Application of a High Order LES Approach to the Redistribution of Inlet Temperature Distortion in a Turbine

2013 ◽  
Author(s):  
Debasish Biswas ◽  
Aya Kitoh
Keyword(s):  
Gas Turbines ◽  
Fluid Dynamic ◽  
Measurement Techniques ◽  
High Order ◽  
Numerical Results ◽  
Cycle Performance ◽  
Inlet Temperature ◽  
Clear Understanding ◽  
Turbine Stage ◽  
Mean Flow

The demand of an increase in the cycle performance of today’s gas turbines creates severe heat loads in the first turbine stage, since higher operating temperatures are required. The mean flow temperature is usually well above the limit supported by the surrounding material. Cooling of both end-walls and the blades of the first stage is thus usually necessary. Consequently, mid-span streaks of hot gas pass through the first stator row and become hot jets of fluid. Also, the exit flow from a gas turbine combustor entering a turbine stage can have a wide variation in temperature. These variations may be both spatial and temporal. The implementation of cooling method requires a clear understanding of the aerodynamics involved. Both qualitative and quantitative assessments of the redistribution of inlet temperature distortions can be used to considerable advantage by the turbine designer. Experimentally it has been demonstrated that the rotor actually separates the hotter and cooler streams of fluid so that a hotter fluid migrates toward the pressure surface and cooler fluid migrates towards the suction surface. The main purpose of this study is to test the performance of a high-order LES model in terms of predicting this type of highly complicated unsteady flow and heat transfer phenomena. This work describes the performance of a high-order Large Eddy Simulation (LES) turbulent model (developed by the first author) related to the prediction of above mentioned redistribution of inlet temperature distortion in an experimental turbine. Because the understanding of the physical phenomena associated with this temperature redistribution behavior is a very challenging computational fluid dynamic problem. If the numerical method could predict the precisely measured data satisfactorily, then the fluid dynamic variables which are difficult to measure (but obtained as computed results) could be used to visualize the flow characteristics. This technique will also help to get rid off indirect measurement techniques with large measurement uncertainty. In our study emphasis is put to predict the unsteady turbulence characteristics. In this work 3-D unsteady Navier-Stokes analysis of a turbine stage (satisfying the experimental stator-rotor blade ratio) is carried out to study the above mentioned phenomena. The numerical results predicted the experimentally observed phenomena very well. The fact that the streamlines in the stator row remain unaffected was demonstrated by the numerical results. The measured characteristics of the streamline patterns in the rotor row resulted from the secondary flow effect and consequently the inlet temperature distortion effect is also very well predicted.

Numerical investigation of non-uniform flow in twin-silo combustors and impact on axial turbine stage performance

2021 ◽  
pp. 095765092199394
Author(s):  
Hafiz M Hassan ◽  
Adeel Javed ◽  
Asif H Khoja ◽  
Majid Ali ◽  
Muhammad B Sajid
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Flow ◽  
Large Temperature ◽  
Clear Understanding ◽  
Gas Temperature ◽  
Turbine Stage ◽  
Flow Angle ◽  
Axial Turbine ◽  
Stage Performance

A clear understanding of the flow characteristics in the older generation of industrial gas turbines operating with silo combustors is important for potential upgrades. Non-uniformities in the form of circumferential and radial variations in internal flow properties can have a significant impact on the gas turbine stage performance and durability. This paper presents a comprehensive study of the underlying internal flow features involved in the advent of non-uniformities from twin-silo combustors and their propagation through a single axial turbine stage of the Siemens v94.2 industrial gas turbine. Results indicate the formation of strong vortical structures alongside large temperature, pressure, velocity, and flow angle deviations that are mostly located in the top and bottom sections of the turbine stage caused by the excessive flow turning in the upstream tandem silo combustors. A favorable validation of the simulated exhaust gas temperature (EGT) profile is also achieved via comparison with the measured data. A drop in isentropic efficiency and power output equivalent to 2.28% points and 2.1 MW, respectively is observed at baseload compared to an ideal straight hot gas path reference case. Furthermore, the analysis of internal flow topography identifies the underperforming turbine blading due to the upstream non-uniformities. The findings not only have implications for the turbine aerothermodynamic design, but also the combustor layout from a repowering perspective.

