Diesel in F1?

[F1_eng]

I wasn't making the point about inertia loads riff raff, I was replying to a comment by Chris that I had ignored dynamic streeses, of which he mentioned inertia.

I agree that combustion aids in reducing inertia loadings, there is no denying that. The only point to mention is that combustion pressures overall increase slightly with speed but the increase in inertia forces with speed increases at a much higher rate. The reduction in inertia force due to combustion on say a formula 1 engine is very small compared to the actual inertia.
I gave a presentation on the effects of combustion on inertia loads and how they contribute to overall piston-sidewall friction a few years ago. You can have a look at some of the content if you want, i'd have to take some company things and some of the formulas out though.

[adam2007]

forget diesel who wants to be waiting on the throttle all the time.

they should have

3.0 petrol -2000bhp limt (what ever things u want to use to achive that, i.e turbo,variable valves wotever)
full areo fremdom
a budget cap

[tok-tokkie]

F1_eng,

You are correct when you say that reversing inertia loads can predominate in a very high speed race engine. But these inertia loads only really affect the conrod structure and rings. The most likely point of failure in a modern F1 engine, even with pneumatic valve springs, is an intake valve bashing a piston.

A highly boosted diesel engine has a much worse combustion pressure and thermal load condition on the piston structure than a N/A gasoline race engine. Even though the diesel runs at much lower revs than the gasoline F1 engine. Plus, the higher peak cycle pressures in the diesel produce much greater torsional stresses in the crankshaft, and require much stronger gears and components in the transmission.

As for the rod structure and bearing inertia loads, the N/A gasoline race engine has a lighter piston and rod, but revs higher. The highly-boosted diesel race engine has a heavier piston and rod, because it has much greater peak combustion loads. But the higher combustion and intake pressures acting on the piston also help to relieve those inertia loads.

Finally, the point that I haven't seen discussed yet, is that diesel fuel has a much better energy density than even gasoline. Couple that with the more thermally efficient combustion cycle possible with a CI diesel engine.

Regards,
Terry

This discussion is way over my head but I am following it with interest, & some confusing learning is taking place.

f1 eng wrote this earlier

The different in gasoline 44Mj/Kg to diesel 45Mj/kg is very slight but it is said you can use less of it.

That hardly agrees with the bit of this post that I have 'bolded'

The other bit I have 'bolded': But on the exhaust stroke there is insignificant (?) pressure to resist the inertia loads so at that stage the diesel must be much higher loaded than the petrol I would have thought. So to at BDC on both strokes when the inertia loads ar very similar to the TDC case.

[xxChrisxx]

I wasn't making the point about inertia loads riff raff, I was replying to a comment by Chris that I had ignored dynamic streeses, of which he mentioned inertia.

I agree that combustion aids in reducing inertia loadings, there is no denying that. The only point to mention is that combustion pressures overall increase slightly with speed but the increase in inertia forces with speed increases at a much higher rate. The reduction in inertia force due to combustion on say a formula 1 engine is very small compared to the actual inertia.
I gave a presentation on the effects of combustion on inertia loads and how they contribute to overall piston-sidewall friction a few years ago. You can have a look at some of the content if you want, i'd have to take some company things and some of the formulas out though.

I need 5 posts to pm you, but i'd be very intersted in looking at what you've got. I did engine modelling for purposes of design for my thesis.

It had a fair amount of detail, but I was never truly happy with it becuase I had virtually no data about the engine to start off with and they assigned no money for practical testing. I just made the best of what I did have though.

[F1_eng]

What sort of modelling was the context of your thesis?

The notes I could give you would be simplified because the development of equations and formulae I did during the work is property of the company I worked for unfortunately. It still outlines some interesting points that you wouldn't really consider without looking at some factors in detail.

[xxChrisxx]

What sort of modelling was the context of your thesis?

The notes I could give you would be simplified because the development of equations and formulae I did during the work is property of the company I worked for unfortunately. It still outlines some interesting points that you wouldn't really consider without looking at some factors in detail.

I used matlab to develop a model for acceleration of the reciprocating components (simple stuff really) and developed my own gas pressure force diagrams by adding losses to an ideal air standard cycle. This vas then validated against the rated power output. So technically the analysis was only valied at that rpm, becuase the gpf was based on a single bmep value.

the above was done to get a load case for FEA analysis.

The problem was it was a vintage engine, I had the block, crank and rod/piston and not a working angine. The idea was to then use what information (basically a power output, an rpm and the geometry) a I had to develop more info to make infomed design decisions for converting two 4 cylinder engines into a V8.

[Ciro Pabón]

Oh my. I understand that purists can find flaws in the simplistic I made, but...

"You pack more air into the combustion chamber, you use a fuel with higher energy content, so you get much better torque."

