Compression Ratio and HHO Self-Iginition

[JojoJaro]

Folks, I found this online calculator for computing the Efficiency of Diesel engines.

http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/diesel.html

Using my Duramax's compression ratio (16.7)and an ambient air temp of 40C, I calculated that the air inside the cyclinder at TDC is 692C. This is beyond the self-ignition temp of HHO. I then moved back and found out that a compression ratio of 12.27 will give me a temp of 580C, which is the self-ignition temp of HHO.

12.27 is 73% of 16.7. Using this percentage, I approximated that the cylinder temp of 580C is achieved at 40deg Before TDC. This means that at 40 Deg BTDC, the HHO will start igniting. 40 Deg BTDC is too soon to ignite.

The conclusion that I have come up with is that HHO may not work very well with Diesels with high compression. It seems that the self-ignition temp is reached way before TDC.

I was also assuming that the air temp injected is at ambient temp. In my experience logging these parameters on my Duramax, I have found out the Intake Air Temps are normally about 20-25F higher than ambient air temp. Which means that self-ignition temps of HHO will be reached more sooner than my calculated 40 deg BTDC.

I am making a quick assumption that the percentage of compression ratios translate directly to mechanical deg proportion. There might be a slight variation is that but I think my math is sound.

Another factor that I have not taken into consideration is how the concentration of HHO affects its self-ignition point. In other words, will a 1% concentration ignite at a higher temp than a 4% concentration of HHO. If this is true, then we may have hope yet, because our gen output is typically a very low concentration, which means that it may self-ignite at a higher temp, bringing the degrees closer to TDC, or it may not self-ignite at all.

Those of you driving gassers, you have lucked out. Your gas engines do not have a high enough compression ratio to reach the self-ignition temp of HHO. This means the only time your HHO will ignite is when that sparkplug fires.

[redneckgearhead34]

most gasoline vehicles have a compression ratio of 9.5:1 or so due to the fact that most new cars low compression ratios so that consumers can buy 89 octane gasoline with out spark knocking.

Along the line of deisels i think that is bad. Does anybody get the equivialnt of spark knocking with there deisel?

[JojoJaro]

most gasoline vehicles have a compression ratio of 9.5:1 or so due to the fact that most new cars low compression ratios so that consumers can buy 89 octane gasoline with out spark knocking.

Along the line of deisels i think that is bad. Does anybody get the equivialnt of spark knocking with there deisel?

Without HHO, it is impossible for Diesels to knock, because no combustion gas or fluid is introduced until the right time. On my diesel, the first time it will see something to combust is during the pilot injection which is at about 4 deg BTDC.

But in theory, it is possible for diesels to knock if HHO is introduced. That is the whole point of my analysis above. Although nobody seems to have experience it when they introduced HHO. Some have reported no gains or loss, which could be explained by the HHO firing too soon.

[redneckgearhead34]

I have to agree with you. I am no diesel expert ( i stil have trouble remembering how to spell it) but this explosion from the HHO that you said that would happen about 40 degrees BTDC could be the cause of the lack of gain or loss in mpg.

Also do deisels have something similiar to an o2 sensor?

[JojoJaro]

I have to agree with you. I am no diesel expert ( i stil have trouble remembering how to spell it) but this explosion from the HHO that you said that would happen about 40 degrees BTDC could be the cause of the lack of gain or loss in mpg.

Also do deisels have something similiar to an o2 sensor?


Diesels do not have o2 sensors. The soot from the exhaust will clog up the sensor in no time. Diesels always run lean so there is no point in measuring o2 at the exhaust.

[Roland Jacques]

I've read that HHO/ hydrogen can't combust if the Air to Hydrogen is above 125:1. So you can see if your HHO input is enough to even reach these ratios. ( It did not mention if that changed under pressure)

A 6 liter engine at 600 RPM idle is 3600 LPMs. So 36 LPM would be 100:1 of HHO to air. 2/3 of that is Hydrogen, so that would be 133:1 Hydrogen to air. So…

I think their is more to this. Personally I think their is early detonation going on with some diesels I'm just not 100% sure as to the why's. If you look at the Purdue U dyno test, it does show poor performance at low RPMs with HHO. I think if we could manage HHO distribution progressively (less HHO at low RPMs more as RPMs go up) it would handle this problem. But im just guessing.

[hydrotinkerer]

All diesels are high compression engines. Most of the heat applied to the cylinder is done after the valves are closed. The piston is on its way back up, compressing the air then fuel is introduced, then combusted. The way the cylinder is designed most of the heat is expelled with the exhaust, then ready for cooler incoming air.