Proof-Of-Concept of a Thermal Barrier Coated Titanium Cooling Layer for an Inside-Out Ceramic Turbine

2021 ◽  
Author(s):  
Antoine Gauvin-Verville ◽  
Patrick K. Dubois ◽  
Benoit Picard ◽  
Alexandre Landry-Blais ◽  
Jean-Sébastien Plante ◽  
...  
Keyword(s):  
Polymer Composite ◽  
Safety Factor ◽  
Gas Turbines ◽  
High Efficiency ◽  
Cooling Power ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Minimum Safety Factor ◽  
Inside Out

Abstract Increasing turbine inlet temperature (TIT) of recuperated gas turbines would lead to simultaneously high efficiency and power density, making them prime candidates for low-emission aeronautics applications, such as hybrid-electric aircraft. The Inside-out Ceramic Turbine (ICT) architecture achieves high TIT by using compression-loaded monolithic ceramics. To resist inertial forces due to blade tip speed exceeding 450 m/s, the shroud of the ICT is made of carbon-polymer composite, wound around a metallic cooling ring. This paper demonstrates that it is beneficial to use a titanium alloy cooling ring with a thermal barrier coating (TBC), rather than nickel superalloys, for the interstitial cooling ring protecting the carbon-polymer from the hot combustion gases. A numerical Design of Experiments (DOE) analysis shows the design trade-offs between the minimum safety factor and the required cooling power for multiple geometries. An optimized high-pressure first turbine stage of a 500 kW microturbine concept using ceramic blades and a titanium cooling ring in an ICT configuration is presented. Its structural performance (minimum safety factor of 1.4) as well as its cooling losses (2% of turbine stage power) are evaluated. Finally, a 20 kW-scale prototype is tested at 300 m/s and a TIT of 1375 K during 4hrs to demonstrate the viability of the concept. Experiments show that the polymer composite was kept below its maximum safe operating temperature and components show no early signs of degradation.

Flashback in a Swirl Burner With Cylindrical Premixing Zone

2001 ◽  
Author(s):  
Jassin Fritz ◽  
Martin Kröner ◽  
Thomas Sattelmayer
Keyword(s):  
Flame Propagation ◽  
Gas Turbines ◽  
High Speed ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Measurement Techniques ◽  
Mean Flow

Flame flashback from the combustion chamber into the mixing zone is one of the inherent problems of lean premixed combustion and essentially determines the reliability of low NOx burners. Generally, flashback can be initiated by one of the following four phenomena: flashback due to the conditions in the boundary layer, flashback due to turbulent flame propagation in the core flow, flashback induced by combustion instabilities and flashback caused by combustion induced vortex breakdown. In this study, flashback in a swirling tubular flow was investigated. In order to draw maximum benefit from the tests with respect to the application in gas turbines, the radial distribution of the axial and circumferential momentum in the tube was selected such that the typical character of a flow in mixing zones of premix burners without centerbody was obtained. A single burner test rig has been designed to provoke flashback with the preheating temperature, the equivalence ratio and the mean flow rate being the influencing parameters. The flame position within the mixing section is detected by a special optical flame sensor array, which allows the control of the experiment and furthermore the triggering of the measurement techniques. The burning velocity of the fuel has been varied by using natural gas or hydrogen. The characteristics of the flashback, the unsteady swirling flow during the flame propagation, the flame dynamics and the reaction zones have been investigated by applying High Speed Video recordings, the Laser Doppler Anemometry and the Laser Induced Fluorescence. The presented results show that a combustion induced vortex breakdown is the dominating mechansim of the observed flashback. This mechanism is very sensitive to the momentum distribution in the vortex core. By adding axial momentum around the mixing tube axis, the circumferential velocity gradient is reduced and flashback can be prevented.

Evaluation of Design Performance of the Semi-Closed Oxy-Fuel Combustion Combined Cycle

2012 ◽  
Author(s):  
H. J. Yang ◽  
D. W. Kang ◽  
J. H. Ahn ◽  
T. S. Kim
Keyword(s):  
Co2 Capture ◽  
Gas Turbines ◽  
Fuel Combustion ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Separation Unit ◽  
Turbine Inlet

This study aims to present various design aspects and realizable performance of the natural gas fired semi-closed oxy-fuel combustion combined cycle (SCOC-CC). Design parameters of the cycle are set up on the basis of component technologies of today’s state-of-the-art gas turbines with a turbine inlet temperature between 1400°C and 1600°C. The most important part in the cycle analysis is the turbine cooling which affects the cycle performance considerably. A thermodynamic cooling model is introduced to predict the reasonable amount of turbine coolant to maintain the turbine blade temperature of the SCOC-CC at the levels of those of conventional gas turbines. Optimal pressure ratio ranges of the SCOC-CC for two different turbine inlet temperature levels are searched. The performance penalty due to the CO2 capture is examined. Also investigated are the influences of the purity of oxygen provided by the air separation unit on the cycle performance. A comparison with the conventional combined cycle adopting a post-combustion CO2 capture is carried out taking into account the relationship between performance and CO2 capture rate.

