Modification and optimization strategies for turbine arbitrary blade tips

2019 ◽  
Vol 233 (6) ◽  
pp. 675-688 ◽  
Author(s):  
Jiahui Jin ◽  
Yanping Song ◽  
Jianyang Yu ◽  
Fu Chen
Keyword(s):  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Kriging Model ◽  
Total Pressure Loss ◽  
Tip Leakage Flow ◽  
B Spline ◽  
Tip Leakage ◽  
Spline Surface ◽  
Blade Tip

The influence of different arbitrary blade tip shapes on restraining the tip leakage flow in a highly loaded turbine cascade has been numerically studied. A combined method of establishing and optimizing the arbitrary blade tip shape is proposed by using B-spline surface modeling, Kriging model and genetic optimization algorithm. The results show that the Kriging model established by the B-spline surface modeling method can accurately fit the relationship between the arbitrary blade tip shape and the relevant aerodynamic parameters. The optimal leakage mass flow tip and the optimal total pressure loss tip obtained by genetic algorithm both have strong inhibitory effects on tip leakage flow. Compare to the flat tip at 1%H gap height, the tip leakage mass flow of the optimal leakage mass flow case and the optimal total pressure loss case decrease by 11.14% and 10.23%, respectively, the area-average total pressure loss at exit section is reduced by 8.08% and 7.41%, respectively.

Effect of Winglet-Shroud Tip With Labyrinth Seals on Aerodynamic Performance of a Linear Turbine Cascade

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Yan Liu ◽  
Min Zhang ◽  
Tianlong Zhang ◽  
Mengchao Zhang ◽  
Ying He
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Flow Fields ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Tip Leakage Flow ◽  
Labyrinth Seals ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Measured Flow

This paper is a continuous study of a previously investigated novel winglet-shroud (WS) tip configuration. Two additional sealing fins are fixed on the WS tip to further reduce tip leakage. This configuration is referred to WS with seals (WSS) tip. Secondary flow structures and total pressure loss coefficients on a transverse plane downstream of the blade trailing edge are measured. Flow in a blade cascade is also numerically simulated to obtain more information of flow fields. Compared with the WS tip, both experimental and numerical results show that the WSS tip can further improve the aerodynamic performance as expected. Relative to the plain tip, the WSS and WS tips can reduce total pressure loss on one plane downstream of the blade trailing edge by 50% and 28%, respectively. This is mainly due to reduced intensity of tip leakage vortex (TLV). For the tip leakage mass flow rate, the WS tip decreases it by 33.6%, while the implement of two additional sealing fins contributes to an extremely high reduction of 88.7%. This demonstrates that the use of sealing fins is effective to control the tip leakage flow and improve flow fields. In addition, a deeper analysis by applying a normalized helicity scheme to identify the evolution of different vortices and by tracing trajectories of the fluid near the tip offers credible supports for results.

Characteristics of Tip-Leakage Flow at High Stagger-Angle Setting for Rotor Blade in an Axial Flow Fan

2012 ◽  
Author(s):  
Takahiro Nishioka ◽  
Masayoshi Joko
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Maximum Efficiency ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Stagger Angle

Rotor-tip flow fields at high stagger-angle setting were investigated to clarify the loss generation mechanism in a high specific-speed axial-flow fan. The tip clearance flow in the cases of large and small clearances, which are 2.0% and 1.0% of the rotor tip chord length respectively, are experimentally and numerically evaluated at the maximum efficiency point and the operating limit. At the maximum efficiency point, the tip leakage vortex reached to the rotor exit in both cases of large and small tip clearances. However, the leakage vortex in the case of large tip-clearance passed closer to the pressure side of the adjacent blade than that in the case of small one. Moreover, in the case of large tip clearance, the tip leakage vortex generated the large total pressure loss in the blade passage, and the interaction between the tip leakage vortex and the wake also generated the large total pressure loss at the rotor exit. Therefore, the maximum efficiency of the rotor and the fan was lower than that in the case of small tip clearance. At the operating limit, the tip-leakage vortex extended inside the blade passage and reached to the front part of the pressure side of the next blade in the case of small tip-clearance. Moreover, the double leakage flow occurred in the case of small tip clearance. In contrast, the leakage vortex reached to the leading edge of the next blade, and the spillage of the tip leakage flow from the leading edge occurred in the case of large tip clearance. The spillage of the tip leakage flow induced the larger total pressure loss than that induced by the double leakage flow. Therefore, the pressure rise in the case of large tip clearance is lower than that in the case of small tip clearance at the operating limit. It was concluded from the experimental and numerical results at the high stagger-angle setting for rotor blade that the loss generation mechanism depended on the behavior of tip-leakage vortex and that this behavior also depended on the tip-clearance.

