06411 Micro Nucleating Bubble Engine

Team MembersSteven NathensonJoseph PawelskiJoaquin PelaezAndrew PionessaBrian Thomson

Project SponsorsDr. CrassidisDr. Kandlikar

Project CoordinatorDr. Walter

Introduction / Project Goals

• Millimeter scale

• Piston like design

• Performance comparison

• Small budget

• Control bubble production

• Mobile

• TO GRADUATE

Alternate Designs

Alternate Designs (cont.)

Alternate Designs (cont.)

Alternate Designs (cont.)

Major / Critical Specifications• Customer Requirements / Objectives

– Be portable and lightweight– Work on principles of bubble nucleation to produce mechanical

oscillations of a piston• Determine appropriate fluid for ideal bubble behavior• Utilize a power supply or a battery in conjunction with a control system to

regulate heater and control bubble growth– Utilize a miniature heating element

• May need to be protected so it does not break or fracture• Must be easily replaced

– Stay within the budget– Create a millimeter-sized engine– Create a proof-of-concept

• Theoretically prove engine design• Create and test a working engine• Benchmark operational specifications, such as operational frequency,

efficiency, and operation time– Runtime

• Must run for about 20 seconds• The liquid reservoir might need be cooled via a heat exchanger to allow for

longer runtimes– Reduce friction between piston and casing

Major / Critical Specifications (cont.)• Functional Requirements

– Contained within (1 ft3) volume– Piston size of 5-10 mm– Must function at around 5-10 Hz

• Design Specifications to Date– Pyrex Cylinder

• ID: 0.218”• OD: .0375”• Operating Temp: -20°F to +446°F

– Teflon Piston– Platinum wire heating element

• OD: 0.002” • Resistivity: 10.6 x10-8 W·m• Length: 1-2 mm

– Base plate with two aluminum electrodes

Feasibility / Technical Concerns

• Piston design – most feasible– Easy to manufacture– Simple– Easy to test– Smallest time of development– Preferred design of sponsor– Risk assessment contained within Pre-Read Package

• QFD Analysis yields concerns– Bubble control– Piston displacement– Piston size– Power input– Accurate theoretical models*

*Not contained within QFD analysis

Heater• During the brainstorming portion of the project, there were several

heater ideas proposed. The initial concepts were:• Straight wire• Square wire• Circular wire• Concentric wire• Metal plate• Additionally, there were several implementation methods proposed

for this heating element. They are as follows:• Resistant wire• Protective plate• Other method…

Fluid bath: pipe flow

Air flow: two flat plateswith upper plate moving

r R

ay

xr0

x

Navier-Stokes Model

r

vr

rrg

dx

dp xx

1

2

1R

rVrvx

2

2

R

VrAFv

Assumptions

•Steady State•One dimensional flow•Fully developed flow•Pressure drop is constant•Constant properties•Laminar

Resulting equation

2

1

a

yg

dx

dp

a

VAF xr

2

2

y

vg

dx

dp xx

Systems ModelR

r

dy

x

hb

h*

Lx1

x2

M1

M2

x1

x2

SYSTEMS MODEL

B2

B1K1

)()()(

0)()(

12112222

2112121111

tfxxKxxBxm

xxKxxBxBxm

Systems Model (cont.)

)(

2)(

)(

2)(

)()(

2)(

212122

2112*

*

122

*

**

rR

rBxx

rR

rxxB

xxxxxdu

dy

du

rddAxxB

yx

yxA

yx

21

*2211

*2211

)(

)(*

rgkxrgxxk

dxrggdxxk

ww

x

ww

Find damper constant B2

Find spring constant K1

Spring constant is derived from the buoyancy force enacted by water on the piston.

• Damper constant B2 represents the shear between the piston and cylinder created by the change in velocity between the piston and water column.

• Shear velocity must be adjusted because of the change in area between the cylinder diameter and the piston based on the conservation of mass equation.

Assumptions:

•Shear forces due to air are negligible•Shear forces within rising water column are negligible *•Shear between the piston and cylinder is calculated assuming shear between infinite parallel plates.•Velocity distributions and vortices created by bubble propagation are negligible, for systems control volume flow is assumed laminar.

*Flow in the cylinder is not fully developed.

Matlab Simulation

• User input parameters• Automatic assumption checks• Current bubble growth function: Mikic et. al. (1970)• Future bubble growth function: Experimentation of our specific conditions

%Laminar flow checkdisp(' ')disp('Is the flow in the fluid bath laminar or turbulent?')disp(' ')for i=1:2001 if(Re(i)>2300) disp('The flow is turbulent') lamturb(i)=0; break else lamturb(i)=1; endend

if(all(lamturb)==1) disp('The flow is laminar')end

Is the flow in the fluid bath laminar or turbulent? The flow is turbulent

Electrical Circuit Diagram

R d

R L

Power Supply

MeasurementsControl System

P_delivered

P_lost

Heater System

Measurements

0

Filtering (if needed)

0

Control System ConceptsControl System Concept #1 – Analog to Digital Converter (A/D)

.

.

.

A/D Converter

N

2

1

AC PowerSupply

Control System Concept #2 – Pulse Width Modulator (PWM

Pulse Width Modulator

Adjustable Duty Cycle,Voltage Supply,Frequency

DCSupply

AC PowerSupply

Control System Concepts (cont.)Control System Concept #3– Oscillator

OscillatorDC PowerSupply

Fixed amplitude,Duty Cycle;Operable frequency range

Control System Concept #4– Function Generator with Bridging Circuitry

FunctionGenerator

Power Outlet(AC)

BridgingCircuitry

Adjustable Duty Cycle,Amplitude, Frequency

Maintains signals shape,Provides a physical meansto apply signal to Heater

Remainder of quarter

• Derive bubble growth equations

• Finalize design

Questions?