scholarly journals Three-dimensional low-order surge model for high-speed axial compressors

2020 ◽  
Vol 4 ◽  
pp. 274-284
Author(s):  
Mauro Righi ◽  
Vassilios Pachidis ◽  
László Könözsy ◽  
Fanzhou Zhao ◽  
Mehdi Vahdati
Keyword(s):  
High Speed ◽  
Transient Flow ◽  
Computational Cost ◽  
Three Dimensional ◽  
Experimental Tests ◽  
High Fidelity ◽  
Order Model ◽  
Axial Compressors ◽  
Aero Engines ◽  
Low Order

Surge in modern aero-engines can lead to violent disruption of the flow, damage to the blade structures and eventually engine shutdown. Knowledge of unsteady performance and loading during surge is crucial for compressor design, however, the understanding and prediction capability for this phenomenon is still very limited. While useful for the investigation of specific cases, costly experimental tests and high-fidelity CFD simulations cannot be used routinely in the design process of compressor systems. There is therefore an interest in developing a low-order model which can predict compressor performance during surge with sufficient accuracy at significantly reduced computational cost. This paper describes the validation of an unsteady 3D through-flow code developed at Cranfield University for the low-order modelling of surge in axial compressors. The geometry investigated is an 8-stage rig representative of a modern aero-engine IP compressor. Two deep surge events are modelled at part speed and full speed respectively. The results are compared against high-fidelity, full annulus, URANS simulations conducted at Imperial College. Comparison of massflow, pressure and temperature time histories shows a close match between the low-order and the higher-fidelity methods. The low-order model is shown capable of predicting many transient flow features which were observed in the high-fidelity simulations, while reducing the computational cost by up to two orders of magnitude.

scholarly journals Three-dimensional low-order surge model for high-speed axial compressors

2020 ◽  
Author(s):  
Mauro Righi ◽  
◽  
Vassilios Pachidis ◽  
László Könözsy ◽  
Fanzhou Zhao ◽  
...  
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressors ◽  
Low Order

scholarly journals Body-force and mean-line models for the generation of axial compressor sub-idle characteristics

2020 ◽  
Vol 124 (1281) ◽  
pp. 1683-1701 ◽  
Author(s):  
M. Righi ◽  
L.E. Ferrer-Vidal ◽  
V. Pachidis
Keyword(s):  
Body Force ◽  
Computational Cost ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Axial Compressors ◽  
Characteristic Lines ◽  
Computational Fluid Dynamics Cfd ◽  
Operating Points ◽  
Low Order

ABSTRACTThis paper describes the application of low-order models to the prediction of the steady performance of axial compressors at sub-idle conditions. An Euler body-force method employing sub-idle performance correlations is developed and presented alongside a mean-line approach employing the same set of correlations. The low-order tools are used to generate the characteristic lines of the compressor in the locked-rotor and zero-torque windmilling conditions. The results are compared against steady-state operating points from three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) simulations. The accuracy of the low-order tools in reproducing the results from high-fidelity CFD is analysed, and the trade-off with the computational cost of each method is discussed. The low-order tools presented are shown to offer a fast alternative to traditional CFD which can be used to predict the performance in sub-idle conditions of a new compressor design during early development stages.

An Efficient Quasi-Three-Dimensional Model of Tilting Pad Journal Bearing for Turbomachinery Applications

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Andrea Rindi ◽  
Stefano Rossin ◽  
R. Conti ◽  
A. Frilli ◽  
E. Galardi ◽  
...  
Keyword(s):  
High Speed ◽  
Computational Cost ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Journal Bearings ◽  
Three Dimensional Model ◽  
Accurate Analysis ◽  
Technical Data ◽  
Plant Behavior ◽  
Tilting Pad

