Comparison between loss coefficients of smooth, smooth-thickened, and rough-thickened axial turbine blades

2007 ◽  
Vol 221 (4) ◽  
pp. 575-582
Author(s):  
Samsher
Keyword(s):  
Turbine Blades ◽  
Axial Turbine ◽  
Loss Coefficients

Optimization of Supersonic Axial Turbine Blades Based on Surrogate Models

2020 ◽  
Author(s):  
Markus Waesker ◽  
Bjoern Buelten ◽  
Norman Kienzle ◽  
Christian Doetsch
Keyword(s):  
Reynolds Number ◽  
Turbine Blade ◽  
Surrogate Model ◽  
Cfd Simulation ◽  
Turbine Blades ◽  
Energy System ◽  
Design Parameters ◽  
Blade Design ◽  
Axial Turbine ◽  
Velocity Coefficient

Abstract Due to the transition of the energy system to more decentralized sector-coupled technologies, the demand on small, highly efficient and compact turbines is steadily growing. Therefore, supersonic impulse turbines have been subject of academic research for many years because of their compact and low-cost conditions. However, specific loss models for this type of turbine are still missing. In this paper, a CFD-simulation-based surrogate model for the velocity coefficient, unique incidence as well as outflow deviation of the blade, is introduced. This surrogate model forms the basis for an exemplary efficiency optimization of the “Colclough cascade”. In a first step, an automatic and robust blade design methodology for constant-channel blades based on the supersonic turbine blade design of Stratford and Sansome is shown. The blade flow is fully described by seven geometrical and three aerodynamic design parameters. After that, an automated numerical flow simulation (CFD) workflow for supersonic turbine blades is developed. The validation of the CFD setup with a published supersonic axial turbine blade (Colclough design) shows a high consistency in the shock waves, separation zones and boundary layers as well as velocity coefficients. A design of experiments (DOE) with latin hypercube sampling and 1300 sample points is calculated. This CFD data forms the basis for a highly accurate surrogate model of supersonic turbine blade flow suitable for Mach numbers between 1.1 and 1.6. The throat-based Reynolds number is varied between 1*104 and 4*105. Additionally, an optimization is introduced, based on the surrogate model for the Reynolds number and Mach number of Colclough and no degree of reaction (equal inlet and outlet static pressure). The velocity coefficient is improved by up to 3 %.

Experimental Validation of Forced Response Methods in a Multi-Stage Axial Turbine

2018 ◽  
Author(s):  
Thomas Hauptmann ◽  
Christopher E. Meinzer ◽  
Joerg R. Seume
Keyword(s):  
Experimental Data ◽  
Vibration Amplitude ◽  
Turbine Blades ◽  
Service Condition ◽  
Sensitivity Study ◽  
Forced Response ◽  
Tip Clearance ◽  
Computational Time ◽  
Reference Case ◽  
Axial Turbine

Depending on the in service condition of jet engines, turbine blades may have to be replaced, refurbished, or repaired in the course of an engine overhaul. Thus, significant changes of the turbine blade geometry can be introduced due to regeneration and overhaul processes. Such geometric variances can affect the aerodynamic and aeroelastic behavior of turbine blades. One goal in the development of the regeneration process is to estimate the aerodynamic excitation of turbine blades depending on these geometric variances caused during the regeneration. Therefore, this study presents an experimentally validated comparison of two methods for the prediction of forced response in a multistage axial turbine. Two unidirectional fluid structure interaction (FSI) methods, a time-linearized and a time-accurate with a subsequent linear harmonic analysis, are employed and the results validated against experimental data. The results show that the vibration amplitude of the time-linearized method is in good agreement with the experimental data and, also requires lower computational time than the time-accurate FSI. Based on this result, the time-linearized method is used to perform a sensitivity study of the tip clearance size of the last rotor blade row of the five stage axial turbine. The results show that an increasing tip clearances size causes an up to 1.35 higher vibration amplitude compared to the reference case, due to increased forcing and decreased damping work.

A Theoretical Study of the Performance of an Axial Flow Turbine for a Microhydro Installation

1996 ◽  
Vol 210 (2) ◽  
pp. 121-129 ◽  
Author(s):  
G J Parker
Keyword(s):  
Theoretical Study ◽  
Draft Tube ◽  
Guide Vane ◽  
Turbine Blades ◽  
Axial Flow ◽  
Prototype System ◽  
Blade Angle ◽  
Flow Through ◽  
Loss Coefficients ◽  
Vane Angle

The Bernoulli-with-loss equation, with the losses represented by a constant times the velocity head, has been applied to each section of the flow through a small turbine system consisting of inlet guide vanes, axial flow turbine and draft tube. Using experimental data and the sets of equations, the flow angles around the turbine blades and the loss coefficients in the turbine and in the draft tube were determined. These were used to predict the effect of varying the guide vane angle and the turbine blade angle on performance. They were also used to predict the effects on the performance of a geometrically similar prototype system.