It is not always the case, the limiting factor generally with gasoline it the throttling wich dictates air intake so at full throttle and moderate engine speeds, a gasoline engine volumetric efficiency would be more optimised than a diesel engine.

It escapes me what volumetric efficiency has to do with anything said, but it depends little on the kind of cycle and much more on the valves and manifold you have. What volumetric efficiency has to do at all with engine efficiency also escapes me. All I intended to say is that density of oxygen is larger when compressed three times more than in a gas engine.

I never said diesel had larger volumetric efficiency, but the air is more dense because is compressed. The fuel burns better because it's easier to "find" an oxygen molecule: they are packed together. Simple.

"That is quite an achievement in an endurance race because a Diesel engine is more "stable" than a gasoline powered one: you pay your price in designing for high stresses, but the engine you get works at a slower pace."

What does this mean???

Absolute rubbish, the extra "punch" you put in does not equate to the ruduction in speed endured.

It means that you can have an engine that produces more power per stroke at lower rpm. You change rpm for torque. A diesel engine of the same power of a gas engine will invariably run at lower rpm, with a larger torque, that's one of the basic tenants of diesel engines. It's also the cause of them being used in stationary power plants, ships and heavy equipment, with long hours of continuous use. That, and because using less fuel for a given output, they are more efficient.

You do not want to compress "only air" as the combustion process a diesel does require time to go through the different phases

On the intake stroke, a diesel engine draws pure un-throttled air into the combustion chamber. There is no fuel mixed with the air, as there is in a gasoline engine.

How is "Otto" limited by atmospheric pressure?

Because atmospheric pressure is what push the air into the cylinders. If you lived in a planet with twice the atmospheric pressure, you could push twice the air into an identical ICE.

Besides, diesel engines are throttled by limiting the amount of fuel injected, which cause they being leaner, while gas engines are throttled by limiting the intake pressure. This consideration is the base to deduct the theoretical efficiency equation for a gas engine I showed. Duh.

There's also mention of the flame speed causing detonation which is blatantly incorrect, it is related to the un-burnt zone conditions. The shock-waves are a side-effect of detonation, not a cuase.

I wonder where did I mentioned what's the cause of detonations. I said it's hard for detonations to occur in a diesel engine and much more easier in a gasoline engine. I mentioned what makes a detonation different from an explosion and from a deflagration and I KNOW what I'm talking about, I've blown a lot of rock for roads and I'm certified to use explosives.

More the point, Diesel engines work by diffusion burning, gasoline engines work by flame propagation. That's the key for Diesel not detonating. How can you talk about flame front in a Diesel engine I don't understand. Perhaps pride equals ignorance?

[WhiteBlue]

Under heavy loads the bearings doesn't last if you make the engine turn fast. The life of a bearing depend exponentially on the rpms it withstands and the load it has. Diesel imposes heavy loads on moving parts. For example, I can attest that a big block 502 engine can run all your life at 2,800 rpm, but run it at 3,800 rpm and you can kiss it goodbye in 500 hours. So, you need a really good gearbox, because the engine doesn't rev up too much.

I just wanted to add that modern engines use hydodynamic bearings which encounter less wear the faster they rotate. The reciprocating bits are causing the problems with revs and as explained several times the injection, gas and combustion dynamics.

[xpensive]

I just wanted to add that modern engines use hydodynamic bearings which encounter less wear the faster they rotate. The reciprocating bits are causing the problems with revs and as explained several times the injection, gas and combustion dynamics.

While it is true that a hydrodynamic bearing's "wedge-effect" becomes more pronounced at higher speeds and in theory gives a thicker oil-film, that is only the case if you are dealing with full-film lubrication, which it rarely is in an engine.
Reality is that there is always a degree of boundary-layer lubrication with occational metal-to-metal contacts and this is why you typically match a softer bearing surface against a harder.
The fact that viscous friction, and therefore oil-temperature, is increasing with the square of the speed doesn't help either.

As for the direct load on the bearing, this is supposed to be largely absorbed by the "squeeze-effect" on the oil-film, but it's the same problem there, the film is rarely perfect.

[F1_eng]

Ciro Pabón, I wouldn't usually rise to this but I have some free time on a sunday morning so I will.

"It escapes me what volumetric efficiency has to do with anything said, but it depends little on the kind of cycle and much more on the valves and manifold you have. What volumetric efficiency has to do at all with engine efficiency also escapes me."

Volumetric efficiency is the measure of an engine's efficiency with regards to filling it with air, that's what it has to do with engine efficiency. It allows you to compare the efficiency of engines of different sizes at filling the cylinder.

"On the intake stroke, a diesel engine draws pure un-throttled air into the combustion chamber. There is no fuel mixed with the air, as there is in a gasoline engine."

