scholarly journals Numerical Investigation on Flow Characteristics and Aerodynamic Performance of a 1.5-Stage SCO2 Axial-Inflow Turbine with Labyrinth Seals

2020 ◽  
Vol 10 (1) ◽  
pp. 373 ◽  
Author(s):  
Qiuwan Du ◽  
Di Zhang
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Groove Depth ◽  
Aerodynamic Performance ◽  
Rotor Blades ◽  
Groove Width ◽  
Cavity Surface ◽  
Labyrinth Seals ◽  
Blade Tip ◽  
Peak Value

The leakage problem of supercritical carbon dioxide (SCO2) axial-inflow turbine brings great challenges to the efficiency and security of the power system. Labyrinth seals are usually utilized to improve the leakage characteristics of the blade tip. In this paper, a 1.5-stage SCO2 axial-inflow turbine is established and labyrinth seals are arranged on the top of the first stage stator and rotor blades. The effects of seal clearance, groove on seal cavity surface and circle groove shape on flow characteristics and aerodynamic performance under different pressure ratio are investigated. Increasing seal clearance can significantly weaken the turbine performance. Arranging rectangle, circle and V-shaped grooves on the seal cavity surface near the outlet of the seal gap can enhance the energy dissipation, reduce the relative leakage and improve the power and efficiency. Increasing the groove width can improve the aerodynamic performance while the effect of the groove depth is weak. The configuration where the circle groove width is 50% of the pitch of seal tooth achieves the best performance with the relative leakage of stator1 and rotor, power and efficiency of 6.04 × 10−3, 8.09 × 10−3, 3.467 MW and 86.86% respectively. With an increase in pressure ratio, the relative leakage increases firstly and then remains almost constant. The power increases while the efficiency increases firstly and then decreases, reaching the peak value under the design condition.

scholarly journals Numerical study of unsteady flow and exciting force for swept turbomachinery blades

2016 ◽  
Vol 20 (suppl. 3) ◽  
pp. 669-676
Author(s):  
Di Zhang ◽  
Ma Jiao-Bin ◽  
Qi Jing
Keyword(s):  
Boundary Layer ◽  
Unsteady Flow ◽  
Pressure Fluctuation ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Rotor Blades ◽  
Stable Operation ◽  
Straight Blade ◽  
Excitation Force

The aerodynamic performance of blade affects the vibration characteristics and stable operation of turbomachinery closely. The aerodynamic performance of turbine stage can be improved by using swept blade. In this paper, the RANS method and the RNG k-? turbulence mode were adopted to investigate the unsteady flow characteristics and excitation force of swept blade stage. According to the results, for the swept blade, the fluid of boundary layer shifts in radial direction due to the influence of geometric construction. It is observed that there is similar wake development for several kinds of stators, and the wake has a notable effect on the boundary layer of the rotor blades. When compared with straight blade, pressure fluctuation of forward-swept blade is decreased while the pressure fluctuation of backward-swept blade is increased. The axial and tangential fundamental frequency excitation force factors of 15?forward-swept blade are 0.139 and 0.052 respectively, which are the least, and all excitation force factors are in the normal range. The excitation factor of the forward-swept blade is decreased compared with straight blade, and the decreasing percentage is closely related to the swept angle. As for backward-swept blades, the situation is the other way around. Additionally, the change of axial excitation factor is more obvious. So the vibration reduction performance of forward-swept blade is better.

Numerical and Experimental Investigation on the Effect of Swirl Brakes on the Labyrinth Seals

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Dan Sun ◽  
Shuang Wang ◽  
Cheng-Wei Fei ◽  
Yan-Ting Ai ◽  
Ke-Ming Wang
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Impedance Method ◽  
Swirl Ratio ◽  
Labyrinth Seals ◽  
Rotating Speed ◽  
Simulation And Experiment ◽  
Computational Fluid Dynamics Cfd ◽  
Static Flow

