Denysiuk O. Increasing efficiency of a gas-turbine engine propfan with an ultra-high bypass ratio

For the first time, a scientific methodology has been developed aimed at increasing efficiency of a ducted propfan of the engine with an ultra-high bypass ratio, including: - scientifically based recommendations for the tractive characteristics of unducted and ducted propfan for the gas turbine engine with ultra-high bypass ratio; - improved methodology for aerodynamic designing of ducted propfan for the gas turbine engine with ultra-high bypass ratio; - evaluation of including the propfan duct drag in calculation of the effective thrust of ducted propfan for the gas turbine engine with ultra-high bypass ratio. The theory of thermal engines was further developed with calculation of parameters and performance of ducted and unducted propfans for the gas turbine engines with ultra-high bypass ratio. The method of aerodynamic design of a ducted propfan of a turbofan with ultra-high bypass ratio has been improved. The methodology allows to design the blade row of a ducted propfan taking into account preset parameters of the gas generator, evaluate the number of blades and assess the results obtained. Scientifically based recommendations pertaining to the number of blades in unducted and ducted engine propfan were obtained. The number of blades in a ducted propfan increased from 8 to 14 allows increasing the propfan thrust up to 57 % at cruise and up to 48 % in ground mode. The obtained results of flow simulation in unducted and ducted propfan show that the duct effects the increase of a propfan thrust and the character of streamlining. With duct the thrust at cruise increases by 23.2 thru 69.2 %, and at takeoff by 28.8 thru 77.2 %. The efficiency of a ducted propfan increases with increase of blades number., The efficiency of a ducted propfan at cruise increases by 4 thru 7 % with number of blades increased from 8 to 14, and, respectively, by 3 to 4 % at takeoff. The evaluation was made of including the propfan duct drag in calculation of the effective thrust of a ducted propfan. The results of studies showed that in ground mode at studied rotational speed of 1500 rpm to 1650 rpm and Mach number range at inlet of 0.5 to 0.8, the drag ranges from 6.9 to 29.3 % of the ducted propfan thrust. In flight mode at altitude of H=11 km, the values of drag force and percentage are decreasing as compared with operation of a ducted propfan on ground. At studied rotational speed within 1500 to 1650 rpm and Mach number at inlet ranging within 0.55 to 0.8, the drag makes 6.3 to 15.3 % of thrust of a ducted propfan. Visualization of stream lines flowing about unducted and ducted propfan demonstrates qualitative nature of a change in streamlining. A specific feature is observed in unducted propfan streamlining, such as existence of vortexes at blades outlet on the periphery. Visualization of stream lines flowing about the ducted propfan has a similar flow pattern. On the periphery there are higher velocity zones, however, no vortex activity zones are observed. Practical significance of obtained results is confirmed by Reports of implementation of the results in work at SE Ivchenko-Progress and SE Antonov.