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?
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Turbo Diesel instant boost 3
- Thread starter gizmag1
- Start date
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...
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...
- Thread starter
- #3
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.
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.
GregLocock
Automotive
Injecting fuel into the exhaust stream ahead of the turbo was done many years ago. It works.
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Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
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.
patprimmer
New member
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.
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A compound turbo/Roots blower type system will solve both problems if set up properly.
Regards
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- #7
SomptingGuy
Automotive
I think he meant no/full load rather than idle/full revs.
Visteon, for example:
Electric supercharging
Bill
Electric supercharging
Bill
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- #13
crysta1c1ear
Automotive
gizmag1 said:
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?
- Thread starter
- #14
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.
- Thread starter
- #15
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!!!
patprimmer
New member
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.
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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
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
- Thread starter
- #17
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
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.
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.
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
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