hydromechanical system modelling using simscape ... · vsvsv xi se mb e off. temperature...
TRANSCRIPT
Trusted to deliver excellence
© 2015 Rolls-Royce plc and/or its subsidiaries
The information in this document is the property of Rolls-Royce plc and/or its subsidiaries and may not be copied or communicated to a third party, or
used for any purpose other than that for which it is supplied without the express written consent of Rolls-Royce plc and/or its subsidiaries.
This information is given in good faith based upon the latest information available to Rolls-Royce plc and/or its subsidiaries, no warranty or representation
is given concerning such information, which must not be taken as establishing any contractual or other commitment binding upon Rolls-Royce plc and/or
its subsidiaries.
Hydromechanical System Modelling
Using Simscape & SimHydraulics to
Expand Capability
Martin Kirkman and Adam Brooke
Rolls Royce Controls and Data Services
Fuel & Actuation Sub-Systems 7th October 2015
Contents
Background
• Who are Rolls Royce CDS ?
• Systems modelling in Rolls Royce CDS
• Use of Simscape/SimHydraulics
Case studies
• Case 1: Valve seal cavitation
‒ Root cause
‒ Fix
• Case 2: Servo valve damage
‒ Root cause
‒ Further understanding
‒ Potential fix through rapid modelling
The way forward
Background
Who are Rolls Royce CDSElectronic Engine Control (EEC)
i.e. software
Pump & Fuel
metering Unit
Engine Burners
Engine Variable Geometry
Design & Manufacture
of Engine Control
Systems.
The Engine
“Intelligence”
Who are Rolls Royce CDS Engine Manifold Ring
Intricate Connecting Pipework
Fuel
Control
Fuel
pump
Fuel
filter
Pipework to
engine
manifold
Hydromechanical Unit
Aircraft
supply
Significant potential for
mechanical and/or fluidic
resonance.
Systems Modelling in RR CDS
Matlab and Simulink• Dynamic models of hydromechanical units used for performance analysis and control law
design • Uses models of pressures, flows & valves to represent the system
• Models built from complex, non-linear, stiff PDEs.
• Reasonably accurate representation
• Aid investigation analysis work through application of tolerances and special cases
Application of SimHydraulics• Using SimHydraulics to increase fidelity of models through use of the physical modelling
environment.
• Applications include:• Pump ripple
• Assess overboard leakages in engine pipe breakage
• Emergency shutdown – water hammer & fluid compressibility
• In-service support issues
- Dynamic seal cavitation investigation
- Servo valve O-ring
Case Studies
𝒄 = 𝑲 𝝆
Where
c = Speed of sound (proportional
to peak frequency)
K = Bulk modulus
𝝆 = Density
Property SimHydraulics
Density (𝑘𝑔/𝑚3) 745
Bulk Modulus (P𝑎) 8.9× 108
Temperature 100oC
𝒄 = 8.9×108745 = 1093 m/s
Principles of Resonance
Res
pons
eR
espo
nse
Res
pons
e
Single source closed ended system
• Metering Valve bore
Sou
rce
Sou
rce
Sou
rce
Sou
rce
¾ standing wave – maximum oscillation
Whole standing wave – minimum oscillation
¼ standing wave – maximum oscillation
½ standing wave – minimum oscillation
Res
pons
e
Case Study 1 - Valve Dynamic Seal
Valve Dynamic Seal- Background• Cavitation damage observed on in-service units after being returned for
failed engine starts
- Only occurring on relatively new units incorporating a new design of the valve.
• Assistance asked by Customer Support Services to investigate the problem.
• Beyond the normal capability of “conventional” Simulink models- SimHydraulics used to model internal passageways leading to damaged area
- Pump ripple suspected to be causing the issues
• Significant resonance observed in the model- Used to support testing to focus accelerated damage on the test rigs
• Cavitation caused by amplification of pump ripple within the valve bore.
Definition of internal path
Cross sectional areas continually decreaseThis amplifies the pressure wave at resonant point
Lp(pump ripple)
Amplification of 1030Hz down the bore (1/4 wave)
Pre
ssu
re
7854Hz around the seal ring 2 holes
Pre
ssu
re
Valve seal - Solution Support
Modelling conducted on original entry-into-service (EIS) metering valve
to observe the differences in resonance excitation
- No damage had been observed on any of these units
- Main reasons for this;
• Larger internal volumes – prevent amplification of ripple
• 10 cross drilling removing high frequency peak.
Comparison conducted on resonant response of EIS, the revised design
and a suggested mod for the revised design which included;
- New screw cap to increase volume
- Reworked piston to increase internal volume and give additional cross
drillings
Valve Dynamic Seal Cavitation Solution
• Similarities to EIS – design pedigree
• Larger fluid volumes
• Re-introduction of 10 holes
Piston bore diameter increased to
increase internal volume
Piston with additional machining to
increase internal volume
Screwed Plug with additional machining to
increase internal volume
The number of radial holes in the Piston
increased from 2 to 10
500 600 700 800 900 1000 1100 1200 1300 1400 15000
5
10
15
20
25
Frequency of excitation (Hz)
Ord
er
of
ma
gn
ific
atio
n o
f L
p s
ou
rce
rip
ple
Response to excitation frequencies at the bal seal midpoint between two cross drillings
FMU EISFMU RevisionFMU Modified on TestFMU New Production Standard
EIS, Revision and new standard response to ripple
Idle range
Geometry of EIS, revision and
new modified standard
compared for amplitude
increase relative to frequency
of oscillation.
