Explosion or detonation, that is the question?

[Lietseu]

Hello everyone, I allow myself to make a small subject of capital importance!

Explosion: following the activation of a layer of explosive (here the fuel), activation due to a spark, to high pressure ... The hot gases which escape from this layer, activates the layer neighbor who ignites in turn ... A flame front propagates in the mass of the explosive at a speed of between a few centimeters per second and some ten meters per second.

It follows that the production of gas and the increase in pressure are progressive . There is a blast. (Explosion)
it should be noted that the speed of propagation of the flame front can be modified by the density of the charge, the addition of inert or retarding materials .... like those used in the "super" which is in fact a detonant which is added a "retarder" to make it explosive

Detonations: a high pressure and high temperature wave (shock wave) is produced by the compression and ignition of the detonating gasoline ...

It is shock wave, which moves at a speed between 2000 and 7000 m per second brings the activation energy to all the molecules it encounters. The entire mass of the explosive is burned in a time close to the microsecond. This results in an acute increase in pressure which can reach 100.000 kilos per square centimeter and a sudden release of energy.
There are detonations. It is the detonation that causes the hardest concrete to break ... The engine ...

That is why it does not matter to put "Super" in an engine which needs "Normal" the performance will be less good since there is more anti-detonating in it, conversely if you put "normal" "(low octane number) you run the risk of screwing up your engine!

the symptoms are: knocking of the engine at low speed and the effects: risk of broken cylinder head, piston, or even crankshaft

[Capt_Maloche]

well, so what do you think of 5% of SP 95 in the GO?

[minguinhirigue]

Is it interesting to mount an engine to accept the detonation?

History to take advantage of this mode of "particular combustion".

I believe that Saint-hilaire proposed that with his qurbine, but as it turns not very round today, are there other contenders?

It is just necessary that the engine kinematics allow a very rapid expansion of the chamber at the time of the explosion (this is not the case of conventional pistons, which have at the time of ignition a relatively small volume variation I believe. ..)

[Lietseu]

well, so what do you think of 5% of SP 95 in the GO?

We continue in the subject addoc if not it will not be easy for others to follow the thread!



@+

[Lietseu]

Is it interesting to mount an engine to accept the detonation?

History to take advantage of this mode of "particular combustion".

Hi! I don’t believe that at the current technical knowledge level, we can do such a thing, for the simple and very good reason,
that I don't see how, you could build a mechanism, which would be so solid, that you could make it turn with a sticks of dynamite! ... it farts, it breaks everything!

In dragsters which are revised engines and designed for intensive use (single use, to my knowledge) we use in addition to gasoline, nitroglycerin, which is one of the most powerful detonants based on the nitration of glycerin.

Let us not forget that in the case of a conventional engine it should resist, for a long time! at pressures of the order of 100.000 kg / cm²!

What in no case the essence reaches.

We are talking about very dangerous things if you wanted to try this, know that the black powder is not an explosive, but with 10gr, you screw up the engine of a mob and the booth of board which is around, and you risk finding rooms 150 m away! lived, God nevertheless made me very careful, I still have both my hands and I have no burns of the type ... pest ...

This is to say that even if we made engines with alloys strong enough to resist, they would have to have cohesion forces so great that in fact, for now we are only dreaming ... .and they should also master their assemblies


Explosive greeting in good humor

[Other]

Hello

well, so what do you think of 5% of SP 95 in the GO?

In the manual of WV rabbit in America (Gulf) it recommends up to 20% maximum of gasoline in diesel in winter in very cold weather. it goes better in the filter and it starts better
a simple fuel heater corrects these problems.

In the frying oil I put 10% of ordinary gasoline and that makes the engine feel good.

An excess of petrol in diesel results in a loss of diesel power. (those who got the pump wrong and filled the diesel with gasoline know what it does)

For detonation in a petrol or diesel combustion engine, we are very far from the explosion of explosives (RDX).
normally we should say combustion engine, we are always looking for rapid combustion but still progressive
a mixture will detonate when its temperature at the end of compression is too high or when ignition takes place too early during the compression phase and the chamber decreases in volume, normally combustion must be completed during part of the descending phase of the piston (do not forget that the piston stops at the top only 25 degrees in advance it is a tiny part of the stroke)
In a petrol engine compression ratio 7
the speed of the flame front from 35 to 40 meters per second with the rise and the end, on average 18 meters per second.
from 3 to 4 milliseconds, which is very long in the language of the exhibition



Pure diesel, there is no sudden increase in pressure, there is progressive combustion.

