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41

Because boiling a volume of water creates a much bigger volume of steam this volume increase is about 1700 times. According to the gas laws doubling the absolute temperature of a volume of gas only doubles the volume at the same pressure, or doubles the pressure at the same volume. Doubling the absolute temperature means going from 300 K (27°C) to 600 K (...

36

Steam piston engines can generate a lot of torque from stationary and the pistons can be physically remote from the boiler, so in most cases it is most convenient to have the pistons directly drive the wheels via a crank. Equally as trains don't have a steering mechanism as such and have conical section wheels, you don't need a differential either. In ...

28

I would say that using a warm pressurized gas is not very feasible. Ratchet freak already mentioned how you can get much more volume out of heating water into steam than just heating up air until it's warmer. This touches on, but doesn't completely address an important factor about steam as power. Converting to steam includes a phase change from liquid to ...

14

Here is a picture of the crankshafts inside a modern internal combustion engine: The purpose of these is to convert the back-and forth motion of the piston into rotational motion. It's very much the same mechanism as used on old steam engines: The difference is that in the internal combustion engine the power is not transferred directly to the wheels but ...

13

Hot air engines are feasible, and have a 200 year history behind them, starting in 1816 with the Reverend Robert Stirling. The other answers are largely correct : steam offers more energy per unit volume, but theoretically lower achievable efficiency while the Stirling Cycle can (in theory) match the ideal efficiency of the Carnot Cycle, using a regenerator ...

12

The main reason is that a turbine requires a pressure drop to extract energy from the working fluid. The drop in temperature that is observed in a turbine is a result of the expansion of the fluid; the turbine doesn't have a way to extract the heat energy directly from the fluid. The total work done by the fluid is typically expressed as a change in ...

12

I would like to point out that modern cars do not use cogwheels for transmission, they use shafts. Cogwheels are used for the gearing and differential. But bar mechanisms were used mostly because they didnt have the kind of manufacturing facilities as we do today. Bar mechanisms are easy to make, they are flexible and field maintainable. In any case in ...

9

There are really countless possible answers to this. I'd like to add one that hasn't been made clear yet. If you are doing a closed cycle, where you aren't letting steam/gas out into the atmosphere, at some point you need to pump the fluid back into the boiler to gain energy again. Pumping gas is very difficult to do. Pumping liquid water is very easy. ...

8

There's some interesting information on a number of alternative working fluids here, including ammonia, alcohol, mercury, sulpur dioxide, freon, and many others. Refrigerants are used today in organic rankine cycle applications which operate at lower temperatures than steam systems and are used to generate electricity from waste heat sources. These are ...

7

In the ones pictured, there are no trailing axles - they are a 2-6-0 and a "tenwheeler" 4-6-0 respectively. The ones shown have the firebox between the two rear drive axles. .That was an evolution of the earlier 4-4-0 arrangement. In later 4-6-0, "Prairie" 2-6-2 and "pacific" 4-6-2s and tank engines with those configurations, ...

6

Pressure is force/area, if the area offered by the pump impeller is smaller than the area against wich the steam must force its way out of the boiler, and both the turbine and the pump are linked, then, the same pressure will result in a smaller force on the pump than on the turbine. Example : Lets suppose that the pump is a piston pump, and on the steam ...

5

for a while, steam locomotives actually used gears and cylinder/piston sets which drove crankshafts. These were called geared locomotives and they were used to haul heavy loads up particularly steep inclines at low speeds. this made them popular for timber logging operations in the western US during the days of steam power. for higher speed use on more ...

5

While toy steam engines often require that one pre-fill the boiler, and then only operate until the boiler is nearly empty, most practical steam engines require that every gram of steam which leaves the boiler be replaced by a gram of water during operation. The amount of work required to pump a gram of cold air into an engine is slightly less than the ...

4

It is called a "steam wand gasket". Technically, it's a ball-and-socket joint made out of two concave PTFE (Teflon) gaskets and an EDPM gasket for the seal. There may be other designs too; I learned this by watching Saeco StarBucks Barista - How to Replace Steam Wand Seals and Gasket (YouTube video).

4

The way of removing couplings in the worst case scenario, where all other alternatives has failed, is to physically destroy the coupling. Cut/grind 2 slots the entire length of the coupling on opposite sides, usually one on top and one on the bottom. The slots need to be deep enough that it is at least flush with the pipe its screwed onto, pretty much as ...

