Steam powered cars

Great Debates
41

Some of the problems the Doble has:

  1. Corrosion. Hot steam condensed to water sitting in pipes and fittings is not healthy for longevity.

  2. Energy transfer. The Doble has a gigantic ‘radiator’ up front that is actually the condenser for the steam’s closed cycle. Any heat it cannot shed has to be shed out of the car as steam, which means in the summer time the water tank only has a range of about 70 miles. It’s a big radiator and a big water tank. In a smaller regular car, it’s not clear that you could radiate all that heat out, meaning short range.

  3. Condensation in the engine. If you try to start the engine before the cylinder temps come up, there could be liquid water in the piston. According to Jay, if that happens the result is an immediately destroyed piston.

  4. Oil. Just like in an IC engine, you need an oil lubricant, and some of that oil gets past the rings and into the cylinder. In a steam car, that oil mixes with the steam, making a mess of the environment if you blow it out of the car. The doble has big cloth ‘diapers’ to soak up the oil/water mixture. The water evaporates out leaving the oil, but on a regular basis you have to remove the diapers and dispose of them.

  5. Energy loss when not moving. If you’re just sitting, you’re burning a lot of fuel to keep the temperature up. If you shut the car off, all the heat you paid money to generate radiates away, and then when you start up you have to sit and wait for the whole system to heat up again.

  6. Shedding heat - Jay says the engine throws off so much heat it warms the limousine-sized interior of the car without needing a heater. But in the summer, the car gets uncomfortably warm from the boiler heat transferring to the interior.

  7. Safety. Not just the risk of an explosion - there are check valves and such to prevent that. But the car uses 800+ degree superheated steam. A crack or a leak or rupture due to an accident is going to spray superheated steam everywhere. The boiler itself can heat to over 3000 degrees. In a major accident, that could be bad news.

There were a bunch of other problems that had to be solved or that still remain to make steam a practical choice. Maybe they can be overcome, but I’m assuming the smart guys who do the math look at the cost of solving it all relative to the gains to be made over modern IC engines, and go “Why?”

We’re now making direct-injection, flex-fuel IC engines that can burn all kinds of fuels and produce amazing amounts of horsepower for their size and fuel consumption. They’re modular, small, can be outfitted with turbos or used with hybrid drive systems, and they just work.

It’s going to take a big advantage to move away from the billions of dollars of development in modern IC engines and go to something radically new like a steam powered drivetrain, especially given the limitations and technical hurdles to overcome.

That said, it’s always worthwhile to revisit old designs in light of new technologies. Maybe the reasons steam was abandoned no longer exist - modern ceramics, computer controls, metallurgy and other advances may suddenly make steam look pretty good again.

But I have faith that the thousands of automotive engineers working for the major automakers are not stupid. I’m sure they’ve had plenty of bull sessions where they talk about alternative power all the time, just like we are.

And exotic projects get greenlit all the time - turbine powered cars, fuel cell cars, etc. There’s no lack of willingness on the part of the auto industry to try something new to gain market advantage. So if steam hasn’t made a comeback, there are probably good reasons for it.

42

I proposed this in a high school science report 35 years ago.

43

I’d think turbine cars would become practical before steam cars. The old Chrysler turbine cars actually had similar advantages and disadvantages to steam. Their main advantage was fuel flexibility-- though they wouldn’t run on coal and wood, they ran on virtually any liquid fuel. They also had ridiculously high low-end torque. But they also had the disadvantages of shedding tons of excess heat and high fuel consumption at idle. They did have a major simplicity advantage, having much fewer parts than a piston engine, in contrast to steam.

44

Water corrosion isn’t necessarily a problem if the circulating system is well-sealed and oxygen-free. Other fluids have been used in “steam” engines including flammable hydrocarbons - see http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/petrol/petrol.htm Although if you just want the fuel-flexibility of an external-combustion engine, stirling may be a better solution than steam.