The constant increase of turbomachinery rotational speed has brought the design and the use of journal bearings to their very limits: tilting pad journal bearings (TPJBs) have been introduced for high-speed/high-load applications due to their intrinsic stability properties and can be used both in transient and steady-state operations obtaining superior performances. An accurate analysis of the TPJBs behavior is essential for a successful design and operation of the system; however, it is necessary to reach a compromise between the accuracy of the results provided by the TPJB model and its computational cost. This research paper exposes the development of an innovative and efficient quasi-3D TPJB modeling approach that allows the simultaneous analysis of the system rotordynamics and the supply plant behavior; the majority of existing models describe these aspects separately but their complex interaction must be taken into account to obtain a more accurate characterization of the system. Furthermore, the proposed model is characterized by a high numerical efficiency and modularity, allowing for complex transient simulations of the complete plant and for the representation of different kind of bearings. The TPJB model has been developed and experimentally validated in collaboration with an industrial partner which provided the technical data of the system and the results of experimental tests.

Enabling efficient uncertainty quantification for seismic modeling via projection-based model reduction

2021 ◽  
Author(s):  
Francesco Rizzi ◽  
Eric Parish ◽  
Patrick Blonigan ◽  
John Tencer
Keyword(s):  
Uncertainty Quantification ◽  
Shear Waves ◽  
Computational Cost ◽  
Memory Bandwidth ◽  
High Fidelity ◽  
Seismic Modeling ◽  
Order Model ◽  
Rank 2 ◽  
Many Core ◽  
Fidelity Model

<p>This talk focuses on the application of projection-based reduced-order models (pROMs) to seismic elastic shear waves. Specifically, we present a method to efficiently propagate parametric uncertainties through the system using a novel formulation of the Galerkin ROM that exploits modern many-core computing nodes.</p><p>Seismic modeling and simulation is an active field of research because of its importance in understanding the generation, propagation and effects of earthquakes as well as artificial explosions. We stress two main challenges involved: (a) physical models contain a large number of parameters (e.g., anisotropic material properties, signal forms and parametrizations); and (b) simulating these systems at global scale with high-accuracy requires a large computational cost, often requiring days or weeks on a supercomputer. Advancements in computing platforms have enabled researchers to exploit high-fidelity computational models, such as highly-resolved seismic simulations, for certain types of analyses. Unfortunately, for analyses requiring many evaluations of the forward model (e.g., uncertainty quantification, engineering design), the use of high-fidelity models often remains impractical due to their high computational cost. Consequently, analysts often rely on lower-cost, lower-fidelity surrogate models for such problems.</p><p>Broadly speaking, surrogate models fall under three categories, namely (a) data fits, which construct an explicit mapping (e.g., using polynomials, Gaussian processes) from the system's parameters to the system response of interest, (b) lower-fidelity models, which simplify the high-fidelity model (e.g., by coarsening the mesh, employing a lower finite-element order, or neglecting physics), and (c) pROMs which reduce the number of degrees of freedom in the high-fidelity model by a projection process of the full-order model onto a subspace identified from high-fidelity data. The main advantage of pROMs is that they apply a projection process directly to the equations governing the high-fidelity model, thus enabling stronger guarantees (e.g., of structure preservation or of accuracy) and more accurate a posteriori error bounds.</p><p>State-of-the-art Galerkin ROM formulations express the state as a rank-1 tensor (i.e., a vector), leading to computational kernels that are memory bandwidth bound and, therefore, ill-suited for scalable performance on modern many-core and hybrid computing nodes. In this work, we introduce a reformulation, called rank-2 Galerkin, of the Galerkin ROM for linear time-invariant (LTI) dynamical systems which converts the nature of the ROM problem from memory bandwidth to compute bound, and apply it to elastic seismic shear waves in an axisymmetric domain. Specifically, we present an end-to-end demonstration of using the rank-2 Galerkin ROM in a Monte Carlo sampling study, showing that the rank-2 Galerkin ROM is 970 times more efficient than the full order model, while maintaining excellent accuracy in both the mean and statistics of the field.</p>

