As said in my previous blog post, this year my associate James Thomson and I will be testing whether the pressure produced from dry ice sublimation could be a way to generate energy for q Mars exploration through a pressure engine. We are testing this by putting dry ice (solid CO2) into our pressure vessel (Arksen Bead Seater) and letting it fully sublimate and then running turbine of sorts. Our turbine was originally supposed to be a pneumatic wrench as seen on the right.
However when tested it only had 120 RPM and generated 4 volts of electricity with our DC motor generator. We decided then to get a pneumatic tool that had much higher RPM to generate more electricity. The tool we selected was an angle die grinder (image to the left that was rated to go at 20,000 RPM. As a test to see how the tool would operate under our test conditions, we used an air compressor to pressurize your tank to 90 psi, the max pressure the turbine operates under, and recorded how long the turbine would run for. The turbine ran for a total of 34 seconds at a very noticeably higher speed than our previous turbine. We expect with the faster speed we should generate much more electricity.
We’ve been researching various gas and fluid laws relevant to our project, including the Ideal Gas Law, the combined gas law, and Bernoulli’s principle. Even in their (at first glance) cryptic forms, these formulae make numerous assumptions about gasses, such as that they are composed of non-interacting massless particles, which is only ever an approximation of the messiness of the real world. We’ll have to take many of these laws into account when deciding various parameters for our engine, such as the range of amounts of dry ice we’ll use and how much pressure we should expect after the gas flows through a tube. Much calculation is still required before we can apply these laws to a physical engine.
This year my associate James Thomson and I will be testing whether the pressure produced from dry ice sublimation could be a way to generate energy for Mars exploration through a pressure engine. As many people know, partly in thanks to the hit motion picture by 20th Century Fox “The Martian”, Mars that is our neighbor planet in the solar system, but what people may not know is that at Mars’s polar caps there is tons of dry ice. One glacier at the south pole has an equivalent volume of dry ice as Lake Superior, and if you have ever seen a dry ice bomb, it can generate extreme pressures and room temperature in a closed container. That pressure we hypothesized could be used to run and engine, but what could we use to get practice with an engine using pressure? A model Steam Engine! Yes, a steam engine like the ones you see in old 1800’s pictures but on a smaller scale (You sometimes have to step into the past to help build the future).
We had borrowed a model steam engine from the Chemistry teacher Mr. Tuckey and planned to test it out by saturating a paper towel with 95% ethanol to boil water (we are not to dry ice yet) to push a piston, and spin a flywheel which would spin a DC motor that doubled as a generator, and measure electricity with a multimeter. Then again, everything doesn’t always go to plan! When we lit the towel and the water started boiling, we noticed that there was a pressure leak before it got to the piston and we were not able to get the flywheel turning, but on the bright side, enough pressure was built up to use the steam whistle :). But failure is a part of science!