Numerical Investigation of the Aerodynamic Performance of Hybrid Aerofoils in a 1.5-Stage Low-Speed Compressor

2021 ◽  
Author(s):  
Jannik Eckel ◽  
Volker Gümmer
Keyword(s):  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Limiting Factors ◽  
Stall Inception ◽  
Low Speed ◽  
Flow Phenomena

Abstract This paper describes the numerical investigation of hybrid aerofoils in a 1.5-stage low-speed compressor, which in its baseline configuration features a conventional rotor and a tandem stator. Both of these are eventually replaced by hybrid aerofoils, using the initial tandem blade profile geometry around mid-span. In this course of design investigations a pure tandem rotor was also generated and analysed as the initial geometry of the hybrid rotor. The aerodynamic design and performance of the tandem rotor and the hybrid aerofoils will be discussed in this paper. The numerical analysis is aimed at understanding the secondary flow phenomena and limiting factors of the working range of the reference stage. Based on this knowledge, the advantages of the hybrid aerofoil design will be discussed. On one hand, the origin and development of three-dimensional flow structures near the endwall regions of the rear vane of the tandem stator are investigated in detail, as they appear to play a major role at de-throttled operating conditions. On the other hand, the tip vortex leakage of the single rotor and the pure tandem rotor are considered, showing the tip vortex taking a major role in loss generation and stall inception at throttled operating conditions, and interacting with the tandem stator secondary flow phenomena at the casing. Both these performance-limiting factors can be addressed by implementing hybrid aerofoils. The paper presents and discusses the improvement of secondary flow loses and aerodynamic performance based on steady-state RANS simulations.

1997 Best Paper Award—Turbomachinery Committee: A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1998 ◽  
Vol 120 (3) ◽  
pp. 393-401 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Short Length ◽  
Operating Conditions ◽  
Length Scale ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms in a low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short length-scale disturbance known as a “spike,” and the second with a longer length-scale disturbance known as a “modal oscillation.” In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented that relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: Long length-scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed that explains the type of stall inception pattern observed in a particular compressor. Measurements from a single-stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1996 ◽  
Vol 118 (4) ◽  
pp. 835-843 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stator at several operating conditions. The flow field is found to be highly three dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier–Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

1997 ◽  
Author(s):  
T. R. Camp ◽  
I. J. Day
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Stability Criteria ◽  
Stall Inception ◽  
Low Speed ◽  
The Stability ◽  
Dimensional Instability

This paper presents a study of stall inception mechanisms a in low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short lengthscale disturbance known as a ‘spike’, and the second with a longer lengthscale disturbance known as a ‘modal oscillation’. In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented which relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: long lengthscale disturbances are related to a two-dimensional instability of the whole compression system, while short lengthscale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed which explains the type of stall inception pattern observed in a particular compressor. Measurements from a single stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

Application of Viscous Flow Computations for the Aerodynamic Performance of a Backswept Impeller at Various Operating Conditions

1988 ◽  
Vol 110 (3) ◽  
pp. 303-311 ◽  
Author(s):  
C. Hah ◽  
A. C. Bryans ◽  
Z. Moussa ◽  
M. E. Tomsho
Keyword(s):  
Experimental Data ◽  
Viscous Flow ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Phenomena ◽  
Overall Performance ◽  
Real Flow ◽  
Operating Points

Three-dimensional flowfields in a centrifugal impeller with backswept discharge at various operating points have been numerically investigated with a three-dimensional viscous flow code. Numerical results and experimental data were compared for the detailed flowfields and overall performance of the impeller at three operating conditions (optimum efficiency, choke, and near-surge conditions). The comparisons indicate that for engineering applications the numerical solution accurately predicts various complex real flow phenomena. The overall aerodynamic performance of the impeller is also well predicted at design and off-design conditions.

Experimental and Numerical Investigation of Stator Exit Flow Field of an Automotive Torque Converter

1994 ◽  
Author(s):  
B. V. Marathe ◽  
B. Lakshminarayana ◽  
Y. Dong
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Numerical Investigation ◽  
Three Dimensional ◽  
Axial Flow ◽  
Torque Converter ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Complex Flow ◽  
Rate Of Decay

The objective of this investigation is to understand the nature of the complex flow field inside each element of the torque converter through a systematic experimental and numerical investigation of the flow field. A miniature five-hole probe was used to acquire the data at the exit of the stat or at several operating conditions. The flow field is found to be highly three-dimensional with substantial flow deviations, and secondary flow at the exit of the stator. The secondary flow structure, caused by the upstream radial variation of the through flow, induces flow overturning near the core. Flow separation near the shell causes flow underturning in this region. The rate of decay of stator wake is found to be slower than that observed in the wakes of axial flow turbine nozzles. The flow predictions by a Navier-Stokes code are in good agreement with the pressure and the flow field measured at the exit of the stator at the design and the off-design conditions.

