Archimedes screw throttle

[johnmyster]

The shape of the throttle plate isn't going to get rid of pumping losses. Worrying about turbulent air "friction" issues during part throttle operation when flow is small is silly. Even if your intake was less restrictive, you'd still have to add more throttle plate in order to re-restrict the motor to maintain the necessary power output. There's some confusion about the origin of pumping loss.

Pumping loss is a result of the energy lost when air moves through the throttle plate, going from atmospheric pressure to a lower, state of vacuum. It's a bigger picture process, but that's where it comes from. It's like uncorking an air tank and letting it spill out into a low pressure surrounding. That energy is lost - not mechanically captured.

Take a mini-turbine of some design and put it at the throttle body and derrive mechanical energy from this pressure change. Then, you've recaptured your pumping loss.

Other choices include using lots of EGR (to reduce manifold vacuum without increasing fuel requirement) or a delayed intake valve closing - such that the manifold can be held at one atmosphere, and the cylinder will only partially charge due to "breathing back out" during the compression stroke.

[TrikeKid]

I think the only fix for the restriction caused by the throttle butterfly is a slide style like a motorcycle carburetor. I'm thinking that may be what metromizer was referring to as a guillotine style throttle body. That would pull out the side of the intake completely and allow uninterrupted flow in theory.

[dcb]

Well it wan't necessarily the OP's original concept, but heres a cheesey thought:

1. Hook up properly sized "air drill" controlled by solenoid, drives an alternator, driven off manifold vacuum. Close off existing idle airway.
2. when at idle, open solenoid and disconnect main alternator field.

[johnmyster]

Originally Posted by TrikeKid

I think the only fix for the restriction caused by the throttle butterfly is a slide style like a motorcycle carburetor. I'm thinking that may be what metromizer was referring to as a guillotine style throttle body. That would pull out the side of the intake completely and allow uninterrupted flow in theory.

Wow. I give up.

[dcb]

Originally Posted by johnmyster

20 inches of mercury isn't anything close to 20 psi. 20 inches is (ballpark) 2/3 of an atmosphere, so roughly 10 psi.

Got it, so lets call it 3hp for the 305. BTW, some of us haven't really thought about this before so patience please.

[Vince-HX]

http://www.mne.psu.edu/me415/fall05/SAE/throttle.html

very interesting, i like the spike


Miller cycle or Atkinson

[MechEngVT]

Originally Posted by johnmyster

Pumping loss is a result of the energy lost when air moves through the throttle plate, going from atmospheric pressure to a lower, state of vacuum. It's a bigger picture process, but that's where it comes from. It's like uncorking an air tank and letting it spill out into a low pressure surrounding. That energy is lost - not mechanically captured.

John, you *almost* but not quite hit the nail on the head.

The pumping losses are a horsepower loss measurable at the crankshaft that is consumed by pumping air. The throttling process of the airflow itself has little to nothing to do with pumping losses, except that the greater the throttling the greater the pumping losses. Correlation is not causation.

The pumping loss is the shaft power required to pull air into the cylinder. Nature abhors a vacuum yet atmospheric or lower air pressure does nothing to assist a cylinder to fill with air. Since the piston moves downward into the crankcase (which let's assume is pretty much at atmospheric pressure) and it's pulling a vacuum to draw air into the cylinder from the manifold which is itself less than atmospheric pressure, the pressure differential multiplied by the cylinder area produces a counter-rotational force. This force is what is called "pumping losses."

You are correct, increasing manifold pressure reduces pumping losses. Running at high engine load (near WOT) is a means of increasing manifold pressure. Boosting, EGR, or throttle-less operation increase manifold pressure (relative to a throttled engine)

Intake turbulence only matters if you have a wet intake (as in a carburetor or a throttle-body injection system) if it even matters then. You want to increase flow turbulence once the intake air has cleared the intake port and is in the cylinder and high port flow velocity does this, which BMW's valvetronic does by limiting intake valve lift.

[metromizer]

Originally Posted by MechEngVT

a really cool... sphincter...

My ex-wife called me one of those... but she used laymen's terms I think

sorry, my odd sence of humor kicking in again... I'll stop

Originally Posted by MechEngVT

Lacking anything else to call it that's how I envision it...an idealized convergent-divergent nozzle (i.e. a venturi) that can smoothly and continuously change the area of the minimum opening to vary the mass flow through the nozzle. Haven't quite worked out the practical aspects of that yet....

Seriously though, I was kicking around the one and same idea (adjustable venturi) yet again a few days ago, while wandering through a wrecking yard. I have no idea how to make a smooth venturi open and close while maintaining decent airflow characteristics. Then yesterday, while standing in a collegues office, I found my eyes wandering to a similar 'adjustable optical filter device' when the 'six shooter Throttle Body' idea popped into my head. BTW, I have no idea how to make one of those rotate and seal vacuum at the base, but the drive and indexing mechanism would be cake.

Originally Posted by MechEngVT

Ron, I don't think your idea was taken as offensive. It's just an idea.

ditto. There are no stupid ideas, only thought provoking ones. Bouncing them off other people here on forums is very low risk, with high potential to learn, and help others learn at the same time. I work around some really bright people, who bounce ideas off each other all day long.

[aerohead]

Originally Posted by ronarprfct

I may be blowing smoke on this one, but it occurred to me and I wanted to put it out there and find out the opinion of people much more knowledgeable. I have read that one of the things that limits engine efficiency at less than wide-open-throttle positions is the lack of efficiency of air moving past the throttle (plate, body? I don't remember the word for it for sure, just the thing that throttles the air intake). It occurred to me that something like an arhimedes screw whose rotation could be completely unhindered or even augmented via an electric motor for wide open throttle might be more efficient if you had to slow it down, ie hinder its rotation for less open throttle. Just free wheeling or with electric motor augmentation, I would think it would lose much less energy than the standard-type throttle. Any thoughts? I admit to having much less knowledge than some, but I am not going to stop thinking for myself just because of that, even if I occasionally look like an idiot. For all I know, this type of throttle has been implemented before or someone attempted to implement it before.

The Archimedes screw is like a grain auger.Archimedes designed his to pump out bilges on ships.Both require horsepower.They are also open on both ends.It would be difficult to achieve "idle" with an open pipe,albeit with a complicated pipe as you propose.Rotating the helix would not perform any "valving",which is what the butterfly valve does.The Archimedes screw also would provide a pathway requiring continuous acceleration of the air,as it spirals through the helix,against sidewalls of much greater surface area,robbing power,both through viscous shearing and wall friction.The turbulence created through the throttle is not the source of pumping-losses,as is the manifold vacuum,not present in a diesel ( as it has no throttle ).Diesels benefit from their lack of a throttle,and fact that pound for pound,Diesel fuel has about 11 % more Btus than gasoline.The increased mass of Diesel reciprocating components,works counter to a Diesel's efficiency at high speeds.Typically,my gasoline pickup truck gets better mileage than a VW Rabbit turbo-diesel,at 80 mph.Throttles can be sized to run at WOT during cruise (as is done in carbuteted HONDAs ),achieving low pumping losses and high mpg.

[tasdrouille]

Originally Posted by MechEngVT

I always thought a really cool throttle would be a sphincter. Lacking anything else to call it that's how I envision it...an idealized convergent-divergent nozzle (i.e. a venturi) that can smoothly and continuously change the area of the minimum opening to vary the mass flow through the nozzle. Haven't quite worked out the practical aspects of that yet.

When I read that I thought about something like this:



But without the holes and with the bottom of it removed. Have 2 facing each other.