scholarly journals 3-D Loss Prediction Based on Secondary Flow and Blade Shear Layer Interaction

1991 ◽  
Author(s):  
D. T. Katramatos ◽  
J. K. Kaldellis
Keyword(s):  
Shear Layer ◽  
Secondary Flow ◽  
Axial Compressor ◽  
Prediction Method ◽  
Test Cases ◽  
Loss Distribution ◽  
Flow Angle ◽  
Flow Calculation ◽  
Loss Prediction ◽  
Profile Loss

The 3-D loss distribution along axial turbomachines has been investigated in the present work. For this purpose, our well documented secondary flow calculation method has been interactively coupled with our fast blade-to-blade shear layer calculation code, in order to predict the complete secondary flow and profile loss distribution. The presence of an even moderate secondary flow field modifies the flow angle distributions, thus making clear the need of a reliable profile loss prediction method for off-design cases, especially in the presence of separation. Accordingly, the blade-to-blade code predicts the profile loss distribution and subsequently provides the correct total pressure field for the secondary flow calculation. The combination of the above mentioned codes finally gives a realistic picture of the flow quantities at any S3 surface along a machine at a minimal computer cost. Several test cases, including axial compressor and turbine cascades as well as transonic axial compressor blade rows have been investigated. The results are in good agreement with the experimental data and are favourably compared with various recent correlations.

A Secondary Flow Calculation Method for Single-Stage Axial Transonic Flow Compressors, Including Shock-Secondary Flow Interaction

1990 ◽  
Vol 112 (4) ◽  
pp. 652-668 ◽  
Author(s):  
J. Kaldellis ◽  
D. Douvikas ◽  
F. Falchetti ◽  
K. D. Papailiou
Keyword(s):  
Shear Layer ◽  
Secondary Flow ◽  
Calculation Method ◽  
Transonic Flow ◽  
External Flow ◽  
Single Stage ◽  
Zone Model ◽  
Flow Calculation ◽  
Viscous Shear ◽  
Wall Shear

A secondary flow calculation method is presented, which makes use of the meridional vorticity transport equation. Circumferential mean flow quantities are calculated using an inverse procedure. The method makes use of the mean kinetic energy integral equation and calculates simultaneously hub and tip secondary flow development. Emphasis is placed upon the use of a coherent two-zone model and particular care is taken to describe adequately the flow inside an unbounded (external), semi-bounded (annulus), and fully bounded (bladed) space. Along with the velocity field, the losses, the defect forces, and the corresponding additional work realized inside the viscous wall shear layer are calculated for stationary and rotating flow. An approximate model for the interaction of the viscous shear layers and the external flow is used, which takes into account the meridional and peripheral blockage. When shock waves are present in the external flow, an approximate interaction model is used, additionally, which calculates the static pressure field resulting from the interaction of the shock wave and the corresponding wall shear layer. The method has been applied to two single-stage transonic flow compressors and the results of the comparison between theory and experiment are presented and discussed.

Profile Loss Prediction for High Pressure Steam Turbines

2016 ◽  
Author(s):  
J. H. Cheon ◽  
P. Milčák ◽  
A. Pacák ◽  
C. R. Kang ◽  
M. Šťastný
Keyword(s):  
Mach Number ◽  
Prediction Method ◽  
Steam Turbines ◽  
Loss Mechanism ◽  
Loss Model ◽  
Correction Curve ◽  
Loss Prediction ◽  
Mach Number Distribution ◽  
Exit Mach Number ◽  
Profile Loss

A method is presented for predicting the energy loss for a 2D turbine cascade blade operating in subsonic regions where the exit Mach number ≤ 0.8. A prediction method based on entropy creation was used to analyze the cascade profile loss mechanism. The basic profile loss model was introduced from the isentropic Mach number distribution along the blade surface and the trailing edge loss model was introduced from available test data, CFD results and available loss models. In addition, the Reynolds number correction curve was applied from previous research. Linear cascade test datasets which represent hub, mid-span and tip sections were used to validate this loss model.

A Secondary Flow Calculation Method for One Stage Axial Transonic Flow Compressors, Including Shock-Secondary Flow Interaction

1989 ◽  
Author(s):  
J. Kaldellis ◽  
D. Douvikas ◽  
F. Falchetti ◽  
K. D. Papailiou
Keyword(s):  
Shear Layer ◽  
Secondary Flow ◽  
Calculation Method ◽  
Transonic Flow ◽  
External Flow ◽  
Zone Model ◽  
Flow Calculation ◽  
One Stage ◽  
Viscous Shear ◽  
Wall Shear