Velocity and Droplet Diameter Distributions of Reacting N-Heptane Sprays at Varied Boundary Conditions in a Generic Gas Turbine Combustor

2010 ◽  
Author(s):  
Michael Hage ◽  
Jan Bru¨bach ◽  
Andreas Dreizler
Keyword(s):  
Boundary Conditions ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Laser Diagnostics ◽  
Droplet Diameter ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Inlet Temperature ◽  
Diameter Distributions

In addition to a previous isothermal study, the present work reports on reacting swirling flow fields and droplet diameter distributions. The employed combustion chamber enabled optical access from three sides allowing the application of laser based measurement techniques. It is equipped with an airblast atomizer nozzle typical for gas turbines. The parameters of the boundary conditions were varied to such an extent that laser diagnostics were feasible. The chamber pressure and the inlet temperature were 2–3 bar and 300–350°C, respectively. The analysis of the spray droplets were performed by two velocity component phase Doppler anemometry (PDA). The measurements allowed for the investigation of axial and radial droplet velocities, Sauter mean diameter (SMD) distributions and an estimation of the volume flow rates. Comparisons of the different operating conditions and the influence of the parameters are given in the discussion.

Gas Properties as a Limit to Gas Turbine Performance

2002 ◽  
Author(s):  
R. C. Wilcock ◽  
J. B. Young ◽  
J. H. Horlock
Keyword(s):  
Gas Turbines ◽  
Industrial Development ◽  
Pressure Ratio ◽  
Cycle Performance ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency ◽  
Gas Properties

Although increasing the turbine inlet temperature has traditionally proved the surest way to increase cycle efficiency, recent work suggests that the performance of future gas turbines may be limited by increased cooling flows and losses. Another limiting scenario concerns the effect on cycle performance of real gas properties at high temperatures. Cycle calculations of uncooled gas turbines show that when gas properties are modelled accurately, the variation of cycle efficiency with turbine inlet temperature at constant pressure ratio exhibits a maximum at temperatures well below the stoichiometric limit. Furthermore, the temperature at the maximum decreases with increasing compressor and turbine polytropic efficiency. This behaviour is examined in the context of a two-component model of the working fluid. The dominant influences come from the change of composition of the combustion products with varying air/fuel ratio (particularly the contribution from the water vapour) together with the temperature variation of the specific heat capacity of air. There are implications for future industrial development programmes, particularly in the context of advanced mixed gas-steam cycles.

Numerical Analysis of a Gas Turbine Using Bio-Ethanol

2012 ◽  
Author(s):  
J. Arturo Alfaro-Ayala ◽  
Armando Gallegos-Muñoz ◽  
Alejandro Zaleta-Aguilar ◽  
Victor Hugo Rangel Hernandez ◽  
Alfonso Campos-Amezcua
Keyword(s):  
Numerical Analysis ◽  
Natural Gas ◽  
Thermal Behavior ◽  
Gas Turbine ◽  
Flow Rate ◽  
Gas Turbines ◽  
Fluid Dynamic ◽  
Inlet Temperature ◽  
Gas Turbine Combustor ◽  
Turbine Inlet Temperature

The change of the fuel to a bio-fuel in a gas turbine combustor is a defiant challenge due to there is not enough information about the thermal behavior into the combustor, even there is not information about the change of conventional fuel used. In these sense, a numerical analysis using Natural Gas, Diesel and Bio-Ethanol is presented. The results show a significant reduction of the Turbine Inlet Temperature (TIT) when the diesel and bio-ethanol are used in the gas turbine combustor (TITNatural Gas = 1,262.24 K, TITDiesel = 1,204.67 K and TITBio-ethanol = 918.24 K). This leads to an increment of the diesel and bio-fuel mass flow rate in order to reach the allowable condition of the gas turbine combustor. As it is well known, the reduction of the TIT means a reduction of the output power of the gas turbine, thus to avoid this, the increase of bio-ethanol was about 255.5% and diesel was about 112.2% (considering 3.6 kg/s of fuel as the full load). This paper gives an attempt to discover the viability to use bio-fuels in gas turbines from the thermal-fluid dynamic standpoint.

Flashback in a Swirl Burner With Cylindrical Premixing Zone

2004 ◽  
Vol 126 (2) ◽  
pp. 276-283 ◽  
Author(s):  
J. Fritz ◽  
M. Kro¨ner ◽  
T. Sattelmayer
Keyword(s):  
Flame Propagation ◽  
Gas Turbines ◽  
High Speed ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Burning Velocity ◽  
Turbulent Flame ◽  
Measurement Techniques ◽  
Mean Flow