Effect of the honeycomb tip with injection on the aerodynamic performance in a 1.5-stage turbine

2020 ◽  
pp. 1-25
Author(s):  
Jianyang Yu ◽  
Yabo Wang ◽  
YanPing Song ◽  
Fu Chen
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Navier Stokes ◽  
Total Efficiency ◽  
Cavity Depth ◽  
Tip Leakage

Abstract Three kinds of rotor tip configurations have been investigated numerically in the LISA 1.5-stage turbine, including the flat tip, the honeycomb tip and the honeycomb tip with injection. The effect of the cavity depth and the injection mass flow rate on the turbine performance is studied in detail, evaluated by the isentropic total-to-total efficiency and the tip leakage mass flow rate. The Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model are adopted in all the present computations. The numerical results show that the first stage efficiency is increased by up to 0.66% and the tip leakage mass flow rate is reduced by about 1.87% of the main flow. The pressure field and the flow feature inside the gap are explored. The flow structures and the total pressure loss contours in the rotor passage are presented. Finally, the total pressure loss is newly defined by considering the injection effect. It is indicated that the injection mass flow rate should be carefully determined for excellent overall performance.

Effect of the Double-Slot Injection on the Leakage Flow Control in a Honeycomb-Tip Turbine Cascade

2019 ◽  
Author(s):  
Yabo Wang ◽  
Yanping Song ◽  
Jianyang Yu ◽  
Fu Chen
Keyword(s):  
Flow Control ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Leakage Flow ◽  
Turbine Cascade ◽  
Tip Leakage

Abstract The effect of five arrangements of the double-slot injections on the leakage flow control is studied in a honeycomb-tip turbine cascade numerically. The honeycomb tip is covered with 67 intact honeycomb cavities, since the uneven tip is wearable and the cavity vortex could realize the aerodynamic sealing for the leakage flow. Then in the present study, a pair of injection slots is arranged blow each cavity, aiming to enhance the leakage flow suppression by modifying the cavity vortex. According to the orientation of the two slots, five designs of the double-slot injections are proposed. In detail, the two slots are opposite to each other or keep tangential to the original cavity vortex roughly. The three dimensional calculations were completed by using Reynolds-averaged Navier-Stokes (RANS) method and the k-ω turbulence model in the commercial software ANSYS CFX. The estimation of these tip designs is mainly according to the tip leakage mass flow rate and the total pressure loss. Firstly, the injection structures induced by the slots can be divided into X- and T-types inside the cavity. The results show that the T-type structure is more effective in reducing the tip leakage mass flow rate, with the maximum reduction up to 48.2%. Then the effect on the flow field inside the gap and the secondary flow in the upper passage is analyzed. Compared with the flat tip, the span-wise position of the tip leakage vortex core drops within the cascade and the range of the affected loss region expands. At the cascade exit, the tip leakage vortex moves toward the passage vortex near the casing, while the latter’s core rises. The position changes of the secondary vortices eventually determine the total pressure loss contour downstream the cascade. Finally, the injection total pressure and the upper casing motion are investigated. Interestingly, the injection intensity (mass flow rate) increases with the injection total pressure but this value decreases as the casing speed increases. The tip leakage mass flow rate decreases linearly as increasing the injection total pressure or the casing speed. Yet the averaged total pressure loss downstream the cascade increases with the injection total pressure but appears a nonlinear distribution against the casing speed.

