Method and apparatus for mixing gases

An apparatus for mixing a first and a second stream of gas, comprising:

• a first plurality of passages configured to direct the first stream of gas, wherein the first stream of gas is one of a stream of dilution air and a stream of exhaust gas from an engine;
• and
• a mixing chamber having first and second ends, the mixing chamber being flow coupled to the first plurality of passages and configured to receive the second stream of gas at the first end, the mixing chamber having an exit port at the second end, the second stream of gas is the other of the stream of dilution air and the stream of exhaust gas from an engine,
• the method further including at least one of the following characteristic factors:
• 1) wherein the first plurality of passages and the second stream passage attach to the mixing chamber in a manner that the first and second streams of gas are unobstructed by structure as they enter the mixing chamber;
• 2) wherein the mixing chamber has an absence of structure extending into the mixing chamber;
• 3) wherein the first plurality of passages and the second stream passage are configured to introduce the first and second streams of gas into the mixing chamber with a substantially well-developed flow;
• and
• 4) wherein at least one of the first plurality of passages and the second stream passage is configured to introduce at least one of the first and second streams of gas, as an exhaust gas, into the mixing chamber from more than one entrance port.

A mixing chamber for mixing a first stream of gas with a second stream of gas, comprising:

• an internal volume defined by a first end, a second end, and walls extending between the first and second ends, the second end having a gradually converging portion, with an absence of structure extending from the first end, from the second end, and from the walls into the internal volume;
• a first inlet opening configured to receive the first stream of gas into the mixing chamber, the first inlet opening located at the first end;
• a plurality of second inlet openings configured to receive the second stream of gas into the mixing chamber, the plurality of second inlet openings symmetrically positioned with respect to the first inlet opening;
• and
• an exit opening configured to discharge a combined stream of gas formed from the first and second streams of gas from the mixing chamber, the exit opening located downstream of the gradually converging portion wherein the first inlet opening and the plurality of second inlet openings are situated in a manner that the first and second streams of gas are unobstructed by structure extending into the mixing chamber.

A method of mixing a first stream of gas with a second stream of gas, comprising:

• introducing a first stream of gas into a mixing chamber via a plurality of first stream passages flow coupled to the mixing chamber;
• directing a second stream of gas into the mixing chamber via at least one second stream passage flow coupled to a first end of the mixing chamber;
• forming a combined stream from the first and second streams;
• discharging the combined stream from the mixing chamber through a mixing chamber exit port;
• providing walls of the mixing chamber with an absence of structure extending into the chamber;
• and
• introducing at least one of the first and second streams of gas into the mixing chamber as an entire exhaust gas flow.

A method of mixing an exhaust gas with a dilution gas for an emissions sampling system, comprising:

• directing the flow of an exhaust gas from an engine through an exhaust gas passage;
• directing the flow of a dilution gas through a dilution gas passage;
• receiving the dilution gas from the dilution gas passage at one end of a mixing chamber, the mixing chamber being flow coupled to the dilution gas passage;
• receiving the exhaust gas into the mixing chamber from the exhaust gas passage;
• developing a substantially well-developed flow stream of the dilution gas upstream of the exhaust gas passage;
• sampling the combined stream for compliance with emission standards;
• and
• discharging a combined stream of the exhaust gas and the dilution gas from the mixing chamber.

An emissions sampling system for mixing an exhaust gas with a dilution gas, comprising:

• an exhaust gas passage configured to direct a flow of the exhaust gas from an engine;
• a dilution gas passage configured to direct a flow of the dilution gas;
• a mixing chamber flow coupled to the dilution gas passage and configured to receive the dilution gas from the dilution gas passage at one end, the mixing chamber also being configured to receive the exhaust gas from the exhaust gas passage;
• and
• a sampling device in the mixing chamber to sample the gas in the mixing chamber,
• wherein the dilution gas passage is configured to create a substantially well-developed flow stream of the dilution gas upstream of the exhaust gas passage,
• wherein the mixing chamber includes an end configured to discharge a combined stream of the exhaust gas and the dilution gas from the mixing chamber.