Non-Axisymmetric End Wall Profiling in Transonic Compressors—Part I: Improving the Static Pressure Recovery at Off-Design Conditions by Sequential Hub and Shroud End Wall Profiling

2009 ◽  
Author(s):  
Steffen Reising ◽  
Heinz-Peter Schiffer
Keyword(s):  
Numerical Study ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Axial Compressor ◽  
Secondary Flows ◽  
Flow Solver ◽  
Axial Compressors ◽  
Transonic Compressor ◽  
End Wall

Secondary flows involving cross flow and three-dimensional separation phenomena in modern axial compressors at high stage loading contribute significantly to a reduction in overall efficiency. This two-part paper presents a numerical study on the potential aerodynamic benefits of using non-axisymmetric end walls in an axial compressor, involving both the rotor and the stator row. This first paper describes the sequential profiling of stator end walls in a transonic compressor at several operating points to suppress separation. An automated multi-objective optimizer connected to a 3-D RANS flow solver was used to find the optimal end wall geometries. As a design exercise, the stator hub end wall of Configuration I of the Darmstadt Transonic Compressor was first optimized at design conditions, keeping the shroud end wall constant. This led to an increase in efficiency of 1.8% due to the suppression of the hub-corner stall. However, this was accompanied by an increased area of reverse flow at the casing, which was even more distinct at off-design conditions near stall. The numerical surge limit of the datum axisymmetric design could no longer be reached and was then determined by the new separation close to the stator casing. A subsequent optimization of the shroud end wall was carried out using the improved profiled hub as the initial design. An operating point near stall with a strongly developed separation was chosen for this purpose. The second optimization resulted in a further improvement in the characteristic speed line over the entire off-design region. Although the shroud contour was designed at off-design conditions, the optimization gained an additional 0.03% in efficiency for the design point. The lower surge limit of the datum design could also be reached again, even at higher efficiency and pressure ratios. The investigations showed that end wall profiling in high loaded compressor stators can be considered as a good supplement to 3-D blading to control separation areas and improve the entire component’s characteristics.

Development of an Improved Streamline Curvature Approach for Transonic Axial Compressor

2016 ◽  
Author(s):  
Wu Xiaoxiong ◽  
Bo Liu ◽  
Shi Lei ◽  
Zhang Guochen ◽  
Mao Xiaochen
Keyword(s):  
Incidence Angle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Field Analysis ◽  
Design Stage ◽  
Axial Compressors ◽  
Transonic Compressor ◽  
Streamline Curvature

In this paper, an improved streamline curvature (SLC) approach is presented to obtain the internal flow fields and evaluate the performance of transonic axial compressors. The approach includes some semi-empirical correlations established based on previous literatures, such as minimum loss incidence angle model, deviation model and total pressure loss model. Several developments have been made in this paper for the purpose of considering the influences of three-dimensional (3D) flow in high-loaded multistage compressors with high accuracy. A revised deviation model is applied to predict the cascade with large deflection range. The method for predicting the shock loss is also discussed in detail. In order to validate the reliability of the approach, two test cases including a two-stage transonic fan and a three-stage transonic compressor are conducted. The overall performance and distribution of spanwise aerodynamic parameters are illustrated in this paper. Compared with both the experimental and computational fluid dynamic (CFD) data at design and a number of different off-design condition, the SLC results give reasonable characteristic curves. The validation demonstrates that this improved approach can serve as a fast and reliable tool for flow field analysis and performance prediction in preliminary design stage of axial compressors.

Three-Dimensional-Flow Theories for Axial Compressors and Turbines

1948 ◽  
Vol 159 (1) ◽  
pp. 255-268 ◽  
Author(s):  
A. D. S. Carter
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Physical Nature ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Three Dimensional Flow ◽  
Axial Compressors ◽  
Dimensional Flow ◽  
Blade Row

It has long been known that the energy losses occurring in an axial compressor or turbine cannot be fully accounted for by the skin-friction losses on the blades and annulus walls. The difference, usually termed secondary loss, is attributed to miscellaneous secondary flows which take place in the blade row. These flows both cause losses in themselves and modify the operating conditions of the individual blade sections, to the detriment of the overall performance. This lecture analyses the three-dimensional flow in axial compressors and turbines, so that, by appreciation of the factors involved, possible methods of improving the performance can readily be investigated. The origin of secondary flow is first examined for the simple case of a straight cascade. The physical nature of the flow, and theories which enable quantitative estimates to be made, are discussed at some length. Following this, the three-dimensional flow in an annulus with a stationary blade row is examined, and, among other things, the influence of radial equilibrium on the flow pattern is noted. All physical restrictions are then removed, and the major factors governing the three-dimensional flow in an actual machine are investigated as far as is possible with existing information, particular attention being paid to the influence of a non-uniform velocity profile, tip clearance, shrouding, and boundary layer displacement. Finally the various empirical factors used in design are discussed, and the relationships between them established.

