scale, low-speed, single-stage research compressor which permitted two rotor-stator axial spacing ratios representative of those found in advanced design compressors to be investigated. At each value of the axial spacing ratio, the aerodynamically induced fluctuating surface pressure distributions on the downstream vane row, with the primary source of excitation being the upstream rotor wakes, were measured over a wide range of compressor operating conditions. The velocity fluctuations created by the passage of the rotor blades were measured in the nonrotating coordinate system. Data obtained described the variation of the rotor wake with both loading and axial distance from the rotor as parameters. These data also served as a reference in the analysis of the resulting time-variant pressure signals on the vane surfaces.

On the Probabilistic Endurance Prediction Approach for Turbomachinery Blades and Vanes

2020 ◽  
Author(s):  
Davendu Y. Kulkarni ◽  
Caetano Peng
Keyword(s):  
Robust Design ◽  
Product Life Cycle ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Probabilistic Methods ◽  
Wide Range ◽  
Deterministic Methods ◽  
Stator Vane ◽  
Turbomachinery Blades ◽  
Prediction Approach

Abstract The design and aeromechanical assessment of turbomachinery blades and vanes comprises a wide range of complex processes that tend to be based on conventional deterministic methods. These processes often provide a ‘snapshot’ evaluation of the new component designs at the nominal operating conditions. While the deterministic methods can predict the high cycle fatigue (HCF) endurance with reasonable accuracy; they assume that the conservative safety factors applied to cover for the parametric variations, uncertainties and unknowns will not change during the product life cycle. This approach is intended to be conservative and in some cases may overlook the lack of robustness. The present paper proposes a robust design analysis approach based on probabilistic methodology for the aeromechanical assessment of rotor blades and stator vanes of turbomachinery. The robust design approach can account explicitly for the effects of design and manufacturing variability. This methodology can reduce the levels of conservatism in the deterministic approach and can provide a more thorough risk assessment. This paper offers a generalised aeromechanical analysis formulation based on probabilistic methods to evaluate the HCF capability of turbomachinery components. Herein, this methodology is demonstrated by using a typical stator vane of an aero engine compressor and it is based on Monte-Carlo and DOE simulations. The methodology consists of parametric sensitivity studies and identification of the most influential parameters that control the HCF endurance. Future ideas and roadmap of the aeromechanical probabilistic analysis capability development are also discussed.

A Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Application of an Improved Streamline Curvature Approach to a Modern, Two-Stage Transonic Fan: Comparison With Data and CFD

2002 ◽  
Author(s):  
Keith M. Boyer ◽  
Walter F. O’Brien
Keyword(s):  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Model Parameters ◽  
Two Stage ◽  
Streamline Curvature ◽  
Wide Range ◽  
Improved Model ◽  
Transonic Fan ◽  
Streamline Curvature Method

A streamline curvature method with improvements to key loss models is applied to a two-stage, low aspect ratio, transonic fan with design tip relative Mach number of approximately 1.65. Central to the improvements is the incorporation of a physics-based shock model. The attempt here is to capture the effects of key flow phenomena relative to the off-design performance of the fan. A quantitative analysis regarding solution sensitivities to model parameters that influence the key phenomena over a wide range of operating conditions is presented. Predictions are compared to performance determined from overall and interstage measurements, as well as from a three-dimensional, steady, Reynolds-averaged Navier-Stokes method applied across the first rotor. Overall and spanwise comparisons demonstrate that the improved model gives reasonable performance trending and generally accurate results. The method can be used to provide boundary conditions to higher-order solvers, or implemented within novel approaches using the streamline curvature method to explore complex engine-inlet integration issues, such as time-variant distortion.

Development of a Novel Axial Compressor Generation for Industrial Applications: Part 2 — Blade Mechanics

2014 ◽  
Author(s):  
Dirk Anding ◽  
Henning Ressing ◽  
Klaus Hörmeyer ◽  
Roland Pisch ◽  
Kai Ziegler
Keyword(s):  
High Efficiency ◽  
Axial Compressor ◽  
Forced Response ◽  
Operating Conditions ◽  
Strain Gauges ◽  
Blade Design ◽  
Operating Range ◽  
Resonance Frequencies ◽  
Wide Range ◽  
Blade Vibrations

