Robust Design Optimization of a Low Pressure Turbine Rotor Discs Secondary Air System

2017 ◽  
Author(s):  
Giulia Antinori ◽  
Ilya Arsenyev ◽  
Andreas Fischersworring-Bunk
Keyword(s):  
Parameter Space ◽  
Cooling System ◽  
Optimization Methods ◽  
Low Pressure ◽  
Life Cycles ◽  
Robust Design Optimization ◽  
Design Parameters ◽  
Low Pressure Turbine ◽  
Air System ◽  
Secondary Air

Low pressure turbine (LPT) rotor discs undergo high thermal and mechanical loads during normal aircraft missions. Therefore, to meet the minimum requirement for life, temperatures and stresses in the disk need to be maintained within certain limits. This is achieved by carefully designing the disk shape and the cooling system. The complexity of this multi-physics problem together with a large number of design parameters require the use of numerical optimization methods for the Secondary Air System (SAS) design. Moreover, possible variations in the boundary conditions due to ambient parameters (e.g. temperatures, pressures) and manufacturing tolerances of the SAS components should be taken into account within the system design and optimization phase. In this paper an application of robust optimization methods for the design of a LPT secondary air system is proposed. The objective is to increase the engine efficiency by minimizing the amount of cooling flow, which is needed to guarantee a minimum required number of life cycles and to keep maximal temperatures within the limits. In order to predict the disks life accurately, transient thermal-structural analysis is used, which is computationally demanding. For this reason, optimization should be performed with a very limited amount of system evaluations. The dimension of the parameter space is reduced through the application of global sensitivity analysis methods by selecting the parameters that most affect the results. Optimization methods are sped up by the use of surrogate models, created over the reduced parameter space, which approximate the objective function and the constraints.

Secondary Air Systems in Aeroengines Employing Vortex Reducers

2001 ◽  
Author(s):  
Dimitrie Negulescu ◽  
Michael Pfitzner
Keyword(s):  
Flow Path ◽  
Supporting Evidence ◽  
Excessive Pressure ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Hot Gas ◽  
Air System ◽  
High Integrity ◽  
Secondary Air ◽  
Aero Engines

A secondary air system in modern aero engines is required to cool the compressor and turbine discs and make sure that no hot gas ingestion occurs into the cavities between the turbine discs, which could cause an inadvertent reduction of disc life. A high integrity solution for guiding the air from the compressor to the turbine is through an inner bleed from the compressor platform and through the space between the disc bores and the shaft connecting the fan with the low pressure turbine. Since strongly swirling air is taken from the compressor platforms to a much lower radius, a means of deswirling the air has to be used to avoid excessive pressure losses along the flow path. The paper describes a system utilizing tubeless vortex reducers to accomplish this deswirl, which are compared to a more conventional air system utilizing tubes. The working principles of both types of vortex reducer and guidelines for the design of a secondary air system using vortex reducers are explained with supporting evidence from rig tests and CFD calculations. Opportunities for the aerodynamic optimisation of the tubeless vortex reducer are elaborated and the experience gained using the system during the development of the BR700 engine is described.

scholarly journals Flutter Mechanisms in Low Pressure Turbine Blades

1998 ◽  
Author(s):  
M. Nowinski ◽  
J. Panovsky
Keyword(s):  
Research Effort ◽  
Turbine Blades ◽  
Low Pressure ◽  
Design Parameters ◽  
Computational Techniques ◽  
Influence Coefficient ◽  
Low Pressure Turbine ◽  
Blade Flutter ◽  
Euler Methods ◽  
Annular Cascade

The work described in this paper is part of a comprehensive research effort aimed at eliminating the occurrence of low pressure turbine blade flutter in aircraft engines. The results of fundamental unsteady aerodynamic experiments conducted in an annular cascade are studied in order to improve the overall understanding of the flutter mechanism and to identify the key flutter parameters. In addition to the standard traveling wave tests, several other unique experiments are described. The influence coefficient technique is experimentally verified for this class of blades. The beneficial stabilizing effect of mistuning is also directly demonstrated. Finally, the key design parameters for flutter in low pressure turbine blades are identified. In addition to the experimental effort, correlating analyses utilizing linearized Euler methods demonstrate that these computational techniques are adequate to predict turbine flutter.

