Transcript Folie 1 - Transport Research

New Flow Actuation Concepts to be Studied Within
European Technology Program ADVACT
AVT - 128
RTO-Meeting
Prague, October 4 – 7, 2004
Dr. Sven-J. Hiller
MTU Aero Engine Munich
Contents
Status and Motivation for the Link between Fluid Mechanics and Microsystems
6th Framework Program ADVACT
Flow Actuation Concepts – Examples
Numerical Simulation Issues and Examples
Dr. Sven-J. Hiller (MTU Aero Engine)
2 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Why becomes flow actuation so attractive now?
• First experiments with flow actuation goes back in the 40’s of the last century
Pulsed hot wire triggers instability waves
• Growing interests in flow control due to wider knowledge about the flow physics
• Achievement in e.g. efficiency growth on the traditional design way is limited by the
amount of effort necessary (time and costs) and uncertainties (manufacturing)
• Recent achievements in simulation technique, control science (growing computer
capabilities, more efficient control algorithm, embedded systems) promise new ways
for further efficiency growth and better operability, e.g. control loops with feedback
Dr. Sven-J. Hiller (MTU Aero Engine)
3 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Comparing Aero Engine Industry with Automotive Industry
•
•
•
•
Electronic Microsystems widely used in
modern cars
Premium class cars equipped with
~ 3.5 km (2 miles) wiring
Minor usage of Microsystems in Aero
Engines
Some of the reasons may be:
• Lower number of pieces
• Harsh environment
• Reliability
• less experiences with Microsystems
• high level of optimal designs already
achieved (i.e. efficiency, life cycles)
Expecting a change in the Aero Engine Industry in mid-term time frame
Dr. Sven-J. Hiller (MTU Aero Engine)
4 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Two Major Braches in MEMS Application in Turbomachinery
Flow Actuation by
Microsystems
Micro Turbomachines
(Pumps, Gasturbines)
Autarkic Energy Supplier
due to their high energy density
(replacement of conventional batteries)
Very Local Flow interaction
Active Energy Conversion with
the fluid enables the establishing
of control loops
Benefits: Size, Weight
Benefits: Size, Weight, Control Loops
Step on the way towards a clever,
fully controlled engine
Kang et al. (2003)
(Stanford)
Frechette et al. (2000) (MIT)
Dr. Sven-J. Hiller (MTU Aero Engine)
5 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Vision: Smart Compressor
Objectives:
Active Surge Control
• Increase in Efficiency by better use of
design space in aerodynamics
• Surge Margin
• Blade Vibration
• Increase in efficiency by reduced
clearances
• Reduction in cost and weight by
reduced number of parts
Active Clearance Control
Attempt:
Active Vibration Control
Dr. Sven-J. Hiller (MTU Aero Engine)
• Active Surge Control
• Active Vibration Control
• Active Clearance Control
Using Microsystems and smart materials
6 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Ambition for modern flow control concepts
• Modern aero engines already achieved a high level of efficiency (based on huge
experience basis)
• Further significant increase is a question of benefit / requirements vs. effort
• Regulation and Laws (environmental impact (noise, pollution), taxes)
• Cost (development, manufacturing, maintenance)
• Cost (operation, end-user)
• But: all the statements base on a single “Working / Design / Warranty Point”
consideration
• Reality is a broad spectra of “Working Points”, ”Power Settings”, etc.
• Many different “Off-Design” Conditions (e.g. short range air transportation)
Dr. Sven-J. Hiller (MTU Aero Engine)
7 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Consequences
• The “Time Integral” is the amount of energy used to achieve a certain condition,
location etc.
• A better performance outside the “Design Point” has the potential to reduce the
total amount of energy required
• Improvement of the so-called “Off-Design Performance” (will also increase the
Design Performance as well) promise an energy saving in general
Altitude
Focus on “Off-Design” Conditions under External Control
Short Range vs. Long Range
Mission Time
Dr. Sven-J. Hiller (MTU Aero Engine)
8 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Contents
Status and Motivation for the Link between Fluid Mechanics and Microsystems
6th Framework Program ADVACT
Flow Actuation Concepts – Examples
Numerical Simulation Issues and Examples
Dr. Sven-J. Hiller (MTU Aero Engine)
9 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Attractiveness of Microsystems for Flow Actuation (locally)
• Laws of the Fluid Mechanics are highly non-linear (sometimes chaotic)
• Small change at one side can causes significant change on the other side
• Urgent need to find the most efficient flow scenarios
• Boundary Layer Flow (see also AVT-111)
• Flow Separation and Reattachment
• Transition (onset and delay)
• Unstable Flow (Bifurcation)
• Buoyancy-driven Flow
Dr. Sven-J. Hiller (MTU Aero Engine)
10 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Attractiveness of Microsystems for Complex Flow Scenarios
• Sensitive Flow Scenarios
• Shock location
• Shock – Boundary Layer Interaction
• Vortex-dominate Flow
• Wing-Tip Vortex (Delta-Wing, etc.)
