start up times

Thank you for adding me. I would like to pose a question to members for opinions if you please.

Could it be that the slow start up times could have contributed to steam automotive development and proliferation as a mainstream traction alternative?

Certainly, that was a significant factor that inhibited the adoption of steam automobiles -- but it was far from the only one.

Regards,

Ken

Thank you for responding Ken. Certainly not the only setback but a substantial one. My name is Richard. To further expand this topic I would like to suggest a thermal transfer fluid boiler and CANBUS to manage steam. As a series hybrid, the steam would drive a generator powering an electric traction motor. And yes, batteries. About 15kwh to satisfy that "I wanna go NOW" part of human nature until the steam comes up. I hope I'm not cluttering up the forum with silly ideas, like firing up a 3 wheeled horseless carriage to terrify the townspeople in the 18th century. Thank you.

There are some fairly strong engineering minds on this forum. I'm a guy who only made it through a couple of years of ME before running away to what I thought was a much easier major. My comments are therefore those of an amateur.

The vehicle has to carry stored energy since it is non-tethered like an electric street car. The stored energy in a gas vehicle is the gas, in an EV a combination of the batteries and gas, and in a pure electric car it is the batteries. In a steam car the stored energy is mostly in the burner fuel.

Somewhere I read that per weight, gas contained the most stored energy of any portable source. Anyways, you need to add up the weight of the stored energy and the mechanism that turns it in to motion and subtract off the inefficiency of the system. The weight and aerodynamics of the car itself is independent of this calculation.

My guess is that when you add up the weight of the fuel for the steam burner, the water, the batteries and the engine itself it is going to be a lot to push around and inefficient. I'm just guessing.

Thank you for your reply.

The battery is not the behemoth of the tesla or other car but a portion of it. The vehicle need only operate all- elecric for maybe 15 minutes. Still only a thought thus far.

Honestly, economy is going to be dictated primarily by three factors, which in order of increasing importance are:

1. Rolling friction
2. Aerodynamic resistance
3. Powerplant thermodynamic efficiency

Rolling friction will be controlled by the properties of the road surface, the properties of the tires, and the vehicular weight. So, it is true that adding mass will increase friction and reduce economy. That said, note that this was the first in a list of increasing importance. The effects of weight are fairly minor compared to the following two items.

Aerodynamics is a function of resistance produced by the vehicle's drag coefficient, frontal area, and speed. Assuming our automobiles all fit into the same body and chassis, this has no effect on the comparison as it will be a constant factor for all vehicles.

Finally, we come to powerplant thermodynamic efficiency, which is the most critical function affecting economy. It is here that steam powerplants have a real problem, the Rankine cycle has limitations because it uses a condensable working fluid. When heating water (and other fluids) we see that it experiences "sensible heat", meaning that the fluid temperature changes a fixed amount for any given amount of heat applied per unit of weight -- say, for example, BTU per pound. When vaporizing, however, the fluid experiences "latent heat", meaning that a different specified amount of heat is needed per pound of fluid in order to convert it into a vapor having exactly the same temperature as the fluid itself -- which is called the saturation temperature. This value is given as 970.3 BTU per pound.

Heating the steam further causes its temperature to rise a fixed amount for each unit of heat added to a given mass; this is also sensible heat, although it has a different value than that for liquid water.

Now, the big problem facing a steam power plant is that vaporizing a liquid into a fluid is an example of a "non-reversible" process. In thermodynamic terms, this refers to a process from which we cannot extract work. So the act of either converting the water to steam, or condensing the steam to water, produces no work -- despite the fact that we invested a significant amount of energy into the process. Some of this energy can be recovered via a heat exchanger, but the effectiveness of heat exchangers drops dramatically as both working fluids approach identical temperatures. If our steam car condenses the exhaust back into water for reuse, we cannot recover all that much energy because automotive condensers cannot typically produce a significant partial vacuum in operation -- meaning that the condensate is already near the boiling point of water. This is hot enough that the engine exhaust steam can provide only minimal heating.

So, the latent heat of vaporization of water is our big roadblock to high efficiency. However, we also have to consider the issues of the materials used in power plant construction. The efficiency of any thermodynamic cycle is relative to the difference in temperature between the working fluid at its hottest and coolest states inside the cycle. While the gasses in an internal combustion engine can be hot enough to destroy the metallic components of the cylinder, head, and pistons, we can live with this by cooling those components sufficiently so that they can function without damage. This cooling wastes some thermal energy but, since most of the gasses do not come into direct contact with the engine surfaces, the net effect is that the gas temperature is still maintained at levels that can destroy the engine.

