Differential mass flowmeter

Claim 1

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

Claim 2

An apparatus for measuring the difference between the mass flow rate of a first fluid stream and the mass flow rate of a second fluid stream comprising: means defining a first flow channel through which said first fluid stream passes; means defining a second flow channel through which said second fluid stream passes; a first drum member mounted for rotation in said first flow channel; a second drum member mounted for rotation within said second flow channel; driving means associated with said first and second drum members for rotating said first and second drum members at identical speed and with a constant phase relationship; a first impeller means mounted for rotation in said first flow channel for imparting angular momentum to said first fluid stream, and first impeller means being resiliently coupled to said first drum member to allow said first impeller means to lag behind said first drum member by an amount proportional to the angular momentum imparted to said first fluid stream by said first impeller means; a second impeller means mounted for rotation in said second flow channel for imparting angular momentum to said second fluid stream, said second impeller means being resiliently coupled to said second drum member to allow said second impeller means to lag behind said second drum member by an amount proportional to the angular momentum imparted to said second fluid stream by said second impeller means; first impeller pick-off means associated with said first impeller means to produce a first impeller signal representative of the instantaneous angular position of said first impeller means; second impeller pick-off means associated with said second impeller means for producing a second impeller signal representative of the instantaneous angular position of said second impeller means; and first signal-processing means for receiving said first and second impeller signals and combining them to produce a signal representative of the difference in instantaneous angular position between said first and second impellers which signal is also representative of the difference in mass flow rate between said first and second fluid streams.

Claim 9

An apparatus for measuring the difference in mass flow rate between any pair of a plurality of fluid streams, including: a housing defining a plurality of fluid flow channels, each of which is associated with one of the said plurality of fluid streams; an impeller means mounted for rotation in each of said flow channels for imparting angular momentum to the fluid stream within an associated channel; a single driving means resiliently coupled to all of said impeller means to rotate each of said impeller means at identical speed, said resilient coupling allowing each said impeller means to lag behind said driving means by an amount proportional to the angular momentum imparted by said impeller to the fluid stream in its associated flow channel; impeller pick-off means associated with each impeller means for producing impeller signals representative of the instantaneous angular position of each said impeller means; signal-processing means for receiving said impeller signals and combining any two of them to produce a difference signal representative of the difference in instantaneous angular position between the impellers whose signals are combined, which signal is also representative of the difference in mass flow rates between the two fluid streams whose impeller signals are combined.