Numerical Investigation on the Effects of Self-Excited Tip Flow Unsteadiness and Blade Row Interactions on the Performance of a Low Speed Compressor Rotor

2008 ◽  
Author(s):  
Daniel Lee ◽  
Paul D. Orkwis ◽  
Fu-Lin Tsung ◽  
William Magnuszewski ◽  
Christopher Noll ◽  
...  
Keyword(s):  
Steady State ◽  
Numerical Investigation ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Tip Leakage Flow ◽  
Low Speed ◽  
Flow Unsteadiness ◽  
Compressor Rotor ◽  
Blade Row

A numerical investigation has been conducted to determine the effects of self-excited tip-leakage flow unsteadiness, upstream stator wakes, and downstream blade row interactions on the performance prediction of a low speed research compressor rotor. Calculations included a single blade-row rotor configuration as well as two multi-blade row configurations: one where the rotor was modeled with an upstream stator and a second where the rotor was modeled with a downstream stator. Steady-state and time accurate calculations were performed using a RANS solver and the results were compared with detailed experimental data at operating conditions corresponding to the compressor design point, near stall and a mid-point between the two. Differences in the performance predictions between the three configurations were then used to determine the effect of the upstream stator wakes and the downstream blade row interactions. Results obtained show that for this compressor with rather large tip clearance, time-accurate calculations are a vast improvement over steady-state calculations, but the upstream stator wakes and the downstream blade row interactions have only a small effect on the numerical solution. In this paper, changes in the rotor flow field due to the upstream and downstream stators are investigated and discussed to explain the limited impact of the stator wakes and downstream blade row interactions on this tip dominated flow. In addition, the unsteady nature of the rotor tip vortex at near stall conditions is discussed to explain the improvement of time accurate analysis over steady state computations.

Unsteady Modelling of the Tip Clearance Flow in an Inlet Vaned, Low-Speed Axial Fan: Deterministic Interactions of Stator Wakes and Tip Vortex Structures

2009 ◽  
Author(s):  
Jesu´s Manuel Ferna´ndez Oro ◽  
Katia Mari´a Argu¨elles Di´az ◽  
Carlos Santolaria Morros ◽  
Mo´nica Galdo Vega
Keyword(s):  
Three Dimensional ◽  
Vortex Structures ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Fan ◽  
Low Speed ◽  
Tip Leakage ◽  
The Impact

In last years, numerical modelling has reached a significant level of maturity in the analysis of axial turbomachinery flows. Full-unsteady, three-dimensional computations have been demonstrated as a powerful tool to characterize viscous phenomena on blade row interactions and blade passage structures. In particular, major effects have been focused on the study of deterministic fluctuations in order to quantify the impact of periodic unsteadiness on the time-averaged flow. An additional complexity concerns to the influence of the tip vortex structures on the deterministic patterns. Hence, some researchers have advanced experimental evidences on the contribution of tip leakage flow to the time-resolved distributions. Tip vortex, shedding energy at a wide range of scales, has been shown to be significant in the description of the spanwise momentum transfer and the appearance of mixing losses. Recently, the authors have investigated the impact of the tip vortex on the passage flow structures of a jet fan with symmetric blades. This work revealed valuable information about tip vortex transport in low-speed axial turbomachinery and demonstrated the ability of commercial codes to simulate three-dimensional, vortical structures with high accuracy. The present paper takes advantage of the same numerical methodology to highlight the influence of the deterministic correlations that describe the stator-rotor interaction on the tip vortex in a single-stage axial fan. Up to now, few works addressing deterministic contributions over the tip leakage flow are available in the literature, so more investigation is needed to understand the complexity of these physical mechanisms. Our contribution to the topic is based on a 3D, unsteady numerical simulation of the flow within a reduced periodic domain of the full-annulus axial stage, composed by only 3-vane and 2-blade passages. This simplification allows an enhancement of the grid density when massive parallel computations are employed. Also, comparison with experimental data measured using hot-wire anemometry is provided to validate the numerical model. The results show how the non-uniformities of the stator wake-core structure in the relative frame of reference are conditioning the tip leakage flow, addressing the influence of the operating conditions or the interrow spacing. The final objective is to provide levels of instabilities in the tip vortex derived from deterministic non-uniformities associated to vane-to-vane flow patterns, applicable in further modelling of deterministic stresses.

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.

Experimental and Numerical Investigation Into the Unsteady Interaction of Labyrinth Seal Leakage Flow and Main Flow in a 1.5-Stage Axial Turbine

2004 ◽  
Author(s):  
A. Giboni ◽  
K. Wolter ◽  
J. R. Menter ◽  
H. Pfost
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Main Flow ◽  
Navier Stokes ◽  
Experimental Program ◽  
Leakage Flow ◽  
Axial Turbine ◽  
Flow Phenomena ◽  
Grid Points

This paper presents the results of experimental and numerical investigations into the flow in a 1.5-stage low-speed axial turbine with a straight labyrinth seal on the rotor shroud. The paper focuses on the time dependent interaction between the leakage flow and the main flow. The experimental program consists of time accurate measurements of the three-dimensional properties of the main flow. The region of the entering leakage flow downstream of the rotor trailing edge was of special interest. The measurements were carried out using pneumatic five-hole probes and three dimensional hot-wire probes at the design operating point of the turbine. The measurement planes behind the three blade rows extend over one pitch from the shroud to the casing. The complex three-dimensional flow field is mapped in great detail by 1,008 points per measurement plane. The time-accurate experimental data of the three measurement planes was compared with the results of unsteady, numerical simulations of the turbine flow. The 3D-Navier-Stokes Solver CFX-TASCflow was used. The experimental and numerical results correspond well and allow detailed analysis of the mixing process. As demonstrated in this paper, the leakage flow causes strong fluctuations of the secondary flow behind the rotor and the second stator. Above all, the high number of numerical grid points reveals both the secondary flow phenomena and the vortex structures of the mixing zone. The time-dependence of both position and intensity of the vortices is shown. The development of the important leakage vortex is illustrated and explained. The paper shows that even at realistic clearance heights the leakage flow gives rise to negative incidence of considerable parts of the downstream stator which causes the flow to separate. Thus, labyrinth seal leakage flow should be taken properly into account in the design or optimization process of turbomachinery.

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