Blade vibrations resulting in alternating stresses are often the critical factor in determining blade life. Indeed, many of the failures experienced by turbomachinery blades occur due to high-cycle fatigue caused by blade vibrations. These vibrations can arise either through self-excited oscillations known as flutter or through aerodynamic forcing of the blades from factors such as periodic wakes from up and/or downstream vanes or unsteady flow phenomena such as compressor surge. The current paper deals with the design and the analytical and experimental verification of the axial blading for a new generation of industrial compressors, a hybrid axial compressor that combines the advantages of conventional industrial compressors — broad operating range and high efficiency — with the advantages of gas turbine compressors — high power-density and high stage pressure ratios. Additionally, the surge robustness of this novel compressor blading has been greatly improved. During the development phase extensive efforts were made to ensure safe operation for future service life. This was achieved by designing blades that will not flutter, do not have high resonance amplitudes throughout their entire operating range and are extremely robust against surge. This strongly increased robustness of the new compressor blading was achieved by the implementation of a “wide-chord” blade design in all rotor blade rows in combination with a proper tuning of resonance frequencies throughout the entire operating range. For the verification of the new blading well-established methods accepted by industry were used such as CFD and FEA. Furthermore, coupling of the two into a method referred to as Fluid Structure Interaction (FSI) was used to more closely investigate the interaction of flow and structural dynamics phenomena. These analytical techniques have been used in conjunction with extensive testing of a scaled test compressor, which was operated at conditions of dynamic similitude (matching of scaled blade vibration frequencies, flow conditions, and Mach number) with full-scale operational conditions. Strain gauges placed on the blades and a state of the art technique known as “tip timing” were used to verify blade vibrations over a wide range of combinations of guide vane positions and rotational speeds. No propensity was found of any of the blades to develop high vibration amplitudes at any of the operating conditions investigated in the rig tests. The comparison of non-linear forced response analyses and the rig test results from strain gauges and tip timing showed close agreement, verifying the analysis techniques used. In conclusion it can be stated that the blade design exhibits a very high level of safety against vibrations within the entire operating range and during surge.

Impact of Turbine Center Frame Wakes on Downstream Rows in Heavy-Duty Low-Pressure Turbine

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Sara Biagiotti ◽  
Juri Bellucci ◽  
Michele Marconcini ◽  
Andrea Arnone ◽  
Gino Baldi ◽  
...  
Keyword(s):  
Experimental Data ◽  
Low Pressure ◽  
Numerical Approach ◽  
Forced Response ◽  
Operating Conditions ◽  
Response Analysis ◽  
Test Case ◽  
Low Pressure Turbine ◽  
Harmonic Content ◽  
The Impact

Abstract In this work, the effects of turbine center frame (TCF) wakes on the aeromechanical behavior of the downstream low-pressure turbine (LPT) blades are numerically investigated and compared with the experimental data. A small industrial gas turbine has been selected as a test case, composed of a TCF followed by the two low-pressure stages and a turbine rear frame (TRF) before the exhaust plenum. Full annulus unsteady computations of the whole low-pressure module have been performed. Two operating conditions, full (100%) and partial (50%) load, have been investigated with the aim of highlighting the impact of TCF wakes convection and diffusion through the downstream rows. Attention was paid to the harmonic content of rotors’ blades. The results show a slower decay of the wakes through the downstream rows in off-design conditions compared with the design point. The analysis of the rotors’ frequency spectrum reveals that moving from design to off-design conditions, the effect of the TCF does not change significantly. The harmonic contribution of all turbine components has been extracted, highlighting the effect of statoric parts on the last LPT blade. The TCF harmonic content remains the most relevant from an aeromechanic point of view as per experimental evidence, and it is considered for an forced response analysis (FRA) on the last LPT blade itself. Finally, aerodynamic and aeromechanic predictions have been compared with the experimental data to validate the numerical approach. Some general design solutions aimed at mitigating the TCF wakes impact are discussed.

scholarly journals Homogeneous Charge Compression Ignition Combustion: Challenges and Proposed Solutions

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Mohammad Izadi Najafabadi ◽  
Nuraini Abdul Aziz
Keyword(s):  
Homogeneous Charge Compression Ignition ◽  
Fuel Efficiency ◽  
Operating Conditions ◽  
Future Research ◽  
Compression Ignition ◽  
Ignition Timing ◽  
Ic Engine ◽  
Hcci Engine ◽  
Wide Range ◽  
Homogeneous Charge