98 Dodge cummins diesel - 19mpg to 23.5 on 700mlpm

[JojoJaro]

I've read that HHO/ hydrogen can't combust if the Air to Hydrogen is above 125:1. So you can see if your HHO input is enough to even reach these ratios. ( It did not mention if that changed under pressure)

A 6 liter engine at 600 RPM idle is 3600 LPMs. So 36 LPM would be 100:1 of HHO to air. 2/3 of that is Hydrogen, so that would be 133:1 Hydrogen to air. So…

I think their is more to this. Personally I think their is early detonation going on with some diesels I'm just not 100% sure as to the why's. If you look at the Purdue U dyno test, it does show poor performance at low RPMs with HHO. I think if we could manage HHO distribution progressively (less HHO at low RPMs more as RPMs go up) it would handle this problem. But im just guessing.

I believe a 6 liter engine at 600 RPM is 1800LPM per cylinder of air (not 3600LPM) since the engine is a 4 stoke. Hence, air is only drawn in half of the time. Total air drawn is 1800 X 8 cylinders = 14400 LPM if the turbo is not used. Since the turbo is being used, this means this value is even higher.

Adjusting the values to use 6.6L instead of 6L engine, the total air drawn by my Duramax is 1980 LPM per cylinder, or 1980 X 8 = 15840 LPM at idle or 52800 LPM at 2000 RPM. This is without the turbo.

At 52800LPM and 4 LPM HHO output, the air to Hydrogen ratio of 13200:1. Does this mean it won't self ignite?

If so, that is good news for diesel owners.

Do you remember where you read the 125:1 ratio?

Also, on your speculation of early detonation, I have theorized that the pilot injection might be responsible for detonating the entire HHO charge. This leaves no HHO to affect the main injection. On my duramax, pilot injection occurs at between 14 to 4 deg BTDC depending on RPM and load. If detonation occurs at 14 deg BTC, it is too soon.

[double it]

Just read your post and looked at the site you went to. There is a major flaw with the math at that site and with your conclusion. first off the temps do not get as hot as the formula gives because they are not taking into account the cooling affect of all the metal in the combustion chamber (surface area) this is why a diesel engines compression ratio goes down as the cylinder volumes get larger, on some of the really large diesel ships, the ratios are as low as five to one and on the really small engines it has been know to get as high as 27 to one. The total heat energy (temp) must be reached on every engine to ignite the fuel and you can look up what the temps are for a particular fuel for self ignition and that will get you fairly close to the actual temperature a diesel engine must reach. Keep in mind that the temperature window is very large when it comes to turbo charged engines. One of the biggest problems with HHO in diesels, is that the timing really needs to be retarded for best results and this can be very difficult to do. If you really want to get the best results with diesels, I would suggest that the timing be retarded with water injection and as much HHO as you can produce.

[JojoJaro]

Just read your post and looked at the site you went to. There is a major flaw with the math at that site and with your conclusion. first off the temps do not get as hot as the formula gives because they are not taking into account the cooling affect of all the metal in the combustion chamber (surface area) this is why a diesel engines compression ratio goes down as the cylinder volumes get larger, on some of the really large diesel ships, the ratios are as low as five to one and on the really small engines it has been know to get as high as 27 to one. The total heat energy (temp) must be reached on every engine to ignite the fuel and you can look up what the temps are for a particular fuel for self ignition and that will get you fairly close to the actual temperature a diesel engine must reach. Keep in mind that the temperature window is very large when it comes to turbo charged engines. One of the biggest problems with HHO in diesels, is that the timing really needs to be retarded for best results and this can be very difficult to do. If you really want to get the best results with diesels, I would suggest that the timing be retarded with water injection and as much HHO as you can produce.

What are you talking about? Diesel engine compression ratios do not go down. It is always the same for any specific engine. My Duramax always compresses air 16.7:1 wether it is hot or cold.

Sure, there is heat sinking into the surrounding metal, but that is relatively small during the fast compression timeframes we are talking about. At 2000 RPM, the piston travels from bottom to top dead center in about 15ms. There is little time for that much heat to sink to the surrounding engine.

The temps reached inside the cylinder is dependent on the compression ratio, not the type of fuel being injected. The fuel type is immaterial. The air must be compressed to a temp high enough for the fuel to ignite. The air can be compressed to a higher temp and it makes no difference what fuel you use.

[Roland Jacques]

125:1 to be "possible", a good bit lower to be probable. I read it here.
http://www.gasadvancesystem.com/Sothwest%20Research%20Test.pdf
And Smack quotes Bob Boyce in the HHO Rally video saying no way well HHO ignite at 200:1 ratio so they introduce HHO before the air filter for better more even HHO gas distribution.

