Impulse force flowmeter

Due to a novel flowmeter for which a patent is pending, it is possible to measure the mass flow of a fluid independent of its material properties, by means of an impulse force measurement.

A novel flowmeter has been developed and a patent application filed for it. With this device, the mass flow of a pipe flow is determined by means of an impulse force measurement. Due to the functional principle of the novel device and the application of highly accurate force measuring techniques, it is expected that with this device, on the one hand a precision flowmeter is realised and, on the other hand, an extension of the measuring range in the field of mass flow measuring techniques can be achieved.

This novel device measures the impulse force which is exerted by a pipe flow onto a target. The target is thereby directly connected with a precision force transducer. The flow is guided in its entire cross section onto the target, abducted radially in front of the target and subsequently coupled back into the pipe system.

While the target flowmeters known so far, where the fluid flows through the annular gap between target and pipe wall, in the case of the device here presented, the fluid does not circulate around the target. The non-linear behaviour of the force impact on a target around which the fluid circulates, which is dependent on Reynold's number, is not relevant here. The mass flow can thus be determined with a high accuracy without knowing the properties of the fluid.

The impulse force  exerted by the fluid flow onto the target is proportional to the mass flow  and to the average speed  of the flow: .

If the flow velocity is known - which is rather rarely the case - one single force measurement is sufficient to determine the mass flow. Normally, the flow velocity is not known and an equation with two unknowns derives. This problem can be solved either by generating a controlled relative movement between the flow and the target or by carrying out a controlled injection of an additional mass flow. For the determination of the mass flow , only two force measurements are necessary now.

Although a first prototype, constructed with the simplest means, clearly showed that mass flow changes are measurable, it also clearly pointed out factors which can be improved. After the realisation of a second, highly improved prototype for which all these findings will be taken into account, promising measurement results are expected and will then be presented.

Contact person:

H. Többen, FB 1.5, AG 1.53, E-mail: helmut.toebben@ptb.de