How do diesel engines work?

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I hope not too, we should be running our cars on hydrogen.

Did you see that BMW car that was tuned to run on hydrogen, proves that you don't need fancy slow hybrid cars to solve the polution problem.

Hyrdogen is the cleanest fuel there is, absolutely no bad stuff comes out of the exhaust and it'll work on our existing engines so no need to say bye-bye to our VTecs or V8's!

the only problem is storing it under pressure in a car, if it was in a smash it could explode, fuel-cell technology should overcome this problem, hopefully these can be made cheaply and be affordable.
 
falling asleep josty? or is your turbo spooling up :D

i've been thinking (oh no!), diesel has a higer burn/explode-temperature than petrol, so why does diesel combust because of pressure, and does petrol need a spark? should be the other way around if you ask me
 
Nono, that was the electric engine from the future! :D

Diesel mixture needs a higher compression ratio to explode. The air is getting compressed, when you compress particles, they move faster, which creates heat. When compressing more, the temperature of the air mixture is getting hotter and hotter, and finally when it's hot enough the diesel is sprayed in and the heat of the air will let the diesel explode.

Petrol has a sparkplug, the compression ratio isn't high enough the get the air at the temperature at which petrol ignites. Also the petrol is sprayed in before the compression stroke, not with diesels.
 
so it should work (poorly) if you run a diesel engine on petrol?
 
Maybe, never tried it, don't think so though, diesels don't have sparkplugs so teh mixture isn't being ignited.

Edit: I'm pretty sure it wouldn't work, petrol has a higher combustiontemperature, the air in the engine would get compressed, get hot, and the petrol is sprayed in, but wouln't ignite.
 
I heard that if you fill petrol on a Diesel it will ruin much of the engine.
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It's very much like filling up with water. The cylinders quickly fill up with liquid petrol, which doesn't compress, and the upward stroke of the cylinder blows the heads.
 
kanderson said:
I heard that if you fill petrol on a Diesel it will ruin much of the engine.
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It's very much like filling up with water. The cylinders quickly fill up with liquid petrol, which doesn't compress, and the upward stroke of the cylinder blows the heads.
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That's not the main concern when filling a modern diesel engine with petrol. Since petrol has less lubricating characteristics, the fuel pump, injectors (which are very precisely engineered on modern diesel engines, due to the high pressures and very fast opening and closing times certainly on the second generation CR diesels) are not lubricated enough and are damaged badly.
 
not lubricated enough and are damaged badly.
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I suppose this is true if the petrol has enough time to mix with the diesel already in the system, otherwise the petrol won't even ignite and the engine will either quit (if it's not revving very fast) or blow the heads.

I've only witnessed two diesel engines filled with gasoline (petrol) and they both blew their heads within a few seconds after the fuel hit the engine. In both cases the engines were wound up at high RPM (3500+, high for diesel) accelerating out of the filling station.
 
qube said:
Hydrogen is the cleanest fuel there is, absolutely no bad stuff comes out of the exhaust and it'll work on our existing engines so no need to say bye-bye to our VTecs or V8's!
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But, were does the hydrogen come from? They have to produce it. And the production of hydrogen can be very environmental unfriendly. The most used method to produce hydrogen is electrolyse, which eats electricity like hell. So if the hydrogen solution wants to be a tree hugging solution, the electricity production has to be environmental friendly (for ex. hydro, solar, wind, nuclear, etc).

There is also one problem when fuelling your car with hydrogen: a lot of hydrogen will escape into the atmosphere, a lot more than with petrol or diesel since hydrogen is very volatile. Too high concentrations of hydrogen in the atmosphere also aren't good for the environment.




qube said:
the only problem is storing it under pressure in a car, if it was in a smash it could explode, fuel-cell technology should overcome this problem, hopefully these can be made cheaply and be affordable.
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Why would fuel cells overcome this problem? You still have to use some sort of hydrogen reservoir.

But if the car stands in the open, a hydrogen tank will not explode in 98% of the cases, since hydrogen is so volatile, it evaporates and flies away before explosive air/hydrogen concentrations are possible.

But when in hydrogen still gets ignited, there is a problem. You can't see or smell a hydrogen flame. Ask a fireman, they will never enter a building when they know there is a possibility hydrogen will ignite.

So in open places there is not a real problem with hydrogen tanks in a car? But when the car is parked in a small garage, things can be really dangerous. In this case the hydrogen gasses can't escape fast enough. And since the explosion barriers of a hydrogen/air mixture are wider than for example petrol/air or LPG/air, there is a big possibility the mixture will ignite. The problem with hydrogen/air mixtures is they don't explode 'normal' like LPG/air, but they cause a detonation, a far heavier form of explosion. Most have probably already heard of detonation when talking about the octane number of petrol fuel and knocking of the engine. Well detonation is a term used for special heavy explosions. I won't go into the details what the difference is with a normal explosion (or deflagration, in scientific terms), but if you want to know it, just PM me ;) One characteristic of a detonation is that the pressure will rise a lot faster than with a normal explosion. The windows or other weak parts of the building won't have the time to break and release the pressure. The result is that at on point the building will just spatter into thousand of pieces.