Thanks for the correction, 1800 LPM air intake for a four stroke 6 liter at 600 RPM. Or for your 6.6 L at 600 RPMs = 1980LPMs. (I think your 6.6 Liter is the total volume of your engine not per cylinder.) So for your 6.6engine at 4 lpm source HHO at Idle 600RPMs is 495:1. And 1649:1 at 2000 RPMs.

Just thinking out loud. I don’t have enough info to say this is anything more than this is my hunch.
IMO there is a “Ideal Ratio” of air to HHO. I think it is around somewhere around 1500:1. Any lower air or higher HHO you may have to start playing with engine ignition timing... So maybe at low RPMs you get into early detonation because of these high ratios.

It seems to me that this Ideal ratio should be easy for someone smarter than me to figure out. Meantime I plan to stay on the low side of that ratio until I figure out a good way to make a progressive HHO distribution for my truck keeping the ratios close at all RPMs

[Roland Jacques]

That pilot injection is of concern. What is the purpose of your pilot injection?

[JojoJaro]

125:1 to be "possible", a good bit lower to be probable. I read it here.
http://www.gasadvancesystem.com/Sothwest%20Research%20Test.pdf
And Smack quotes Bob Boyce in the HHO Rally video saying no way well HHO ignite at 200:1 ratio so they introduce HHO before the air filter for better more even HHO gas distribution.

Thanks for the correction, 1800 LPM air intake for a four stroke 6 liter at 600 RPM. Or for your 6.6 L at 600 RPMs = 1980LPMs. (I think your 6.6 Liter is the total volume of your engine not per cylinder.) So for your 6.6engine at 4 lpm source HHO at Idle 600RPMs is 495:1. And 1649:1 at 2000 RPMs.

Just thinking out loud. I don’t have enough info to say this is anything more than this is my hunch.
IMO there is a “Ideal Ratio” of air to HHO. I think it is around somewhere around 1500:1. Any lower air or higher HHO you may have to start playing with engine ignition timing... So maybe at low RPMs you get into early detonation because of these high ratios.

It seems to me that this Ideal ratio should be easy for someone smarter than me to figure out. Meantime I plan to stay on the low side of that ratio until I figure out a good way to make a progressive HHO distribution for my truck keeping the ratios close at all RPMs

WOW, thanks for the correction. It never occured to me that 6.6L might be too big for 1 cylinder.

So, it seems we must figure out a way to control output based on RPM. I'm gonna have to dig thru my tech manuals again to see if I can tap the RPM signal from the OBD connector.

Also, looks like the link above is down.

[JojoJaro]

That pilot injection is of concern. What is the purpose of your pilot injection?

Yes, Pilot injection is a big concern. The pilot injection is a feature on all common rail designs. The purpose is to pre-ignite a small portion of diesel before the main injection is introduced.

By preheating the cylinder, it is supposed to lower the Diesel clatter noise, reduce vibrations, and reduce emissions.

[double it]

What are you talking about? Diesel engine compression ratios do not go down. It is always the same for any specific engine. My Duramax always compresses air 16.7:1 wether it is hot or cold.

Sure, there is heat sinking into the surrounding metal, but that is relatively small during the fast compression timeframes we are talking about. At 2000 RPM, the piston travels from bottom to top dead center in about 15ms. There is little time for that much heat to sink to the surrounding engine.

The temps reached inside the cylinder is dependent on the compression ratio, not the type of fuel being injected. The fuel type is immaterial. The air must be compressed to a temp high enough for the fuel to ignite. The air can be compressed to a higher temp and it makes no difference what fuel you use.

I think that you miss understood? Please let me clarify,

I did not say that the compression ratio varies in you engine. Smaller diesel engines with small displacement cylinders have higher ratios and larger diesel engines have lower ratios and it is also dependent on the metals used in the construction of the engine. A good example is your Duramax, It has aluminum cylinder heads which allow the combustion chamber to run at a slightly different temperature and therefore the compression ratios are different then the Cummins. If you do a search on Google, you can look up the world largest diesel on line and I believe that its compression ratio is around 4 or 5 to one and if you look up the smallest, I believe that its around 35 or 40 to one.

The temperature that is necessary to ignite a particular fuel (diesel #2) is what sets the heat parameters that must be designed into the engine which dictates the ratios for a particular engine such as your Duramax etc. If you compare turbo diesel engines with normally aspirated diesel engines you will find that the latter are usually higher in ratios because the turbos inject more air which causes higher pressures which translates into higher temperatures.

[Roland Jacques]

So, it seems we must figure out a way to control output based on RPM. I'm gonna have to dig thru my tech manuals again to see if I can tap the RPM signal from the OBD connector.


