scholarly journals Improved Modeling Capabilities of the Airflow Within Turbine Case Cooling Systems Using Smart Porous Media

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Yanling Li ◽  
A. Duncan Walker ◽  
John Irving
Keyword(s):  
Porous Media ◽  
Gas Turbines ◽  
Tip Clearance ◽  
Computational Time ◽  
Small Scale ◽  
Design Phase ◽  
Local Flow ◽  
Alternative Approach ◽  
Cooling Hole ◽  
Computational Fluid Dynamics Cfd

Impingement cooling is commonly employed in gas turbines to control the turbine tip clearance. During the design phase, computational fluid dynamics (CFD) is an effective way of evaluating such systems but for most turbine case cooling (TCC) systems resolving the small scale and large number of cooling holes is impractical at the preliminary design phase. This paper presents an alternative approach for predicting aerodynamic performance of TCC systems using a “smart” porous media (PM) to replace regions of cooling holes. Numerically CFD defined correlations have been developed, which account for geometry and local flow field, to define the PM loss coefficient. These are coded as a user-defined function allowing the loss to vary, within the calculation, as a function of the predicted flow and hence produce a spatial variation of mass flow matching that of the cooling holes. The methodology has been tested on various geometrical configurations representative of current TCC systems and compared to full cooling hole models. The method was shown to achieve good overall agreement while significantly reducing both the mesh count and the computational time to a practical level.

Design of an Improved Turbine Rim-Seal

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
James A. Scobie ◽  
Roy Teuber ◽  
Yan Sheng Li ◽  
Carl M. Sangan ◽  
Michael Wilson ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Navier Stokes ◽  
Computational Time ◽  
Gas Concentration ◽  
Engine Design ◽  
Successful Design ◽  
Purge Flow ◽  
Rotor Disk ◽  
Computational Fluid Dynamics Cfd ◽  
Improved Performance

Rim seals are fitted in gas turbines at the periphery of the wheel-space formed between rotor disks and their adjacent casings. These seals, also called platform overlap seals, reduce the ingress of hot gases which can limit the life of highly stressed components in the engine. This paper describes the development of a new, patented rim-seal concept showing improved performance relative to a reference engine design, using unsteady Reynolds-averaged Navier–Stokes (URANS) computations of a turbine stage at engine conditions. The computational fluid dynamics (CFD) study was limited to a small number of purge-flow rates due to computational time and cost, and the computations were validated experimentally at a lower rotational Reynolds number and in conditions under incompressible flow. The new rim seal features a stator-side angel wing and two buffer cavities between outer and inner seals: the angel-wing promotes a counter-rotating vortex to reduce the effect of the ingress on the stator; the two buffer cavities are shown to attenuate the circumferential pressure asymmetries of the fluid ingested from the mainstream annulus. Rotor disk pumping is exploited to reduce the sealing flow rate required to prevent ingress, with the rotor boundary layer also providing protective cooling. Measurements of gas concentration and swirl ratio, determined from static and total pressure, were used to assess the performance of the new seal concept relative to a benchmark generic seal. The radial variation of concentration through the seal was measured in the experiments and these data captured the improvements due to the intermediate buffer cavities predicted by the CFD. This successful design approach is a potent combination of insight provided by computation, and the flexibility and expedience provided by experiment.

Comparison of Detailed and Simplified Optimization Approaches for the Performance Simulation of Cogeneration Plants

2009 ◽  
Author(s):  
Stefano Campanari ◽  
Giampaolo Manzolini ◽  
Paolo Silva
Keyword(s):  
Gas Turbines ◽  
Management Strategies ◽  
Primary Energy ◽  
Pollutant Emissions ◽  
Computational Time ◽  
Plant Management ◽  
Small Scale ◽  
Optimization Strategy ◽  
Detailed Model ◽  
Partial Load

