An ideal venturi

Edits and changes to engines, experiences, findings and ideas.
Other
Pantone engine Researcher
Pantone engine Researcher
posts: 3787
Registration: 17/03/05, 02:35
x 12

An ideal venturi




by Other » 12/06/07, 03:48

Hello
On different works we have different angles for the construction of the venturis
Normally in the technical books we talk about 30 degrees for entry and 7 degrees for exit
measured as a function of the reference line, i.e. a total angle of 60 degrees at entry and 14 degrees at exit,

To have measured on several industrial ventutris these values ​​vary for the exit it is from 8 to 12 degrees, but for the entry we have different values ​​certain 30 degrees other 50 degrees and other arcuate forms most often in carburetor nozzles, outlet lengths also vary.


It should be known theoretically which the best venturi design.
which gives the least pressure drop
who gives the most depression

Andre
0 x
User avatar
pollux
I understand econologic
I understand econologic
posts: 164
Registration: 07/05/06, 23:08
Location: Paris
x 1




by pollux » 12/06/07, 07:38

Hello,

I'll tell you what I learned in the course of fluid mechanics:
the convergent does not matter, the air always accelerates very easily. however, if you want constant acceleration, your section should decrease quickly at first, then more and more slowly. roughly, the "profile" of your convergent walls must be of the same shape as the "square root" function. (I don't know if it's very clear ...).

the divergent on the other hand is very delicate. above 7 ° (14 ° if we count the two walls), the boundary layer becomes detached and recirculation zones are created. below these 7 °, the flow remains straight, the boundary layer sticks well, and the deceleration is smooth.

now, I have not yet fully understood the role of this venturi, and I therefore do not know if it is better to have a very clean venturi that does not generate turbulence (in which case you need a well rounded inlet and an outlet <7 °) or else if it is preferable to trigger the turbulence to mix the gases well and avoid excessive pressure drops due to a hypothetical laminar flow (in this case, a venturi made up of two cones one in the other with a divergent at 7 or 8 °, but there, hello turbulence).

here, I summarized you what I knew. if you have a specific question, i can try to answer it.
I will look in my books, but I believe that we have never been given the ideal shape of a venturi. a shame for an aeronautical engineering school ... : Shock:
0 x
criticism is necessary, but the invention is vital because in any invention there is a criticism of the convention ...
User avatar
Capt_Maloche
Moderator
Moderator
posts: 4559
Registration: 29/07/06, 11:14
Location: Ile-de-France
x 42




by Capt_Maloche » 12/06/07, 12:15

This is just the application of Bernouilli's theorem

The cones must be progressive and the elongation depends on the density of the fluid used (Reynolds nbr)

the system can also be improved by using an inverted Pitot tube placed directly under vacuum in the rapid fluid flow (at the site of the narrowing); in this case, no need for a lot of calculations :D

There is also the principle of gas injectors, a nozzle (injector) pulses gas at high speed in an open cone, the gas jet induces air movement (make-up) up to 10 times the volume of gas displaced

By the way, for what application?
0 x
"Consumption is similar to a search consolation, a way to fill a growing existential void. With, the key, a lot of frustration and a little guilt, increasing the environmental awareness." (Gérard Mermet)
OUCH, OUILLE, OUCH, AAHH! ^ _ ^
Other
Pantone engine Researcher
Pantone engine Researcher
posts: 3787
Registration: 17/03/05, 02:35
x 12




by Other » 12/06/07, 15:25

Hello

the application is to place in the manifold of the diesel engine.
its role is especially to increase the depression in the reactor or rather to suck more humid air in the panton,
what we are looking for is to make as little pressure drop as possible in the intake (which penalizes us at full power on diesel lack of air.)
with a simple restriction exceed 75% of power the engine heats a little more (an engine which heats it is in pure loss)
if there is a little turbulence it is tolerable, but not
too much this venturi is placed in front of the turbo, it is preferable that what enters the turbo is laminar (although I can add a honeycomb of Mass air flow from GM)
Let’s say for the moment I favor the operation of the panton reactor to the detriment of the engine if necessary. therefore the maximum suction at the neck of the venturi

The measured models it is on venturi (trumpet) that we find on the old planes to operate the gyroscopes a speed of 150kmh is enough to make them functional j, have a simple model is a model double cone on the model double venturi angles are different entered is exited
I also measured on a venturi pump for water the 7 degree is respected but not the 30 degree.

