yr right - By hymomics, I presume you mean harmonics. What adverse harmonics does a CI engine possess, that a SI doesn't?

Every driven a desiel and then a petrol car what's the difference. The rattle is the firing which give the proplem. They not a smooth engine on firing.

Which leads to something I just thought of. When we balance props we use accelerometers. These pick up the bad vibes in the engine. Not sure they will work on theses engines but

The Austro Engine is certified to run on EITHER JetA1 (plus 2 dozen or so equivalents depending on your countries preference) alongside pump diesel. Add to that the economy you get from them, plus the longevity of the core engines and you've got the undeniable future for all light aircraft applications.

The V1 twin turbo diesel Diamond does 190 kts at 28000 feet burning a total of 36 litres per hour. or 18 litres per hour per side. (Coming from the mouth of Austro/Diamonds ferry pilot himself) Although the airframe is only certified to something like 18000 feet.

Austro are aiming for a 5000 hour TBO and are projecting an unlimited TBO into the future as their condition is constantly monitored via oil sampling at every service by the manufacturer.

They are also working on a number of larger applications in the 350 hp range which may already be in use by the US military in drone applications.

I've flown a couple of different diesel models on a number of occasions and I can say I was quite impressed with them. As for "ry igrht" comment re vibration I can confirm they are light years ahead of their opposite number in Lycoming. I can't comment on TCM as I've never flown a 4 cylinder 180-200 horse TCM.

In the Diamond twin (diesel), you can have the canopy open with both engines running and still have a conversation with your headsets off. They are that quiet and smooth.

Can't wait for more diesels like the V8 mentioned here are certified and STCable or fitted to production aircraft. Bring em on!

This would have to be the biggest piece of misinformation I have come across lately The rattle is the firing which give the proplem. They not a smooth engine on firing.


An Audi A8 V8 twin turbo diesel at idle is quitter than the petrol equivalent it uses Piezo Injectors that control the flame front with up to 8 fuel pulses and is just delightful to drive I owned one for a time, great car Euro 5 compliant without using Blue Goo.

T28D
SO what are the harmonics from if not the firing pulses?
The Vision 350 innovation allows the fitting of an aluminium propellor, previous diesels could only be fittted with composite blades. Are you refering to flame lift off length, after initial autoignition? As you would know the flame in a CI engine propagates quite differently to that of an SI engine.

YUP As you would know the flame in a CI engine propagates but it is still a predictable flame front or she wont go !!!!!

That takes me back to diesel theory: Lift off, diffusion flame, cool flame soot, oxidisation etc etc. But it also makes that noise or rattle that Yr Right spoke of.
By the use of modern fuels, with better matching cetane number for swirl chambers and cylinder head design, CI engines can now be produced almost vibration free. Note almost, they all seem to have a frequency that resonates, a car can be geared to avoid that RPM

the diesel noise is caused by the ignition delay of the fuel and depends on the amount of fuel injected before actual ignition. If you can get a lot in before it begins to burn, you'll get a rapid pressure rise as it all suddenly goes off together, which is the cause of the knocking/rattling sound.

pilot injections, rate-shaping, or whatever-you-want-to-call-it that the electronically controlled injectors do are all designed to limit the amount of fuel injected prior to ignition.

Having said that, not much of this has anything to do with torsional harmonics, hymomics or any other imagined figment that the propeller sees. It's the compression ratio that pretty much dictates the torque amplitude for a given load/power level

AndyRR Would you like to explain why?

Hard to explain without waving my hands in the air drawing imaginary diagrams, but...

...in simple terms, the net work done is the sum of the (positive) expansion work and the (negative) compression work. If you increase the compression work by increasing the compression ratio (negative torque pulse) you also increase the expansion work (positive torque pulse). The net work done is the same (more-or-less) but the difference between the two (torque pulses) is the amplitude. Hence higher CR >> higher torque amplitude.

Why not go back to radial diesels?