Inverse Design of 3D Compressor Blades With Adjoint Method

2003 ◽  
Author(s):  
June Chung ◽  
Jeonghwan Shim ◽  
Ki D. Lee
Keyword(s):  
High Speed ◽  
Adjoint Method ◽  
Design Method ◽  
Computational Cost ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Adjoint System ◽  
Inverse Design ◽  
Compressor Blades

A three-dimensional (3D) CFD-based design method for high-speed axial compressor blades is being developed based on the discrete adjoint method. An adjoint code is built corresponding to RVC3D, a 3D turbomachinery Navier-Stokes analysis code developed at NASA Glenn. A validation study with the Euler equations indicates that the adjoint sensitivities are sensitive to the choice of boundary conditions for the adjoint variables in internal flow problems and constraints may be needed on internal boundaries to capture proper physics of the adjoint system. The design method is demonstrated with inverse design based on Euler physics, and the results indicate that the adjoint design method produces efficient 3D designs by drastically reducing the computational cost.

A Low-Order Model for Predicting Turbocharger Turbine Unsteady Performance

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Teng Cao ◽  
Liping Xu
Keyword(s):  
Power Output ◽  
Three Dimensional ◽  
Pulsating Flow ◽  
Navier Stokes ◽  
Order Model ◽  
Wave Dynamics ◽  
Predicting Performance ◽  
Set Up ◽  
Cfd Method ◽  
Low Order

In this paper, a low-order model for predicting performance of radial turbocharger turbines is presented. The model combines an unsteady quasi-three-dimensional (Q3D) computational fluid dynamics (CFD) method with multiple one-dimensional (1D) meanline impeller solvers. The new model preserves the critical volute geometry features, which is crucial for the accurate prediction of the wave dynamics and retains effects of the rotor inlet circumferential nonuniformity. It also still maintains the desirable properties of being easy to set-up and fast to run. The model has been validated against a experimentally validated full 3D unsteady Reynolds-averaged Navier–Stokes (URANS) solver. The loss model in the meanline model is calibrated by the full 3D RANS solver under the steady flow states. The unsteady turbine performance under different inlet pulsating flow conditions predicted by the model was compared with the results of the full 3D URANS solver. Good agreement between the two was obtained with a speed-up ratio of about 4 orders of magnitude (∼104) for the low-order model. The low-order model was then used to investigate the effect of different pulse wave amplitudes and frequencies on the turbine cycle averaged performance. For the cases tested, it was found that compared with quasi-steady performance, the unsteady effect of the pulsating flow has a relatively small impact on the cycle-averaged turbine power output and the cycle-averaged mass flow capacity, while it has a large influence on the cycle-averaged ideal power output and cycle-averaged efficiency. This is related to the wave dynamics inside the volute, and the detailed mechanisms responsible are discussed in this paper.

Considerations for Using 3D Pneumatic Probes in High Speed Axial Compressors

2002 ◽  
Author(s):  
Simon Coldrick ◽  
Paul Ivey ◽  
Roger Wells
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Pressure Probe ◽  
Probe Type ◽  
Calibration Data ◽  
Axial Compressors ◽  
Close Proximity ◽  
Multistage Axial Compressor ◽  
Preparatory Work

This paper describes preparatory work towards three dimensional flowfield measurements downstream of the rotor in an industrial, multistage, axial compressor, using a pneumatic pressure probe. The probe is of the steady state four hole cobra probe type. The design manufacture and calibration of the probe is described. CFD calculations have been undertaken in order to assess the feasability of using such a probe in the high speed compressor environment where space is limited. This includes effects of mounting the probe in close proximity to the downstream stator blades and whether it is necessary to adjust the calibration data to compensate for these effects.

