Экспериментальное исследование нового способа уменьшения волнового сопротивления профиля при трансзвуковых скоростях

A new method is proposed for wave drag reducing of a supercritical airfoil at transonic speeds, which is associated with the organization of a microwave section in a local supersonic zone on the upper surface. Simultaneously with optical studies, aerodynamic loads acting on a model were obtained. It is experimentally established that the proposed approach leads to the formation of a system of weak compression waves, to consecutive deceleration of the supersonic flow, to decrease of the Mach number in front of the shock wave, and, as a consequence, to weakening of its intensity and to reducing of the airfoil wave drag

Effect of Inner Nozzle Lip Thickness on Co-flow Jet Characteristics

This paper presents the experimental results of subsonic and underexpanded sonic jets delivered from a central nozzle surrounded by a co-flow. The role of central nozzle lip thickness on the co-flow jet characteristics has been studied. The jet-mixing enhancement is achieved in the case of jet from the thick-lip nozzle compared to that of thin-lip nozzle. The extent of supersonic zone for the thick-lip is much shorter than the thin-lip jet.

Aerodynamic and Performance Behavior of a Radial Turbine at Design and Off-Design Conditions

When a turbocharged engine which was designed to work at sea level works at high altitude area, its power will decrease because of the decrease of the air density. And the expansion ratio of the turbine will increase a lot because of the decrease of the out pressure, leading to a bad efficiency of the turbine. In order to recover the power of the turbocharged engine when it worked at the high altitude area, the efficiency of the turbine should be increased when it worked at high expansion ratio condition. This paper shows a numerical investigation of the flow fields in a radial inflow turbine at design and off design condition. The comparison of the flow characteristics between the design and off design conditions is researched. When the turbine work at a high expansion ratio, there will occur a supersonic zone at the leading edge on the suction side and a shock wave will occur at the trailing edge, causing a flow separation and making a lot of losses, leading the decrease of the turbine efficiency.

Experimental Analysis of Air Jets for Sorting Applications

Pulsed air jets are used in the industry to eject objects in sorting operation and understand the jet establishment and its spatial characteristics is important to optimize the application. This paper presents a first experimental analysis of jets issued from a high speed solenoid valve in terms of pressure, temperature, and velocity. Results will be first shown for steady state flows at different pressure conditions inducing subsonic or supersonic air jets and compared to the literature. For a subsonic jet, the results confirm the topography proposed in the literature. For the supersonic jets, a subsonic topography was identified after the supersonic zone. These supersonic jets have a constrained diameter which is appreciated in order to perform sorting with precision. Then, first unstationary experimental results will be presented and commented. This first measurement of the jet development is encouraging, since it was possible to identify the different delays linked to the propagation time from the valve outlet to the measurement point on opening and closing.

A Numerical and Experimental Study on the Effect of the Cone Angle of the Spindle in Murata Vortex Spinning Machine

To study the effect of the cone angle of the hollow spindle in the nozzle of Murata vortex spinning (MVS) on yarn properties, the k‐ε turbulence model is employed to simulate the airflow patterns inside the different nozzles with different spindle cone angles. A set of corresponding spinning experiments is designed to verify numerical predictions. The simulation results show that some factors, such as the counter-rotating vortex pair (CVP) over the spindle, high supersonic zone in the inlet of the swirling chamber, and the distribution of wall shear stress (WSS) along the outer wall of the spindle caused by variation of the cone angle of the spindle, are significantly related to fluid flow, and consequently to MVS yarn properties. A rational cone angle (Case 2) can form an axisymmetric CVP and high WSS, which can ensure sufficient twisting of the yarn and produce high quality yarn. The experimental results, which yarn properties spun using 100% cotton, 100% polyester, and polyester 70∕cotton 30 blends with different nozzles, are well consistent with the numerical study.