What Is A Two-Shaft Turbo? What Is An Axial-Radial Turbocharger? What's better than a sequential turbocharged engine?
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A two-shaft turbocharger is designed to be a solution that allows an engine to produce boost across a wide range of airflow, while being more compact than a sequential turbo set-up. It also allows for high boost levels like larger turbos, but doesn't sacrifice the bottom end torque as much.
What's the secret to a two-shaft turbo? It uses two different styles of compressors. First, an axial compressor forces air into a radial compressor, which then increases boost further. Using variable vanes for both the intake and the exhaust turbines, the turbocharger can provide useful boost across a wide rev-range. It's like the combination of a jet turbine, an automotive style turbocharger, and a variable geometry turbocharger all in one. Sound complicated? Check out the video for full details!
Honeywell Patent - https://goo.gl/1s3tEo
SAE Journal Turbo Article - https://goo.gl/WrXJ9U
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Jason, Can you cover your take on smooth versus rough intake manifold and intake head port finishing in a carburetor or fuel injected scenario? People say the rough surface helps with fuel atomization. I am in the smooth camp saying that the rough surface causes more turbulence slowing the air velocity down.
My understanding of guide vanes is that a spinning fan tends to spin air and the guide vanes redirect it back into the desired direction. It's basic jet engine science. More efficient might be to replace the vanes with a counter rotating fan blade. Theoretically double the air could be pushed at the same RPM that way. I always had a problem with jet engine stator vanes. Stator meaning stationary. Why would you want to carry stationary weight in something so dynamic. And why wouldn't you want to make it twice as hard to max out the bearings.
I did not hear you mention clearly the main purpose of the dual shafts, which is to allow the compressors to spin with a different speed, which in turn make a possibility to use those vains, that farther modulate the speed.
I like having a VGT on my truck (Detroit Diesel) because I can use light throttle to spool the turbocharger before a hill without using as much fuel. I can see how this Honeywell/Garrett design would be useful.
Is it possible to use a 'SUPER-CAPACITOR' as sort of a TURBO-CHARGER for a battery powered Tesla automobile?
Teslas have 'Ludicrous Mode', but the amount of current being supplied to the motors is limited by the battery construction technology. Having a large super-capacitor would allow the battery to charge up the capacitor and then when that sudden BURST of power is needed the capacitor can deliver that boost of current much better than a battery pack can.
How to hold the oil in?
Something needs to hold the inner turbo shaft in place, so it does not move back and forth and it still needs to seal oil.
The outer shaft needs to be ekstra large to allow the inner shaft, leading to lower efficiency then a regular turbo.
The bearing part of the turbo is generally the smallest part of the turbo, if this part is made bigger to allow 2 shafts and a longer turbo shaft with ekstra fan, the packaging could be worse then 2 normal turboes.
I have never seen this kind of turbo used anywhere, so the patent could just be a shotgun patent, shooting at something and patent all the idears hit by the shot.
Hello Jason great video thank you for your work, it’s greatly appreciated. If you have a video explaining engine oil thickness regarding the weather heat if you could use alternatives from the owners manual recommendation and car age that I have not seen, could you give me some advice or link the explain art video please?
Also, have you considered doing more Diesel engine videos? I am from Panama and I own a 2005 Rexton; not only the 2.9l diésel engine but the vacuum system to enable the 4x4 feature I would like to understand.
Thank you again for the great videos and for your time, regards.
I can't wait to see how small the intercooler between the 2 compressor stages is, and how, at such a small size, it has any kind of efficiency or flow at all... It will have to be liquid to air though....
I wonder if this enables the centrif to operate shock free compared to a single stage radial. If so, this would maintain a somewhat simpler design of the impeller and low manufacturing cost while also increasing it's thermal efficiency across the speed range. My guess is that the inlet experiences very good uniform flow circumferentially which helps.
For those who may ask about the two shaft design, it must be due to have two different spindle speed on the two shaft, it does increase the efficiency of the compressor compared to a one shaft design ( this is used in the most recent airliner jet engine).
It sounds a lot like the mechanics of a turboprop engine sans the combustion. Probably not used in cars because there's more efficient designs; and the focal point for more power is in the volumetric efficiency of the engine itself.
When I read two shaft, I thought this was going to be a video on twin radial compressors. I wondered how they were going to feed the second radial turbine without stalling or reducing the efficiency of the first radial turbine. Axial and radial compressors combined makes sense. They do that in some jet applications. Generally, it is not favored because it doesn't help with compactness, so most jets just opt to go for an axial only compressor. But in this application it sort of makes sense. My problem is making the turbo 2-3" longer. Turbos already barely fit in most engine bays. Why would an auto manufacturer sacrifice even more space for little benefit?
I think the answer to your question is because there is significant benefit, and yet with a small sacrifice in space (it's not two turbos of space, but more power than a single turbo, with a wider range).
I work at Honeywell and of the turbos that have had this design, the issue is with bore-through wheels. Mainly compressor wheels as our manufacturing process would cause minor imperfections within the bore which caused stress fractures at speed.
Isn't twin-scroll doing something very similar? Just that it has centrifugal sections rather than one being axial, and some way of bypassing a section so it spools up faster on moderate load. At least that's what my understanding was.
