scholarly journals Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
John Leggett ◽  
Edward Richardson ◽  
Stephan Priebe ◽  
Aamir Shabbir ◽  
Vittorio Michelassi ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Mechanical Work ◽  
Navier Stokes ◽  
Operating Pressure ◽  
Compressor Stage ◽  
Compressor Cascade ◽  
Loss Analysis ◽  
Dead State ◽  
Thermodynamic Performance ◽  
Pressure Compressor

Abstract Loss analysis is a valuable technique for improving the thermodynamic performance of turbomachines. Analyzing loss in terms of the “mechanical work potential” (Miller, R.J., ASME Turbo Expo 2013, GT2013-95488) provides an instantaneous and local account of the thermal and aerodynamic mechanisms contributing to the loss of thermodynamic performance. This study develops the practical application of mechanical work potential loss analysis, providing the mathematical formulations necessary to perform loss analysis using practical Reynolds-averaged Navier–Stokes (RANS) or large eddy simulations (LES). The analysis approach is demonstrated using RANS and LES of a linear compressor cascade, both with and without incoming wakes. Spatial segmentation is used to attribute loss contributions to specific regions of the flow, and phase-averaging is performed in order to associate the variation of different loss contributions with the periodic passage of wakes through the cascade. For this un-cooled linear cascade, viscous dissipation is the dominant source of loss. The analysis shows that the contribution of the viscous reheat effect depends on the operating pressure of the compressor stage relative to the ambient “dead state” pressure—implying that the optimal blade profile for a low-pressure compressor stage may be different from the optimal profile for a high-pressure compressor stage in the same engine, even if the operating conditions for both stages are dynamically similar.

scholarly journals Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential

2019 ◽  
Author(s):  
John Leggett ◽  
Edward Richardson ◽  
Stephan Priebe ◽  
Aamir Shabbir ◽  
Vittorio Michelassi ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Mechanical Work ◽  
Navier Stokes ◽  
Operating Pressure ◽  
Compressor Stage ◽  
Compressor Cascade ◽  
Loss Analysis ◽  
Dead State ◽  
Thermodynamic Performance ◽  
Pressure Compressor

Abstract Loss analysis is a valuable technique for improving the thermodynamic performance of turbomachines. Analysing loss in terms of the ‘mechanical work potential’ (Miller, R.J., ASME Turbo Expo 2013, GT2013-95488) provides an instantaneous and local account of the thermal and aerodynamic mechanisms contributing to the loss of thermodynamic performance. This study develops the practical application of mechanical work potential loss analysis, providing the mathematical formulations necessary to perform loss analysis using practical Reynolds-Averaged Navier-Stokes (RANS) or Large Eddy Simulations (LES). The analysis approach is demonstrated using RANS and LES of a linear compressor cascade, both with and without incoming wakes. Spatial segmentation is used to attribute loss contributions to specific regions of the flow, and phase-averaging is performed in order to associate the variation of different loss contributions with the periodic passage of wakes through the cascade. For this un-cooled linear cascade, viscous dissipation is the dominant source of loss. The analysis shows that the contribution of the viscous reheat effect depends on the operating pressure of the compressor stage relative to the ambient ‘dead state’ pressure — implying that the optimal blade profile for a low-pressure compressor stage may be different from the optimal profile for a high-pressure compressor stage in the same engine, even if the operating conditions for both stages are dynamically-similar.

Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Lanxin Sun ◽  
Qun Zheng ◽  
Yijin Li ◽  
Rakesh Bhargava
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Water Flow Rate ◽  
Separated Flow ◽  
Operating Conditions ◽  
Compressor Stage ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Wet Compression

The effects of wet compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.

