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Ghenaiet A.,Laboratory of Thermal Power Systems
AIP Conference Proceedings | Year: 2010

The erosion resulting from sand ingestion into an axial turbomachinery is predicted using a Lagrangian particle tracking model. This simulation takes into account the effects of turbulence and endwalls vorticities on particles, random size distribution and rebound of particles. The governing equations of particle motion through stationary and rotating parts are solved in a stepwise manner separately from the flow field. Particles tracking and impacts are predicted in different cells of the computational domain based on the finite element method. A semi-empirical erosion correlation is used to predict erosion areas based on impacts condition. The simulations results obtained for different positions of the rotor blade revealed that the main impacted areas are found over the blade leading edge corner and an area of the pressure side extending towards and over the tip, in addition to a strip along the leading edge of the suction side. © 2010 American Institute of Physics. Source

Ghenaiet A.,Laboratory of Thermal Power Systems
Proceedings of the ASME Turbo Expo | Year: 2012

Modern gas turbines operate in severe dusty environments, and because of such harsh operating conditions, their blades experience significant degradation in service. This paper presents a numerical study of particle dynamics and erosion in an hp axial turbine stage. The flow field is solved separately from the solid phase and constitutes the necessary data in the particle trajectories simulations using a Lagrangian tracking model based on the finite element method. Several parameters consider a statistical description such as particle size, shape and rebound, in addition to the turbulence effect. A semi empirical erosion correlation is used to estimate erosion contours and blades deteriorations, knowing the locations and conditions of impacts. The trajectory and erosion results show high erosion rates over the pressure side of NGV near trailing edge, in addition to extreme erosion observed toward the root corner, due to high number of particles impacting with high velocities. On the suction side, erosion is mainly over a narrow strip from leading edge. Erosion in the rotor blade is shown along the leading edge and spreading over the fore of the blade suction side, owing to a flux of particles entering at high velocities and incidence. On the pressure side, regions of dense erosion are observed near the leading edge and trailing edge as well as the tip corner. Critical erosion spots seen over NGV and rotor blade are signs of a premature failure. Copyright © 2012 by ASME. Source

Cerdoun M.,Laboratory of Thermal Power Systems | Ghenaiet A.,University of Science and Technology Houari Boumediene
Institution of Mechanical Engineers - 8th International Conference on Compressors and Their Systems | Year: 2013

The operating characteristics of a turbo-compressor are tightly depending on the steady and unsteady operating characteristics of its powering turbine. The present study is aimed to highlight the flow structures through the twin-entry volute and the rotor of a radial turbine. The influence of tongue wake is depicted by a low momentum toward the rotor entry, but the effect of this critical region does not extend beyond a tangential angle of 90 deg. The unsteady simulations at different operating conditions and the FFT analyses of the pressure fluctuations due components interactions have revealed a space-time periodic behaviour that may be described by the double Fourier decomposition. The time mode analysis has permitted to determine the different frequencies and the prevailing modes. Different results were obtained based on the type of computational domains; accordingly the one-blade simulation did not reveal all the flow features as was the case of full-rotor simulation. © The author(s) and/or their employer(s), 2013. Source

Ghenaiet A.,Laboratory of Thermal Power Systems
Proceedings of the ASME Turbo Expo | Year: 2010

This paper presents an evolutionary approach as the optimization framework to design for the optimal performance of a high-bypass unmixed turbofan to match with the power requirements of a commercial aircraft. The parametric analysis had the objective to highlight the effects of the principal design parameters on the propulsive performance in terms of specific fuel consumption and specific thrust. The design optimization procedure based on the genetic algorithm PIKAIA coupled to the developed engine performance analyzer (on-design and off-design) aimed at finding the propulsion cycle parameters minimizing the specific fuel consumption, while meeting the required thrusts in cruise and takeoff and the restrictions of temperatures limits, engine size and weight as well as pollutants emissions. This methodology does not use engine components' maps and operates on simplifying assumptions which are satisfying the conceptual or early design stages. The predefined requirements and design constraints have resulted in an engine with high mass flow rate, bypass ratio and overall pressure ratio and a moderate turbine inlet temperature. In general, the optimized engine is fairly comparable with available engines of equivalent power range. Copyright © 2010 by ASME. Source

Ghenaiet A.,Laboratory of Thermal Power Systems
Journal of Turbomachinery | Year: 2012

Turbocompressors manipulating particle-laden airflows suffer from severe erosion damages which affect their operating performance and lifetime. This paper presents the results of a numerical investigation of the dynamics of sand particles and the subsequent erosion in a centrifugal compressor. The particle trajectories simulations used a developed code based on a stochastic Lagrangian model, which solves the equations of motion separately from the airflow, whereas the tracking of particles in different computational cells used the finite element method. The number of particles, sizes, and initial positions were specified, conformed to a sand particle size distribution AC_coarse (0-200 μm), and a given concentration profile. The obtained results show that the speed of rotation and particle size strongly affect the trajectories of particles and their locations of impact. Erosion is spreading over the pressure side of the main blade. Regions of high erosion rates are seen over the leading edge, at the inducer top corner and along the blade tip. Over the splitter pressure side erosion wear is much less than the main blade. The suction sides are almost without erosion except near the leading edge, and the casing is mainly affected over the inducer and tips of the blades. © 2012 American Society of Mechanical Engineers. Source

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