Measurement of Blade Tip Heat Transfer and Leakage Flow in a Turbine Cascade With a Multi-Cavity Squealer Tip

2013 ◽  
Author(s):  
Jung Shin Park ◽  
Sang Hoon Lee ◽  
Jae Su Kwak ◽  
Won Suk Lee ◽  
Jin Taek Chung
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Leading Edge ◽  
Total Pressure Loss ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Measurement Results ◽  
Blade Tip ◽  
Cavity Floor

Tip leakage flow induces high heat transfer to the blade tip and causes significant aerodynamic losses. In this paper, we propose a multi-cavity squealer tip with an additional rib in the squealer cavity. Our study investigated the effects of the rib location and shape on the blade tip heat transfer and the total pressure loss. Experiments were performed in a five-bladed linear cascade using a low speed wind tunnel. The blade chord, pitch, and span length were 126mm, 102.7mm, and 160mm, respectively. The Reynolds number, based on the blade chord and cascade exit velocity, was 2.44×105, and a tip clearance of 1.25% of the blade span was considered. The additional rib was installed in the squealer tip cavity near the leading edge, the mid-chord, and the training edge, respectively. The shape of the rib was also varied from rectangular to triangular in order to minimize the rib surface area exposed to the hot gas. The secondary flow and total pressure loss were measured using a seven-hole probe at one-chord downstream of the blade trailing edge, and the heat transfer coefficient distributions were measured by utilizing the hue-detection based transient liquid crystal technique. Flow measurement results indicated that the proposed multi-cavity tip reduced the total pressure loss. The blade tip heat transfer measurement results showed that the proposed multi-cavity tip was able to reduce the maximum heat transfer region near the cavity floor near the leading edge, but the heat transfer on the second cavity floor increased due to the leakage flow reattachment.

Film Cooling and Aerodynamic Performance on Multi-Cavity Squealer Tip of a Turbine Blade

2021 ◽  
Author(s):  
Feng Li ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Cooling Performance ◽  
Pressure Loss Coefficient ◽  
Blade Tip ◽  
Total Pressure Loss Coefficient

Abstract The blade tip region of the shroud-less high-pressure gas turbine is exposed to an extremely operating condition with combined high temperature and high heat transfer coefficient. It is critical to design new tip structures and apply effective cooling method to protect the blade tip. Multi-cavity squealer tip has the potential to reduce the huge thermal loads and improve the aerodynamic performance of the blade tip region. In this paper, numerical simulations were performed to predict the aerothermal performance of the multi-cavity squealer tip in a heavy-duty gas turbine cascade. Different turbulence models were validated by comparing to the experimental data. It was found that results predicted by the shear-stress transport with the γ-Reθ transition model have the best precision. Then, the film cooling performance, the flow field in the tip gap and the leakage losses were presented with several different multi-cavity squealer tip structures, under various coolant to mainstream mass flow ratios (MFR) from 0.05% to 0.15%. The results show that the ribs in the multi-cavity squealer tip could change the flow structure in the tip gap for that they would block the coolant and the leakage flow. In this study, the case with one-cavity (1C) achieves the best film cooling performance under a lower MFR. However, the cases with multi-cavity (2C, 3C, 4C) show higher film cooling effectiveness under a higher MFR of 0.15%, which are 32.6%%, 34.2%% and 41.0% higher than that of the 1C case. For the aerodynamic performance, the case with single-cavity has the largest total pressure loss coefficient in all MFR studied, whereas the case with two-cavity obtains the smallest total pressure loss coefficient, which is 7.6% lower than that of the 1C case.

Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

2017 ◽  
Author(s):  
Brian M. T. Tang ◽  
Marko Bacic ◽  
Peter T. Ireland
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Total Pressure ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Turbine Efficiency ◽  
Coolant Injection ◽  
Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

scholarly journals Preliminary Experimental Study on Pressure Loss Coefficients of Exhaust Manifold Junction

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Xiao-lu Lu ◽  
Kun Zhang ◽  
Wen-hui Wang ◽  
Shao-ming Wang ◽  
Kang-yao Deng
Keyword(s):  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Ratio ◽  
Pressure Loss Coefficient ◽  
Loss Coefficients ◽  
Total Pressure Loss Coefficient ◽  
Mass Flow Ratio

The flow characteristic of exhaust system has an important impact on inlet boundary of the turbine. In this paper, high speed flow in a diesel exhaust manifold junction was tested and simulated. The pressure loss coefficient of the junction flow was analyzed. The steady experimental results indicated that both of static pressure loss coefficientsL13andL23first increased and then decreased with the increase of mass flow ratio of lateral branch and public manifold. The total pressure loss coefficientK13always increased with the increase of mass flow ratio of junctions 1 and 3. The total pressure loss coefficientK23first increased and then decreased with the increase of mass flow ratio of junctions 2 and 3. These pressure loss coefficients of the exhaust pipe junctions can be used in exhaust flow and turbine inlet boundary conditions analysis. In addition, simulating calculation was conducted to analyze the effect of branch angle on total pressure loss coefficient. According to the calculation results, total pressure loss coefficient was almost the same at low mass flow rate of branch manifold 1 but increased with lateral branch angle at high mass flow rate of branch manifold 1.

