In a tube-nested combustor of a compact water-tube boiler, water tubes are placed closely to the burner and thus conventional empty furnace is, in principle, removed. In this type of boiler the convective heat transfer becomes a dominant design factor owing to the existence of tube banks in a burning zone and resulting agitation of flow. The flow pattern in a tube nest closely to the burner jet is substantially different from that in a uniform flow. Then, a cold model test using full-scale simulated tube-nested combustor has been conducted to understand the fundamental characteristics of flow pattern and structure of re-circulations flow at the burner exit. A stable and symmetric re-circulation flow at the burner exit is observed in a suitable tube arrangement, and the three-dimensional structure of this re-circulation is investigated.

View full abstract