Influence of Geometric Effects on the Aspect Ratio Optimization of Axial Turbine Bladings

1978 ◽  
Author(s):  
D. Rist
Keyword(s):  
Aspect Ratio ◽  
Absolute Size ◽  
Axial Turbine ◽  
Flow Channels ◽  
Best Value ◽  
Loss Coefficients ◽  
Relationship Of ◽  
The Relationship ◽  
Ratio Optimization ◽  
Geometric Effects

In order to illustrate optimization possibilities, the cooled axial turbine stage has been investigated regarding aerothermodynamics. Aims of the study are: (a) to estimate the range of the aspect ratio in which the aerothermodynamic efficiency, under comparable conditions, is not less than 0.2 percent under the best value in order to acquire tolerances for the best possible blading design when considering other design and aspects; (b) to acquire the relationship of the turbine loss coefficients and efficiencies to the absolute size of the flow channels, i.e. (also) to the hot gas flowrate. This is important for fair comparison of smaller and larger machines as well as for realistic judgments and prognosis pertaining especially to small units.

Development of a Cost-Efficient Test Rig for Turbine Loss Education

2014 ◽  
Author(s):  
Stefan aus der Wiesche ◽  
Steffen Wulff ◽  
Felix Reinker ◽  
Karsten Hasselmann
Keyword(s):  
Turbine Blades ◽  
Test Rig ◽  
Flow Angle ◽  
Efficient Test ◽  
Academic Courses ◽  
Flow Deviation ◽  
Flow Through ◽  
Loss Coefficients ◽  
Turbine Cascades ◽  
Cost Efficient

A large number of approaches have been made to predict the total pressure loss coefficients and flow deviation angles to the geometry of turbine cascades and the incoming flow. Students feel typically uncomfortable when faced with turbine loss coefficients during their education, and it is challenging to fully understand turbine losses only by means of theory. The integration of a turbine cascade facility into academic courses might be useful but such test facilities are expensive or not available for a large number of engineering schools. To overcome this issue, a cost-efficient test rig for measurements of the flow through a two-dimensional cascade of turbine blades was designed. This test rig enabled the measurement of the flow through a blade cascade and the formation of wakes. The effect of the inlet flow angle on the cascade performance was investigated easily by students. Based on own measurements, the students were able to apply the most prominent approaches for determining loss coefficients. Furthermore, they compared their results with literature data and predictions of available correlations. By doing that, the importance of blade spacing and Reynolds number level on profile loss coefficients became more transparent and invited to further studies.

Numerical Investigation of Losses Due to Unsteady Effects in Axial Turbines

2003 ◽  
Author(s):  
Michael Moczala ◽  
Ernst von Lavante ◽  
Manuchehr Parvizinia
Keyword(s):  
High Pressure ◽  
Numerical Investigation ◽  
Research Work ◽  
Navier Stokes ◽  
Loss Assessment ◽  
Physical Explanation ◽  
Axial Turbine ◽  
Loss Coefficients ◽  
Axial Turbines ◽  
Unsteady Effects

Understanding of losses caused by unsteady effects is essential in efforts to improve the efficiency of modern turbomachines. In the present research work, the unsteady midspan flow in a typical high pressure axial turbine was investigated using a compressible Navier Stokes solver. The aim of this study was to take a closer look at trends in the loss behavior depending on several flow and geometry parameters as well as to give a physical explanation of these trends. Two different definitions of loss coefficients were also employed for the loss assessment and its suitability for evaluation of “unsteady losses” was discussed considering accuracy and physical aspects.

