Throttle wins system
 

The idea is to use the exhausts to heat the incoming air. The air is then passed through a variable axial turbine that acts as the throttle plate. Then through an inter cooler.

The power produced could be used either for generating electricity, or geared down and sent to the crank.

http://ecomodder.com/forum/attachmen...1&d=1324367686

Then Lancelot, Galahad and I wait until nightfall and then leap out of the rabbit

i have always wondered why we don't put an alternator on a turbo charger exhaust to generate electricity.

There are some, see post 18 in this thread http://ecomodder.com/forum/showthrea...tor-15679.html

Maybe you'd care to elaborate on how this relates?

where does the energy to turn the turbine come from and under what operating conditions? How is this better than direct injection with no throttle? I guess it doesn't make much sense without more explanation.

The turbine is powered by vacuum from the engine at low to moderate loads. (I drew an engine by forgot to mention it i guess) The available energy is further boosted by heating the air before it enters the turbine with heat otherwise lost in the exhausts from the ICE.

The turbine replaces the throttle plate and performs all the air restriction necessary for partial load operation of the ICE.

Not a monty python fan, I take it?

I actually like this idea assuming varying the drag on the turbine can give you respectable throttle response. I suspect it might not.

just wondering:

why do you think heating the air will make the turbine extract more energy in this case?

How does changing the angle of attack on the turbine blades effect turbine efficiency?

Can you have a turbine that can restrict air down to idle demands while providing sufficient full throttle airflow?

And of course there are enumerable energy conversions going on as well with losses, from the throttle plate pumping losses (and intercooler fan and extra weight/complexity/cost). I don't see how it could stack up to eliminating those losses (i.e. direct injection or pulse and glide).

As pete notes, you may need a somewhat sophisticated controller for your variable vanes for ok throttle response. It needs to know the rpm of the turbine (and etc) and adjust accordingly to the gas pedal

fwiw I did pick up on the engine and the brown exhaust.

Am I missing something here? Maybe a giant wooden badger would help? (Just kidding :) )

Heating the air increases the volume that passes through the turbine.

What throttle plate pumping losses?

Unless you are talking about diesels i don't see how direct injection eliminates throttle losses.
I't hard to predict how it does against P&G because while P&G eliminates throttle losses it doesn't do anything to convert the heat in the exhausts to useful work either.

Yes but heating does not increase the mass. If you don't send more mass airflow over the turbine, do you think it will perform better?

I meant your turbine throttle, typo. You have to take airflow, turn it into rotory motion, and turn that into electricity or torque via some driveline.

How many hp do you think are available at low/mid throttle and rpm for say a 2 litre engine for your contraption? How much after the conversions? if it is less than 100% efficient at converting the incoming air back into vehicular propulsion then it sounds like a losing scenario to me as compared to no throttle.

There are direct injection gasoline engines, becoming more and more common. If they made it with a throttle plate then the designer would be promptly fired.

perhaps this engine as part of a hybrid system could work. the electrical side could account for quick power adjustments, given the likely sluggishness of a turbine throttle. i would also suggest a few holy hand grenades strapped to the rear bumper for emergency acceleration needs.

Run Away!

It will totally perform better, even if you don't have more molecules of air, each one of them is going faster and can deliver both more momentum and energy. (If mass was the only thing that mattered⁽*⁾, gas turbines would run just as well on water as they do on fuel.)

Even if flow control turned out to be sluggish this could easily be compensated for by an extra bypass and restrictor for increasing and decreasing flow faster.

*⁾ No pun intended.

Thanks, I need to process that a bit, hadn't thought about it in those terms. I have raised a number of other concerns though.

Lets assume that throttle restriction is energy costly (it is), when an engine uses a throttle plate to control air flow into the engine. I guess the question is can you extract enough energy from the restriction to make it worthwhile?

I never really thought it was that much of an energy loss since the most pressure differential you can have is 14.7 PSI (give or take depending on atmospheric pressure).
Would any system be sufficient to do the job of the alternator?

regards
Mech

(I excluded heating/cooling of gas due to expansion/compression for simplify)

Well to create 1cm³ of vacuum when working against 1bar of pressure requires about 98mJ of energy.

A 2litre 4 stroke spinning at 600rpm with full manifold vacuum needs 1000w for the pumping.

http://ecomodder.com/forum/attachmen...1&d=1324638369

At 250mBar it takes about 40mJ/cm³.