Modifications can be seen to
bring the peak amplitude back
to around 700Hz and the
amplification at flight
conditions below that of the
EIS standard.
These peaks can be expected
to shift ±70Hz with fuel type
and temperature.
Rest of flight regime
7854Hz around the seal ring 10 holes
Pre
ssu
re
Case study 2 – Servo Valve ‘O’ Ring
Servo Valve (SV) - Background
• In-service SV ‘O’ ring seals cracking
resulting in fuel leaks
• Approached by Customer Support after
the successes of valve dynamic seal
analysis to see if resonances are
present.
• Details of the internal drillings of the unit
provided in the Low pressure (LP) return
pathways for all servo valves.
Internal Body Drillings (fluid pathways)
VSVSV LP port
VSVSV LP port
MV - Metering Valve
VSV - Variable Stator Vane
SimHydraulics Representation
Conn1
SOVSV
HP estimate
In
Out
PATH ABCD
HP estimate
In
Out
PATH 1234
HP estimate
Conn1
Oscilatory source
A B
LP inlet
Conn1
FRTT1FRTT
Resonant peak of all three servo valves at 20oC
0 200 400 600 800 1000 1200 1400 1600 1800 20000
2
4
6
8
10
12
14
16
18
20
Frequency (Hz)
Rip
ple
mag
nific
atio
n (fa
ctor
)
MVSV
SOVSV
VSVSV
Taxi
Cru
ise
Clim
b
Take off
Temperature sensitivity at Servo Valve
0 200 400 600 800 1000 1200 1400 1600 1800 20000
5
10
15
20
25
30
Frequency (Hz)
Rip
ple
mag
nific
atio
n (fa
ctor
)
-45 DegC
0 DegC
100 DegC
165 DegC
20 DegC
SimHydraulics determines
density, compressibility and
viscosity through lookup tables
based on temperature.
Temperature Peak frequency Peak amplitude
-45 1289 16.42
0 1156 18.55
20 1109 19.44
100 964 22.86
165 880 25.54
𝒄 = 𝑲 𝝆
Taxi
Pump ripple definition
Pump ripple is made up
of multiple sinusoidal
waves being driven at
different harmonics of
the pump ripple
frequency.
For this reason we
cannot just consider
the simple frequency of
the pump.
0 1000 2000 3000 4000 5000 6000 7000 80000
10
20
30
40
50
60
70
80
90FFT of source pump ripple MTO (7950RPM)
Frequency (Hz)
FFT
Am
plitu
de
0 1000 2000 3000 4000 5000 6000 7000 80000
10
20
30
40
50
60
70
80
90FFT of source pump ripple Taxi (5000RPM)
Frequency (Hz)
FFT
Am
plitu
de
FFT of three pump signals
0 1000 2000 3000 4000 5000 6000 7000 80000
10
20
30
40
50
60
70
80
90FFT of source pump ripple Cruise (7500RPM)
Frequency (Hz)
FFT
Am
plitu
de
Taxi: 1st, 2nd, 3rd
Cruise: 1st, 4th, 3rd, 2nd
MTO:, 4th, 2nd ,1st ,5th ,3rd
Extended frequency response
Due to the amplitudes
of pressure ripple at the
higher harmonics must
consider the frequency
response plot beyond
the fundamental pump
frequency.
Horizontal blue lines
represent cruise
harmonics for
reference.
Is there a solution?
Drilling directed towards FRTT Sol V in addition to RSOV
Feeding in test data from rig
0
1
2
3
4
5
6
7
8
3000 4000 5000 6000 7000 8000 9000
Am
plif
icat
ion
Pump speed (RPM)
In-service pump amplification of ripple at the SOVSV
CurrentHMU
New HMU(easy mod)
Use select samples of
pump ripple from test
data.
Pressure ripple is complex
(not simple sinusoidal as
used for the frequency
sweeps)
Can see clear maximum in
the Taxi regime the region
of 7 times magnification.
Taxi
Dry
ru
n
Cru
ise
Clim
b
Take
off
The way forward
How to tackle the future
Return of units
Test rig data
SimHydraulicsanalysis
Solution and lessons learnt
Lessons learnt
SimHydraulicsanalysis
More robust design
Current successes Future desire
Design of dead ended pathways should
not reduce in cross section down the path.
Path length resonances should be
considered for pump ripple coincidence.
Build in greater analysis depth through
use of tool. Replace current practice with
higher fidelity models.
Investigate potential issues before they
occur on young units and ensure good
design going forward on new projects.
Any Questions?