Amelioration de la performance des compresseurs et des soufflantes par actionnement plasma.

摘要

This project studies the potential of a new technology to increase the aerodynamic performances of axial compressors and fans. This technology called single dielectric barrier discharge (SDBD) plasma actuator (henceforth referred to as plasma actuator) is an electrical device consisting of two parallel and offset electrodes that are separated by a layer of dielectric material. One of the two electrodes is exposed to the air. The application of a high A.C. voltage at high frequency between the electrodes partially ionizes the air in the vicinity of the electrodes. The ionized air combined with the electric field between the electrodes creates a force that accelerates the air. The effect of the actuator is thus similar to a thin jet. Plasma actuators allow to increase the momentum in the flow without mass addition.;Two aerodynamic applications of plasma actuators have been conceptually studied in this project. The first one is to evaluate their capability to reduce the momentum deficit in the wake of compressor and fan blades in order to reduce rotor-stator interaction noise. The second application is to study how plasma actuators can prevent boundary layer separation on the blade suction side to increase compressor and fan stage pressure ratio and efficiency.;To study these two concepts, a numerical approach (CFD) has been taken.;However, before studying the two proposed concepts, the first step of the project is to numerically model the force distribution produced by the actuator. A model is developed from the combination of the features of two existing models. The force distribution produced by this hybrid model shows the same general characteristics as the one obtained with the most complex models. The force distribution is then implemented in a turbomachinery CFD code using an algorithm that is developed during the project.;Reduction of rotor-stator interaction tonal noise. The proposed concept for this part of the project consists in the use of two actuators (one on each side of the blade) positioned near the trailing edge of a compressor blade operating at a relatively low speed (Mtip = 0.2) to reduce the momentum deficit in the wake linked to rotor-stator interaction tonal noise. Four objectives are identified for this part of the project: evaluate the effect of the actuator strength and position on the blade, estimate the required power and finally evaluate the impact of the actuation method (continuous versus pulsed). Results show that the wake reduction relative to the actuator strength follows a linear relation, that the effect of the actuator position is negligible (as long as the actuators are not too far from the trailing edge) and that the proposed concept consumes a small amount of power in comparison to the one required to drive the rotor that is used in the CFD simulations. However, simulations do not allow us to draw a clear conclusion on the actuations methods.;Finally, results show that the proposed concept can significantly reduce the harmonic amplitude (harmonic amplitude are directly related to the noise emission).;Increase of the pressure ratio in fans and axial compressors. This part of the project aims to show that the use of plasma actuator on the suction side of a blade upstream of the location of boundary layer separation can prevent this separation and allow pressure ratio increase without losing efficiency. To demonstrate the concept, a mean line program is developed to evaluate the performances of conventional subsonic compressor blades and to set reference values. Three objectives are established for this study: evaluate the effect of actuator strength and position and estimate the required power.;The study is carried out using a subsonic compressor blade having a separation zone close to the trailing edge. Simulations show that plasma actuation can effectively suppress the separation zone and that the effect of the position is negligible relatively to the capacity of the actuator to eliminate the separation zone. However, from an energy point of view, the actuator's position has a significant impact on the power that will be required.;Finally, the suppression of the separation zone near the trailing edge of the blade allows an increase in the pressure ratio and efficiency of the blades.;Keywords: plasma actuator, noise, pressure ratio, compressor, fan