Heavy Duty Gas Turbine Simulation: Global Performances Estimation and Secondary Air System Modifications

2006 ◽  
Author(s):  
Carlo Carcasci ◽  
Bruno Facchini ◽  
Stefano Gori ◽  
Luca Bozzi ◽  
Stefano Traverso
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Energy System ◽  
Operating Conditions ◽  
Coupled Analysis ◽  
Ambient Conditions ◽  
Air System ◽  
Secondary Air ◽  
And Performance

This paper reviews a modular-structured program ESMS (Energy System Modular Simulation) for the simulation of air-cooled gas turbines cycles, including the calculation of the secondary air system. The program has been tested for the Ansaldo Energia gas turbine V94.3A, which is one of the more advanced models in the family Vx4.3A with a rated power of 270 MW. V94.3A cooling system has been modeled with SASAC (Secondary Air System Ansaldo Code), the Ansaldo code used to predict the structure of the flow through the internal air system. The objective of the work was to investigate the tuning of the analytical program on the basis of the data from design and performance codes in use at Ansaldo Energy Gas Turbine Department. The results, both at base load over different ambient conditions and in critical off-design operating points (full-speed-no-load and minimum-load), have been compared with APC (Ansaldo Performance Code) and confirmed by field data. The coupled analysis of cycle and cooling network shows interesting evaluations for components life estimation and reliability during off-design operating conditions.

Transition Modelling for Vortex Generating Jets on Low-Pressure Turbine Profiles

2011 ◽  
Author(s):  
Florian Herbst ◽  
Dragan Kozˇulovic´ ◽  
Joerg R. Seume
Keyword(s):  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Local Transition

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is ≤ 100·103 an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modelled by a filtered Q vortex criterion the transition development itself is modelled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

Prediction of Non-Linear Mechanical Behavior With Deep Neural Network: Application on Low Pressure Turbine Disc

2020 ◽  
Author(s):  
Yuan Jin ◽  
Weichen Li ◽  
Zheyi Yang ◽  
Olivier Jung
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Displacement Field ◽  
Deep Neural Network ◽  
Low Pressure ◽  
Constitutive Law ◽  
Design Parameters ◽  
Low Pressure Turbine ◽  
Turbine Disc ◽  
Nonlinear Constitutive Law

Abstract Thanks to the increase of computational capacity and the diversification of computational means, deep learning techniques have shown great successes in learning representations from data in the past decade. Following this trend, efforts have been made in the literature to apply Deep Neural Network (DNN) as surrogate model. Common practice consists in utilizing a single DNN to predict a certain physical property given input design parameters, and the DNN is trained by corresponding simulation results. However, most of the complex high-fidelity simulations involve nonlinear physical laws, e.g. elasto-plasticity, which cannot be explicitly depicted by the applied single DNN model. In the present work, static mechanical simulation with nonlinear constitutive law is addressed with a novel approach in a deep learning framework. We approximate the displacement and the nonlinear constitutive law by two deep neural networks. The first DNN acts as a prior on the unknown displacement field, while the second network aims at describing the nonlinear strain-stress relationship. The dependence of the strainstress relationship on the strain level is taken into consideration by taking the first order derivative with respect to spatial coordinates of the first DNN as an input of the second network. A new loss model combining the error in displacement field prediction and constitutive law description is proposed to train the two DNNs together. We demonstrate the effectiveness of the proposed framework on a low pressure turbine disc design problem.

