Transonic Fan Blade Redesign Approach to Attenuate Nonsynchronous Vibration

2021 ◽  
Author(s):  
Yaozhi Lu ◽  
Bharat Lad ◽  
Mehdi Vahdati
Keyword(s):  
Fan Blade ◽  
Transonic Fan

Radial Decomposition of Blade Vibration to Identify a Stall Flutter Source in a Transonic Fan

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Q. Rendu ◽  
M. Vahdati ◽  
L. Salles
Keyword(s):  
Pressure Fluctuations ◽  
Navier Stokes ◽  
Local Vibration ◽  
Blade Vibration ◽  
Nonlinear Solver ◽  
Low Mass ◽  
Stall Flutter ◽  
Fan Blade ◽  
Unstable Oscillation ◽  
Transonic Fan

Abstract This paper investigates the three dimensionality of the unsteady flow responsible for stall flutter instability. Nonlinear unsteady Reynolds-averaged Navier–Stokes (RANS) computations are used to predict the aeroelastic behavior of a fan blade at part speed. Flutter is experienced by the blades at low mass flow for the first flap mode at nodal diameter 2. The maximal energy exchange is located near the tip of the blade, at 90% span. The modeshape is radially decomposed to investigate the main source of instability. This decomposition method is validated for the first time in 3D using a time-marching nonlinear solver. The source of stall flutter is finally found at 65% span where the local vibration induces an unstable oscillation of the shock-wave of large amplitude. This demonstrates that the radial migration of the pressure fluctuations must be taken into account to predict stall flutter.

Experimental Reduction of Transonic Fan Forced Response by IGV Flow Control

2004 ◽  
Author(s):  
S. Todd Bailie ◽  
Wing F. Ng ◽  
William W. Copenhaver
Keyword(s):  
Flow Control ◽  
Forced Response ◽  
Resonant Response ◽  
Compressor Blades ◽  
Resonant Amplitude ◽  
Engine Order ◽  
Blade Vibrations ◽  
Fan Blade ◽  
Transonic Fan ◽  
Bending Response

The main contributor to the high-cycle fatigue of compressor blades is the response to aerodynamic forcing functions generated by an upstream row of stators or inlet guide vanes. Resonant response to engine order excitation at certain rotor speeds can be especially damaging. Studies have shown that flow control by trailing edge blowing (TEB) can reduce stator wake strength and the amplitude of the downstream rotor blade vibrations generated by the unsteady stator-rotor interaction. In the present study, the effectiveness of TEB to reduce forced fan blade vibrations was evaluated in a modern single-stage transonic fan rig. Data was collected for multiple uniform full-span TEB conditions over a range of rotor speed including multiple modal resonance crossings. Resonant response sensitivity was generally characterized by a robust region of strong attenuation. The baseline resonant amplitude of the first torsion mode, which exceeded the endurance limit on the critical blade, was reduced by more than 80% with TEB at 1.0% of the total rig flow. The technique was also found to be modally robust; similar reductions were achieved for all tested modal crossings, including more than 90% reduction of the second LE bending response using 0.7% of the rig flow.

scholarly journals Effect of Geometry Variability on Transonic Fan Blade Untwist †

2019 ◽  
Vol 4 (3) ◽  
pp. 24
Author(s):  
Yaozhi Lu ◽  
Bharat Lad ◽  
Jeff Green ◽  
Sina Stapelfeldt ◽  
Mehdi Vahdati
Keyword(s):  
High Cycle Fatigue ◽  
Related Phenomenon ◽  
Peak Efficiency ◽  
Fan Performance ◽  
Manufacturing Tolerance ◽  
Efficiency Condition ◽  
Fatigue Characteristics ◽  
Fan Blade ◽  
Adverse Influence ◽  
Transonic Fan

Due to manufacturing tolerance and deterioration during operation, fan blades in the same engine exhibit geometric variability. The absence of symmetry will inevitably exacerbate and contribute to the complexities of running geometry prediction as the blade variability is bound to be amplified by aerodynamic and centrifugal loading. In this study, we aim to address the fan blade untwist related phenomenon known as alternate passage divergence (APD). As the name suggests, APD manifests as alternating passage geometry (and hence alternating tip stagger pattern) when the fan stage is operating close to/at peak efficiency condition. APD can introduce adverse influence on fan performance, aeroacoustics behaviour, and high cycle fatigue characteristics of the blade. The main objective of the study is to identify the parameters contributing to the APD phenomenon. In this study, the APD behaviours of two transonic fan blade designs are compared.

