soot measurement in exhaust gas

BartW

BartW

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www.amptec.be
last year we drove the boat A LOT at 1200rpm / 11..12kn
this is slightly above displacement speed (9kn)

after several hours / day's of navigation there is some soot on the edge of the swim platform,
SB side slightly more than P side.

both engines and mechanical injection pumps have been rebuild. (2015-2016)
the soot is less then before the rebuild, but still a bit too much for me liking.

what could be the cause of that ?
perhaps the engines are used in a non optimum RPM / cruising speed (better at 9..10 kn 1100rpm or full planing 2000rpm- 20kn,
remember these old engines are fully mechanical (no electronics)

air filters look a bit black didn't replace them last year,
could that be the cause ?
(new filters are on order)

problem for testing is that I can only see the soot after long periods of navigation,
would it be usefull to "measure" soot in exhaust gas, at different engine performance ?
how to measure ?

or should I just accept that and live with it?
 
There’s few threads on running marine high speed diesels below optimum rpm for long periods .
Operating a P boat at D speeds .
Soot , is an imbalance of the air / fuel ratio .
It can be caused by faulty injectors or the pump .But these you say have had recent overhaul s .
Air filters —- maybe ? ,but should be good for 200 hrs or so .

You see ideally to get the correct burn temp and pressures inside the cylinders s you need to be higher than 1100 rpm .
I suspect there in is the problem. The combustion temps / pressures are not high enough .
The soot gets in the oil more than say running at 18-2000 rpm. Cos at the “ cooler “ 1100 rpm the rings are not tight enough .
At really low temps for long time the soot even clumps together into even bigger more damaging particles .

Some say an “ Italian tune up “ 10 mins every hour or what ever to burn off / flush out the soot that’s built up from excessive time at D speed .

With modern electronic diesel s the effect of sooting is less due to more control, because various sensors can adjust the fuel more accurately, indeed with Common Rail as well there’s less sooting as is the control is as about as accurate as they can get it .
So running at D in a P boat with high speed diesels so imho — allowed with CR , I think you can get away with it .
High speed diesel is over 1600 rpm , so most MANs are designed to run about 2000 rpm .

Personally because I have the added luxuary of seeing the load and the EGT,s I set the cruise on those .
Near 80 % and EGT North of 550 degree C .

It’s amazing how fast the EGT drops - almost instantaneous as you back off the rpm .

So for me assuming everything’s OK with the mechanical side then it’s too low combustion temps / pressure that’s causing the soot .
The Mech pump if it’s been calibrated right will be optimised for max bhp and normal cruise rpm around 2000 .

I have mentioned this before regarding correct engine match for use .
In 2003 ish Sunseeker built a pred 108 for a client who was having a year off to do the Med .
It was stabilised ( before anybody asked :) but and it’s a big BUT it had a pair of John Deere’s max speed was somthing like 14 knots and cruise ( at the correct rpm for correct cylinders pressures/ temp ) was somthing like 11 knots .
Long range tanks etc , for self sufficiency.
Looked the part - stylish of course .This guy did not fancy the rufty tufts trawler , Nordhaven , look .
Crewed boat .
 
Bart, I don’t think this is a big issue. It sounds like the calibration is “overfuelling” at the speed you are running. As a mechanical fuel injection system, there are a lot more compromises than an electronic engine with fuel and exhaust sensing. An electronic engine will change the fuelling to suit the load.
With Rafiki, I can tell when the props need a clean, as the transom gets sooty. Our Cats are mechanical.
 
Portofino said:
There’s few threads on running marine high speed diesels below optimum rpm for long periods .
Operating a P boat at D speeds .
Soot , is an imbalance of the air / fuel ratio .
It can be caused by faulty injectors or the pump .But these you say have had recent overhaul s .
Air filters —- maybe ? ,but should be good for 200 hrs or so .

You see ideally to get the correct burn temp and pressures inside the cylinders s you need to be higher than 1100 rpm .
I suspect there in is the problem. The combustion temps / pressures are not high enough .
The soot gets in the oil more than say running at 18-2000 rpm. Cos at the “ cooler “ 1100 rpm the rings are not tight enough .
At really low temps for long time the soot even clumps together into even bigger more damaging particles .