Statistical Methods for a Stochastic Analysis of the Secondary Air System of a Jet Engine Low Pressure Turbine

2013 ◽  
Author(s):  
Giulia Antinori ◽  
Yannick Muller ◽  
Fabian Duddeck ◽  
Andreas Fischersworring-Bunk
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Analysis ◽  
Stochastic Analysis ◽  
Sampling Methods ◽  
Correlation Method ◽  
Low Pressure ◽  
Jet Engine ◽  
Low Pressure Turbine ◽  
Input Variables ◽  
Secondary Air

In this paper several stochastic methods are evaluated with respect to their applicability for the analysis of fluid networks. The methods are applied for the analysis of a 1D flow model of the Secondary Air System (SAS) of a three stages low pressure turbine (LPT) of a jet engine. The stochastic analysis is comprised of a sensitivity analysis followed by an uncertainty analysis. The sensitivity analysis is performed to gain a better understanding of the SAS physics and robustness, to identify the important variables and to reduce the number of parameters involved in the simulations for the uncertainty analysis. The uncertainty analysis, using probability distributions derived from the manufacturing process, allows to determine the effect of the input uncertainties on responses such as pressures, fluid temperatures and mass flow rates. A review of the most common and relevant sampling methods is performed. A comparison of the respective computational cost and of the sample points distribution is proposed with the aim of finding the most suited method. The study shows that some of the sampling methods can not be recommended since they produce spurious correlations between independent input variables. With regards to the sensitivity analysis, many literature sources state that the Pearson correlation method is only valid for linear models when assessing the importance of input variables. As the SAS is highly non-linear, non-parametric variance based methods are introduced here to make up for the limitations of the correlation method. Following the results of the study, it is recommended to combine the sampling method with a non-parametric variance based method. Thus, the main effects as well as all the interactions among variables are captured.

Particulate Monitor for Gas Turbine Cooling Air

2008 ◽  
Author(s):  
Richard H. Bunce ◽  
Francisco Dovali-Solis ◽  
Robert W. Baxter
Keyword(s):  
Gas Turbine ◽  
Monitoring System ◽  
Cooling System ◽  
Gas Turbine Engine ◽  
Minimum Size ◽  
Turbine Engine ◽  
Air System ◽  
Air Cooler ◽  
Secondary Air ◽  
Cooling Air

It is important to monitor the quality of the air used in the cooling system of a gas turbine engine. There can be many reasons that particulates smaller than the minimum size removed by typical engine air filters can enter the secondary air system piping in a gas turbine engine system. Siemens has developed a system that provide real time monitoring of particulate concentrations by adapting a commercial electrodynamic devise for use within the confines of the gas turbine secondary air system with provision for a grab sample option to collect samples for laboratory analysis. This on-line monitoring system is functional at typical engine cooling system piping operating pressure and temperature. The system is calibrated for detection of iron oxide particles in the 1 to 100 micrometer range at concentration of from 1 to 50 parts per million mass wet (ppmmw) The electro dynamic device is nominally operable at 800°C. The particulate monitoring system requires special mounting and antenna. This system may be adjusted for other materials, sizes and concentrations. The system and its developmental application are described. The system has been tested and test results are reviewed. The test application was the cooling air piping of a Siemens gas turbine engine. Multiple locations were monitored. The cooling system in this engine incorporates an air cooler and the particulate monitoring system was tested upstream and downstream of the air cooler for temperature contrast. The monitor itself is limited to the piping system and not the engine gas-path.