Detailed Investigation of RANS and LES Predictions of Loss Generation in an Axial Compressor Cascade at Off Design Incidences

2016 ◽  
Author(s):  
John Leggett ◽  
Stephan Priebe ◽  
Richard Sandberg ◽  
Vittorio Michelassi ◽  
Aamir Shabbir
Keyword(s):  
Best Practice ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Free Stream Turbulence ◽  
Loss Analysis ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Prediction Techniques

In the design of modern jet engines the need for accurate loss prediction techniques is ever present. The most common tool currently in use is Reynolds Averaged Navier-Stokes model which provides good estimation at design conditions but can struggle with off design conditions. With accuracy being such an important requirement, an alternative method such as Large Eddy Simulation presents an opportunity to improve and assess the off design performance. Although still limited by computational resources, the use of Large Eddy Simulations in conjunction with more detailed loss analysis methods forms a powerful tool for assessing and improving current Reynolds Averaged Navier-Stokes techniques. The simulations performed here are an incidence sweep at off-design conditions with free stream turbulence. The results of the two methodologies are compared with the use of loss breakdown analysis and the best practice of applying the loss breakdown technique to compressors is outlined.

Analytical Maps of Aerodynamic Damping as a Function of Operating Condition for a Compressor Profile

2006 ◽  
Author(s):  
Paul J. Petrie-Repar ◽  
Andrew McGhee ◽  
Peter A. Jacobs ◽  
Rowan Gollan
Keyword(s):  
Inviscid Flow ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Operating Condition ◽  
Flow Solver ◽  
Aerodynamic Damping ◽  
Wide Range ◽  
Contour Plots ◽  
Standard Configuration

In this paper, analytical maps of aerodynamic damping for a two-dimensional compressor cascade (Standard Configuration 10) are presented. The maps are shown as contour plots of the aerodynamic damping as a function of operating condition. The aerodynamic dampings were calculated by a linearized Navier-Stokes flow solver. The flutter boundaries over a wide range of operating conditions are clearly shown on the damping maps and were found to be strongly dependent on the mode frequency and the mode shape. Extremely low values of negative aerodynamic damping were predicted for some off-design operating conditions where flow separation occurred. A damping map was also constructed based on inviscid flow simulations. There were differences in the viscous and inviscid flutter boundaries particularly at off-design inflow angles. The extremely low values of negative aerodynamic damping were only predicted by the viscous simulations and not the inviscid simulations.

Multiphase Flow Simulation of Subcooled Boiling Using the N-Phase Approach in TransAT

2013 ◽  
Author(s):  
S. Thomas ◽  
C. Narayanan ◽  
D. Lakehal ◽  
Y. Gong
Keyword(s):  
Phase Change ◽  
Flow Simulation ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Operating Pressure ◽  
Subcooled Boiling ◽  
Convective Boiling ◽  
Pressurized Water ◽  
Recent Developments ◽  
Water Reactors

In Pressurized Water Reactors (PWR), convective boiling occurs at the heated walls, which are superheated while liquid bulk is subcooled at a given operating pressure. The physical modeling of the phenomenon is complex, as it requires consideration of phase change and turbulence. The combinations of Reynolds-Averaged Navier Stokes (RANS) and wall boiling models have found moderate success in the past. Succesful modeling depends on the nature of the problem and its operating conditions, the manner of the model implementation and the quality of the computational platform. In the present work recent developments executed in the TransAT code for subcooled boiling are demonstrated. To better capture the phase change, the modified mixture approach is employed where the temperature of the N-phases are resolved separately. This method has been more suitable for phase-change problems, when compared to a single mixture temperature. To check the validity of the modeling, results are evaluated against the DEBORA experiments carried out at CEA Grenoble.

The Effects of Wet Compression on the Separated Flow in a Compressor Stage

2008 ◽  
Author(s):  
Lanxin Sun ◽  
Yijin Li ◽  
Qun Zheng ◽  
Rakesh Bhargava
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Water Flow Rate ◽  
Separated Flow ◽  
Flow Region ◽  
Operating Conditions ◽  
Compressor Stage ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Wet Compression

Effects of wet compression on the flow field within a compressor stage, particularly in presence of the separated flow region are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a Computational Fluid Dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated.