A secondary flow calculation method is presented, which makes use of the meridional vorticity transport equation. Circumferentially mean flow quantities are calculated using an inverse procedure. The method makes use of the mean kinetic energy integral equation and calculates simultaneously hub and tip secondary flow development. Emphasis is placed upon the use of a coherent two-zone model and particular care is taken in order to describe adequately the flow inside an unbounded (external), semi-bounded (annulus) and fully-bounded (bladed) space. Along with the velocity field, the losses, the defect forces and the corresponding additional work realized inside the viscous wall shear layer are calculated for stationary and rotating flow. An approximate model for the interaction of the viscous shear layers and the external flow is used, which takes into account the meridional and the peripheral blockage. When shock waves are present in the external flow, an approximate interaction model is used, additionally, which calculates the static pressure field resulting from the interaction of the shock wave and the corresponding wall shear layer. The method has been applied to two one stage transonic flow compressors and the results of the comparison between theory and experiment are presented and discussed.

scholarly journals Effects of Periodic Wake Passing Upon Aerodynamic Loss of a Turbine Cascade: Part I — Measurements of Wake-Affected Cascade Loss by Use of a Pneumatic Probe

1999 ◽  
Author(s):  
Ken-ichi Funazaki ◽  
Nobuaki Tetsuka ◽  
Tadashi Tanuma
Keyword(s):  
Turbine Cascade ◽  
Flow Angle ◽  
Linear Cascade ◽  
Local Loss ◽  
Aerodynamic Loss ◽  
Free Stream Turbulence ◽  
Pressure Distributions ◽  
Wake Turbulence ◽  
Wake Passing ◽  
Profile Loss

This paper reports on an experimental investigation of aerodynamic loss of a low-speed linear turbine cascade which is subjected to periodic wakes shed from moving bars of the wake generator. In this case, parameters related to the wake, such as wake passing frequency (wake Strouhal number) or wake turbulence characteristics, are varied to see how these wake-related parameters affect the local loss distribution or mass-averaged loss coefficient of the turbine cascade. Free-stream turbulence intensity is changed by use of a turbulence grid. In Part I of this paper a focus is placed on the measurements by use of a pneumatic five-hole yawmeter, which provides time-averaged stagnation pressure distributions downstream of the moving bars as well as of the turbine cascade. Spanwise distributions of wake-affected exit flow angle are also measured. From this study it is found that the wake passing greatly affects not only the profile loss but secondary loss of the linear cascade. Noticeable change in exit flow angle is also identified.

Aerodynamic Characterization of Transonic Turbine Vanes Optimized to Attenuate Rotor Forcing

2011 ◽  
Author(s):  
R. Puente ◽  
G. Paniagua ◽  
T. Verstraete
Keyword(s):  
High Efficiency ◽  
Prediction Method ◽  
Optimization Procedure ◽  
3D Design ◽  
Turbine Vanes ◽  
Turbine Vane ◽  
Loss Prediction ◽  
Transonic Turbine ◽  
Characteristic Features

A multi-objective optimization procedure is applied to the 3D design of a transonic turbine vane row, considering efficiency and stator outlet pressure distortion, which is directly related to induced rotor forcing. The characteristic features that define different individuals along the Pareto Front are described, analyzing the differences between high efficiency airfoils and low interaction. Pressure distortion is assessed by means of a model that requires only of the computation the steady flow field in the domain of the stator. The reduction of aerodynamic rotor forcing is checked via unsteady multistage aerodynamic computations. A well known loss prediction method is used to drive the efficiency of one optimization run, while CFD analysis is used for another, in order to assess the reliability of both methods. In both cases, the decomposition of total losses is performed to quantify the influence on efficiency of reducing rotor forcing. Results show that when striving for efficiency, the rotor is affected by few, but intense shocks. On the other hand, when the objective is the minimization of distortion, multiple shocks will appear.

An Inverse Inviscid Method for the Design of Quasi-Three-Dimensional Turbomachinery Cascades

1993 ◽  
Vol 115 (1) ◽  
pp. 121-127 ◽  
Author(s):  
E. Bonataki ◽  
P. Chaviaropoulos ◽  
K. D. Papailiou
Keyword(s):  
Differential Equation ◽  
Three Dimensional ◽  
Test Cases ◽  
Elliptic Type ◽  
Flow Angle ◽  
Blade Shape ◽  
Closure Conditions ◽  
Type Boundary ◽  
Absolute Frame ◽  
The Given

The calculation of the blade shape, when the desired velocity distribution is imposed, has been the object of numerous investigations in the past. The object of this paper is to present a new method suitable for the design of turbomachinery stator and rotor blade sections, lying on an arbitrary axisymmetric stream-surface with varying streamtube width. The flow is considered irrotational in the absolute frame of reference and compressible. The given data are the streamtube geometry, the number of blades, the inlet flow conditions and the suction and pressure side velocity distributions as functions of the normalized arc-length. The output of the computation is the blade shape that satisfies the above data. The method solves an elliptic type partial differential equation for the velocity modulus with Dirichlet and periodic type boundary conditions on the (potential function, stream function)-plane (Φ, Ψ). The flow angle field is subsequently calculated solving an ordinary differential equation along the iso-Φ or iso-Ψ lines. The blade coordinates are, finally, computed by numerical integration. A set of closure conditions has been developed and discussed in the paper. The method is validated on several test cases and a discussion is held concerning its application and limitations.

