Project 2: Study of Separated Flow - PowerPoint Presentation

Slide1

Project 2: Study of Separated Flow in a Low- Pressure Turbine*

Joshua Combs, Aerospace Engineering, Junior, University of CincinnatiDevon Riddle, Aerospace Engineering, Senior, University of CincinnatiASSISTED BY:Michael Cline, Graduate Research AssistantDr. Kirti Ghia, Faculty Mentor*Sponsored by the National Science FoundationGrant ID No. DUE-0756921

1

Project Goals

Goal 1: Understand the phenomenon of flow separation on streamlined bodies. Goal 2: Understand methodologies for analyzing and controlling flow separation.

2

Objectives

Objective 1: Investigate characteristics of the low-pressure turbine.Objective 2: Explore methods of flow separation and control. Objective 3: Disseminate findings in a technical report.

3

Motivation

Reduce engine weight (COST!!) i.e. use fewer bladesIncreases the amount of work done by each bladeAdverse pressure gradient and low Reynolds number induces flow separation thereby decreasing low-pressure turbine (LPT) efficiencyMust CONTROL flow in LPT to reduce flow separation

4

Terminology

Adverse Pressure Gradient (APG): Pressure increases in the flow direction

Flow Separation: Detachment from body surface

Michael Cline, 2012 AY-REU Program

5

John Anderson, Fundamentals of Aerodynamics, 5th

Terminology continued

Reynolds Number (Re): Dimensionless quantity representing the ratio of inertial forces to viscous forcesIndicates whether flow is laminar or turbulent

Re ≈ 10e5

Re ≈ 10e6

Transition Region:

Zone between laminar and turbulent flow

Boundary Layer (BL):

Thin viscous region adjacent to the body

6

John Anderson, Fundamentals of Aerodynamics, 5th

Flow Control Methods

Two main categories:

PassiveTrip WireVortex GeneratorsRoughness…There are others, these are just to name a few

ActiveBL SuctionSynthetic JetPlasma Actuator

7

Passive Control

TripwirePromotes transition from laminar BL to turbulent BL Increases momentum to overcome APG

(Top-Bottom):

“Drag Reduction on Aerodynamic Shapes with Ground Effect”, http://www.aerospaceweb.org/question/aerodynamics/q0228.shtml

Vortex Generator“Re-energizes” BLDelays flow separation

8

Active Control

Adds momentum through a body force.Proven to reattach flow effectively; no fluid injection

Plasma Actuators

9

Professor Wei

Shyy

University of Michigan

Types of Plasma Actuators

Single Dielectric Barrier Discharge (SDBD) Plasma ActuatorsGlow Discharge ActuatorsPlasma Synthetic Jet Actuators

10

Single Dielectric Barrier Discharge Plasma Actuators

Widely utilized Desirable features for use in air at atmospheric pressuresActive airfoil leading edge separation controlControl airfoil dynamic stallBluff body flow controlBoundary layer flow controlInternal and external flow applications. Effective at high subsonic, transonic, and supersonic Mach numbers

Two electrodes separated by dielectric barrier material. One electrode on aerodynamic surface exposed to airCovered electrode encapsulated in dielectric materialVoltage is applied igniting the DBDUnique: sustain large volume discharge at atmospheric pressure without arcing. Self limiting.Flow control created through generated body force vector field mixing with the external flows momentum.

11

Experiment using SDBD actuators

Cylinder Side image of the smooth flow closely attached to the cylinder.Close up on the flow behind the cylinder. Wake is minimized.

12

Professor Wei

Shyy

University of Michigan

Experiment using SDBD actuators continued

Cylinder Side image of flow without the use of SDBD.Close up on the flow behind the cylinder. Wake is large and out of control.

13

Professor Wei ShyyUniversity of Michigan

Plasma Synthetic Jet Actuator

Designed for flow control that consists of an annular electrode in quiescent and flat plate boundary layer flows. SJA formed from the working flow of the systemName came from:Circular plasma region produced on the actuation generates vertical zero-net mass flux (synthetic) jet.

Actuator pulses forming a starting vortex ring. Advects ahead of jet and secondary vortex rings near actuator surface. Pulsing frequency is varied, creating multiple vortex ringsVortex ring interactionsIncreases peak velocityIncreases streamwise extent of the jet.

14

Experiment using Synthetic Jet Actuators

Investigating plasma actuators and synthetic jets to develop a plasma flow control device that is more effective. Observed varied pulse frequencies and jet characteristicsPeak velocitySteady operation of the actuator without pulse frequenciesConstant velocity

15

Experiment using Synthetic Jet Actuators continued

Both graphs show the streamwise distribution of local maximum mean axial velocity Peak velocity pulsing at 10 HzOptimum time of operation is less than 24 msInteresting observation being that it never returns to zero velocitySuggests optimum operational frequency closer to 10 Hz.

16

Computational Fluid Dynamics

Method of analyzing fluid mechanics with theoretical and experimental techniquesUtilizes algorithms and numerical methods to solve and analyze fluid flow problemsComputer carries out the calculations of time dependent interactions between the body and the fluid

17

Generate “baseline” results for the LPTLearn how to model flow and implement into ANSYS Fluent (CFD software)Learn to used programming languages required for CFD (i.e. C++)

18

…Future Work

Timeline

Weeks:12345 6 78910111213Learn characteristics of turbineUnderstand flow separationUnderstand transition of flowStudy flow control strategiesPosterFinal ReportJournal PaperDue Final Day

19

Questions?

References

http://

projei.tistory.com/47

Huan

,

Junhui

,

Separation Control Over Low Pressure Turbine Blades Using Plasma Actuators,

University of Notre Dame, 2005

Hilbert, Brian F.,

Drag Reduction on Aerodynamic Shapes with

Groudn

Effect,

Clarkston University, 2011

Xiaoping

Xu

, Zhou

Zhou

,

Ruijun

Fan,

Junli

Wang,

Investigation of Active Flow Control on Aerodynamic Performance of HALE

UAV Airfoil,

Second International Conference on Computer Modeling and

Simulation, 2010

Shin, J.,

Narayanaswamy

, V., Raja, L.L., Clemens, N.T., "Characterization of a Direct-Current Glow Discharge Plasma Actuator in Low-Pressure Supersonic Flow,"

AIAA Journal

, Vol. 45, No. 7, pp. 1596-1605, 2007.