Abstract
A new shape of the tandem blade with an improved arrangement of profiles, in relation to the known propellers, in which the profiles are located similar to those in the tandem wing of an airplane is developed. A new arrangement of profiles along the height of the blade is proposed. The basis for the design was the location of the profiles according to the type of tandem blade rows of compressors and fans. Such an approach made it possible to eliminate the aerodynamic shadowing of the blades and increase the aerodynamic loading. To join the blades in the final part, a spiral tip connector is used, which allowed to significantly reduce the secondary end losses by preventing the formation of the tip vortex. To study the characteristics of tandem propellers and the structure of gas-dynamic flows around them, a computational model of the propeller in a periodic formulation was developed, which significantly reduced the calculation time. The simulation was carried out in the ANSYS CFX software package, which implements an algorithm for solving non-stationary Reynolds averaged Navier-Stokes equations closed by the SST turbulence model. As a result of the simulation, the characteristics of the tandem propeller were obtained, which confirmed the correctness of the chosen approach for the design of the tandem blade. The efficiency of the developed propeller reaches 75 % in the design mode, which is a very good indicator for small propellers operating at low Reynolds numbers. For comparison, the efficiency of classic propellers with similar geometric characteristics is in the range of 50–60 %. When using the tandem propeller with joined blades as a pusher propulsion, a decrease in its thrust by 3–4 % was observed, which is due to the formation of a vacuum zone in the hub part and in the spinner area
Highlights
The propeller, as a thruster, has been known for a very long time and has been the only possible mover in aviation for many years
Applied mechanics have no competitors in the application on wing-in-ground effect crafts and air-cushion ships, where it is necessary that the propeller throw a large mass of air at a low speed, which is impossible to achieve with jet engines
A geometric model of the tandem propeller is developed taking into account the features of the flow around the first and second rows of blade profiles, which differs in the new location of the profiles of the first and second rows of the blade along its height
Summary
The propeller, as a thruster, has been known for a very long time and has been the only possible mover in aviation for many years. It should be noted that tandem propellers allow a comprehensive approach to solving the problem of efficiency and reducing weight and size characteristics, along with the known advantages, theoretical methods for their design are practically absent, which creates significant difficulties in the design and use of such propellers. This is primarily due to the practical lack of research results on tandem propellers with joined blades, and the results of existing research are only partial and do not provide a complete picture of the aerodynamic characteristics and flow characteristics of tandem propellers. Studies aimed at determining the aerodynamic characteristics and flow characteristics of tandem propellers with joined blades are relevant and timely, since their results will subsequently determine the factors affecting their characteristics and develop methods for designing such propellers
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