What name is given to the device on a steam locomotive that discharges exhaust steam from the cylinders into the smokebox?

The blastpipe is part of the exhaust system of a steam locomotive that discharges exhaust steam from the cylinders into the smokebox beneath the chimney in order to increase the draught through the fire.

The primacy of discovery of the effect of directing the exhaust steam up the chimney as a means of providing draft through the fire is the matter of some controversy, Ahrons (1927) devoting significant attention to this matter. The exhaust from the cylinders on the first steam locomotive (built by Richard Trevithick) was directed up the chimney, and he noted its effect on increasing the draft through the fire at the time.

At Wylam, Timothy Hackworth also employed a blastpipe on his earliest locomotives, but it is not clear whether this was an independent discovery or a copy of Trevithick's design. Shortly after Hackworth, George Stephenson also employed the same method, and again it is not clear whether that was an independent discovery or a copy of one of the other engineers.