By contrast, steam engines require the use of a boiler which is composed of tubes that separate the combustion gasses from the water and steam -- whether the steam is on the inside or outside of the tube. Since combustion gasses are on one side of the tube and the water and/or steam is on the other, the boiler can only function by the passage of heat through the tube wall. This heat cannot be allowed to raise the tube wall to destructive temperatures and therefore our working fluid (steam) is well below the temperatures found inside an internal combustion engine. Since efficiency is predicated upon temperature, we find another limitation to the steam power plant.



Edited 1 time(s). Last edit at 05/19/2022 07:54AM by frustrated.

Thank you for your reply "Frustrated".

Here we come to another component of the system that has been poured over by highly knowledgeable people over many, many years and no amateur such as myself could ever hope to better. And this may expose my ignorance and end this discussion string as just another crackpot on the forum.

Boilers still need work. The Doble generator to my small bit of knowledge is the best ever created. I propose a thermal transfer fluid via heat exchanger around a body of water. Our transfer fluid temp is only about 600-700°F which might not be enough but can contain heat that otherwise is lost. According to steam tables I've reviewed 520°F water renders 800lb psig of steam and I can't argue the physics of temp vs pressure. It would be, as they say, have to be tried.

Thanks to all readers and greatly appreciate replys. If it stimulates thought and compels dialog then it's headed in the right direction. I'm certainly not the smartest guy in the room and especially when I'm by myself. (Lol)

The Doble generator to my small bit of knowledge is the best ever created.

Not in a long shot.

Rolly

Good to hear!

You should buy Jim Crank's book on the Doble. Very well down and it covers the other Steam cars. At the end of the book, I think he says the White was the best steam car ever built. Of course, the last one was built in 1910, so you would think there would be some improvements in technology in 100 years.

If I understand the original question correctly, the steam would power a generator which would power an electric motor. During the steam generator startup, the car would run under battery power. When the steam generator is up and running it would start recharging the battery.

Is that what you are proposing?

Thank you for your reply Alsancle!

Yes. It's difficult to communicate technical details in so many words in new ideas. That's why there are tech writers. They're akin to great novelists, only without so much fanfare.

The smallish battery acts as traction power and startup while the boiler comes up to pressure. The now ubiquitous CAN bus system monitors and takes care of the steam generator. Not much sport in this I suppose but this is consumer level design.

There are as many ideas for steam generation as have been boilers made and this too is different and deserving of an entirely different discussion. Thermal transfer fluid does the heat exchange to water and may be of greater value than this odd little car propulsion system presented here.

Instead of the Diesel/Electric you are proposing the Steam/Electric. Interesting, and I would wonder if any of the more seasoned members of the forum can remember anyone trying this. Typically, every idea has been tried at least once, sometimes very early in the automobile development and then "rediscovered" or often just forgotten.

I'm not smart enough to setup the calculation, but I'm going to stick with the opinion too much weight for all the components relative to the amount of propulsion you can generate.

Hi Richard (SteamPunk_Hybrid1925)

Welcome to the forum. Please don't hesitate to offer ideas and concepts about steam. There just might be a new concept worth pursuing. As a director of the club and a BSME, I just wanted to provide some input to this conversation along with some encouragement.

Attached is a concept for a locomotive that I think relates to your idea. Is this on the right track?

The other thing is you mention some ubiquitous boiler controller that I'm not familiar with...please explain. What type of boiler does it control?

Note that the Doble has a mono-tube steam generator along with the White. I'm thinking that's why you mentioned them. I think It is hard, difficult, to control the steam from a mono-tube, i.e. compared to a water level controlled boiler. Does this controller do that, control a mono-tube generator?

Kind regards,
Rick

I'm honestly puzzled by the heat transfer fluid surrounding a tank of water. While I can think of some effective binary fluid systems, and some systems with water heated by water, none of them seem to fit the bill. In any case, producing steam without later adding more heat to raise the steam temperature well into the superheat region will not allow the builder to fabricate an engine capable of any kind of efficiency.

Most steam car boilers operate in the 70 to 85 percent efficiency range, which actually isn't too bad. To increase the efficiency would require cooling the exhaust gas temperature down to that approaching the temperature of the incoming feed water.