Swirl brake influences the static and rotordynamic characteristics of labyrinth seal which are important in the prediction of turbomachine stability. To study the influence of the swirl brakes on improving seal stability, the effects of swirl brakes on the static and rotordynamic characteristics of labyrinth seals were investigated by the combination of numerical simulation and experiment. First, it was performed to the effects of swirl brake on the static flow characteristics of labyrinth seal with swirl ratio and pressure distribution based on computational fluid dynamics (CFD). And then a comparison between leakage predicted by the CFD model and measurement was presented to verify the accuracy of the simulation. Moreover, an experiment was implemented to analyze the rotordynamic characteristics of labyrinth seal using an improved impedance method based on an unbalanced synchronous excitation method on a rotor test rig. The influences of swirl brake density, length, inlet/outlet pressure ratio, and rotating speed were measured and discussed, respectively. The CFD numerical results show that the swirl brake effectively reduces the seal swirl ratio (∼60–75% less), circumferential pressure difference (∼25–85% less) so that the seal destabilizing forces decrease. With the increasing of the swirl vanes density and length, the seal leakage drops (∼8–20% less). The experimental rotordynamic characteristics results show that it is more obvious to reduce the cross-couple stiffness (∼50–300% less) and increase the direct damping (∼50–60% larger) with the increasing in the number and length of the swirl vanes, and thus the swirl brake improves the seal rotordynamic stability. The efforts of this paper provide a useful insight to clearly understand the effects of swirl brakes on the labyrinth seal static and rotordynamic characteristics, which is beneficial to improve the design of annular seals.

Rub-Groove Width and Depth Effects on Flow Predictions for Straight-Through Labyrinth Seals

2004 ◽  
Vol 126 (4) ◽  
pp. 781-787 ◽  
Author(s):  
David L. Rhode ◽  
Richard G. Adams
Keyword(s):  
Turbulence Model ◽  
Groove Depth ◽  
Groove Width ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Two Dimensional ◽  
Labyrinth Seals ◽  
Dramatic Effect ◽  
Finite Volume Discretization ◽  
Depth Effects

A fully compressible, two-dimensional axisymmetric, turbulent Navier-Stokes code using the finite-volume discretization approach was utilized to obtain an enhanced understanding of the effects of rub-grooves in straight-through, abradable labyrinth seals. The high-Re form of the k-ε turbulence model was used. The code was first validated against measurements of straight-through honeycomb labyrinths, and accurate results were obtained. It was found that in most of the cases considered (tooth tip outside of its rub groove), the presence of rub-grooves increases the leakage, except for the case of the large pre-rub clearance and narrow rub-groove width. The presence of the large- or the intermediate-width rub-grooves allows the rub-groove depth to exert a fairly large effect on the leakage, especially for the smallest pre-rub radial clearance. Further, the presence of a narrow rub-groove with the smallest pre-rub radial clearance gives a dramatic effect on the streamwise (i.e., cavity-to-cavity) variation in overall flow patten.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

scholarly journals The Aerodynamic Performance of an Over-the-Rotor Liner With Circumferential Grooves on a High Bypass Ratio Turbofan Rotor

2013 ◽  
Author(s):  
Rick Bozak ◽  
Christopher Hughes ◽  
James Buckley
Keyword(s):  
Pressure Ratio ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Oscillating Flow ◽  
Acoustic Liners ◽  
Performance Loss ◽  
Acoustic Liner ◽  
Blade Tip ◽  
Fan Blade ◽  
The Impact

While liners have been utilized throughout turbofan ducts to attenuate fan noise, additional attenuation is obtainable by placing an acoustic liner over-the-rotor. Previous experiments have shown significant fan performance losses when acoustic liners are installed over-the-rotor. The fan blades induce an oscillating flow in the acoustic liners which results in a performance loss near the blade tip. An over-the-rotor liner was designed with circumferential grooves between the fan blade tips and the acoustic liner to reduce the oscillating flow in the acoustic liner. An experiment was conducted in the W-8 Single-Stage Axial Compressor Facility at NASA Glenn Research Center on a 1.5 pressure ratio fan to evaluate the impact of this over-the-rotor treatment design on fan aerodynamic performance. The addition of a circumferentially grooved over-the-rotor design between the fan blades and the acoustic liner reduced the performance loss, in terms of fan adiabatic efficiency, to less than 1% which is within the repeatability of this experiment.

