Heat transfer, myth, theory, speculation...
04-16-2008, 03:07 PM
#22
My head hurts...
For the sake of the community i came up with a somewhat simple test.
We need a willing guinea pig that meets the criteria.
Criteria:
1. Forced induction.
2. Fabrication skills and some free time to devote to testing.
3. WI.
4. EGT sensor (preferably 4 of them, one on each runner to measure consistence across the board)
5. Tuning capabilities
6. Patience.
7. Brains.
8. *****.
9. Typing skills to let us all know without getting himself banned.
Is there such a person that owns a miata?
Series of Tests:
1. Install WI the traditional way (i guess before TB)
-take notes on ambient temps, boost levels, and EGT's
2. Install WI nozzles in the manifold plenum(2 nozzles, one between each runer)
-take notes on ambient temps, boost levels, and EGT's
3. Install WI the way I plan to do mine (4 nozzles, one on each runner as close to the head as possible without interfering with the injectors)
-take notes on ambient temps, boost levels, and EGT's
4. Let everyone know what the results are so we may finaly come to a conclusion.
5. Drink beer, on me!
I am willing to donate a 1.8 manifold if test car is a 1.8 (94-97) and some money toward nozzles or just some nozzles.
What does everyone think of this?
Cheers,
Dan
For the sake of the community i came up with a somewhat simple test.
We need a willing guinea pig that meets the criteria.
Criteria:
1. Forced induction.
2. Fabrication skills and some free time to devote to testing.
3. WI.
4. EGT sensor (preferably 4 of them, one on each runner to measure consistence across the board)
5. Tuning capabilities
6. Patience.
7. Brains.
8. *****.
9. Typing skills to let us all know without getting himself banned.
Is there such a person that owns a miata?
Series of Tests:
1. Install WI the traditional way (i guess before TB)
-take notes on ambient temps, boost levels, and EGT's
2. Install WI nozzles in the manifold plenum(2 nozzles, one between each runer)
-take notes on ambient temps, boost levels, and EGT's
3. Install WI the way I plan to do mine (4 nozzles, one on each runner as close to the head as possible without interfering with the injectors)
-take notes on ambient temps, boost levels, and EGT's
4. Let everyone know what the results are so we may finaly come to a conclusion.
5. Drink beer, on me!
I am willing to donate a 1.8 manifold if test car is a 1.8 (94-97) and some money toward nozzles or just some nozzles.
What does everyone think of this?
Cheers,
Dan
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04-16-2008, 03:28 PM
#23
Boost Czar
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Join Date: May 2005
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/hijack.
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04-16-2008, 03:35 PM
#24
Ger, typed it all and lost it. Typing again...
The ideal place to inject the water/fuel/nitrous/propane/etc. would be directly into the cylinder right before combustion. It's flat out more efficient as the fuel/water would remove more heat from the charge.
If you sprayed the water at the begining of the compression stroke directly into the cylinder, some of the water would end up cooling the cylinder walls, combustion chambers, pistons, etc and not pulling heat out of the charge.
If you spray it right before the intake valves, the water is also cooling a bit of the intake manifold, the runners in the head, and the intake valves and seats as well.
Spraying it before the TB and now your cooling the TB and intake manifold as well.
There are other reasons to spray further away from the cylinders, but it's not for maximum reduction of charge cooling (it is and it ain't). It's for better distribution purposes in a single fogger setup. Direct port would be ideal in these situations.
The ideal place to inject the water/fuel/nitrous/propane/etc. would be directly into the cylinder right before combustion. It's flat out more efficient as the fuel/water would remove more heat from the charge.
If you sprayed the water at the begining of the compression stroke directly into the cylinder, some of the water would end up cooling the cylinder walls, combustion chambers, pistons, etc and not pulling heat out of the charge.
If you spray it right before the intake valves, the water is also cooling a bit of the intake manifold, the runners in the head, and the intake valves and seats as well.
Spraying it before the TB and now your cooling the TB and intake manifold as well.
There are other reasons to spray further away from the cylinders, but it's not for maximum reduction of charge cooling (it is and it ain't). It's for better distribution purposes in a single fogger setup. Direct port would be ideal in these situations.
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04-18-2008, 03:08 AM
#25
My head hurts...
For the sake of the community i came up with a somewhat simple test.
We need a willing guinea pig that meets the criteria.
Criteria:
1. Forced induction.
2. Fabrication skills and some free time to devote to testing.
3. WI.
4. EGT sensor (preferably 4 of them, one on each runner to measure consistence across the board)
5. Tuning capabilities
6. Patience.
7. Brains.
8. *****.
9. Typing skills to let us all know without getting himself banned.
Is there such a person that owns a miata?
Series of Tests:
1. Install WI the traditional way (i guess before TB)
-take notes on ambient temps, boost levels, and EGT's
2. Install WI nozzles in the manifold plenum(2 nozzles, one between each runer)
-take notes on ambient temps, boost levels, and EGT's
3. Install WI the way I plan to do mine (4 nozzles, one on each runner as close to the head as possible without interfering with the injectors)
-take notes on ambient temps, boost levels, and EGT's
4. Let everyone know what the results are so we may finaly come to a conclusion.
5. Drink beer, on me!
I am willing to donate a 1.8 manifold if test car is a 1.8 (94-97) and some money toward nozzles or just some nozzles.
