Coupled Simulation of the Secondary Air Flow, Heat Transfer, and Structural Deflection of a Gas Turbine Engine

2012 ◽  
Author(s):  
Guilherme Tondello ◽  
Wolodymir Boruszewski ◽  
Fernando Mengele ◽  
Marcelo Assato ◽  
Silvio Shimizu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Model ◽  
Air Flow ◽  
Labyrinth Seal ◽  
Simulation Software ◽  
Thermal Loads ◽  
Labyrinth Seals ◽  
Secondary Air

In secondary air flow in gas turbines, labyrinth seals are used to control the flow to and from each cavity and to the rotor blades for cooling purposes. Those components and the final flow rate are very sensitive to gap clearance and displacement due to structural and thermal loads during operation, therefore designing those seals and knowing the resultant flow rates in each part of the circuit during the design phase is not an easy task, and tuning those gap values may bring significant increase in turbine efficiency. This paper describes the application of coupled commercial codes for secondary air flow and structural simulation for better evaluating temperature profiles and labyrinth seal behavior during operation. Flowmaster V7 was used for building a one dimensional model of the complete secondary air flow path including swirl effects and heat transfer phenomena, and ANSYS was used for building a structural model, taking into account both rotational and thermal loads. The labyrinth seals clearances, and thermal interactions between solid and fluid were coupled bi-directionally between the two simulation software. This simulation focused in the system, including the effects of each region, passage, seal and cavity in the calculations. The turbine model simulated was a VSE’s gas turbine under development, having a nominal rotation of 22600 rpm. This paper presents the numerical characteristics of each model, the details about the 1D fluid and 3D structural coupling, and the results obtained.

Experimental Investigation on Leakage Losses and Heat Transfer in a Non Conventional Labyrinth Seal

2011 ◽  
Author(s):  
Luca Bozzi ◽  
Enrico D’Angelo ◽  
Bruno Facchini ◽  
Mirko Micio ◽  
Riccardo Da Soghe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbine ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Secondary Air

Different labyrinth seal configurations are used in modern heavy-duty gas turbine such as see-through stepped or honeycomb seals. The characterization of leakage flow through the seals is one of the main tasks for secondary air system designers as well as the evaluation of increase in temperature due to heat transfer and windage effects. In high temperature turbomachinery applications, knowledge of the heat transfer characteristics of flow leaking through the seals is needed in order to accurately predict seal dimensions and performance as affected by thermal expansion. This paper deals with the influence of clearance on the leakage flow and heat transfer coefficient of a contactless labyrinth seal. A scaled-up planar model of the seal mounted in the inner shrouded vane of the Ansaldo AE94.3A gas turbine has been experimentally investigated. Five clearances were tested using a stationary test rig. The experiments covered a range of Reynolds numbers between 5000 and 40000 and pressure ratios between 1 and 3.3. Local heat transfer coefficients were calculated using a transient technique. It is shown that the clearance/pitch ratio has a significant effect upon both leakage loss and heat transfer coefficient. Hodkinson’s and Vermes’ models are used to fit experimental mass flow rate and pressure drop data. This approach shows a good agreement with experimental data.

Effect of Air-Curtains on Labyrinth Seal Performance

2016 ◽  
Author(s):  
Aakash C. Rai ◽  
Deoras Prabhudharwadkar ◽  
Sunil Murthy ◽  
Andrew Giametta ◽  
David Johns
Keyword(s):  
Gas Turbines ◽  
Cross Flow ◽  
Labyrinth Seal ◽  
Labyrinth Seals ◽  
Air Curtain ◽  
Baseline Design ◽  
Leakage Flows ◽  
Seal Design ◽  
Parametric Studies ◽  
Secondary Air

