scholarly journals Numerical Investigation of Different Tip Clearances Effect on the Hydrodynamic Performance of Pumpjet Propulsor

2018 ◽  
Vol 15 (05) ◽  
pp. 1850037 ◽  
Author(s):  
Denghui Qin ◽  
Guang Pan ◽  
Qiaogao Huang ◽  
Zhengdong Zhang ◽  
Jiujiu Ke
Keyword(s):  
Numerical Simulation ◽  
Rotor Blade ◽  
Fluid Dynamic ◽  
Open Water ◽  
Suction Side ◽  
Close Relation ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Hydrodynamic Performance ◽  
Cfd Method

Previous studies show that the tip clearance loss limits the improvement of turbomachinery performance, and it is roughly in close relation with the gap size. In this study, a pumpjet propulsor (PJP) with different sizes of tip clearances ([Formula: see text], 0.5, 1, 2, 3[Formula: see text]mm) has been presented to investigate the influence of tip clearances on PJP. This analysis is based on computational fluid dynamic (CFD) method, and the SST k-[Formula: see text] turbulence model is applied. Calculations are carried out with a worldwide employed ducted propeller (the Ka4-70 propeller in 19A duct) to verify the numerical simulation. And the grid independence validation is discussed. The numerical simulation of PJP flow with different tip clearances is carried out. Results show that the open water efficiency decreases gradually with the increase of tip clearance. The efficiency decreasing is caused by the tip flow loss. The shape of tip vortex of PJP which consisted of tip-separation vortex and tip-leakage vortex is presented. Furthermore, the formation and spread process of tip vortex at different tip clearances are discussed. Then, the effect of different tip clearances on the pressure field of rotor blade is investigated. The main pressure area affected by different tip clearances is mainly concentrated in the area above 0.9 spanwise of the suction side of rotor blade. Beyond that, the effects of different tip clearances on the velocity field of PJP has been studied.

Numerical Analysis of Hydrodynamic Performance of FX-83-W Hydrofoil Current Turbine

2017 ◽  
Author(s):  
Yuchen Shang ◽  
Nikolaos I. Xiros
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Open Water ◽  
Hydrodynamic Performance ◽  
Ocean Current ◽  
Thrust Coefficient ◽  
Cfd Method ◽  
Three Dimensional Coordinate ◽  
Current Turbine

Ocean current flow characteristics are relatively stable and predictable, current turbine absorbs the energy of the ocean currents by the blades with a relative stable and lower angular velocity which indicates the capacity of current turbine greater than the onshore wind turbine. In this paper, the CFD method is utilized to calculate and analyze the working principle of FX-83-W current turbine. The three-dimensional coordinate of FX-83-W Hydrofoil blade surface have been calculated by MATLAB code, and 3D model has been established in Gambit. The basic control equations of CFD and its numerical solution are described, Reynolds Averaged N-S equations is used, and the realizable k-e turbulence model is introduced to solve the Reynolds stress in the RANS equation. The numerical algorithm is the finite volume method (FVM), and the numerical simulation of CFD is used to study the open water performance, leading to thrust coefficient KT and torque coefficient KQ of FX-83-W Hydrofoil. The hydrodynamic thrust and hydrodynamic power of the ocean current turbine under different sea conditions have been obtained by numerical simulation.

A Physical Model for the Tip Vortex Loss: Experimental Validation and Scaling Method

2012 ◽  
Author(s):  
Sascha Karstadt ◽  
Peter F. Pelz
Keyword(s):  
Measurement Data ◽  
Suction Side ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Tip Leakage Flow ◽  
Rotating Blades ◽  
Fluid Systems ◽  
Spiral Vortex ◽  
Flow Through

