Stirling MotorDisplacer Piston Controller Project Sponser; EcoGen Contact; Alan Holsapple
The Technology• EcoGen is developing a novel Stirling Motor based on a patent pending technology which promises to increase the efficiency of the motor relative to current production engines while decreasing the manufacturing costs dramatically.
Stirling Engines • External combustion, flexible fuel source • Closed cycle, helium or H2 working gasRobert Stirling patented this hot air • High thermal efficiencyengine with economizer (regenerator)in the early 19th century. Historically, • Low noise and vibrationcheap IC engines have displaced nearlyall engine applications, however due • Low maintainenceto it’s high efficiency, the Stirling is • Low emissionsmaking a comeback. • High cost of manufacturingThe free piston Stirling developed byInfinia Corp at right is being used form-CHP applications, and others arebeing developed for high efficiencypower generation applications .The high cost of manufacturing is akey inhibitor to the mass scalecommercialization of the Stirlingengine.
EcoGen’s Motor Description
Induction Control Coil• Circumferential orientation at cylinder wall• PM’s embedded in Displacer• Current; pos / neg (act as motor / generator)• Simple, low cost materials
Displacer X-Section • Graphalloy bearings • Haxagonal alignment • Stacked Perf-plate or brazed tube design • Mock regenerator with porous material
Control Algorithm• Cold Start / ramp frequency• Run / bracket frequency• Retard or advance phase angle• Shut down cycle, soak back protection
PLC and Power Electronics• Power requirements• Feedback signal analysis• PWM vs FM or other current control• The primary function of the controller is to align the frequency of the displacer relative to the power piston
Project Goals• Prototype hardware configuration for displacer piston controller• Preliminary algorithm for prototype motor control• Spring size / rate down select• Test data, results and report