Some say an “ Italian tune up “ 10 mins every hour or what ever to burn off / flush out the soot that’s built up from excessive time at D speed .

With modern electronic diesel s the effect of sooting is less due to more control, because various sensors can adjust the fuel more accurately, indeed with Common Rail as well there’s less sooting as is the control is as about as accurate as they can get it .
So running at D in a P boat with high speed diesels so imho — allowed with CR , I think you can get away with it .
High speed diesel is over 1600 rpm , so most MANs are designed to run about 2000 rpm .

Personally because I have the added luxuary of seeing the load and the EGT,s I set the cruise on those .
Near 80 % and EGT North of 550 degree C .

It’s amazing how fast the EGT drops - almost instantaneous as you back off the rpm .

So for me assuming everything’s OK with the mechanical side then it’s too low combustion temps / pressure that’s causing the soot .
The Mech pump if it’s been calibrated right will be optimised for max bhp and normal cruise rpm around 2000 .

I have mentioned this before regarding correct engine match for use .
In 2003 ish Sunseeker built a pred 108 for a client who was having a year off to do the Med .
It was stabilised ( before anybody asked :) but and it’s a big BUT it had a pair of John Deere’s max speed was somthing like 14 knots and cruise ( at the correct rpm for correct cylinders pressures/ temp ) was somthing like 11 knots .
Long range tanks etc , for self sufficiency.
Looked the part - stylish of course .This guy did not fancy the rufty tufts trawler , Nordhaven , look .
Crewed boat .
Click to expand...

Thanks PF,
it has been confirmed from many sources that this old MAN engine can run for day's at slower RPM,
the turbo's start spinning from below 1000rpm iirc. (thats why they can)

and in my situation last summer, I would expect there to be a little more soot because I was slightly ABOVE relaxed D speed,
I remember from the skiing behind BA, that she produced quite a bit of black smoke, while fast accelerating from 1100RPM to 1600rpm...


If I knew that EGT measurements would give me some insights in this; I would install one or two pairs of gauges,
but I'm afraid that these would just give measurements that can be expected,

and tbh I'm not so much worried about too high EGT, (very often your concern...)
boat has been runnning fine for 25y, and now with the rebuild engines she's running even smoother than before.

I would really be interested to measure the "soot" in the exhaust gas.
 
rafiki_ said:
Bart, I don’t think this is a big issue. It sounds like the calibration is “overfuelling” at the speed you are running. As a mechanical fuel injection system, there are a lot more compromises than an electronic engine with fuel and exhaust sensing. An electronic engine will change the fuelling to suit the load.
With Rafiki, I can tell when the props need a clean, as the transom gets sooty. Our Cats are mechanical.
Click to expand...

OK, that sounds right,
and I'll probably leave it like that,
but if you know a way of measuring soot, pls let me know
 
BartW said:
OK, that sounds right,
and I'll probably leave it like that,
but if you know a way of measuring soot, pls let me know
Click to expand...

Not on a mechanical engine Bart. There are Particulate Traps as aftermarket fits for commercial vehicles, but this will not be an easy packaging fit in your boat. Not worth the effort Bart.
 
rafiki_ said:
Bart, I don’t think this is a big issue.
Click to expand...
+1.
The only thing there's no reason to expect is the difference between port and stbd.
B, what do you mean exactly by "slightly more"? If barely perceivable, I wouldn't bother.

Besides, are you sure to have ALWAYS stbd>port?
I'm asking because the soot stagnation might well be affected also by the wind direction...
...but it's rather unlikely that you are always cruising with the same apparent wind, of course! :rolleyes:
 
MapisM said:
+1.
The only thing there's no reason to expect is the difference between port and stbd.
B, what do you mean exactly by "slightly more"? If barely perceivable, I wouldn't bother.

Besides, are you sure to have ALWAYS stbd>port?
I'm asking because the soot stagnation might well be affected also by the wind direction...
...but it's rather unlikely that you are always cruising with the same apparent wind, of course! :rolleyes:
Click to expand...