What does everyone think of this?
Cheers,
Dan
For the sake of the community i came up with a somewhat simple test.
We need a willing guinea pig that meets the criteria.
Criteria:
1. Forced induction.
2. Fabrication skills and some free time to devote to testing.
3. WI.
4. EGT sensor (preferably 4 of them, one on each runner to measure consistence across the board)
5. Tuning capabilities
6. Patience.
7. Brains.
8. *****.
9. Typing skills to let us all know without getting himself banned.
Is there such a person that owns a miata?
Series of Tests:
1. Install WI the traditional way (i guess before TB)
-take notes on ambient temps, boost levels, and EGT's
2. Install WI nozzles in the manifold plenum(2 nozzles, one between each runer)
-take notes on ambient temps, boost levels, and EGT's
3. Install WI the way I plan to do mine (4 nozzles, one on each runner as close to the head as possible without interfering with the injectors)
-take notes on ambient temps, boost levels, and EGT's
4. Let everyone know what the results are so we may finaly come to a conclusion.
5. Drink beer, on me!
I am willing to donate a 1.8 manifold if test car is a 1.8 (94-97) and some money toward nozzles or just some nozzles.
What does everyone think of this?
Cheers,
Dan
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j/k
04-25-2008, 07:34 PM
#27
Ok, time for more myth and speculation. I formed my own opinion on how WI helps and how it works, and it's pretty much what Mr. Perez spelled out in his first post. However, this guy sees it differently. He's on HomeMadeTurbo, and the guy wrote the sticky for their WI faq. Have a look here:
http://www.homemadeturbo.com/forum/i...?topic=88312.0
Yes it adds oxygen. An oxidant is something that readily accepts electrons. Water is amphoteric, and because of this it can dissociate if it's bombarded by ionized molecules, like you have in super excited reactions (i.e. really high pressure ones). Long chain aliphatic hydrocarbons have a lot of love to give, generally having less C=C bonds don't have as high of a potential as the supplemented aromatics that are used, they still readily form C-OH bonds upon compression and ****** up hydrogen cations like no tomorrow.
The presence of hydroxides and hydrogen ions is what really enhances deflagration and ups the required activation energy of the reaction.
As far as being able to burn the water I think you're neglecting stoichiometric ratio for the charge you're putting into the cylinder, there still has to be enough heat and ionized hydrocarbons to get the water to dissociate in order for it to "burn" properly. A large amount of activation energy is required to have the water enter a transition state as well, liquid water doesn't burn.
Essentially water is somewhat of a catalyst that raises the amount of heat you can throw at the charge before it ignites, as well as raising the density of the charge overall just by evaporation (lower heat levels).
I'm going to go tend to my hangover now.
WTF? Since when does water act as an oxidizer? I'm not buying all this. Granted I've forgotten what some of those words mean. I still don't think he's right. I'm doing more research now but what does everyone think of this? Any chemical engineers want to confirm/deny his post?
http://www.homemadeturbo.com/forum/i...?topic=88312.0
Here's the part that I wrote questioning him and his response:
For the most part I agree with everything you've said, but this part not so. Are you saying that spraying water in the motor adds oxygen? Or are you saying it will suppress detonation and allow you to add more oxygen to make more power? I'll agree with the later. I think that's what your saying, but it's wordy at best. No, now I see you do say it's an oxidizer in a combustion event. How so? I don't think that's correct. If it did, then the hydrogen would react with the oxygen. If that were so, then we could simply spray LOTS of water in the motor with just enough fuel to get the reaction going. In this case we wouldn't need a turbocharger at all, just gas and air to get the reaction going to burn the water.
In simple terms, the water goes through a phase change during the compression stroke, which removes a significant amount of heat from the charge, suppressing detonation. In turn, you can now effectively increase boost to add more oxygen.
For the most part I agree with everything you've said, but this part not so. Are you saying that spraying water in the motor adds oxygen? Or are you saying it will suppress detonation and allow you to add more oxygen to make more power? I'll agree with the later. I think that's what your saying, but it's wordy at best. No, now I see you do say it's an oxidizer in a combustion event. How so? I don't think that's correct. If it did, then the hydrogen would react with the oxygen. If that were so, then we could simply spray LOTS of water in the motor with just enough fuel to get the reaction going. In this case we wouldn't need a turbocharger at all, just gas and air to get the reaction going to burn the water.
In simple terms, the water goes through a phase change during the compression stroke, which removes a significant amount of heat from the charge, suppressing detonation. In turn, you can now effectively increase boost to add more oxygen.
The presence of hydroxides and hydrogen ions is what really enhances deflagration and ups the required activation energy of the reaction.
As far as being able to burn the water I think you're neglecting stoichiometric ratio for the charge you're putting into the cylinder, there still has to be enough heat and ionized hydrocarbons to get the water to dissociate in order for it to "burn" properly. A large amount of activation energy is required to have the water enter a transition state as well, liquid water doesn't burn.
