Alicea-Román, Jean C.
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Publication Study of volume variations in alpha stirling engine design via a discrete control volume approach(2014) Alicea-Román, Jean C.; Ruiz, Orlando E.; College of Engineering; Baiges, Iván J.; Dooner, David B.; Department of Mechanical Engineering; Carlo, Hector J.New demand for cleaner and low cost energy production are factors that have increased interest in the Stirling engine as a plausible alternative to internal combustion engines. The Stirling engine is based on the principles of having a machine work within a temperature differential and internal thermal regeneration. The regenerator is a waste heat recovery device that improves the thermal efficiency of the cycle. Theory shows that the Ideal Stirling cycle efficiency is the same found for the Carnot cycle efficiency. However, the use of Ideal cycle and First Order analysis methods tend to grossly over predict performance parameters. This often comes as a result of inadequate assumptions and ignoring loss terms in the system to make simplifications in the analysis. In practice, the design of Stirling engines is difficult because of the complex thermal and mechanical processes that are involved. The Second Order method is found to be useful in engine design optimization, since the analysis assumes that all of the energy losses are decoupled. The individual loss mechanisms can be conveniently identified and quantified. This analysis allows the engine performance to be estimated in a more realistic manner by subtracting the losses to the idealized performance parameters in a simple and efficient approach. Such analysis model, if implemented with enough accuracy, could properly evaluate design changes required for developing technology to make the Stirling engine more reliable, sustainable and efficient. More efficient heat transfer and adequate kinematic mechanisms for performing cycle work are two major areas that can be improved. This research project considers the potential for improving the thermodynamic efficiency of the Stirling engine by evaluating alternative piston motions that substantially deviate from sinusoidal. The present study further expands on previous work in this area by incorporating the Second Order losses. Following in this effort, the studies are based on arbitrary functions that describe the piston motion and parametric studies of the cylinder compartments. Unfavorable results were obtained in the motion studies for the new arbitrary functions. The lower performance was related to larger gas velocities that significantly increased the power losses. However, an optimal configuration was found for cylinder compartment while maintaining the sinusoidal motion.