If we had an engine cycle that reused(some) live steam without condensing it, what would this mean?

How would this be classified and when would the design depart from the Rankine cycle.

Also how would efficiency of the expander be classified.



Edited 1 time(s). Last edit at 04/13/2015 06:53PM by Jeremy Holmes.

See this is my problem with the forum or the club. "how dare you deviate from the rankine cycle"

Us younger people want change. look at what Einstein did simply revolutionized the science. But oh no you don't have enough experience...

My engine is designed upset the status quo but I get 0 percent support... Thank goodness for people like Tom Kimmel.

Jeremy,

The high compression Uniflow cycle uses some of the live steam when it re-compresses the residual steam left in the cylinder at the end of exhaust. The engine does work in doing this. Minus some potential heat losses to the cylinder and surroundings this energy mostly returns to the work output. Engine efficiency is aided by this insofar as the clearance space is re-compressed to inlet pressure and so there is no free expansion of the incoming charge of steam when the inlet valve opens. IE no clearance space losses.

I think that the definitions of the Rankine cycle are fairly all inclusive, given the immense history of steam engines. Departure from it's basics is pretty hard to do.

The efficiency of a steam expander is not the efficiency of the Rankine cycle itself. One could have an expander of high efficiently of say 95% operating on wet steam at a fairly low temperature. If the Rankine cycle itself had an ideal thermal efficiency of say 10%, then the overall efficiency would be 9.5%.

Some live steam is also often bled away from the working cycle after having done some work and then used in the re-generation cycle where feed water is heated. This increases Rankine cycle efficiency but the expander has to be designed for it. A feed water heater is a simple affair applicable to an automotive type of engine, where in this, the feed water is heated by the engines exhaust steam. That is also a form of re-generation.

One idea several people kicked around on the forum several years ago to greatly increase cycle efficiency was to somehow re-compress a percentage of the saturated steam going to the condenser. This turned out to be next to impossible. Wet steam is a mixture of water droplets and dry steam. The dry steam re-compresses to superheated steam while the droplets might fizzle away too slowly to maintain equilibrium. The opposite process of expanding dry steam well below the saturation line can yield good results if the motion is quick enough so that the water droplets do not form. Expanding to a steam quality of 85% was not unheard of.

Best,

Bill G.

Quote

so there is no free expansion of the incoming charge of steam when the inlet valve opens. IE no clearance space losses.

The problem I have with this is that there are thermal losses to flash steam which reduces the temp of the on-coming steam.

But what is encouraged has more in common with a hydrostatic flow, like a hydraulic motor.

When Stephens Link or Gouch Gear was used on locomotives it encouraged "free expansion" because it was more efficient."

I learned from this book -

I want to reference a very significant book that all steam enthusiasts should know about. -The Pictorial History of Steam Power- by J.T. van Riemsdijk and Kenneth Brown. 1980 Octopus Books Limited. ISBN-0-7064-0976-0- On page 56 begins a very interesting sub chapter. Called EFFICIENT USE OF STEAM. If you are lucky enough to obtain this book I highly recommend reading it from cover to cover.

I cant find my copy otherwise I would quote, moving here to TN has most of my reference stuff scattered.

Bill G, I will take some more time reading your good reply but the free expansion thing I had to point out.

Modern power plants often do just that, if i understand the question, single and double reheat cycles are the norm keeping a lot of working fluid out of the liquid state for a significant period. Also, I believe, the super critical CO2 based power generation systems target the whole cycle outside saturation and liquid states. Now let me go see how bad i stick foot in mouth this time. (it does seem to dip into the saturation curve barely, so I was incorrect)



Edited 1 time(s). Last edit at 04/13/2015 09:57PM by kdc2.

Yes modern power plants do super heat in-between turbine stages. But at the end of the day all the steam is condensed. this isn't the rule with a 4 cycle steam engine using steam(super heated) drawn off the condenser and rerouted to a compression cycle, the condenser simply has less steam to condense.

I think if a portion of the vapor state fluid can be pulled from the condenser and pressurized, gaining heat and pressure without dipping into the liquid with a net pumping efficiency greater than allowing complete condensation, it would be a real winner.

