Proceedings of the 2017 ASEE Annual Conference & Exposition, Columbus, OH, June 24-28, 2017
Hands-on projects are launch pads for sparking student interest. Specifically, design-build-test (DBT) projects can be effective tools for boosting students’ confidence in their ability to apply theoretical knowledge to practical engineering. Recognizing the need for relating the theoretical aspects of thermodynamics to its application, an air cannon design-build-test project was envisioned and implemented.
Air cannons can be simple and inexpensive to construct, while offering a robust platform to explore thermodynamics, heat transfer, and fluid mechanics concepts. At the same time, the ability to launch projectiles from the cannons carries an obvious appeal for many students. An air cannon design project was integrated towards the beginning of a year-long thermal-fluid sciences course series. The primary aim of the project was for student teams to study how air cannons function and subsequently design a prototype that fits “customer” specifications. Each team constructed their cannons using PVC piping to launch acetal plastic projectiles. Students were additionally required to design a functional release valve mechanism to trigger the projectile launch. To aid in evaluation of their designs, students were introduced to a numerical-analytical modeling approach to explain air cannon behavior using principles of linear momentum conservation and ideal gas thermodynamics theory. Among other metrics, the performance of each student team was assessed based on (1) the ability of the custom trigger mechanism to fire the cannon over a range of initial reservoir pressures, (2) a thoughtful comparison among experimentally-measured and model-predicted muzzle velocities, and (3) documentation of the results of cannon design, realization, and operation.
This paper discusses the implementation and relevant outcomes of the project. Based on student feedback, the project was well-received and anchored the often abstract thermal-fluid sciences concepts taught. The project also highlighted the challenges of applying theoretical equations to real-world problems and the vital need for experiments to improve accuracy of theoretical models. Exposure to this iterative approach to design emphasizes the practical aspects of engineering challenges. Overall, the project served its primary purpose of engaging students with thermodynamics concepts. With minor modifications in implementation, the project can appeal to students with a broader academic focus and experience.
Haas, F. M., Dow, N. W., Merrill, T., & Bakrania, S. (2017, June), Cannons to Spark Thermal-Fluid Canons Paper presented at 2017 ASEE Annual Conference & Exposition, Columbus, Ohio. https://peer.asee.org/28007.