3D Printing

One of the classes I am in this semester is 2.014: Engineering Systems Development (or something like that) ie. the Rapid Development Group. I’ve been involved with the Rapid Development Group for two semesters now. The Rapid Development Group is working on  the Seawater/Aluminum Reactor for use in AUVs similar to the REMUS. The goal is to develop a power source for autonomous underwater vehicles that outperforms Lithium Ion Batteries and extends the REMUS mission from 3 days to 3-4 weeks.  My group is working on the Waste Management sub-system of the project. This semester has involved a lot of design work and a particularly large amount of re-design work.

Here’s some of our final parts as they are being 3D-printed and cleaned. After they are cleaned, the parts are ready to get a coating of epoxy and then they’ll be ready to integrate into our sub-system and eventually the overall system. I’ll do a complete write-up on the project and the different subsystems at the end of the term. For now, here’s a teaser.  Oh and you’ll be able to tell from the pictures but the parts for our sub-system will all be bright orange. This was just a function of what plastic was available to print with. It’ll make a loud statement at our presentation to Lincoln Labs on May 3rd.

Here is one part getting printed. This will be the lid for our purge chamber. The part is about halfway printed in this picture.

This clean station contains a chemical bath that removes the support material that the 3D printer uses to support the plastic as it cools. Removal of the support material typically takes three to four hours.

Removing the lid of the clean station, the part (here, the settling stage body) is visible but so is the chemical bath. Gloves were definitively required in this case.

The settling stage has a bizarre geometry but all these crazy features have specific, important roles in our subsystem.

Because 3D printed parts our porous, these parts need to have an epoxy coating added to them after printing. We are using them in our system as containers to hold water / waste, and they need to be watertight. We’ve tested the epoxy on some of our 3D printed prototypes of these parts and we were successful in waterproofing the prototype parts.

Hopefully, the parts will come together and we’ll be able to have the parts printed and epoxied by Friday! This has been a long semester (especially since I’m involved in a large number of project classes) and I’ll be very excited to be finished with everything once the end of May rolls around.

Pressure Vessel Endcaps

For the 2.017 robot’s pressure vessel, endcaps needed to be made. Sam, structures, had never made endcaps before so I volunteered to help out. Here are some pics from the process. It took the two of us two hours to make two endcaps. There’s still a lot to be done on the 2.017 robot. I haven’t mentioned it before but I’ll do a more thorough write-up on it soon. For now, endcaps!

Delrin stock on lathe.

Checking the clearance of the endcap into the pressure vessel tube. We made several passes (then tried to fit the tube) several times before getting it right.

We put a chamfer on the edge using a file.

Here, the first o-ring groove is added to the endcap.

I’m pictured using the parting tool to create the groove.

Both grooves are finished! An o-ring is used to make sure the fit is right.

Two grooves with only one o-ring. The final endcap will feature two o-rings.

Parting the endcap off the piece of stock, creating a shoulder on the endcap.

Sam is holding the finished endcaps.

Finished endcaps! Later, I’ll add holes for our waterproof connectors and some mounting holes for the internal pressure vessel structure. The internal structure will support the electronics and some small batteries (not our main batteries).

FSAE Computer Bank

From Saturday 4/20/2013: This Saturday was a long Saturday, spent coding in matlab at the FSAE shop with Shavi (left) and Sammy (right).

Engine Operation Points and Performance

Me, pictured in front of modified Volvo B5254 engine with Dynamometer (blue machine box, behind engine) and a variety of different testing apparatuses (everywhere). MIT Sloan Automotive Laboratory.

