Авіаційно-космічна техніка та технологія (Aug 2020)
EFFECT OF THE CLEARANCE BETWEEN ROWS OF COAXIAL PROPFAN ON THRUST
Abstract
The thrust of a turboprop engine depends on many factors, one of which is hydraulic loss when flowing around the propeller blades. When using coaxial propellers, this factor plays an even greater role, since in this case the losses associated with the swirl sheet behind the first propeller were added. The aim of the work is to assess the influence of the axial clearance between the rows of the coaxial propeller on the thrust. The object of the study is a coaxial propeller. The axial clearance between the rows of the propeller ranged from 650 mm to 950 mm. Geometrically, the calculation model was a cylinder with a radius of 75 m and a height of 150 m. A coaxial propeller was located in the center of the cylinder. The investigated computational model is divided into four subregions: the external environment, the input guide vane, the first row of the propeller, the second row of the propeller. Separation of the calculation model into those listed below for the region allows us to evaluate the effect of the engine air intake on the propeller parameters and to ensure the correct modeling of flow around two rows of the propeller. In the first step of the study, a comparison was made of the results of numerical simulation with the results of an approved mathematical model for a version of a propeller with an axial clearance of 650 mm. The calculations were carried out with three models of turbulent viscosity: k-ω, SST, SST Gamma Theta Transitional. Based on the comparison, the SST turbulent viscosity model was selected for further research. The second research step included flow modeling for a modified coaxial propeller with an axial clearance between the propeller rows of 950 mm. According to the results of the study, it was found that the magnitude of the axial clearance between the rows of coaxial propeller affects the thrust. It is shown that when the clearance between the rows of the propeller increases from 650 mm to 950 mm, the thrust of the propeller increases by 17 %. This can be explained by a decrease in the level of unevenness and hydraulic losses behind the second row of the propeller. In the future, the obtained results of a numerical experiment require agreement with a field experiment.
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