Effects of Pressure Ratio and Fin Pitch on Leakage Flow Characteristics in High Rotating Labyrinth Seals

2006 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Zhenping Feng
Keyword(s):  
Flow Rate ◽  
Geometrical Structure ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Rotational Axis ◽  
Labyrinth Seals ◽  
Sealing Performance ◽  
Leakage Flow Rate

Labyrinth seals represent an important flow element in the sealing equipment of modern turbomachinery industries. The straight-through and stepped labyrinth seal are widely used in modern steam turbine due to their comparable simple structure and low manufactured costs. The influence of pressure ratio and fin pitch on the leakage flow characteristics of the straight-through and stepped labyrinth seals is numerically determined. The pressure ratio is defined as the outlet static pressure divided by the inlet total pressure. The fin pitch varied in the fixed axial distance of the labyrinth seal. The geometries investigated represent designs of the straight-through and stepped labyrinth seal typical for modern steam turbines. The leakage flow fields in the high rotating straight-through and stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT with the fixed seal clearance and fins geometrical structure. The effect of the rotational axis is also taken into account in numerical computations. Numerical simulations covered a range of pressure ratio and fin pitch for the straight-through and stepped labyrinth seals. Dimensionless discharge coefficients, describing the sealing performance, are calculated from the simulation results. The numerical results show that pressure ratio and fin pitch both affects the sealing performance with the fixed seal clearance and fin geometrical structure. The leakage flow rate decreases with the decreasing fin pitch for both the straight-through and stepped labyrinth seal at the fixed pressure ratio. Furthermore, the leakage flow rate decreases with the increasing pressure ratio at the fixed fin pitch for two kinds of labyrinth seals in the present study. This research provides technical support for improved design of labyrinth seals in turbomachinery.

Experimental Investigations on the Thermal Load and Leakage Flow of a Turbine Blade Tip Section With Different Tip Section Geometries

2000 ◽  
Author(s):  
Martin F. Urban ◽  
Nicolas Vortmeyer
Keyword(s):  
Thermal Load ◽  
Flow Characteristics ◽  
Systematic Investigation ◽  
Rotor Blades ◽  
Experimental Program ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Leakage Flow ◽  
Gap Flow ◽  
Blade Tip

The gap flow across the tips of cooled rotor blades of combustion turbines is of crucial importance for the thermal load of the tip section and the stage efficiency. Various blade tip section designs with different cooling concepts were tested in a two dimensional steam cascade test rig with superheated steam as working fluid. The blade tip surface temperature distributions were measured with a thermography system and the gap flow was determined by 105 static wall pressure measurements at the opposite wall. The experimental program included systematic variations of decisive flow parameters like Mach and Reynolds numbers of the main and leakage flow as well as variations of the gap width in a range of 1.6% to 4.8% of the chord length. The performance of a simple flat blade tip served as a baseline for the comparison with advanced grooved tip designs developed in earlier studies. In addition attention was given to a systematic investigation of the influence of the coolant mass flow ejected out of the blade into the grooved tip section. The paper presents an overview of the experimental program and results as well as a discussion of the influence of the main flow and geometry parameters on the leakage flow characteristics and the accompanying thermal load of the tip section.

Acoustics and Performance of High-Speed, Unequally Spaced Fan Rotors

1980 ◽  
Vol 102 (1) ◽  
pp. 19-27 ◽  
Author(s):  
S. Fujii
Keyword(s):  
Sound Pressure Level ◽  
High Speed ◽  
Sound Pressure ◽  
Pressure Ratio ◽  
Thermodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Measured Data ◽  
Pressure Level ◽  
Rotor Blades ◽  
High Pressure Ratio

This paper describes an experimental measurement of the effects of uneven blade spacing on the acoustic and aero-thermodynamic characteristics of high-speed, high-pressure-ratio fan rotors at two selected spacing configurations. A test rig, consisting of inlet guide vanes and transonic rotor blades, was employed to explore the redistribution of harmonic sound energy into a series of multiple tones of lower sound pressure level. The measured data indicated that a ten percent modulated rotor exhibited a six to eight decibel decrease in the sound pressure level as compared with the original first blade passage frequency harmonic. Disadvantages in aerodynamic performance resulting from spacing modulation were not so unfavorable for the ten percent modulated blades. However, with five percent modulated blades, serious deterioration in aerodynamic performance was observed particularly near the blade tip section, which produced an unfavourable acoustic signature. A calculation method, assuming a pulse event for each blade sound pressure, provided agreeable results with the measured data.

