Experimental and Numerical Study on the Use of Guide Vanes in the Dilution Zone

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Osama M. Selim ◽  
Tarek Elgammal ◽  
Ryoichi S. Amano
Keyword(s):  
Pressure Drop ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Turbine Blades ◽  
Uniform Temperature ◽  
Guide Vanes ◽  
Fluid Forces ◽  
Critical Components

Abstract The importance of gas turbine blades is to convert the thermal energy into shaft work output, which makes the turbine blades as one of the critical components of the gas turbines. Besides the mechanical stresses caused by the centrifugal force and the fluid forces, the thermal stresses arise because of the temperature gradient within the blade materials. This paper aims to have a uniform circumferential temperature field at the combustor exit, consequently reducing the thermal stresses caused by the non-uniform temperature distribution along the turbine blade. The validation of the simulation results with the experiments showed an acceptable agreement with the available experimental data. The agreement includes the uniformity factor and the normalized mixture fraction at two different flowrates. Furthermore, another location of the guide vanes, external guide vanes, was experimentally and numerically tested. The results show that the external guide vanes with a 30 deg orientation gave the most uniform temperature flow for the two different flowrates. Compared with the internal guide vanes with the same orientation, the external guide vanes gave a 7.5% higher uniformity factor and a 2% lower pressure drop. The main reason for this result is that the external guide vanes direct the cold stream to penetrate the dilution zone with an angle enhance the swirling effect which are the main factors for excellent mixing, while the pressure drop is lower as the external guide vanes are facing the lower flowrate which is the secondary stream. Another advantage of the external guide vanes over the internal ones is that they are subjected to less thermal stresses as they are facing the cold flow. Furthermore, the external guide vanes are reachable and easy to maintain compared with the internal guide vanes.

Computational Analysis of Mixing in a Gas Turbine Combustor

2012 ◽  
Author(s):  
Alka Gupta ◽  
Mohamed Saeed Ibrahim ◽  
R. S. Amano
Keyword(s):  
Gas Turbines ◽  
Computational Analysis ◽  
Blunt Body ◽  
Mixture Fraction ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Equilibrium Mixture ◽  
Reacting Flow ◽  
Uniform Temperature ◽  
Combustion Gases

This paper presents the computational analysis of the dilution process involved in gas turbines order to cool the combustion gases to the desired temperature before it enters the turbine. Here, it should be noted that in order to focus only on the dilution process, non-reacting flow conditions were simulated and the complete system was reduced to mixing of a primary (hot) stream and dilution (cold) stream of air. Four different schemes were investigated based on the layout of the dilution holes and use of a blunt body. A complete three dimensional analysis was carried out for each case in order to investigate its effectiveness to produce a more uniform temperature conditions at the exit of the combustor, so as to reduce the detrimental effect these temperature non-uniformities have on the turbine blades. For comparison of the proposed schemes, a parameter is defined in terms of the temperatures of the dilution and primary flow streams at the inlet and the exit plane, called the mixture fraction. Based on this parameter, it was found that the staggered dilution holes with the blunt body has the mixture fraction closest to the equilibrium mixture fraction (0.4), which implies that this scheme with the mixture fraction of 0.36, resulted in best mixing and produced the most uniform temperature distribution at the exit amongst the four proposed schemes.

Crystal Visco-Plastic Model for Directionally Solidified Ni-Base Superalloys Under Monotonic and Low Cycle Fatigue

2021 ◽  
Author(s):  
Navindra Wijeyeratne ◽  
Firat Irmak ◽  
Ali P. Gordon
Keyword(s):  
Grain Boundaries ◽  
Gas Turbines ◽  
Thermal Stresses ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Material Behavior ◽  
Flow Rule ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Crystallographic Slip

