Christian Wakelam

Controlling Separation on a Simulated Compressor Blade Using Vortex-Generator Jets

Flow control using vortex-generator jets has been used to control a separating boundary layer on the surface of a flat plate in the presence of a pressure distribution equaling that on the suction surface of a compressor blade. A parametric study has been performed in which the skew angle and jet velocity of steady jets have been varied. In addition to steady blowing, the jets have been pulsed over a range of reduced frequency from 0.5 to 7.0. Steady blowing with a jet velocity greater than the inlet flow velocity was found to delay separation on the surface of the flat plate and reduce the loss coefflcient of an equivalent cascade blade by 36 %, relative to the unactuated case. This jet velocity is equivalent to an injected mass flow rate of 0.13 % of the inlet mass flow rate. With pulsed blowing, the same loss reduction was achieved over the unactuated case using 40% less mass flow. This loss reduction, however, required a reduced frequency greater than 6.0 and a peak jet velocity equal to 1.5 times the inlet flow velocity. This corresponds to a jet Mach number in a real compressor of 1.125, pulsing at more than 180 kHz.

Flow Control in a Compressor Cascade at High Incidence

Flow control has been applied on the suction surface of blades within a compressor cascade to remove a turbulent boundary-layer separation that occurs at an incidence of 12.5°. Vortex generator jets and boundary-layer suction through discreet holes have each been applied to the suction surface to push the point of separation from 54% chord to the trailing edge. Corner separations also occurring at this incidence have been controlled by means of endwall suction. The mixed-out stagnation-to-stagnation pressure loss coefficient was measured in each case tested. The measured loss coefficients were used, together with an endwall suction-loss coefficient and a boundary-layer control loss coefficient, to estimate the total loss coefficient for a compressor blade with a representative aspect ratio of 3.5. For such a blade, endwall suction and vortex generator jets on the suction surface were found to yield a 20% reduction in the total loss coefficient relative to the uncontrolled case. Endwall suction, together with boundary-layer suction on the suction surface, was found to yield a 33% reduction in the total loss coefficient. Flow control was also applied to the suction surface at a range of incidences from 0 to 15.5°. Only boundary-layer suction was able to achieve a loss reduction at 15.5°.

Separation Control for Aeroengine Intakes, Part 1: Low-Speed Investigation of Control Strategies

This paper documents the first part of an investigation into control of the separation occurring over the windward lip of an aeroengine intake operating in a crosswind. The results presented are for a low-speed experimental study that investigated the effectiveness of two candidate control techniques: boundary-layer trips and vortex generator jets. The study was conducted using a novel experimental rig that was designed to set up a representative pressure gradient on a two-dimensional intake lip, and which allowed the experiments to be conducted at a larger scale than would otherwise be possible with the available wind tunnel. It was shown that the rig exhibited the same typical flow behaviors as a three-dimensional intake operating at low engine mass flow (low fan-face Mach number) under crosswind conditions. Control techniques were applied to reduce the separation on the intake lip, and consequently reduce the distortion in total pressure at the fan face. Both boundary-layer trips and vortex generator jets positioned on the outside surface of the intake lip were found to successfully remove the leading-edge separation. A combination of vortex generator jets outside and inside the intake further reduced the distortion in total pressure.

ADVACT an European Program for Actuation Technology in Future Aero-Engine Control Systems

The present paper will give an overview about the flow control activities in the project ADVACT launched within the EC 6th Framework. It is addressed to the identification and application of actuator technology for aircraft engines. The primary objective of ADVACT is to enable the achievements of improvements in operation, availability, costs and reduction of environmental impact of gas turbines by the provision of extended in-flight actuation and control of engine parameters.

Separation Control for Aeroengine Intakes, Part 2: High-Speed Investigations

This paper documents the second part of an investigation into how fluidic control can be used to reduce separationinduced total pressure nonuniformity in an aeroengine intake. Flow conditions typical for an intake operating in a pure 90 deg crosswind are recreated in a laboratory-scale experiment. The lip rig concept, discussed in Part 1 (Wakelam, C. T., Hynes, T. P., Hodson, H. P., Evans, S. W., and Chanez, P., “Separation Control for Aeroengine Intakes Part 1: Low-Speed Investigation ofControl Strategies,” Journal of Propulsion andPower, Vol. 28,No. 4, 2012, pp. 758–765), has been developed for application in a high-speed study. The sector rig exhibits the same behaviors as a three-dimensional intake: low-speed separation hysteresis, attachedflowbucket atmoderate fan-faceMach numbers, and shock-induced separation. The flow control method of vortex generator jets is applied to reduce the negative effects of this shock-induced separation.Measurements of static pressure distribution show that separation is delayed to a higher fan-faceMach number when fluidic control is applied. Total pressure measurements in the fan-face plane show that distortion can be reduced over the full range of separated cases.A nonintrusivemethodof inferring the state of the flow in the intake, which could be used in a fully active control system, is also presented.

ADVACT - A European Programme Investigating Adaptive Technologies for Future Aero Gas Turbine Engines

*† ‡ § ** †† ‡‡ §§ , *** ††† , ‡‡‡ §§§ **** This paper will give an overview of flow-actuation systems contemplated in the ADVACT project, a European programme funded under the 6th Framework Programme. The project addresses the application of actuator technology in an aircraft engine environment, in particular flow-control of intake under strong cross-wind conditions, flow-control of low and high speed cascade blades and variable area nozzles by Shape Memory Alloys. The primary objective of ADVACT is to enable the achievements of improvements in operation, costs and reduction of environmental impact of gas turbines by the provision of extended in-flight actuation and control of engine parameters. Extended simulation work along with both material and devices characterization has enabled the ADVACT Consortium to design appropriate actuation systems that are aimed at engineconditions. Simulation and device characterization are the primary objects of this paper along with some insight on construction of rigs for testing under engine like conditions; this latter being the object of future work within ADVACT. Engine performance analysis with the adoption of some of these advanced actuation techniques is also investigated and data on 2 and 3-shaft engines are presented.