Labyrinth seals are used in many key sealing locations in gas turbines to control various leakage flows, e.g., to control the secondary air-flow from the compressor (bypassing the combustor), the turbine inter-stage leakages and blade tip leakages. This study was performed to assess the improvement in the performance of a labyrinth seal by using an air-curtain (cross-flow jet(s)) from the stator. Detailed parametric studies were performed to study the effect of the air-curtain jet pressure, location, and the number of jets on the seal performance with respect to the leakage flow. The analysis was done using 2-dimensional axisymmetric CFD simulations. It was found that in the case of a labyrinth seal with a flat stator (without a honeycomb attached to the stator) the air-curtain design can reduce the seal leakage by about 30% over the baseline seal design without air-curtains. This reduction happened because the air-curtain jet deflected the main seal jet away from the seal clearance. A similar conclusion was also obtained in case of a labyrinth seal with a honeycombed stator. Furthermore, our parametric studies with different air-curtain designs parameters implemented over a honeycombed labyrinth seal showed that the air-curtain jet pressure, location, and the number of jets were crucial factors governing the seal leakage. Amongst the air-curtain designs studied, it was found that implementing three air-curtains in the 1st pocket gave the maximum leakage reduction (by about 50%) over the baseline design.

Experimental and Numerical Investigation on Leakage Characteristic of Stepped Labyrinth Seal

2016 ◽  
Author(s):  
Li Zhang ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Fei Tong
Keyword(s):  
Gas Turbines ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Scaling Effects ◽  
Labyrinth Seals ◽  
Maximal Deviation ◽  
Tooth Number ◽  
Leakage Coefficient ◽  
Secondary Air ◽  
Aero Engines

Labyrinth seals represent an important flow element in the secondary air system of aero engines. The influence of seal clearance and teeth parameters on the leakage characteristic of a real size stepped labyrinth seal was experimentally and numerically analyzed in a stationary state. Two kinds of labyrinth seals were studied in this investigation that are generally used in gas turbines, namely downward stepped labyrinth and upward stepped labyrinth. The differences of seal flow leakage mechanisms between the two types of the labyrinth were investigated. In order to eliminate the scaling effects on leakage losses in labyrinth seals, the experimental labyrinth seal model took the size of the real one in an aero engine. The experiments covered a range of pressure ratio from 1.1 to 3.5. The experimental and numerical results show that in the range of the studied parameters the main teeth parameters affecting leakage coefficient are seal clearance, tooth tip thickness, tooth number and tooth front inclination. The influence of tooth height, pith and rear inclination angle on leakage coefficient of downward stepped labyrinth seal can almost be neglected in this research. And when the step height is more than twice the width of seal clearance, its effect on seal performance can be ignored. An empirical formula express of leakage coefficient with pressure ratio, seal clearance and teeth parameters of downward stepped labyrinth seal was organized which fits the experimental data with a maximal deviation of 8%. With similar pressure ratios and seal clearances, the downward stepped labyrinth seal displays lower leakage rates and provides the best sealing efficiency.

Development of Numerical Tools for Stator-Rotor Cavities Calculation in Heavy-Duty Gas Turbines

2008 ◽  
Author(s):  
C. Bianchini ◽  
R. Da Soghe ◽  
B. Facchini ◽  
L. Innocenti ◽  
M. Micio ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Inlet Temperature ◽  
Heavy Duty ◽  
One Dimensional ◽  
Air System ◽  
Numerical Tools ◽  
Secondary Air ◽  
The One