4

The main reason is that it takes much less energy to compress a liquid than a gas by the same pressure difference. The pump takes a little bit of energy to compress the water, but a huge amount of energy is released when the steam expands in the turbine. This is why a phase change is used in the Rankine and related cycles. Another thing to consider is ...

4

Heating water to make steam is not necessarily more efficient, but a lot more practical. What you describe is how internal combustion engines work, for example, so it's a valid concept. However, they do this in bursts and use liquid and carefully engineered fuel, which makes the implementation more practical. In a continuous system as you describe, the ...

4

The maximum efficiency of either the Diesel or a steam engine cycle is (assuming you can treat steam as an ideal gas): $$\eta_{Diesel} = 1 - \frac{1}{(\frac{V_{Max}}{V_{Min}})^{k-1}} \left[\frac{r_c^k-1}{k(r_c-1)}\right]$$ Where $k$ is the heat capacity ratio, and $r_c$ is the cutoff volume ratio - i.e. the ratio of volumes after and before the combustion ...

4

Because you can't get something for nothing? If the generator is generating more electrical power then that energy has to come from somewhere. The more power you try to pull from a generator the harder it becomes to turn the generator. If it's harder to turn the generator then you need to push harder on the turbine driving it. The way you push harder on the ...

4

One thing to consider is that pipes used for heating like this are normally « finned » to increase the surface area - fins can be small discs fitted to the pipe or even wire loops - both increase the surface area massively and reduce the length required. This article explains the finned pipe although they are collecting heat: The performance of a coiled ...

4

Steam generates full torque at zero speed as has been mentioned elsewhere, so like in an electric car (which has very much the same sort of characteristic), there is little to be gained from a gearbox, may as well drive the wheels directly. This is also why the vast majority of diesel locomotives above the very small, are really diesel-electric, it makes ...

4

There have been some locomotives with this design, it's called "Cab forward." As the article says, Southern Pacific railroad in the US had some cab forward locomotives, which solved crew asphyxiation problems on some mountain routes where there were multiple tunnels and snow sheds. The downsides to the design were concerns about what would happen ...

3

You can use the Hagen-Poiseuille equation to determine the flow rate as a result of a pressure gradient. A caveat in using this equation is that the flow has to be laminar, i.e. inertial effects can be neglected. It is best used in the form: $$Q=\frac{1}{128}\frac{\pi d^4}{\mu}\frac{\Delta P}{L}$$ from which you can see that the volumetric flow rate $Q$ is ...

3

You stated that most things you found are too complex for your basic understanding, is it safe to assume that the answer you are seeking may be an educated guess? If so I would go with Bernoulli $$g z_1 + \frac{c_1^2}{2} = g z_2 + \frac{c_2^2}{2} + \int_1^2 \frac{dp}{\varrho}$$ Assume isothermal state change. Also assume $c_1 = 0$ if you say you regard the ...

3

You are almost describing a gas turbine engine. These are used to generate electrical power, and also to power aircraft. But, in a gas turbine the output of the combustor is at high pressure, and that is used to turn a turbine. And, that is a different combustion cycle from a steam cycle.

3

Do a web search on "Rankine cycle". The real key is that in a practical heat engine, you need to pump in cold working fluid, heat it, let it do work (and cool) as it expands, and then repeat. If you ignore losses, the energy to pump a working fluid up by a given pressure difference is proportional to the volume times that pressure difference. A mole of ...

3

A governor is a poor application for steam locomotives because the throttle is constantly adjusted by the driver. Speeds, loads, and steam pressure change constantly, plus a major part of driving a train is managing slack in the cars. Even today, managing slack is done by the engineer using the throttle. All this means that an engineer would spend more ...

2

It all depends on the sterilization level you want to achieve. As you say, you would need to know the death kinetics parameters, or equivalently the log-decimal reduction time (D) and how it changes with temperature (Z). As sterilization is a problem that takes place almost everywhere in food industry, a standard sterilisation cycle lasts for 30 min. at 121 ...

2

The reason wind turbines use three blades is because it reduces the load fluctuations (fatigue) on the turbine shaft an bearings. Wind at high altitude is faster than the wind at low altitude. A two bladed rotor would be the most economical if it were not for the largest horizontal load being on the upper blade while simultaneously the lowest horizontal load ...

2

Steam engines can expand the steam only so much before the water vapor starts to condense. In addition, the volume of the vapor increases significantly as it expands, making it difficult to obtain further work, as the cylinder size must increase to accommodate the volume of vapor passing through it. Most steam engines use three or four cylinders to expand ...

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