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 SpecificationValueComments Target FuelButane, LPG Full scale massflow200 sccm Control Range20% to 100% and Off Valve should be capable of being commanded to these set positions using TBD electrical signal (PWM, analog, or other) Fuel Temp10C to 40CWide vapor pressure range is significant design challenge Accuracy+/- 20% of Set PointAverage over any 1 second interval Allowable Pulsation0 to 200% of FS 0 to 150% of FS 0 to 120% of FS 50 msec Power Consumption< 50 3 to 6 VDC Includes any power dissipation for control signals Mass< 10 grams InterfaceTBDIn: LPG Fuel canister Out: Fluoropolymer tubing Electrical: Flying Lead

LL: Valve Concept Rough concept for initial performance requirements –Actual requirements driven by more thorough design review Pressure Regulator Low Frequency DC modulation Flow Regulator Pulse Width Modulated Valve Controller Fuel Pvap(T) Fuel Mass Flow Temp Flow SP

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: K, BP: K Flash Point: 213 K Auto-ignition Temp: 773 K Cost: ~0.70 $/gal *all values for 1 atm

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?