Separation of Particles in the Secondary Air System of Gas Turbines

2011 ◽  
Author(s):  
Natalia Garci´a Vi´llora ◽  
Klaus Dullenkopf ◽  
Hans-Jo¨rg Bauer
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Separation Efficiency ◽  
Cooling System ◽  
Turbine Blades ◽  
Spherical Particles ◽  
Experimental Investigations ◽  
Air System ◽  
Secondary Air ◽  
Aero Engines

Particles contaminating the secondary air system of land based gas turbines or aero-engines can cause serious problems in various engine components, particularly in the cooling system. The capability of the pre-swirl system in separating particles will be described in this paper. So far, only a few publications can be found on experimental investigations on this subject. The work presented in this paper attempts to give a contribution to fill this gap and thus represents a further step towards a better understanding of the behaviour of solid contaminants in the secondary air system. Due to the strong swirl in the pre-swirl cavity, the aero-dynamical forces can be used to separate particles, thus preventing depositions inside the turbine blades or even block-age of the film cooling holes. Numerous experiments in a pre-swirl system have been performed using spherical particles and non-spherical particles. As reference cases, three types of spheres, with two size ranges and different materials, were used to understand how size and density influence the separation efficiency. For further experiments, irregularly-shaped particles, more similar to the ones found in real aero-engines, were used too. The separation efficiency was investigated at different pre-swirl nozzle pressure ratios, rotational speeds and radial mass flows. The results are presented in relation to the particle Reynolds numbers, drag coefficients, Stokes numbers and swirl ratios in the pre-swirl cavity.

scholarly journals Design Space Exploration of Turbine Blade Shroud Interlock for Flutter Stability

2020 ◽  
Author(s):  
Olatz Larrieta ◽  
Roberto Alonso ◽  
Óscar Pérez Escobar ◽  
Ibrahim Eryilmaz ◽  
Vassilios Pachidis
Keyword(s):  
Modal Analysis ◽  
Turbine Blade ◽  
High Speed ◽  
Design Space Exploration ◽  
Twist Angle ◽  
Low Pressure ◽  
Axial Position ◽  
Design Parameters ◽  
Low Pressure Turbine ◽  
Contact Position

Abstract The geared turbofan engines bring the potential to rotate the fan at lower speed and allow an increase in diameter, which in turn leads to an increase in propulsive efficiency through high by-pass ratio. The low-pressure turbine stages driving the fan can also rotate at high speed resulting in fewer stages when compared to traditional turbofans. However, when operating at high speed, pressure fluctuations due to self-excited vibrations increase and may provoke flutter instabilities. In a geared architecture, to deliver the high power required by the fan and the intermediate-pressure compressor, the low-pressure turbine system operates at higher temperatures compared to its predecessors. This phenomenon requires structural materials with higher heat resistance, which carries the inconvenience of poor welding suitability. That is the reason why alternative non-welded blade shroud joint techniques are so important, techniques as the blade interlock mechanism studied in this work. This manuscript examines the effects of different design parameters of a low-pressure turbine blade shroud interlock on flutter stability, to make future recommendations for geared engines. The shrouded turbine rotor blades feature blade interlocks, which enhances the dynamic stability by providing stiffness to the rotor blade row. To assess the stability of the system, a parametric design of a turbine blade-disk assembly was prepared. In the parametric model the design variables that define the blade interlock are the interlock angle, interlock axial position, interlock contact length and height, knife seal position and pre-twist angle. After parametrization, a finite element model of the turbine blade and disk assembly was prepared with cyclic symmetry boundary condition. The stresses caused by rotation were calculated in a static structural analysis and these were used as pre-stress boundary conditions in modal analysis. The modal results were afterwards exchanged with an aerodynamic model to obtain the aerodynamic damping for different blade interlock design configurations. In the present work, the dynamic response of the first three excitation modes was analyzed. It was found that the third mode was stable for all the design points, whereas first and second modes were unstable at least for the reference design point. Among the considered six different parameters that define the blade interlock geometry, the interlock contact position turned to be the most influential parameter for modal response and for flutter stability. Moving the interlock contact position towards the trailing edge gave the most beneficial results. On the other hand, the interlock angle showed the least influence on both, the modal analysis and flutter behavior. The accomplished Design of Experiments and subsequent optimization process also conclude that there exists an interdependency between the studied parameters.

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