The rate of heat transfer is going to be equivalent to (Material Thermal Conductivity / Material Thickness) * Heat Transfer Area * Temperature Differential

So, we have four issues limiting flow of heat from the gases to the water in the boiler. The first is the thermal conductivity of the material transferring the heat. If we use a metal with decent thermal conductivity, this isn't too big a problem. The second issue is the thickness of the material transferring heat -- the thicker the metal, the worse our heat transfer. Unfortunately, some of this is out of our control since the boiler has to contain water and steam at high temperatures and pressures -- meaning the walls need a reasonably great amount of thickness. The next issue is the area of the heat exchange material -- that is also going to be limited because we only have so much room inside an automobile to which we can devote to the boiler. Finally, there is the temperature differential -- as that drops, the rate of heat transfer falls. So, to achieve higher efficiency we need to either increase the heat transfer area, make the material thinner, or go to materials with even better thermal conductivity. Given that people have been building boilers for over 200 years, we can take it as a given that someone has looked at this already and pushed matters as far as they can go. For example, the Doble Ultimax boiler, the SES, Carter, and Barrett boilers all used finned tubing (along with many others). The fins provided a great deal of heat transfer surface in a small package, permitting boilers much smaller than the Doble E and F series could manage for comparable output.

As far as preventing heat escape, this is usually accomplished in a couple of ways. Lagging is the simple expedient of adding insulation to the outside of the boiler. Another method is to conduct air to the burner by way of an air space surrounding the boiler. Heat leaving the boiler raises the temperature of the air flowing into the burner. This not only aids in clean combustion, but it carries heat that would otherwise escape into the atmosphere back into the boiler. Some boilers have been built with a scroll-shaped housing to further reduce losses, the air circles inwards maybe 2, 3, or even 4 times so that the heat loss through each layer of the housing is returned to wence it came. Given the low air pressures involved, this methodology results in relatively low weight added.

I can see a steam-electric drive working, but question why one would build such a thing. The market is currently effectively about zero and it is almost impossible to conceive of the odds ever improving, given regulations regarding fuel economy and pollution. In a related area, governments are slowly forcing the adoption of electric or other ostensibly "zero emissions" vehicles, so it is a matter of bucking the system without having a trump card you can play. Lightweight boilers with fan driven burners come up to heat so rapidly that the steam car hobbyist won't find the matter an issue and there is virtually no chance that anyone else will possess such a vehicle. The real problem of such a scheme is that it increases weight, volume, and complexity -- all of which steamers don't need.

Regards,

Ken

Thanks Ken,

It occurred to me to handle steam more as a process technology than a traditional boiler. If the steam generator can't be built to be smaller, lighter in weight and more efficient then it is not a candidate in the form factor I've presented.

The basic premise of this is the backend of a molten salt system proposed for a nuclear power plant. ORNL ran a prototype a few years. A solar version exists, or did, but was recently shut down in the Las Vegas area.

The nuances of scale can make or break the functional efficacy and practicality of a system. Small models can grow into bigger ones.

Thanks to everyone that would even consider this ruse as worthwhile reading. Try it yourself. Wrap a copper coil around a pipe, circulate paraffin through it and see what happens to the water in the pipe.

Betcha it boils ;-)

Thanks

Richard Evan Riddle
Mobile, Al

The other thing is you mention some ubiquitous boiler controller that I'm not familiar with...please explain. What type of boiler does it control?

CANBUS is an embedded protocol based system ideveloped by Bosch (1995) You might know it as the OBD II that throws codes everytime something malfunctions or the gas cap didn't get screwed back tightly enough on the car.

The various valves, sensors, switches and servos on this newfangled boiler might be tweeked as components not only talk to you or the ecu but to each other.

As for the boiler the form factor follows treating water as a process technology.

Thanks again to all.

Once again, excuse my naive thoughts on this. The just in time steam generators like the Doble seem to require very complex control systems to make sure you have enough steam when it is requested. The Stanley with its fire tube boiler doesn't have the same issue but suffers from long startup times.

I would think in the scenario described here, you could have a just in time sort of system but with a much simpler controller. The reason being you are only trying to keep the batteries charged to an adequate level to continue to power the electric motors.

For example, whenever the batteries reach 75% charge, the steam generator fires up to run the generator. Since the batteries contain the stored energy, not the generator, you don't have the Doble like control issue.

I am so grateful for the interest.

Yes. It is a series hybrid like the Fisker, BMW i3 ot Chevy Volt.

I became aware of one of the pitfalls of steam early on. It does not like to change speed. My father ran boilers at TVA many years. They're fine until the turbines spin down and the whole process has to be restarted.

While this is still only a thumbnail sketch it is imagined that the steam remains at a constant speed until shutdown. The CAN bus monitors and executes blow down, oil flow, steam trap, water injection and other functions. This invites consumer level use.