It is well known that cogeneration can be an effective energy-saving solution, able to achieve relevant reductions in primary energy consumption and pollutant emissions. Generally speaking, obtaining best performances from a cogeneration plant requires a proper design and a careful management, aiming to maximize the plant energy and economic savings. Solving the issue of optimization may require a dedicated simulation tool when the CHP plant faces variable loads (both electrical, thermal and in some cases cooling loads) and electricity tariffs, or significantly changes its efficiency at partial load, or integrates a heat storage which allows to extend the possible plant management strategies. In all these cases, the optimization results may not be easy predictable. However, in other cases also simpler and faster approaches may lead to correctly optimized results, depending on the application features. The purpose of this work is to compare two approaches to the optimization of trigeneration plants: (i) a detailed model already presented in previous works (DCOGEN), able to perform accurate optimization and prediction of annual energy balances but requiring detailed plant definition, accurate specifications of the user demands and a significant computational time, and (ii) a simplified and faster model based on few information and a intuitive optimization strategy. The comparison is carried out for two cases, reflecting the features of industrial CHP applications based on small scale gas turbines and reciprocating engines. Results show the advantages given by the detailed model as well as the limits of simplified approaches.

Predicting the Adiabatic Effectiveness of Effusion Cooling by the Convolution Modeling Method

2019 ◽  
Author(s):  
Li Yang ◽  
Yu Rao
Keyword(s):  
Gas Turbines ◽  
Thermal Load ◽  
Turbine Blades ◽  
Computational Time ◽  
Cooling Effectiveness ◽  
Proposed Model ◽  
Convolution Model ◽  
Adiabatic Cooling ◽  
Cooling Hole ◽  
Random Manner

Abstract Effusion Cooling has a strong potential in protecting hot section components of gas turbines engines such as turbine blades, endwalls and combustor liners. By carefully distributing the cooling holes adaptively to the external thermal load, effusion cooling can dramatically reduce the temperature and thermal stress for the protected components. However, the effectiveness for effusion cooling was not easy to correlate due to the numerous parameters to study and the significant variation from the upstream to the downstream. Conventional equations used in the literature were insufficient to express the complex mechanism for effusion cooling and consequently utilized averaged parameters as variables. This study proposed a convolution method to model the local adiabatic cooling effectiveness for the entire effusion cooled surfaces. The new model treated the cooling hole distribution as an input matrix and applied convolution networks to predict the cooling effectiveness. Compared with conventional correlations, this network based model provided extensive details of the cooling effectiveness distribution while consuming computational time as short as correlations. Training of the proposed model was based on the numerical simulation results of three geometries and the validation was conducted for two additional geometries. Results indicated high accuracy and high robustness of the convolution model. With the aid of this novel model, further designing could adjust hole distribution in a random manner instead of using rows and columns, and generate adaptive effusion cooling based on thermal load.

Comparison of LBM and FVM in the estimation of LAD stenosis

2021 ◽  
pp. 095441192110169
Author(s):  
Jian Liu ◽  
Yong Yu ◽  
Chenqi Zhu ◽  
Yu Zhang
Keyword(s):  
Stokes Equations ◽  
Flow Simulation ◽  
Diagnostic Methods ◽  
Computational Time ◽  
Speed Ratio ◽  
Maximum Speed ◽  
Fractional Flow ◽  
Local Flow ◽  
Non Invasive ◽  
Flow Reserve

The finite volume method (FVM)-based computational fluid dynamics (CFD) technology has been applied in the non-invasive diagnosis of coronary artery stenosis. Nonetheless, FVM is a time-consuming process. In addition to FVM, the lattice Boltzmann method (LBM) is used in fluid flow simulation. Unlike FVM solving the Navier–Stokes equations, LBM directly solves the simplified Boltzmann equation, thus saving computational time. In this study, 12 patients with left anterior descending (LAD) stenosis, diagnosed by CTA, are analysed using FVM and LBM. The velocities, pressures, and wall shear stress (WSS) predicted using FVM and LBM for each patient is compared. In particular, the ratio of the average and maximum speed at the stenotic part characterising the degree of stenosis is compared. Finally, the golden standard of LAD stenosis, invasive fractional flow reserve (FFR), is applied to justify the simulation results. Our results show that LBM and FVM are consistent in blood flow simulation. In the region with a high degree of stenosis, the local flow patterns in those two solvers are slightly different, resulting in minor differences in local WSS estimation and blood speed ratio estimation. Notably, these differences do not result in an inconsistent estimation. Comparison with invasive FFR shows that, in most cases, the non-invasive diagnosis is consistent with FFR measurements. However, in some cases, the non-invasive diagnosis either underestimates or overestimates the degree of stenosis. This deviation is caused by the difference between physiological and simulation conditions that remains the biggest challenge faced by all CFD-based non-invasive diagnostic methods.

