Problem- New Conscept?

[Rolf_K]

I have been lurking on your forum for some time, much interesting information and pictures. All my tools are just sitting there now as I am not able to stand up for any length of time. But my computer and brain is still working overtime. The other day I came up with this idea and was wondering if it could possibly work.

What I am asking is, what is preventing us from keeping the cylinder(s) superheated and injection water on each power stroke (similar to diesel engine) so that no boiler would be needed; granted the engine would not look anything like we consider a normal steam engine because the cylinder(s) / boiler would be one and the same!

I did search the net to see if anyone had tired this or even though of it, before I posted.

Rolf

[bogstandard]

Rolf,

A very novel concept, and I am sure, even though you found nothing on your web search, someone has tried it sometime over the last 300 or so years. Maybe it was such a dismal failure, it was never recorded anywhere. But these things are here to challenge us, and as they say, many new inventions are not new at all, just rediscoveries of old technology that didn't work, brought into being by using new technology that would.

Fossil fuels produce their own heat in the combustion process, and is confined to the cylinder, where with a coolant jacket around the outside, temperatures can be controlled to very close tolerances, so the engine remains relatively cool.

What you would have to take into consideration is the expansion of metals and lubrication problems you would face in keeping the engine at such a high temperature, high enough to vapourise water instantly, without cooling the engine down, all the time it was running.

One way maybe to overcome it, and I do mean maybe, would be to have a very small flash steam boiler sitting on top of the engine, being fed by an engine driven water pump. The valving arrangements and their mechanical linkages would need to be worked out, and I am sure, if it was to be used with a fairly low pressure, slide valve engine, you could generate enough steam to run continuously from a very small flash boiler, and also the boiler could be insulated from the engine, to keep the engine at a much lower temperature.
Maybe a bit far away from your original concept, but one where you wouldn't have to take a degree in metallurgy to try out.

John

[Jason3]

Hi Rolf,

A colleague and I worked on exactly that idea briefly before we concluded that although it should be quite possible, it would not be economical to develop for the project we had at the time. We felt that the potential problem with the heat/lubrication issue could probably be overcome by moving the bearing surfaces away from the heat - the piston would have perhaps had a very convex top, and the heating chamber a matching concave shape, with the hot zone being at the top where the water was injected. The bore would have been cooled as for an ordinary IC engine and insulated from the hot head by a thermal isolation gasket.

Not sure if that's clear, but hopefully I'm making some sense...

Regards,

Jason

[Smertrios]

Anyone make an on-demand type of boiler? Instead of heating the piston or a large boiler filled with water you would heat a smaller metal tube (or boiler) up to very high temp and inject water as needed to adjust the power output of the engine. Fuel use could also be adjusted on an as needed basis to get more or less heat to the boiler IE: add more fuel and/or more air to get more flame

[trevj1]

Originally Posted by Smertrios Anyone make an on-demand type of boiler? Instead of heating the piston or a large boiler filled with water you would heat a smaller metal tube (or boiler) up to very high temp and inject water as needed to adjust the power output of the engine. Fuel use could also be adjusted on an as needed basis to get more or less heat to the boiler IE: add more fuel and/or more air to get more flame

Anyone, like, commercially?

Flash steam boilers were used a lot in model racing boats, and were used in steam cars, like the Stanley Steamer.
Stand alone versions were made,too, as portable boilers.

Cheers
Trev

[RonL]

Originally Posted by Rolf_K I have been lurking on your forum for some time, much interesting information and pictures. All my tools are just sitting there now as I am not able to stand up for any length of time. But my computer and brain is still working overtime. The other day I came up with this idea and was wondering if it could possibly work. What I am asking is, what is preventing us from keeping the cylinder(s) superheated and injection water on each power stroke (similar to diesel engine) so that no boiler would be needed; granted the engine would not look anything like we consider a normal steam engine because the cylinder(s) / boiler would be one and the same! I did search the net to see if anyone had tired this or even though of it, before I posted. Rolf

I believe you are thinking in the right way, and would suggest you look at resistance heating of your cylinder liners, make them much thicker to get a large mass thermal storage, and if for a start point 5KW per cylinder, an 8 cylinder engine would turn a 40 or 50 KW generator, a few batteries and a hybrid free of fossil fuel might emerge.

