Search

The present study reports the numerical investigation of the compressor cascade. To minimize the separation phenomenon in the compressor cascade, a passive flow control device i.e. Micro Vortex Generator (MVG) is utilized. MVG is a very simple and lightweight attachment mounted infront of the leading edge of the cascade blade. Due to being passive in nature, it neither consumes power nor requires any external device to actuate. The numerical simulations were carried out on a highly loaded compressor cascade at an angle of incidence of −1° under subsonic conditions at Mach number 0.2. The profile of the compressor cascade blade was double circular arc (DCA), unsymmetrical and cambered at 40°. Two different types of micro vortex generators were mounted infront of the leading edge in the compressor cascade to control the secondary flows since secondary flows were responsible for various losses in cascade. To analyze the flow under incompressoible state of air (M = 0.2), Star CCM + software has been used. To simulate the flow under turbulent condition, k-ω SST turbulence model was used. A velocity profile of 25 mm boundary layer thickness was extracted and used as an input in the compressor cascade. Mounting of MVG on compressor cascade enhanced drag but also increased lift. Total pressure loss coefficient (TPLC) was calculated to compare the losses. The aerodynamic efficiency in terms of coefficient of lift and coefficient of drag has been used to study the effect of MVG over cascade. It is found that there is reduction in total pressure loss coefficient (TPLC) for trapezoidal and curved trapezoidal types of MVGs and the decrease in percentage are 2.17 and 8.86%, respectively. Alos, aerodynamic efficiency is increased by mounting trapezoidal and curved trapezoidal types of MVG and the increase in percentages are 2.03 and 3.10%, respectively. [ABSTRACT FROM AUTHOR]

This paper reports the numerical investigations to analyze the effect of the application of Gurney Flaps on various configurations in a Low-Pressure Turbine (LPT) cascade in mitigating the laminar flow separation during low Reynolds number operations. T106 LPT blade of chord 60 mm has been selected for the present study. Gurney Flaps of flat type and quarter round type of a particular height of the chord length are selected. Flaps are provided near the blades' trailing edges for numerical analysis. The numerical computations are performed using STARCCM+ software, and the K-ω SST turbulence Model is used for turbulence closure. The studies are performed at various Reynolds numbers ranging from 37,500 to 138,750 to understand the application of various configurations of Gurney Flap vis a vis turbine blade without Gurney Flap. Performance parameters such as lift coefficient, drag coefficient, aerodynamic efficiency, and static pressure distributions over the blade surface are used to analyse the alterations in the performance of aerodynamic characteristics of the LPT Blade. All the Gurney Flap configurations improved the overall blade aerodynamics. Among these configurations, the flat Gurney Flap configuration is found to be superior as it improves the aerodynamic efficiency of the blade. [ABSTRACT FROM AUTHOR]

This study evaluates the ability of five micro vortex generator (MVG) geometries in attenuating the flow separation induced by an axisymmetric compression corner. Experimental and computational investigations were carried out at Mach 2 on a cone–cylinder–flare model, with a flow deflection angle of 24° at the cylinder/flare juncture. The MVG shapes considered were baseline ramp, trapezoidal ramp, split ramp, thick vanes and ramped vanes. A circumferential array of these MVGs having a device height (h) of 1.4 mm and an inter-device spacing of 10.5 mm (7.5 h) was introduced 50 mm upstream of the compression corner. Streamwise counter-rotating vortex pairs that originated from these devices created alternate bands of upwash and downwash regions in the incoming boundary layer, which resulted in suitable three-dimensional alterations of the separation region's size. Furthermore, surface streamline visualizations showed that the vortices induced profound topological transformations in the separated flow structure. In the absence of MVGs, spectral analysis of the pressure signal obtained from the separation shock's intermittent region revealed a relatively broadband dominant frequency range of 0.55 kHz–0.9 kHz. The MVGs did not cause any significant change in the dominant frequency, but made the bandwidth slightly narrower. Among the different MVG designs that were studied, the ramped vanes (RV) induced the most momentum augmentation in the near wall region and thereby caused the maximum downstream shift in the separation shock's position. [ABSTRACT FROM AUTHOR]

