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Sans J.,Von Karman Institute for Fluid Dynamics | Brouckaert J.-F.,Von Karman Institute for Fluid Dynamics | Hiernaux S.,Techspace Aerospace
Proceedings of the ASME Turbo Expo | Year: 2015

The solidity in a compressor is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. The choice of this parameter represents a crucial step in the whole design process. Most of the studies addressing this issue are based on low-speed compressor cascade correlations. In that prospect, aiming at updating those correlation data as well as improving the physical understanding of the solidity effect on compressor performance, both experimental and numerical high-speed cascade investigations have been carried out at the von Karman Institute. The profile is a state-of-the-art controlled diffusion blade, representative of a low pressure compressor stator mid-span profile. The performance in terms of total pressure losses and deviation have been measured in the high-speed C3 cascade facility for three different solidities at six incidences and two Mach numbers. Based on the experimental results, a numerical linear cascade model has been built and computations have been run with FINE/Turbo at the same conditions as the measurements. The quality of the numerical predictions is discussed over the whole incidence range and, in particular, big discrepancies are highlighted at off-design incidences. Focusing on the solidity effects at mid-span, both experimental and numerical results are compared with existing correlations. The establishment of updated correlations for such controlled diffusion profile is addressed for both deviation and total pressure losses and at both optimum and off-design conditions. Copyright © 2015 by ASME.

Sans J.,Von Karman Institute for Fluid Dynamics | Resmini M.,Von Karman Institute for Fluid Dynamics | Brouckaert J.F.,Von Karman Institute for Fluid Dynamics | Hiernaux S.,Techspace Aerospace
Proceedings of the ASME Turbo Expo | Year: 2014

In the use of RANS models, it is well known that the selection of the turbulence model and the numerical scheme may have a critical impact not only in terms of convergence, but also on the reliability to simulate separated or secondary flows in general. The aim of the investigation, performed using the commercial software FINE/Turbo, is the understanding and the quantification of the effects of these two numerical parameters on the performance and the stability of a state-of-the-art controlled diffusion airfoil compressor cascade. A mesh sensitivity analysis has been carried out at both design and off-design conditions. The behaviour of the main flow parameters have been investigated over the whole incidence working range, considering a variation of the inlet Mach number between 0.35 and 0.65. Five different turbulence models have been tested: Baldwin-Lomax, Spalart-Allmaras, k - ε Yang-Shih, k - ε Launder-Sharma and k - ω SST. In a specific combination of incidences and Mach numbers, the impact of turbulence model settings has been assessed imposing boundary conditions according to different criteria. Two different numerical schemes have been tested: a Jameson central scheme and a second order upwind scheme. The results between the different simulations are discussed in terms of loss coefficient distribution and incidence range; considering the turbulence model comparison, the differences are significant in the whole incidence range, specially approaching the stall limit. Baldwin-Lomax and Spalart-Allmaras simulations present the same value of last stable incidence, while Yang-Shih and SST are characterized by a reduced stall margin. In many operating conditions, simulations computed with centered scheme present negative losses in a wide area of the outlet sections. This problem is reduced if an upwind scheme is used, but causes a substantial reduction of the incidence range. Copyright © 2014 by ASME.

Sans J.,Von Karman Institute for Fluid Dynamics | Resmini M.,Von Karman Institute for Fluid Dynamics | Brouckaert J.-F.,Von Karman Institute for Fluid Dynamics | Hiernaux S.,Techspace Aerospace
Proceedings of the ASME Turbo Expo | Year: 2014

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on lowspeed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-ofthe-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and com- Copyright © 2014 by ASME.

Taylor S.R.,University of Texas Health Science Center at Houston | Contu F.,University of Texas Health Science Center at Houston | Hunter C.N.,U.S. Air force | Fenzy L.,Techspace Aerospace
ECS Transactions | Year: 2010

This study examines the role of short-term changes in the coating-substrate interface as a means to predict the long-term coating performance. By introducing a through-coating defect, interfacial changes are quantified using EIS over short times of exposure to aqueous environments. The ability of these short-term measurements to predict long-term performance of coating systems was examined in two studies. In one study, 32 aerospace coating systems on AA2024-T3 substrates were exposed in a large volume cell to 0.1M (NH 4) 2SO 4 + 0.005M NaCl for 8 days. In a second study, 12 aerospace coatings systems on AA2024-T3 were exposed in a small volume cell (80 μ) to 0.5M NaCl for 4 days. Separate panels of the same coating systems were exposed to ASTM B117 salt spray for 3000 hours. A blind comparison of the EIS data to the 3000 h salt spray results showed an 80% correlation. EIS data acquired after the introduction of the defect was essential and the dominate factor in the prediction of 3000 h salt spray results. The results of this study reinforces the importance of coating-substrate interface stability in predicting field performance of inhibited coating systems, and provide a promising short-term method for the quantitative prediction of long-term coating performance for these materials. ©The Electrochemical Society.

Bettaieb M.B.,University of Liège | Lenain A.,Techspace Aerospace | Habraken A.M.,University of Liège
Fatigue and Fracture of Engineering Materials and Structures | Year: 2013

This paper presents and discusses static (elastoviscoplastic and damage) and high-cycle fatigue characterization of two microstructures of the Ti5553 alloy. The difference between these two microstructures is related to their heat treatment and precisely to the temperature of the final aging. For each microstructure, several tests were carried out to identify their static and fatigue properties and the test results were correlated to the microstructure. A fractographic analysis of the rupture sections was performed in order to investigate the fracture mechanisms of the two microstructures. Finally, the fatigue properties of the two microstructures were compared with those found in results reported in the literature for two other classical titanium alloys used for aeronautical applications. © 2012 Wiley Publishing Ltd.

