Dilution device

An exhaust sampling system, comprising:

• a first flow sensor fluidly connected to a compressed air source and configured to sense a characteristic of a dilute flow;
• a flow control valve fluidly connected to the first flow sensor and configured to controllably direct the dilute flow to a dilute flow inlet port of a dilution device;
• a second flow sensor fluidly connected to an outlet port of the dilution device and configured to sense a characteristic of a combined flow;
• and
• a controller configured to control a mass flow rate of a flow of engine exhaust gas extracted by an extraction component of the dilution device based on a difference between the sensed characteristic of the dilute flow and the sensed characteristic of the combined flow,
• the dilution device including:
• a first porous conduit having an internal flow passage, the first porous conduit having a plurality of pores that communicate between a first chamber located externally of the first porous conduit and the internal flow passage, the first chamber having an outer wall having a plurality of pores that communicate between a second chamber located externally of the outer wall, the second chamber being in communication with the dilute flow inlet port, the first porous conduit including a port at a first end of the first porous conduit in communication with the second chamber.

A method of controlling fluid flow through a fluid sampling system connected to a power source, comprising:

• extracting a portion of fluid from the power source;
• directing the portion of fluid into a chamber of a dilution device;
• directing dilute gas into the chamber through a porous wall surrounding the chamber;
• directing dilute gas through a porous conduit at central region of the chamber and into the chamber;
• and
• directing a combined flow of the portion of fluid and the dilute gas out of the dilution device through an outlet port in communication with the chamber.