Multi Point Injection Diesel?
Multi Point Injection Diesel?
(OP)
I was wondering whether it made any sense to have more than one injector per cylinder in diesel engines.
Instead of a centrally mounted injector fed by a fuel line from the common rail injecting fuel, for example, at a maximum of 1350 bar (like in my car, 90 PS/BHP? HDi, my 2000) why not have 2 or 3 in the hopes of improving spread and mixing and also speeding it up for better torque at high rpm.
Would it make sense to have 3 solenoid injectors per cylinder connected to 3 common rails fed by 3 injection pumps running at a peak of 1350 bar instead of 1 piezoelectric injector per cylinder connected to one common rail fed by 1 injection pump operating at a maximum of 1600 bar?
At least in terms of specific power if not of efficiency (running three 1350 bar pumps instead of one 1600 bar pump) or cost?
Or, if you can get it to work, use one injection pump feeding fuel at 1350 bar to one common rail with 8 or 12 outlets for two/three solenoid injectors per cylinder in an inline 4, for example.
You'd also be able to keep multi stage injection to high rpm with solenoid injectors.
I was thinking of placing the injectors so that they form an equilateral triangle inside, not necessarily near, the cylinder circumference and have them oriented centrally, towards the piston crown burn chamber.
Pls. don't lapidate or laugh. I'm not an engineer.
Instead of a centrally mounted injector fed by a fuel line from the common rail injecting fuel, for example, at a maximum of 1350 bar (like in my car, 90 PS/BHP? HDi, my 2000) why not have 2 or 3 in the hopes of improving spread and mixing and also speeding it up for better torque at high rpm.
Would it make sense to have 3 solenoid injectors per cylinder connected to 3 common rails fed by 3 injection pumps running at a peak of 1350 bar instead of 1 piezoelectric injector per cylinder connected to one common rail fed by 1 injection pump operating at a maximum of 1600 bar?
At least in terms of specific power if not of efficiency (running three 1350 bar pumps instead of one 1600 bar pump) or cost?
Or, if you can get it to work, use one injection pump feeding fuel at 1350 bar to one common rail with 8 or 12 outlets for two/three solenoid injectors per cylinder in an inline 4, for example.
You'd also be able to keep multi stage injection to high rpm with solenoid injectors.
I was thinking of placing the injectors so that they form an equilateral triangle inside, not necessarily near, the cylinder circumference and have them oriented centrally, towards the piston crown burn chamber.
Pls. don't lapidate or laugh. I'm not an engineer.





RE: Multi Point Injection Diesel?
About triple the cost for the fuel system.
The valves might get in the way.
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RE: Multi Point Injection Diesel?
- Steve
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
blacksmith
Not sure about that theory but I would suggest that you brush up on your combustion fundamentals. Diesels engines dont have the same combustion process as gasoline (laminar & turbulent combustion) they tend more to diffusion type flames and are in effect multiple flame fronts all burning away as the situation allows.
MS
RE: Multi Point Injection Diesel?
Maybe you could save money by having a lower pressure system able to deliver a max. injection pressure of only 1350 bar like my first gen. CR. And on solenoid instead of piezoelectric injectors.
I should think the nozzles would be simpler to machine as well, not needing as many holes.
3 nozzles instead of one would have a higher flow rate and main injection sequence would take less leaving time for post combustion at higher rmp and preinjection at higher rpms than would be possible with a single solenoid injector.
The micro droplets wouldn't have as far to travel in the same amount of time which would benefit high rpm torque through quicker dispersion and you could have lower injection pressures than with a single injector.
You could even fire the three injectors sequentially to promote better swirl for the second and third injectors.
There must be some application niche for this. Railroad or truck diesel, maybe.
At least a feasibility study.
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
Therefore, in theory it could work but in today's reality there are no gains available and the cost and engineering to achieve multiple injection points is significant. I wouldn't be surprised if this is done someday when we have better control of the combustion mix and can get the cylinder pressure up while still avoiding NOx (highly controlled homogenous EGR, during-combustion air injection, other exotic solutions).
To get the effect you want, why not just greatly increase the number of cylinders and make them smaller?
RE: Multi Point Injection Diesel?
Maybe someday or for really large bore applications.
Final question. Do ship engines use multi point injection?
I think using more cylinders would not achieve the same effect because of added crank inertia due to a longer crank, more friction points with a longer crank and more piston skirts and ring, crank flexing issues and more reciprocating weight.
Basically, more inertia, heat loss and friction for the same amount of burnt. More parasitic losses.
Thanks for the info.
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
A - Run at 1350 bar to get better atomization, not to get more fuel in faster.
B - Often shoot the fuel in multiple shots per combustion event (up to 5) for emissions and noise reductions. One big bang vs 3 little bangs.
ISZ
RE: Multi Point Injection Diesel?
Avoiding cylinder wall collision is not to avoid knock. It's to avoid massive soot generation, rapid oil degradation, and catastrophic engine failure due to ring failure and piston scuffing.
Flame front collision shouldn't cause knock, but it will cause localized oxygen depletion and excessive soot. Low cetane can cause flame front collision (late combustion) and independently knock (early combustion), and of course both in the same engine at different times due to unpredictability of the combustion.
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
Of course, it can never be earlier than time of injection, so calling it early combustion is probably not as good of a description as unpredictable combustion - which is probably your point. In the late combustion case, I was focusing on the more catastrophic problem of fuel impinging on the cylinder wall, but detonation is bad anywhere as I think you are also pointing out.
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
RE: Multi Point Injection Diesel?
This is what Elsbett has to say
Cheers malbeare
h
A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare
www.sixstroke.com
RE: Multi Point Injection Diesel?