From the link Radial engine - Wikipedia, the free encyclopedia

A new Piper or Cessna would look awesome with a radial up front :ok:

Have you ever seen the engine mounts in a modern diesel car. They huge and not only that they also electronically controlled to smooth out the nvh. this is hard to over come in an aircraft when its fitted with a prop.
And as I recall now I may been wrong but don't they fire via compression, hence the rattle. Now the rattle is the problem as it sets up the harmonics though the whole of the airframe, as I said earlier a TB 10 or 20 was fitted with one and it blew the tail off it as it taxyed back after its first and only test fight, then you have the problem of a prop. Now as I understand they also fitted with a cushion rubber drive to take the pluses out.
In a modern car this is not so much as a problem as weight is not such a primary concern but in an aircraft it is.
Also as I said earlier im not sure you be able to do a prop balance on the airframe with one of these engines,


Cheers

The vibration through the crankshaft would not vary as the pulses stay in balance, unless of course it is a single cylinder.

I read recently that a diesels natural combustion properties mean it runs in constant detonation, hence the traditional clatter sound a diesel makes.

Modern diesel engines have eliminated this clatter by using a pilot injection that comes before the main injection pulse, as well as pulses of fuel injection after combustion has started.

I do no it's mandatory line replacement if you have to crack one open. $$$$$

I just watched that video and while the noise level has drop a hell of a lot you can still hear it with still means bad vibes

That might be true on a multi-cylinder engine with an infinitely stiff crankshaft, however no-one's invented an infinitely stiff crankshaft yet. A radial engine is a close approximation though.

The diesel knock/rattle is in the 5-15kHz range and the engine mounts are not very well coupled at that frequency at all. It's like trying to remove the tail of your TB20 by repeatedly hitting the crankcase with a hammer...

yr right - You're confusing sounds (hearing a diesel clatter) with vibration (torsional and longitudinal crankshaft whip).
Vibration will lead to airframe cracking, noise from the combustion process won't.

The fancy engine mounts in current diesel cars and light commercials are designed to prevent the diesel clatter noise from transferring to the chassis and body via amplification through the engine block, the chassis, and the body.

A CI engine has a longer duration power stroke than an SI engine. The power stroke from an SI engine is relatively short.
This accounts for the much higher torque production from a diesel engine.
The much higher torque level of an aircraft diesel is possibly more of a concern with regard to prop damage/life, than anything else.

The considerably higher compression ratio of a CI engine is what produces the larger rotational impulses as compared to a SI engine.
Most diesels are 16 to 18:1 compression ratio. The much lower compression ratios of SI engines produce much lower rotational impulses.
However, a misfiring SI engine (an exceptionally rare event in CI engines) would produce far greater rotational impulses, than a CI engine ever would.

I think you are missing the point. The rattle is where combustion starts. It's not a clean start to combustion as with a ignition engine. Hence the sound but that sound relates to the harmonics that are produced. When then are produced they travel through the airframe. It dose not matter what the frequency is if it what of a better term hurts the airframe. That's why the props are different and why the tail fell of. In a metal aframe they also produce cracking. They had an engine that was to be able to be placed into 182 etc but that never really took off ethier.

Cheers

Diesel: for _ fuel economy,consistent performance, long mechanical life. virtually maintenance-free if fuel/oill filters and oil are serviced properly, fuel cheap and readily available worldwide.
against = usually heavier, noisier, the need for extensive research, refinement and certification, fuel could "wax" at altitude/cold-soak -because it will happily burn it, doesn't mean it should!

The huge cost of research, development and Certification, for the relatively small volumes of piston GA engines, means the economics are very tight.

Anyone remember the Porsche engine? Robin? (Just 2 I know of)
Thielert was beset with problems, despite having an assured sales-volume .
Jabiru hardly has a stellar reputation in the reliability -stakes.

On the other hand, Where Robin (and others) disappeared from the Microlight market,but Rotax continued development, thrived and has expanded. They now have a very real and potent challenge to the Lycosaurus market.

Lycoming and Continental, having recovered their development and tooling-costs decades ago, must be really hurting....the recent directive on aftermarket cylinders gives a hint of this Complacency, poor quality-control and protectionism is not the way to run a sucessful business!
Meeting the customers' needs and expectations, is, however, a fairly fundamental foundation..

