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Turbo Diesel instant boost
3

Turbo Diesel instant boost

Turbo Diesel instant boost

(OP)
Just an idea I conjured up recently. Naturally aspirated Diesels draw basically the same amount of air at idle as they do at full revs, They only vary the amount of fuel injected into the cylinder to vary their output, add more air (i.e turbo) and you're able to burn more fuel - more power...But with turbo lag still posing an engineer's nightmare. Variable vane turbo's, while better, still aren't perfect. What aboutfitting an injector situated between the exhaust manifold and the turbocharger. This would allow full boost to be achieved from idle - actuated with application of full throttle. NO turbo lag, Super charger style boost without the parasitic drag... Just a thought?      

RE: Turbo Diesel instant boost

Oh god thats wrong on soooo many levels....

Dumping xtra fuel at the turbo wont make it spin faster, more than likely it will start a fire....

To get the effect you are after, a well set up NOS system that actuates at part trottle and low boost would do the job -not pointed at the exhaust-, till the bottle ran out...

RE: Turbo Diesel instant boost

(OP)
Rather than think fire,  think similar principles to a gas turbine. In fact exhaust manifold injector could be fasioned similar to that of a combustion chamber/flame holder from a gas turbine.
 The train of thought was to optimise thermal efficiency and drivablity of Diesel.
 Possible to substitute fuel for steam injection at nozzle and utilise huge expansion rate of water to afford similar results??? Just thinking outside the square... More of a why not than a why.

RE: Turbo Diesel instant boost

Injecting fuel into the exhaust stream ahead of the turbo was done many years ago. It works.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

RE: Turbo Diesel instant boost

many things have been done to account for lag.  Fuel into the manifold is bad because it's hard on the turbines..  some people would inject CO2 or compressed air at the compressor blades.  That worked but the CO2 had issues with it being so cold.

RE: Turbo Diesel instant boost

Injecting fuel into the manifold would certainly reduce lag, but it sure won't do much for fuel economy.

A compound turbo/Roots blower type system will solve both problems if set up properly.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Turbo Diesel instant boost

Quote:

Naturally aspirated Diesels draw basically the same amount of air at idle as they do at full revs

Sorry, but could you explain that one?

Bill

RE: Turbo Diesel instant boost

No throttle.

RE: Turbo Diesel instant boost

I think he meant no/full load rather than idle/full revs.

RE: Turbo Diesel instant boost


Yes, I can see no difference in air flow between full-speed/full load and full-speed/no load, I just thought I'd ask gizmag1 the question.
I suppose it's me being thick.

Bill

RE: Turbo Diesel instant boost



There are also a few electrically enhanced turbos and air pumps for that very purpose.

RE: Turbo Diesel instant boost

Quote (gizmag1):

Possible to substitute fuel for steam injection at nozzle and utilise huge expansion rate of water to afford similar results??? Just thinking outside the square... More of a why not than a why.

The turbine extracts thermal and kinetic energy from the exhaust gases. If you add water, then energy is required to evaporate the water, and this comes from reducing the energy in the gases before the turbine. If steam is added then you partly have a steam turbine. So while using enough steam should provide power to the turbine, it begs the question what is the power source for this partly steam turbine?

RE: Turbo Diesel instant boost

(OP)
WGJ - sorry for slow response... Basically petrol engines run at a constant ratio of air to fuel ( typically 14.7:1 for minimum emissions - more parts fuel for power, and less for economy ) They vary their power by varying the amount of fuel/air mixture drawn into the cylinder by means of a throttle valve. Diesels on the other hand draw in the same amount of air ( na only ) and vary the amount of fuel injected into the chamber. Which is part of the reason that diesels are so economical. They can run an air fuel ratio of say 200:1 at and idle and say 12:1 at full revs. This also explains why diesels of old beltched out plums of black smoke; there is only so much air to support cumbustion. once the diesel has burnt up all the oxygen, the rest just poors out the exhaust as sooty deposits. You can now see why Diesels support the use of turbos so well.

RE: Turbo Diesel instant boost

(OP)
Crystalclear - sorry for slow response, my thoughts were the heat energy wasted out the exhaust pipe or cooling system could be tapped to extract the wasted heat energy - how quickly does the coolant turn to steam with the most basic of failures? I'm guessing This pocess could theoretically make the engine more efficient? I love your train of thought with trying to diminish the amount of wasted energy!!!

RE: Turbo Diesel instant boost

gizmag1

I think everyone who actually belongs here understands constant a:f ratio and air throttle of SI engines vs fuel metered WOT of CI engine, in fact many actually design engines for a living.

You still overlook your mistake in your original post even though several have pointed it out.

A diesel does not ingest the same amount of air at idle as at full speed. It only ingests the same amount of air at constant rpm. If idle is 500 rpm and full speed is 2500 rpm, at full speed it ingests about 5 times as much air. A diesel does ingest about the same amount of air per turn of the engine whether at full load or light load.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Turbo Diesel instant boost

(OP)
Thanks patprimmer, perhaps my original statement should have read: Naturally aspirated Diesels draw basically the same amount of air at idle as they do a full revs per rotation... Naturally cfm's increase as r/m rate increase. sorry for the oversight - my bad

RE: Turbo Diesel instant boost

Yo Pat. You are polite.