Pressure Distributions in the Tip Clearance Region of an Unshrouded Axial Turbine as Affecting the Problem of Tip Burnout

1987 ◽  
Author(s):  
Jeffery P. Bindon
Keyword(s):  
Separation Bubble ◽  
Low Pressure ◽  
High Heat ◽  
Tip Clearance ◽  
Small Scale ◽  
Narrow Strip ◽  
Pressure Surface ◽  
High Heat Transfer ◽  
Axial Turbines ◽  
Secondary Vortices

The pressure distribution in the tip clearance region of a 2D turbine cascade was examined with reference to unknown factors which cause high heat transfer rates and burnout along the edge of the pressure surface of unshrouded cooled axial turbines. Using a special micro-tapping technique, the pressure along a very narrow strip of the blade edge was found to be 2.8 times lower than the cascade outlet pressure. This low pressure, coupled with a thin boundary layer due to the intense acceleration at gap entry, are believed to cause blade burnout. The flow phenomena causing the low pressure are of very small scale and do not appear to have been previously reported. The ultra low pressure is primarily caused by the sharp flow curvature demanded of the leakage flow at gap entry. The curvature is made more severe by the apparent attachement of the flow around the corner instead of immediately separating to increase the radius demanded of the flow. The low pressures are intensified by a depression in the suction corner and by the formation of a separation bubble in the clearance gap. The bubble creates a venturi action. The suction corner depression is due to the mainstream flow moving round the leakage and secondary vortices.

Development of the DLE Combustor for L30A Gas Turbine

2015 ◽  
Author(s):  
Toshiaki Sakurazawa ◽  
Takeo Oda ◽  
Satoshi Takami ◽  
Atsushi Okuto ◽  
Yasuhiro Kinoshita
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Nox Emission ◽  
Test Facility ◽  
Exhaust Temperature ◽  
Main Burner ◽  
Harmful Emissions ◽  
Emission Regulation ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses

This paper describes the development of the Dry Low Emission (DLE) combustor for L30A gas turbine. Kawasaki Heavy Industries, LTD (KHI) has been producing relatively small-size gas turbines (25kW to 30MW class). L30A gas turbine, which has a rated output of 30MW, achieved the thermal efficiency of more than 40%. Most continuous operation models use DLE combustion systems to reduce the harmful emissions and to meet the emission regulation or self-imposed restrictions. KHI’s DLE combustors consist of three burners, a diffusion pilot burner, a lean premix main burner, and supplemental burners. KHI’s proven DLE technologies are also adapted to the L30A combustor design. The development of L30 combustor is divided in four main steps. In the first step, Computational Fluid Dynamics (CFD) analyses were carried out to optimize the detail configuration of the combustor. In a second step, an experimental evaluation using single-can-combustor was conducted in-house intermediate-pressure test facility to evaluate the performances such as ignition, emissions, liner wall temperature, exhaust temperature distribution, and satisfactory results were obtained. In the third step, actual pressure and temperature rig tests were carried out at the Institute for Power Plant Technology, Steam and Gas Turbines (IKDG) of Aachen University, achieving NOx emission value of less than 15ppm (O2=15%). Finally, the L30A commercial validation engine was tested in an in-house test facility, NOx emission is achieved less than 15ppm (O2=15%) between 50% and 100% load operation point. L30A field validation engine have been operated from September 2012 at a chemical industries in Japan.

A comprehensive comparative investigation of the Lifting Line Theory and Blade Element Momentum Theory applied to small wind turbines

2021 ◽  
pp. 1-25
Author(s):  
K.A.R. Ismail ◽  
Willian Okita
Keyword(s):  
Wind Turbines ◽  
Power Coefficient ◽  
Computational Time ◽  
Local Flow ◽  
Small Wind Turbines ◽  
Wake Effects ◽  
Line Theory ◽  
Lifting Line ◽  
Lifting Line Theory ◽  
Blade Element