Engine and car manufacturers are experiencing the demand concerning fuel efficiency and low emissions from both consumers and governments. Homogeneous charge compression ignition (HCCI) is an alternative combustion technology that is cleaner and more efficient than the other types of combustion. Although the thermal efficiency andNOxemission of HCCI engine are greater in comparison with traditional engines, HCCI combustion has several main difficulties such as controlling of ignition timing, limited power output, and weak cold-start capability. In this study a literature review on HCCI engine has been performed and HCCI challenges and proposed solutions have been investigated from the point view ofIgnition Timingthat is the main problem of this engine. HCCI challenges are investigated by many IC engine researchers during the last decade, but practical solutions have not been presented for a fully HCCI engine. Some of the solutions are slow response time and some of them are technically difficult to implement. So it seems that fully HCCI engine needs more investigation to meet its mass-production and the future research and application should be considered as part of an effort to achieve low-temperature combustion in a wide range of operating conditions in an IC engine.

Statistical Sensitivity Study of Frequency Mistuning on the Prediction of the Flutter Boundary in a Transonic Fan

2016 ◽  
Author(s):  
Atsushi Tateishi ◽  
Toshinori Watanabe ◽  
Takehiro Himeno ◽  
Mizuho Aotsuka ◽  
Takeshi Murooka
Keyword(s):  
Aerodynamic Force ◽  
Sensitivity Study ◽  
Dominant Mode ◽  
Operating Conditions ◽  
Modal Properties ◽  
Numerical Predictions ◽  
Wide Range ◽  
Damping Rate ◽  
Flutter Boundary ◽  
Transonic Fan

This paper aims at quantifying the stabilization effect of mistuning in transonic fan flutter. The results are used to support the evaluation of flutter boundary and to clarify the reason for the mismatch observed in the numerical predictions reported in our previous study. Mistuning is modeled by the deviation of blade-mode frequency, and the stability analysis of vibrating blades is formulated as an eigenproblem of the equation of motion including self-excited aerodynamic force obtained by fluid-structure interaction simulations. Statistics about the modal properties are obtained by Monte Carlo simulation. The change in the averaged damping rate and flutter boundary is evaluated in a wide range of mistuning levels and operating conditions. Nominal levels of mistuning due to manufacturing tolerance have little effect to the flutter boundary because the decline in aerodynamic damping is very steep. Therefore, the accuracy associated with the computational fluid dynamics is likely to have caused the mismatch in the flutter boundary. Histograms of modal properties show that the inter-blade phase angle and blade amplitudes in flutter mode can be highly scattered, even if the level of mistuning is nominal. For largely mistuned cases, new crests which do not exist in nominal cases appear in the eigenvalue histogram. They were found to be highly-localized, single-blade dominant mode.

A Modified Beddoes–Leishman Model for Unsteady Aerodynamic Blade Load Computations on Wind Turbine Blades

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Moutaz Elgammi ◽  
Tonio Sant
Keyword(s):  
Flow Separation ◽  
Random Noise ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Unsteady Aerodynamic ◽  
Novel Approach ◽  
Wide Range

A modified version of the Beddoes–Leishman (B-L) dynamic stall model is presented. A novel approach was applied for deriving the effective flow separation points using two-dimensional (2D) static wind tunnel test data in conjunction with Kirchhoff's model. The results were then fitted in a least-squares sense using a new nonlinear model that gives a better fit for the effective flow separation point under a wide range of operating conditions with fewer curve fitting coefficients. Another model, based on random noise generation, was also integrated within the B-L model to simulate the effects of vortex shedding more realistically. The modified B-L model was validated using 2D experimental data for the S809 and NACA 4415 aerofoils under both steady and unsteady (oscillating) conditions. The model was later embedded in a free-wake vortex model to estimate the unsteady aerodynamic loads on the NREL Phase VI rotor blades consisting of S809 aerofoils when operating under yawed rotor conditions. The results in this study confirm the effectiveness of the proposed modifications to the B-L method under both 2D and three-dimensional (3D) (rotating) conditions.

Shape Optimization of Transonic Compressor Blades Using Quasi-3D Flow Physics

2000 ◽  
Author(s):  
June Chung ◽  
Ki D. Lee
Keyword(s):  
Design Method ◽  
Computational Cost ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Compressor Blades ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range

A design method for transonic compressor rotor blades is developed based on Navier-Stokes physics. The method is applied to optimize the blade sections at several span stations, and new three-dimensional blades are constructed by interpolating the geometry of the designed blade sections. The method is demonstrated with NASA Rotor 37, producing new rotor blades with improved adiabatic efficiency over a wide range of operating conditions. The results indicate that the developed design process can find improved designs at an affordable computational cost.

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