Today was another well-spent afternoon hanging out in the Sloan Automotive Lab! Our class split into two groups and my group spent the afternoon collecting data for the engine operation lab. The lab had two components. The first half of the lab was focused on measuring the MAP, NIMEP, Fuel Pressure, COV of GIMEP, and exhaust temperature of the engine when different spark timings were used. The Air-Fuel Ratio was held constant at stoichiometric for these tests. The dry exhaust gas was collected and the concentration of NOx, CO, HC, CO2 in the gas was measured. The second half of the lab varied the Air-Fuel Ratio and the spark timing was constant (the Max Brake Torque spark timing was used). The same measurements were collected. All in all, it was a cool experience and I welcomed the chance to spend the afternoon in the Sloan Automotive Lab. It’s a bummer 2.61 (Internal Combustion Engines) only had two labs! I still need to process all the data and do a lab write-up. I’ll post some scans  of the data and the resulting write-up later.

The Volvo engine on its mount with test apparatus and dynamometer.

The engine controls and data readouts are kept outside of the room with the engine, engine mount and test apparatuses. A shatterproof window allowed visual access to the engine and the test apparatuses while providing protection to the engine operators.

Inside of engine room, on the left is the drying and collection apparatus for the exhaust gas. This exhaust gas is collected so that the concentration of NOx, CO, HC, and CO2 are measured. CO, HC, and CO2 values are displayed on the screen.

The exhaust gas from the engine is collected so that the concentration of NOx, CO, HC, and CO2 are measured. CO, HC, and CO2 values are displayed on the screen.

The red box shows the collection and drying setup. The purple box shows the readout screen.

The dynamometer for the operation of the engine. The dynamometer measures the power outputted by the motor. The dynamometer is part of the control loop for the motor operation that ensure the motor operates at a specified condition so that the motor’s behaviors can be studied at that operation point.

The controls for the engine. The throttle controls are highlighted in the red box and the other controls are in the purple box. The readout screens are for various temperature and pressure sensors.

The lambda meter measures the air-to-fuel ratio of the engine. At stoichiometric, this ratio is 1 and the value of lambda is 1.

Most of the sensors output directly to the computers. One computer operates the engine (communicating with the dynamometer and the engine control unit) while the other gathers data on engine operation.

And that’s it! When I finish the lab report I’ll post the data and some of the conclusions I reached.

Internal Combustion Engine

This semester I’ve been taking an Internal Combustion Engines course that has a hands-on lab component. Tomorrow is the last lab of the semester.

The class had a total of two labs and I really enjoyed the first lab. The first lab was therapeutic! We were given the tools to take apart a 4.2 L Ford engine from a Ford Focus. We were also given the engine and told to go at it. The purpose of the dis-assembly lab was to give us an intuition of the scale of parts inside the engine and to give us an opportunity to see how the length, thickness and area of different engine components directly affected the overall performance of the engine. We measured the different engine parts and then ran calculations to understand how the size of the different engine parts affected engine performance at different loads.

For tomorrow’s lab, we want to study the engine in operation at several different operating points. To do this, we will vary the timing of the spark ignition (within +/- 20 dgrees of the timing for max brake torque) and the throttle position.

To characteristic the engine’s performance, we will take data on

… the net indicated specific fuel consumption

… coefficient of variation in the Gross indicated mean effective pressure

… NOx, ppm and the emission index

… HC, ppmCl and emission index

… CO, as a mole fraction and emission index

… CO2, as a mole fraction and emission index

I’ll try to take some pictures of the cylinder we’re working with – we’re using a modified five-cylinder Volvo B5254 engine. The modification is that we’re running the test with four of the five cylinders removed so that we can operate the engine at part load.

Wish me luck!

- J.

Blue Lobster Bowl Presentation

BLB Presentation March 2013 v3

Whale Tag

From New York Times: http://green.blogs.nytimes.com/2012/08/20/a-whale-a-tag-a-mission/

 

 

 

 

Jake Levenson, Marine Biologist, asked David and I to help him produce two new whale tags for his trip to the Caribbean French Territories. Jake left this morning – David and I met him with the new tags at Logan at 4:00am – but here’s a picture of the two new tags with a professionally-manufactured tag for comparison. The manufactured tag is green and our tags are yellow.