Pyroalliance and Techspace Aerospace | Date: 2015-11-20

An arming and safety device for a pyrotechnic chain, the device including a housing presenting an inlet zone for a pyrotechnic stream and an outlet zone for the pyrotechnic stream, an arming element housed in the housing between the inlet and outlet zones and adapted to move between a disarmed position in which it blocks the passage of the pyrotechnic stream and an armed position in which it allows the pyrotechnic stream to pass, and an electric motor for driving the arming element. The stator of the electric motor is situated outside the housing, and the rotor is contained entirely inside the housing.

Leborgne M.,Cernium | Carton L.,Cernium | Lonfils T.,Cernium | Iliopoulou V.,Techspace Aerospace | Hiernaux S.,Techspace Aerospace
11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015 | Year: 2015

This paper focuses on the development and application of an integrated aero-mechanical design methodology for a new architecture of low-pressure compressor : the so-called Bladed druM, which enables a substantial reduction of the engine mass but at the cost of high vibrational stresses and complex dynamic behaviour. In this study, a novel two-step design approach is proposed and applied on the critical third rotor : first the creation of a purely aerodynamic database based on CFD, followed by a surrogate-assisted mechanical optimization, taking into account aerodynamic constraints by surrogate models built at the end of the first step. To this end, an integrated aero-mechanical parameterization space tackling both the rotor and drum shapes was devised. Data mining tools such as SOMs were used to identify constraint activity and their antagonism in order to refine the optimization scope and steer the optimizer efficiently. Final results of the mechanical optimization showed a potential benefit of 9% for the mass of rotor 3 while satisfying all mechanical and predicted aerodynamic constraints. A posteriori comparison between the predicted and the actual CFD aerodynamic performances for some optimized experiments demonstrated the qualitative representativeness of the surro-gates and their potential usage during the design phas.

Mesbah M.,Cernium | Thomas J.F.,Cernium | Thirifay F.,Cernium | Naert A.,Techspace Aerospace | De Vriendt O.,Techspace Aerospace
IFASD 2013 - International Forum on Aeroelasticity and Structural Dynamics | Year: 2013

This paper focuses on the numerical and experimental analysis of the forced response in turbomachinery. A new numerical methodology called TWIN approach is proposed which does not rely on the superposition principle of forces and it can handle the non-linear blade-rowinteractions. It's performance is evaluated through a low pressure compressor BluMTM excited by low engine excitations. To verify the superposition principle, a Decoupled approach is also employed. Extensive experiments are carried out to investigate the accuracy and reliability of the method. A detailed analysis of the results obtained from TWIN and Decoupled approaches is presented and the estimated forced response are compared with measurement.

Mesbah M.,Cernium | Thomas J.-F.,Cernium | Thirifay F.,Cernium | Naert A.,Techspace Aerospace | Hiernaux S.,Techspace Aerospace
Journal of Turbomachinery | Year: 2015

This study aims to numerically investigate the sensitivity of the forced response with respect to the variation of the tip clearance setting of a low pressure compressor BluM ™ (monoblock bladed drum) when it is subjected to low engine order excitations. Two different types of blades are employed in the upstream row in order to generate the low engine order excitations. The forced response as well as the aerodynamic damping is numerically estimated using the TWIN approach. The experiments are conducted to measure the forced response for the nominal tip gap to validate the numerical results. Further, simulations are performed for a range of tip clearances. The variation of the steady load distributions due to the changes of the tip clearance are analyzed and presented. The aerodynamic damping and the forced response are calculated and compared for different tip clearances. It is observed that aerodynamic damping increases significantly with tip gap, whereas the excitation forces are reduced. As consequence of these two evolutions, the forced response decreases drastically for larger tip clearance. © 2015 by ASME.

Cori J.-F.,Techspace Aerospace | Etienne S.,Ecole Polytechnique de Montréal | Garon A.,Ecole Polytechnique de Montréal | Pelletier D.,Ecole Polytechnique de Montréal
International Journal for Numerical Methods in Fluids | Year: 2015

This paper presents an approach to develop high-order, temporally accurate, finite element approximations of fluid-structure interaction (FSI) problems. The proposed numerical method uses an implicit monolithic formulation in which the same implicit Runge-Kutta (IRK) temporal integrator is used for the incompressible flow, the structural equations undergoing large displacements, and the coupling terms at the fluid-solid interface. In this context of stiff interaction problems, the fully implicit one-step approach presented is an original alternative to traditional multistep or explicit one-step finite element approaches. The numerical scheme takes advantage of an arbitrary Lagrangian-Eulerian formulation of the equations designed to satisfy the geometric conservation law and to guarantee that the high-order temporal accuracy of the IRK time integrators observed on fixed meshes is preserved on arbitrary Lagrangian-Eulerian deforming meshes. A thorough review of the literature reveals that in most previous works, high-order time accuracy (higher than second order) is seldom achieved for FSI problems. We present thorough time-step refinement studies for a rigid oscillating-airfoil on deforming meshes to confirm the time accuracy on the extracted aerodynamics reactions of IRK time integrators up to fifth order. Efficiency of the proposed approach is then tested on a stiff FSI problem of flow-induced vibrations of a flexible strip. The time-step refinement studies indicate the following: stability of the proposed approach is always observed even with large time step and spurious oscillations on the structure are avoided without added damping. While higher order IRK schemes require more memory than classical schemes (implicit Euler), they are faster for a given level of temporal accuracy in two dimensions. © 2015 John Wiley & Sons, Ltd.

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