A Method of Stall and Surge Prediction in Axial Compressors Based On Three-Dimensional Body-Force Model

2021 ◽  
Author(s):  
Hanxuan Zeng ◽  
Xinqian Zheng ◽  
Mehdi Vahdati
Keyword(s):  
Body Force ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Rotating Stall ◽  
The Body ◽  
Force Model ◽  
Computational Domain ◽  
Forward Flow ◽  
Axial Compressors

Abstract The occurrence of stall and surge in axial compressors has a great impact on the performance and reliability of aero-engines. Accurate and efficient prediction of the key features during these events has long been the focus of engine design processes. In this paper, a new body-force model that can capture the three-dimensional and unsteady features of stall and surge in compressors at a fraction of time required for URANS computations is proposed. To predict the rotating stall characteristics, the deviation of local airflow angle from the blade surface is calculated locally during the simulation. According to this local deviation, the computational domain is divided into stalled and forward flow regions, and the body-force field is updated accordingly; to predict the surge characteristics, the local airflow direction is used to divide the computational domain into reverse flow regions and forward flow regions. A single-stage axial compressor and a three-stage axial compressor are used to verify the proposed model. The results show that the method is capable of capturing stall and surge characteristics correctly. Compared to the traditional fully three-dimensional URANS method (fRANS), the simulation time for multi-stage axial compressors is reduced by 1 to 2 orders of magnitude.

Non-Axisymmetric End Wall Profiling in Transonic Compressors—Part II: Design Study of a Transonic Compressor Rotor Using Non-Axisymmetric End Walls—Optimization Strategies and Performance

2009 ◽  
Author(s):  
Steffen Reising ◽  
Heinz-Peter Schiffer
Keyword(s):  
Secondary Flow ◽  
Total Pressure ◽  
Cfd Simulation ◽  
Pressure Ratio ◽  
Cross Flow ◽  
Secondary Flows ◽  
Transonic Compressor ◽  
End Wall ◽  
Total Pressure Ratio ◽  
Isentropic Efficiency

Secondary flows involving cross flow at high stage loading in modern axial compressors contribute significantly to efficiency limits. This paper summarizes an approach to control end wall flow using non-axisymmetric end walls. The challenge is to find the optimal non-axisymmetric end wall shape that results in the largest gain in performance. An automated multi-objective optimizer connected to a 3-D RANS flow solver was used to design the end wall contour. The process chain was applied to the rotor hub end wall of Configuration I of the Darmstadt Transonic Compressor. Several optimization strategies involving different objective functions to be minimized and the corresponding performances were compared. The parameters considered within the optimization process were isentropic stage efficiency, pressure loss in the rotor, throat area and secondary kinetic energy (SKE). A parameter variation was undertaken, leading to the following observations: Strong penalties on SKE at the rotor outlet and moderate penalties on isentropic efficiency, throat area and pressure ratio led to the best design. Isentropic efficiency could be raised by 0.12%, SKE at the rotor exit was reduced while the total pressure ratio of the stage remained constant. Strong penalties on efficiency and pressure ratio, a moderate one on throat area and a small one on SKE at the rotor outlet all led to a smaller increase in efficiency: 0.06%. On the other hand, a slight raise in the total pressure ratio could be achieved. A third optimization, eliminating the restriction on the throat area, was carried out to see which benefit in performance could be achieved without this geometrical restriction. Since the throat areas of all optimized geometries differ slightly from the datum value, an estimation was derived to see the extent to which the end wall profiling and cross section enlargement contribute to the improvements. Finally, a method to display secondary flows in turbomachinery is introduced. A second CFD simulation is used to calculate the primary flow where the hub end wall is defined as an Euler wall to avoid the end wall boundary layer and so eliminate the cause for some of the secondary flow mechanisms. This method clearly shows how the characteristics of secondary flow can be positively influenced by using non-axisymmetric end walls.

scholarly journals Simulation of Casing Treatments of a Transonic Compressor Stage

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
M. Hembera ◽  
H.-P. Kau ◽  
E. Johann
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Flow Solver ◽  
Stall Margin ◽  
Transonic Compressor ◽  
Flow Mechanisms ◽  
Multistage Compressor ◽  
Casing Treatments

This article presents the study of casing treatments on an axial compressor stage for improving stability and enhancing stall margin. So far, many simulations of casing treatments on single rotor or rotor-stator configurations were performed. But as the application of casing treatments in engines will be in a multistage compressor, in this study, the axial slots are applied to a typical transonic first stage of a high-pressure 4.5-stage compressor including an upstream IGV, rotor, and stator. The unsteady simulations are performed with a three-dimensional time accurate Favre-averaged Navier-stokes flow solver. In order to resolve all important flow mechanisms appearing through the use of casing treatments, a computational multiblock grid consisting of approximately 2.4 million nodes was used for the simulations. The configurations include axial slots in 4 different variations with an axial extension ranging into the blade passage of the IGV. Their shape is semicircular with no inclination in circumferential direction. The simulations proved the effectiveness of casing treatments with an upstream stator. However, the results also showed that the slots have to be carefully positioned relative to the stator location.