Inevitably, due to the shrinking Avgas market, the future choice will be Diesel (OK, CI ) or Mogas continuing with it's limitations.
I forsee a decade or so of stuff with high maintenance and relatively short life (Thielert) until the engineering refinement gives a whole new era of low-maintenance,affordable GA Piston engines.

I have deliberately ignored Electric....that could change at a stroke with the invention of a light,cheap, high energy-density battery....already, solar cells are edging closer to being practical as an airframe surface-cover....but , although massive leaps forward have been made, there's a huge capability -gap to be bridged.

Just idle speculation from a bystander.

Steve, the Thielert Centuriian 2.0 lives on, part of the Continental Engine Group now.
Piper Introduces Diesel Archer | Flying Magazine

-@ No hoper , Yes, but the burden of all the early development costs was borne by those who lost their shirts, either directly swallowing a pill (taking an unpleasant loss) when Thielert folded, or buying a lemon powered by the troublesome, costly and maintenance-intensive early engines.
the new owner has , really, only the refinement costs to fund. That makes a huge difference to the profitability of the new product and also the legacy engines could well be a cash-cow, as the poor aircraft owner is well and truly caught by the gonads.....pay the ransom-price to keep the engines running, scrap the aircraft or , lastly, go through the process of converting to a different engine and getting certification.
Harmonic dampers are well-established in the automotive world, I don't see any issue with C.I engines for Aviation use...As has already been alluded-to, cold and thin-air are bigger things that could slow progress whilst their potential threat is eliminated.

The balancer wont take the impulse loads from being transmitted back into the airframe it is there to balance the engine some areo engines all ready have a external balancer and are also internally balanced with dampers inside the case. Harmonics are extremely damaging to an aircraft fuselage

This is a design engineering issue. If this issue results in a placard having to be fitted to forbid or limit operation in a specific power range then the engineer needed to be sacked.

Why or what design issue would result in an engine, 0-360 A1A for instance, to be built with such limitations. Why would Thielert engineers allow their names to be put onto a design that fails so expensively?

Harmonics is not a dark art. Why complicate this issue? All we do is discourage any innovation within this industry. Lord knows, regulation has stifled light aircraft development into a multi decade old time warp.

Harmonics whilst not a black art it is a major issue that has to be over come at it's designed phase and the fact that aircraft engines are different to any othe engines that we all use on a day to day level. The fact that you swing a 5 foot prop of the end is we'll maybe an issue one would think ?

OZBUSDRIVER,
RR Alison 250 has an RPM forbidden to tarry range. So too PT6 engines that I know have the same. I think it would be inherent in the rotating components.

It's interesting reading about harmonics and dynamic balancing, and the causes of the "clatter" of diesel engines. All of it new to me!

However, I would like to inject a note of practicality. Torsional impulses, harmonics and so on do not limit the life of the Diamond product, singles or twins. It didn't with the unsuccessful Thielert engine, and (so I understand) it doesn't with the more successful Austro engines. There are no prohibited RPM ranges either, unlike (for example) the old Tobago TB10, with a horizontally opposed four cylinder SI engine.

Re Diamond, you could tell it was a CI engine in two ways. 1) Power almost independent of RPM, and 2) a horrible clatter on shutdown, as the propeller clutch shuddered its way to a stop. That's it. (Ok, and the lightweight propeller.)

Don't mean to put a dampener on the discussion - I'm learning lots - but let's not say "they can't do that", when clearly, they can.

Now one putting a damper on anything. But there is a lot of difference between a low HP engine to something they claim around 350 HP. I put more on later about problems P&W are having at the moment with turbine blades and harmonics

What is Compacted Graphite iron ?

COMPACTED GRAPHITE ENGINE BLOCKS Precision Engine

http://www.sintercast.com/file/docum...er-heads-1.pdf

came across this


Pro Systems - Under The Scoop


carby vs injection


cheers

Good article YR Right

I'll bet you did! :}

Andyrr what you not as clever as you thought you was. Hey the sky is blue. You need to wake up you not as smart as you like us to all think you are. You don't even know basic bgt. Drrrrrr

As I said you can make more power out of a carby. That is unless this guy is me and I've gone and made these carbys and set up a web site.