Energy cannot be destroyed, and there is no law that says so much of it has to be wasted.

Just a thought to start on.

Ron

[Geof]

Originally Posted by RonL ....Energy cannot be destroyed, and there is no law that says so much of it has to be wasted. Just a thought to start on. Ron

Unfortunately there is a law, it is the Second Law of Thermodynamics which says that not all the heat energy supplied to a heat engine can be used to do work.

What Rolf_k is contemplating is more or less equivalent to the original Newcomen steam engine in that it would work through a very small temperature range. Granted the Newcomen engine worked at a relatively low temperature and Rolf_k's would work at a high temperature but was is important for efficiciency is that the engine absorb heat from a high temperature source and reject heat to a low temperature source.

In steam engines this means you need steam at the highest temperature and pressure feasible entering the cylinder. As the steam performs work by moving the piston it expands and cools down and you want the expansion hence cooling to be a large as possible. In a single stage engine the steam still has significant heat and pressure even at the full piston stroke and this means a large portion of the heat energy entering the cylinder in the form of really hot steam is lost as medium hot steam.

This is why compound expansion is used where the still hot medium pressure steam passes from the high pressure cylinder into the medium pressure cylinder where it expands further doing more work and cooling further. A further stage of expansion is possible but as each succeeding piston has to be larger than the one preceding all the valves and connecting ports have to be bigger and significant heat starts being lost here. Also there is a practical limit to the lowest temperature possible because the steam has to be kept as steam not condensed into water, at least not in the cylinders.

All this means that significant heat is unavoidably wasted and even the largest and most efficient steam engine possible, which would be a multi-stage turbine still wastes something like 55%, or more, of the energy used to make the steam in the first place.

[RonL]

Originally Posted by Geof Unfortunately there is a law, it is the Second Law of Thermodynamics which says that not all the heat energy supplied to a heat engine can be used to do work. What Rolf_k is contemplating is more or less equivalent to the original Newcomen steam engine in that it would work through a very small temperature range. Granted the Newcomen engine worked at a relatively low temperature and Rolf_k's would work at a high temperature but was is important for efficiciency is that the engine absorb heat from a high temperature source and reject heat to a low temperature source. In steam engines this means you need steam at the highest temperature and pressure feasible entering the cylinder. As the steam performs work by moving the piston it expands and cools down and you want the expansion hence cooling to be a large as possible. In a single stage engine the steam still has significant heat and pressure even at the full piston stroke and this means a large portion of the heat energy entering the cylinder in the form of really hot steam is lost as medium hot steam. This is why compound expansion is used where the still hot medium pressure steam passes from the high pressure cylinder into the medium pressure cylinder where it expands further doing more work and cooling further. A further stage of expansion is possible but as each succeeding piston has to be larger than the one preceding all the valves and connecting ports have to be bigger and significant heat starts being lost here. Also there is a practical limit to the lowest temperature possible because the steam has to be kept as steam not condensed into water, at least not in the cylinders. All this means that significant heat is unavoidably wasted and even the largest and most efficient steam engine possible, which would be a multi-stage turbine still wastes something like 55%, or more, of the energy used to make the steam in the first place.

I didn't say much because I have a poor ability to translate my thoughts into words that make much sense to most people that read my post.

My first take on what was being said by Rolf_K, was the injection of water at a superheated state, with a large mass storage by the piston, cylinder liner, and head, the steam would stay at high pressure as the piston desended because of this transfer of heat from the areas mentioned. At the discharge point the KE of all rotating parts in the system would recompress the gas to a superheated critical state where it once more is injected back to the pressure chamber.
The overall system would be a fast cycle, hot, and high pressure, process.

This might pose a design engineer a lot of grief, but with different layers of insulation, lubrication of the piston could stay in a proper heat range, while inner areas would be hot to an extreme.

I see a system that keeps heat in circulation as much as the gas that carries it.