Improving a one-dimensional centrifugal compressor performance prediction method

2005 ◽  
Vol 219 (8) ◽  
pp. 653-659 ◽  
Author(s):  
E Swain
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Prediction Method ◽  
Compressor Cascade ◽  
One Dimensional ◽  
Compressor Performance ◽  
Cfd Analyses

A one-dimensional centrifugal compressor performance prediction technique that has been available for some time is updated as a result of extracting the component performance from three-dimensional computational fluid dynamic (CFD) analyses. Confidence in the CFD results is provided by comparison of overall performance for one of the compressor examples. The extracted impeller characteristic is compared with the original impeller loss model, and this indicated that some improvement was desirable. The position of least impeller loss was determined using a traditional axial compressor cascade method, and suitable algebraic expressions were derived to match the CFD data. The merit of the approach lies with the relative ease that CFD component performance currently can be achieved and adjusting one-dimensional methods to agree with the CFD-derived models.

scholarly journals Numerical Investigation on the Influence of Hot Streak Temperature Ratio in a High-Pressure Stage of Vaneless Counter-Rotating Turbine

2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Zhao Qingjun ◽  
Wang Huishe ◽  
Zhao Xiaolu ◽  
Xu Jianzhong
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Heat Load ◽  
Rotor Blades ◽  
Inlet Temperature ◽  
Combined Effects ◽  
Temperature Ratio ◽  
Flow Angle ◽  
Hot Streak ◽  
Relative Flow

The results of recent studies have shown that combustor exit temperature distortion can cause excessive heat load of high-pressure turbine (HPT) rotor blades. The heating of HPT rotor blades can lead to thermal fatigue and degrade turbine performance. In order to explore the influence of hot streak temperature ratio on the temperature distributions of HPT airfoil surface, three-dimensional multiblade row unsteady Navier-Stokes simulations have been performed in a vaneless counter-rotating turbine (VCRT). The hot streak temperature ratios from 1.0 (without hot streak) to 2.4 were used in these numerical simulations, including 1.0, 1.2, 1.6, 2.0, and 2.4 temperature ratios. The hot streak is circular in shape with a diameter equal to 25%of the span. The center of the hot streak is located at 50%of span and 0%of pitch (the leading edge of the HPT stator vane). The predicted results show that the hot streak is relatively unaffected as it migrates through the HPT stator. The hot streak mixes with the vane wake and convects towards the pressure surface (PS) of the HPT rotor when it moves over the vane surface of the HPT stator. The heat load of the HPT rotor increases with the increase of the hot streak temperature ratio. The existence of the inlet temperature distortion induces a thin layer of cooler air in the HPT rotor, which separates the PS of the HPT rotor from the hotter fluid. The numerical results also indicating the migration characteristics of the hot streak in the HPT rotor are predominated by the combined effects of secondary flow and buoyancy. The combined effects that induce the high-temperature fluid migrate towards the hub on the HPT rotor. The effect of the secondary flow on the hotter fluid increases as the hot streak temperature ratio is increased. The influence of buoyancy is directly proportional to the hot streak temperature ratio. The predicted results show that the increase of the hot streak temperature ratio trends to increase the relative Mach number at the HPT rotor outlet, and decrease the relative flow angle from 25%to 75%span at the HPT rotor outlet. In the other region of the HPT outlet, the relative flow angle increases when the hot streak temperature ratio is increased. The predicted results also indicate that the isentropic efficiency of the VCRT decreases with the increase of the hot streak temperature ratio.

scholarly journals Measurement and Prediction of Short-Range Path Loss between 27 and 40 GHz in University Campus Scenarios

2020 ◽  
Author(s):  
Glaucio Ramos ◽  
Carlos Vargas ◽  
Luiz Mello ◽  
Paulo Pereira ◽  
Sandro Gonçalves ◽  
...  
Keyword(s):  
Short Range ◽  
Prediction Models ◽  
Path Loss ◽  
Prediction Method ◽  
University Campus ◽  
Millimetre Wave ◽  
Empirical Prediction ◽  
Loss Prediction ◽  
Path Loss Prediction ◽  
Path Loss Measurements

Abstract In this paper, we present the results of short-range path loss measurements in the microwave and millimetre wave bands, at frequencies between 27 and 40 GHz, obtained in a campaign inside a university campus in Rio de Janeiro, Brazil. Existing empirical path loss prediction models, including the alpha-beta-gamma (ABG) model and the close-in free space reference distance with frequency dependent path loss exponent (CIF) model are tested against the measured data, and an improved prediction method that includes the path loss dependence on the height di erence between transmitter and receiver is proposed. A fuzzy technique is also applied to predict the path loss and the results are compared with those obtained with the empirical prediction models.

Sign in / Sign up

Export Citation Format

Share Document