Instead of insults perhaps you should do some reading and exams and put your time into that instead of mindless posts.

Cheers

That is an informative website yr right.

There is one aspect of aero engine operation that it didn't discuss though: changing air density.

A carburettor engine designed for a wide variety of air densities needs either a mixture lever operated by an expert, or a very complex auto-lean mechanism. In practice these days, manufacturers rely on the first option!

A single-power-lever engine can be operated at the most appropriate f/a ratio at all times, and needs no special expertise outside the factory or overhaul shop. Granted you won't get the theoretical efficiency of a high-end expensive carburettor. But 90% efficiency with no hassles is pretty good for us "get from a to b no worries" types.

I totally agree with what you say about the efficiently of a carburettor. How ever the point was that you can make more HP/torque for a carby. For most application the high end is not required to the degree of what this carby dose. But it explains a whole lot and more the differences between the two systems. Then you can have a pressure injected carby which is an extremely complex bit of kit.
In drag racing now they measure grains of water in the air. It's gone from we'll let's try this to an extreme science to get the lasts tenth out of a machine.

There Arnt to my knowledge any Single lever piston engine aircraft that Arnt fadec controlled. There are however a lot of turbine engine aircraft that are.
The fuel basically in a turbine is ethier on or off. The pilot has no control over fuel other than a power lever. This is all because fuel is computed via air speed and placement of the power lever. In a piston engine aircraft this is extremly hard to do unless the use if electronics is used. Then that makes the system complex and takes away the simplicity of an engine. And the ability for the engine to run with out any electrical power.
It's all a balance in the end.

Aviation is similar to drag racing. How fast you won't to go is only held back by the amount of cash you won't to through at it.

I keep saying fuel is the cheapest thing you can place in an aircraft.

Cheers

Let's be clear. Apart from the fact that yr right can't spot a little innuendo, that article is an opinion piece with no references and no date. It provides absolutely no factual evidence to support any claim. It is as much use as any other "found on the internet" information that's not subject to some scrutiny.

The only thing that carburetors have going for them is they are passive, mechanical devices. Whether they make more or less power on a dyno is pretty much irrelevant because engines are not useful on dynos. They need to be brought into the real world, where atmospheric pressure, temperature, fuel quality and density, wear and maintenance are all, for carburetors, uncompensated variables. So, for aircraft we give the pilot a big red knob to apply a crude correction factor to the whole system.

Unfortunately, so very few pilots know how to correctly use it.

In my opinion, a properly engineered FADEC would be far superior in almost every respect. It could compensate for most of the above mentioned factors and more. The automotive industry has adopted and developed the technology to the point where failure rates causing loss of function are at levels that even the big jets would be pleased with. Alas, with all the regulations that "keep the aircraft in the air" we won't be seeing it any time soon.

At least carburetors make more power on the dyno :hmm:

Let's be perfectly clear. In the automotive world where you can play and change to your hearts content were claims that are made that are incorrect are soon found out and products don't last. It was one article I came across that showed what really happens in the real world as I said very earl in this post. I have not and did not go looking for this but found that some people may find it interesting.
Not everything new is better. To be honest a fadec controlled engine is going to give you what. Sfa. Aircraft engines are as they are for a reason. There are no other production engines that will do what an aircraft engine will do. All fadec will do is take the leaning out of a pilots hands and may and it's a big may give a slightly better fuel use age. That's it.
Not really much of an advantage in the end. The reason why the auto motive industry was the tighten emission controls that have been imposed. A piston engine with spark ignition has a very narrow brand of schicometic envelope. And before you say efi gives better fuel economy yes but only slightly by being able to keep the engine in its envelope closer it the transmission that give the economy as we now head toward 9 speeds in passenger cars.

Cheers

Oh btw. Casa not so long back where pushing that all o/h aircraft engines had to be DYNO tested before release. The industry got together and where able to have it stopped before it was imposed on the industry.

Cheers