Development of a high efficiency in-line tube fan using CFD

An in-line tube fan with design flow rate 1 m³/s, static pressure 1030 Pa, rotation speed 3450 rpm, and specific speed 2.1 was investigated. Inverse design method was used to design deswirl vane while CFD to analyze its flow field. Results showed that although the efficiency of the axial straight flat plate is poor, it remained better than that of the vaneless type. The efficiency of deswirl vane was much higher than the previous two. However, when the casing-impeller ratio was lower than 1.25, completely recovering tangential velocity would result in large recirculation flow near outlet of deswirl vane. When the casing-impeller ratio increased to 1.33, the recirculation flow and pressure loss were obviously reduced. When the casing-impeller ratio increased to 1.46, the deswirl vane almost completely recovered tangential velocity, and pressure loss was further reduced. Static pressure and efficiency at operating point were 10% and 6% higher than the casing-impeller ratio 1.33.