RELATIVE CASING MOTION EFFECT ON SQUEALER TIP COOLING PERFORMANCE AT TIGHT TIP CLEARANCE

2020 ◽  
pp. 1-18
Author(s):  
Diwei Zhu ◽  
Qiang Zhang ◽  
Shaopeng Lu ◽  
Jinfang Teng
Keyword(s):  
Thermal Load ◽  
Tip Clearance ◽  
Cooling Efficiency ◽  
Suction Surface ◽  
Cooling Performance ◽  
High Thermal Load ◽  
Blade Tip ◽  
Motion Effect ◽  
Cfd Method ◽  
The Impact

Abstract The effect of relative motion between the casing and turbine blade tip has been recognized as an important factor for tip aerothermal performance evaluation. Tight tip clearance is becoming one of the main objectives of engine manufacturers. This paper provides some insights on the topic that the impact of casing motion on the blade tip thermal performance could be different between nominal and tight tip clearances. A typical squealer tip geometry was employed, with coolant holes on the cavity floor near the pressure side rim. Three tip clearances, 1.1%, 0.6% and 0.2% of the span, are compared. The CFD method was validated against experimental data in the previous study. The results suggest that, in the tight tip situation, the effect of casing motion on cooling efficiency and flow structure is distinguished from the larger clearance situations. The scraping effect drives the leakage flow towards the blade suction surface, inducing high thermal load at tight clearance. The findings in this study highlight the importance of relative casing motion, especially at tight clearance.

Sensitivity Analysis and Experimental Validation of Transient Performance Predictions for a Short-Range Turbofan

2016 ◽  
Author(s):  
Maria V. Culmone ◽  
Nicolás Garcia-Rosa ◽  
Xavier Carbonneau
Keyword(s):  
Short Range ◽  
Engine Performance ◽  
Sensitivity Study ◽  
Simulation Software ◽  
Tip Clearance ◽  
Mass Storage ◽  
Transient Effects ◽  
Transient Model ◽  
Blade Tip ◽  
The Impact

Transient effects are important features of engine performance calculations. The aim of this paper is to analyze a new, fully transient model implemented using the PRopulsion Object Oriented Simulation Software (PROOSIS) for a civil, short range turbofan engine. A transient turbofan model, including the mechanical inertia effect has been developed in PROOSIS. Specific physical effects such as heat soakage, mass storage, blade tip clearance and combustion delay have been implemented in the relevant components of PROOSIS to obtain a fully transient model. Since a large number of components are concerned by all the transient effects, an influence study is presented to determine which are the most critical effects, and in which components. Inertia represents the relevant phenomenon, followed by thermal effects, combustion delay and finally mass storage. The comparison with experimental data will provide a first validation of the model. Finally a sensitivity study is reported to assess the impact of uncertain knowledge of key input parameters in the response time prediction accuracy.

Effect of blade tip grooving on the performance of an axial fan at different tip clearances in the absence and presence of inlet guide vanes

2019 ◽  
Vol 234 (1) ◽  
pp. 72-84
Author(s):  
Masoud Kharati-Koopaee ◽  
Hossein Moallemi
Keyword(s):  
Numerical Study ◽  
Guide Vane ◽  
Pressure Coefficient ◽  
Tip Clearance ◽  
Axial Fan ◽  
Guide Vanes ◽  
Inlet Guide Vanes ◽  
Blade Tip ◽  
Torque Coefficient ◽  
The Impact

This research aims at the numerical study of the blade tip grooving effect on the performance of a ducted axial fan at different tip clearances in the absence and presence of inlet guide vanes. To do this, significant parameters of the fan (i.e. pressure and torque coefficients as well as fan efficiency) comprising single- and double-grooved tips are evaluated and compared with those of the original fan. Validation of the considered numerical model is performed through comparison of the numerical findings with experimental results of a single-stage ducted fan, which comprises a set of 37 guide vane and 24-blade rotor rotating at the speed of 3600 r/min. Results reveal that grooving the blade tip causes the fan parameters to increase and higher fan parameters could be attained adopting single-grooved tip. It is shown that employing grooved blades causes the sensitivity of fan parameters to the change in the tip clearance to diminish. Results exhibit that the impact of grooving the blade on the reduction of sensitivity of fan parameters to the change in the tip clearance for the single-grooved tip in the absence of guide vanes is more remarkable than the other cases and in this case, as the tip clearance increases from the lower to the upper considered value, the decreased percentages in pressure coefficient, torque coefficient, and fan efficiency are 29.8%, 8.9%, and 22.8%, respectively. Numerical findings show that the influence of grooving the blade on the fan parameters in the presence of guide vanes is lower than that without guide vanes and in the presence of guide vanes, the highest average increase percentages in pressure coefficient, torque coefficient, and fan efficiency relative to those of the original fan, which is observed in the single grooved tip, are 3.1%, 1.4%, and 1.7%, respectively.

