MEAM.Design : MEAM247-10A-P3

MEAM.Design - MEAM 247 - P3: Stirling

Schedule

You Realize Your Predicament

Stranded out in the woods, you are desperately searching for a source of relatively high-speed, low-torque power. Why? I have no idea.

Digging through your rucksack, you come across a small custom-machined tabletop Stirling engine. What a find! Remembering that Stirling engines operate on an external heat source, you decide to build a fire. Fortunately, you are good at this.

Now, you start thinking about the output requirements of your engine, and come to realize that you really want to create a simulation of the engine. Disregarding the improbability of these events, you again go digging through your rucksack, and find a laptop with a fully-charged battery and an installation of Matlab. Another amazing find!

And now the fun begins...

You Find Some Friends

Stumbling around thinking about the simulation you're going to develop, you realize that you're going to need some help. Fortunately, you find that the woods are full of people you know. In addition, you realize that approximately 46 percent of the people in the woods have personally built a Stirling engine before.

Now, you need to find two people that you haven't worked with before (make sure that either one or two of the three team members have built a Stirling engine), and add your names here before 6:00 p.m. on Wednesday, April 7th. Those not listed on the page by the deadline will be randomly assigned.

You Explain How it Works

Walking around with your new team of friends, you find a nice log next to a babbling brook. You decide to sit down as a team to prepare a brief (2-page maximum) explanation of how your Stirling engine works. You decide to use a few graphics, including a well-labeled P-V diagram and an illustration of the engine. You also decide to include explanations of both the thermodynamics and the mechanical dynamics of this fascinating system. Somehow, you manage to deliver this to the slot under the door to Towne 220 by 5:00 p.m.

You Create Your Simulation

As night is approaching, you build a fire (remember, you're good at that), and decide to evaluate the engine to determine the important parameters (input, output, variables, constants, etc.).

After a good night's rest, you boot up your computer to create a dynamic model of your Stirling engine. You decide that the top-level script must have the following well-labeled sections:

• An explanation of your simulation
• An area to set the input parameters (hot and cold temperatures, etc.)
• A block of constant definitions (link lengths, masses, etc.)

After some discussion with your team of friends, you decide that the simulation should produce the following:

• graphs of both the P-V and T-s diagrams for the engine
• an estimate of the output shaft speed (in RPM)

Fortunately, you recall that the nominal dimensions for a standard Stirling engine can be found here.

If you'd like to share thoughts on this project with other wanderers in the woods, you can do so here.

You Validate Your Model

A few days have gone by, and you're getting hungry, but you've been so wrapped up in Matlab (now your favorite software program), that it doesn't matter. Now that you've made your first model of the engine, it is time to see how accurate it is and make improvements where necessary. Walking around your campsite, you stumble across an instrumented Stirling engine. This engine has a full suite of sensors, including thermocouples in the hot and cold ends of the air chamber, an absolute pressure sensor in the mounting block, and a magnetic encoder on the output shaft. All of the sensors are connected to a data acquisition device so that you can record the values while running the engine. Convenient, to say the least.

Unfortunately, you're not the only one to find this, and the owner has asked you to sign up for a 20-minute time slot to work with his engine (click here to add your team to the schedule).

Testing Procedure & Data Format

Once you finishing testing, you take your data back to your campsite, where you decide (very wisely, I might add) to divide the data into two sets. You use one of the sets to compare against your simulation results, and make improvements where necessary. You then use the remaining data to validate your model.

You Complete Your Mission

Finally, you remember why you needed this engine in the first place, but there is one final obstacle to overcome. You must send an email to medesign@seas.upenn.edu with your (well-commented) simulation code and all of your testing data. You decide to title the email as "247-P3-T##-code", where ## is your team number. Then you go do whatever it was that you were up to in the first place...