Numerical investigation of total temperature distortion problem in a multistage fan based on body force approach

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jin Guo ◽  
Jun Hu ◽  
Baofeng Tu
Keyword(s):  
Steady State ◽  
Total Pressure ◽  
High Speed ◽  
Large Scale ◽  
Body Force ◽  
Present Model ◽  
Force Model ◽  
Flow Feature ◽  
Total Temperature ◽  
Large Scale Flow

AbstractThis paper applies a body force model developed recently to investigate the interaction between total temperature distortion and a multistage fan. The off-design performance of the fan shows the reasonable predicting accuracy and supports the present model is applicable for high-speed multistage machines. The transfer behaviors of 90° steady-state circumferential total temperature distortion as well as combined total pressure and total temperature distortion in the multistage environment are captured successfully by the model. The mechanism of the phase shift of the high temperature sector is discussed by the model to advance the understanding of the total temperature distortion problem. The results reveal that the large-scale flow feature of total temperature distortion in the multistage environment can be capably quantified by the present body force model with the acceptable computational consumption.

Calculation of Flow Instability Inception in High Speed Axial Compressors

2014 ◽  
Author(s):  
Xiaohua Liu ◽  
Yanpei Zhou ◽  
Xiaofeng Sun ◽  
Dakun Sun
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Body Force ◽  
Present Model ◽  
Flow Instability ◽  
Tip Clearance ◽  
Force Model ◽  
Fine Grid ◽  
Stall Margin ◽  
Onset Point

This paper applies a theoretical model developed recently to calculate the flow instability inception point in axial high speed compressors system. After the mean flow field is computed by steady CFD simulation, a body force approach, which is a function of flow field data and comprises of one inviscid part and the other viscid part, is taken to duplicate the physical sources of flow turning and loss. Further by applying appropriate boundary conditions and spectral collocation method, a group of homogeneous equations will yield from which the stability equation can be derived. The singular value decomposition method is adopted over a series of fine grid points in frequency domain, and the onset point of flow instability can be judged by the imaginary part of the resultant eigenvalue. The first assessment is to check the applicability of the present model on calculating the stall margin of one single stage transonic compressors at 85% rotational speed. The reasonable prediction accuracy validates that this model can provide an unambiguous judgment on stall inception without numerous requirements of empirical relations of loss and deviation angle. It could possibly be employed to check over-computed stall margin during the design phase of new high speed fan/compressors. The following validation case is conducted to study the nontrivial role of tip clearance in rotating stall, and a parameter study is performed to investigate the effects of end wall body force coefficient on stall onset point calculation. It is verified that the present model could qualitatively predict the reduced stall margin by assuming a simplified body force model which represents the response of a large tip clearance on the unsteady flow field.

Calculation of Flow Instability Inception in High Speed Axial Compressors Based on an Eigenvalue Theory

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Xiaohua Liu ◽  
Yanpei Zhou ◽  
Xiaofeng Sun ◽  
Dakun Sun
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Body Force ◽  
Present Model ◽  
Flow Instability ◽  
Tip Clearance ◽  
Force Model ◽  
Fine Grid ◽  
Stall Margin ◽  
Onset Point

This paper applies a theoretical model developed recently to calculate the flow instability inception point in axial high speed compressors system with tip clearance. After the mean flow field is computed by 3D steady computational fluid dynamics (CFD) simulation, a body force approach, which is a function of flow field data and comprises of one inviscid part and the other viscid part, is taken to duplicate the physical sources of flow turning and loss. Further by applying appropriate boundary conditions and spectral collocation method, a group of homogeneous equations will yield from which the stability equation can be derived. The singular value decomposition (SVD) method is adopted over a series of fine grid points in frequency domain, and the onset point of flow instability can be judged by the imaginary part of the resultant eigenvalue. The first assessment is to check the applicability of the present model on calculating the stall margin of one single stage transonic compressors at 85% rotational speed. The reasonable prediction accuracy validates that this model can provide an unambiguous judgment on stall inception without numerous requirements of empirical relations of loss and deviation angle. It could possibly be employed to check overcomputed stall margin during the design phase of new high speed compressors. The following validation case is conducted to study the nontrivial role of tip clearance in rotating stall, and a parameter study is performed to investigate the effects of end wall body force coefficient on stall onset point calculation. It is verified that the present model could qualitatively predict the reduced stall margin by assuming a simplified body force model which represents the response of a large tip clearance on the unsteady flow field.