Ron

[Geof]

Originally Posted by RonL .....My first take on what was being said by Rolf_K, was the injection of water at a superheated state, with a large mass storage by the piston, cylinder liner, and head, the steam would stay at high pressure as the piston desended because of this transfer of heat from the areas mentioned. At the discharge point the KE of all rotating parts in the system would recompress the gas to a superheated critical state where it once more is injected back to the pressure chamber. The overall system would be a fast cycle, hot, and high pressure, process. I see a system that keeps heat in circulation as much as the gas that carries it. Ron

But it would not do any external work. A heat engine takes heat from a high temperature source, uses some of it to do external mechanical work and rejects the balance (which in fact is most of it) to a low temperature heat sink.

[RonL]

Originally Posted by Geof But it would not do any external work. A heat engine takes heat from a high temperature source, uses some of it to do external mechanical work and rejects the balance (which in fact is most of it) to a low temperature heat sink.

Would this low temperature heat sink, in most cases, because of simplicity in design, be a rejection to the atmosphere where it is considered waste heat and not worth the effort to try and reclaim it ?

[Geof]

Yes very often the low temperature sink is the atmosphere; this is the case with an internal combustion engine. In the case of steam it can be a river, lake, the ocean or a condensing tower.

From the point of view of getting more mechanical work out of it this energy is 'waste'; you cannot reclaim it for mechanical energy. However, it is not waste if you have an application for heat such as heating a building or for use in an industrial process.

This is the whole idea behind co-generation or combined heat and power, CHP. The generating facility is located at the point of consumption and the 'waste heat' from generating electricity is used to heat buildings or in manufacturing processes.

Co-generation is not at all feasible with nuclear power and is only marginally feasible with coal because the generating facility has to be large for good thermodynamic efficiciency. It is feasible with diesel and is eminently feasible with natural gas.

Natural gas fueled gas turbine generators are used quite widely for peak load requirements because they can be started quickly and throttled up and down. Both nuclear and coal powered generation is best suited for supplying a constant demand because the output from these facilities cannot be varied very much or very quickly.

This use of natural gas is more or less impossible to avoid but in terms of energy efficiency it is ludicrous. In most cases the waste heat from the gas turbine, i.e. up to 60% or more of the energy provided to it is rejected to the atmosphere at the location of the gas turbine generating facility. The 40% or less that is converted into electricity is then transmitted to an apartment building, for example, and some of it used for building heat.

If the gas turbine facility was in the apartment building the heat rejected during the electricity generation can be used for heating the building so in a sense building heat is free. This heat can even be used for cooling by using an absorption cycle refrigeration unit in the air conditioning system.

Combined heat and power (CHP) systems can be scaled down to an individual house scale and some companies are slowly making these available. They are simply an automobile engine tuned to run on natural gas at optimum efficiency. These units need not be expensive because all the technology is off the shelf and for an individual homeowner they can reduce electricity from the grid to zero without seriously increasing the amount of natural gas consumed for normal heating requirements. Unfortunately regulations that favor the status quo can interfere with them being installed.

[gandalf1]

Many years ago there was such or similar type of engine described in the Model Engineer magazine here in UK. It weas described as an explosive steam engine and there were thoughts of it being developed further for use especially in so called underdeveloped countries where there is a lot of sun and high temperatures.
The basic idea was to heat the cylinder head with a flame or even put it at the focal point of a mirror system so sunlight could do the heating. Head and piston obviously would need making from heat resistant materials and the original scheme envisaged a closed water or working fluid system so lubrication was out of the question so a carbon piston was suggested. The cylinder head was to be heated by whatever source was available be it flame or sun and a small quantity of working fluid injected which then 'exploded' into high pressure steam thus driving the piston down the cylinder. The idea was originally conceived while watching a smith working hot iron and spitting on the metal before hitting it immediately with his hammer and the resultant 'explosion causing the hammer to rise again thereby reducing the amount of work the smith did. An example was demonstrated at a Model Engineer exhibition using a blow torch to heat the head and by the written account the results were very promising. Even with a low efficiency using Free Sunlight as the heating medium has got to be a good thing. Sadly here the amount of sunlight falling on us rather precludes such an interesting idea being developed further for domestic uses.
John.