Losses through secondary flows occur in every turbomachine. Between the rotating blades and the casing of a turbomachine there is a secondary flow through the tip clearance caused by the pressure difference between the pressure and the suction side of the blade. This tip leakage flow is not involved in the work done by the rotating blades hence it reduces the aerodynamic efficiency. The flow through the tip clearance rolls up to a spiral vortex on the suction side of the blade and induces drag. Size and circulation of this vortex, according to the Helmholtz vortex theorem, depend on the bound vortex and the width of the tip clearance. Examinations of this structure lead to an idea of describing the tip vortex loss with analytical methods. Therefore an analytical approach is made regarding mainly the circulation at the blade tips. The method is discussed critically in the context of known loss models. It is shown to be a good summary of earlier methods. Since no explicit geometry data of the turbomachine is needed, it is much easier to use. The most important aspect is the excellent agreement with measurements performed at the Chair of Fluid Systems Technology. In total eleven different fan configurations are measured and analyzed in regard to their tip clearance losses. The measurements are performed at a test rig located at the laboratory of the Chair of Fluid Systems Technology at Technische Universität Darmstadt. Additionally further published measurement data is used to validate the method.

Effects of Tip Clearance on Unsteady Flow Characteristics in an Axial Turbine Stage

2009 ◽  
Author(s):  
Hao Sun ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Rotor Blade ◽  
Suction Side ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Blade Tip

The clearance between the rotor blade tip and casing wall in turbomachinery passages induces leakage flow loss and thus degrades aerodynamic performance of the machine. The flow field in turbomachinery is significantly influenced by the rotor blade tip clearance size. To investigate the effects of tip clearance size on the rotor-stator interaction, the turbine stage profile from Matsunuma’s experimental tests was adopted, and the unsteady flow fields with two tip clearance sizes of 0.67% and 2.00% of blade span was numerical simulated based on Harmonic method using NUMECA software. By comparing with the domain scaling method, the accuracy of the harmonic method was verified. The interaction mechanism between the stator wake and the leakage flow was investigated. It is found that the recirculation induced by the stator wake is separated by a significant “interaction line” from the flow field close to the suction side in the clearance region. The trend of the pressure fluctuation is contrary on both sides of the line. When the stator wakes pass by the suction side, the pressure field fluctuates and the intensity of the tip leakage flow varies. With the clearance size increasing, the “interaction line” is more far away from the suction side and the intensity of tip leakage flow also fluctuates more strongly.

Study of Three-Dimensional Viscous Flows in an Axial Compressor Cascade Including Tip Leakage Effects Using a SIMPLE-Based Algorithm

1986 ◽  
Vol 108 (1) ◽  
pp. 51-58 ◽  
Author(s):  
M. Pouagare ◽  
R. A. Delaney
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Simple Algorithm ◽  
Suction Side ◽  
Tip Clearance ◽  
High Loading ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Flow Phenomena

A multisweep space-marching solver based on a modified version of the SIMPLE algorithm was employed to study the three-dimensional flow field through a linear cascade. Three cases were tested: one with moderate loading, one with high loading, and one with high loading and tip clearance. The results of the numerical simulation were compared with available experimental measurements, and the agreement between the two was found satisfactory. The numerical simulation provided insight into several important endwall flow phenomena such as the interaction between the leakage and passage vortices, the interaction between the leakage vortex and the wake, the effect of leakage flow and loading on losses and secondary kinetic energy, the suction side corner separation, and the blowing of this separation by the leakage flow.

Improved Delayed Detached Eddy Simulation (IDDES) of a 1.5 Stage Axial Compressor Non-Synchronous Vibration

2020 ◽  
Author(s):  
Purvic Patel ◽  
Yunchao Yang ◽  
Gecheng Zha
Keyword(s):  
Rotor Blade ◽  
High Speed ◽  
Stokes Equations ◽  
Axial Compressor ◽  
Suction Side ◽  
Tip Vortex ◽  
Weno Scheme ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

Abstract This paper utilizes the Improved Delayed Detached Eddy Simulation (IDDES) to investigate the non-synchronous vibration (NSV) mechanism of a 1.5 stage high-speed axial compressor. The NSV occurs at a part speed in the rig test. A low diffusion E-CUSP approximate Riemann solver with a third order Weighted Essentially Non-Oscillating (WENO) scheme for the inviscid flux and a second order central differencing scheme for the viscous flux are employed to solve the 3D time accurate Navier-Stokes equations. The fully conservative sliding boundary condition is used to preserve the wake-propagation. The aerodynamic instability in the tip region induces two alternating low pressure regions near the leading and the trailing edge on the suction side of the rotor blade. It is observed that the circumferential tip vortex motion in the rotor passage above 75 % span and its coupling forces cause NSV at the operating speed. This instability moves in the counter-rotating direction in the rotational frame. The NSV results using URANS simulation is also presented for comparison. The predicted frequency with the IDDES and URANS using rigid blades agrees well with the measured frequency in the rig test. In addition to the NSV, the IDDES solver also captures the dominant engine order frequencies. The tip flow structures show the vortex filament with one end on the suction side of the rotor blade and other side terminating on the casing or the pressure side of the rotor blade.