Aero-Mechanical Optimization Design of a Transonic Fan Blade

2013 ◽  
Author(s):  
Xiangyang Deng ◽  
Fushui Guo ◽  
Yesheng Liu ◽  
Pinlian Han
Keyword(s):  
Optimal Design ◽  
Optimization Design ◽  
Mechanical Performance ◽  
Static Stress ◽  
Optimization Techniques ◽  
Optimization Process ◽  
Mechanical Constraints ◽  
Fan Blade ◽  
Transonic Fan ◽  
Mechanical Optimization

This paper presents the optimization design of a high bypass ratio civil fan blade with the consideration of aerodynamics, static and dynamic mechanics. The baseline fan blade was designed with a conventional approach without using automatic optimization techniques on both the aero side and the mechanical side. Therefore, the objective of this paper is to achieve a higher aero-mechanical performance under the multiple aerodynamic and mechanical constraints. Before the optimization, the static stress and modal analysis are performed on the baseline fan blade with/without the introduction of the arc dovetail root and shank. The results are compared to investigate the necessity of including the arc root and shank in the aero-mechanical optimization. With respect to the optimization process, the numerical design of experiment (DOE) by means of high fidelity CFD/FEA computations is firstly performed to construct the database for the initialization of Kriging surrogate mode. After that, the surrogate model is integrated with the optimization design process, and the non-dominated sorting genetic algorithm (NSGAII) is implemented to obtain the Pareto front, based on which the optimal design is selected. Utilizing this optimization process, both the aero-only and aero-mechanical optimizations are carried out. The results show that the attenuation of the 3D shock wave strength between the middle and shroud span improves the overall aero performance of the fan blade in both the aero-only optimal design and the aero-mechanical optimal design. Compared with the aero-only optimal design, the aero-mechanical optimal design shows the efficiency penalty within all the operation range simulated, however, the mechanical performance is significantly enhanced by the mitigation of the static stress level on the entire arc dovetail root and shank as well as the increase of the resonance margin.

Transonic Fan Blade Redesign Approach to Attenuate Nonsynchronous Vibration

2020 ◽  
Author(s):  
Yaozhi Lu ◽  
Bharat Lad ◽  
Mehdi Vahdati
Keyword(s):  
High Cycle Fatigue ◽  
Wave Pattern ◽  
Travelling Wave ◽  
Peak Efficiency ◽  
Aerodynamic Loads ◽  
Manufacturing Tolerance ◽  
Unsteady Effect ◽  
Fan Blade ◽  
Transonic Fan ◽  
Stagger Angle

Abstract Due to manufacturing tolerance and deterioration during operation, different blades in a fan assembly exhibit geometric variability. This leads to asymmetry which will be amplified in the running geometry by centrifugal and aerodynamic loads. This study investigates a phenomenon known as Alternate Passage Divergence (APD), where the blade untwist creates an alternating pattern in passage geometry and stagger angle around the circumference. After the formation of alternating tip stagger pattern, APD’s unsteady effect, APD-induced Non-Synchronous Vibration (APD-NSV), can cause the blades from one group to switch to the other creating a travelling wave pattern around the circumference. Thus, it can potentially lead to high cycle fatigue issues. More importantly, this phenomenon occurs close to, or at, peak efficiency conditions and can significantly reduce overall efficiency. Therefore, it is vital to attenuate the NSV behaviour. In this study, an redesign approach is investigated.