Abstract Small wind turbines are adequate for electricity generation in isolated areas to promote local expansion of commercial activities and social inclusion. Blade element momentum (BEM) method is usually used for performance prediction, but generally produces overestimated predictions since the wake effects are not precisely accounted for. Lifting line theory (LLT) can represent the blade and wake effects more precisely. In the present investigation the two methods are analyzed and their predictions of the aerodynamic performance of small wind turbines are compared. Conducted simulations showed a computational time of about 149.32 s for the Gottingen GO 398 based rotor simulated by the BEM and 1007.7 s for simulation by the LLT. The analysis of the power coefficient showed a maximum difference between the predictions of the two methods of about 4.4% in the case of Gottingen GO 398 airfoil based rotor and 6.3% for simulations of the Joukowski J 0021 airfoil. In the case of the annual energy production a difference of 2.35% is found between the predictions of the two methods. The effects of the blade geometrical variants such as twist angle and chord distributions increase the numerical deviations between the two methods due to the big number of iterations in the case of LLT. The cases analyzed showed deviations between 3.4% and 4.1%. As a whole, the results showed good performance of both methods; however the lifting line theory provides more precise results and more information on the local flow over the rotor blades.

Numerical Simulation of Insulin Depot Formation and Absorption in Subcutaneous Tissue Modeled as a Homogeneous Anisotropic Porous Media

2021 ◽  
Author(s):  
Michael Zedelmair ◽  
Abhijit Mukherjee
Keyword(s):  
Porous Media ◽  
Numerical Model ◽  
Insulin Pump ◽  
Subcutaneous Tissue ◽  
Saturated Porous Media ◽  
Anisotropic Porous Media ◽  
Effective Option ◽  
Computational Fluid Dynamics Cfd ◽  
Experimental Findings ◽  
Subcutaneous Adipose

Abstract In this study, a numerical model of the insulin depot formation and absorption in the subcutaneous adipose tissue is developed using the commercial Computational Fluid Dynamics (CFD) software. A better understanding of these mechanisms can be helpful in the development of new devices and cannula geometries as well as predicting the concentration of insulin in the blood. The injection method considered in this simulation is by the use of an insulin pump using a rapid acting U100 insulin analogue. The depot formation is analyzed running Bolus injections ranging from 5-15 units of insulin corresponding to 50-150µl. The insulin is injected into the subcutaneous tissue in the abdominal region. The tissue is modeled as a fluid saturated porous media. An anisotropic approach to define the tissue permeability is studied by varying the value of the porosity in parallel and perpendicular direction having an impact on the viscous resistance to the flow. Following recent experimental findings this configuration results in a disk shaped insulin depot. To be able to run the simulation over longer timeframes the depot formation model has been extended implementing the process of absorption of insulin from the depot. The developed model is then used to analyze the formation of the insulin depot in the tissue when using different flow rates and cannula geometries. The numerical model is an effective option to evaluate new cannula designs prior to the manufacturing and testing of prototypes, which are rather time consuming and expensive.

Effect of a Ceramic Matrix Composite Surface on Film Cooling

2021 ◽  
Author(s):  
Peter H. Wilkins ◽  
Stephen P. Lynch ◽  
Karen A. Thole ◽  
San Quach ◽  
Tyler Vincent ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Matrix Composite ◽  
Film Cooling ◽  
Gas Turbines ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix ◽  
Composite Surface ◽  
Minimal Impact ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

Abstract Ceramic matrix composite (CMC) parts create the opportunity for increased turbine entry temperatures within gas turbines. To achieve the highest temperatures possible, film cooling will play an important role in allowing turbine entry temperatures to exceed acceptable surface temperatures for CMC components, just as it does for the current generation of gas turbine components. Film cooling over a CMC surface introduces new challenges including roughness features downstream of the cooling holes and changes to the hole exit due to uneven surface topography. To better understand these impacts, this study presents flowfield and adiabatic effectiveness CFD for a 7-7-7 shaped film cooling hole at two CMC weave orientations. The CMC surface selected is a 5 Harness Satin weave pattern that is examined at two different orientations. To understand the ability of steady RANS to predict flow and convective heat transfer over a CMC surface, the weave surface is initially simulated without film and compared to previous experimental results. The simulation of the weave orientation of 0°, with fewer features projecting into the flow, matches fairly well to the experiment, and demonstrates a minimal impact on film cooling leading to only slightly lower adiabatic effectiveness compared to a smooth surface. However, the simulation of the 90° orientation with a large number of protruding features does not match the experimentally observed surface heat transfer. The additional protruding surface produces degraded film cooling performance at low blowing ratios but is less sensitive to blowing ratio, leading to improved relative performance at higher blowing ratios, particularly in regions far downstream of the hole.

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