Experimental and numerical investigation of the flow field in a high-pressure centrifugal compressor impeller near surge

2009 ◽  
Vol 223 (6) ◽  
pp. 657-666 ◽  
Author(s):  
N Bulot ◽  
I Trébinjac ◽  
X Ottavy ◽  
P Kulisa ◽  
G Halter ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Laser Doppler Anemometry ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Compressor Stage ◽  
Peak Efficiency ◽  
Vaned Diffuser

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. The present article focuses on the results obtained within the impeller, at an operating condition close to the surge of the compressor. The experimental results were obtained from a laser Doppler anemometry investigation. Unsteady numerical simulations of the compressor stage were performed using a three-dimensional Reynolds-averaged Navier—Stokes code with a phase-lagged technique, at both peak efficiency and close to surge operating conditions. A good agreement between the experiments and simulations were obtained, which justifies the use of the computational fluid dynamics results for the comparison of the flow field at both operating conditions (peak efficiency and near surge). Even if the change in flow field within the impeller from peak efficiency to near surge looked to be gradual, an overall rotation of the whole flow in the blade passages led to a non-homogeneous flow at the impeller exit in terms of angle and velocity level. Therefore, the vaned diffuser has to tolerate upstream flows, which are all the more distorted as the operating point moves towards surge.

Effect of operating conditions on rejection of anionic pollutants in the water environment by nanofiltration especially in very low pressure range

1996 ◽  
Vol 34 (9) ◽  
pp. 149-156 ◽  
Author(s):  
C. Ratanatamskul ◽  
K. Yamamoto ◽  
T. Urase ◽  
S. Ohgaki
Keyword(s):  
Water Environment ◽  
Chloride Ions ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Operating Pressure ◽  
Nanofiltration Membranes ◽  
Single Solution ◽  
Crossflow Velocity ◽  
Membrane Type ◽  
New Generation

The recent development of new generation LPRO or nanofiltration membranes have received attraction for application in the field of wastewater and water treatment through an increasingly stringent regulation for drinking purpose and water reclamation. In this research, the application on treatment of anionic pollutants (nitrate, nitrite, phosphate, sulfate and chloride ions) have been investigated as functions of transmembrane pressure, crossflow velocity and temperature under very much lower pressure operation range (0.49 to 0.03 MPa) than any other previous research used to do. Negative rejection was also observed under very much low range of operating pressure in the case of membrane type NTR-7250. Moreover, the extended Nernst-Planck model was used for analysis of the experimental data of the rejection of nitrate, nitrite and chloride ions in single solution by considering effective charged density of the membranes.

Multiscale Partially Averaged Navier Stokes Approach for the Prediction of Flow in Linear Compressor Cascade With Moving Casing

2011 ◽  
Author(s):  
Domenico Borello ◽  
Giovanni Delibra ◽  
Franco Rispoli
Keyword(s):  
Turbulence Models ◽  
Navier Stokes ◽  
Test Case ◽  
Compressor Cascade ◽  
Preliminary Assessment ◽  
Linear Compressor ◽  
Tip Leakage ◽  
Experimental Campaign ◽  
Elliptic Relaxation ◽  
Linear Compressor Cascade

In this paper we present an innovative Partially Averaged Navier Stokes (PANS) approach for the simulation of turbomachinery flows. The elliptic relaxation k-ε-ζ-f model was used as baseline Unsteady Reynolds Averaged Navier Stokes (URANS) model for the derivation of the PANS formulation. The well established T-FlowS unstructured finite volume in-house code was used for the computations. A preliminary assessment of the developed formulation was carried out on a 2D hill flow that represents a very demanding test case for turbulence models. The turbomachinery flow here investigated reproduces the experimental campaign carried out at Virginia Tech on a linear compressor cascade with tip leakage. Their measurements were used for comparisons with numerical results. The predictive capabilities of the model were assessed through the analysis of the flow field. Then an investigation of the blade passage, where experiments were not available, was carried out to detect the main loss sources.

Numerical Investigation of the Solidity Effect on Linear Compressor Cascades

2014 ◽  
Author(s):  
J. Sans ◽  
M. Resmini ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Numerical Investigation ◽  
State Of The Art ◽  
Leading Edge ◽  
Operating Conditions ◽  
Compressor Cascade ◽  
Minimum Loss ◽  
Low Speed ◽  
High Mach ◽  
The Stability ◽  
The Impact

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on low-speed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-of-the-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and compared with existing correlations for both configurations and various Mach numbers that have been selected in order to match typical booster stall and choke operating conditions. The emphasis is set on the minimum loss performance at mid-span. The impact of the solidity on the operating range and the stability of the cascade are also studied.

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