Piston Bowl Config vs Nozzle Size in HSDI Engines

[Brayden]

Another good read.. Research was conducted by Toyota.

http://www.tytlabs.co.jp/english/review/rev373epdf/e373_017hotta.pdf

Comparing deep and shallow combustion chambers with two different sized injectors.

What I gather from this is that a larger nozzle may help in higher RPM and load conditions compared with a smaller nozzle and more volatile flame front.

Interesting for sure.


Brayden

 

[sweetdiesel]

Brayden not sure if your a meber of SAE but they had a really good write up also
if you do a search they cost about 10 bucks...but they are good reads

BTW thanks for the link

 

[Brayden]

I'm not a member yet.. Thinking about it though..

 

[sweetdiesel]

its only a opinion but a keeper IMO

I like how they talk about the injectors and the difference in the RPM they sure have nice test equipement

 

[sweetdiesel]

I'm not a member yet.. Thinking about it though..

I sighned up years ago.but unless it pertains to diesel power i dont loook:rofl:

Theys send you emails weekly to new publications...then you just choose to download for X amount.Auto billing to your creditcard

 

[Tacojedbob7]

so increasing diameter of the nozzle and decreasing depth of bowl will yield an increase in power? pistons could be cut down to decrease bowl depth, but how would the lower compression affect this theory?

More power and less pollution sounds good to me!

 

[Brayden]

They're after less soot and a cleaner burn.. That means we can overfuel that much more without having to add boost.. Anytime you can gain efficiency it will help greatly.

The only way to test different bowl config's would be with a forged piston. You could create the bowl you want with the volume you want to create the desired compression.

What I gather from that paper is that there's plenty of turbulence in the cylinder at high rpms. So it would seem that we could get away with a shallower bowl, still lipped, (toroidal reentrant design) and an even shallower spray angle.

For those that are into long durations the flatter spray angle would be bad. But if you were to increase nozzle size and run short pulses I think this is the direction things would need to go.

Just my opinion though.

Brayden

 

[McRat]

Very interesting. Thanks.

Our injectors are .15 and our target rpm range is 3000-4500, so this is relevant.

If I'm reading it right, the squish band (flat area on top of piston/chamber) creates such violent swirl that it is interfering with small injector combustion at high RPM. By widening the bowl (reducing the squish band) it allows small injectors to burn the fuel more completely.

Looks like they are using 50mm of fuel, while we are using 250mm of fuel, so I do not know what effect that would have, plus we are pushing the fuel in at 190mpa instead of 130mpa like their test. Their injectors are 6 hole 155, ours are 7 x 158 which is similiar.

I would be interested in trying a large dia bowl in the future.

 

[malibu795]

MDE posted soem info along this line..bassicly saying on off idle and part throttle larger inj suck compared to smaller inj. with everything remaining constant except inj holes

 

[Brayden]

One sentence which describes something that sucks based on opinion doesn't add much to the technical nature of this thread does it?

I have 45% over nozzles in an LBZ with a stock engine and it certainly doesn't suck. Tuning has to be addressed to properly pull off a set of nozzles or really any mechanical change to the engine.

Pat would you say that by increasing the pressure we're atomizing even better and making the flame front more volatile (easier to push around)? Or the opposite, more fuel, more dense, more stable.

Keep in mind those tests were done on a single cylinder engine. The fuel flow rates are per cylinder. Their engine is 497cc and our single cylinder would be 823cc. Not exact science there but close.

Pretty amazing that they can flow 50mm3 in one cylinder and not smoke, I wonder what the boost limits were?

Anybody else notice the timing numbers.. I think my theory is on track. The larger injector in the tests requires less advance, and less duration in CA than the smaller injector.

 

[Trippin]

Interesting read. Thanks for sharing Brayden.

Seems to agree with my previous research.

 

[McRat]

One sentence which describes something that sucks based on opinion doesn't add much to the technical nature of this thread does it?

I have 45% over nozzles in an LBZ with a stock engine and it certainly doesn't suck. Tuning has to be addressed to properly pull off a set of nozzles or really any mechanical change to the engine.

Pat would you say that by increasing the pressure we're atomizing even better and making the flame front more volatile (easier to push around)? Or the opposite, more fuel, more dense, more stable.

Keep in mind those tests were done on a single cylinder engine. The fuel flow rates are per cylinder. Their engine is 497cc and our single cylinder would be 823cc. Not exact science there but close.

Pretty amazing that they can flow 50mm3 in one cylinder and not smoke, I wonder what the boost limits were?

Anybody else notice the timing numbers.. I think my theory is on track. The larger injector in the tests requires less advance, and less duration in CA than the smaller injector.

The higher pressure should spray the fuel further, less deflection. Like a bullet.

Something that also affects the results: They are trying to reduce smoke, and are calculating HP gain by the threshold of smoking. We on the otherhand are doing our damnest to overfuel past the point of smoking. Even our "tuning only" trucks would be considered smokey by their scale. The dmax race engines BILLOW out smoke.

 

[duratothemax]

cool info, thanks brayden

 

[Gasuout]

So cutting the lip off piston is a good thing .

 

[sweetdiesel]

Pat would you say that by increasing the pressure we're atomizing even better and making the flame front more volatile (easier to push around)? Or the opposite, more fuel, more dense, more stable.

Depends on temp and vis

Injection pressures above 25k and a temp of around 75-80f lead to better atomization.This leeds to better evaparation of the liquid fuel, hence a better burn and less timing advance needed


Just some stuff ive read in the past

 

[Mike]

The higher pressure should spray the fuel further, less deflection. Like a bullet.

Something that also affects the results: They are trying to reduce smoke, and are calculating HP gain by the threshold of smoking. We on the otherhand are doing our damnest to overfuel past the point of smoking. Even our "tuning only" trucks would be considered smokey by their scale. The dmax race engines BILLOW out smoke.

Just wondering if that added pressure for distance can be true Pat. With orifice size and volume staying the same, I would think distance would decrease due to air friction creating turbulence with that higher pressure. I mean a golf ball has dimples for a reason. I wonder if your theory would hold true if volume was also increased or maybe just orifice size? Kinda like a pressure washer spray granted the orifice is not identical but still causes a higher mist with higher pressure and the same volume. What do you think?

 

[Mike]

So cutting the lip off piston is a good thing .

I think so but only if impinging is already controlled by injector spay pattern, timing and bowl configuration.

 

[SmokeShow]

Anyone remember seeing the pictures of Banks' prototype pistons that they are gonne be using and producing??? If so, you may recall, at least I do, that the bowl in them has a good bit larger diam. than that of a OE duramax piston. At least it appeared that way to me when comparing a picture of their piston to a stocker. Perhaps they are finding the same trends in their research as well.

Very interesting stuff for sure! Thanks for sharing Brayden!


C-ya

 

[Brayden]

That's what this site is for.. Uncovering Tech

You're welcome.

Brayden

 

[mytmousemalibu]

Everyone breakout the magnifiying glasses! This is top shelf stuff! We need to look closer into this! I was wondering if the 50% nozzles were becoming a step backwards and this throws the balence back in my favor! And yes, big "SOTP" power gain reported here too Brayden!