A reactor (12) and method for the conversion of hydrocarbons utilizes a reactor (12) having a unique feed assembly (56) that creates an inwardly spiraling fluid flow pattern of the feed gases to form a swirling gas mixture that passes through a conduit (46) with a constricted neck portion or nozzle (52). At least a portion of the swirling gas mixture forms a thin, annular mixed gas flow layer immediately adjacent to the conduit (46). A portion of the swirling gas mixture is combusted as the swirling gas mixture passes through the conduit (46) for conversion of hydrocarbons.