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A 20-year experience with LMS Amesim:the simulation of positive displacement pumps
Naples, June 27, 2016
Massimo RundoPolitecnico di Torino – Dipartimento Energia
Fluid Power Research Laboratory
New Trends in Fluid PowerDesign & Simulation Symposium
2/25
FPRL at a glance
- 1st course of Fluid Power in Italy (1979)
- 1979 - 2016: about 9500 students
- From 2014: 2 courses in English at M.Sc.
- More than 100 M.Sc. theses
- About 100 scientific papers
- Development of simulation models of
positive displacement machines and valves
Research
Didactics
Laboratory
- 1985: construction of the 1st Lab
- 2005: completion of the new Labwww.fprl.polito.it
3/25
Test facilitiesLUBRICATING PUMPS TEST RIG PUMPS AND MOTORS TEST RIG SERVOVALVES TEST RIG
LOAD SENSING TEST RIGwith steering unit and hydraulic winch
CENTRAL HYDRAULICUNITSDIDACTIC TEST RIGS OTHER RIGS
4/25
Industrial research collaborations
(from 1996, 13 contracts, for a total of about 12 years)
(from 2000, 9 contracts)
(3 contracts)
(2 contracts)
(2 contracts)
5/25
The experience with LMS Amesim
‐ Users since 1995 with v0.3
‐ 1998: 1st international publication on gerotor pump
‐ 2000: presentation at the 1st AMESim Users’ Conference in Paris
‐ Since 2006 used by the students in didactic laboratories
‐ Several customized libraries created in Ameset
6/25
Systems/components studied with AmesimDetailed 1D modelling of positive displacement machines (with customized libraries)• 1997: Gerotor pumps • 1999: External gear pumps • 2000: Swash plate and bent axis pumps, also in cosimulation with MSC Adams (2006)• 2001: Vane pumps, also in cosimulation with MSC Adams (2008)• 2005: Crescent pumps ‐ Swash plate motors• 2012: Single vane vacuum pumps
Vehicle systems• 1999: Variable Valve Actuation ‐ Electro hydraulic braking system• 2002: Lubrication circuit, also aeronautical (2001)• 2004: Clutch actuation ‐ Steering units
Mobile hydraulics• 2001: Hydrostatic transmissions • 2006: Load sensing proportional valves• 2011: Excavator and telehandler hydraulic circuits (coupled simulation with LMS Virtual Lab)Industrial hydraulics• 2001: Hydraulic power unit for hydroforming system
7/257/
Equivalent hydraulic circuit
Need to evaluate the geometric features
N variablechambers
Delivery volume
Suctionvolume
Flow areas Flow areas
drainInternalleakages
J
J+1
Gerotormachine
Variablechambers
The simulation of a positive displacement machine
Flow area
volume
areaarea
j‐th chamber
• Hydraulic volume: continuity equation• Hydraulic resistance: flow equation
8/25
The vector approach
multistage pump built using the supercomponentfacility
(30 chambers !)
MANCO’ S., NERVEGNA N., RUNDO M., et Al. “Gerotor Lubricating Oil Pump for IC Engines”, SAE Transactions, Journal of Engines 107(3), 1998
flow areas
leakages
geometric features
N variable volume chambers in parallel
The number of chambers is a parameter
Hydraulic vector lines
1997
9/25
Numerical evaluation of geometric features
Procedure valid for any shape of the port plate: profiles are supplied as XY data table
port profile Flow area
Numerical technique used to calculate the flow area vs. angle:• Discretization of the domain• Calculation of number of elementary cells belonging to both closed lines• Interpolation of the flow area
chamber profileGerotor pump
10/25
Automatic CAD method
CARCONI G., D’ARCANO C., NERVEGNA N., RUNDO M.: “Geometric Features of Gerotor Pumps: Analytic vs Cad Methods”, Bath/ASME Symposium on Fluid Power & Motion Control, Sept. 12‐14, 2012, Bath, UK
Based on commercial CAD software PTC Creo Elements/Pro (formerly Pro/ENGINEER)
1. Creation of:
• Assembly parts
• Constraints
• Global parameters
• Relations (correct movement)
2. Creation of virtual parts (fluid volume):
• Chamber volume
• Suction / Delivery
• Inter-sections
3. Evaluation of geometric quantities:
• Analysis features
• Relational features
• Numerical derivation
• Simulation
area volume
11/25
inlet
outlet
A B
Variable flow gerotor pump2000
Early ClosingInlet Port
Delayed ClosingDelivery Port
Timing can be varied with respect to the gearing
DCDP
The end of the delivery phase is progressively delayed
The flow area is also function of the sector position
Flow rate vs. sector position
NERVEGNA N., MANCO' S., RUNDO M.: “Variable Flow Internal Gear Pump”, ASME International Mechanical Engineering Congress and Exposition, New York, 11‐16 November, 2001
Piston linkedto the sector
12/25
Selection of the control volumesdelivery volume
variable chambersinlet volume
trappedvolume
constantvolumes
flow area
3 variable volumes
2N+2 variable volumes
Inlet/delivery volumes include connected chambers
A control volume is associated to the space between two teeth and connected to inlet/delivery volumes through flow areas
deliveryphase
suctionphase
Simulated chamber pressureExternal gear pump
inlet volume
13/25
Model validation
Miniature pressure transducer
chambers
inlet
outlet
geometry
driving gear(10 chambers)
driven gear(10 chambers)
2005
