Twin fluid nozzles or pneumatic atomizers - fine and flexible atomisation

Twin fluid nozzles, also termed pneumatic atomizers or two-substance nozzles, are frequently used in process and production engineering processes. Especially where the atomization of liquids or suspensions with pressure nozzles causes problems, twin fluid nozzles may be a solution.

However, it is very important to clarify in advance whether the use of these special nozzles is possible and also sensible! Alternative nozzle and atomisation systems may also be considered. Therefore a competent consultation is absolutely necessary.

Of course, our experts will discuss the specific task together with you and help you to solve the problem!

The special feature of the twin fluid nozzles

This nozzle design has a special feature that distinguishes it from other atomizers. The energy supply for the spraying process is a gas flowing at high speed. This is in most applications compressed air. However, steam or inert gases can also be used if required.

The liquid to be atomized can therefore flow very slowly because, unlike single-substance nozzles, it does not have to supply energy. That's a big advantage. Especially when low volume flows of liquids with high viscosity have to be atomized!

A fluidic explanation of pneumatic atomizers

A short and simplified fluidic explanation.

The flow velocity of a fluid depends significantly among other properties on the pressure difference as well as on its density. Air reaches a speed of sound of approx. 340 m/s at a pressure difference of slightly more than one bar!

However, under common process conditions water flows at a pressure difference of just one bar at a maximum speed of approx. 14 m/s.

And exactly this interesting fluidic effect is widely used by twin fluid nozzles! The liquid is not to be accelerated to a high speed. It is well known that this requires high pressure differences. Rather, the high flow velocity of a gas, which is much easier to achieve, is used.

It is therefore ultimately a question of the relative velocity between the gas or the surrounding atmosphere and the liquids to be atomised. It is completely irrelevant whether a liquid jet, a drop or a lamella is to be split!

A low flow velocity for the liquid also means that high viscosities only play a minor role! And relatively large free flow cross-sections can be used. This reduces the risk of clogging.

Difficult tasks can be solved with twin fluid nozzles!

These advantages of twin fluid nozzles also make it possible to solve difficult tasks in atomisation technology. And we are your partner in solving these difficult tasks! Because we not only have extensive practical experience here, but also specialists who have a scientifically founded know-how in the field of multiphase flows!

In the following just a few examples of individual developments:

Nozzle lance with two-substance nozzle. This pneumatic atomizer is steam-heated and atomizes highly viscous liquids into fine droplets.

This special nozzle lance was developed on behalf of and in cooperation with a well-known partner from the chemical industry. It is steam-heated to reduce the viscosity of the liquid to be atomized.

With this nozzle lance, considerable volume flows of a highly viscous melt are atomized to fine drops. The measured maximum droplet diameter in the spray is less than 20 µm. A protective screening of the product is no longer necessary. Clear advantages could thus be realized.

This nozzle lance has been in operation without malfunctions for several years.

Special development of a two-substance nozzle. This can fine atomize small quantities of liquid with low gas consumption.

A further development of IBR Zersäubungstechnik GmbH is a twin fluid nozzle for atomizing small amounts of liquid into fine droplets. One of the requirements of the client was that the nozzle itself should be self-priming. The nozzle had to be emptied after completion of the spraying process. Furthermore, hygienic aspects must be taken into account.

This nozzle is now used in large quantities worldwide.

Twin fluid nozzles have advantages and disadvantages

As with any nozzle type, there are specific advantages and disadvantages. This also applies to pneumatic atomizers. That is why it is so important to look closely at a nozzle technology in view to the planned application.

This nozzle technology also distinguishes between the atomizers of the outer mixing and the atomizers of the inner mixing. Here, too, there are very specific characteristics which must be taken into account.

By mischance, twin fluid nozzles cannot be reliably calculated numerically so far. It is certainly not possible to calculate droplet size distributions at these atomizers in advance. If necessary, real drop size measurements must be carried out. Of course we can also can do this for you!

Advantages and disadvantages briefly contrasted:

Twin fluid nozzles can also atomize low volume flows of viscous liquids into fine droplets. Here, pressure nozzles often fail.

The flow rate of the liquid in pneumatic atomizers can be controlled over a wide range. For pressure nozzles, this is only possible via the pressure difference Δp. At the same time, this has a significant influence on the droplet size distribution.

Depending on the lay out of the nozzle, it can be designed to be much less sensitive to blockages than pressure nozzles. This is particularly advantageous when spraying soiled liquids or suspensions.

The spray momentum is high due to the flowing gas. Depending on the application, this can be advantageous or even hindering. This must be assessed for each respective application. The generation of compressed air or another compressed gas (inert gas) is energetically unfavourable.

In certain processes, no additional gases must be introduced. Then the use of this nozzle design is ruled out. In this case alternative nozzle techniques are required.

There are many aspects to consider when choosing a twin fluid nozzle

Basically always with regard to the desired result! Here it is completely irrelevant whether it concerns the cooling of gases, the targeted coating or cooling of surfaces or the combustion technology.

When developing or optimizing a production or process engineering system, it is always very important to see the potential, but also the limits, of a particular nozzle technology. And this in connection with the desired overall result.

If this is neglected, serious problems often arise. This results in complex and costly changes in the system technology.

Our special service in the field of twin fluid nozzles for you!

After a detailed discussion of your task, we either suggest suitable pneumatic atomizers or recommend alternative nozzle technologies. If twin fluid nozzles are considered, we first check whether commercially available products are suitable for you. If this is the case, we procure the required number of the suitable nozzle for you.

If standard nozzles do not fit, we would be happy to develop and optimize a special atomizer on your behalf. This is then exactly adapted to your needs. Of course, all technical possibilities are available for this. This also includes nozzle test benches with appropriate spray measurement technology.

Would you like comprehensive information?

Then you will receive complete diagrams for the operation of your special twin fluid nozzle on request! We create these to atomize your original fluid. If this is not possible, we provide model fluids with almost identical rheological properties. The characteristic diagrams can thus be used to react flexibly to changing operating conditions or changes in rheology.

A service that would elsewhere be hard to find!

Advice on twin fluid nozzles and possible applications!

It is therefore essential that you discuss your planned application with our specialists. Already with a first noncommittal telephone call it can be clarified frequently whether twin fluid nozzles are considered for the solution of your tasks or alternative nozzle systems are better solutions.

Our experts will be happy to advise you and answer your questions about twin fluid nozzles

During office hours we will be happy to connect you directly with a specialist for twin fluid nozzles. Discuss your task with him/her and benefit immediately from our service.

Of course you can also use our contact form. Simply describe your task briefly.

We will then contact you; guaranteed!