Unsteady Three-Dimensional Analysis of Inlet Distortion in a Transonic Fan

2006 ◽  
Author(s):  
Peng Sun ◽  
Guotal Feng
Keyword(s):  
Shock Wave ◽  
Total Pressure ◽  
Large Scale ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Inlet Distortion ◽  
Flow Loss ◽  
Large Scale Vortex ◽  
Total Temperature ◽  
Transonic Fan

A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out using "Fluent-parallel" in a parallel supercomputer. The numerical simulation focused on a transonic fan with inlet square wave total pressure distortion and the analysis of result consisted of three aspects. The first was about inlet parameters redistribution and outlet total temperature distortion induced by inlet total pressure distortion. The pattern and causation of flow loss caused by pressure distortion in rotor were analyzed secondly. It was found that the influence of distortion was different at different radial positions. In hub area, transportation-loss and mixing-loss were the main loss patterns. Distortion not only complicated them but enhanced them. Especially in stator, inlet total pressure distortion induced large-scale vortex, which produced backflow and increased the loss. While in casing area, distortion changed the format of shock wave and increased the shock loss. Finally, the format of shock wave and the hysteresis of rotor to distortion were analyzed in detail.

Crackle Noise in Heated Supersonic Jets

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Joseph W. Nichols ◽  
Sanjiva K. Lele ◽  
Frank E. Ham ◽  
Steve Martens ◽  
John T. Spyropoulos
Keyword(s):  
Large Scale ◽  
Supersonic Jet ◽  
Supersonic Jets ◽  
Scale Model ◽  
Positive Pressure ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Total Temperature ◽  
Large Scale Flow ◽  
Large Eddies

Crackle noise from heated supersonic jets is characterized by the presence of strong positive pressure impulses resulting in a strongly skewed far-field pressure signal. These strong positive pressure impulses are associated with N-shaped waveforms involving a shocklike compression and, thus, is very annoying to observers when it occurs. Unlike broadband shock-associated noise which dominates at upstream angles, crackle reaches a maximum at downstream angles associated with the peak jet noise directivity. Recent experiments (Martens et al., 2011, “The Effect of Chevrons on Crackle—Engine and Scale Model Results,” Proceedings of the ASME Turbo Expo, Paper No. GT2011-46417) have shown that the addition of chevrons to the nozzle lip can significantly reduce crackle, especially in full-scale high-power tests. Because of these observations, it was conjectured that crackle is associated with coherent large scale flow structures produced by the baseline nozzle and that the formation of these structures are interrupted by the presence of the chevrons, which leads to noise reduction. In particular, shocklets attached to large eddies are postulated as a possible aerodynamic mechanism for the formation of crackle. In this paper, we test this hypothesis through a high-fidelity large-eddy simulation (LES) of a hot supersonic jet of Mach number 1.56 and a total temperature ratio of 3.65. We use the LES solver CHARLES developed by Cascade Technologies, Inc., to capture the turbulent jet plume on fully-unstructured meshes.

The Dynamic Analysis of High-Speed Energy Storage Flywheel Rotor System

2013 ◽  
Vol 770 ◽  
pp. 78-83
Author(s):  
Xiu Hua Zhang ◽  
Guang Xi Li ◽  
Long Nie
Keyword(s):  
Steady State ◽  
Energy Storage ◽  
High Speed ◽  
Transient Analysis ◽  
Critical Speed ◽  
Large Scale ◽  
Simulation Analysis ◽  
Rotor System ◽  
Analysis Method ◽  
Flywheel Rotor

This article aims at large-scale energy storage flywheel rotor system, obtaining the dynamic characteristics. Through theoretical analysis, and after doing a simulation analysis for a given flywheel rotor on the 0-20000 RPM, getting the flywheel rotor critical speed, the transient analysis and imbalance response. The system is in steady state at runtime according to the analysis results. Providing also certain theory basis for study of flywheel rotor system according to the analysis method .

Proper Orthogonal Decomposition Analysis of Non-Swirling Turbulent Stratified and Premixed Methane/Air Flames

2014 ◽  
Author(s):  
M. Mustafa Kamal ◽  
Christophe Duwig ◽  
Saravanan Balusamy ◽  
Ruigang Zhou ◽  
Simone Hochgreb
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
High Speed ◽  
Large Scale ◽  
Bluff Body ◽  
Decomposition Analysis ◽  
Orthogonal Decomposition ◽  
Stereoscopic Particle Image Velocimetry ◽  
Large Scale Flow ◽  
Proper Orthogonal

This paper reports proper orthogonal decomposition (POD) analyses for the velocity fields measured in a test burner. The Cambridge/Sandia Stratified Swirl Burner has been used in various studies as a benchmark for high resolution scalar and velocity measurements, for comparison with numerical model prediction. Flow field data was collected for a series of bluff-body stabilized premixed and stratified methane/air flames at turbulent, globally lean conditions (ϕ = 0.75) using high speed stereoscopic particle image velocimetry (HS-SPIV). In this paper, a modal analysis was performed to identify the large scale flow structures and their impact on the flame dynamics. The high speed PIV system was operated at 3 kHz to acquire a series of 4096 sequential flow field images both for reactive and non-reactive cases, sufficient to follow the large-scale spatial and temporal evolution of flame and flow dynamics. The POD analysis allows identification of vortical structures, created by the bluff body, and in the shear layers surrounding the stabilization point. In addition, the analysis reveals that dominant structures are a strong function of the mixture stratification in the flow field. The dominant energetic modes of reactive and non-reactive flows are very different, as the expansion of gases and the high temperatures alter the unstable modes and their survival in the flow.

