Volcano v rocket stove

Hi All,

I have used a *volcanoe/ Kelly Kettle whilst camping and wondered if its funnel shape speeds up the heating process i.e. does the shape compress the gases making it burn hotter ? If so, can we use that shape in a rocket stove to make it more efficient to heat water for my house ?

* A volcanoe/ Kelly Kettle is basically a double-walled chimney with the water contained within the chimney walls. It is a based on rocket stove principles and heats water incredibly fast.

In my observations of my Kelly Kettle, the smoke occasionally ignites for a secondary burn. Which is similar to a rocket stove. But this happens at the upper lip of the chimney, where the extra heat probably can't heat the water very much. But I do think that the water jacket creates a positive feedback loop that helps the fire burn a bit hotter as the water heats up.

Venturi Effect must have some impact:

Where a gas or fluid passes through a pipe that narrows or widens, the velocity and pressure of the gas or fluid vary. As the pipe narrows, the gas flows more rapidly.