If you were say, running a 2dm³ engine at 2500rpm and 250mBar manifold pressure a perfect TB-motor could generate 1300w of power. (and 2700w if the gas was heated to twice the absolute temperature by engine exhausts.)

throttle pumping loss is apparently measurable, and noticable. If you have a manual transmission, you can feel it yourself - coasting down the road, turn off the ignition and note your rate of deceleration. Then floor the throttle - you should feel deceleration lessoning.
This is the reason diesel engines have such crappy compression braking with out "jake brakes" and the like.

Variable vane turbines have been around a LONG time, even in the consumer market.

Turbines run off of the energy contained in the fluid stream - typically heat, but pressure also contributes.

There is a relationship between Pressure, volume, mass, and temperature -
PV=nRT

This thread has caused me to rethink a few ideas I had, and gave me some new ones.

I think there is an opportunity to avoid pumping losses and increase efficiency in a measurable way using ideas grown from this thread, and I plan to test them this spring.

Intake throttling losses are less than 5% of output power under most conditions. And there isn't any energy to be gotten at full throttle, and almost nuttin at idle. So you're kinda stuck trying to get a small fraction of your part throttle at cruise. Maybe your car cruises at 65 mph using 20 hp. So you have about 1 hp to spin the alternator. That would be fine for fair weather.

I remember seeing a patent application for a turbine throttle with variable vanes and a clutch which revved up a flywheel. Moving the vanes acted as the throttle. At cruise you store energy in the flywheel. When you need 100% power the vanes "reverse" and the flywheel powers the turbine. The math is right on the edge of working.

Also looking at jakobnev's graph. Well I think he's missed something. There's hardly any air flow at idle - "full vacuum" so there can't be much power. Not 1kw.

In fact you can try back of the envelope figurin' The power lost to pumping the air into an engine is W=dP * Q, for me, using conventional dimensions, that's horsepower = pressure drop in psi multiplied by flow in cubic feet per second. Well, there's a bunch of conversions in there. Assuming the engine is in the 20% efficiency range and putting out 1 horsepower at idle, that works out to about .66 lb of gasoline per hour. The engine will use 129 cubic feet of air to burn that gasoline. Or 2.2 cu ft per minute, which is about 3700 cu in per minute. The throttle is nearly shut, so the pressure drop might be .95 bar - 14 psi. 14 psi * 3700 cu in per minute is 52000 in - lb per minute or 50 ft-lb per sec. or almost 0.1 hp. about 75 watts.

-mort

W=dP * Q is woefully inaccurate for expansion ratios much greater than one tho.

Any chance you can redo that in SI-units?

Actually if you are coasting with the engine engaged to the power train, and you floor it (engine off) you will increase the resistance.

Why?

Because when you have the throttle closed the in cylinder compression is very low since the air flow is restricted by the closed throttle (high manifold vacuum). With the throttle wide open you have 100% of the available compression, which in most engines is about 10 times atmospheric pressure.

You can see it with a vacuum gauge. 0 measured vacuum means highest possible compression while highest vacuum reading means lowest possible compression. Obviously it takes more energy to compress 10 atmospheres into one than it does to suck 1 atmosphere into an almost perfect vacuum (emphasis on almost). This is why most engines shut the fuel off during deceleration. The compression is so low the fuel will not burn anyway and you have huge amounts of unburned hydrocarbons coming out of the engine.

regards
Mech

I could see using a vvt on the exhaust stream, to add a flexible amount of torque to the drivetrain or something.

But since throttle losses are not necessary (direct injection) it would be best to eliminate them alltogether.

The heat energy on the intake would have to be via heat exchanger, which is going to lose significant energy in the process, the exhaust gas specific heat is not going to be room temperature, and the turbine intake specific heat is not going to be near what left the exhaust valve.

Hi jakobnev,
You must be thinking of some other situation. If your p1 is atmospheric the power to pump something is the sucking force times the flow. The equation is exact.

I guess I'll leave the SI conversion for somebody else. I never got the feel of 100000 Pascals. The only numbers you need to make up are A/F (14.7:1) energy density of the fuel (about 12 kwh/kg maybe for petrol) and engine efficiency.

-mort

Did you try it, or are you just talking your perception of theory?

