Corax, this piston pounder burns Jet-A1. Available from your friendly local fuel bowser.

Martin, with latest gen Fadec this system will be single control. Besides diesels don't need carb heat. ;)

There will never be a piston diesel engine that will have the power to weight ratio of a current helicopter turbine engine. Aviation diesel engines are only practical as an option for avgas burning piston engines.
Since the objective published 6 years ago was primarily to reduce emissions by improving specific fuel consumption, by burning to fuel at a much higher temperature, the investment should be in the greater use of ceramic materials in the combustion and turbine sections of all gas turbine engines.

This V12 engine has existed for a couple years. I had a chat with the company back in 2010. The engine was 6.1L (86mm bore x 88mm stroke), and they quoted an MCP of 480hp. It might be the same engine.

http://www.red-aircraft.com/wp-conte...04/red_A03.jpg

While a DI turbo diesel recip engine would definitely give excellent SFC, there are still some other issues to consider. The installed weight penalty of this complete engine system (including plumbing, heat exchangers, etc.) vs. a turboshaft engine is quite substantial. A recip turbo diesel engine would also require a heavier duty drivetrain to handle the cyclic torque impulses produced by the high combustion pressures. This engine would be quite expensive, and I could imagine it costing well in excess of $100K.

The project seems like an interesting engineering exercise, and the engine design seems to be well thought out. But the reduced SFC is not enough to justify the current weight penalty of the engine installation. We should also consider that the TE and SFC of small turboshaft engines is rapidly improving, thanks to better materials, improved compressor/turbine designs, and higher cycle pressures. So the turboshaft will likely continue to be the engine of choice for light helicopters.

Riff,

Don't think it's the same engine, looks like a Mercedes derived aero engine(?). I'm impressed that the flight test is in a YAK-52: Those wings are relatively untwisted, which means it will be capable of flick rolls (spin entry under gee loading from say a 60' bank with tip stall that washout is normally there to reduce) so that first flight was just a gentle look-see. When you consider the problems that Thielert had with the gearbox before handing the concern on to become Austro AE4, you'll understand what I mean. That prop will generate impressive gyroscopic torques. Being a V12 should help keep crankshaft torsional vibration down, but it would not suprise me if TV was why TEOS/Airbus picked a V8 for Ironbird.


Gemini,

What you say is all true: AvTur diesel can never hope to match turbine for power-to-weight. But the benefit is that you do not have to rely on exotic materials, coatings or casting processes like you need with turbine first stages. This translates to reduced operating costs because overhauls can be less extensive, which combined with the fuel burn then reduces costs-per-hour. The RR300 developed from RR250 for the R66 was specifically designed to remove axial stages for reduced overhaul costs. The next step is to consider combining piston high pressure stage with turbine low pressure stage to get the best of all worlds: low weight, low cost, good efficiency...

Diesel engines in the air is not really new. In the mid 30'ies, JUMO 205A diesel had 867 Hp at 595 kg.. They where used in Dornier and Blohm & Voss machines.

Graviman,

If my memory serves, the Rakhlin V12 was a derivative of the Audi V12 TDI engine. The engine was re-engineered to lighten it, replace the chain cam drive and accessory drives with gears, replace the turbos, etc, and TEOS may have been involved with that effort. I did a quick check and Rakhlin is proposing a price of $170K for this engine, which is about 75% of the $225K price of a new 250-C20 turboshaft of similar power.

I also liked your comment about putting a high-pressure recip combustion stage between the turboshaft compressor and turbine stages. Garrett did quite of bit of work on this type of engine back in the 80's. Pratt & Whitney has also been working on a similar approach using a Wankel rotary combustion stage.

When I went to Robinson's safety course in 2010, Tim Tucker said before they decided to put a turbine in the R66 they tried to come up with a diesel engine to run in it but the numbers were not good, in others words too heavy per HP produced!

Just comparing, a Lycoming IO360 engine is rated at 290 HP and weights about 270kg, the RR300 turbine is rated at 300 HP and weights about 90kg. Usually diesel engines are heavier than gasoline ones.

Perhaps the aircraft diesel engine designers will benefit from a talk to Mazda about their new SkyActiv-D low compression diesel engines.

By lowering compression to 14.0:1 and by initiating earlier injection of fuel (BTDC as compared to TDC in regular diesels), Mazda have been able to produce a diesel engine that performs more like a petrol (gasoline) engine.

The weight savings in the design of the Mazda SkyActiv-D engine are substantial, with many major components being lightened to the order of up to 25%, as compared to conventional diesels.

The additional benefits of the SkyActiv design are better fuel economy, reduced emission levels and more responsiveness.
The SkyActiv design includes Variable Valve Lift, and twin, two-stage turbochargers, that are all proven principles, that produce the best performance out of IC design.
Building NA diesels is a waste of time, diesels have to be turboed to extract maximum efficiency from the diesel principle.

MAZDA: SKYACTIV-D | ENGINE | SKYACTIV TECHNOLOGY

Riff, read your paper: wow!

Looks to me as if the only reason this didn't happen was because of the diffculty in convincing investors of the market. Maybe that's about to change...

Soave, Frank Robinson himself admitted that at an RAES conference I attended. The difficulty here is that you don't want to take on a new engine in a new airframe - that really only left him with the diesel engines that were in the market place at that time. Post their LeMans endurance racing experience TEOS obviously gained enough practical design experience to convince Airbus to consider an EC120 prototype.