Cooling Efficiency for Assessing the Cooling Performance of an Effusion Cooled Combustor Liner

2013 ◽  
Author(s):  
B. Wurm ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
M. Gerendas
Keyword(s):  
Heat Fluxes ◽  
Main Flow ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Cooling Efficiency ◽  
Transfer Coefficients ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Thermal Investigations ◽  
The Impact

Based on experimental results on a liner of a modern direct lean injection combustion chamber using coolant ejection from both effusion cooling holes and a starter film, a method is presented that allows the assessment of the cooling performance of the liner. As the main focus of the present study is a deeper understanding of the interaction of swirl flow and near wall cooling flow, wall pressure measurements are performed for the calculation of local blowing ratios and local coolant mass fluxes. Thermal investigations allow the calculation of adiabatic film cooling effectiveness and heat transfer coefficients. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure of the main flow. As experiments are performed without combustion and at low temperature, the influence of radiation is neglected. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by detailed PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas. For the definition of the non dimensional cooling efficiency the measurement area is sub divided into rhombic sections, which are located around each effusion cooling hole. Based on the measurement results presented, heat fluxes per unit area can then be calculated and put together to the cooling efficiency.

scholarly journals Turbine Blade Tip External Cooling Technologies

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 90 ◽  
Author(s):  
Song Xue ◽  
Wing Ng
Keyword(s):  
Turbine Blade ◽  
Recent Progress ◽  
Tip Clearance ◽  
New Techniques ◽  
Cooling Performance ◽  
Tip Leakage ◽  
Blowing Ratio ◽  
External Cooling ◽  
Blade Tip ◽  
Cooling Technology

This article provides an overview of gas turbine blade tip external cooling technologies. It is not the intention to comprehensively review all the publications from past to present. Instead, selected reports, which represent the most recent progress in tip cooling technology in open publications, are reviewed. The cooling performance on flat tip and squealer tip blades from reports are compared and discussed. As a generation conclusion, tip clearance dimension and coolant flow rate are found as the most important factors that significant influence the blade tip thermal performance was well as the over tip leakage (OTL) flow aerodynamics. However, some controversial trends are reported by different researchers, which could be attributed to various reasons. One of the causes of this disagreement between different reports is the lacking of unified parametric definition. Therefore, a more appropriate formula of blowing ratio definition has been proposed for comparison across different studies. The last part of the article is an outlook of the new techniques that are promising for future tip cooling research. As a new trend, the implementation of artificial intelligence techniques, such as genetic algorithm and neural network, have become more popular in tip cooling optimization, and they will bring significantly changes to the future turbine tip cooling development.

Exploring the Impact of Manufacturing Geometric Uncertainties on the Aerodynamic Performance of a Small Scale Compressor

2018 ◽  
Author(s):  
Kailash Manohara Selvan ◽  
Lukasz Kowalczyk
Keyword(s):  
Monte Carlo ◽  
Robust Design ◽  
Tool Path ◽  
Pressure Rise ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Robust Design Optimization ◽  
Small Scale ◽  
Suction Surface ◽  
The Impact

