Throttle wins system

[jakobnev]

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

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

And of course there are enumerable energy conversions going on as well with losses, from the throttle plate pumping losses

What throttle plate pumping losses?

I don't see how it could stack up to eliminating those losses (i.e. direct injection or pulse and glide).

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.

[dcb]

Originally Posted by jakobnev

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

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?

Originally Posted by jakobnev

What throttle plate pumping losses?

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.

Originally Posted by jakobnev

Unless you are talking about diesels i don't see how direct injection eliminates throttle losses.

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.

[pete c]

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.

[dcb]

Run Away!

[jakobnev]

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?

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.)

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.

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.

[dcb]

Originally Posted by jakobnev

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.

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.

[user removed]

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

[jakobnev]

(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.



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.)

[drmiller100]

Originally Posted by Old Mechanic

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

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.

[drmiller100]

Originally Posted by dcb

Run Away!

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.