|
||||||||||||
|
||||||||||||
| flowing N2O through a restriction | |||
| Post Reply | Forum | ||
| Posted by: CCR5600Design ® 10/08/2007, 13:52:52 Author Profile eMail author Edit |
Hi folks! I need some help. I work for a racing sanctioning body which allows the use of nitrous oxide as a power adder in some of its classes. Some questions have arisen pertaining to its use and I figured I would go to the brainbank to get some answers. First, a bit of reference material. Nitrous oxide has been used as a power adder (oxidizer) since WWII with exceptional results. When injected into the intake tract of an internal combustion engine, nitrous oxide offers a cooling effect on the intake charge as it vaporizes, thus increasing the charge density and offering additional oxygen to the combustion process. When additional fuel is added to the mixture, more horsepower is gained. To restrict the amount of horsepower in the racing classes, the sanctioning body restricts the size of the orifice the nitrous oxide must pass through before it is injected into the intake tract. In this particular class, the orifice is restricted to a single 0.098" diameter jet. This limits the amount of oxygen present during the combustion process. A racer recently approached the rules committee with a proposal. Due to the design of a particular make and model of domestic V8 intake manifold, the nitrous oxide is not distributed equally to all the cylinders of the engine resulting in some cylinders burning lean and some cylinders burning rich. He asked if he could use TWO nitrous oxide jets of 0.069" diameter at opposing ends of the intake tract to better distribute the nitrous oxide. The rules committee responded that they would consider the use of a pair of 0.049" jets (0.098" divided by 2) and I had to inform them that they were in error in their math. As I figured it, the racer did the proper calculations for the area of the jets, but I am not certain what effect the pressure of the nitrous oxide system would have on the flow through 2 smaller orifices rather than one large orifice. Herein lies my question. With a bottle pressure of roughly 1200 psi, will a pair of 0.069" diameter jets flow the same amount of liquid N2O as a single jet of 0.098" diameter? If there is a difference, what size would the pair of smaller jets need to be to flow equal to the single 0.098" diameter jet? Thanks, Ron "What we need are more people who specialize in the impossible." - Theodore Roethke |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
View All | | Next | |
| Replies to this message |
| Re: flowing N2O through a restriction | |||
| Re: flowing N2O through a restriction -- CCR5600Design | Post Reply | Top of thread | Forum |
Posted by: randykimball ®  10/08/2007, 14:42:01 Author Profile eMail author Edit |
Clearly you are correct, .049 is half of .098 diameter but is not half the area. Half the area of a .098 diameter jet is .06934. It is all about the cross sectional area of the jet size. Actually the racer is offering to very slightly reduce his flow in favor of better mix. ...a slick idea... For the sake of comparison: The force (tossing out flow dynamics) at a .098 jet opening at 1200 PSI is the area of the jet (.0075429) times the full pressure. ... this comes to a relative value of 9.05148. The force (tossing out flow dynamics) at a .o69 jet opening at 1200 PSI is the area of the jet (.0037392) times the full pressure. ... this comes to a relative value of 4.48704. Clearly this is slightly half the force provided for with the .098 jet. For the racer to get the same flow rate he will need to double the .069 jet size or use two jets. Even then he will be getting flow based on a total jet area of 8.97408 which is to say he will get 99.14 % of the flow at a .098 jet. But, additionally he has induced more resistance along the walls of the the two jets as he now has more skin effect. The .098 jet will have 71% of the skin (circumference) as the two .069 jets. Will this added skin effect caused pressure drop add power or decrease power??..... I dauh know....
..This could be very interesting... The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Mon, Oct 08, 2007, 15:13:34 |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Re: flowing N2O through a restriction | |||
| Re: Re: flowing N2O through a restriction -- randykimball | Post Reply | Top of thread | Forum |
| Posted by: jboggs ® 10/08/2007, 17:42:57 Author Profile eMail author Edit |
OK Randy buddy, I'll bite. You've got me confused. I'll admit that my last fluid dynamics course was 30 years ago, but . . . You say "For the racer to get the same flow rate he will need to double the .069 jet size or use two jets." Huh? I thought that was the plan. Two .069 jets. What do you mean by "double the .069 jet size"? According to your calculations it appears that two .069 jets will give him better than 99% of the flow of a single .098 jet. Yes the effects of other flow considerations (friction, corner losses, etc.) are unknowable, but I would think that the advantage of having two remote insertion points in a common manifold would probably override all of that. I would also think that they could minimize those other effects with some attention to system design. For what its worth. |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Re: Re: flowing N2O through a restriction | |||
| Re: Re: Re: flowing N2O through a restriction -- jboggs | Post Reply | Top of thread | Forum |
| Posted by: randykimball ® 10/08/2007, 23:16:12 Author Profile eMail author Edit |
Exactly, I am saying that .049 is not the correct answer.
Two .069 jets is the right jet size to provide the close to equal flow as one .098 jet. I guess my wording is confusing. ... ok... ? ..big smile... .... Double .069 jet size is .098, or two .069 jets are both, math wise, fair.
So... we agree???
The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Mon, Oct 08, 2007, 23:39:26 |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Re: Re: Re: flowing N2O through a restriction | |||
| Re: Re: Re: Re: flowing N2O through a restriction -- randykimball | Post Reply | Top of thread | Forum |
| Posted by: jboggs ® 10/09/2007, 09:46:47 Author Profile eMail author Edit |
We agree. |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread | | | |
| Re: Re: Re: Re: Re: flowing N2O through a restriction | |||
| Re: Re: Re: Re: Re: flowing N2O through a restriction -- jboggs | Post Reply | Top of thread | Forum |
| Posted by: CCR5600Design ® 10/09/2007, 11:15:07 Author Profile eMail author Edit |
Randykimball and jboggs, Thanks for your replies and good information. I was interested in the frictional losses and such as mentioned by jboggs and was wondering what effect they would have but I had not considered the benefits of the dual-jet system outweighing the losses through friction. Good point. Just as an FYI, the racers are restricted to a single "plate-style" injector which is placed between the throttle body/carburetor and the intake manifold. Direct port or "fogger" systems are not allowed. These direct port systems are much more efficient and produce more consistent combustion mixtures than the plate system but are not as easy to police and are quite a bit more expensive. I will use the information you have given to make a case to the rules committee and let them form their own opinions based on fact. Thanks again, Ron "What we need are more people who specialize in the impossible." - Theodore Roethke |
| Post Reply Tell a Friend (must be logged in) Alert Admin About Post |
Where am I? Original Top of thread |
Powered by Engineers Edge
© Copyright 2000 - 2024, by Engineers Edge, LLC All rights reserved. Disclaimer