Onetrack, the bit that auto marketing men aren't telling you here is the common rail pressure that you need to more or less vapourise the diesel on injection - I'm told that 3000bar is probably where they need to be. The real problem is that a helicopter engine must reliably chug, whir, or hum away for at least 3000 hours before major overhaul. If competing with turbines then 10000 hours is the mark. The fuel injection system tends to be one of the main limiting factors to that TBO, so you can bet your bottom dollar the aero engineers pour over the reliability data before even mentioning the word "certification".

Edit: Just noticed that last paragraph did not make it clear that Jet-A1 has less lubricity than pump diesel.

A pal from the Emerald Isle's tells me he can supply Diesel at Half price, now that would make things a lot cheaper or should I say Lower Cost!!

Peter R-B
Lancashire

Graviman-

The results from that 1985 Garrett project were pretty impressive indeed: 2.3 hp/lb wet installed and an overall BSFC of 0.33 lb/hp-hr. Here's a link to another paper of a trade study Garrett did. On page 7 there is a comparison between notional 1000hp turboshaft and compound engine drivetrains operating at 4K95F conditions. Over a 2.5 hr flight the combined weight of the engine, fuel and fuel tank is 16% lower for the compound engine.

The Garrett project results are even more impressive when you consider that all of the testing was done using circa-1985 commercial mechanical diesel injection equipment. The DDC unit injectors used could produce injection pressures around 1200bar, but they did not provide accurate control of injection timing or duration. As you pointed out, just imagine how much better this compound engine would have performed using a modern 3000bar, high-frequency, direct drive piezoelectric, digitally controlled, common rail injection system.

As for your concern about the durability of such an injection system, they are used widely on modern production automotive diesel engines and provide extremely reliable service for well over 150K miles. 150K miles of highway driving would be roughly equivalent to 3000hrs operation, which would seem to be acceptable for current commercial rotorcraft service.

It would be great to see someone pick up where Garrett left off with this concept.

Riff,

Thanks for that paper. Agreed it would be great if Ironbird taking to the sky kicked off new R&D to examine whether a modern incarnation of CCEP could generate the same level of improvement as CCEP is over the Napier Nomad (arguably first of the kind).

Perhaps I was too quick to dismiss Onetrack's mention of the Mazda approach. Certainly fuel systems able to handle kerosine are available for diesel engines, so it is not too big a leap to envisage a 3000 bar system able to cope with kerosine. The other thing to bear in mind is that diesels are efficient because of the high peak cylinder pressures, but there are other methods to reduce weight. For my money Steyr have been pretty close to the mark by avoiding a head gasket in their monoblock designs. It's no surprise that the M16 was selected by Austro for an aircraft engine (my initial thought was TEOS must be using the Steyr part bin):

http://www.mackboring.com/images/steyr-2-small.jpg from http://www.mackboring.com/Commercial..._Features.aspx

SAE papers on Steyr monoblock:

Steyr Monoblock High Speed Diesel Engine Family Powerful, Cost Effective, Compact, Low Noise, Ware-Resistant and Fuel Effective
The New Generation of High Speed DI Diesel Engine with High Specific Power and Durability

Graviman-

The first thing Garrett did with their CCE project was establish a baseline using the Nomad. Then they conducted numerous trade studies to determine what approach was optimum for cylinder scavenging, compressor/turbine arrangement, balance of work between the piston and turbo machinery, etc. Garret determined a uniflow (scavenge ports in the cylinder walls and poppet exhaust valves in the head) 2-cycle CI diesel core with an effective compression ratio around 8:1, combined with a single stage turbo compressor for scavenging/boosting, and a free turbine stage connected to the crankshaft by a gear set for power recovery, was optimum. The Nomad used different engine and turbomachinery arrangements than this.

A monoblock construction like Steyr's is an excellent choice for a high-pressure diesel, since it addresses many of the structural and heat transfer problems these engines face. There have also been significant recent improvements in piston rings, cylinder liner coatings, journal bearing materials, and lightweight forged steel pistons that would provide adequate service life when operating at peak cycle pressures well above 200bar. This may not have been possible just 10 or 15 years ago. But as you noted, the way the CCE achieves high efficiency is thru high cycle pressure ratios, so these developments are important.

Lastly, a 4-cycle turbo diesel would have lower thermal loading on the engine components than a 2-cycle compound turbo diesel, so it would likely have better durability. But the 4-cycle would also be heavier, and this is a significant concern for a rotorcraft application.

TEOS POWERTRAIN ENGINEERING - Diesel aircraft engine

Iron bird testing:
http://www.teos-engineering.com/mbFi...ngineering.jpg

Not the V8 AE440, but another TEOS V12 aircraft engine:

http://www.teos-engineering.com/mbFi...ineering-1.jpg

Safe to say that a lot of people are watching this one to see if it points the way for an industry shift...

Diesel H120 finally flies
http://i.imgur.com/v82SmFO.jpg

I/C

Diesel Copter!
 

Well done to all involved. This is a very interesting and important development and I hope the program continues to make useful progress.

CRAN
:ok::)

I doubt they will move anywhere with this. They probably just had to get it to fly in order to get their share of the €1.6bn budget of the clean sky program. It will fly for a couple of hours then will be moved to some museum or EC lobby. Then the project department will be dissolved, probably having created a respectable profit drawing public fundings...

Woulda been more sexier if they ran a set of exhaust manifolds out the side like a hot-rod.

Without looking I guess you could mistake it for a Ford Transit van when it's idling :E

I am following this project with great interest and hope it becomes viable . Why no video of the flight and i wonder how it sounds from its twin turbo v12 engine . From the picture the exhaust looks to emit very clean exhaust fumes .

There's video of it flying in the link at post 34. Can't really tell over the musical packing but sounded OK.