• Noise and Acoustics
• Aero acoustics
• Instabilities (burner instabilities, etc.)
• Bifurcation of the Complex Flow Scenarios
• Flow at Adverse Pressure Gradient (Dynamic Stall, etc.)
• Compressor Surge and Stall
Dr. Sven-J. Hiller (MTU Aero Engine)
11 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
6th Framework Program ADVACT
• EC launched within the 6th Framework the research project ADVACT
“Development of ADVanced ACTuation Concepts to Provide a Step Change in
Technology Used in Future Aero-Engine Control Systems”
• Joint Research Program of Industrial Partners and Universities
• Runs 48 month from July 2004 to June 2008
Rolls-Royce plc
Industria
Birmingham University
MTU Aero Engines
VKI
Sheffield University
Snecma Moteurs
ONERA
TU Dresden
Avio
CNRS
INSA
Turbomeca
Cambridge University
Politecnico di Torino
DaimlerChrysler AG
Cranfield University
Dr. Sven-J. Hiller (MTU Aero Engine)
12 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Main Objectives
• “… generic study of the benefits of expanded actuation capabilities couples to
development of specific technology which will show the capabilities for identified
applications. “
• 9 Work Packages (see John Webster’s Presentation)
• Focus on WP 2 “MEMS Development and Cascade Airflow Control” (Lead: MTU)
• Close link to WP 3 “Boundary Layer Control in Intake and Ducts” (Lead: Snecma)
Partners in WP2:
MTU
Rolls-Royce
Snecma
Onera
IEMN (Institut d’Électronique de
Microélectronique et de Nanotechnologie of CNRS)
Dr. Sven-J. Hiller (MTU Aero Engine)
13 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Compressor Stability
Flow effects involved
• Flow Separation at the blade surface
during Off-Design (Airfoil Stall)
• Induced Flow Separation through 3D
Tip Clearance Flow
• Boundary Layer-Shock interaction,
especially in the tip gap region of the
rotor blade
• Unstable Flow Regime when throttled
(Stall & Surge)
• Instabilities inside the flow (rotating
and non-rotating instabilities)
• Vortex-dominate Flow (Secondary
Vortex / Passage Vortex)
• Corner Stall
Dr. Sven-J. Hiller (MTU Aero Engine)
14 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Origin: Turbomachinery Flow
• Compressor Flow (rotating)
• Off-Design Conditions
• Compressor Stall & Surge
• Tip Clearance Flow
Simplified to
• Cascade Flow (non-rotating)
• Gap between Blade and (non-moving) Casing
• Cold Conditions (Temperature less than any
critical temperature for a actuator device)
• Size in the order of 0.1% …1% of a typical HPC Blade
Chord (20 µm … 200 µm)
• Lab-Scale Demo Test
• information about the flow mechanism involved (Lab-Scale)
• information concerning reliability, certification, etc.
