When creating a modern aircraft, the principle of optimal integration of the power plant and the aircraft is used to ensure the maximum target function, determined by its functional purpose. The specific fuel consumption and specific thrust of the power plant depend significantly on the loss of the total air pressure in the inlet device, which is characterized by the total recovery factor. The change in pressure along the diameter of the propfan affects the efficiency of the inlet of the power plant. When using the inlet ring device, its efficiency decreases, due to low pressure in the area of the root part of the propfan blades. The use of a bucket inlet allows air to be supplied to the channel from the area located near the middle part of the blade height and this is the main factor influencing the reduction of pressure losses in the air supply channel. When using a bucket inlet, curvature and constriction are important factors influencing the effectiveness of S-channels. The influence of the curvature of the S-shaped channel on the total pressure recovery coefficient at a constant value of its narrowing is studied in this work. The study S-shaped channel in its geometric parameters is equivalent to the channel of the annular inlet device of a power plant with a turbofan engine. The total pressure recovery coefficient of an S-shaped channel is calculated from the flow parameters in the sections of the S-shaped channel by solving the Navier-Stokes equations using the Florian Menter two-layer turbulence model (SST Transitional No. 4 Gamma Theta) and the combined finite element model at the entrance to the channel and in the channel itself - hexahedral, at the exit tetrahedral. An analysis of the dependence of the total pressure recovery coefficient of the S-shaped channel on the M number and the channel curvature shows that, up to a curvature of 0.002, the total pressure recovery coefficient is not significantly affected. A further increase in the channel curvature has a significant effect on the change in the total pressure recovery coefficient, which is associated with flow separation and losses from the vortex formation.

The increase in losses in the inlet device leads to an increase in specific fuel consumption. When integrating the inlet device and the propeller or propfan, it is necessary to take into consideration their interaction to ensure the maximum efficiency of the power plant. The object of this study is a coaxial propfan with the channel of the inlet device. The results reported here are of practical value: a methodology for designing a bucket S-shaped channel of the inlet device of a power plant with a turboprop engine has been developed. The dependence of the coefficient of preservation of the total pressure of the inlet device on the height and speed of flight was obtained, which makes it possible to take into consideration the influence of the propfan of a turboprop engine. A comparison of the characteristics of the ring-type and bucket S-shaped channel of the inlet device of the power plant with the turboprop engine was carried out. Specifically, it was found that the change in flight conditions has a less significant effect on the change in the coefficient of preservation of the total pressureof the ring-typeinlet device than the bucket one. A comparative assessment of the obtained results of mathematical modeling of the flow in the bucket S-shaped channel of the inlet device, taking into account the influence of the propfan, with the results of flight tests of the ring-type inlet device of the prototype is given. The comparative evaluation shows that the use of a bucket inlet device, instead of a ring-type inlet device, makes it possible to increase the full pressure recovery factor by 5–7 %. Thus, there is reason to argue that replacing the ring-type with a bucket inlet device will minimize hydraulic losses at the inlet to the engine and reduce the uneven flow at the inlet. That, in turn, will improve engine efficiency.