Aerodynamic optimisation of a winglet-cavity tip in a high-pressure axial turbine cascade

2016 ◽  
Vol 232 (4) ◽  
pp. 649-663 ◽  
Author(s):  
Zhihua Zhou ◽  
Shaowen Chen ◽  
Songtao Wang
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Suction Side ◽  
Tip Clearance ◽  
Total Pressure Loss ◽  
Pressure Side ◽  
Tip Clearance Flow ◽  
Clearance Flow

Tip clearance flow between rotating blades and the stationary casing in high-pressure turbines is very complex and is one of the most important factors influencing turbine performance. The rotor with a winglet-cavity tip is often used as an effective method to improve the loss resulting from the tip clearance flow. In this study, an aerodynamic geometric optimisation of a winglet-cavity tip was carried out in a linear unshrouded high-pressure axial turbine cascade. For the purpose of shaping the efficient winglet geometry of the rotor tip, a novel parameterisation method has been introduced in the optimisation procedure based on the computational fluid dynamics simulation and analysis. The reliability of a commercial computational fluid dynamics code with different turbulence models was first validated by contrasting with the experimental results, and the numerical total pressure loss and flow angle using the Baseline k-omega Model (BSL κ-ω model) shows a better agreement with the test data. Geometric parameterisation of blade tips along the pressure side and suction side was adopted to optimise the tip clearance flow, and an optimal winglet-cavity tip was proven to achieve lower tip leakage mass flow rate and total pressure loss than the flat tip and cavity tip. Compared to the numerical results of flat tip and cavity tip, the optimised winglet-cavity design, with the winglet along the pressure side and suction side, had lower tip leakage mass flow rate and total pressure loss. It offered a 35.7% reduction in the change ratio [Formula: see text]. In addition, the optimised winglet along pressure side and suction side, respectively, by using the parameterisation method was studied for investigating the individual effect of the pressure-side winglet and suction-side winglet on the tip clearance flow. It was found that the suction-side extension of the optimal winglet resulted in a greater reduction of aerodynamic loss and leakage mass flow than the pressure-side extension of the optimal winglet. Moreover, with the analysis based on the tip flow pattern, the numerical results show that the pressure-side winglet reduced the contraction coefficient, and the suction-side winglet reduced the aerodynamic loss effectively by decreasing the driving pressure difference near the blade tips, the leakage flow velocity, and the interaction between the leakage flow and the main flow. Overall, a better aerodynamic performance can be obtained by adopting the pressure-side and suction-side winglet-cavity simultaneously.

Axisymmetric Tip Gap Profiling in a Shroudless Axial Turbine

2020 ◽  
Author(s):  
M. Abda ◽  
M. G. Rose
Keyword(s):  
Mass Flow ◽  
Separation Bubble ◽  
Suction Side ◽  
Entropy Generation Rate ◽  
Tip Leakage Flow ◽  
Axial Turbine ◽  
Tip Leakage ◽  
Blade Tip ◽  
Design Value ◽  
Tip Mass

Abstract The inevitable gap between the rotor tips and the casing promotes flow leakage driven by the pressure difference between the pressure side and suction side of the blade. Axisymmetric tip gap profiling was applied at the blade tip and the casing endwall to reduce the tip leakage maintaining the same gap clearance. The investigation was held on a shroudless single stage axial turbine designed in ETH Zurich University named LISA D. The numerical calculation showed that axisymmetric tip gap profiling reduced the tip leakage flow and improved the efficiency by 0.65% and 0.1% respectively. However, the stage mass flow increased and as a result so did the rotor capacity. When the stage mass flow was reduced to the design value to maintain the design capacity, the effect of the axisymmetric tip gap profiling further improved, due to a reduction in the entropy generation rate of the tip leakage and passage vortices. The tip mass flow reduced by 2.39% and the efficiency improved significantly by 0.6%. It was observed that the tip profiling increased the size of the separation bubble in the PS/tip junction, which increased blockage effect in the gap. Hence, reduced the leaking flow to the SS, which results in weaker tip leakage vortex and its associated losses.

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