university of notre dame particle dynamics laboratory michael p. davis and patrick f. dunn...
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University of Notre Dame Particle Dynamics Laboratory
Michael P. Davis and Patrick F. Dunn
Department of Aerospace and Mechanical Engineering
Particle Dynamics Laboratory
B032 Hessert Laboratory
University of Notre Dame
Notre Dame, IN 46556 USA
University of Notre DameAME - Graduate Student Conference
October 19, 2006
SPONSOR: Honeywell International, Incorporated
Jet Fuel Cavitation in a Converging-Diverging Nozzle
University of Notre Dame Particle Dynamics Laboratory
Brennan (1995).
Cavitation - “the process of rupturing a liquid by decrease in pressure at roughly constant liquid temperature”
FLUENT simulation
Cavitation Fundamentals
University of Notre Dame Particle Dynamics Laboratory
Motivation - Honeywell Fuel Pump• Honeywell product line includes valves, flow controllers, and fuel pumps
• Common to all devices is high flow rates through very small orifices, resulting in cavitation
• Presence of bubbles causes damage to components, vibrations, and a loss of pump efficiency
pitting damage caused by cavitation
University of Notre Dame Particle Dynamics Laboratory
sphericalbubbles slug-like
gas voidsbubbly shock
microbubble nucleioriginating from microparticles or walls
liquid
solid
gas pockets
xflow
Void Fraction = f(x)Pressure = f(x)
Void Fraction = Gas Volume/Total Volume
Problem Description
University of Notre Dame Particle Dynamics Laboratory
€
R˙ ̇ R +3
2˙ R 2 =
1
ρPv + PGo
Ro
R
⎛
⎝ ⎜
⎞
⎠ ⎟3γ
− P∞(t) −2σ
R− 4μ
˙ R
R
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
bubble interface,surface tension
far field,
bubble inertia bubble contents far fieldpressurein liquid
surfacetension
viscous effects
€
P∞(t)
ρ
μ- fluid density
- fluid viscosity
Vapor+
GasR(t)
Bubble Dynamics - Raleigh Plesset Equation
University of Notre Dame Particle Dynamics Laboratory
Raleigh-Plesset in a C-D Nozzle
€
∂∂t
1−α( )A[ ] +∂
∂x1−α( )uA[ ] = 0
∂u
∂t+ u
∂u
∂x= −
1
2 1−α( )
∂Cp
∂x
RD2R
Dt 2+
3
2
DR
Dt
⎛
⎝ ⎜
⎞
⎠ ⎟2
= −Ca
21− R−3γ( ) +
4
Re
1
R
DR
Dt+
2
WeR−1 − R−3γ
( ) +Cp
2
⎛
⎝ ⎜
⎞
⎠ ⎟
(continuity)
(momentum)
(bubble dynamics)
€
α(x) =4 /3πηR3(x)
1+ 4 /3πηR3(x)
Ca =P∞ − Pv
1/2ρU∞2
We =ρU∞
2Ro
σ
Re =ρU∞Ro
μ
Cp =P(x) − Pv
1/2ρU∞2
(void fraction)
(viscosity)
(pressure forcing)
(surface tension)
(liquid tension)
University of Notre Dame Particle Dynamics Laboratory
Transducers measure P
Experimental Apparatus
University of Notre Dame Particle Dynamics Laboratory
University of Notre Dame Particle Dynamics Laboratory
flow
JP-8
H2O
University of Notre Dame Particle Dynamics Laboratory
Void Fraction by Laser Light Scattering
• Initialize counter and increment each time voltage drops below threshold• Compute running average as a function of time and look for convergence• Need a way to calibrate output signal
Flow direction
Vout = f(α
Runningaverage
Test section
CavitationBubbles
Photo-diodearray
HeNelaser
University of Notre Dame Particle Dynamics Laboratory
flow
University of Notre Dame Particle Dynamics Laboratory
flow
University of Notre Dame Particle Dynamics Laboratory
flow
JP-8
H2O
University of Notre Dame Particle Dynamics Laboratory
• The experimentally determined JP-8 mass flux under choked conditions can be used to identify the maximum volumetric flow rates achievable for a given minimum flow cross-sectional area assuming similar, fully choked flow conditions.
Maximum Flow Rate Estimate
University of Notre Dame Particle Dynamics Laboratory
• Reliably predict cavitation in internal flows involving hydrocarbon fuels.
• Obtain experimental void fraction and pressure profiles for model comparison.
• Parallel experimental and computational approach is focused on model development.
• Development of passive and active cavitation control strategies.
Goals of Research - Summary