I’m still of the opinion that having to conduct all the heat energy of the fuel to your circulating fluid through a thin metal surface adds a complication you could really do without. It also adds an inefficiency in series with your engine inefficiency - some of the boiler heat has to go up the exhaust flue. Then you have to dump the waste heat from your circulating fluid to air, again through a thin metal surface. You also have to lubricate your engine and prevent lubrication oil from contaminating your circulating fluid. And you have to shoehorn your solutions to all these issues into a vehicle. I don’t think fuel flexibility is worth it for light vehicles, frankly, although it may look better for trucks.

45

Even merchant ships are now not steam and it was not labor that caused the end of steam. The new Deisel are more efficient.

46

It’s not because of cheap labor. It’s because of cheap coal. India and China have more than enough coal to be self-sufficient, but both need to import oil.

47

You may be right about a Stirling engine! Thanks for making me aware of it.

But I still don’t see lubrication as such a major problem unless we are talking about water / steam as the working fluid. My air conditioner does basically the same thing as a steam engine, but in reverse. (In the AC, force applied by a motor pushing pistons effectively “moves” heat between an evaporator and a condenser. In a steam motor, heat “moving” between boiler and condenser drives pistons which can perform work.) Lubrication is accomplished by an oil charge which is contained in an oil reservoir and small amounts are mixed in with the recirculating Freon. The oil clearly isn’t a significant contaminant, and corrosion is not an issue. No shoehorning of this solution is required.

And cooling could be accomplished with a recirculating water system, identical to the water pump and radiator in an IC car. Well, not identical, we’d be cooling a condenser, not an engine block, but you understand. (Again a parallel to air conditioning technology, which can employ a water cooler to cool the Freon condenser.) And we seem to have adequate control of corrosion issues in our present applications with “coolant” or “antifreeze” replacing water. This would of course be separate from, and a parasitic load on, the “steam” system actually powering the vehicle, whatever its working fluid might be. (So, of course, would be things like an alternator to power lights and computer control systems. Just because it’s parasitic doesn’t mean it’s bad, or unnecessary. Nor does it mean overpoweringly complex; even cheap IC cars have all those and more.)

Again, I’m not offering steam as a panacea. But it still seems that there are problems with IC (dependence on oil with all the socioeconomic issues we know so well, plus global warming implications) and with electric and electric/IC hybrids (range limitations because batteries are a developing technology, lack of ability to move or tow heavy loads, implications from coal-based electric generation, etc.). So the fuel flexibility of a recirculating Freon “steam car” or light truck as a niche application might be useful. It could be set up to burn any of a number of relatively (even if locally) abundant fuels, like CNG, methanol, ethanol, isopropanol or other –ols, or whatever secondary product of oil cracking is produced and otherwise less salable when refining for a primary product like gasoline or home heating oil.

Efficiency concerns are valid, and I’m not an engineer, so I won’t try to evaluate them directly. But my understanding is that the power rating of an IC engine is entirely dependent on engineering decisions – displacement, compression ratio, etc. The energy available comes from the explosion of fuel/air in the cylinder, and this is basically a constant (each power stroke is effectively the same). So a car is designed with an engine whose power rating allows for the heaviest loads expected (weight and/or towing capacity). Your Buick has a V8 producing a maximum of 200 horsepower, because you need all 200 horses for 6 passengers, luggage, and two canoes on top. But for your lone commute to work, you are still running that same power plant, though admittedly at a very slightly lower RPM for the same speed.

Alternatively, the power produced by a steam engine is also partly dependent upon an engineering decision, that being the area of piston(s) which will experience pressure. But the power is also dependent upon the pressure acting upon that unit area. And, unlike an IC, this is variable. So a steam engine could easily produce power X at pressure R, enough for its rolling resistance and you to go 70 mph down the highway. By design, this could be a relatively low pressure, and could require minimal, or repeated but sporadic, doses of fuel to the burner to produce the heat required to hold that pressure. If called upon to move a greater load needing X+Y power, you don’t run the RPM up toward some red-line maximum. Instead the control system would simply increase the pressure to R+S by burning a bit more fuel for a longer period of time. Need to tow a boat? Then you want X+Y+Z power and produce it at R+S+T pressure. The power rating of your engine would not be “200 hp” (well, actually, probably more like “zero to a maximum of 200 hp at different RMP, best at 3800 to 5600 RPM”). For steam it might be “25 hp to 250 hp at design pressures from 100 to 450 PSI, continuously variable on demand”. Wouldn’t this be more efficient than the one-size-fits IC engine?

