Crazy throttle idea

[cyberface]

I had a random crazy idea recently and wondered whether it is a crock of shit or not. Basically as we know, butterfly throttles present obstruction to clean flow at full open, slide throttles are difficult to implement, and roller barrels are expensive (IIRC).

I was thinking of a new way to operate a variable inlet throttle that keeps flow nice and clean across all throttle openings.

Basically it would be a section of very flexible hose, with an automatic jubilee clip wrapped round it (simplification). To close the throttle, tighten the 'clip' which compresses the flexible hose, making the throttle opening smaller - but keeping it circular with no obstructions in the path of air.

Full throttle would simply open the clip, pulling the flexible material into a larger diameter tube. In all throttle openings, the intake would offer a smooth curved intake, either a straight pipe (at full open) or a smoothly tightening restriction at closed throttle. Hopefully this would retain full laminar flow in the intake tracts.

Obviously there may be materials problems here (the flexible tube would need to be pretty good!) but is this a crazy idiot idea, or actually feasible - and would it offer any benefit at all?

[GreenV8S]

I'm not sure that laminar flow is desirable under all conditions. You may find that having a bit of turbulence to re-energise the boundary layer helps with fuel distribution or wall wetting. In any case, to achieve laminar flow downstream of the device you would need to find a way to expand the air flow back out to the full cross section of the manifold without separation, and that will be extremely difficulty to do at small throttle openings.

[deltafox]

Better to design an engine that does away with the throttle plate altogether, like a diseasel.
Pity it cant be easily done with petrol engines....wonder if some other method is possible?

[Mikey G]

deltafox said:

Better to design an engine that does away with the throttle plate altogether, like a diseasel.
Pity it cant be easily done with petrol engines....wonder if some other method is possible?

Maybe some sort of variable pneumatic/hydraulic/solenoid inlet valve system to replace camshafts, so the valves only open as much as needed?

[GreenV8S]

Mikey G said:

Maybe some sort of variable pneumatic/hydraulic/solenoid inlet valve system to replace camshafts, so the valves only open as much as needed?

Doesn't that just move the restriction?

I seem to remember reading about somebody who was working on a full throttle petrol engine, using some form of stratified charge to allow ultra lean burn. Was it BMW?

[anonymous-user]

BMW Valvetronic engines have no throttle butterfly but control the lift of the valves: www.autozine.org/technical_school/engine/petrol2.htm

[Pigeon]

cyberface said:

is this a crazy idiot idea, or actually feasible

Well God implemented it hundreds of millions of years ago, and it's been successful enough to remain in service on every succeeding model...

I suspect though that on an engine it would be too awkward to implement to be worthwhile.

For a variant throttle idea my own brainwave would be to use an iris disc like a camera lens...

I think quite a few people have worked on stratified-charge unthrottled petrol engines, usually using GDI these days. But my own preferred solution to reducing pumping losses is Uncle Rudi's idea

[GreenV8S]

I wonder if you could use a Dyson style tapered swirl pot as variable restrictor? You can get a nice predictable pressure drop, and the high swirl at the outlet should mean that you can expand the flow as quick as you like afterwards.

[Mikey G]

LexSport said:

BMW Valvetronic engines have no throttle butterfly but control the lift of the valves: www.autozine.org/technical_school/engine/petrol2.htm

So my idea wasnt quite so stupid afterall

[steve_d]

Pigeon said:

.......For a variant throttle idea my own brainwave would be to use an iris disc like a camera lens...

Or for those with larger engine the iris from the Stargate.

Steve

[Mr Whippy]

cyberface said:

Full throttle would simply open the clip, pulling the flexible material into a larger diameter tube. In all throttle openings, the intake would offer a smooth curved intake, either a straight pipe (at full open) or a smoothly tightening restriction at closed throttle. Hopefully this would retain full laminar flow in the intake tracts.

You'd also have to watch out that under heavy demand the low pressure inside the manifold didn't result in the flexible intake collapsing, which would ultimately have a feedback loop effect sucking the throttle completely closed.

Don't think it'd work personally without a very complex control. BMW's Valvetronic is already pretty good at what it does, and I'm sure a throttle plate at fully open isn't *that* restrictive vs the other elements in the intake?

Dave

[BadgerBenji]

Sounds very much like the iris in a lense.

Your sphincter operates in a similar manner but doesnt flow air

Edited by BadgerBenji on Monday 18th September 09:19

[F.M]

I`ve seen some futuristic doors on sci fi films where the metal comes in from the outside to the centre consisting of overlapping plates...Much like the iris analalgy mentioned...
Nice idea though..

Edited by F.M on Monday 18th September 09:51

[Mr Whippy]

BadgerBenji said:

Sounds very much like the iris in a lense.

Your sphincter operates in a similar manner but doesnt flow air

Edited by BadgerBenji on Monday 18th September 09:19

A sphincter flows air too you know

Dave

[BadgerBenji]

Mr Whippy said:

BadgerBenji said:

Sounds very much like the iris in a lense.

Your sphincter operates in a similar manner but doesnt flow air

Edited by BadgerBenji on Monday 18th September 09:19

A sphincter flows air too you know

Dave

But not in polite company

[Mr Whippy]

Infact if the known sound for a similar device is the way it is, induction roar wouldn't quite be the same any more... more a comedy raspberry as you close the throttles

Dave

[leorest]

Mr Whippy said:

...I'm sure a throttle plate at fully open isn't *that* restrictive vs the other elements in the intake?

I agree. Make the throttle opening 1mm larger, or so, would regain the Cross Sectional Area lost by the butterfly. Though the turbulence created by hitting the butterfly/spindle edge on is probably more significant than the CSA.

[leorest]

The "camera" iris is a relatively cheap and easy thing to make and control. Hundreds of millions of cameras over the last century have used them after all. There must be a good reason why it's not been used in production or competition?

[BadgerBenji]

The iris in a lens is not under any pressure operating at right angles to its plates. Whereas if you flow air through it, there will be forces acting at right angles to the iris plates. You also need to be able to close of the air supply, and use the idle air control valve, so it would all have to be very precise, and with this comes cost. If there is any benefit the cost benefit analysis probably doensnt prove favourable compared to say rollers.

[Marquis_Rex]

Anyone performance development engineer who is familiar with shannon hose and who has had to battle it out with NVH development engineers will recognise how a medium with compliant walls will infact absorb energy. Snannon hose is a type of hose that dampens out pulses in the intake system to reduce noise. It also has an adverse effect on performance if placed in performance critical places in the intake system.

The worst case scanerio for this proposed 'compliant throttle part' would be if it was placed in the inlet runner near the inlet valve- as is often on engines with individual port thorttles, where intake tuning pulses will be damped out with resulting loss in BMEP and power.

The throttle blade losses have more of an adverse impact on a port throttled engine- performancewise than a conventional single throttle/plenum arrangement.

Precise control of the "compliant thorttle part" would be critical too, for conditions such as idling as would be sealing...