As third remark, I add that the same engine will produce less power when it's driven by hydrogen compared to petrol if the fuel consumption remains the same. Hydrogen may have a higher combustion ratio (I don't remember the correct English term, sorry), but the specific combustion ratio is a lot lower.



I have only talked about the possible downsides of hydrogen. So don't get me wrong. I'm not against hydrogen. I only want to stress that it's vital that the implementation of hydrogen driven ic engines of hydrogen driven fuel cells has to be profound thought through. And currently we aren't there yet at all. There are a lot of issues to be solved. Certainly the environmental aspect. If We don't watch out, the pollution of cars will not be reduced with the introduction of hydrogen driven cars, but will be transferred from the exhaust to the production of hydrogen or electricity to operate the hydrogen production (there are other methods besides electrolyse).
 
kanderson said:
not lubricated enough and are damaged badly.
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I suppose this is true if the petrol has enough time to mix with the diesel already in the system, otherwise the petrol won't even ignite and the engine will either quit (if it's not revving very fast) or blow the heads.

I've only witnessed two diesel engines filled with gasoline (petrol) and they both blew their heads within a few seconds after the fuel hit the engine. In both cases the engines were wound up at high RPM (3500+, high for diesel) accelerating out of the filling station.
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Well if the fuel tank was pretty empty there is a lot of change a lot of petrol will flow through the fuel pump and injectors and they go wrong after some kms/miles.

The problem I was talking about is most common to occur when filling a diesel with petrol on the real modern diesel engines (CR and PD). On the more conventional diesels, you will probably encounter 'your' blown head problem I think. I'm aware of also only 2 issues of petrol in a diesel with people I know. Both were new cars, one with a CR engine, and the other with a PD engine. They both had to replace their fuel pumps.
 
Agreed on the extraction of hydrogen is currently difficult, it doesn't exist natually on the Earth, only as a Hydroxide (like Water) or a Hydrocarbon (like coal or oil).

However driving a car on hydrogen would be much more efficient than petrol because it's a far more efficient fuel they wouldn't use it in rockets if it wasn't.
 
qube said:
However driving a car on hydrogen would be much more efficient than petrol because it's a far more efficient fuel they wouldn't use it in rockets if it wasn't.
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Yes, hydrogen is easier to burn compared to petrol or diesel and it has a higher combustion ratio / heating value (more energy is released when it burns). But if you want to have the same amount of power when running on hydrogen you have to consume a lot more fuel/hydrogen, because the specific burning ratio (*) and volumetric efficiency of hydrogen is lower compared to petrol or diesel.

If you don't believe me, just try to find out some performance figures of hydrogen-driven internal combustion engines, for example that BMW hydrogen driven V12 7-series. Those performance figures are pretty low compared to a BMW V12 or V8 petrol engine.



The reason why rockets use hydrogen fuel is because their working principle is totally different compared to an internal combustion engine. They have to throw out mass at high speed so the rocket engine creates thrust. They don't have a closed combustion chamber like an internal combustion engine, so the specific burning ratio isn't really the most important parameter here. The combustion just has to create as much energy as possible. That's why they use hydrogen and fuel containing oxide.


(*) also takes into account the air/fuel ratio of the theoretical stoechiometric combustion and the thermal characteristics of the fuel.
 
woodchuck said:
Diesel works the same as regular fuel but there's no spark. It explodes when compressed enough.
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Yeah, what he said :thumbsup:
 
Nuclear power is about to take off bigtime. We have reactors that can run on nuclear waste too, so the whole process is that bit more environmentally friendly.

Australia is chock full of uranium, and i'm pretty sure that (meltdowns aside), nuclear power is the most efficient/enviro friendly power source available today.

There is another power-source project being constructed here soon, which uses convection heat to drive a big turbine (looks like a giant, hollow, toilet plunger stuck to the ground), but i don't expect it to meet the demands for consumption nearly as effectively.

With nuclear power we could create hydrogen without killing the earth. I don't see why we use organic-based fuels for power stations still, the technology to make an utterly safe nuclear plant has been around for decades. I put it down to the public being idiots, them getting scared at the mention of "nuclear".

On a similar note, Australian hippies stopped the use of irradiation for importing foods (a method of cleaning them of diseases etc). They got all pants-twisted over the word radiation, when i reality it's as safe as microwaving food (which i bet those damn hippies do!).
 
Yep, and nuclear powered cars would be a hit too. Especially when they crash.

"Residents are advised to avoid Sydney today as there has been a two car crash in the CBD."

On a different note, diesel fuel sort of works in the opposite way to petrol. With petrol, a higher octane number means better fuel, usually, but diesel uses a cetane number, which is basically the opposite to octane. A lower octane number works better in a diesel, etc.
 
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