An auto diesel there is a sudden build-up of pressure mainly due to a mass ignition of the badly sprayed drops and the one that wet the walls of the chamber is the characteristic noise of diesel (not desired) doping with water attenuated this banging ..

an injector that spits at 150 bars in a small room of a few cm it is impossible that it does not water the walls of the cylinder head which makes it complicated to build small diesel
and this is one of the reasons for the high efficiency of large diesel
combustion in a diesel engine is complex to analyze, it is far from a burner or a turbojet, in a piston engine it is only compromises. we must live with something imperfect which we will not see much improvement before the end of petrol.
Do not think that when you mix gasoline in gas oil that gasoline or acetone arrives whole in the injectors they are diluted in gas oil and form a product, it modifies its cetene index.

Andre

[Capt_Maloche]

Hello
Do not think that when you mix gasoline in gas oil that gasoline or acetone arrives whole in the injectors they are diluted in gas oil and form a product, it modifies its cetene index.

Andre

I follow you on most of your post, but for the dilution of the essence, I doubt

The essence is miscible in GO because it comes from the same basic product, but you will not change the molecular composition of each product, otherwise you would need a thermal or other reaction

This is the reason why the addition of a relatively small percentage of SP95 petrol in the diesel fuel allows a faster spraying of the droplets in the room and gives this spectacular result: around 3 times less emission of soot. https://www.econologie.com/forums/economies- ... 1-140.html

[Lietseu]

Hello

well, so what do you think of 5% of SP 95 in the GO?

In the manual of WV rabbit in America (Gulf) it recommends up to 20% maximum of gasoline in diesel in winter in very cold weather. it goes better in the filter and it starts better
a simple fuel heater corrects these problems.
Andre

Thank you André! your presentation was very clear!

Where I am very surprised is when you tell me that a diesel engine can (accidentally) run on diesel, I thought it would have a devastating effect on the injection pump and of course on the engine ... if I follow you, there is no danger of engine failure, but I suppose it must "hit hard" with a terrible performance?

Can you tell us about it?

Greetings to you and to all the brothers in Quebec who read us (the others too, of course)

Sincerely, live from the flat country, Lietseu

[Lietseu]

Hello
Do not think that when you mix gasoline in gas oil that gasoline or acetone arrives whole in the injectors they are diluted in gas oil and form a product, it modifies its cetene index.

Andre

I follow you on most of your post, but for the dilution of the essence, I doubt

The essence is miscible in GO because it comes from the same basic product, but you will not change the molecular composition of each product, otherwise you would need a thermal or other reaction

This is the reason why the addition of a relatively small percentage of SP95 petrol in the diesel fuel allows a faster spraying of the droplets in the room and gives this spectacular result: around 3 times less emission of soot. https://www.econologie.com/forums/economies- ... 1-140.html

Hi Captain, uh the dilution, it sort of "drowns the fish"! no?
Even if there is no chemical reaction, the gasoline molecules are found scattered around in a "GO molecule cloud, right?

What worries us therefore is that after a certain level (the 20% that André tells us about) the number of its molecules is numerous enough to create "disturbances" of combustion of the detonation-style - instead of - the explosion. .

For my part I am amazed at this proportion of 20% which is in my opinion a very good limit ... dangerous limit (hence my question above to André)

As I told you, yesterday, the test is underway for me, results will follow!

Greetings

[Other]

Hello
The Rabbit manual dates from 1979
it specifies "to mix regular gasoline with diesel fuel
use as little as possible 20% to 30% of the filling volume depending on the temperature. >>

Attention it was the old diesel so with more sulfur and its lubricating qualities for the pump was superior to the new diesel
If you are to increase the dose of gasoline in the new diesel, think of including oil, this diesel looks more and more like kerosene.
To make good tests it is necessary to do them on continuous distances, warm engine if possible of one to two hours of road
and make it repetitive to have meaning.

Andre