Are you seriously telling me how air is inducted in a diesel engine? I really do not need this. This is an area that could be utilized to improve the efficiency of the cylinder filling by using the fuel to cool the incoming air. This in turn then decreases the input energy required to heat the fuel directly through the compression process.

"Because atmospheric pressure is what push the air into the cylinders. If you lived in a planet with twice the atmospheric pressure, you could push twice the air into an identical ICE.

Besides, diesel engines are throttled by limiting the amount of fuel injected, which cause they being leaner, while gas engines are throttled by limiting the intake pressure. This consideration is the base to deduct the theoretical efficiency equation for a gas engine I showed. Duh."

Otto is limited by atmospheric pressure, exactly the same as any diesel engine without a super/turbo charger. I'm not sure what you are trying to say with the last part.

"I KNOW what I'm talking about, I've blown a lot of rock for roads and I'm certified to use explosives."

That is irrelevant, combustion within an engine is different to other explosives. You might know what you are talking about but not able to explain it very well.

"More the point, Diesel engines work by diffusion burning, gasoline engines work by flame propagation. That's the key for Diesel not detonating. How can you talk about flame front in a Diesel engine I don't understand. Perhaps pride equals ignorance?"

Where in my post is there mention of flame front with regards to diesel engines? I have had a look and couldn't find any.

My post correcting your errors are getting shorter each time, this means eventually all of them might be corrected.

Hearing a term which is related to a topic then putting it in to google and trying to interprite the results does not mean you should be teaching other people about the terms used.

There is a saying: a little knowledge is a dangerous thing.
I think it's very relevant in this instance.

[Jersey Tom]

I think what F1_eng is saying is we should just use NOS.

[Ciro Pabón]

Volumetric efficiency is the measure of an engine's efficiency with regards to filling it with air, that's what it has to do with engine efficiency. It allows you to compare the efficiency of engines of different sizes at filling the cylinder.

Engine efficiency is thermal efficiency. I assume you know that volumetric efficiency serves to compare engines as air pumps, not to compare them in regards to produce work.

Surely they are related somehow, but the things that give an engine its characteristica engine efficiency is the kind of thermal cycle. It's like saying that all tall men are fat men: sure they are related, but other factors influence more if you are fat or not besides your physical stature. And, pleeze, you DON'T need to explain to me what VE is, either. I repeat: I have no idea why you mention it, I'm not saying I don't understand what it is.

However, now that is a Sunday, could you ellaborate about two things? Why are you mentioning VE in a discussion regarding diesel vs gasoline? In which way VE is related to a thread about diesels in F1? As I said, the valve size and manifold pressure is what influences VE the most, period.

Sure your posts are getting shorter, I still haven't comprehended very well (with all respect) what your point is. Aren't diesel engines leaner on fuel? Detonations aren't faster than sound? Aren't Diesel engines more reluctant to detonate? Aren't Diesel engines low revving and easy on bearings? Aren't Diesel engines used when endurance is needed because of its high torque/low rev combination? Isn't Diesel oxygen density double or triple the one of a gas engine before combustion? Doesn't that mean that a slow burning fuel, like oil, can be burn in a much more efficient way than in an Otto engine and thus doesn't it make them have a thermal efficiency better than gasoline ones? Aren't fuel throttled engines leaner than air throttled ones?

No babbling about VE will make those points untrue and emminently related to this tread.

I can say that I'm still surprised by the tone of your posts. We're used here to correct each others posts (if that is the case) without having to call ourselves morons or qualifying the quality of knowledge of every one.

The aim of the thread is the use of Diesel in F1, I think, so, please, if you find so displeasing and limited my posts on the subject, by all means, dazzle us with your illimited knowledge about the point at hand, instead of saying that something is wrong but not explaining why

I complain about you entwining the conversation by putting in my mouth things I didn't say and then rebating those non-existent points of view. I learned about the point at hand in the same way you did: in college. Assuming that I learned them in Wikipedia is insulting, to say the least. I may be more stupid than you are, if that's what you mean, but I haven't studied less than you.

If I had a moderator I could complain about that, I would. Unfortunately, I'm the mod here, so I have no one, except you, to complain about your lack of education. I'd love to hear your answer about that point, now that is a Sunday...

[F1_eng]

"Aren't Diesel engines low revving and easy on bearings?"

They are lower reving than gasoline.
Certainly they are NOT easy on bearings!

In the comparison between diesel and gasoline engines, for sure VE has a place. Torque is proportinal to VE and the major difference is in the torque characterictics.

Overall, even considering the lower opperating speeds of diesel engines, stresses are much harder to deal with.

Regards

[Jersey Tom]

Ahhh the old intellectual masturbation / pissing contest.

I am curious though. What is your job function, F1_eng? Or what have they been?

[xpensive]

Ahhh the old intellectual masturbation / pissing contest.

With the moderator at that, fantastic! Go go go!