Anyone out there ever hear of compressive steam condensation? I believe it is just what you are talking about. Specifically I refer to 'the Anderson system' named after co-patentee Henry Percival Harvey Anderson. Quite a moniker, isn't it? Actually, he is listed first in the English patents and John McCallum is first listed inventor in the US patents.

A few locomotives were so fitted out some 80 odd years ago and claimed to have improved efficiency. From what I gather, the system costs and reliability didn't justify continued development.

I would suspect the gains would be even smaller on a modern steam automobile. As pressures and temperatures rise, fewer pounds of steam are needed to do the same work. Fewer pounds have less BTUs socked away as latent heat and therefore less potential savings.

See attached patents.

Regards,

Ken



Edited 1 time(s). Last edit at 04/14/2015 11:17PM by frustrated.

Condensation never happens in the working cylinder, instead the amount of super heat is reduced.

I will check out your links thanks

Jeremy,

If condensation never occurs in the cylinder, it becomes a mystery where the term "initial condensation" originated. It all depends on degree of superheat and expansion ratio. If you are running an engine on saturated steam, condensation is utterly guaranteed unless you have no cutoff whatsoever. Likewise, depending on admission conditions, it is entirely possible for superheated steam to intersect the saturation line at some point during expansion in the cylinder as pressure and temperature fall. Naturally, the entire mass won't condense, there is that latent heat of vaporization to contend with. You can see any number of steam engines with water dripping out the exhaust, obviously condensed before release to atmosphere.

Ken



Edited 1 time(s). Last edit at 04/15/2015 04:03PM by frustrated.

Ken take a look here- [flashsteam.com] See if this compares with what your pointing out.

The U-tubes used in the Anderson patent (second link) have more in common with a re-generative engine cycle.

I would consider the 4 cycle steam engine cycle is a "conservative" cycle, as steam is taken from the condenser and reheated as steam then aspired into the engine thru the intake and compression cycles. Preheated water is then injected into the compressed superheated mass at 1/3rd cutoff. Variable valve lift of the direct injection valve is used to very effectively throttle the engine. Cutoff is fixed it the particular prototype (engine) im working with.



Edited 1 time(s). Last edit at 04/15/2015 04:07PM by Jeremy Holmes.

Ken, the steam that leaves the cylinder and enters the condenser is saturated steam with no water mix.

Jeremy
You never ran a compound or triple.
Rolly

The last time I was messing around with the engine it went FOMPH FOMPH FOMPH, it was the most glorious sound Ive ever heard.

Rolly, no I have not but I think compound engines are a good design.

To answer the question in a lot of cases it yes. In theory and in most cases you would like exhaust steam to be around 225-250f. Exhaust steam is used for feed water heaters. You like feed water around 170F to keep the oxygen out any hotter and it hammers and is hard to pump. Then it can go the condenser and pull a vacuum on a low-pressure cylinder. In other cases on a ship it can go the galley for cooking as well as providing heat for the ship in the colder weather. It also can go to chillers to air condition. Many uses

Its the same school of engineering I was reading about, DA Locomotive, The marine engines are triple compound and these type of engines can be a 30% expander efficiency.

Heres an example of a feed pump drive im using on this engine.

[flashsteam.com]



I started out with 40 tooth drive and 10 tooth sprocket on the feed pump it was overdrive and was like hitting a brick wall once the pump starts to make pressure.

Now 31 tooth drive, and 114 tooth on the feed pump, now its under driven. Im shooting for pressure on the feed pump during cranking and have a soft start.



Edited 2 time(s). Last edit at 04/15/2015 06:43PM by Jeremy Holmes.

I recently finished the modification on the drive sprockets to the feed pump and engine pto. I have been adjusting the bearings and pulled the piston out the other day and I thought wow, then I thought this would make a good picture with the rings and all.

A few years back someone advised me to polish the top of the cast iron piston to reduce heat loss. I think im going to do that.

This weekend I will update.

I decided to take a picture of the piston and rings in my engine, I took many other pictures but just wanted to get this one up

Ive had a couple of times I removed the piston. Yesterday I polished the top off the piston.

Once that piston is out of there, you can roll the flywheel and it will just spin and spin... But the counterweights will fall last. I cant imagined this being wrong because the piston is heavy.

A majority of engines and pistons and rings, quadruple drag on the engine.

Once the piston is in the engine most friction drag comes from it.

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