Essentially water is somewhat of a catalyst that raises the amount of heat you can throw at the charge before it ignites, as well as raising the density of the charge overall just by evaporation (lower heat levels).
I'm going to go tend to my hangover now.
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04-25-2008, 10:14 PM
#28
I fully and completely agree with this hypothesis. On what basis? Well, thermodynamics not being my forte, I decided to search the SAE paper database on the subject of water injection.
And not a SINGLE paper made reference to, or presented data on, intake air temperatures so much as in-cylinder temperatures or pressure-time plots.
I dont know if you've read this: "End Zone Water Injection as a means of suppressing knock in a Spark-Ignition engine", NACA Wartime Report, Sept. 1944. It talks about direct injection of water into the cylinder on the compression stroke, and optimising the injection angle and the water-fuel ratio. They found that at 60 deg. BTDC and a water-fuel ratio of 0.5, the octane requirement of the engine reduced by 80 octane points!! In other words, 20 octane + WI = 100 octane with everything else kept constant. The implication for us, since we already have 93 octane available, is that we can run more boost with more advance than is otherwise possible.
Its also a known fact that water slows down the flame front and that is the primary reason for it being an excellent knock suppressant. As you said before, the reduction in intake air temperature due to WI is, at best, insignificant, and at worst, irrelevant. Ricardo is developing a turbocharged engine which they call lean-boost DI: the concept is that the direct injection of fuel takes care of the in-cylinder charge temperature at the end of the compression stroke, and they actually use excess air (like 18:1 AFR) at maximum boost to actually act as a knock suppressant.
I am pretty sure that one could very safely say, that the yo-yo guy would have much, much better luck with this 5th injector device if it were fed with a water-alcohol mixture rather than gasoline.
And not a SINGLE paper made reference to, or presented data on, intake air temperatures so much as in-cylinder temperatures or pressure-time plots.
I dont know if you've read this: "End Zone Water Injection as a means of suppressing knock in a Spark-Ignition engine", NACA Wartime Report, Sept. 1944. It talks about direct injection of water into the cylinder on the compression stroke, and optimising the injection angle and the water-fuel ratio. They found that at 60 deg. BTDC and a water-fuel ratio of 0.5, the octane requirement of the engine reduced by 80 octane points!! In other words, 20 octane + WI = 100 octane with everything else kept constant. The implication for us, since we already have 93 octane available, is that we can run more boost with more advance than is otherwise possible.
Its also a known fact that water slows down the flame front and that is the primary reason for it being an excellent knock suppressant. As you said before, the reduction in intake air temperature due to WI is, at best, insignificant, and at worst, irrelevant. Ricardo is developing a turbocharged engine which they call lean-boost DI: the concept is that the direct injection of fuel takes care of the in-cylinder charge temperature at the end of the compression stroke, and they actually use excess air (like 18:1 AFR) at maximum boost to actually act as a knock suppressant.
I am pretty sure that one could very safely say, that the yo-yo guy would have much, much better luck with this 5th injector device if it were fed with a water-alcohol mixture rather than gasoline.
And I think you guys are missing an important aspect of water injection. Wet bulb temperature which allows you to have below ambient temperatures
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05-08-2008, 04:07 AM
#29
Junior Member
Join Date: Mar 2007
Location: Auckland, NZ
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since someone asked... here's stuff outlining the chemistry of WI:
http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=1039
http://www.faqs.org/faqs/autos/gasoline-faq/part3/ --sec 7.13
http://www.eng-tips.com/faqs.cfm?fid=811
basically it assists in combusting CO to CO2. I think.
http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=1039
http://www.faqs.org/faqs/autos/gasoline-faq/part3/ --sec 7.13
http://www.eng-tips.com/faqs.cfm?fid=811
basically it assists in combusting CO to CO2. I think.
...Then consider that pure CO and pure O2 burns very slowly if at all. Virtually
the only mechanism to complete the oxidization ( Glassman - Combustion Third
Edition ) of CO ==> CO2 is the "water method".
CO + OH ==> CO2 + H
H + OH ==> H20
H2O + O ==> H2O2
H2O2 ==> OH + OH
goto to top and repeat.
This simple reaction accounts for 99% + of the conversion of CO to CO2. It is important in that fully two thirds of the energy of carbon combustion is
released in the CO ==> CO2 process and that this process occurs slow and late in the combustion of the fuel. Excess water can and does speed this
conversion - by actively entering into the conversion process thru the above
mechanism.
the only mechanism to complete the oxidization ( Glassman - Combustion Third
Edition ) of CO ==> CO2 is the "water method".
CO + OH ==> CO2 + H
H + OH ==> H20
H2O + O ==> H2O2
H2O2 ==> OH + OH
goto to top and repeat.
This simple reaction accounts for 99% + of the conversion of CO to CO2. It is important in that fully two thirds of the energy of carbon combustion is
released in the CO ==> CO2 process and that this process occurs slow and late in the combustion of the fuel. Excess water can and does speed this
conversion - by actively entering into the conversion process thru the above
mechanism.
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