I was recently asked to post some pictures in the gallery of a thermo-lag engine design which I constructed in 2003. The still pictures to not really do justice to the performance that this pulse tube design achieves so I have published a video on Youtube.
http://youtu.be/OLWmAE0FZJg
I hope it is of interest.
Geoff V
Thermo-lag pulse tube design
Re: Thermo-lag pulse tube design
Geoff, very good, given me some ideas, my motor is stuffed with steel wool, and would barely reach 1000rpm.
In your testing, it would be interesting to see if there was any difference when running with the prop if you diverted the cooling air away from the engine, as it is in the vidio the motor is receiving extra cooling, more and more as the motor speeds up. Perhaps a little electric motor with a variable load, and an ammeter.
Is the internal tube bit sealed as in an ordenary displacer ? Ian S C
In your testing, it would be interesting to see if there was any difference when running with the prop if you diverted the cooling air away from the engine, as it is in the vidio the motor is receiving extra cooling, more and more as the motor speeds up. Perhaps a little electric motor with a variable load, and an ammeter.
Is the internal tube bit sealed as in an ordenary displacer ? Ian S C
Re: Thermo-lag pulse tube design
Ian
The cooler/cylinder head gets quite hot, very quickly, so if anything I would wish to duct the air over the cooler, originally it had a water jacket which I removed as the engine is now just for show.
The inner tube is filled with stainless steel wool and is open at the heater end, allowing a reverse flow.
Regarding output, I have measured the the power comsumed by the prop using an electric motor and a laboratory DC power supply.
Geoff V
The cooler/cylinder head gets quite hot, very quickly, so if anything I would wish to duct the air over the cooler, originally it had a water jacket which I removed as the engine is now just for show.
The inner tube is filled with stainless steel wool and is open at the heater end, allowing a reverse flow.
Regarding output, I have measured the the power comsumed by the prop using an electric motor and a laboratory DC power supply.
Geoff V
Re: Thermo-lag pulse tube design
Very nice! So what is the estimated power?
Re: Thermo-lag pulse tube design
Dear Derwood
I was reluctant to disclose the power as it is only one point on the power curve and I really should have built a small Prony brake to get the big picture. However as I am busy with another engine and unlikely to find the time, I measure 2.34watts at 1400rpm, unpressurised, heater temperature not known but from memory just red. I also have a 90deg vee twin version of this engine which was designed to be pressurised with a built in starter/generator. The problem I had was insufficient torque to turn the engine over compression so I had to start it depressurised but then found it very difficult to raise the pressure slowly enough to keep it running. However I was left with the impression that it responded to pressurisation so I may have another play with it next winter.
Geoff V
I was reluctant to disclose the power as it is only one point on the power curve and I really should have built a small Prony brake to get the big picture. However as I am busy with another engine and unlikely to find the time, I measure 2.34watts at 1400rpm, unpressurised, heater temperature not known but from memory just red. I also have a 90deg vee twin version of this engine which was designed to be pressurised with a built in starter/generator. The problem I had was insufficient torque to turn the engine over compression so I had to start it depressurised but then found it very difficult to raise the pressure slowly enough to keep it running. However I was left with the impression that it responded to pressurisation so I may have another play with it next winter.
Geoff V