If you tried it, you will find you are wrong.

Then to rationalize, when you have WOT (or a diesel) you compress 10:1 or 20"1 compression on the compression stroke, but you get all that energy back on the power stroke - kind of like a big pneumatic spring.

how many pounds per hour does a 2 liter engine consume at idle?

where does all that energy go?

ever wonder why diesels get such better mileage then gasoline engines?

fyi, direct injection gasoline thread:
http://ecomodder.com/forum/showthrea...gas-17460.html

so better to use the hot exhaust gas directly on a turbine wheel, no? a-la power recovery turbine http://ecomodder.com/forum/showthrea...tml#post204535

as far as I know adding a heat exchanger will at most equalize the heat between the flows, vs using the exhaust directly. If hot is good, hotter is better.

re: throttle open/closed coast. I never noticed a significant deceleration difference (seat of pants) except open is a little louder.

It seems you and i disagree on whether air is compressible or not.





(Clue: Your formula is accurate for hydro power)

You never get all of the energy back in any IC engine, unless you wish to ignore carnot's law, and yes I have tried it. I recommended it on this site years ago as a way to separate compression-suction losses from mechanical losses.
Coast in neutral
Coast with engine engaged and downshift at exactly the same points where you would normally up shift.
Do the same with the throttle wide open.
Push the car to the same speed and downshift at the same points as the previous test.

The "you get it all back statement" basically assumes there are not other losses involved when there are always losses involved. Moving air through an engine requires more work than sucking against a restricted intake. The rationale of you get it all back would apply equally to the vacuum scenario as it does to the compression scenario.

I have tried it, have you?

Tell you what, have you ever tried a compression test with the throttle closed, then realized you needed to open the throttle to get a true reading.
When you do that (open throttle) the cranking speed slows down because compression increases the total resistance.

Tried it on my Echo years ago and it slowed down faster with the throttle wot.

regards
Mech

Hi jakobnev,
I guess that's sarcasm.
In the case of the automotive engine, we don't need to know about the compressability or heat capacity or any other characterisics of the fluid. Neither does the actual shape of the restriction matter. We don't need to CALCULATE the force required to move the air through the throttle. We simply measure that force. Power is equal to the force times rate of flow.

-mort

To summarize, the members are arguing pumping losses are insignificant for a gasoline engine, and turbo chargers work off of only the mass of the exhaust gasses passing through them (and heat doesn't matter), and variable vane turbos are too far in the future to be worth worrying about.

Hi drmiller,
as Homer says, "Your ideas are intriguing to me and I wish to subscribe to your newsletter."

Merry Christmas to all.
-mort

http://ecomodder.com/forum/attachmen...1&d=1324385008
Are you designing a new crack pipe? :D

not just any crack pipe, a super efficient crack pipe.

winterize the blarney
 

1.pumping losses are not Insignificant in gasoline engines
2. variable vane turbos have been in production and use in VWs for many years
3.gasoline engines with direct injection still use throttle plates or variable lift intake valve to control air flow to the intake and by so doing
MUST have suction throttling loss es / pumping losses

AFR in gasoline engines is controlled to be near 14.7 to 1 much but not all of the time in direct injection gasoline engine systems and it could NOT be controlled if air flow were to be UN controlled as it is in a older diesel engine / remembering that air flow is regulated / controlled in newer diesel systems by a
throttle plate , primarily used to
increase EGR flow by increasing pressure delta betwixt exhaust and intake ,
also
throttle plate is used to stop the diesel engine right now when key is switched to off in current production diesel engines with direct injection, assuming there is a "key" .

the throttle plate in newer diesel engines does increase pumping losses / suction throttling loss and the throttle plate in the exhaust (also used to increase EGR flow ) does not help in that regard either

to winterize

Yes
 

I think depending on configuration of the turbine it might need a throttle plate besides in order to achieve a low idle?

you are correct
 

yes it would and
hardware and software to control when the two switch back and forth

as well
it is a bad idea to take heat from the exhaust as that will screw up exhaust flow , especially when there is plenty of extra heat and some pressure available from ducting the back side of the radiator ala
Meredith effect ...

gains would be small , but gains are gains

I don't think the ecoboost has a throttle, I don't know why it would need one either. The original (i.e. 50 years ago) direct injection schemes had a throttle, but I don't think it is a requirement these days. What am I missing here?