The Design, Development and Evaluation of 3D Aerofoils for High Speed Axial Compressors: Part 2 — Simulation and Comparison With Experiment

2005 ◽  
Author(s):  
G. Woollatt ◽  
D. Lippett ◽  
P. C. Ivey ◽  
P. Timmis ◽  
B. A. Charnley
Keyword(s):  
Collaborative Design ◽  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Loss Reduction ◽  
Test Results ◽  
Design Development ◽  
Axial Compressors ◽  
Quantitative Basis ◽  
End Wall

The focus of this paper is to report on measurements from and simulation of Cranfield University’s 3-stage high-speed axial compressor test rig. This newly built rig is supported by European Commission funding and has tested a set of conventionally stacked 2D rotor and stator blades (Reference 1). The results were used to evaluate and to assess the performance of several commercially available CFD codes leading to the collaborative design of an advanced three-dimensional blade set. The philosophy behind the advanced design is described. The datum test results show that the state of the art, highly loaded, datum compressor is well matched with limited potential for loss reduction. A comparison is made between the measured results and a series of numerical analyses using the various CFD codes. Although the codes showed reasonable qualitative agreement with each other and the measured data, there were significant differences in the predicted performance of the datum build. Further the codes were unable to grade candidate redesigns consistently on a quantitative basis and therefore increased the difficulty of selecting suitable ‘3d’ features. Generic studies involving sweep, lean and recambering are used to evolve a design philosophy for the advanced three-dimensional design. Over cambering of the end-wall sections, coupled with a suitable stack of the blades, enables the blade count to be reduced. In the presence of a clearance combinations of sweep and lean are used to modify the loading in the clearance gap, thereby influencing the associated losses. The application of three-dimensional features redistributes the flow. The opportunity is therefore taken to rematch the sections based on the predicted results of the CFD codes. The above philosophy is used in the redesign of the datum compressor. Overall characteristics and exit traverse results from the test of the advanced build are compared to those from the datum build.

Numerical Investigation on the Effect of Vortex Generator on Axial Compressor Performance

2014 ◽  
Author(s):  
Ruchika Agarwal ◽  
Anand Dhamarla ◽  
Sridharan R. Narayanan ◽  
Shraman N. Goswami ◽  
Balamurugan Srinivasan
Keyword(s):  
Cross Flow ◽  
Axial Compressor ◽  
Vortex Generator ◽  
Side Surface ◽  
Suction Side ◽  
Test Case ◽  
Stall Margin ◽  
Layer Flow ◽  
Flow Effects ◽  
End Wall

The performance of the compressor blade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as corner flow separation between the wall and the blade. The present work is focused on the studying the effects of Vortex Generator (VG) on NASA Rotor 37 test case using Computational Fluid Dynamics (CFD). VG helps in controlling the inception of the stall by generating vortices and energizes the low momentum boundary layer flow which enhances the rotor performance. Three design configuration namely, Counter-rotating, Co-rotating and Plow configuration VG are selected based on the improved aerodynamic performance discussed in reference [1]. These VG are located at 90% span and 42% chord on suction side surface of the blade. Among the three configurations, the first configuration has greater impact on the end wall cross flow and flow deflection which resulted in enhanced numerical stall margin of 5.4% from baseline. The reasons for this numerical stall margin improvement are discussed in detail.

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

Compressor Performance 2D Modelling at Reverse Flow Conditions

2010 ◽  
Author(s):  
L. Gallar ◽  
I. Tzagarakis ◽  
V. Pachidis ◽  
R. Singh
Keyword(s):  
Experimental Data ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Engine Performance ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Compressor Surge ◽  
Compressor Performance ◽  
Shaft Failure

After a shaft failure the compression system of a gas turbine is likely to surge due to the heavy vibrations induced on the engine after the breakage. Unlike at any other conditions of operation, compressor surge during a shaft over-speed event is regarded as desirable as it limits the air flow across the engine and hence the power available to accelerate the free turbine. It is for this reason that the proper prediction of the engine performance during a shaft over-speed event claims for an accurate modelling of the compressor operation at reverse flow conditions. The present study investigates the ability of the existent two dimensional algorithms to simulate the compressor performance in backflow conditions. Results for a three stage axial compressor at reverse flow were produced and compared against stage by stage experimental data published by Gamache. The research shows that due to the strong radial fluxes present over the blades, two dimensional approaches are inadequate to provide satisfactory results. Three dimensional effects and inaccuracies are accounted for by the introduction of a correction parameter that is a measure of the pressure loss across the blades. Such parameter is tailored for rotors and stators and enables the satisfactory agreement between calculations and experiments in a stage by stage basis. The paper concludes with the comparison of the numerical results with the experimental data supplied by Day on a four stage axial compressor.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

Sign in / Sign up

Export Citation Format

Share Document