Abstract
In the present study, steady air injection upstream of the tip blade leading edge was studied. To reveal the mechanism, steady numerical simulations were performed on a transonic axial compressor, NASA rotor 37. The injection angle α is 20° and three injector axial position were studied, respectively 9, 18 and 27% upstream of the axial chord length at blade tip (ca). For each position a different injection mass flow rate and different injection yaw angles were simulated. The results show at design speed (n =17188 r/min), with injector position at 9% ca, injection mass flow rate of 2% and injection yaw angle between -20° and -30°, the mass flow rate at stall can decrease for approximately 3%, but others compressor parameters were affected such as the total pressure ratio. With injector positioned at 27% ca, the decrease in the mass flow rate at stall is less obvious, but the effect on the compressor pressure ratio is benefic.
Highlights
All current research on compressors, focus exclusively on the best way to eliminate instabilities, such as surge or stall, which affect the efficient functioning of the system and cause various losses in yield and rate of pressure
Recent research results (Lin et al, 2008; Vo et al, 2008) suggested the Tip Leakage Flow (TLF) and its interaction with the incoming main flow to be responsible for spike-type stall precursor and rotating stall inception
Some tip clearance flow originating near the casing travels over to the tip gap of the adjacent blade, resulting in so-called double leakage flow (Smith, 1993)
Summary
All current research on compressors, focus exclusively on the best way to eliminate instabilities, such as surge or stall, which affect the efficient functioning of the system and cause various losses in yield and rate of pressure. Flow through the tip gap interacts with the incoming passage flow near the suction side of the blade as it leaves the blade tip section, forming the tip clearance vortex. Some tip clearance flow originating near the casing travels over to the tip gap of the adjacent blade, resulting in so-called double leakage flow (Smith, 1993). The pressure difference across the blade tip section increases and the interaction between the tip clearance flow and the passage flow becomes stronger. This causes more mixing losses and an increase in aerodynamic blockage near the casing.
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