P,
the decision to not bother gives a lot peace of mind ;-)

after long trips the edge of the swimplatform has a black film on it,
and it is alway's a bit more black on SB side,

now there is more that I should explain,

the Bosch center in Zagreb who did a thorrow re-inspection / retune of both pumps, (after we discovered a difference in max rpm remember )
told us that both pumps are not exactly the same, just one number difference in a long type number,
and the pumps behave a little different, and that it is impossible to adjust both pumps to behave exactly the same over their total working curve....
apparently one pump is not a orriginal, we don't know when this has been swapped, Afaik not during my ownership of the boat.
after some investigation it turned out that the SB pump (a bit more soot) is the orriginal,

communication with Bosch Zagreb was done by Ilko,(Montenegro) so very difficult to get more details now...

the reason why I am anoid with this is:
after a few hours navigation there is a black film also on top of the bathing platform, and on the edje of the fixed platform,
guests lean or sit on that during bathing, and get black stains on their swim suits, or on their skin,
that's why it annoy's me.
(we only wash the boat and platform ones every week or every two weeks in summer)
going to asc the crew todo the platform after every trip !
 
My experience of mechanical diesel engines is from more modest ones than yours, but still similar in that I've always had some soot on the edges of the bathing platform.

I had Volvo KAMD300's on the Sealine and after an hour's run, I had to mop the corners. The stb side was worse and in an effort to improve things, I had the injectors replaced at my engineers suggestion. All the other usual suspects were ruled out.

This made zero difference.

My current TAMD75's are a lot better in this respect, but there is still some and occasionally I need to use the mop.

I've found that running at lower speeds makes things slightly worse as the exhaust gases tend to linger around the transom for longer.

Frankly, I would be surprised to learn of a boat with older engines that don't have this problem at all.
 
Bart, my stbd engine uses considerably more fuel than the port one. I can find no clear reason for this. In addition, the port side of the boat appears to get more soot than the starboard. Logically this should be the other way round given the fuel burn.
 
scubaman said:
Frankly, I would be surprised to learn of a boat with older engines that don't have this problem at all.
Click to expand...
Actually, as you possibly remember, the Cat 3116 on my old boat were amazingly clean.
Never really understood why, maybe they got so used to spin at ridiculously low rpm/load that they self-adapted to the situation...! :rolleyes:
But I agree, generally speaking all mechanical engines I came across were smokey, regardless of builder.
MAN, Cat, VP, MTU... You name it.
 
rafiki_ said:
Bart, my stbd engine uses considerably more fuel than the port one. I can find no clear reason for this. In addition, the port side of the boat appears to get more soot than the starboard. Logically this should be the other way round given the fuel burn.
Click to expand...

have you done a full- full test with a good run to verify.? I have found boat fuel gauge accuracy to be very imaginative,depending on the type and installation.

I also was introduced to an interesting test a few weeks back to help determine which engine is working harder (at a decent engine speed)- measure the temperature of the pipe from the turbo charger compressor side to the charge air cooler. They should be similar.
 
Bart,

another solution is that as part of your hull rebuilt, you paint the transom dark grey :p

serious, I also get soot on the transom, cannot really say I get more on one side or the other, but it's definitely there. Get the kids to clean it...

wouldn't worry too much if I were you.

V.
 
kashurst said:
I also was introduced to an interesting test a few weeks back to help determine which engine is working harder (at a decent engine speed) - measure the temperature of the pipe from the turbo charger compressor side to the charge air cooler. They should be similar.
Click to expand...
That's much better than nothing, but to do that you must have an IR thermal gun and go inside the e/r.
In which case, while you are at that, you could as well go for the full monty, and measure/compare the temp of each cylinder at the respective exhaust flange.
Btw, that is even better than the EGT number which you get in the displays of electronically controlled engines, because it only gives you a sort of average for all cylinders.
By measuring them separately, on top of the possible differences between the two engines, you can also spot in advance any potential malfunctioning of a single injector.
The only drawback (aside from needing a bit more time) is that depending on the installation, the access to the external engines sides might be a PITA - particularly with the engines hot and running... :ambivalence:
 
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