Introduction

In this unit of the Science and Engineering course, we are making a device that uses energy transformation to make a difference in society. This can be as simple as building an electric fan and converting chemical potential energy into kinetic energy. However, I do not believe it is cool enough. My goal is to create something more complex, amazing, and worthwhile. I currently have three designs: a sterling engine, an electric motor, and a thermoacoustic engine. I’ll describe my potential designs and evaluate them based on their visual appeal, challenge, and usefulness level.

Potential Designs

Sterling Engine

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The Stirling engine converts thermal energy into mechanical/kinetic energy by establishing a cycle of a fixed mass of gas that is heated and expanded, then cooled and compressed, using the temperature difference between its hot and cold ends. In a Stirling engine, the coil of steel wool placed inside the soda can is referred to as a displacer, and the higher soda can is referred to as a piston that connects to the crank shift. The engine begins with a displacer at the top of the can and a piston halfway down the can. When the can is heated, the air pressure inside the can rises in comparison to the outside air pressure, penetrating the displacer and pushing the piston up. The piston propels the crankshaft and fan, causing them to spin. The flywheel momentum builds up as the fan spins, accelerating the rotation. The displacer is also connected to the crankshaft, but at a 90° angle with the piston connection. As a result, as the piston rises, the flywheel momentum lowers the displacer and vice versa. When the displacer is pushed downward, the gas inside the can rises to the top and cools, and the air pressure falls in comparison to the outside air pressure, causing the piston to fall to the bottom. The flywheel momentum then propels the piston to the halfway point and the displacer to the top of the cycle, and the cycle begins again. As long as the burner keeps heating the gas inside the soda can, the Stirling engine will run for a long time.

The Stirling engine is what I believed is the most challenging one out of my three potential designs. It requires a wide range of materials/apparatus such as steel wool, a plastic pipe, a crankshaft, an alcohol burner, a wooden setup, a hot glue gun, and a drilling machine. It requires high craftsmanship and investment (time & effort), which I believe is difficult to finish in two weeks. However, I really like the way the Stirling engine functions, and the process of energy transformation in terms of this design.

Electric Motor

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An electric motor is a piece of machinery that converts electrical energy into mechanical energy. Magnetism is important in this energy transformation process. When an electrical current flows through the coil on the bottom, it can act like a magnet, which is known as an electromagnet. Torque is a rotational force torque that can be generated by using the forces of electricity and magnetism—the attraction and repulsion exhibited by magnets, as seen in the video. With the help of a battery, the wire coil was transformed into an electromagnet, which repelled the magnets attached to the bottle, resulting in a torque that spun the bottle and the fan. The rotation will last until the battery runs out.

The electric motor is what I believed is the smartest and easiest one out of my three potential designs. It requires fewer materials and is less dangerous since it doesn’t include the use of fire. The main focus is on the circuits and the magnets, which I’m quite interested in. However, I think the design is too simple and tiny and is not that attractive to audiences.

Thermoacoustic Engine

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This thermo-acoustic Stirling engine has a single piston instead of the two found in more traditional Stirling engines. Stirling engines use a power piston and a second piston to move air between the hot and cold parts of the engine (known as a displacer piston). Instead of a displacer piston, this thermo-acoustic engine uses a traveling sound wave to do the work of a displacement piston. A small alcohol burner included with the engine provides heat.

The thermoacoustic engine is what I believed is the best one out of the three potential designs. It uses the mechanism of the Stirling engine and is easier because it contains only one piston instead of two. Therefore, I decided to create a thermoacoustic engine for my two-week project.