A Low-Order Dynamic Model for Planar Solid Oxide Fuel Cells Using Online Iterative Computation

2008 ◽  
Vol 5 (4) ◽  
Author(s):  
Handa Xi ◽  
Jing Sun
Keyword(s):  
Energy Balance ◽  
Solid Oxide Fuel Cells ◽  
Computational Cost ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Order Model ◽  
Baseline Model ◽  
Iterative Computation ◽  
Balance Dynamics ◽  
Low Order

High-fidelity dynamic models of solid oxide fuel cells (SOFCs) capture the spatial distribution of key performance variables by considering the cells as distributed parameter systems. As such, they are often complex and require extensive computational resources. In this paper, driven by the need to support the control strategy development and system optimization, we develop a low-order SOFC model by approximating the mass and energy balance dynamics in the fuel and air bulk flows using quasi-static relations. However, due to the coupling between the quasi-static mass balance and current distribution, this approximation leads to a large set of coupled nonlinear algebraic equations that have to be solved online using iterative computation. In order to mitigate the computational cost involved, an efficient iterative algorithm is proposed to solve these equations. The new algorithm requires to iterate on only one variable—the cell voltage—to determine the current and flow compositions and their distributions. The low-order model with 16 states is compared to the baseline model, which has 160 states that incorporates fully the mass and energy balance dynamics. Simulations are performed to evaluate the model performance for both steady-state and transient operations, and to assess the computational cost associated with the low-order and full order models. It is shown that the low-order model closely matches the original baseline model, while the computation time is reduced by more than 50% compared to the baseline model.

Numerical and experimental analysis of rubbing–misalignment mixed fault in a dual-rotor system

2020 ◽  
pp. 095440622096858
Author(s):  
Wenzhen Xie ◽  
Chao Liu ◽  
Nanfei Wang ◽  
Dongxiang Jiang
Keyword(s):  
High Speed ◽  
Experimental Tests ◽  
Rotor System ◽  
Dynamic Responses ◽  
System Model ◽  
Speed Ratio ◽  
Rotor Systems ◽  
Frequency Components ◽  
Aero Engines ◽  
Misalignment Fault

Dual-rotor systems are widely used in aero-engines, in which rubbing–misalignment mixed faults are essential, as both are frequently observed and can occur simultaneously due to the harsh working conditions of high temperature, high pressure, and high speed. To analyze the vibration characteristics of such faults, a dual-rotor system model is established and dynamic responses under varying parameters of the dual-rotor system with rubbing–misalignment mixed fault are investigated. Through numerical simulation, the effects of speed ratio, rubbing clearance, and rubbing stiffness on the dual-rotor system with rubbing–misalignment fault are revealed. Meanwhile, experimental tests are conducted for validation, the main findings of which are that the characteristic frequency components could benefit the diagnosis of mixed faults in dual-rotor systems.

An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances

2012 ◽  
Author(s):  
Martin Lange ◽  
Konrad Vogeler ◽  
Ronald Mailach ◽  
Sergio Elorza-Gomez
Keyword(s):  
Flow Field ◽  
Experimental Verification ◽  
Gas Turbines ◽  
Three Dimensional ◽  
Performance Data ◽  
Axial Compressors ◽  
The Third ◽  
Overall Performance ◽  
Overall Efficiency ◽  
Aero Engines

Proportionally large relative radial clearances can be found within the rear stages of multistage axial compressors of gas turbines and aero engines, with significant impact on their efficiency. A new three-dimensional design for cantilevered stators in axial compressors is presented, with the aim of improving the overall efficiency and losses of rear stage vanes with large relative hub clearances. The new vane design comprises an unconventional dihedral, with special consideration to reduce the losses caused by the hub clearance vortex. The design was tested in a 4-stage low speed axial research compressor under rear stage conditions. The results are compared to the nominal design to validate the reduction of hub clearance losses and blockage. For both designs, the hub clearances over the third and fourth stator were varied from 1.5% up to 6.0% of span. Overall performance data and flow field traverses upstream and downstream of stator 3 and rotor 4 will be presented in this article in comparison with 3D CFD results.

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