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عنوان فارسی مقاله:
بررسی بیرون آوردن لایه مرزی برای مقاومت در برابر فشار در یک عایق
عنوان انگلیسی مقاله:
Investigation of boundary-layer ejecting for resistance to back pressure in an isolator
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
The inlet and isolator are important aerodynamic components in an air-breathing engine [1,2]. In these compression systems, shock-wave/boundary-layer interaction (SWBLI) is a complex physical phenomenon of compressible viscous flow. After a type of precombustion shock train inside the inlet undergoes multiple reflections, it can thicken boundary layer [3], cause flow distortions [4] and even induce flow separation [5]. At this point, if the combustor back pressure is too high for the shock-train length to match, unstart can occur. It is therefore critical to effectively control the boundary-layer flow to improve the performance of propulsion system and increase the stability margins. Methods to control or minimize shock-induced flow separation have been proposed and are mainly classified as passive and active control. Control nature, whether passive or active, manages to increase the momentum of fluid near the wall so that the boundary layer can withstand the adverse pressure gradient imposed by incident shock or heat release at high equivalence ratio. Of these * Corresponding author. Address for correspondence: No. 92, West Da-Zhi Street, Harbin, Heilongjiang, 150001, PR China. E-mail address: yudaren@hit.edu.cn (D. Yu). methods, since the suction control was first brought forward, its application has lasted to the present time. It can remove the low energy boundary-layer flow and reduce the size of the separation through a perforated domain [6–8]. Although suction provides many benefits to the propulsion system, its use often comes at a cost of increased drag and weight of the aircraft, thereby increasing the system complexity [9]. Another attractive control technique is micro vortex generators such as the micro-ramps. Saad et al. [10] performed the wind tunnel experiments at Mach 5 with two micro-ramps of different sizes to investigate the control of shockwave/boundary-layer interaction and revealed the mechanism of the flow control device through schlieren visualization technique, surface flow visualization, and a new type of luminescent measurement technique such as infrared thermography [11]. Oorebeek et al. [12] devised a normal shock experiment with a supersonic inflow of Mach 1.35 to investigate the vortex generator and bleed effectiveness suppressing flow separation. They found that the vortex generator is similar to the bleed and can considerably reduce the separation bubble size, thereby improving the diffuser performance. Martis et al. [13] conducted a three dimensional numerical investigation to analyze the effect of micro-ramps on the separated swept shock-wave/boundary layer interactions. They analyzed the parametric influence of the height, width, and spacingof the micro-ramps and drew a conclusion that the micro-ramps can significantly delay the boundary-layer separation. Alternatively, the larger height of micro-ramps can be more conductive to delaying the flow separation. Although the vortex generator can induce pairs of counter-rotating streamwise vortices to mix the high momentum fluid of core flow with the near-wall low momentum boundary layer flow, there is still a potential hazard of engine damage if the structure is destroyed [14]. Recently, an array of continuous air jet vortex generators (AJVGs) on upstream surface of separation bubble is used to successfully reduce the separation bubble size through inducing the periodical change of velocity which can redistribute the boundary-layer momentum, but the effectiveness is reduced at off design conditions [15]. However, the most of research mainly focuses on a single point control of separation bubble. Fewer investigations on the back pressure control can be seen. It is thus necessary to utilize a control method in inlet model to restrain the upstream propagation of adverse pressure gradient and simultaneously avoid several disadvantages of above methods.
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کلمات کلیدی:
Shock Waves: Proceedings of the 24th International Symposium on ... https://books.google.com/books?isbn=3540270094 Zonglin Jiang - 2010 - Science Numerical investigation on the mixing and combustion in supersonic ejecting flow ... shock wave, boundary layer, chemical reactions in the ejecting and mixing ... Viscous Drag Reduction: Proceedings of the Symposium on Viscous Drag ... https://books.google.com/books?isbn=1489955798 C. Sinclair Wells - 2013 - Technology & Engineering Results of this ejection study are presented into two different ways in Figure H. Region l represents ... the ejected solution within the entire turbulent boundary layer, utilizing the l/7-power velocity distribution. ... In order to investigate further ... An Experimental Investigation of the Effect of Ejecting a Coolant Gas at ... authors.library.caltech.edu/61712/ by CHE Warren - 1958 - Cited by 2 - Related articles Oct 29, 2015 - An Experimental Investigation of the Effect of Ejecting a Coolant Gas at ... which the coolant was injected into the boundary layer so increased ... Unsteady separation in vortex-induced boundary layers rsta.royalsocietypublishing.org/content/roypta/372/2020/20130348.full.pdf by KW Cassel - 2014 - Cited by 4 - Related articles Both steady and unsteady boundary-layer separation are induced by an adverse ... investigators to search for more generalized criteria of separation that would hold .... and infinite thickness in the normal direction, thereby ejecting boundary-. The Benthic Boundary Layer: Transport Processes and Biogeochemistry https://books.google.com/books?isbn=0199770913 Bernard P. Boudreau, Bo Barker Jorgensen - 2001 - Science The ejection of brightly dyed fluid packets from the near-wall region was observed to be ... High-resolution measurements in the boundary layer. ... (1996) manipulated dissolved gas and solute concentrations to investigate the response of ...