Numerical investigation of strake profile and maximum thickness position in the ram-rotor

2019 ◽  
Vol 233 (15) ◽  
pp. 5773-5787
Author(s):  
Ji-ang Han ◽  
Jian Guan ◽  
Jingjun Zhong ◽  
Zi-an Zhao
Keyword(s):  
Numerical Investigation ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Aerodynamic Performance ◽  
Maximum Thickness ◽  
Combination Scheme ◽  
Starting Point ◽  
Comprehensive Performance ◽  
Total Pressure Ratio ◽  
Peak Value

Numerical investigation of ram-rotors with different strake profiles and maximum thickness positions has been performed. Four types of strake profiles are modeled firstly and the results show that total pressure ratio and adiabatic efficiency of the ss-sym, ss-ps, and ss-ss schemes are improved in different degrees compared with the sym-sym scheme, in which the comprehensive performance of the ss-ss scheme is relatively optimal, and its total pressure ratio and adiabatic efficiency are increased by 26.275% and 2.554%, respectively. The results of different strake maximum thickness positions indicate that the total pressure ratio and adiabatic efficiency are gradually increasing with the backward movement of starting point of maximum thickness, and the pressure rising capacity can come to a peak value. As the ending point of maximum thickness moves backward, there both exist peak values of the total pressure ratio and adiabatic efficiency. Compared with the ss-ss scheme, the scheme that combines optimal starting and ending point positions of maximum thickness takes advantage of these two schemes to achieve a higher aerodynamic performance, with total pressure ratio and adiabatic efficiency increasing 0.182% and 1.928%, respectively. Moreover, in comparison to the original sym-sym scheme, the total pressure ratio and the adiabatic efficiency of the combination scheme are improved much by 26.50% and 4.53%.

scholarly journals Artificial intelligence-based Monte-Carlo numerical simulation of aerodynamics of tire grooves using computational fluid dynamics

2019 ◽  
Vol 33 (03) ◽  
pp. 302-316 ◽  
Author(s):  
Ghulam Moeen Uddin ◽  
Syed Muhammad Arafat ◽  
Ali Hussain Kazim ◽  
Muhammad Farhan ◽  
Sajawal Gul Niazi ◽  
...  
Keyword(s):  
Neural Network ◽  
Fluid Dynamics ◽  
Monte Carlo ◽  
Lift Coefficient ◽  
Groove Depth ◽  
Aerodynamic Performance ◽  
Groove Width ◽  
Performance Parameters ◽  
Drag And Lift ◽  
Drag And Lift Coefficient

AbstractIn the current work, the effects of design (groove depth and groove width) and operational (temperature and velocity) parameters on aerodynamic performance parameters (coefficient of drag and coefficient of lift) of an isolated passenger car tire have been investigated. The study is conducted by using neural network-based Monte-Carlo analysis on computational fluid dynamics (CFD). The computer experiments are designed to obtain the causal relationship between tire design, operational, and aerodynamic performance parameters. The Reynolds-averaged Navier–Stokes equations-based RealizableK-εmodel has been employed to analyze the variations in flow patterns around an isolated tire. The design parameters are varied over wide range and full factorial design, while considering temperature and velocity is completely explored to draw conclusive results. The multi-layer perceptron type neural network with the back-propagation algorithm is trained to map any non-linearity in causal relationships. The sensitivity analysis is performed to find the relationship between control variables and performance indicators. The importance of control variable is determined by both sensitivity and significance analyses and the paired interaction analysis is performed between selected control variables to find the interactive behavior of corresponding variables. The design parameter of groove width with 6.8% and 41% reduction in drag and lift coefficient, respectively, and conventionally overlooked operational parameter of velocity with 4% and 35% impact on drag and lift coefficient, respectively, are found to be the most significant variables. The air trapped between the longitudinal grooves and the road is found to follow the beam theory. The interaction of the groove depth and width is found to be significant with respect to coefficient of lift based on the air beam concept. The interaction of groove width and velocity is found to be significant with respect to both coefficients of lifts and drag.

Sign in / Sign up

Export Citation Format

Share Document