Isokinetic diluter for particle measuring instrument

A method of determining the size distribution of particles in a flowing fluid sample containing particles suspended therein, comprising dividing the flowing fluid sample into a first and second sub-stream, filtering the particles from said first sub-stream to form said first sub-stream into a filtered steam while leaving particles suspended in said second sub-stream in the same size distribution as in said fluid sample, and then mixing said filtered stream and said second sub-stream together into a combined stream and measuring the size distribution of the particles in said combined stream.

An apparatus for dilution of fluids entraining particles comprising:

• a chamber having an entrance port and an exit port and defining a flow path to pass fluid from said entrance port to said exit port, the entrance port defining a direction of flow in said entrance port for fluid passing through said chamber from said entrance port to said exit port, a permeable filter medium in said chamber separating said chamber into a proximal region and a distal region, said filter medium being arranged to trap particles from fluid passing from said proximal region to said distal region through said filter medium, said entrance port located in said proximal region and said exit port located in said distal region and a tube having a proximal end and a distal end, said tube connecting said proximal region to said distal region, said tube having an entrance opening in said proximal end facing the direction of flow in said entrance port and being constructed and arranged so that the fluid flowing into said entrance port is isokinetically divided into flows around the proximal end of said tube and into the entrance opening of said tube.

A particle measuring system comprising an apparatus for dilution of fluids, an instrument for measuring the sizes of particles entrained in a stream and means to draw a sample gas stream through said apparatus for dilution and then through said instrument, said apparatus comprising a chamber having an entrance port and an exit port and defining a flow path to pass fluid from said entrance port to said exit port, the entrance port defining a direction of flow in said entrance port for fluid passing through said chamber from said entrance port to said exit port, a permeable filter medium in said chamber separating said chamber into a proximal region and a distal region, said filter medium being arranged to trap particles from fluid passing from said proximal region to said distal region through said filter medium, said entrance port located in said proximal region and said exit port located in said distal region and a tube having a proximal end and a distal end, said tube connecting said proximal region to said distal region, said tube having an entrance opening in said proximal end facing the direction of flow in said entrance port and being constructed and arranged so that the fluid flowing into said entrance port is divided into flows around the proximal end of said tube and into the entrance opening of said tube.

A method of diluting a flowing fluid sample containing particles suspended therein, comprising dividing the flowing fluid sample into a first and second sub-stream, filtering the particles from said first sub-stream to form said first sub-stream into a filtered stream while leaving particles suspended in said second sub-stream in the same size distribution as in said fluid sample, and then mixing said filtered stream and said second sub-stream together, the pressure drop through the length of travel of said first stream during said filtering being substantially equal to the pressure drop through the length of said second sub-stream.

A method of diluting a flowing fluid sample containing particles suspended therein, comprising dividing the flowing fluid sample into a first and second sub-stream, filtering the particles from said first sub-stream to form said first sub-stream into a filtered stream while leaving particles suspended in said second sub-stream in the same size distribution as in said fluid sample, and then mixing said first filtered stream and said second sub-stream together, the flow in said second sub-stream being maintained turbulent throughout said second sub-stream.

An apparatus for dilution of fluids entraining particles comprising:

• a chamber having an entrance port and an exit port and defining a flow path to pass fluid from said entrance port to said exit port, the entrance port defining a direction of flow in said entrance port for fluid passing through said chamber from said entrance port to said exit port, a permeable filter medium in said chamber separating said chamber into a proximal region and a distal region, said filter medium being arranged to trap particles from fluid passing from said proximal region to said distal region through said filter medium, said entrance port located in said proximal region and said exit port located in said distal region and a tube having a proximal end and a distal end, said tube connecting said proximal region to said distal region, said tube having an entrance opening in said proximal end radially centered in said entrance port and facing the direction of flow in said entrance port and being constructed and arranged so that the fluid flowing into said entrance port is divided into flows around the proximal end of said tube and into the entrance opening of said tube.