• concepts for possible control loops
• adequate numerical simulation techniques
• development of MEMS technology for actuators
Dr. Sven-J. Hiller (MTU Aero Engine)
15 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Upsizing of a Compressor Working Line
Larger Power Density
Higher Thrust-Weight-Ratio
Upsizing of the Working Line
toward the Efficiency Optimum
D = +2%
Efficiency
Pressure Ratio
DPG = -10%
Surge Margin
Mass Flow Rate
Upsizing of the Working Line enables a significant improvement of the Power Density and
Efficiency based on a modified Compressor Design Concept
The compressor runs stabilised with a lower surge margin but higher efficiency
Dr. Sven-J. Hiller (MTU Aero Engine)
16 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Joint Research Project Between MTU, University of Armed Forces Munich and
Engineering Office for Thermoacoustics (IfTA)
• Objective were:
• to identify some precursors of the LP compressor surge
• to stabilize the LP compressor by air injection into the tip region of the Rotor 1
• Development of a controller device which detects the precursors and reacts on
them (Active Surge Control)
• Test vehicle: Larzac 04 Engine installed at the University
Dr. Sven-J. Hiller (MTU Aero Engine)
17 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Time Signals and Spectra @ Constant Throttle Position with ASC
Opening
of
10
the Valve and
Start of the
5
Control Loop
Aktuator
LVDTs 1,3,5,7,9 und Kulites 1-5 (von oben nach unten), File352
Sensor
0
-5
-10
15.65 15.66 15.67 15.68 15.69 15.7 15.71 15.72 15.73 15.74 15.75
Time [s]
Sensor and Aktuator Signal
66% LPC Speed, 18% Valve Opening (Gear Factor = 30, 1st Search Range)
Dr. Sven-J. Hiller (MTU Aero Engine)
18 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Time Signals and Spectra @ Continuous Throttling with ASC
Sensor
Aktuator
LVDTs 1,3,5,7,9 und Kulites 1-5 (von oben nach unten), File356
7.86
7.88
7.9
7.92
7.94
7.96
Time [s]
7.98
8
8.02
Sensor and Aktuator Signal
66% LPC Speed, 18% Valve Opening (Gear Factor = 40, 1st Search Range)
Dr. Sven-J. Hiller (MTU Aero Engine)
19 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Air Injection Nozzles in front of a Larzac Engine
Injection Channels
Turnable Nozzles
External Air Supply
Injection Casing (view from Rotor 1 forward)
Dr. Sven-J. Hiller (MTU Aero Engine)
20 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Air Injection
• Comparable results from different research groups
• all experiments base on discreet air injection equally spaced around the
circumference
• Typically ~12 air injectors at the circumference used
Injected Air
as % of Core
Mass Flow
Reduced Core
Mass Flow
@ Stall
Scheidler et al.
(Uni Armed Forces,
MTU)
Larzac Engine
2 Stage LPC,
High Speed
5%
~-9%
Weigl et al.
(MIT)
Compressor
Rig
Single Stage
High Speed
3.6 %
~ - 11%
Nie et al.
(Chinese Academy)
Compressor
Rig
3 Stage,
Low Speed
0.056%
~ - 5.8 %
Question: Can the Injection Mass Flow further reduced by a huge number of Micro Actuators?
Dr. Sven-J. Hiller (MTU Aero Engine)
21 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Contents
Status and Motivation for the link between Fluid Mechanics and Microsystems
6th Framework Program ADVACT
Flow Actuation Concepts – Examples
Numerical Simulation Issues and Examples
Dr. Sven-J. Hiller (MTU Aero Engine)
22 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Compressor Rotor Blade near Stall Condition (simulated oil flow)
Origin of Vortex
Huge Secondary Vortex
enhanced by the Tip
Clearance Leakage
High Incidence
Corner Stall
The Key: Tip Clearance Flow -> determine Efficiency and Stall Margin
Dr. Sven-J. Hiller (MTU Aero Engine)
23 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Adaptive Blade Shape
• Control of Curvature means Control of Stall Onset
(in certain limits)
• 4 Options (mechanical)
• Nose-Dropping Devices (DLR Geissler/Trenker)
• Actuated Flaps at Suction Side / Trailing Edge
(ONERA, CEDRAT) (e.g. piezoactuators)
• Shape Adaptive Airfoil (TU Kassel –
Müller/Lawerenz, segmented airfoil)
• Local Thickness Change by surface mounted
devices
• “Flexible” Blade Shape (fluidic, e.g. aspirated /
transpired airfoil) in order to delay dynamic
stall
AVT-111 Chandrasekhara (NASA Ames)
AVT-111 Glezer (Georgia Tec)
Dr. Sven-J. Hiller (MTU Aero Engine)
24 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
MiniTED = Miniature Trailing Edge Devices
• Very small high-lift devices attached at the trailing edge of an airfoil
• Co-operation between DLR (Institute for Aerodynamics Braunschweig) and Airbus
• Transsonic and high Reynolds Number Flow
Rossow (DLR)
•
•
Method applicable as a Virtual Inlet Guide Vane (VIGV) in turbo machines
Typical HPC chord 1 in (~25 mm) -> Flap 1% -> 0.01 in (250 µm)
Dr. Sven-J. Hiller (MTU Aero Engine)
25 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Sub-layer vortex generators
vortex system generated downstream
enhances the energy transport
from the outer flow into the near-wall regions
and energises the boundary layer
Bauer, EADS
AVT-111 Liu (Texas)
Dr. Sven-J. Hiller (MTU Aero Engine)
26 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Aerodynamic Airfoil Shape Change
Controlled Link between
Pressure and Suction Side
Synthetic Jets Array used for “virtual” airfoil
shape change (aspirated / transpired airfoil)
AVT-111 Glezer (Georgia Tec)
Dr. Sven-J. Hiller (MTU Aero Engine)
27 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
What’s New within ADVACT?
