Оцінка характеристик закапотованого гвинтовентилятора ТРДД з надвисоким сту-пенем двоконтурності

In many respects, the efficiency and economy of the aircraft are determined by the parameters and characteristics of the power plant. The analysis of trends in the world engine building shows that an increase in the bypass ratio can significantly increase the efficiency of engines. One of the possible technical solutions to ensure the high performance of the perspective engines with an ultra-high bypass ratio is the use of a ducted propeller or propfan. This solution allows you to reduce acoustic radiation. In addition, the main advantage of the ducted propfans is a certain increase in thrust for the same consumed power. When flowing around a ducted propfan, a significant suction force arises on the nose of the profiled ring, the projection of which on the direction of movement provides a positive thrust of the ring. The presence of a duct also leads to a decrease in the final loss of the propeller, which, in turn, leads to an increase in the efficiency of the engine. Ducted and unducted propfans with the same blade row are investigated to assess the characteristics of a ducted propfan. The researches were carried out by the method of numerical experiment. The object of the research is a propfan with an inlet diameter of 2.924 m and the number of blades of 14 for a turbofan engine with a bypass ratio of m = 30. To research the propfan characteristics, a cruising mode of operation was selected in the range of revolutions n = 1500 ... 1650 rpm. with Mach numbers at the input from M = 0.54 to M = 0.8. In this work, the calculation did not take into account the resistance force of the duct. For a qualitative assessment of the flow in the propfan, visualization of the flow lines in the ducted and unducted propfan was obtained. The analysis of the research results showed that for all modes of operation the ducted propfan has a thrust force higher than the unducted propfan. The increase in thrust load reaches 71 ... 76 %. Visualization of the flow lines when flowing around a ducted and unducted propfan showed that the presence of a duct improves the internal aerodynamics of the propfan.

Numerical Study of the Hydrodynamic Characteristics Comparison between a Ducted Propeller and a Rim-Driven Thruster

The Rim-Driven Thruster (RDT) is an extraordinary innovation in marine propulsion applications. The structure of an RDT resembles a Ducted Propeller (DP), as both contain several propeller blades and a duct shroud. However, unlike the DP, there is no tip clearance in the RDT as the propeller is directly connected to the rim. Instead, a gap clearance exists in the RDT between the rim and the duct. The distinctive difference in structure between the DP and the RDT causes significant discrepancy in the performance and flow features. The present work compares the hydrodynamic performance of a DP and an RDT by means of Computational Fluid Dynamics (CFD). Reynolds-Averaged Navier–Stokes (RANS) equations are solved in combination with an SST k-ω turbulence model. Validation and verification of the CFD model is conducted to ensure the numerical accuracy. Steady-state simulations are carried out for a wide range of advance coefficients with the Moving Reference Frame (MRF) approach. The results show that the gap flow in the RDT plays an important role in affecting the performance. Compared to the DP, the RDT produces less thrust on the propeller and duct, and, because of the existence of the rim, the overall efficiency of the RDT is significantly lower than the one of the ducted propeller.

Design, simulation of AUV (VIAM-AUV1000) for research and rescue

Autonomous Underwater Vehicles have gained popularity for the last decades, especially a lot of AUVs were considered as the most suitable tool for the purpose of reducing risks of people in dangerous marine operations. This paper presents the preliminary results of the research on hardware design, the controller of an autonomous underwater vehicle model for the task of survey, search and rescue ... With a compact design, AUV can operate in limited spaces. Through a unique ducted propeller and rudder located at the aft, the AUV can perform horizontal motion. It can also control pitch angle and depth motion by an inside mass shifter mechanism (MSM) which changes the vehicle center of gravity. In addition, The AUV is integrated with powerful eletronic system, highprecision sensors helping it carries on missions from simple to complex. The use of Sliding Mode Control (SMC) to independently design the heading and depth controllers for AUV demonstrates the steady stability of the controllers with the nonlinear model, uncertainty parameters and disturbances. Finally, the simulation results show that the SMC controllers can control the AUV nonlinear model to track the desired steering angle and depth with high accuracy and stability.