Since on the subject of turbos why not do a pros and cons of installing a twin turbo set up where turbos are mounted behind the rear axle and no need for expensive turbo manifolds or exhaust piping or even K-members on mustangs to fit those expensive headers.. boost would be much lower then traditional turbos but the cost would be far less then even a traditional single turbo set up
I have a suggestion for a video. Compare a twin turbo V8 or V6 configuration where you take 2 identical engines and use Twin turbos on the first engine and 2 mirror image turbos of the same size on the 2nd engine. I've read that the mirror image configuration will make more power. I know that this is probably due to the exhaust plumbing being balanced between the right and left cylinder bank. But I wonder if merging the compressed air from opposite rotating impellers yields a higher boost than with 2 clockwise rotating impellers at the same RPMs? I suspect there may be a slight advantage with the opposite rotation pair. But that is just a guess. And If this is true, then I am thinking you could get the same benefit by using 2 clockwise turbos and mounting one facing forwards and the other facing backwards. Of course this would throw off getting any kind of balance in the plumbing between your right and left cylinder banks and thus, defeat the purpose of doing this in the first place. I just realized that opposite rotating impellers might yield some type of gyroscopic effect, but such effect may only be on steering the vehicle, and not on boost. This would be of no benefit in a car, but if positioned correctly, could give some desired effects on a motorcycle. Maybe that could be the subject of another video.
I assume you mean sequential turbos in the traditional sense as used in the Supra and others? Because the comparison that comes to my mind is the use of compound turbos in diesel engines where the exhaust from the first turbo drives the turbine of a second turbo, which turns a compressor that sends boost into the compressor of the first turbo.
The radial type Turbo charger has its roots in WWII aircraft engines. We used them in our high altitude Fighters and Bombers. The best example of this was in the P47 American aircraft, where the normally 2000 hp R2800 radial aircraft engine was boosted to 2500 HP. And the other is the Rolls Royce Merlin used in the later P52 Mustangs. In fact the early Allison engines were higher performing Angie's that's the Rolls Royce Merlin when naturally aspirated, but the British Supercharger, which was a radial design,far out performed those of ours. The ideal situation would have been to marry an English super Charger to an Allison engine, but politics kept that from happening. Later on, Frank Whittle's jet engine used a radial designed compressor in his jet engines. These were used by the allies for years. But the German ME 262 used an axial flow compressor in their engines, which is far superior to the axial design. We started using the axial design in our later Mach one plus Fighters and in our later bomber and passenger aircraft, and today there are no axial compressors used except in automotive applications.
The extra mass of the axial turbine will represent a performance compromise/cost that, perhaps Honeywell don’t want to openly discuss.
That compromise will manifest itself as lag and/or spool up delay.
The only way to properly compare what the true benefits and/or downsides of the design are, is to plot boost pressure against exhaust turbine pressure and/or crankshaft rotational speed and/or time.
The additional turbine is not a bad idea.
But Garrett know (whether or not they openly admit it in their literature) the 2 shaft (or dual compressor turbine) turbocharger concept - compared to any other turbocharger with the same exhaust/compressor turbine geometry - *trades off additional boost for a delay in compressor/turbine shaft acceleration times; which means more lag and/or spool up delays.
Essentially this is why most European car/engine manufacturers use a similar concept of another in-line (axial/other) pre-compressor, but power it with electrons, not exhaust gases.
That way the *above-mentioned trade odds are almost completely removed.
I do enjoy your videos. I especially like how you supercharge your Honda S2000. A lot of what you say in your videos goes right over my head. I'm more of a Hands-On learner than a book learner. You reminds me of a lot of Kevin Cameron of Cycle World magazine he always would write engineering articles in Cycle World magazine. Now, he is getting older but still writing he has put out some YouTube videos. I would suggest giving some of his past articles I read if you can.
Sounds good on paper, does it really produce extra 20-30% extra boost? I am thinking whatever method you use, if all the exhaust energy (or force) were used to turn the turbin, you will not gain anything? Unless it was not as efficient to capture all the energy as the dual shaft?
Such a cool idea to extend the compressor map of a regular turbo.
As you mentioned in the video, a lot less complex than a twin turbo set up.
I have a Nissan Navara (Frontera) 2.3TT diesel and there is an awful lot going on just driving down the road.
Yes it works, and makes a broad spread of torque from around 1200rpm up, but it's very complex.
Neat, never heard of these. Closest to them I was aware of are compound turbo setups where you use a big turbo feeding a little turbo. Exhaust flow goes from cylinder head to the little turbo then the waste gas and waste gate bypassed exhaust feed the big one. So that way the big turbo can increase the PR to the little turbo. You get a very responsive setup with insane low end torque and power to redline. Maybe you could do a video on compounds like this, because most people don't seem to know about it.
YouTube turbine mechanic AgentJayZ would disapprove of your description of the variable state vanes, unless they are actually supposed to be inlet guide vanes. His videos on turbo machinery operation and theory are well done.
You have the two types of compressors labeled as Axial (Jet Engine) and Radial (Turbo/Centrifugal Supercharger), but the latter is also used for jet and turboshaft engines. Early jets commonly used centrifugal compressors and they're still common in turboshaft helicopters today.
That Honewell turbo could be called twin spool with variable stators.
On another matter not unrelated, the 1st 'mans' jet engine was the J79. It was such a mechanically correct design that many are still in use today. It has variable stators and is of single spool design. There is a youtube video of a bloke with a cutaway j79 motor explaining the operation and gas flow. It is a short video and very informative.
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