Experimental Study of Tip Clearance Effects Under Transonic Flow Conditions

1996 ◽  
Author(s):  
M. Wehner ◽  
A. Bölcs ◽  
J. Bütikofer
Keyword(s):  
Test Section ◽  
Static Pressure ◽  
Suction Side ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Blade Loading ◽  
Gap Flow ◽  
Inlet Conditions ◽  
Axial Turbines ◽  
Tip Gap Flow

An idealized 3 blade test section has been used to study tip clearance effects which occur in transonic axial turbines. At subsonic inlet conditions (Mis1 = 0.56) the flow leaves the test section supersonic (Mis2 = 1.26). The tip clearance was varied from 0 to 15% of the chord length. Extensive laser-2-focus anemometry was used to determine the tip gap mass flow based on the velocity vectors for gaps with 6, 10 and 15% chord. At small clearances the tip gap flow is mainly influenced by the pressure drop between pressure and suction side, while for larger gaps the main flow field dominates the tip gap flow. The variation of the blade loading with the tip clearance was measured by static pressure tappings at 50% and 90% Span. Furthermore the static pressure along the tip surface was measured for varying tip clearances. Pitot probe traverses in the tip vortex region at different downstream positions revealed the vortex structures and vortex core evolution. For tip gaps of 3 and 6%, multiple vortices were detected which were not fully mixed downstream. The origin of these vortices moves towards the trailing edge for larger gaps.

Flow Physics and Profiling of Recessed Blade Tips: Impact on Performance and Heat Load

2006 ◽  
Author(s):  
Bob Mischo ◽  
Thomas Behr ◽  
Reza S. Abhari
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Suction Side ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Limiting Factor ◽  
Total Efficiency ◽  
Axial Turbine ◽  
Blade Tip ◽  
Improved Design

In axial turbine the tip clearance flow occurring in rotor blade rows is responsible for about one third of the aerodynamic losses in the blade row and in many cases is the limiting factor for the blade lifetime. The tip leakage vortex forms when the leaking fluid crosses the gap between the rotor blade tip and the casing from pressure to suction side and rolls up into a vortex on the blade suction side. The flow through the tip gap is both of high velocity and high temperature, with the heat transfer to the blade from the hot fluid being very high in the blade tip area. In order to avoid blade tip burnout and a failure of the machine, blade tip cooling is commonly used. This paper presents the physical study and an improved design of a recessed blade tip for a highly loaded axial turbine rotor blade with application in high pressure axial turbines in aero engine or power generation. With use of three-dimensional Computational Fluid Dynamics (CFD), the flow field near the tip of the blade for different shapes of the recess cavities is investigated. Through better understanding and control of cavity vortical structures, an improved design is presented and the differences to the generic flat tip blade are highlighted. It is observed that by an appropriate profiling of the recess shape, the total tip heat transfer Nusselt Number was significantly reduced, being 15% lower than the flat tip and 7% lower than the baseline recess shape. Experimental results also showed an overall improvement of 0.2% in the one-and-1/2-stage turbine total efficiency with the improved recess design compared to the flat tip case. The CFD analysis conducted on single rotor row configurations predicted a 0.38% total efficiency increase for the rotor equipped with the new recess design compared to the flat tip rotor.