Model with 2N+2 variable volumes
Chamber pressure
14/25
Internal gear pump modellingThe approach with only 3 variable volumes is suitable for the evaluation of the pressure ripple
Volume derivatives(analytic expressions)suction volume
delivery volume
trapped volume
15/25
Interaction between bodies (analytic approach)
Contact vane‐stator in a vane pump (detachment analysis)
2001
Force equilibrium on each vane:
MANCO' S., NERVEGNA N., RUNDO M., ARMENIO G., “Modelling and Simulation of Variable Displacement Vane Pumps for IC Engine Lubrication”, SAE World Congress, 8‐11 Mar. 2004, Detroit, USA
Fr = reaction forcesFp = pressure forcesFf = friction forcesFc = centrifugal force
x
( ) ( ) ....mx j cx j
Endstops management (contact with stator track)
If contact evaluation of contact force on the stator contribution to the stator equilibrium
If detachment evaluation of the leakage on vane tip influence on the chamber pressures
Small movements of mechanical parts influence on leakages
16/25
Multibody simulation (fuel pump)
fluid viscosity ≈ 2‐3 cSt
The issue: the current positions of the gears axes is critical for the leakages evaluation
x
yModel in MSC Adamswith all clearances:• inner gear – outer gear• inner gear ‐ shaft• outer gear ‐ housing
Forces on gearscalculated with Amesim
2005
Theoretical eccentricity (not in scale)
Amesim output Adams output
RIELLO Research Contract, 2006
17/2517/
Need of cosimulation
Floating ring
ICE lubricating vane pump
Analysis of vane detachment
The issue: interaction vanes‐ringThe solution: cosimulation LMS Amesim – MSC Adams
LMS Amesim (master)
• User interface• Hydraulic model• Solver
MSC Adams (slave)
Forces on the vanes
Vanes and rings positions
• Mechanical model• Solver
Communicationat constant Δt
2008
18/25
Adams model by
Amesim model by FPRLwithout bodies dynamics
Implementation of cosimulation
Output example
theoretical vane lift
calculated lift
Contact force vane root
Contact force vane tip
Trajectory of ring centre
x
y
Rotor axis(fixed)
interface
PIERBURG Research Contract, 2008
19/25
Vacuum pump for brake booster
Rundo, M. and Squarcini, R., "Modelling and Simulation of Brake Booster Vacuum Pumps" SAE Int. J. Commer. Veh. 6(1), 2013
The issue:Fluid mainly air + small % oil pneumatic chamber… but at the end of the delivery phase 100% oil
hydraulic chamber
Hydraulic‐pneumatic chamber
2012
variable chambersPump geometry
1c pV x
Vc
2 ,p oil airx V V
Virtual piston equilibrium
Mass conservation ,oil airp p Force on piston
2 1 ?p px xYES air + oil NO only oil
oil cV V
The equilibrium of the virtual piston adjusts the volume of air/oil so that
oil airp p
Mass conservation
( , , )oil oil c cp f m V V
(purely hydraulic chamber)
20/25
Model implementation and validation
Supercomponent(3 chambers)
detail
Pneumatic line
Hydraulic line
Time required to empty a 4 L test volume of air
Hydraulic‐pneumatic chamber
21/25
Electric heater
Speed
Measure of lubricating pump energy
Temp.Press.
Flow rate
Closed loop control
RUNDO M., SQUARCINI R., “Experimental Procedure for Measuring the Energy Consumption of IC Engine Lubricating Pumps during a NEDC Driving Cycle”, SAE Int. Journal of Engines 2(1), 2009
Pump under test
Speed vs. time
Temperature vs. time
Q = f(p,T,n)
Cycle
Energy Torque speed dt
2008
22/25
Simulation and validation of the procedure
RUNDO M.: “Energy Consumption in ICE Lubricating Gear Pumps”, SAE Powertrains, Fuels & Lubricant Meeting, 25‐27 Oct. 2010, San Diego, USA
NEDC cycle
Friction data interpolationLoad characteristic(pressure signal from data table)
Gears: chambers, porting, leakages
increasing temperature
23/25
1D simulation of lubricating circuit
lubrication of each cylinder:• main bearing• piston cooling jet• crankshaft drilled holes• conrod bearing
SINGLE OVERHEAD CAMSHAFT DIESEL ENGINE
2003
Circuit layoutLoad on the bearings(supplied asdata file)
FURNO F., RUNDO M.: “Simulazione del sistema di lubrificazione di un motore a combustione interna”, 58° Congresso Nazionale ATI, Padova ‐ S. Martino di Castrozza, Italy, 9‐12 September, 2003
24/25
Overall flow‐pressure curve
Validation: flow rates and pressures
140 °C
Oil pump outletMain galleryHead gallery
90 °C
140 °C90 °C
FURNO F., “The Lubrication Network in Internal Combustion Engines: a Simulation Approach”, 3rd FPNI PhD Symposium, Terrassa, Spain, 30 June – 2 July, 2004.
continuous lines: simulation
dots: experimental values
25/25
Some final remarks / curiosities
• First model of gerotor pump in 1997 ran on a Sun SparcStation 10 @ 50 MHz ‐ 96 Mb RAM
About 2‐3 minutes to simulate a shaft revolution Now about 2 seconds : 2 orders of magnitude smaller !!
• In 1997 an entire month spent for the development of the model of a simple relief valve(at that time the Hydraulic Component Design Library in Amesim did not exist !)
Now the same valve is built in 30 min by the students of the Fluid Power courses
• The nightmare :
When you realize thatyour model no longer runson the new release of a software !!
Fluid Power Research Laboratorywww.fprl.polito.it
Politecnico di Torino