bypass ratio
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The possibility of extracting large amounts of electrical power from turbofan engines is becoming increasingly desirable from an aircraft perspective. The power consumption of a future fighter aircraft is expected to be much higher than today’s fighter aircraft. Previous work in this area has concentrated on the study of power extraction for high bypass ratio engines. This motivates a thorough investigation of the potential and limitations with regards to performance of a low bypass ratio mixed flow turbofan engine. A low bypass ratio mixed flow turbofan engine was modeled, and key parts of a fighter mission were simulated. The investigation shows how power extraction from the high-pressure turbine affects performance of a military engine in different parts of a mission within the flight envelope. An important conclusion from the analysis is that large amounts of power can be extracted from the turbofan engine at high power settings without causing too much penalty on thrust and specific fuel consumption, if specific operating conditions are fulfilled. If the engine is operating (i) at, or near its maximum overall pressure ratio but (ii) further away from its maximum turbine inlet temperature limit, the detrimental effect of power extraction on engine thrust and thrust specific fuel consumption will be limited. On the other hand, if the engine is already operating at its maximum turbine inlet temperature, power extraction from the high-pressure shaft will result in a considerable thrust reduction. The results presented will support the analysis and interpretation of fighter mission optimization and cycle design for future fighter engines aimed for large power extraction. The results are also important with regards to aircraft design, or more specifically, in deciding on the best energy source for power consumers of the aircraft.

Blended wing body is a fixed wing aircraft which are smoothly blended together with no clear dividing line and no distinct wings also be given a wide Aerofoil shaped body. The future transportation is of aircrafts will incline towards the aerodynamically efficient and capable of carrying large number of passengers over long range and environmental benefits is the main paradigm in the design of aircraft BWB has a high lift to drag ratio which increases the CL max and velocity of the airplane with high load factor and high economy compared with traditional aircraft. Evacuation pressure or the cabin pressurization is the major issues in most of the designs with the minimum aerodynamic lift coefficient and drag coefficient. On the other side of the trend is towards the increasing cruise speed. High speed flow is connected with overcoming of intensive drag rise accruing due to existence of intensive shock, closing local area of supersonic flow. Increase of flight Mach number is possible only by using flow control methods and through affecting the shock increases of aspect ratio leads to increase of lift coefficient corresponding to maximal lift to drag. High bypass ratio engines have smaller fuel consumption and lower noise level but have negative effect on flow around airframe including take-off and landing phases. The necessity of solving problem of intensive aerodynamic heating of surface element of flight vehicles and by ensuring of their stability and controllability and also by need of implementing of high-volume tanks for hydrogen fuel and super high bypass ratio engines.

A variable area nozzle integrated into the design of a high-bypass-ratio turbofan engine effectively saves up to 10% in aircraft fuel consumption. Additionally, noise emissions can be lowered at airports during take-off and landing by having better control of the nozzle diameter. Shape memory capabilities of Nitinol alloys could be availed in the form of actuators in the construction of such a nozzle. However, these Nitinol actuators must be joined to Ti-6Al-4V, a prominent alloy making up most of the rest of the nozzle. Because of the huge differences in the physical and metallurgical properties of these alloys, fusion welding is not as effective as solid-state welding. In the current study, a linear friction welding process was adopted to join Ti-6Al-4V to Nitinol successfully. The effect of friction welding on the evolution of weld macro and microstructures; hardness and tensile properties were studied and discussed. The macrostructure of Ti-6Al-4V and Nitinol’s dissimilar joint revealed flash formation mainly on the Ti-6Al-4V side due to its reduced flow strength at high temperatures. Optical microstructures revealed fine grains in Ti-6Al-4V immediately adjacent to the interface due to dynamic recrystallisation and strain hardening effects. In contrast, Nitinol remained mostly unaffected. An intermetallic compound (Ti2Ni) was seen to have formed at the interface due to the extreme rubbing action, and these adversely influenced the tensile strength and elongation values of the joints.

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.

Modern trends in the global aircraft industry are prompting aircraft engine engineers to create and develop various methods to improve the aerodynamic characteristics of turbomachines. The urgent need to improve the efficiency of new generation engines leads to a rapid increase in the bypass ratio of engines, which requires the development of fans with large diametrical dimensions and high aerodynamic perfection. Boundary layer control in turbomachines using tandem blade rows is one of the most promising ways to improve the aerodynamic characteristics of aircraft engine fans with a high bypass ratio. The work aims to evaluate the aerodynamic characteristics of a fan with a tandem impeller for a turbofan engine. Two fan impellers were investigated: a single-row and an equivalent tandem-row (the equivalence was ensured by the equality of the structural angles of the flow inlet and outlet and the equality of the chord of the profiles). The blade row consisted of 33 blades, the tip diameter at the inlet to the impeller was 2.37 m, the hub diameter was 0.652 m. The flow was simulated in the range of axial velocity at the inlet from 80 to 200 m/s at a relative rotor speed of 0.65, 0.85, and 0.9. For the investigated tandem fan impeller, the chord of the first row was 60% of the total chord of the profile, the length of the slotted channel was 10% of the total chord. The flow was simulated using a numerical experiment. When closing the system of Navier-Stokes equations, Menter's SST turbulence model was used. The computational grid is unstructured, with an adaptation of the boundary layer. The work shows that the use of a tandem impeller will improve the aerodynamic characteristics of the fan. As a result of the study, it was found that the pressure ratio in a fan with tandem impeller increases from 0.32 to 20% for an operating mode at a relative rotor speed of n=0.65, n=0.85, and n=0.9 in the range of values of the gas-dynamic flow rate function q (λ)=0.4...1. The greatest growth is observed on the left branches of the pressure lines. The obtained data on the efficiency of a fan with a tandem impeller showed that in the range of values of the gas-dynamic flow rate function q(λ)=0.4...0.6 and q(λ)=0.76...0.98 a tandem impeller is higher than the efficiency of a fan with a single-row impeller, for values of the gas-dynamic flow function q(λ)=0.64...0.76 - the efficiency of a fan with a tandem impeller is 4% less than the efficiency of a fan with a single-row impeller.