Study of Cavitation on a Gerotor pump with 1D Modelling ... · 1D Simulation Model The model has 133 total flow volumes, 110 of which are pipe sub-volumes D. Buono, Study of Cavitation

Study of Cavitation on a Gerotorpump with 1DModelling Approach

A. SENATORE , D. BUONO, E. FROSINA

DEPARTMENT OF INDUSTRIAL ENGINEERING, UNIVERSITY OF NAPLES FEDERICO II, VIA CLAUDIO 21, NAPLES 80125, ITALY

GT Conference 2016October 17 – 18, 2016

Outlook

• Introduction

• Test Equipment and Measuring Method

• 1D Simulation Model

• Results

• Conclusions

D. Buono, Study of Cavitation on a Gerotor pump with 1D Modelling ApproachGT Conference 2016 - October 17 – 18, 2016

Introduction

• Engine: 2 cylinder• Displacement: 875,4 cm3

• Max Power: 80 kW at 5500 rpm• Max Torque: 145 Nm at 1900 rpm

ENGINE

DESCRIPTION


IntroductionPUMP

• Outer Gear: 10 Teeth• Inner Gear: 9 Teeth• Displacement: 5.2 cm3/rev


Introduction


NO CAV

CAV

NO CAV CAV

Test Equipment and Measuring Method

P1 = Mean Delivery Pressure Transducer

P2 = Mean Suction Pressure Transducer

P3 = Instantaneous Delivery Chamber

Pressure Transducer

P4 = Instantaneous Suction Chamber

Pressure Transducer

Q = Flow Meter

R1 = Suction Throttle Valve

R2 = Suction Calibrated Orifice

R3 = Delivery Calibrated Orifice

R4 = Delivery Throttle Valve





Suction

DeliveryCalibrated

Orifices


Full Synthetic 5W40 Long Life Engine Oil

Viscosity (ASTM D445)80 cSt @ 40 °C /

13,7cSt @ 100 °C

Viscosity Index 176

Sulphated Ash (ASTM

D874)1,3 wt %

Phosphorous 0,1

Flash Point (ASTM D92) 231 °C

Density (ASTM D4052) 0,85 g/ml @15,6 °C

Total Base Number (ASTM

D2896)

11,8

MRV (ASTM D4684) 24,453 cP @ -35 °C

HTHS Viscosity (ASTM

D4683)

3,9 mPa ∙ s @ 150 °C

Oil Properties



Dario Buono, Fulvio Domenico Schiano di Cola, Adolfo Senatore, Emma Frosina, Giorgio Buccilli, Jonathan Harrison, 2016, “Modelling

approach on a Gerotor pump working in cavitation conditions”, 71st Conference of the Italian Thermal Machines Engineering Association,

ATI2016, 14-16, September 2016, Turin, Italy

1D Simulation Model

Discretization of flow passages in the 1D model

The 1D pump flow model is

discretized into many volumes

comprised of pipes and flowsplits

(volumes), and pipe passages are

further discretized into

subvolumes. The 1D Navier-

Stokes equations, namely

conservation of mass, momentum

and energy are solved every

timestep in every subvolume.

Conservation of species is also

considered to solve for species

transport throughout the system.

In the figure, the flow volumes

used in the model are shown by

alternating colors. Both the inlet

and outlet ports are divided into

three sections for more

accurate wave propagation

through the port.


111D Simulation Model

Since the pump has 10 outer teeth, there are 10 chamber volumes, and one cycle of the pump is represented as

one revolution of the outer gear. The flow path from the oil pan to the chamber volumes is highlighted in blue,

while the flow path from the chambers to the outlet is highlighted in red.

The leakage path between chambers is highlighted in green. The changing volume in each "Vol1", Vol2", etc…

part pulls the oil from the pan into each chamber as its volume expands. Then when the volume in each chamber

compresses, the oil is forced to the outlet side of the pump.

The internal leakage between each chamber is modeled with parts "gap1", "gap2", etc…


Three internal leakage paths are used in the model. The dominant path is highlighted green (leakage between teeth), the two minor paths are highlighted orange and pink.

1D Simulation Model


The 1D model was built directly from the CAD model of the pump using theGEM3D pre-processor of GT-SUITE.

1D Simulation Model


1D Simulation Model

The model has 133 total flow volumes, 110 of which are pipe sub-volumes


There are three distinct sections for both the inlet and outlet ports, to represent the flow area between the pumping chambers and these port sections.

Free/dissolved gas is included in the model, based on Henry’s Law

A time constant is used to control the rate at which air goes fromdissolvedfree state and vice versa

The amount of gas that can be dissolved in a liquid at steady state isproportional to the pressure and dependent on the Bunsen coefficient, B

The Bunsen coefficient for oil/air mixtures is on the order of 0.08-0.09

The model assumes no free air at the oil pickup tube inlet, but 100%dissolved air in the oil

1D Simulation Model

atmliqssdgas

P

PBVKbarV )273,1(,

Ga

s d

issolv

ed

Pressure

B


ResultsComparison between model results and experimental data with a Toil of 80⁰C

and a suction tube orifice diameter of 15mm





ResultsComparison with different suction tube orifice diameters, while holding outlet pressure at 3 bar and 80⁰C

pout = 3 bar

MASS

FLOW-RATE


NO CAV

CAV




ResultsComparison with different suction tube orifice diameters, while holding outlet pressure at 3 bar and 80⁰C

pout = 3 bar

SUCTION

PRESSURE





0

1

2

3

4

5

6

0 60 120 180 240 300 360

PD

EL

IVE

RY

[b

ar]

Angle [deg]

3000rpm - TOIL=80°C

Results

NO CAV CAV

0

1

2

3

4

5

6

0 60 120 180 240 300 360P

DE

LIV

ER

Y [

bar

]Angle [deg]

3000rpm - TOIL=80°C

Results

15mm

5mm

Pressure pulsation comparison at 3000 RPM and 80⁰C

NO CAV

CAV




ResultsInfluence of oil type and suction tube diameter on pump mass flow

Toil = 20⁰C

Toil = 80⁰C





Conclusions

• A numerical and experimental investigation on thecavitation in a gerotor oil pump has been done

• The pump has been forced to cavitate varying thesuction pressure.

• An experimental investigation has been performed bythe University of Naples “Federico II” on a hydraulic testbench.

• The Pump performance in no-cavitating and cavitatingconditions has been measured; these data have beenused to compare to the 1D simulation model.D. Buono, Study of Cavitation on a Gerotor pump with 1D Modelling Approach

GT Conference 2016 - October 17 – 18, 2016

Conclusions• The comparison between the model results and

experimental data has shown a good accuracy with amaximum gap of 7%.

• The model has demonstrated to correctly predict cavitation

• The model is able able to predict the power request of the pump


Work in progress

THANK YOU FOR YOUR ATTENTION

A sincere thanks to:Giorgio Buccilli and Jonathan Harrison

Documents

Study of Cavitation on a Gerotor pump with 1D Modelling ... · 1D Simulation Model The model has 133 total flow volumes, 110 of which are pipe sub-volumes D. Buono, Study of Cavitation