Transcript Microfluidics and Valve Design

Microfluidics and Valve Design
Mark Barineau
Ryan Slaughter
Presentation Overview
• Lincoln Laboratory goals
• Micro- and Macroscale
Fluidics
• Governing Physics
• Valve and Actuator
Types
• Related Technologies
• Butane/LPG Properties
• FEA Intro
Critical Findings
• Distinction between microfluidics and
microvalves
• Applicable valve, actuator, and sensor
technologies have been developed
• Butane/LPG is a good choice
LL: Fuel Metering Valve
• Need compact, low-mass system to meter fuel flow in prototype TE
microgenerator system
– Relevant to other micropower applications, as well
• Design goals:
– Automatic control to accommodate varying electrical loads
– Compensate for fuel vapor pressure
– Integration into fuel tank plumbing
– Very low mass: < 10 grams including tank adapter
– Very low power: < 50 mW
– Operability with LPG fuels: butane and propane
– Act as compact massflow controller
LL: Candidate Performance
Specification
Specification
Value
Comments
Target Fuel
Butane, LPG
Full scale massflow
200 sccm
Control Range
20% to 100%
and Off
Valve should be capable of being
commanded to these set positions using
TBD electrical signal (PWM, analog, or
other)
Fuel Temp
10C to 40C
Wide vapor pressure range is significant
design challenge
Accuracy
+/- 20% of Set Point
Allowable Pulsation
0 to 200% of FS
0 to 150% of FS
0 to 120% of FS
Power Consumption
< 50 mW
@ 3 to 6 VDC
Mass
< 10 grams
Interface
TBD
Average over any 1 second interval
< 10 msec
10 to 50 msec
> 50 msec
Includes any power dissipation for control
signals
In: LPG Fuel canister
Out: Fluoropolymer tubing
Electrical: Flying Lead
LL: Valve Concept
Fuel
Mass Flow
Fuel
Pvap(T)
Temp
Flow SP
Pressure Regulator
Low Frequency
DC modulation
Flow Regulator
Pulse Width
Modulated
Valve Controller
•
Rough concept for initial performance requirements
– Actual requirements driven by more thorough
design review
Valve Components
•
•
•
•
•
•
Fluid reservoir
Actuator
Restrictive element
Sensor(s)
Controls
Interconnects
Micro- vs. Macrofluidics
• Microfluidic—devices
and/or flow
characteristics
• Knudsen number
– Kn<0.3, Continuity
– Kn>0.3, Statistical
mechanics
Fluids (2.005) Review
• Navier-Stokes Eq.
• Mass Continuity
• Reynolds Number
Working Fluid: Butane, LPG
• High heat of combustion (~50
MJ/kg)
• Stable storage and
manipulation
• Clean burn
• Reliable, cost-effective valve
solutions exist
• Safe for lab use => gas
detection tools available
Butane Properties*
• Density:
– 2.46 kg/m3 gas (288 K)
– 600 kg/m3 liquid (272 K) (roughly half that of H20)
• MP: 135.4 K, BP: 272.6 K
• Flash Point: 213 K
• Auto-ignition Temp: 773 K
• Cost: ~0.70 $/gal
*all values for 1 atm
Butane Properties
Butane Properties
Butane Properties
Butane Properties
Fundamentals of FEA
Conclusions
• Microfluidics/Valve to Fluidics/Microvalve
• Applicable valve, actuator, and sensor
technologies are available for our device
• Butane/LPG is a reasonable fuel
Next Steps
• System concept/design refinement
– Confirm valving liquid or gas
– Actuation
– Closed Loop Sensing/Controls
• Learn from other groups (especially
related to DFM)
Questions?