Abstract Nickel-base superalloys (NBSAs) are extensively utilized as the design materials to develop turbine blades in gas turbines due to their excellent high-temperature properties. Gas turbine blades are exposed to extreme loading histories that combine high mechanical and thermal stresses. Both directionally solidified (DS) and single crystal NBSAs are used throughout the industry because of their superior tensile and creep strength, excellent low cycle fatigue (LCF), high cycle fatigue (HCF), and thermomechanical fatigue (TMF) capabilities. Directional solidification techniques facilitated the solidification structure of the materials to be composed of columnar grains in parallel to the <001> direction. Due to grains being the sites of failure initiation the elimination of grain boundaries compared to polycrystals and the alignment of grain boundaries in the normal to stress axis increases the strength of the material at high temperatures. To develop components with superior service capabilities while reducing the development cost, simulating the material’s performance at various loading conditions is extremely advantageous. To support the mechanical design process, a framework consisting of theoretical mechanics, numerical simulations, and experimental analysis is required. The absence of grain boundaries transverse to the loading direction and crystallographic special orientation cause the material to exhibit anisotropic behavior. A framework that can simulate the physical attributes of the material microstructure is crucial in developing an accurate constitutive model. The plastic flow acting on the crystallographic slip planes essentially controls the plastic deformation of the material. Crystal Visco-Plasticity (CVP) theory integrates this phenomenon to describe the effects of plasticity more accurately. CVP constitutive models can capture the orientation, temperature, and rate dependence of these materials under a variety of conditions. The CVP model is initially developed for SX material and then extended to DS material to account for the columnar grain structure. The formulation consists of a flow rule combined with an internal state variable to describe the shearing rate for each slip system. The model presented includes the inelastic mechanisms of kinematic and isotropic hardening, orientation, and temperature dependence. The crystallographic slip is accounted for by including the required octahedral, cubic, and cross slip systems. The CVP model is implemented through a general-purpose finite element analysis software (i.e., ANSYS) as a User-Defined Material (USERMAT). Uniaxial experiments were conducted in key orientations to evaluate the degree of elastic and inelastic anisotropy. The temperature-dependent modeling parameter is developed to perform non-isothermal simulations. A numerical optimization scheme is utilized to develop the modeling constant to improve the calibration of the model. The CVP model can simulate material behavior for DS and SX NBSAs for monotonic and cyclic loading for a range of material orientations and temperatures.

Computational and Experimental Study of Enhanced Mixing in a Gas Turbine Combustor Using Guide Vanes

2013 ◽  
Author(s):  
Alka Gupta ◽  
Mohammed Saeed Ibrahim ◽  
Benjamin Wiegand ◽  
Ryoichi Amano
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Film Cooling ◽  
Mixture Fraction ◽  
Effective Means ◽  
Turbine Blades ◽  
Primary Flow ◽  
Guide Vanes ◽  
Exit Nozzle ◽  
Blade Failure

A number of studies have shown that the flow field exiting a combustor of a gas turbine cycle is highly non-uniform in pressure, velocity and, most importantly, temperature. Much research has been dedicated to the cooling of gas turbine blades using internal, film cooling, impingement jets, and pin/fin cooling technologies. Such designs allow for heated blades to be cooled from the inside out. While advancements in this type of blade cooling technology provide effective means to reduce the occurrence of blade failure due to material overheat conditions, the effect of externally reducing or eliminating the temperature non-uniformities in the exit flow from the combustor would assist in the solution. The goal of this study is to optimize the mixing of primary and dilution air in the dilution zone of the combustor using guide vanes. This improvement in mixing would lead to increase in the degree of temperature uniformity with respect to the radial position at the exit nozzle. To achieve this objective, both experimental and computational studies were performed to investigate the heat and flow behaviors with 45° spherically swept guide vanes attached to the dilution holes. These guide vanes were intended to direct the dilution jets into the primary flow and enhance mixing. A parameter was defined in terms of the temperatures of the dilution and primary flow streams at the inlet and the exit plane, called the mixture fraction. Based on the mixture fraction value, it was found that the guide vanes produce a more uniform exit temperature flow field as compared to the case when there were no guide vanes used. Also, the design was modified for different alignment orientations of the guide vanes — 0°, 30°, 60° and 90° with respect to the primary flow — with the 60° orientation fostering the best results.

scholarly journals Effects of Damaged Rotor Blades on the Aerodynamic Behavior and Heat-Transfer Characteristics of High-Pressure Gas Turbines

Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 627
Author(s):  
Thanh Dam Mai ◽  
Jaiyoung Ryu
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Rotor Blade ◽  
High Speed ◽  
Power Plants ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Combined Cycle

Gas turbines are critical components of combined-cycle power plants because they influence the power output and overall efficiency. However, gas-turbine blades are susceptible to damage when operated under high-pressure, high-temperature conditions. This reduces gas-turbine performance and increases the probability of power-plant failure. This study compares the effects of rotor-blade damage at different locations on their aerodynamic behavior and heat-transfer properties. To this end, we considered five cases: a reference case involving a normal rotor blade and one case each of damage occurring on the pressure and suction sides of the blades’ near-tip and midspan sections. We used the Reynolds-averaged Navier-Stokes equation coupled with the k − ω SST γ turbulence model to solve the problem of high-speed, high-pressure compressible flow through the GE-E3 gas-turbine model. The results reveal that the rotor-blade damage increases the heat-transfer coefficients of the blade and vane surfaces by approximately 1% and 0.5%, respectively. This, in turn, increases their thermal stresses, especially near the rotor-blade tip and around damaged locations. The four damaged-blade cases reveal an increase in the aerodynamic force acting on the blade/vane surfaces. This increases the mechanical stress on and reduces the fatigue life of the blade/vane components.

