One of the basic requirements for existing and future aircraft engines is high specific power, low specific fuel consumption, and low noise level. The current work evaluates the thrust of a ducted coaxial propfan. A coaxial propfan was chosen as the object under study. The peripheral diameter of the first and second rows of the propfan reaches 4.5 m. The number of blades of the first row of the propfan is 8, the second – 6. The duct had a length of 3.214 m and a maximum profile thickness of 0.23 m. For this study, a model of a coaxial propeller fan was made for a numerical experiment. The model created for the study was a cylinder with a radius of 75 m and a height of 150 m. A model of an open coaxial fan and a ducted coaxial fan was created in this cylinder. The simulation of the flow in a ducted and open coaxial propfan was carried out for a flight altitude of H=7534 m at a rotational speed of the first and second rows of the propfan at 850 rpm. The input Mach number was 0.52. Based on the results of the study, a histogram for evaluating the thrust of the ducted and open coaxial propfan was constructed. The simulation of the flow in assessing the thrust of a ducted and open coaxial propfan was carried out under the same flight conditions. The results of the study showed that the presence of a duct gives a fairly large increase in thrust - the thrust of a coaxial propfan increases by 82 %. However, note that the calculations do not consider the drag that the duct will create. Evaluation of the drag of the ducted is the next task of the study. The resulting visualizations of the flow around an open and ducted coaxial propfan demonstrate qualitative and quantitative changes in the values of the parameters under study during flow. It can be seen that in the presence of a duct, the total pressure behind the propfan increases significantly. Increasing the thrust of a ducted coaxial propfan makes it possible to reduce the rotational speed of the propfan to provide thrust similar to that of an open propfan, which will improve the acoustic characteristics of the propfan. Also, the acoustic radiation can be reduced by placing sound-absorbing structures in the duct.

The efficiency of an aircraft engine is estimated by many parameters, one of which is the thrust force. Improving the efficiency of aircraft engines is an important task for engine building. However, questions remain regarding the effect of the number of blades on the change in the thrust of the ducted and unducted fans. In this work, the object of study is a propfan. 3 variants of the propfan with 8, 10, and 12 blades were investigated. The study was conducted by the method of numerical experiment. The aim of the work was to compile recommendations for choosing the number of blades in the ducted and unducted fans for motors with an ultra-high bypass ratio. That could make it possible to improve the efficiency of an aircraft engine with a propfan. Studies have shown that the number of blades in a propfan significantly affects the thrust force that it creates, as well as efficiency. With an increase in the blades of the ducted fan from 8 to 12, the thrust force increases to 38 %. With an increase in the blades of the propfan from 8 to 12, the thrust force increases to 36.9 %. An increase in the blades from 8 to 12 in the ducted fan leads to an increase in its performance, thereby improving efficiency by 2.4–5.7 %. When flowing around a propfan, it is possible to note the peculiarity that occurs when all three variants are streamlined – vortex traces of the blades in the peripheral parts. Visualization of current lines when flowing around an unducted fan with 8, 10, and 12 blades demonstrates a similar flow character. On the periphery, there are zones of higher speed but there are no zones with eddy formations. The resulting regularities of the influence of the number of blades on a change in the thrust of the ducted and unducted fans could improve the efficiency of the aviation power plant with an engine whose bypass ratio is ultra-high.

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.

The aerodynamic wakes behind the struts cause uneven flow at the compressor inlet. An irregularity at the compressor inlet of a turboshaft engine causes unstable operation of the compressor, which can deteriorate the engine economy and a decrease its efficiency. The current work evaluates the effect of injection of an additional mass of air into the inlet struts of a TV3-117 turboshaft engine on the velocity non-uniformity at the compressor inlet. The solution of the task was carried out by the method of mathematical modeling using the free version of the Ansys Workbench Student software environment. When solving the problem, several modules were involved: Geometry (creation of geometry), Mesh (generation of the computational mesh), CFX (selection of boundary and initial conditions, calculation and visualization of the calculation). The blade rim of the input racks of a TV3-117 turboshaft engine was chosen as the object of study in this work. Analysis of the results obtained shows that by using the injection of additional air mass, it is possible to reduce the unevenness of the speed at the compressor inlet. When injected with a mass flow rate of 2.2...2.8% of the main mass flow rate at inlet speeds of 100...160 m/s, the speed unevenness at the compressor inlet decreases from 10...12% to 3...4%. Thus, the velocity field in front of the compressor will be nearly uniform, which will positively affect its performance. An analysis of the visualizations of the velocity fields shows that when additional air mass is injected, the aerodynamic wake changes qualitatively and decreases significantly, the speed in the wake at a distance of 10 mm differs from the speed in the flow core by 3%, in contrast to the case without boundary layer control, where the speed in the wake it differs in speed in the core of the flow by 10...12%. To control the boundary layer in the blades of the input racks, it will not be necessary to supply additional air because air that is already supplied to heat the input racks can be used for this. The design of the inlet leg blade with control of the near-boundary layer will be quite complicated, but it is possible to implement the developed inlet leg blade design for controlling the boundary layer in the trailing edge using modern 3D printers.