(Note that I pulled these numbers directly out of my ass. I’m a biologist, I can do that! However, I believe they are in the ballpark with actual working steam motors from the 20th century, and the physics of pressure times area equals power is not in doubt.)

48

History Channel is playing a tour of Jay Leno’s steam garage tonight. Conan O’Brien’s friends are all out complaining that it isn’t fair.

49

I love steam, retrotech and funky engines in general, but I really see small external combustion engines as having some basic limitations that stop them from ever being viable as IC engine replacements.

Oil contamination of water or any other circulating fluid is a problem because that fluid flows through the boiler and so sees hot metal surfaces, where lubricants tend to degrade and build up. Your AC unit doesn’t have this problem since the circulating fluid does not pass through tubes surrounded by fire! Oil seperators were a standard component on marine steam engines and would have to be present in a vehicle.

Of course cooling of a recirculating system would have to be accomplished through radiators but the amount of energy dumped through the radiator would be much larger than in a conventional car. Remember that your car radiator is only taking waste heat away that is conducted into the cylinder walls, the heat in the working fluid being dumped directly into the outside world through the exhaust pipe (and a lot of that heat comes out through the exhaust manifold.) In the condensing steam engine, ALL the waste heat has to go through the radiator. (IIRC, in a gasoline engine, 25% of the fuel’s heat energy is converted to engine power, 25% is lost as heat through the radiator and the remaining 50% is dumped through the exhaust pipe.) You’re probably looking at a radiator that is three times bigger, along with your boiler and oil separator, hence the shoehorn. Maybe doable, if you eliminate the transmission and use direct coupling, but difficult.

You also run into thermodynamics rather fast. The optimum efficiency in old steam engines was achieved by “compounding” - expanding the steam multiple times in seperate cylinders. E.g. the triple-expansion engine had three cylinders in series, a small hot one, a medium warm one and a large cool one. The idea was that you didn’t have your hot steam fresh from the boiler feeding into a cold cylinder cooled by expansion of the previous steam charge. This works well but it’s bulky - the higher power-to-weight engines trialled for aircraft used single-expansion and their efficiency was poor.

To get around the bulk of compounding, you can use “uniflow” cylinders where there is a hot inlet end and a cold outlet end of the cylinder with a temperature gradient along the thing. This basically gives you the benefits of compounding in a single cylinder but leaves you with tapered cylinders when the engine is cold, just waiting to sieze up.

Or you can say to hell with pistons - this is the 21st century and we’re going to use turbines or screw expanders or what-have-you. You can do that, but then you have to put the transmission back in - gears and clutch etc.

Corrosion control can be acheived in a number of ways but glycol-based additives are not one of them - remember you want to heat the fluid as hot as you can get away with for maximum efficiency. Glycol won’t tolerate too much of that.

There are whole forums devoted to this subject and they’re a great waste of time for tech nerds like myself, but I’ve yet to be convinced that steam in light vehicles is remotely viable. Trucks maybe, and trains certainly, but cars, no way. Not enough internal real estate.

Check out: http://bestpoems.ucoz.com/blog/the_technical_aspects_of_the_modern_steam_car/2010-07-30-43 for more info.

50

This is incorrect I’m afraid. While an IC engine draws the same volume of air into its cylinder with each piston stroke, in a gasoline engine the mass of air drawn in is variable. This is achieved by sucking the air in through a variable-sized hole (the throttle) so if the throttle is nearly closed, the cylinder fills with thin, low-pressure air. The fuel injection adds an appropriate of fuel and the spark lights it off, but the pressure on the piston face is very much smaller with the throttle opening small than large. (Diesels don’t throttle - they just add less fuel for less power.)

51

Thank you matt for all the info! I’ll do some reading and perhaps some re-evaluating too.