Numerical modelling of turbulent flow in a combustion tunnel

1982 ◽  
Vol 304 (1484) ◽  
pp. 303-325 ◽  
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Speed ◽  
Large Scale ◽  
Numerical Technique ◽  
Vortex Method ◽  
Reacting Flow ◽  
Exothermic Process ◽  
Schlieren Photography ◽  
Large Scale Flow

A numerical technique is presented for the analysis of turbulent flow associated with combustion. The technique uses Chorin’s random vortex method (r.v.m .), an algorithm capable of tracing the action of elementary turbulent eddies and their cumulative effects without imposing any restriction upon their motion. In the past, the r.v.m . has been used with success to treat non-reacting turbulent flows, revealing in particular the mechanics of large-scale flow patterns, the so-called coherent structures. Introduced here is a flame propagation algorithm , also developed by Chorin, in conjunction with volume sources modelling the mechanical effects of the exothermic process of combustion. As an illustration of its use, the technique is applied to flow in a combustion tunnel w here the flame is stabilized by a back-facing step. Solutions for both non-reacting and reacting flow fields are obtained. Although these solutions are restricted by a set of far-reaching idealizations, they nonetheless mimic quite satisfactorily the essential features of turbulent combustion in a lean propane—air mixture that were observed in the laboratory by means of high speed schlieren photography.

scholarly journals Innovations in Body Force Modeling of Transonic Compressor Blade Rows

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
David J. Hill ◽  
Jeffrey J. Defoe
Keyword(s):  
Total Pressure ◽  
Body Force ◽  
Computational Cost ◽  
Pressure Rise ◽  
The Body ◽  
Force Model ◽  
Axial Fan ◽  
Compressor Blades ◽  
Time Resolved ◽  
Transonic Compressor

Aeroengine fans and compressors increasingly operate subject to inlet distortion in the transonic flow regime. In this paper, innovations to low-order numerical modeling of fans and compressors via volumetric source terms (body forces) are presented. The approach builds upon past work to accommodate any axial fan/compressor geometry and ensures accurate work input and efficiency prediction across a range of flow coefficients. In particular, the efficiency drop-off near choke is captured. The model for a particular blade row is calibrated using data from single-passage bladed computations. Compared to full-wheel unsteady computations which include the fan/compressor blades, the source term model approach can reduce computational cost by at least two orders of magnitude through a combination of reducing grid resolution and, critically, eliminating the need for a time-resolved approach. The approach is applied to NASA stage 67. For uniform flow, at 90% corrected speed and peak-efficiency, the body force model is able to predict the total-to-total pressure rise coefficient of the stage to within 1.43% and the isentropic efficiency to within 0.03%. With a 120∘ sector of reduced inlet total pressure, distortion transfer through the machine is well-captured and the associated efficiency penalty predicted with less than 2.7% error.

A New Loss Generation Body Force Model for Fan/Compressor Blade Rows: Application to Uniform and Non-Uniform Inflow in Rotor 67

2021 ◽  
pp. 1-41
Author(s):  
Syamak Pazireh ◽  
Jeff Defoe
Keyword(s):  
Body Force ◽  
Present Model ◽  
Axial Compressor ◽  
Computation Time ◽  
Pressure Profile ◽  
Design Stage ◽  
Force Model ◽  
Force Modeling ◽  
Cost Of Time ◽  
Isentropic Efficiency

Abstract Despite advances in computational power, the cost of time-accurate flows in axial compressor and fan stages with spatially non-uniform inflow is still too high for design-stage use in industry. Body force modeling reduces the computation time to practical levels, mainly by reducing the problem to a steady one. These computations are important to determine efficiency penalties associated with non-uniform inflows. Previous studies of body force methods have, in most cases, relied on computations with the presence of the blades to calibrate loss models. In some recent studies, uncalibrated models have been used, but such models can drop off in accuracy at conditions where separation would occur on the blade surfaces. In this paper, a neural network-based loss model introduced in a recent paper by the authors is implemented for NASA rotor 67 for both uniform and non-uniform inflow conditions. For uniform inflow, the spanwise trend of entropy variation is generally captured with the new body force model. Although there are discrepancies at some span fractions, the present model generally predicts the compressor's isentropic efficiency to within 3% compared to bladed RANS simulations. For non-uniform inflow, we consider a stagnation pressure profile representative of boundary layer ingestion. The results show that the region of maximum entropy generation is captured by the present model and the prediction of isentropic efficiency penalty due to the non-uniform inflow is only 0.2 points less than that determined from bladed computations.

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