Development and Integration of an Advanced Stirling Convertor Linear Alternator Model for a Tool Simulating Convertor Performance and Creating Phasor Diagrams

Abstract

A simple model of the Advanced Stirling Convertor's (ASC) linear alternator and an AC bus controller has been developed and combined with a previously developed thermodynamic model of the convertor for a more complete simulation and analysis of the system performance. The model was developed using Sage, a 1-D thermodynamic modeling program that now includes electro-magnetic components. The convertor, consisting of a free-piston Stirling engine combined with a linear alternator, has sufficiently sinusoidal steady-state behavior to allow for phasor analysis of the forces and voltages acting in the system. A MATLAB graphical user interface (GUI) has been developed to interface with the Sage software for simplified use of the ASC model, calculation of forces, and automated creation of phasor diagrams. The GUI allows the user to vary convertor parameters while fixing different input or output parameters and observe the effect on the phasor diagrams or system performance. The new ASC model and GUI help create a better understanding of the relationship between the electrical component voltages and mechanical forces. This allows better insight into the overall convertor dynamics and performance. NomenclatureC f = alternator motor constant (N·s/m) F = Force (N) FF = sinusoidally varying forcing function (N) I = current (A) L alt = alternator inductance (H) N = number of turns Q in_net = net heat input (W) t = time (s) R alt = alternator resistance (Ω) R1, R2 = resistances (Ω) Sage_Q in = net heat input as calculated by Sage (W) V emf = electromotive force (EMF) voltage (V) Wnet = Power (W) x = position (m) ΔV = voltage (V) Φ = magnetic flux (Wb)