Valve with enhanced rangeability and logarithmic flow characteristic

A control valve comprising (a) a valve body having a slide chamber therein and an inlet passage and an outlet passage cooperating to partially define a flow passageway transversely intersecting the slide chamber;

• (b) a plug member mounted for movement within the slide chamber and having an elongated flow orifice extending transversely therethrough, the plug member and its flow orifice being each dimensioned and configured to seal the flow passageway when the flow orifice is out of registration with the inlet passage and to complete the flow passageway by connecting the inlet and outlet passages in flow communication when the flow orifice is registered therewith;
• and (c) positioning means operatively connected to the plug member to position the plug member at selected locations within the slide chamber to selectively adjust registration of the flow orifice with the inlet and outlet passages, the flow orifice and flow passageway being respectively dimensioned and configured to provide a flow characteristic such that a plot of percentage lift on the ordinate versus percentage flow as the abscissa on log--log coordinates defines a straight line of positive slope, and wherein the inlet and outlet passages are of circular cross section and at least a segment of the flow orifice has a tapered slot portion with a cross-sectional flow area less than that of the flow passageway, the tapered slot portion being narrower than the diameter of the flow passageway over at least a majority of its length, and a base portion with a cross-sectional flow area which is at least as wide as the cross-sectional flow area of the flow passageway and which is dimensioned and configured so that when the base portion is fully registered with the flow passageway, the valve is fully open to flow therethrough and when the tapered slot portion or part thereof os registered with the flow passageway, the valve is partially open for flow therethrough.

A control valve comprising:

• a valve body having therein a slide chamber and an inlet passage and an outlet passage at respective opposite sides of the chamber, the inlet and outlet passages cooperating to partially define a flow passageway transversely intersecting the slide chamber;
• a plug member mounted for movement within the slide chamber and having a flow orifice extending transversely therethrough, the plug member and its flow orifice being each dimensioned and configured to seal the flow passageway when the flow orifice is out of registration with the flow passageway and to complete the flow passageway by connecting the inlet and outlet passage in flow communication when the flow orifice is registered therewith, at least a segment of the flow orifice being dimensioned and configured to have tapered slot portion with a cross-sectional flow area less than that of the flow passageway, the tapered slot portion (a) having in flow cross section the shape of an isosceles triangle, the legs of which subtend at their apex ends an angle of from about 45 to 90 degrees, and (b) being narrower than the diameter of the flow passageway over at least a majority of its length;
• and a base portion with a cross-sectional flow area at least as wide as the cross-sectional flow area of the flow passageway, and dimensioned and configured so that when the base portion is fully registered with the flow passageway, the valve is fully open to flow therethrough and when the tapered slot portion or part thereof is registered with the flow passageway, the valve is partially open for flow therethrough ;
• and
• positioning means operatively connected to the plug member to position the plug member at selected incremental locations within the slide chamber to selectively adjust registration of the flow orifice with the inlet and outlet passages at fully open, fully closed and a plurality of intermediate throttling positions.