In high performance heavy-duty engines, turbine inlet temperature is considerably higher than the melting point of the metals used for turbine components e.g. nozzle guide vanes, turbine rotor blades, platforms and discs, etc. Cooling of those components is therefore essential and is achieved by diverting a few percent of the compressed air from extraction points in the compressor and passing it to the turbine through stationary ducts and over rotating shafts and discs. All those elements form the so-called secondary air system of the gas turbine, whose correct design is hence fundamental for safety, reliability and performance of the engine. Secondary air system analysis is generally performed using one dimensional calculation procedures, based correlations both for pressure losses and heat transfer coefficient evaluations. Such calculation approach, usually used in industry, takes advantages in terms of reduced computational resources. Besides, for those elements of air systems where multidimensional flow effects are not negligible and the flow field structure is highly complex, the one-dimensional–correlative modeling needs to be supported by CFD investigations. Among these elements, rotating cavities need a careful modeling in order to correctly estimate discs temperature and the minimum amount of purge air to prevent hot gas ingestion. Ansaldo Energia is facing the investigation of secondary air system of Vx4.3A gas turbine models also by using numerical tools developed by Dipartimento di Energetica “Sergio Stecco” of University of Florence. They include both a one-dimensional cavity solver and a 3D unstructured finite volume code of compressible Navier-Stokes Equation based on open source C++ Open-Foam libraries for continuum mechanics. The first numerical tool has been widely employed in simplified analysis of stator-rotor cavities and is undergoing to be integrated into a in-house lumped-parameters fluid network solver simulating the entire secondary air system. This paper is aimed at discussing some interesting results from numerical tests performed with the above discussed programs on stator-rotor cavities of a V94.3A2 gas turbine. Such numerical analysis was addressed both for better understanding the flow phenomena in the wheel space regions and for testing and verifying the experimental correlations and the calculation procedure implemented in the one-dimensional program. A detailed comparative analysis between the two different codes will be shown, both in adiabatic and heat transfer conditions.

scholarly journals Comprehensive Thermodynamic Analysis of the Humphrey Cycle for Gas Turbines with Pressure Gain Combustion

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3521 ◽  
Author(s):  
Panagiotis Stathopoulos
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Combustion Process ◽  
Ideal Gas ◽  
Point Of View ◽  
Pressure Gain Combustion ◽  
Combustion Technology ◽  
Secondary Air ◽  
And Performance ◽  
The Impact

Conventional gas turbines are approaching their efficiency limits and performance gains are becoming increasingly difficult to achieve. Pressure Gain Combustion (PGC) has emerged as a very promising technology in this respect, due to the higher thermal efficiency of the respective ideal gas turbine thermodynamic cycles. Up to date, only very simplified models of open cycle gas turbines with pressure gain combustion have been considered. However, the integration of a fundamentally different combustion technology will be inherently connected with additional losses. Entropy generation in the combustion process, combustor inlet pressure loss (a central issue for pressure gain combustors), and the impact of PGC on the secondary air system (especially blade cooling) are all very important parameters that have been neglected. The current work uses the Humphrey cycle in an attempt to address all these issues in order to provide gas turbine component designers with benchmark efficiency values for individual components of gas turbines with PGC. The analysis concludes with some recommendations for the best strategy to integrate turbine expanders with PGC combustors. This is done from a purely thermodynamic point of view, again with the goal to deliver design benchmark values for a more realistic interpretation of the cycle.

Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade

2017 ◽  
Author(s):  
E. Findeisen ◽  
B. Woerz ◽  
M. Wieler ◽  
P. Jeschke ◽  
M. Rabs
Keyword(s):  
Heat Transfer ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Cooling System ◽  
Fe Model ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Temperature Distributions

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements. Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated. Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.

A Modular Code for Real Time Dynamic Simulation of Gas Turbines in Simulink

2002 ◽  
Vol 128 (3) ◽  
pp. 506-517 ◽  
Author(s):  
S. M. Camporeale ◽  
B. Fortunato ◽  
M. Mastrovito
Keyword(s):  
Mathematical Model ◽  
Real Time ◽  
Gas Turbine ◽  
Dynamic Behavior ◽  
Gas Turbines ◽  
Simulation Software ◽  
Computational Time ◽  
High Fidelity ◽  
Time Step ◽  
The Mathematical Model