Developing an Application for Refractory Open Cell Metal Foams in Jet Engines

2004 ◽  
Vol 851 ◽  
Author(s):  
Wassim E. Azzi ◽  
William L. Roberts ◽  
Afsaneh Rabiei
Keyword(s):  
Pressure Drop ◽  
Gas Turbines ◽  
High Speed ◽  
Infrared Imaging ◽  
Metal Foam ◽  
Turbine Blades ◽  
Metal Foams ◽  
Thermodynamic Efficiency ◽  
Open Cell ◽  
The Difference

ABSTRACTThe thermodynamic efficiency of the Brayton cycle, upon which all gas turbines (aeropropulsion and power generation) are based on scales with the peak operating temperature. However, the peak temperature is limited by the turbine blades and the temperature they can withstand. The highest temperatures in the gas turbine occur in the combustor region but these temperatures are often too high for turbine blades. As a result, the combustion products must be diluted with relatively cooler air from the compressor to reduce the temperature to tolerable levels for the turbine blades. This research suggests placing a ring of high temperature open cell metal foam between the combustors and turbine sections of the jet engine to mix and average the difference in temperatures resulting from the cooling schemes in combustor cans. Temperature mixing effect was tested using a special setup with the application of an infrared camera and streams of hot and cold air passing through the foam. High speed flow pressure drop around Mach 1 (340 m/s) was done on the same foam samples to understand pressure drop in the compressible regime of air. Infrared imaging showed that open cell metal foams successfully mixed and averaged the difference in temperatures of the hot and cold gasses thus creating a more uniform temperature profile while pressure drop testing revealed that open cell metal foams result in minimal pressure drop at high flows especially when the increase in temperature in taken into consideration.

scholarly journals Wear Characteristics of Superalloy and Hardface Coatings in Gas Turbine Applications–A Review

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1171
Author(s):  
Ahmad Afiq Pauzi ◽  
Mariyam Jameelah Ghazali ◽  
Wan Fathul Hakim W. Zamri ◽  
Armin Rajabi
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Research Field ◽  
Fatigue Wear ◽  
Hastelloy X ◽  
Hot Gas ◽  
Hard Particles ◽  
Critical Components ◽  
Improve Wear Resistance

In the gas-turbine research field, superalloys are some of the most widely used materials as they offer excellent strength, particularly at extreme temperatures. Vital components such as combustion liners, transition pieces, blades, and vanes, which are often severely affected by wear, have been identified. These critical components are exposed to very high temperatures (ranging from 570 to 1300 °C) in hot-gas-path systems and are generally subjected to heavy repair processes for maintenance works. Major degradation such as abrasive wear and fretting fatigue wear are predominant mechanisms in combustion liners and transition pieces during start–stop or peaking operation, resulting in high cost if inadequately protected. Another type of wear-like erosion is also prominent in turbine blades and vanes. Nimonic 263, Hastelloy X, and GTD 111 are examples of superalloys used in the gas-turbine industry. This review covers the development of hardface coatings used to protect the surfaces of components from wear and erosion. The application of hardface coatings helps reduce friction and wear, which can increase the lifespan of materials. Moreover, chromium carbide and Stellite 6 hardface coatings are widely used for hot-section components in gas turbines because they offer excellent resistance against wear and erosion. The effectiveness of these coatings to mitigate wear and increase the performance is further investigated. We also discuss in detail the current developments in combining these coating with other hard particles to improve wear resistance. The principles of this coating development can be extended to other high-temperature applications in the power-generation industry.

A Probabilistic Machine Learning Framework for Explicit Inverse Design of Industrial Gas Turbine Blades

2021 ◽  
Author(s):  
Sayan Ghosh ◽  
Valeria Andreoli ◽  
Govinda A. Padmanabha ◽  
Cheng Peng ◽  
Steven Atkinson ◽  
...  
Keyword(s):  
Machine Learning ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Inverse Design ◽  
Learning Framework ◽  
Industrial Gas Turbines ◽  
Critical Components ◽  
Turbine Blade Design ◽  
The Individual ◽  
Probabilistic Machine Learning

Abstract One of the critical components in Industrial Gas Turbines (IGT) is the turbine blade. Design of turbine blades needs to consider multiple aspects like aerodynamic efficiency, durability, safety and manufacturing, which make the design process sequential and iterative. The sequential nature of these iterations forces a long design cycle time, ranging from a several months to years. Due to the reactionary nature of these iterations, little effort has been made to accumulate data in a manner that allows for deep exploration and understanding of the total design space. This is exemplified in the process of designing the individual components of the IGT resulting in a potential unrealized efficiency. To overcome the aforementioned challenges, we demonstrate a probabilistic inverse design machine learning framework, namely Pro-ML IDeAS, to carry out an explicit inverse design. Pro-ML IDeAS calculates the design explicitly without costly iteration and overcomes the challenges associated with ill-posed inverse problems. In this work the framework will be demonstrated on inverse aerodynamic design of 2D airfoil of turbine blades.

