Stirling engine for running a car alternator

[smartmachine]

Hellos!..... I'm not new to stirling engines but gonna make a working Gamma type, as a beginner. I need to ask the following things:

1. Purpose: I need to run a car alternator (35 amp, 6 poles), or a bigger one (110 amp, may be it's an 8 poles) taken out
from a large vehicle e.g a bus or a truck, to get 1200 rpm for 50 Hz from the said alternator, running it with the
stirling engine through the belt pulley arrangement (bigger alternator is wanted to use/run to get more amperes as per
application).

2. What sizes the Displacer cylinder and the Power cylinder should I use for the purpose. I know this already that the Displacer cylinder should be ideally 1.5 times or 33% larger than the power piston cylinder, but I need powerful piston strokes for the purpose mentioned above, I assume.

3. I also assume that, for powerful power piston strokes, a Displacer should be used at least 6 times larger than the power piston size (and hence the same for their respective Cylinder sizes), especially for the swept volume of air in the Displacer cylinder. Am I correct in this?

4. For cold part of the stirling engine, I would use some coke tin can filled with water.

5. Very important, how should I seal the power piston and the Displacer shaft for possible air/gas leakage from there.

6. How should I calculate the Displacer stroke (the distance that Displacer would travel as per the Cylinder size) and the
power piston stroke for making the respective crank sizes for them on the crankshaft.

7. Which working gas should I use, air or Helium?


Many thanks in advance and ........ Regards!

smartmachine.

[theropod2]

Do you have any idea how much power you're gonna need to turn that alternator? I live off grid and use a large frame alternator to charge my batteries when the sun fails and there is no wind. To get that sort of power you will need about a 5 HP engine.

Now, if you really think a Stirling is the way to go here I'd suggest a dual disc axial flux alternator using rare earth magnets and individually rectify each coil and combine the outputs.

In no case would I consider this a beginners project.

R

[Ian S C]

To power a 35 amp alternator,(490W) you must have at least double that power, and able to turn it over at 2500 to 3000rpm, its got to run at least 1200 rpm to strike the alternator and start charging, 3 to 4hp would do it. The Philips generator set was a 200w unit (think it could manage about .5hp), An un pressurised motor will be quite big, you won't need any coke cans(except to keep you cool) I seem to remember the power working out a 1watt per cc, so for 4hp you would need 3000cc minimum, proberbly better to go to a motor of about 1000cc, pressurised to quite a high pressure. The 110 amp alternator would require a proportionatly larger motor. Ian S C

[smartmachine]

Thank you very much theropod2 & Ian, I actually wanted to know also, that what I give this configuration of a Stirling engine Gamma type) in my post, what Hp would it be, basically? and How much power in watts would it give up, with this given configuration in my post. If I use strong cranks and crankshaft and with larger Displacer set, wouldn't it do it the nearest? I wanted to actually Tap out the 120 VAC also from the car alternator, thereby stepping it up to 220 VAC for use of House hold fans n lights etc. I just want to "Bypass" the "inverter channel" and use the 220 VAC. That's it! Battery charging through this alternator is a secondary issue.


Thanks.

[smartmachine]

My question is: How should I seal the power piston and the Displacer shaft for possible air/gas leakage from there. Plz provide helpful info in this.

Also plz confirm that, there are many stirling engine plans on the internet, including the Working ones (especially for Stirling engine fans, either heavy or small designs), do they all really work indeed (especially the Heavy Stirling engine fan designs)? so that I or anyone could make them on part.


Thanks in advance.
.
.
smartmachine.

[Ian S C]

First, get a book on Stirling Engines, ie "The Stirling Engine Manual" vol 1 and 2, or"Modelling Stirling and Hot Air Engines" by James G. Rizzo. There are a number of other books. Read and understand(even if you know the general principals), you will find the ratios required to get an engine that runs well, then just feed it steroids, and see what happens.
You are going to need a machine shop, with a lathe a bit bigger than hobby size.
Have a look on google for Stirling Technology,inc. ST5 engine, you may find a down load. This 5hp motor was designed for use in Bangladesh, to run on rice husks. Ian S C

[smartmachine]

Thank you very much Mr. Ian S C for great n kind help of yours. Hope these references wl guide very better!

[rustybarrel]

I dont know but correct me if i am wrong. To charge a battery you need to have voltage greater than that supplied by battery. But the current has no limit. If the current is low it will take long time to charge and if current is high it will take less time. Only thing to remember is the total power supplied (volt x current) is more than internal losse from the battery. So if you have to charge a standby battery you can have a small engine say 50 or 100 watt with dynamo producing about 13 to 14 volts. But it will take very long time to charge. This method is called trickle charge.
On the other hand if the battery is providing power while it is being charged you will need power which is more than its load.
It will be easier to construct the engine for charging a standby battery than to charge a running battery.
thanks

[Ian S C]

You have it near enough, the actual voltage will be nearer to 17 V at a peak, and the maximum charge is regulated, not sure what at, maybe 8 watts , but 2 to 3 watts would be useful.
A motor that would make quite a good charger is the one from a (not sure what to call it), stick mixer, thing for mixing food in the kitchen, they have a 200v and up to 500watt DC motor, I won one, and use it on my Ross Yoke ALPHA motor, it generates up to about 20v with no load. Usually I run a 9v radio, and the little computor fan for the cooling system, with the motor running at 600 to 700rpm. The motor is about 35 mm dia X 60 mm long. Another motor that is worth looking for/at, is the one in a tread-mill. There are many motors out there, pick a motor with the lowest revs, and voltage.
For most generators the power source(your Stirling Engine) needs to be about double what you expect to get out. DC motors are a little less complicated to set up than car alternators, you don't need a 12v battery to get the ordenary generator(motor) producing power, although you can start the alternator with two little 9v batteries, or even two 6v lanten batteries.
There is a modification that can be done to a car alternator;Take the armature out,and disassemble the rotor, you'll need a good high power press, you need some powerful magnets to fit over the shaft, and inside the fingers of the armature, reassemble. You then have the option of leaving the field coils as is, or rewinding them for a different voltage (more turns higher voltage, lower amps = same watts), or make it single phase. Ian S C

[nate]

Windblue (http://www.windbluepower.com/) makes a permanent magnet alternator that produces 12V at low speeds that's not too expensive. They also make a replacement armature for DELCO alternators. I haven't bought one of these, but I have a friend running one on a water wheel. They are supposed to be a whole lot more effiecent that a regular automobile alternator. They also make an AC tap (not sure what the volatage is but I assume that it is low). Nathan.

[Ian S C]

There is another, the New Zealand designed and made, Fisher & Paykel washing machine motor, this is much sort after as an alternator, and there is a company in NZ making small hydro-electric plants, producing about 1kw for a single stage unit, there is quite a bit on google about these motors, and how to convert them, and the information comes from the manufacturers. Much more efficient than your friends delco unit.
Ian S C