[Gasification] OT - two stroke engine

[Bob Stuart]

On 2-Jun-07, at 6:21 PM, Peter Singfield wrote:

> At 12:56 PM 6/2/2007 -0600, Bob Stuart wrote:
>>
>> How is this communicated to the gas?  Does it not still see a moving
>> piston changing its volume?  How could a pressurized gas expand
>> against a piston and not do work?  It would either accelerate a crank
>> and flywheel or make the piston into a projectile.  Neglecting
>> friction, it would put just enough into the flywheel to re-compress
>> itself to the same temperature.
>>
>
> Yes -- except one side is hotter than the other.

It seems to me that both sides will stabilize around the temperature  
of the working fluid as it averages in that location, and you will  
always have to add power to overcome friction. I've never heard of a  
heat engine that does not exploit a difference in temperature.  This  
scheme seems to violate the second law of thermodynamics.  Heat is a  
lower  form of energy than momentum or electricity, so while they can  
produce heat directly at 100% efficiency, the exchange can't be  
reversed directly, and must be approached by interfering with the  
mixing of hot and cold.  Where only a small temperature difference is  
available, as in the ocean thermal schemes, the efficiency is  
extremely low.

Best,
Bob

>
> I see your point about cooling the cylinder rather than insulating  
> it --
> thus achieving a higher Delta-T  -- and that certainly would  
> increase the
> total power being extracted -- but not as "work" -- read on ---
>
> Now -- to keep on with this mental twisting exercise.
>
> It would appear that one should avoid to much compressing.
>
> Let's name some parts and areas -- real spur of this moment stuff.
>
> The coiled tube heat exchanger = "boiler"
>
> The piston/cylinder area = "engine"
>
> How about if we consider lowering the compression ratio  
> substantially??
>
> Just for discussion -- 2:1
>
> So the 385 CC engine would transfer it's entire volume into a 385  
> cc "Boiler"
>
> Thus reducing 770 CC to 385 CC
>
> So -- what would happen now??
>
> The boiler would operate near bath temperature -- call that 400 F
>
> The cylinder would stabilize at "expanded" temperature.
>
> We would be expanding the boiler "charge" from 385 CC to 770 CC --  
> when
> piston travels from top dead center to bottom.
>
> Now -- can we find the other parameters??
>
> Using steam tables.
>
> If we start this cycle with the piston top dead center -- we have  
> 385 CC of
> steam heated to 400 F in the boiler.
>
> Ah-ha -- but at what pressure??
>
> Well -- basically -- at any pressure we decide to load it up to --
>
> These little diesels run happily at 20 to 1 -- so -- rounding it  
> out -- 300
> PSI
>
> Steam of 300 PSI 400 F -- is past "saturation" -- oops -- we must  
> not have
> any of that at all!!
>
> So -- instead of 300 -- we make it 200 psi (abs by the way)
>
> Or -- instead of 400 F we run that liquid metal bath at 600F -- but  
> still
> at 300 PSI
>
> I like the second option better -- more "push" more power.
>
> Steam chart stuff ---
>
> One pound of water at 300 PSI and 600F is well "superheated"
>
> Volume/density of steam is 1.0723 ft cubed.
>
> Total "heat" per pound of steam in this state = 1351.1 btu
>
> OK -- now piston backs off -- volume doubles.
>
> OK -- now we have 2.145 feet cubed of steam --
>
> Question -- what will be the new "temperature" and pressure???
>
> Scanning the steam tables:
>
> Well -- 220 psi at 400 F --- and a btu value of 1206.5
>
> 1351.1 - 1206.5 = 144.6 btu "difference"
>
> OK Bob -- if my cylinder is "insulated" -- pray tell -- where did  
> the 144.6
> btu go??
>
> Would you ever believe it went into "work"??
>
> Now -- I did this example totally at random -- one could spend a  
> little
> time and find better parameters -- different operating pressure --
> temperature - -and compression ratios.
>
> But -- using this random choice example ---
>
> The little engine is doing one "work cycle per revolution.
>
> The little engine is turning at 1000 rpm
>
> Each work cycle involves volume of steam expanded of 385 CC =  
> 0.0136 ft
> cubed --
>
> times 1000 = 13.6 btu
>
> 13.6 btu/min = 0.320
>
> Now some believe that is simply disappearing into a proverbial  
> black hole
> out there.
>
> I "theorize" that can be extracted as power.
>
> Steam engine operating for more than 200 years -- also support that  
> "theory"
>
> OK - -their will be friction losses -- some heat losses (but not  
> much!!) --
> so call it 1/4 HP!!
>
> Which -- some of you might recall -- was my original "gut" estimate.
>
> OK -- tell me again why this can't work -- anyone??
>
> Certainly -- the top end of a diesel engine without valves or valve  
> train
> -- can operate at 400 F!!
>
> Take that you stirlings!!
>
> Hmm -- maybe 3 to 1 compression ratio???
>
> Hmm -- maybe .5 to one ????
>
> I'll do more scanning later -- maybe ---
>
>
> Peter/Belize