Flame flashback from the combustion chamber into the mixing zone is one of the inherent problems of lean premixed combustion and essentially determines the reliability of low NOx burners. Generally, flashback can be initiated by one of the following four phenomena: flashback due to the conditions in the boundary layer, flashback due to turbulent flame propagation in the core flow, flashback induced by combustion instabilities and flashback caused by combustion induced vortex breakdown. In this study, flashback in a swirling tubular flow was investigated. In order to draw maximum benefit from the tests with respect to the application in gas turbines, the radial distribution of the axial and circumferential momentum in the tube was selected such that the typical character of a flow in mixing zones of premix burners without centerbody was obtained. A single burner test rig has been designed to provoke flashback with the preheating temperature, the equivalence ratio and the mean flow rate being the influencing parameters. The flame position within the mixing section is detected by a special optical flame sensor array, which allows the control of the experiment and furthermore the triggering of the measurement techniques. The burning velocity of the fuel has been varied by using natural gas or hydrogen. The characteristics of the flashback, the unsteady swirling flow during the flame propagation, the flame dynamics and the reaction zones have been investigated by applying high-speed video recordings, the laser Doppler anemometry and the laser induced fluorescence. The presented results show that a combustion induced vortex breakdown is the dominating mechanism of the observed flashback. This mechanism is very sensitive to the momentum distribution in the vortex core. By adding axial momentum around the mixing tube axis, the circumferential velocity gradient is reduced and flashback can be prevented.

Flow Fields and Droplet Diameter Distributions of Water and N-Heptane Sprays at Varied Boundary Conditions in a Generic Gas Turbine Combustor

2007 ◽  
Author(s):  
Michael Hage ◽  
Andreas Dreizler ◽  
Johannes Janicka
Keyword(s):  
Time Series ◽  
Boundary Conditions ◽  
Gas Turbines ◽  
Droplet Diameter ◽  
Turbulent Flame ◽  
Measurement Techniques ◽  
Flow Fields ◽  
Chamber Pressure ◽  
Inlet Temperature ◽  
Diameter Distributions

The present study reports on non-reacting swirling flow fields and droplet diameter distributions of sprays at elevated pressures and reduced inlet air temperatures. The combustion chamber used in this study enabled optical access from three sides allowing the application of various laser based measurement techniques. It is equipped with an airblast atomizer nozzle typical for many gas turbines. The parameters of the boundary conditions, based on a reacting case for a partially premixed turbulent flame, were varied to such an extent that laser diagnostics were feasible. The effects of variation in chamber pressure (2–3 bar) and inlet temperature (250–350°C) are discussed. In order to investigate the influence of the atomized liquids, and thereby surface tensions, water sprays were analysed additionally for comparison to n-heptane. For single-phase isothermal air flows, mean velocities and RMS-values were measured using laser Doppler anemometry (LDA). The aim was solely to test the performance of the turbulence model in a subsequent numerical simulation and to allow for a characterization of the flow field in absence of the spray. In addition to the statistically independent LDA measurements, time series were recorded with the intention to gain structural information on the flow patterns. The autocorrelations derived from the time series revealed a periodic coherent structure within the flow pattern indicating the presence of a precessing vortex core (PVC) typical for swirl stabilized flows.

Proof-Of-Concept of a Thermal Barrier Coated Titanium Cooling Layer for an Inside-Out Ceramic Turbine

2021 ◽  
Author(s):  
Antoine Gauvin-Verville ◽  
Patrick K. Dubois ◽  
Benoit Picard ◽  
Alexandre Landry-Blais ◽  
Jean-Sébastien Plante ◽  
...  
Keyword(s):  
Polymer Composite ◽  
Safety Factor ◽  
Gas Turbines ◽  
High Efficiency ◽  
Cooling Power ◽  
Thermal Barrier ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Minimum Safety Factor ◽  
Inside Out

Abstract Increasing turbine inlet temperature (TIT) of recuperated gas turbines would lead to simultaneously high efficiency and power density, making them prime candidates for low-emission aeronautics applications, such as hybrid-electric aircraft. The Inside-out Ceramic Turbine (ICT) architecture achieves high TIT by using compression-loaded monolithic ceramics. To resist inertial forces due to blade tip speed exceeding 450 m/s, the shroud of the ICT is made of carbon-polymer composite, wound around a metallic cooling ring. This paper demonstrates that it is beneficial to use a titanium alloy cooling ring with a thermal barrier coating (TBC), rather than nickel superalloys, for the interstitial cooling ring protecting the carbon-polymer from the hot combustion gases. A numerical Design of Experiments (DOE) analysis shows the design trade-offs between the minimum safety factor and the required cooling power for multiple geometries. An optimized high-pressure first turbine stage of a 500 kW microturbine concept using ceramic blades and a titanium cooling ring in an ICT configuration is presented. Its structural performance (minimum safety factor of 1.4) as well as its cooling losses (2% of turbine stage power) are evaluated. Finally, a 20 kW-scale prototype is tested at 300 m/s and a TIT of 1375 K during 4hrs to demonstrate the viability of the concept. Experiments show that the polymer composite was kept below its maximum safe operating temperature and components show no early signs of degradation.

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