Emission Controls - Technical Thread

[mydauphin]

The problem is general public thinks that bigger is better. A large boat manufacture will never advertise that their motor is smaller or produces less horsepower than the next guy. No, they want to show more horsepower, I have seen a 50 foot boat go from 300hp to 2000 hp. The boat still does 14 knots most of the time.

On water injection again, all motors prefer dry air to moist air. That is why many boats have elaborate air intake schemes to cut out moisture and salt air from air. Water injection reduces horsepower... Period

ON Boat design, I would love to have CPP prop, can't afford it. So on my boat did it old fashion away. How fast you want to go, get HP numbers, RPM, and got prop to match rpm of engines.
It turns out, I only need 250hp per engine, to achieve 14knots. So I got 300hp engines. Why get more? My engines will be properly loaded and should last forever and give best fuel economy.

On Boat Manufactures, all their anchor selections are too small.... Their engines too big.... go figure which is more important

[CDK]

Originally Posted by mydauphin

On water injection again, all motors prefer dry air to moist air. That is why many boats have elaborate air intake schemes to cut out moisture and salt air from air. Water injection reduces horsepower... Period

H2O can be considered as the combustion product of Hydrogen. Feeding that to a combustion engine again is the ultimate nonsense, unlike EGR where there is still something left to burn.
Like drinking pee or eating shit, the recipient does not benefit from it at all and it could lead to severe disorders.

The discussion about marine emission control is better served if we explore other paths.

I am not sure that smaller engines always are the answer. I made a short trip on a proud owner's brand new Bavaria, where two high-revving Mercruisers had to give all they could to maintain 25 knots and gobbled up massive amounts of fuel while doing so.

[apex1]

Originally Posted by mydauphin

On water injection again, all motors prefer dry air to moist air. That is why many boats have elaborate air intake schemes to cut out moisture and salt air from air. Water injection reduces horsepower... Period

Sorry mate I do´nt like to contradict you, but that statement is wrong. It increases power. The Formula 1 for example used WI during the 80ies and they certainly dont do anything that reduces power. Though I mentioned some of the negative effects in my former post.

Regards
Richard

[mydauphin]

Worst than disagreeing with me, you are agreeing with kristine....
Seriously, WI in and of itself looses power. Tune your engine different and it can have a cooling effect, and you add alcohol, which is a fuel to compensate power loss. But if you want power inject nitrous not water.

Going back to racing, it is amazing what blueprinting and proper tuning will do to a stock engine.

[apex1]

Originally Posted by mydauphin

Worst than disagreeing with me, you are agreeing with kristine....

Yeah mate, I did not like that either! But whats true is true, even if K. says the same. And water injection (or a water fuel emulsion to be more exact) increases power, that is a proven fact and common knowledge in the industry. Naturally it is not done the way K. would like it.

Regards
Richard

[FAST FRED]

Water injection allows an engine at 100% power to suffer detonation less.



That's its use in piston supercharged aircraft engines ,54 inches of manifold pressure with water injection ,but only 50 inches could be tolerated without the water, On a 3350ci 9 cylinders and 3 rows of cylinders round motor .

For tiny engines now stuck in cars that have 2 turbos or waste gate turbos the possibility of using water injection for even more very short term power does exist.

On a boat , unless its a dragster , or your using an old insect sprayer to get carbon out during a tune up, water isnt going to do much good.

FF

[mark775]

"...amazing what blueprinting and proper tuning will do to a stock engine." Don't forget "balancing".
Say, a few things I take issue with are no big deal but the CPP is not for every boat. I spend 95% of the time at one RPM, more or less, and a fixed prop wins out in this scenario.
Getting into efficiency but it is connected. Almost everything is common rail or unit injection (except stupid Cat ACERT) allowing what a previous post pointed out. I believe that the real efficiency gains are going to be in heat capture or generation of some type.
Does the exhaust heat capture device technology BMW has been playing with apply to diesels in boats? I don't know what it does as far as forming pollutants but a higher operating temp is better for combustion and the engines are happier. Ceramics? I do know that almost everything has higher temp thermastats these days.
Side note: New FRP exhaust upon repower last spring. D9-500 Volvo with unit injection. 700 hours. The exhaust tubing looks like the day I put it in ( No particulates ).