I dont think that we have to, but it makes a lot of sence to me.
Im looking into ways to make this happen on this thread, I would like more input if anyone else is interested.
http://hhoforums.com/showthread.php?t=1158

[JojoJaro]

Guys, Check out this data about Hydrogen.

Of interest to me is the Ignition Interval (concentration of Hydrogen in air) that will cause self-ignition at 520C. It is 4.1 - 72.5% concentration. Anything outside of that range, Hydrogen will not self-ignite, at least that is how I understand the data. Although I do not understand the Lower Detonation Level data (14-18%).


http://www.minihydrogen.dk/catalog/documents/materials/miniHYDROGEN_hydrogen_facts_sheet.pdf

Also check out this link. This link has a chart of the relationship of hydrogen concentration to Lower ignition level. There appears to be linear relationship between temp and Hydrogen concentration for self-ignition. The higher the temp, the lower the self ignition concentration. At 400C only 1.4% concentration will ignite. I suspect at 680C which is the cylinder temp on my Duramax at TDC, the concentration is probably 1/2 of 1.4%.

I am speculating here because the data is not completely linear. So, at 680C, I will need a concentration of .7% for self ignition. This is 46 LPM (or 69LPM of HHO) of hydrogen at 2000 RPM. (Or this is 22 LPM of HHO at 680 idle). It does not look like my measly 4 LPM production rate is going to have enough concentration to self-ignite during coasting. In fact, I have not even taken into consideration the amount of air added by the turbo, or the fact that the concentration needed increases as you increase pressure.

From this analysis, it does appear that inside the cylinder, the HHO does not reach concentrations high enough to self-ignite irregardless of compression ratio. Which means, the only mechanism for HHO to ignite is if it is ignited by the sparkplug, or by the igniting gasoline, or by the igniting diesel. Both gasoline and diesel have lower self-ignition points that hydrogen. Hence, any predetonation experienced by any engine can be attributed to detonation caused by the gasoline or diesel, not by the HHO. Any overly advance timing will exacerbate this predetonation problem. So engines should be retarded with HHO.

http://www.hysafe.org/download/1042/BRHS_Chap3_hydrogen%20ignition%20version_0_9_0.pdf

This is indeed bad news for my 'coasting' theory.

Which bring me back to my original problem of the pilot injection igniting all the HHO before the main injection is injected.

[hydrotinkerer]

Guys, Check out this data about Hydrogen.


Which bring me back to my original problem of the pilot injection igniting all the HHO before the main injection is injected.

The pilot injection doesn't burn all the fuel/air mixture in the cylinder. Pilot injection only starts the main burn cycle, like a fuse lights a fire cracker. The flame front from the pilot injection burns the rest of the injected fuel. This keeps noise down. Above 2500rpm the pilot injection is disabled.

[JojoJaro]

The pilot injection doesn't burn all the fuel/air mixture in the cylinder. Pilot injection only starts the main burn cycle, like a fuse lights a fire cracker. The flame front from the pilot injection burns the rest of the injected fuel. This keeps noise down. Above 2500rpm the pilot injection is disabled.


Yes, normally this is true. But when you add HHO, your flame front suddenly becomes significantly faster, up to 10X faster. It could burn up all your pilot charge as well as all the HHO before the HHO can modify the ignition characteristic of the main injection.

[hydrotinkerer]

Well the easiest way to answer that question is put hho on your duramax and see what it does. Thats what I did with my cummins diesel over 2 months ago

[JojoJaro]

Well the easiest way to answer that question is put hho on your duramax and see what it does. Thats what I did with my cummins diesel over 2 months ago

What year is your Cummins? Only newer common rail have pilot injections.

What LPM, amps and temps are you having on your gen? Are you getting MPG gains?

Also, I am reluctant to build an HHO genny until I am a little bit more sure I understand the process. Right now, I believe the pilot injection is going to be a problem based on my understanding of what goes on inside the cylinder.

Also, I am not as motivated to jump into this because I am already running free wvo, so my fuel only cost me $.03/gallon.

[hydrotinkerer]

98 cummins 12 valve(not a common rail)
.7 lpm, at 13amps, and 130F thats after 5hrs
19mpg base w/hho is 23mpg

The gen has a small chamber that warms up fast, Added second reservior to enable thermal exchange of catalyst. Played around for 4 months on the design. I have 2hr drive one way to work and I can't have it overheat.

I believe the pilot injection is going to make a difference, I just don't think it going to be that much. If you loose 50% it is still a gain.

Now granted your fuel cost being what it is you can't hardly beat that.

[Roland Jacques]

FREE what??? WVO? I want some, what is it?

[hydrotinkerer]

FREE what??? WVO? I want some, what is it?

Waste Vegetable Oil