Numerical Simulated Method on Wind Environmental of Outdoor

2011 ◽  
Vol 250-253 ◽  
pp. 3815-3821
Author(s):  
Can Li ◽  
Tian Fu Deng
Keyword(s):  
Numerical Simulation ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Outdoor Air ◽  
Wind Environment ◽  
Outdoor Air Quality ◽  
Turbulent Airflow ◽  
Cfd Method ◽  
Velocity Pressure ◽  
Improve Planning

Outdoor wind environment play an important role at planning an estate. The method of simulating the wind environment of the district was conducted by two cases that had been tested and verified. The steady-state three-dimensional turbulent airflow fields were analyzed by computational fluid dynamic (CFD) method for the two cases. The distribution of velocity, pressure and turbulivity were presented. The detailed schemes on simplified physical model, mesh division, solving and boundary conditions defining were presented. Results shows that numerical simulation helps predict the details of the outdoor wind environment of estate, and it helps evaluate outdoor air quality in all its aspects or improve planning.

scholarly journals Numerical Simulation of the Ducted Propeller and Application to a Semi-Submerged Vehicle

2020 ◽  
Vol 27 (2) ◽  
pp. 19-29
Author(s):  
Jin Zou ◽  
Guoge Tan ◽  
Hanbing Sun ◽  
Jie Xu ◽  
Yongkang Hou
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Open Water ◽  
The Self ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Cfd Simulations ◽  
Ducted Propeller ◽  
Numerical Software ◽  
Numerical Approaches

AbstractThe self-propulsion test of underwater vehicles is the key technique for predicting and evaluating the navigation performance of these submersibles. In this study, the numerical simulation of a standard propeller JD7704+Ka4-70 is first presented and the results are compared with experiments to validate the numerical approaches. The reason why the propulsion efficiency of the ducted propeller is higher than that of the conventional propeller is explored. Then, the paper proposes a series of numerical simulations conducted to test the performance of the ducted propeller designed according to the JD7704+Ka4-70 in order to match with the unmanned semi-submerged vehicle (USSV), and the propeller’s open water characteristic curves are obtained. The results show a reasonable agreement with the regression analysis. Afterwards, the numerical simulations focus on a self-propulsion test of the USSV with the designed ducted propeller and the self-propulsion point is obtained. The streamlines through the hull as well as the ducted propellers are clearly obtained, together with the velocity distributions of the propeller plane. The results vividly demonstrate the hydrodynamic performance of the USSV with the designed propellers. In this paper, all the CFD simulations are based on the numerical software, Star-CCM+, and use the Reynolds-averaged Navier‒Stokes (RANS) equations with the shear stress transport (SST) k-omega turbulence model.

Flow Physics and Profiling of Recessed Blade Tips: Impact on Performance and Heat Load

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Bob Mischo ◽  
Thomas Behr ◽  
Reza S. Abhari
Keyword(s):  
Heat Transfer ◽  
Rotor Blade ◽  
Suction Side ◽  
Tip Clearance ◽  
Limiting Factor ◽  
Total Efficiency ◽  
Base Line ◽  
Axial Turbine ◽  
Blade Tip ◽  
Improved Design

In axial turbine, the tip clearance flow occurring in rotor blade rows is responsible for about one-third of the aerodynamic losses in the blade row and in many cases is the limiting factor for the blade lifetime. The tip leakage vortex forms when the leaking fluid crosses the gap between the rotor blade tip and the casing from pressure to suction side and rolls up into a vortex on the blade suction side. The flow through the tip gap is both of high velocity and of high temperature, with the heat transfer to the blade from the hot fluid being very high in the blade tip area. In order to avoid blade tip burnout and a failure of the machine, blade tip cooling is commonly used. This paper presents the physical study and an improved design of a recessed blade tip for a highly loaded axial turbine rotor blade with application in high pressure axial turbines in aero engine or power generation. With use of three-dimensional computational fluid dynamics (CFD), the flow field near the tip of the blade for different shapes of the recess cavities is investigated. Through better understanding and control of cavity vortical structures, an improved design is presented and its differences from the generic flat tip blade are highlighted. It is observed that by an appropriate profiling of the recess shape, the total tip heat transfer Nusselt number was significantly reduced, being 15% lower than the flat tip and 7% lower than the base line recess shape. Experimental results also showed an overall improvement of 0.2% in the one-and-a-half-stage turbine total efficiency with the improved recess design compared to the flat tip case. The CFD analysis conducted on single rotor row configurations predicted a 0.38% total efficiency increase for the rotor equipped with the new recess design compared to the flat tip rotor.

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