Investigation of Three-Dimensional Unsteady Flows in a Two-Stage Shrouded Axial Turbine Using Stereoscopic PIV—Kinematics of Shroud Cavity Flow

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Yong Il Yun ◽  
Luca Porreca ◽  
Anestis I. Kalfas ◽  
Seung Jin Song ◽  
Reza S. Abhari
Keyword(s):  
Turbine Blades ◽  
Cavity Flow ◽  
Main Flow ◽  
Stereoscopic Particle Image Velocimetry ◽  
Wake Flow ◽  
Leakage Flow ◽  
Two Stage ◽  
Trailing Edge ◽  
Axial Turbine ◽  
Outward Motion

This paper presents an experimental study of the behavior of leakage flow across shrouded turbine blades. Stereoscopic particle image velocimetry and fast response aerodynamic probe measurements have been conducted in a low-speed two-stage axial turbine with a partial shroud. The dominant flow feature within the exit cavity is the radially outward motion of the main flow into the shroud cavity. The radial migration of the main flow is induced by flow separation at the trailing edge of the shroud due to a sudden area expansion. The radially outward motion is the strongest at midpitch as a result of interactions between vortices formed within the cavity. The main flow entering the exit cavity divides into two streams. One stream moves upstream toward the adjacent seal knife and reenters the main flow stream. The other stream moves downstream due to the interaction with the thin seal leakage flow layer. Closer to the casing wall, the flow interacts with the underturned seal leakage flow and gains swirl. Eventually, axial vorticity is generated due to these complex flow interactions. This vorticity is generated by a vortex tilting mechanism and gives rise to additional secondary flow. Because of these fluid motions combined with a contoured casing wall, three layers (the seal leakage layer, cavity flow layer, and main flow) are formed downstream of the shroud cavity. This result is different from the two-layer structure, which is found downstream of conventional shroud cavities. The seal leakage jet formed through the seal clearance still exists at 25.6% axial chord downstream of the second rotor. This delay of complete dissipation of the seal leakage jet and its mixing with the cavity flow layer is due to the contoured casing wall. Time-averaged flow downstream of the shroud cavity shows the upstream stator’s influence on the cavity flow. The time-averaged main flow can be viewed as a wake flow induced by the upstream stator whose separation at the shroud trailing edge induces pitchwise non-uniformity of the cavity flow.

Methods and Tools for Multidisciplinary Optimization of Axial Turbine Stages With Relatively Long Blades

2004 ◽  
Author(s):  
Leonid Moroz ◽  
Yuri Govoruschenko ◽  
Leonid Romanenko ◽  
Petr Pagur
Keyword(s):  
Optimal Design ◽  
Turbine Blades ◽  
Multidisciplinary Optimization ◽  
Stress Strain ◽  
Axial Turbine ◽  
Maximal Efficiency ◽  
Vibration Reliability ◽  
Technological Limitations

An effective methodology for optimal design of axial turbine blades is presented. It has been used for achieving stage maximal efficiency meeting both stress-strain and vibration reliability requirements and taking into account technological limitations.

Aeromechanical Optimization of a Winglet-Squealer Tip for an Axial Turbine

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Zbigniew Schabowski ◽  
Howard Hodson ◽  
Davide Giacche ◽  
Bronwyn Power ◽  
Mark R. Stokes
Keyword(s):  
Mechanical Performance ◽  
Turbine Blades ◽  
Careful Consideration ◽  
Rate Of Change ◽  
Leakage Loss ◽  
Simple Method ◽  
Axial Turbine ◽  
Low Speed ◽  
Aerodynamic Loss ◽  
Tip Leakage

The possibility of reducing the over tip leakage loss of unshrouded axial turbine rotors has been investigated in an experiment using a linear cascade of turbine blades and by using CFD. A numerical optimization of a winglet-squealer geometry was performed. The optimization involved the structural analysis alongside the CFD. Significant effects of the tip design on the tip gap flow pattern, loss generation and mechanical deformation under centrifugal loads were found. The results of the optimization process were verified by low speed cascade testing. The measurements showed that the optimized winglet-squealer design had a lower loss than the flat tip at all of the tested tip gaps. At the same time, it offered a 37% reduction in the rate of change of the aerodynamic loss with the tip gap size. The optimized tip geometry was used to experimentally assess the effects of the opening of the tip cavity in the leading edge part of the blade and the inclination of the pressure side squealer from the radial direction. The opening of the cavity had a negligible effect on the aerodynamic performance of the cascade. The squealer lean resulted in a small reduction of the aerodynamic loss at all the tested tip gaps. It was shown that a careful consideration of the mechanical aspects of the winglet is required during the design process. Mechanically unconstrained designs could result in unacceptable deformation of the winglet due to centrifugal loads. An example winglet geometry is presented that produced a similar aerodynamic loss to that of the optimized tip but had a much worse mechanical performance. The mechanisms leading to the reduction of the tip leakage loss were identified. Using this knowledge, a simple method for designing the tip geometry of a shroudless turbine rotor is proposed. Numerical calculations indicated that the optimized low-speed winglet-squealer geometry maintained its aerodynamic superiority over the flat tip blade with the exit Mach number increased from 0.1 to 0.8.

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