Two dimensional computations were conducted to investigate the performance of NACA 0010 cascades with Gurney Flaps. The cascades with three different stagger angles (βB) viz. 45°, 90° and 135° were studied for the aerodynamic performance characteristics of the blades with and without Gurney Flaps and the results were compared. The Gurney Flap's length is 2 % of the chord length and has a 45° inclination with respect to the chord line. A significant lift augmentation is observed in all the three blade angle configurations due to the Gurney Flap. In terms of aerodynamic efficiency, it was observed that the presence of Gurney Flap was detrimental when βB = 45°, while the same was highly advantageous when βB = 135°. The streamline visualizations indicated the existence of counter rotating vortex pairs behind the Gurney Flap and that their rate of decay with respect to the Angle of attack was affected by the stagger angle at which the blades were arranged. [ABSTRACT FROM AUTHOR]

Computational investigations on the effect of Gurney flaps in a NACA 0010 cascade with a 90o blade angle were carried out using STARCCM+ code. The flaps were positioned at the trailing edge of the blades and were aligned at 45o and 90o to the blade chord. The variations in the lift, drag, aerodynamic efficiency and static pressure distributions were recorded on the blades and were compared with the baseline case. Significant increase in the lift coefficient was observed due to the Gurney flaps accompanied by a small drag penalty. This is achieved by increasing the effective camber of the blade, thereby increasing the pressure difference between the pressure and suction surfaces. The Gurney flaps increased the aerodynamic efficiency of the blade at lower angles of attack, whereas at higher angles a small drop in the value was observed. [ABSTRACT FROM AUTHOR]

The endeavor to improve the aerodynamic efficiency of supersonic flying bodies has been constant and significant ever since. Notably it has a significant contribution towards the growth of Aerospace industry. The rigorous experiments carried out on aerodynamic efficiency have led to the optimization of flying body design involving structural, aerodynamic or chemical performance parameters. Aerodynamic efficiency is the basis of energy-efficient flying model, and low drag is the basis of aerodynamic efficiency. The relative impact of drag depends upon the flight regime and specific design requirements. Hence, in the search of improving the aerodynamic efficiency and reducing the undesirable flight properties, specifically in supersonic regime, a channelised study has been carried out, as also being carried out many researchers across the world through different processes. Since shock waves create a considerable amount of drag, which can result in extreme drag on the supersonic body, it forms a significant area of study while aiming at improving the aerodynamic efficiency of a supersonic flying object. Hence, this paper deals with the reduction of wave drag by adopting cascade fin, which is a kind of fin that is still evolving in the aerospace environment. A cascade is a control surface which is composed of an external frame supporting an internal cascade of planar surfaces having small chord length. Various properties of cascade fin impact the aerodynamic efficiency individually and also in consonance with other properties. However specific properties of angle of attack and leading edge shape of cascade fin have been considered in this paper to evaluate their effect in reducing the wave drag of a supersonic flying object. This paper deals with these properties of cascade fin individually in isolation, in order to study and understand their impact in detail. The study on wave drag reduction by varying the angle of attack of cascade fins, in supersonic flow regime, has been carried out by adopting computational fluid dynamics simulation, performed for a Mach number of 2 and angle of attack of 0° and 5°. The study on wave drag reduction by varying the leading edges of cascade fins, in supersonic flow regime, has been carried out by adopting computational fluid dynamics simulation, performed for a Mach number of 2 and angle of attack of 0°. The study of varied leading edges considered have displayed significant variation of wave drag, but in practical application, a particular leading edge needs to be chosen as part of the larger scheme of aerodynamic designing process. [ABSTRACT FROM AUTHOR]