Andre
0 x
User avatar
Capt_Maloche
Moderator
Moderator
posts: 4559
Registration: 29/07/06, 11:14
Location: Ile-de-France
x 42




by Capt_Maloche » 12/06/07, 21:50

hi Andrew

The depression is such that when the turbo is aspirated that you will not need a venturi !!
0 x
"Consumption is similar to a search consolation, a way to fill a growing existential void. With, the key, a lot of frustration and a little guilt, increasing the environmental awareness." (Gérard Mermet)
OUCH, OUILLE, OUCH, AAHH! ^ _ ^
User avatar
PITMIX
Pantone engine Researcher
Pantone engine Researcher
posts: 2028
Registration: 17/09/05, 10:29
x 17




by PITMIX » 12/06/07, 23:03

Hello
The use of the venturi in our case only serves to siphon the air from the reactor.
The goal is to make the air accelerate as much as possible in the venturi but by limiting pressure losses as much as possible.
In the case of its use for spraying water only the most violent turbulence possible is sought in order to spray as finely as possible.
I have noticed that a simple restriction of the intake air vein fulfills the role asked of it.
A perfect venturi would certainly provide better performance.
Regarding the shape of the venturi to spray water I think that an approximate shape does not give the expected results.
The air speed is not sufficient to properly spray the water.
Do you think we can compare the effect of spraying water subjected to a venturi with air under pressure and a venturi with air under pressure?
It seems to me that in depression water tends to be sucked very strongly and the air sprays water weakly.
On the contrary, under pressure, I have the impression that the water is correctly sprayed without it being evacuated in too large an amount.
0 x
Other
Pantone engine Researcher
Pantone engine Researcher
posts: 3787
Registration: 17/03/05, 02:35
x 12




by Other » 13/06/07, 04:36

Hello

a new venturi that I just made today, smaller diameter inlet 60 degrees outlet 7 degrees stitching at 1/3 of the diameter behind the neck stitching tube 12,7 mm
Normally the temperature leaving the reactor should drop (increase in the passage of moist air through the reactor)
tested over 40 km tonight the temperature is still above 130c
it keeps me reducing the water consumption to see if it has increased

Image

A reactor that runs the copper pipe has this internal color

Image

Image

The probe penetrates inside the copper tube so as not to be affected by the temperature of the copper conduit which cools in the air flow.

Image

The venturi is placed in the nose of the turbo with a protective mesh the mesh makes more pressure losses than the venturi
anyway I rarely drive at 160kmh ..
0 x
User avatar
PITMIX
Pantone engine Researcher
Pantone engine Researcher
posts: 2028
Registration: 17/09/05, 10:29
x 17




by PITMIX » 13/06/07, 08:46

hi Andrew
Regarding the temperature increase this corresponds to the measurements that I have made.
The more suction in the reactor, the higher the temperature of the outlet tube.
Besides, on my super5 the temperature of the reactor outlet tube could rise to 300 ° C with very little water when the reactor was connected under the fuel.
It was subjected to a depression ranging from 1 to 4m of water column.
Today, connected directly to the air filter, the temperature barely reaches 100 ° C. Nothing has changed except the air flow through the reactor.
Another observation, if you cut the water and you block the air intake you will measure only the thermal conduction. In the Super5 in this case the temperature reached 50 to 80 ° C depending on the engine load.
Very nice work of realization on your venturis.
0 x
jeannot
I learn econologic
I learn econologic
posts: 19
Registration: 09/10/06, 10:17




by jeannot » 17/07/07, 16:45

Hello,

I try to run a reactor without mounting it on an engine; only by vacuuming through a compressor.
I do not understand why you are looking to get a lot of depression.
In your assemblies with GV, the depression is practically zero
at the entrance, otherwise you suck water !? no ? did I miss something?

I measure the depression at the outlet of the reactor, it is a function only of the air flow which passes inside

here is the montage I made; unfortunately I can't get it started; is there an assembly error?


Image

Here are some values ​​that I noted

air speed in the reactor about 25 m / s depression 26mmce
50 m / s depression 105 mmce

80 m / s depression 160 mmce

note: I heat the air with a heat gun; at the outlet, I heat the water in my steam generator to around 80 ° c
the SG is open at atmospheric pressure; the steam intake is in diameter 18 and perforated with ten small 2mm holes to mix air and steam

I let it run for 1/2 hour, but no ionization or priming ????

Any ideas !!

Jeannot
0 x
Other
Pantone engine Researcher
Pantone engine Researcher
posts: 3787
Registration: 17/03/05, 02:35
x 12




by Other » 17/07/07, 16:57

Hello
I do not understand why you are looking to get a lot of depression.
In your assemblies with GV, the depression is practically zero
at the entrance, otherwise you suck water !? no ? did I miss something?

In the GV the depression is weak, but after the GV there is an air inlet and for the reactor to work it is necessary to make circulate the air is the vapor in the reactor, if not it will not happen much.
Either you put a venturi, or you pump, or you make a restriction and the motor pumps.

Andre
0 x

 


  • Similar topics
    Replies
    views
    Last message

Back to "Water injection in the engines: the assembly and experimentation"

Who is online ?

Users browsing this forum : No registered users and 122 guests