The performance of small scale compressors mass-produced for domestic appliances is influenced by geometric manufacturing uncertainty which affects overall product performance and reliability. Precise manufacturing processes through tighter tolerances ensure high geometric accuracy and lower compressor performance spread, but it challenges high volume production capabilities and cost. Good understanding of geometric sensitivities is necessary for robust design and tolerance definition. This paper presents the application of geometric Sensitivity Analysis (SA), Uncertainty Quantification (UQ) and robust optimization method to a small scale compressor. Geometric SA was carried out on parametric blade geometry and the key influential parameters were identified. The tip clearance was found to be the most influential parameter followed by a blade surface thickness. The tip section of the blade was more influential than hub section and the suction surface was found to be more important than the pressure surface. Findings from the SA were used to define parameters that were measured and controlled to ensure impeller quality during production. Within the parametric bounds studied, impeller chord did not feature as a critical parameter. The machining tool path was optimized accordingly and a 12% reduction in cutting time was achieved. The numerical sensitivities were also compared with experimental data and a trend-level agreement was seen. Meta-models for aerodynamic performance were built using DoE generated geometries which were used to perform manufacturing UQ using a Monte Carlo estimator. Robust design optimization was carried out using stochastic optimization algorithm coupled with the meta-model based Monte-Carlo simulator. This framework was used to choose a robust nominal shape that achieved 18% lower standard deviation in stage pressure rise. The predicted performance spread was compared with production data and a satisfactory agreement was seen.

scholarly journals The Impact of Realistic Casing Geometries and Clearances on Fan Blade Tip Aerodynamics

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Alistair John ◽  
Ning Qin ◽  
Shahrokh Shahpar
Keyword(s):  
Engine Performance ◽  
Leading Edge ◽  
Tip Clearance ◽  
Blade Design ◽  
Engine Operation ◽  
Surface Method ◽  
Flow Features ◽  
Blade Tip ◽  
Fan Blade ◽  
The Impact

During engine operation, fan casing abradable liners are worn by the blade tip, resulting in the formation of trenches. This paper describes the influence of these trenches on the fan blade tip aerodynamics. A detailed understanding of the fan tip flow features for cropped and trenched clearances is first developed. A parametric model is then used to model trenches in the casing above the blade tip and varying blade tip positions. It is shown that increasing clearance via a trench reduces performance by less than increasing clearance through cropping the blade tip. A response surface method is then used to generate a model that can predict fan efficiency for a given set of clearance and trench parameters. This model can be used to influence fan blade design and understand engine performance degradation in service. It is shown that an efficiency benefit can be achieved by increasing the amount of tip rubbing, leading to a greater portion of the tip clearance sat within the trench. It is shown that the efficiency sensitivity to clearance is biased toward the leading edge (LE) for cropped tips and the trailing edge (TE) for trenches.

Influence of Tip Clearance on the Inter Blade and Exit Flow Field of a Turbine Rotor Cascade

1994 ◽  
Author(s):  
M. Govardhan ◽  
N. Venkatrayulu ◽  
V. S. Vishnubhotla
Keyword(s):  
Static Pressure ◽  
Leading Edge ◽  
Turbine Rotor ◽  
Tip Clearance ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Static Pressure Distribution ◽  
Blade Tip ◽  
Flow Through ◽  
Downstream Flow

A detailed study of flow through the blade passage and downstream of a linear turbine cascade was carried out for four cases of tip clearance including zero clearance. Apart from inlet traverse, a total of eight stations were chosen for inter-blade flow traversing between 5% and 95% of axial chord from leading edge. Downstream flow surveys were made at distances of 106% of axial chord from the blade leading edge. Pitchwise and spanwise traverses were conducted for each tip clearance at these stations using a small five hole probe. Provision was also made for the measurement of static pressure distribution on the suction and pressure surfaces and also on the blade tip surface when clearance is present. At about 40% of axial chord from the leading edge, the presence of clearance vortex is identified inside the passage. The growth of the clearance vortex in size, its movement towards the suction surface and its increase in strength with the gap size were observed beyond 55% of axial chord till the trailing edge region. The rate of growth of the losses in the endwall region increased with clearance. Horse shoe vortex was not observed for the highest clearance. The overall losses increase rapidly with clearance in the rear half of the blade.

