of the passage 23 of the valve is in this embodiment precisely defined in order to get a sonic flow of the gaseous fluid through the valve this means that the flowrate will be independent of the pressure on the downstream side of the valve which is very important in an application as injector valve as this pressure changes considerably during the engine working cycle at the same time the opening between the seat 24 and the disk in the fully open position of the valve is defined so that it is much bigger than the area of the hole 23 which will allow for the sonic flow in the hole 23 thus the flow of gaseous fluid only depends on the pressure of the gaseous fluid on the inlet to the valve 10 in a preferred embodiment the disk formed member 17 is provided with grooves 25 arranged radially on its lower surface as shown in fig2 these grooves have an inclined section which is causing a rotation of the disk 17 when the gaseous fluid circulate from the inlet conduit 26 through the valve towards the outlet conduit 36 the stepwise rotation of the disk 17 allows for a uniform wear of the seat 24 the disk 17 in the area where it touches the seat 24 in the closed position the guiding member 34 on the disk 17 and the slide bearing 14 the rotation of the disk could also.