[mydauphin]

It is amazing that people are still trying to sell water injection as panacea. It was the rage 30 years. Install at least 10 units myself. It work on 70's cars to reduce detonation with their high comp, with lower octane gas, but at lower hp because it still require less timing. I also would modify cabs to give more gas, run rich, this help with detonation more. Obviously fuel economy was not the goal.

[CDK]

Originally Posted by apex1

Yeah mate, I did not like that either! But whats true is true, even if K. says the same. And water injection (or a water fuel emulsion to be more exact) increases power, that is a proven fact and common knowledge in the industry. Naturally it is not done the way K. would like it.

Regards
Richard

Somehow the water still manages to creep back into this thread.

Could it be that evaporating water just lowers the intake air temp. a little bit, so the air gets denser and there are a few more oxygen atoms to marginally improve the combustion?

I hope we are in agreement that H2O cannot contribute actively in any combustion process, but while wrestling with a starter motor that slowly moves itself away from the flywheel of my port engine, I got this weird idea:

The alternator on a marine engine is doing little or nothing most of the time once the starting energy has been replenished. If a small reactor vessel was added to the air intake, partly filled with water under a fine mesh separator and carbon electrodes would use the available alternator current to split H2O into H2 and O, could that contribute to lower emission?

Of course it would be possible to put a cage around the anode and cathode and just let the oxygen in, but the hydrogen as just as valuable in the combustion process. Although it will not lead to higher engine performance because of alternator load and efficiency, it may reduce CO and NOx in the exhaust gases.

Or do I overlook something?

[fasteddy106]

Originally Posted by CDK

Somehow the water still manages to creep back into this thread.

Could it be that evaporating water just lowers the intake air temp. a little bit, so the air gets denser and there are a few more oxygen atoms to marginally improve the combustion?

I hope we are in agreement that H2O cannot contribute actively in any combustion process, but while wrestling with a starter motor that slowly moves itself away from the flywheel of my port engine, I got this weird idea:

The alternator on a marine engine is doing little or nothing most of the time once the starting energy has been replenished. If a small reactor vessel was added to the air intake, partly filled with water under a fine mesh separator and carbon electrodes would use the available alternator current to split H2O into H2 and O, could that contribute to lower emission?

Of course it would be possible to put a cage around the anode and cathode and just let the oxygen in, but the hydrogen as just as valuable in the combustion process. Although it will not lead to higher engine performance because of alternator load and efficiency, it may reduce CO and NOx in the exhaust gases.

Or do I overlook something?

If you can develop that method of extracting hydrogen you will solve the energy crisis for all time and provide the world with a cheap,clean, and unlimited amount of fuel. Go for it!

[CDK]

Originally Posted by fasteddy106

If you can develop that method of extracting hydrogen you will solve the energy crisis for all time and provide the world with a cheap,clean, and unlimited amount of fuel. Go for it!

I need not develop anything because the technology is already there.
Two carbon electrodes in water, made conductive with a little salt. When an electrical current is applied, water reverts to its pre-combustion stage, H and O2. Both gases brought together again and ignited, form water again. A totally clean combustion process.
The amount of electrical energy needed to separate H2 from O is equal to the thermal energy from the explosion, so the gain is zero. In a future world without oil, this principle will be used to power aircraft. For automotive and marine use, electricity will do, but airborne vehicles need something with less weight and must carry enough energy for long distance flights.
The electricity needed for the electrolysis of water can be obtained from a number of sources like sunlight, wind, nuclear or the tide.
If you live long enough, you'll see it all happen....

[apex1]

Originally Posted by CDK

Could it be that evaporating water just lowers the intake air temp. a little bit, so the air gets denser and there are a few more oxygen atoms to marginally improve the combustion?

I hope we are in agreement that H2O cannot contribute actively in any combustion process, but while wrestling with a starter motor that slowly moves itself away from the flywheel of my port engine, I got this weird idea:

Post #41 CDK that was all I wanted to say about that issue. I am by no means a advocate of water emulsion, injection! You are right, and I said in the post mentioned, that the evaporating water increases air density. For that reason the effect is known as "active aftercooling". And for sure that is the main reason of some (small) gain in power.

And yes we are in consensus "actively" water cannot contribute.

