Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
R.G. van Wachem Revolver Venturi or increased range venturi flow meter as part of a multi-phase flow measurement system. Masters thesis, Report 92.3.OS.2958, Transport Engineering and Logistics / Offshore Engineering.
A venturi flow meter with a 'variable' throat diameter, as part of a multi-phase flow measurement system, has been designed and tested.
One possible concept for a multi-phase flow meter, consists of rough separation of liquid and gas, measuring the components, oil, water and gas, and recombination of these flows. The system uses gravity for level control. It may be installed parallel to a manifold. The liquid section comprises, next to a composition meter, a flow meter.
Succesful application of gravity control requires low pressure loss over the liquid meter (maximum allowable pressure loss equals 5 kPa). Installation parallel to a manifold demands a large flow range which the meter has to cover (first field test: 30-500 m³/day).
As a variable venturi can meet these requirements, it is chosen as a potentially suitable liquid flow meter.
Several concepts have been examined and a prototype has been built and tested. It consists of a drum containing several Venturis around which a box is built to prevent leakage. The Venturis (three for the prototype) have different throat diameters and can be rotated into position in the flow.
Test results show the feasibility of the design. A large flow range, without high differential pressures, can be realised. For the prototype approximately 22-650 m³/day (i.e. a turn-down of about 1:30), while differential pressures stay within 1-10 kPa. The concept however is suitable for even larger turn-downs (1:100 can be accommodated). For single phase flow pressure losses stay well below maximum allowable 5 kPa.
However, with gas entrained liquids pressure recovery may deteriorate sharply (down to 0%, although this has to be verified as adequate testing on this phenomena was not possible). Venturi performance under these circumstances has to be ascertained and a separate study is currently in progress. If pressure recovery is low indeed, the advantage of a venturi diminishes and other flowmeters should be considered. For instance, orifices, also within the drum and box concept, could provide a viable alternative.
Reports on Transport Engineering and Logistics (in Dutch)
