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Final Design Testing in Sponsor's lab

For the final design test, we moisturized a dry air sample (provided by Dr. Jooil Kim) using the piezo atomizer and fed the mixture into a Greenhouse Gas Analyzer (GHG). The image below shows the chamber setup and data collected by the GHG displayed on the monitor.

Mixing Chamber - Optimized Horizontal Injection

Mixing chamber injection with the water tank at an optimized water height. Keeping water level within 1 cm above piezo device prevents from excessive pressure that can lead to leaking.

IMG_2724.MOV

This final mixing chamber model was machined using polycarbonate material for ease of manufacturing and to help visualize the mixing the water vapor and air samples.

Computation Fluid Dynamics (CFD) modeling was utilize to optimize the distribution of water vapor particulates injected from the side of the chamber into the injected air stream (Volume Fraction close to 1 means a completely dry air composition).

Piezo Fitting

Made to house the Piezo atomizer so that input water can be moisturized into the side of the mixing chamber. The fitting is machined using hand milling tools and is made of 6061 Aluminum and is sealed to ensure no leaking using a silicone adhesive.

Cross Section View: Water entrance at left, mist exits at right

External view

Base Fitting

Cap Fitting

Test Stand - Panel Design & Water chamber

The Test Stand is used to hold the humidification chamber and water tank on it to easily run tests. There is a worm lamp and L-brackets on the stand for varying Humidification Chamber sizing. The stand and legs themselves were lasercut out of 1/2" acrylic.

Piezo Circuit - Duty Cycle Adjustment

The second and final iteration of the piezo circuit utilizes another 555 timer circuit that induces a duty cycle on the original piezo circuit. Two circuits are linked in series where the first creates a duty cycle at 1.6kHz and the second circuit physically vibrates the piezo device at 113 Hz. The second circuit also can not alter frequency anymore and only operates at its resonant frequency. The duty cycle was able to be lowered to 5.8% of the original atomization rate using a ratio of resistors and the potentiometer. This circuit was then soldered on to a PCB in order to ensure repeatability and avoid faulty connections

Findings:

Can induce piezo to atomize water from a range of 0.0067g/min - 1.17 g/min
Piezo has a ramp up time of ~30 seconds to reach steady atomization rate
Potentiometer alters the atomization rate linearly

Final PCB Piezo Circuit:

Left: Duty Cycle Adjuster. Right: Fixed Frequency Atomizer

Circuit Diagram of Final Piezo Electronics

Mixing Chamber- Horizontal Injection Risk Reduction

The team's second model utilizes a side injection methodology where the Piezo atomizer is spraying its mist into the side of the mixing chamber. The chamber is designed to precisely inject air from the top of the chamber via a baffle as well as a funnel to flush out the moisturized air at the bottom of the chamber.

Findings:

Side water vapor injection allows the stream to inject perpendicular to airflow
Funnel at bottom allows for flow to follow gravity
Baffle creates mini jets that create turbulent flow before mixing with water vapor
Chamber is too wide to fully mix with a weak water vapor stream

Chamber 2.0 video.MOV

Risk Reduction model made out of recycled and 3D printed parts

Cross sectional view of the CAD model

Piezo Circuit - Frequency Adjustment Circuit

The first model of the circuit would atomize the piezo device at different frequencies. The piezo would operate at its maximum capacity at its resonant frequency of 113 kHz. Then using a potentiometer, the frequency could be adjusted. When deviating from the resonant frequency, the piezo will atomize at lower rates in hopes to achieve the air moisturization goal range.

Findings:

Deviating from resonant frequency creates issues with leaking from the piezo surface
- makes flow inconsistent
Lowers the atomization rate but too sensitive to use with hand turn potentiometer
Altering frequency does not scale linearly with atomization rate

Initial Frequency Adjustable Piezo Circuit. The top figure is the circuit diagram that was followed to atomize the piezo. The bottom figure shows the circuit connected on a breadboard and operating on the piezo connected to a water bottle for testing.

Mixing Chamber - Internal Injection Risk Reduction

The first model the team designed involved a multi level system intending for the water vapor and air sample to be distributed at the bottom of the chamber and mix at they rose gradually through the baffle and out the chamber from the outlet at the top.

Risk Reduction Findings:

Moisturized air not rising
Baffle blocks atomized water from rising
Piezo position not ideal
- atomized vapor falls back down

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Cross sections of mixing chamber. The top figure shows the air inlet coming from the side of the chamber where it is then distributed evenly in the lower level using a (name).

The water inlet cross section. Water spreads into the bottom of the chamber where the piezo atomizes it and forms water vapor for mixing.

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