vane
1. A thin and more-or-less flat object intended to align itself with a stream or flow in a manner similar to that of the common weathercock, as: (a) a device that project ahead of an aircraft to sense gusts or other actions of the air so as to create impulses or signals that are transmitted to the control system to stabilize the aircraft; (b) a fixed or movable surface used to control or give stability to a rocket. See control vane.
2. A blade or paddle-like object, often fashioned like an airfoil and usually one of several, that rotates about an axis, either being moved by a flow or creating a flow itself, such as the blade of a turbine, of a fan, of a rotary pump or air compressor, etc. See impeller vane.
3. Any of certain stationary blades, plates, or the like that serve to guide or direct a flow, or to create a special kind of flow, as: (a) any of the blades in the nozzle ring of a gas-turbine engine; (b) any of the plates or slatlike objects that guide the flow in a wind tunnel; (c) a plate or fence projecting from a wing to prevent spanwise flow. See contravane. See airfoil, note. http://vesuvius.jsc.nasa.gov/er/seh/v.html#vane
My guess is that it is some sort of mixing propeller to produce an even temperature in the chamber – without more context it is difficult to tell. But whether it is a mixing propeller, flow-directing structure or flow-measuring device (i.e. a propeller connected to a small generator) will it not translate as 'pala'.