scholarly journals Using Shock Control Bumps to Improve Transonic Fan/Compressor Blade Performance

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Alistair John ◽  
Ning Qin ◽  
Shahrokh Shahpar
Keyword(s):  
Compressor Blade ◽  
3D Analysis ◽  
Aerodynamic Optimization ◽  
Compressor Blades ◽  
Stall Inception ◽  
Stall Margin ◽  
Shock Control ◽  
Fan Blade ◽  
Transonic Fan ◽  
Critical Regions

Shock control bumps can help to delay and weaken shocks, reducing loss generation and shock-induced separation and delaying stall inception for transonic turbomachinery components. The use of shock control bumps on turbomachinery blades is investigated here for the first time using 3D analysis. The aerodynamic optimization of a modern research fan blade and a highly loaded compressor blade is carried out using shock control bumps to improve their performance. Both the efficiency and stall margin of transonic fan and compressor blades may be increased through the addition of shock control bumps to the geometry. It is shown how shock-induced separation can be delayed and reduced for both cases. A significant efficiency improvement is shown for the compressor blade across its characteristic, and the stall margin of the fan blade is increased by designing bumps that reduce shock-induced separation near to stall. Adjoint surface sensitivities are used to highlight the critical regions of the blade geometries, and it is shown how adding bumps in these regions improves blade performance. Finally, the performance of the optimized geometries at conditions away from where they are designed is analyzed in detail.

Multi-Disciplinary Design Optimization of Transonic Fan Blade Design Using Analytical Target Cascading

2014 ◽  
Author(s):  
Saima Naz ◽  
Christophe Tribes ◽  
J.-Y. Trépanier ◽  
Jason Nichols ◽  
Eddy Petro
Keyword(s):  
Design Optimization ◽  
Solution Process ◽  
System Level ◽  
Analytical Target Cascading ◽  
Structure And Dynamics ◽  
Design Variables ◽  
Key Points ◽  
Target Cascading ◽  
Fan Blade ◽  
Transonic Fan

Analytical Target Cascading (ATC), a multilayer multidisciplinary design optimization (MDO) formulation employed on a transonic fan design problem. This paper demonstrates the ATC solution process including the specific way of initializing the problem and handling system level and discipline level targets. High-fidelity analysis tools for aerodynamics, structure and dynamics disciplines have been used. A multi-level parameterization of the fan blade is considered for reducing the number of design variables. The overall objective is the transonic fan efficiency improvement under structure and dynamics constraints. This design approach is applied to the redesign of the NASA Rotor 67. The overall study explores the key points of implementation of ATC on transonic fan design practical problem.

scholarly journals Global Optimisation of a Transonic Fan Blade Through AI-Enabled Active Subspaces

2021 ◽  
pp. 1-33
Author(s):  
Diego Lopez ◽  
Tiziano Ghisu ◽  
Shahrokh Shahpar
Keyword(s):  
Pressure Ratio ◽  
Computational Cost ◽  
High Dimensional ◽  
Jet Engine ◽  
Cfd Models ◽  
Active Subspaces ◽  
Fan Blade ◽  
Novel Strategy ◽  
Optimisation Methods ◽  
Transonic Fan

Abstract The increased need to design higher performing aerodynamic shapes has led to design optimisation cycles requiring high-fidelity CFD models and high-dimensional parametrisation schemes. The computational cost of employing global search algorithms on such scenarios has typically been prohibitive for most academic and industrial environments. In this paper, a novel strategy is presented that leverages the capabilities of Artificial Neural Networks for regressing complex unstructured data, while coupling them with dimensionality reduction algorithms. This approach enables employing global-based optimisation methods on high-dimensional applications through a reduced computational cost. This methodology is demonstrated on the efficiency optimisation of a modern jet engine fan blade with constrained pressure ratio. The outcome is compared against a state-of-the-art adjoint-based approach. Results indicate the strategy proposed achieves comparable improvements to its adjoint counterpart with a reduced computational cost, and can scale better to multi-objective optimisation applications.

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