Given management can be altered with a line of code and relays the electric motor can be powered directly by the steam electric generator while the batteries sit idle. The power harness is the same. Battery output and electric generator are the same and the power management system doesn't know the difference.

This is not a template or architecture written in stone. It could go in any direction insofar as components. Water could be instead freon or other gas phase change material. The steam engine could be Stirling cycle.

But what I think is central to it all is the thermal transfer fluid. We've thrown fire at pipes full of water, (or vice versa), and dealt with its limitations and frequent catastrophic consequences.

Thanks again

Actually, steam plants can change speed quite readily. Central power stations are designed to run at a fairly constant output, but that's hardly the only kind of steam plant out there. Consider an aircraft carrier. Maybe not as big as a central generating plant, but it still packs 280,000 horses in the main engines along with 64 megawatts of electrical generating capacity, along with providing hotel service steam and distilling hundreds of thousands of gallons of fresh water per day. And let us not forget how much steam the catapults consume... One moment you may be floating along at a couple of knots just maintaining steerage, and then the word comes in to accelerate to 30+ knots. From experience, I can tell you that they open the throttles NOW and accelerate smoothly up to speed with steam production rising as needed. So, no, inflexibility is not necessarily part of the package -- it all depends on the original design parameters.

Honestly, I don't get the importance of thermal transfer fluid. The boiler, or steam generator, is a large heat exchanger. Add heat on one side and water on the other, pull steam off the top. Thermal transfer fluid just adds yet another heat exchanger. Mechanical systems hardly ever get smaller, lighter, or more efficient when you start stacking additional elements -- the general trend is in the opposite direction. You can't really argue the point from a safety angle since steam systems built to code are almost ludicrously safe -- the margins are incredible. We can't really claim improvements in efficiency since there is still some sort of combustion from which heat need be extracted and basic thermodynamics impose practical limits on combustion based on environmental conditions. The real limiting factor for any boiler is the combustion gasses, the heat transfer is "air-side limited". This is sort of obvious, simply upon inspection, when we consider the density of air versus any solid or liquid working fluid. So, we can stick water, molten sodium, Learium or any other material inside the boiler tube but the rate at which the system can absorb heat is limited to how much surface area the combustion products can work against.

I long, long ago looked at a steam/electric hybrid and came to the conclusion that the concept works better with internal combustion. The problem is that the steam plant is already going to be larger and heavier than a comparable ICE, adding an electric drive train is taking us in the wrong direction. This led to the conclusion that maybe steam car enthusiasts focus too much on power plants.

Automotive engineers consider powertrain to be one element contributing to vehicular efficiency, not the only factor. A compact power plant of lower efficiency may well be superior to a larger plant of higher efficiency. Let's say we made this highly efficient power plant by building a larger engine that has shorter cutoff and operates at lower rpm in order to reduce friction. Let's also assume that we have a very large condenser, condensate deaeration equipment (no one ever thinks of this one), plus large economizer and air preheater sections. All of this not only adds weight, it takes up space.

Unfortunately, in an automobile, empty volume is heavy. I know, that sounds silly, but let me explain. Any volume has to be enclosed by some sort of structure, and the amount of structure increases along with the volume. And, if you've looked at the strength of components, you realize that the structure has to get stronger as the volume increases (hence, the reason boiler tube gets thicker as the diameter increases, even if pressure remains constant). Beyond that, weight is additive. Suppose we end up with a 50 percent increase in powertrain weight. This is going to require a stronger support structure in the car, which also adds mass. This mass is going to put a strain on the suspension, steering and brakes -- all of which need to be beefed up to deal with the extra load -- and this impacts wheels, tires, transmission, and so on. That isn't the end of it, however, it becomes an iterative process. Beefing all the components adds yet more weight, which must again be dealt with, and so on. The mass increase at each step dimishes greatly, but the net result is still additive.

So, paradoxically, the highly efficient power plant might return worse fuel economy than the less efficient but smaller competitor. The lesson is that you don't design the power train in isolation.

Regards,

Ken

Back in the 70's we played with that concept when I was in the steam car program at Chrysler Engineering. They said they didn't want to put a 300 # starter motor on this thing. As soon as they used up the grant money, the program was dumped. They wrote it off in one paragraph. I think I gave Ken a copy of that study.

That's awesome! I have run across mentions of "steam power" that really wasn't, more like a gas like freon that expands and then recovered. That's classic stuff. Thanks!

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File Name	File Size		Posted by	Date
Locomotive Concept.jpg	653.3 KB	open | download	Rick.H	05/23/2022	Read message