| 摘要 |
Catalyser, with a central honeycomb catalyst body, has a diffusor section between the inlet pipe and the mixing region in front of the catalyst which can be fitted with a flow guiding body. The flow quiding body ensures an even flow to the surface of the catalyst, and ocmprises channels of gradually increasing cross-section in the direction of flow of the gases. Such flow guiding bodies can be constructed from various arrangements of corrugated and flat metal sheets or from pre-constructed parts. A narrow opening angle of the channels of the flow quiding body (less than pi/17,pref. less than pi/24) will allow for even, streamline flow and minimal throttling of the gases. A wider angle will produce turbulence. Turbulence may be useful, partic. at the end of a channel, to provide improved contact with the walls of the channels of the flow quiding body when these are coated with a catalytic susbtance themselves. This is useful for cold starts, since this coating will become effective sooner than the main catalyst body and aid the start-up of the latter with the heat produced. The mixing region allows turbulence to develop in the gas flow before it enters the catalytic body, thereby increasing the effectiveness of the catalyser. The converging section can be fitted with a flow guiding body. |
