LTDS Engine for power generation - C. LLoyd

Source

A low temperature differential Stirling engine for power generation
Thesis - Caleb Lloyd, University of Canterbury, New Zealand
2009

Characteristics

Type:    gamma, controled/powered rotating displacer
Theoretical power:  500W with Th=90°C and Tc=20°C and working gas (air) at 10bar
Measured power:    na
Beale:  expected value 0.002 to 0.008

Vexpansion = 5000 cm3
Vcompression = 83000 cm3
Heater:    43200 cm3 * ?%, wetted area = 8.1m2
Cooler:    43200 cm3 * ?%, wetted area = 8.1m2
Regenerator:   modular, 43200 cm3 * x%

Illustrations

Photo credit: Electrical and Computer Engineering - University of Canterbury

Details

www.elec.canterbury.ac.nz -  [ pdf ]

This Gamma-type piston engine has not been tested yet. The geometry is not usual, mainly the displacer chamber, with an rotating displacer. The engine is supposed to oscillate at 2 Hz with working gas at 10bar pressure.

The piston is made of aluminum, it is constructed with separate pieces bolted together for cost reduction reasons. The seals are silicone rubber O-rings, lubricated with silicone grease.

The displacer is oscillating in a rotation movement, it is actuated by a motor to be able to vary velocity parameters. Once the optimal motion will be determined, the electrical actuation will be replaced by an appropriate mechanical linkage. The displacer is made of expanded polyurethane foam and an aluminum framework.

Heater and cooler are base on fin-tube structures. Fins are made of aluminum, and the tubes are made of copper

The regenerator is a modular element that can be pulled out and changed easily. Regenerator and heat exchangers have the same dimensions. Six different material have been studied for the regenerator. The best results are obtained with mild steel wool.

Material	Fiber diameter  [micrometers]	Density [g/cc]	Cp [J/kg°C]	Regenerator  effectiveness [%]	Indicate  effectiveness [%] (*)
Mild steel wool	30	7.8	437	94	8.8
Stainless steel wool	40	7.8	510	79	6.6
Stainless steel mesh	100	7.8	510	85	5.3
Silica wool	7	2.2	840	89	6.9
Glass fiber	1	2.7	670	84	4.7
Kao wool	7	2.5	1070	91	2.22

(*) tested in a small air test engine