A high-fidelity real-time simulation code based on a lumped, nonlinear representation of gas turbine components is presented. The code is a general-purpose simulation software environment useful for setting up and testing control equipments. The mathematical model and the numerical procedure are specially developed in order to efficiently solve the set of algebraic and ordinary differential equations that describe the dynamic behavior of gas turbine engines. For high-fidelity purposes, the mathematical model takes into account the actual composition of the working gases and the variation of the specific heats with the temperature, including a stage-by-stage model of the air-cooled expansion. The paper presents the model and the adopted solver procedure. The code, developed in Matlab-Simulink using an object-oriented approach, is flexible and can be easily adapted to any kind of plant configuration. Simulation tests of the transients after load rejection have been carried out for a single-shaft heavy-duty gas turbine and a double-shaft aero-derivative industrial engine. Time plots of the main variables that describe the gas turbine dynamic behavior are shown and the results regarding the computational time per time step are discussed.

An Integrated Approach to Simulate Gas Turbine Secondary Air System

2020 ◽  
Author(s):  
Ali Izadi ◽  
Seyed Hossein Madani ◽  
Seyed Vahid Hosseini ◽  
Mahmoud Chizari
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Great Influence ◽  
Integrated Approach ◽  
Cfd Modeling ◽  
Connectivity Matrix ◽  
Analysis Tool ◽  
Air System ◽  
Secondary Air

Abstract One of the most critical parts of a modern gas turbine that its reliability and performance has a great influence on cycle efficiency is the secondary air system (SAS). Modern systems functions to supply not only cooling air flow for turbine blades and vanes but sealing flow for bearing chambers and turbine segments as well as turbine disks’ purge flow in order to eliminate hot gas ingestion. Due to the various interactions between SAS and main gas, consideration of the former is substantially crucial in design and analysis of the whole engine. Geometrical complexities and centrifugal effects of rotating blades and disks, however, make the flow field and heat transfer of the problem so complicated AND too computationally costly to be simulated utilizing full 3-D CFD methods. Therefore, developing 1-D and 0-D tools applying network methods are of great interests. The present article describes a modular SAS analysis tool that is consisted of a network of elements and nodes. Each flow branch of a whole engine SAS network is substituted with an element and then, various branches (elements) intersect with each other just at their end nodes. These elements which might include some typical components such as labyrinth seals, orifices, stationary/rotating pipes, pre-swirls, and rim-seals, are generally articulated with characteristic curves that are extracted from high fidelity CFD modeling using commercial software such as Flowmaster or ANSYS-CFX. Having these curves, an algorithm is developed to calculate flow parameters at nodes with the aid of iterative methods. The procedure is based on three main innovative ideas. The first one is related to the network construction by defining a connectivity matrix which could be applied to any arbitrary network such as hydraulic or lubrication networks. In the second one, off-design SAS calculation will be proposed by introducing some SAS elements that their characteristic non-dimensional curves are influenced by their inlet total pressure. The last novelty is the integration of the blades coolant calculation process that incorporates external heat transfer calculation, structural conduction and coolant side modeling with SAS network simulation. Finally, SAS simulation of an industrial gas turbine is presented to illustrate capabilities of the presented tool in design point and off-design conditions.

Thermal Influences in Gas Turbine Transients: Effects of Changes in Compressor Characteristics

1979 ◽  
Author(s):  
N. R. L. Maccallum
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Transient Response ◽  
Gas Turbines ◽  
Axial Flow ◽  
Transient Heat Transfer ◽  
Shaft Speed ◽  
Delivery Pressure ◽  
Surge Line ◽  
Transfer Parameters

During transients of axial-flow gas turbines, the characteristics of the compressor are altered. The changes in these characteristics (excluding surge line changes) have been related to transient heat transfer parameters, and these relations have been incorporated in a program for predicting the transient response of a single-shaft aero gas turbine. The effect of the change in compressor characteristics has been examined in accelerations using two alternative acceleration fuel schedules. When the fuel is scheduled on compressor delivery pressure alone. there is no increase in predicted acceleration times. When the fuel is scheduled on shaft speed alone, the predicted acceleration times are increased by about 5 to 6 percent.

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