Pressure Losses for Jet Array Impingement With Crossflow

2012 ◽  
Author(s):  
Yeshayahou Levy ◽  
Arvind G. Rao ◽  
V. Erenburg ◽  
V. Sherbaum ◽  
I. Gaissinski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Numerical Simulations ◽  
Gas Turbines ◽  
Total Pressure ◽  
Turbine Blades ◽  
Jet Impingement ◽  
Solar Panels ◽  
Cfd Simulations ◽  
Pressure Losses

Jet impingement is an efficient heat transfer method and has been used successfully in cooling of turbine blades in gas turbine engines. Although many studies have been conducted on the heat transfer characteristics of jet impingement array, there is a lack of knowledge in pressure drop characteristics of large jet impingement arrays. The pressure losses encountered are becoming increasingly important when applied to micro gas turbines, cooling concentrated solar panels and high density electronic chips. The present work focuses on experimental and theoretical investigation of pressure losses in low Re impingement arrays, 200< Re <3000. Experiments were carried out on jet impingement array with nozzle diameters of 200 to 800 μm. Numerical simulations were also performed with available commercial CFD tools. Reasonable comparisons between experimental results and numerical simulations were obtained. Detailed flow structure, mass flow rate distribution, jet velocity profiles, and pressure drop within the array in the streamwise direction were obtained from the CFD simulations. These simulations enhance the understanding of the physics within multiple jet impingement system. Additionally a semi empirical–analytical method is developed for calculating the total pressure loss within a multi jet impingement system. This simple methodology can provide a quick estimate of the total pressure drop and hence is suited for first order optimization. The methodology is validated by results obtained from experiments and from CFD simulations.

A Numerical Study on the Effects of Acoustic Forcing on Fuel Spray Dynamics in Gas Turbines

2020 ◽  
Author(s):  
Nicholas C. W. Treleaven ◽  
Andrew Garmory ◽  
Gary J. Page
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Gas Turbines ◽  
Numerical Study ◽  
Mixture Fraction ◽  
Orthogonal Decomposition ◽  
Computational Domain ◽  
Fuel Injector ◽  
Design Modification ◽  
Acoustic Forcing ◽  
Proper Orthogonal

Abstract In the case of aircraft engines, the fuel is injected as a liquid spray which may play a role in thermoacoustic instabilities through creating changes to the mixture fraction inside the combustion chamber. This study uses two-phase incompressible non-reacting large eddy simulation with Lagrangian particle tracking to show how spray droplets of different sizes can be affected by large scale hydrodynamic structures and acoustic forcing. The forcing is applied at the inlets of a truncated computational domain that only includes the geometry downstream of the fuel injector using the newly developed PODFS (proper orthogonal decomposition Fourier series) method. The PODFS is a model that can reproduce the effects of acoustic forcing by extracting planes of data from an auxiliary acoustically forced compressible unsteady Reynolds averaged Navier-Stokes simulation. A proper orthogonal decomposition analysis shows that fuel droplets of a typical size seen in jet engines are more sensitive to acoustic and hydrodynamic structures than droplets with an order of magnitude larger or smaller diameter, consistent with their Stokes number. Phase and azimuthally averaged results show that fluctuations of the spray mixture fraction represented by large droplets affect the total spray mixture fraction much more than fluctuations of the small droplets. An additional intermittent spray dispersion mechanism was identified that is due to intermittent vorticity being generated between the two outer injector flow passages. An injector design modification has been suggested that will reduce the prevalence of this mechanism.

UDIMET 718

Alloy Digest ◽  
1978 ◽  
Vol 27 (11) ◽  
Keyword(s):  
Gas Turbines ◽  
Base Alloy ◽  
Heat Treating ◽  
High Yield ◽  
Nickel Base Alloy ◽  
Aged Condition ◽  
High Yield Strength ◽  
Unusual Combination ◽  
Critical Components ◽  
Nickel Base

Abstract UDIMET 718 is a nickel-base alloy that is precipitation hardenable. It exhibits exceptionally high yield strength up to 1300 F, excellent cryogenic properties down to -423 F and superior weldability even in the fully-aged condition. This unusual combination of characteristics makes it suitable for elevated-temperature applications in gas turbines and in critical components for missiles. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-258. Producer or source: Special Metals Corporation.

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