Regards
Richard

[marshmat]

Richard,

Just to make sure we're on the same page here re. fuel grades:

The cetane number measurement used in North America assigns a value of 15 to isocetane (heptamethylnonane), and a value of 100 to cetane (n-hexadecane). The test is done in a particular standard variable-compression engine, which you run on the unknown test fuel while varying the compression ratio to get a 13-degree ignition delay (2.407 milliseconds, IIRC, at the standard test conditions). Then, leaving the compression ratio fixed, you run the engine on varying blends of cetane and isocetane until you find one that gives the same 13-degree delay; the resulting blend defines the cetane number.

Under this system, low-cetane fuels have a long ignition delay (hence "diesel knock" that occurs if ignition is delayed until a large amount of fuel has already been injected), and high-cetane fuels are very quick to ignite. In this system, a fuel's cetane number is inversely correlated with its octane number. (Our pump diesel is about 38-42 cetane; if you run it in the test engine used for gasoline, it gets an octane rating of around 50. Pump gasoline, 87 to 91 octane, has a cetane number of 15-20.)

Some other notes:

Combustion temperature- In general, a higher combustion temperature (note- combustion temperature, not intake temperature) will lead to a higher peak pressure, and a more efficient cycle, whether you use diesel or spark ignition. The main downsides to this approach are:
- Higher stress on hotter engine components (thus more complex/expensive metallurgy and possible reductions in engine life)
- Greatly increased production of nitrogen oxides
The latter point is the reason why EGR (exhaust gas recirculation) systems are fitted to most cars. Take a 4-stroke gas engine with 10:1 compression, for example, intake at SATP: adding only 5% residual gas will drop the combustion temperature from about 2300 K to about 2230 K. The result is a slight drop in cycle efficiency and a very large drop in NOx production. (Anything that reduces combustion temperature will have this same effect- high residual gas fraction, high water content intake air, etc.)

[apex1]

Originally Posted by marshmat

Richard,

Just to make sure we're on the same page here re. fuel grades:

The cetane number measurement used in North America assigns a value of 15 to isocetane (heptamethylnonane), and a value of 100 to cetane (n-hexadecane). The test is done in a particular standard variable-compression engine, which you run on the unknown test fuel while varying the compression ratio to get a 13-degree ignition delay (2.407 milliseconds, IIRC, at the standard test conditions). Then, leaving the compression ratio fixed, you run the engine on varying blends of cetane and isocetane until you find one that gives the same 13-degree delay; the resulting blend defines the cetane number.

Under this system, low-cetane fuels have a long ignition delay (hence "diesel knock" that occurs if ignition is delayed until a large amount of fuel has already been injected), and high-cetane fuels are very quick to ignite. In this system, a fuel's cetane number is inversely correlated with its octane number. (Our pump diesel is about 38-42 cetane; if you run it in the test engine used for gasoline, it gets an octane rating of around 50. Pump gasoline, 87 to 91 octane, has a cetane number of 15-20.)

Some other notes:

Combustion temperature- In general, a higher combustion temperature (note- combustion temperature, not intake temperature) will lead to a higher peak pressure, and a more efficient cycle, whether you use diesel or spark ignition. The main downsides to this approach are:
- Higher stress on hotter engine components (thus more complex/expensive metallurgy and possible reductions in engine life)
- Greatly increased production of nitrogen oxides
The latter point is the reason why EGR (exhaust gas recirculation) systems are fitted to most cars. Take a 4-stroke gas engine with 10:1 compression, for example, intake at SATP: adding only 5% residual gas will drop the combustion temperature from about 2300 K to about 2230 K. The result is a slight drop in cycle efficiency and a very large drop in NOx production. (Anything that reduces combustion temperature will have this same effect- high residual gas fraction, high water content intake air, etc.)

You are dead right Matt! I completely mixed up the Diesel and Gas behaviour!
I will edit my post. Thanks.

Regards
Richard

[Jimbo1490]

Originally Posted by mydauphin

The problem is general public thinks that bigger is better. A large boat manufacture will never advertise that their motor is smaller or produces less horsepower than the next guy. No, they want to show more horsepower, I have seen a 50 foot boat go from 300hp to 2000 hp. The boat still does 14 knots most of the time.

More watts = better sound



Jimbo