• many effects are known
• some are well understood, other partially
• mainly developed with the background of external (wing)
or pure aerodynamics (flat plate)
Our Objective
• bring the effects into a turbo machine environment, e.g. internal aerodynamics
• assessment of the various effects in an unsteady rotor-stator environment
• assessment of the additional requirements concerning certification, reliability, aging,
design and maintenance of an aero engine
Dr. Sven-J. Hiller (MTU Aero Engine)
28 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Contents
Status and Motivation for the link between Fluid Mechanics and Microsystems
6th Framework Program ADVACT
Flow Actuation Concepts – Examples
Numerical Simulation Issues and Examples
Dr. Sven-J. Hiller (MTU Aero Engine)
29 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Simulation Techniques Issues
• Domains simulated embodies very different length scales
• because of smooth mesh coarsening from the actuator to the airfoil the mesh sizes
tend to be very large
• Some Questions to be answered:
• Continuums Mechanics still valid?
• Role of Turbulence Models (URANS) and Wall Treatments
• What’s about DNS / LES / DES?
• Simplification thinkable?
Dr. Sven-J. Hiller (MTU Aero Engine)
30 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Simulation Techniques – Continuums Mechanics still valid?
• Stationary statistics (large number of molecules) and
continuity of transport quantities (viscosity and diffusivity)
must be valid
N *m
 3
• Assumption:
L
 - Density
N - Number of Molecules
m - MoleculeMass
L - Side Lengthof thecube meassured
For Air: Lgas = 1 µm (10-6 m)
For simulation domains with edges larger then 1 µm the application of Navier-Stokes-based
solvers (e.g. standard (U)RANS CFD solvers) are still valid !
Dr. Sven-J. Hiller (MTU Aero Engine)
31 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Characteristic Values
Knudsen Number Kn  
L
Ratio of mean molecular spacing to diameter of typical
gas molecules
>> 1 diluted gas

d
Mach Number
Ma 
Reynolds Number Re 
Dr. Sven-J. Hiller (MTU Aero Engine)
Ratio of mean free path to length scale of the flow
Navier-Stokes with slip or non-slip conditions at the wall
c
a
c*L

Ratio of velocity to speed of sound
sub- / trans- / supersonic flow
Ratio of initial forces to viscous forces
laminar / transient / turbulent
32 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
NASA Test Cases (2003)
• NASA Langley initiated and published 3 test cases for
flow actuators and flow actuation for CFD validation
• Case 1: Synthetic Jet into Quiescent Air
• Case 2: Synthetic Jet in a Crossflow
• Case 3: Flow over a Hump Model (Actuator Control)
Wall-mounted GlauertGoldschmied type body
Dr. Sven-J. Hiller (MTU Aero Engine)
Slot across span
33 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
CFD Validation for Case 3 (Förster, Hiller)
• Usage of in-house and commercial solver (in the frame of a diploma thesis)
• Aim: meet the measured re-attachment point of the separated hump flow
• Assessment of the effects of a Synthetic Jet onto the main flow
Mainf=0.1
Re ~ 106
Synthetic Jet Detail
measured
k-e BSL k-w SST
Jet Slot Width ~ 0.5% Chord Length
Dr. Sven-J. Hiller (MTU Aero Engine)
RNG
SSG
Reattachment Point
34 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Simplification (proposed by Orkwis (Connecticut))
• The effect of a Synthetic Jet onto the main flow will be simulated as a special kind
of momentum sources rather then the detailed flow interaction between the jet and
the main flow
• Pro: still working on the “coarser” main flow mesh with short turn-around times
• Cons: a huge calibration task is necessary in advance (database-like)
Details accurately
reproduced
Steady w/ LDSTs
Time-averaged and
Steady-State+LDST
Solutions: 90˚ SJ
Time-average
Dr. Sven-J. Hiller (MTU Aero Engine)
Orkwis
35 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004
Dr. Sven-J. Hiller (MTU Aero Engine)
36 - 36
RTO-AVT-128 Meeting, Prague, Oct 4-7, 2004