Export Angle On The Law Of Influence Of The Centrifugal Pump Impeller Cutting Experiment

The work is one part of a project that was supported by the Scientific and technological research fund at Lanzhou University of Technology.Impeller trim is an important way to adjust hydraulic performance of centrifugal oil pumps with constant motor speed. Thus, the investigation into the pump performance variation with various impellers trimmed has a practical signification to maintain the pump operating in a high efficiency, to reduce its electricity consumption and to enrich its flow theory and performance features.This research group did some experiment researches in the affinity law of impeller trim and the influence of number of blades on the law etc for the original impeller of centrifugal oil pump of type 65Y60 in succession.It has been shown that there is a large choice interval for blade outlet angle when a centrifugal oil pump being designed. This will cause the blade outlet angle of the pump made by one manufactory would differ from that by another. Does the performance variation with impeller diameter trimmed still share the same affinity law for the pumps with different blade outlet angles? The present thesis will attempt to attack this research issue by experiments. The centrifugal oil pump of type 65Y60 with low specific speed, which have been applied extensively in oilfields and refineries in China, is selected the test model. The pump performance variations with impeller diameter trimmed have been studied experimentally under various viscosities of liquids for the impellers with outlet angles of respective 15 , 30 ,45 and 60. Based on the experimental data, the trim exponents of head and shaft power in shut-off points and exponents of flow rate, head, shaft power and efficiency in best efficiency points have been worked out. The discrepancy in both performance and trim exponent among the impellers with different outlet angles has been analyzed. Based on the results of the investigation, the following conclusion should be made:(1) When the impeller is cut in first time, the pump efficiency rises at best efficiency points. The larger the blade outlet angle is, the greater the efficiency rises. If the pump handles viscous oil, the efficiency rises greatly as the viscosity increases.(2) The trim exponents of head and shaft power of the impeller with different outlet angles approximately are equal to different constants respectively at shut-off points.(3) When handling viscous oil, the trim exponents of head in best efficiency points is close to that at shut-off points. However, the trim exponent variations of head of impellers with different outlet angles differ from each other.(4) When pumping viscous oil, the larger blade outlet angle will result into smaller trim exponents in a certain viscosity range.(5) There is a relationship between the trim exponents and impeller diameter ratio, namely the exponents vary with the ratio.