Bill

RE: Turbo Diesel instant boost

Essentially, on a N/A engine the volumetric efficiency remains fairly constant from idle to max governed speed eg approx 85-90%, however, in a turbo application this can be upto 150% and sometimes even greater dependant on design and application.
As previously mentioned a diesel runs without air throttling as in the case of SI engines and hence runs at full compression. I would hasten to add there are some systems that do use a throttle butterfly to control fueling.

RE: Turbo Diesel instant boost


Hello r2800. I thought that any air throttling on a diesel for  fueling control was now quite archaic. I remember seeing something like this in my first college thermodynamics book in the 60s and it was old even then.
Any experience I've had with throttle plates in diesels has been as part of an emissions control (EGR/crankcase gas) and/or 'shut off shake' control system.

gizmag1 - although r2800 says that volumetric efficiency tends to be (broadly) constant over a range of engine speeds, speed is obviously the ultimate control on air consumption, as you have acknowledged in your last post.

Bill

RE: Turbo Diesel instant boost

Toyoytas use throttle butterflies to this date

RE: Turbo Diesel instant boost

I seem to remember throttling a diesel being a potential solution to something related to NVH or emissions a few years back, but my searches (internally and externally) have left me empty-handed.  Would be interested to know what the story was... and what Toyota use throttling for.

RE: Turbo Diesel instant boost

Apart from the electric supercharger or electrically assisted turbo, there are additional options to reduce lag:

A 'Dual-Turbo' (sequential-turbo):
http://www.greencarcongress.com/2006/06/peugeot_applies.html
(The porsche 959 originally introduced this concept).

Or a mechanical supercharger that is engaged at low rpms:
http://www.greencarcongress.com/2005/08/vw_introducing_.html

Or a pressure wave supercharger:
http://www.egr.msu.edu/mueller/projects_waverotor.htm
http://www.wenko.ch/e/news.e/techinfocontent.e.jsp
Mazda 626 was running it.

RE: Turbo Diesel instant boost


r2800 - Like SomptingGuy, I'd be very interested to have any links you may have for the Toyota application.

Bill

RE: Turbo Diesel instant boost

globi5

See my post of a few days ago.

gizmag1

There is an extensive previous thread on compound supercharging or twin-charging. The on site google feature works best.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Turbo Diesel instant boost

Hello gizmag1 -

Relative to your original post (this thread has really meandered), and to GregLocock's answer, please do a search for the French built SACM Hyperbar diesel engine that is used in the Leclerc main battle tank.

Dick Vincent

RE: Turbo Diesel instant boost

(OP)
Turbomotor - Thanks for the lead - wikipedia will be hit hard! You do realise than you've made it increasingly difficult to explain the need to experiment with this technology on my own hilux!!! I can hear the missus now - TANK your not bolting a tank to you car!!!

RE: Turbo Diesel instant boost

The toyota system uses a butterfly controlled by a stepper motor controlled by ecu,designed for emissions rather than throttling in the conventional sense.
In my earlier life I worked extensively on trucks & coaches and pnuematic governors were common as indeed was a throttle set up to allow manifold vacuum to be built up for servo brake operation, I'm thinking of old landrover diesels here.

RE: Turbo Diesel instant boost

r2800

Quote:

The toyota system uses a butterfly controlled by a stepper motor controlled by ecu,designed for emissions rather than throttling in the conventional sense
Exactly what has been said. The 'throttle' is used so that, under certain speed/load conditions, EGR and crank case gas is consumed in preference to clean air to help control emissions. The valve is often shut at key-off to help reduce engine shake as it stops.

Quote:

In my earlier life I worked extensively on trucks & coaches and pnuematic governors were common as indeed was a throttle set up to allow manifold vacuum to be built up for servo brake operation, I'm thinking of old landrover diesels here.
Well, I suppose the adoption of vacuum pumps to power the brakes and the efficiency loss due to throttled operation killed off the old pneumatic type governeors. I certainly never saw one on the 30 years I've been associated with truck and car diesels.

Bill

RE: Turbo Diesel instant boost

Leyland 350,600 & some versions of 680, Bedford 300/330
Ford Trader 4 & 6 cyl models, Some Perkins models too.
Admittedly these are late 50's early 60s.

RE: Turbo Diesel instant boost

The later Toyota (and other brands too) with electronic pumps use the throttle body for TPS and ECU control of the pump....and vacuum control of EGR etc.

I've seen throttle bodies on the old British diesels as others have mentioned,and  diaphram govenors.The last vacuum govenors I worked on were in the Nissan 220D,a common vehicle for taxi's.

RE: Turbo Diesel instant boost

Pre-turbine combustion anti-lag strategies have been used for quite some time in racing with excellent results (most commonly found in rally cars).

http://www.rallycars.com/Cars/bangbang.html

It's incredibly loud and will never make it to production vehicles in that form.

RE: Turbo Diesel instant boost

jblaine -- Rally fan? I was wondering if anyone would put that link up....

(TSD Rally driver, RA Worker, Service crew chief #734, KD8EUT)

RE: Turbo Diesel instant boost

NickE - Well well, if it isn't LyveWRX :)  Hello from a fellow NASIOC member with Google skills.

RE: Turbo Diesel instant boost

yea, I inhabit this place too... The questions are harder and the answers way more involved than most delivered to NASIOC.

Of course we have our share of disagreements here, though they usually can be solved with a small application of math and science, something that normally doesnt help at NABISCO.

RE: Turbo Diesel instant boost

I worked on a 60's something Mercedes Diesel that throttled the inlet air.

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