Parametrical Investigation of Turbine Stages With Open Tip Clearance for the Purpose of Stage Efficiency Increase

2010 ◽  
Author(s):  
Andrei Granovskiy ◽  
Mikhail Kostege ◽  
Nikolay Lomakin
Keyword(s):  
Pressure Ratio ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Turbine Stage ◽  
Suction Surface ◽  
Tip Leakage ◽  
Degree Of Reaction ◽  
Blade Tip ◽  
Stage Efficiency

The aerodynamic loss due to tip leakage vortex of rotor blades represents a significant part of viscous losses in axial flow turbines. The mixing of leakage flow with the main rotor passage flow causes losses and reduces turbine stage efficiency. Many measures have been proposed to reduce the loss in the tip clearance area. In this paper the reduction of the tip clearance loss due to changes made to the blade tip section profile is presented. The blade tip profile was modified to decrease the pressure gradient between pressure surface and suction surface. This approach allows the reduction of tip leakage and tip vortex strength and consequently the reduction of tip clearance losses. A 3D Navier-Stokes solver with q-ω turbulence model is used to analyze the flow in the turbine with various tip section profiles. Test data of three single-stage experimental turbines have been used to validate analytical predictions: • Highly loaded turbine stage with a pressure ratio π0T = 3.2 and reaction degree ρmean = 0.5. • Two turbines with a pressure ratio π0T = 3.9. (One with high degree of reaction ρmean = 0.55; the other with low degree of reaction ρmean = 0.26). The numerical investigation of the influence of various tip section profiles on stage efficiency was carried out in the range of relative tip clearance 0.5%–2.4% with the objective of a decreasing the influence of the tip clearance on the stage efficiency.

Thermal Validation of a Heat Shield Surface for a High Lift Blade Profile

2011 ◽  
Author(s):  
M. Cochet ◽  
W. Colban ◽  
M. Gritsch ◽  
S. Naik ◽  
M. Schnieder
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Heat Shield ◽  
Transfer Coefficients ◽  
High Lift ◽  
Heat Transfer Coefficients ◽  
Blade Tip ◽  
The Impact

Low emission requirements for heavy-duty gas turbines can be achieved with flat combustor temperature profiles, reducing the combustor peak temperature. As a result, the heat load on the first stage heat shield above the first stage blade increases. High lift airfoils cause increased thermal loading on the heat shield above the blade tip and impact the unavoidable secondary flows, including complex vortex flows. Cascade tests have been performed on a blade with a generic high lift profile and the results on the heat shield are presented. A transient thermochromic liquid crystal measurement technique was used to obtain heat transfer coefficients on the heat shield surface. Several variations of blade tip clearance were investigated, and the impact on heat transfer coefficients is shown. Computational fluid dynamics predictions are compared to the experimental data to interpret the data and validate the CFD.

scholarly journals The Tip Clearance Cavitation Mechanism of a High-Speed Centrifugal Pump with a Splitter-Bladed Inducer

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1576
Author(s):  
Xiaomei Guo ◽  
Shidong Yang ◽  
Xiaojun Li ◽  
Liang Shi ◽  
Ertian Hua ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
High Performance ◽  
Static Pressure ◽  
Tip Clearance ◽  
Small Range ◽  
Suction Surface ◽  
Static Pressure Distribution ◽  
The Impact ◽  
External Characteristics

For a high-speed centrifugal pump, cavitation occurs easily. To equip a high-performance splitter-bladed inducer upstream of the pump is an effective method to suppress cavitation. In this paper, an external characteristics experiment of the high-speed centrifugal pump with a splitter-bladed inducer is carried out, and the corresponding numerical calculations are completed. The research shows that the results of the numerical calculation are credible. Numerical cavitation calculations under eight different tip clearance conditions are carried out. First, it is found that the tip clearance (TC) has a certain impact on the head of the centrifugal pump. When TC is in a small range, the clearance leakage is small, and the impact on the head of the pump is not so obvious, which can give the pump a higher performance. Second, it is found that TC has a certain influence on the static pressure distribution in the cascade passage of the splitter-bladed inducer. When TC is in a certain range, the increasement in TC will aggravate the cavitation at the suction surface of the long blades near the inlet. When it exceeds the certain range, it will cause cavitation at the outlet of the inducer. At last, it is found that the cavitation’s severity and position of the inducer are closely related to TC. TC affects the magnitude and position of vorticity in the inducer’s passage. In this paper the flow mechanism of TC is revealed, and its research results can provide theoretical basis and technical support for the design of the tip clearance of the inducers.

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