Experimental investigation of exhaust system mixers for a high bypass turbofan engine

Abolfadl, Mohamed; Sehra, Arun K.

doi:10.2514/6.1993-22

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…Povinelli et al [8] and Paterson [9,10] subsequently found that there were large-scale secondary motions in the wake of the lobed forced mixer while conducting the NASA energy efficient engine (E 3 ) investigation programmes. Researchers such as Presz et al [5], Barber et al [11], Skebe et al [12], Koutmos and McGuirk [13], Eckerle et al [14], Abolfadl and Sehra [15], Presz et al [16], Tew et al [17], Yu and Yip [6], Yu and Xu [18] studied the fluid dynamic characteristics of the lobed forced mixer either experimentally or numerically. The gross features of the flow field were examined in their investigations, and mostly focused on the formation and development of the streamwise vortices.…”

Section: Introductionmentioning

confidence: 99%

Kelvin - Helmholtz and Streamwise Vortices in the Near Wake of a Single-Lobe Forced Mixer

Mao

Chua

2006

Proceedings of the Institution of Mechanical Engineers, Part G:

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In the present experimental investigation, the characteristics of two types of vortices, namely the normal Kelvin-Helmholtz (K-H) and streamwise vortices, generated in the near wake of a lobed forced mixer were examined and evaluated at two velocity ratios (r = U1: U2 = 1:1 and 0.4:1). The lobed forced mixer has only one lobe and was designed to eliminate any possible interactions between the neighbouring vortices generated by the adjacent lobes. Hot-wire anemometer was used to study the K-H vortices via the spectrum analysis. Laser-Doppler anemometer was employed to examine the streamwise vortices. It was found that there were two main frequencies for the K-H vortex in the wake of the forced mixer ( fLM_C and fLM_L); both were higher than the case of plane-free shear layer ( fFP), i.e., fLM_C fLM_L fFP. where fLM_C represents the K-H vortex shedding frequency in the behind the semi-circle part of the trailing edge, whereas fLM_L represents the frequency in the near wake behind the parallel side-walls of the trailing edge. The velocity ratio appeared to have more important effects at point C than at point L. The Strouhal numbers ( StLM_C and StLM_L) reached constant values at the Reynolds number greater than 5 × 105. The K-H vorticities for the velocity ratio r= 0.4 was ∼30 and 110 per cent stronger than for case r= 1 for points L and C, respectively. The K-H vortices were also found to be more contributive to the production of the turbulent kinetic energy in the near wake of the single-lobe forced mixer than the streamwise vortices. The streamwise vortices at r= 0.4 accelerated the breakdown of the K-H vortices, which happened at about one wavelength earlier than r= 1. Finally, the effects of geometry parameters, including lobe height (or penetration angle) and wavelength, were examined.

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Section: Introductionmentioning

confidence: 99%

Kelvin - Helmholtz and Streamwise Vortices in the Near Wake of a Single-Lobe Forced Mixer

Mao

Chua

2006

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…Farly preliminary investigations [17][18][19][20] were mainly focused on estimating the influence of geometric parameters on the performance of forced exhaust mixers including the number of lobes, lobe radial penetration angles, lobe shape and length, etc. Results from these studies provided a data base for optimizing the design of turbofan forced mixer exhaust system.…”

Section: Introductionmentioning

confidence: 99%

Parametric Effects on Internal Aerodynamics of Lobed Mixer-Ejector With Curved Mixing Duct

Pan

Shan

Zhang

2014

Journal of Engineering for Gas Turbines and Power

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The internal flow characteristics inside lobed mixer-ejector with curved mixing duct and the parametric effects on the lobed mixer-ejector performance are investigated numerically and validated by experimental test. The cwved mixing duct ajfects the development of the streamwise vortices induced by the lobed mixer. When the mixing process undergoes the transition from the straight section to the bent section, the flow inside the cwved mixing duct is dominated by the impinging and centrifugal ejfects. In general, the pumping ratio is decreased approximately 20%-30% once the bent section is mounted on the straight duct. The mixer-ejector performance could by improved by increasing the straight section length, due to more fully momentum utilization of primary jet and weaker influence of bent section on the back pressure near nozzle exit. The mixer-ejector pumping capacity is also augmented with the increase of mixing duct area ratio until the area ratio is reached to 3.5. And the fully-utilization of primary jet momentum inside mixing duct with big area ratio needs long mixing distance. The pumping ratio is decreased as the increase of bent angle of curved mixing duct in approximately linear relationship. When the bent angle exceeds 45 deg, the thermal mixing efficiency is decreased rapidly as the increase of bent angle.

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“…Meanwhile, from the fuel savings, full fuel combustion can be achieved by enhancing the mixing of reactants while delaying ignition in a controlled manner (Smith et al 1997;Mitchell et al 2004). Previous studies show that the scalloping of lobed nozzles can improve the mixing performance (Presz et al 1994;Abolfadl and Sehra 1993;Yu et al 1997Yu et al , 2000Hu et al 1999;Mao et al 2009;Lei 2011) but cause some extra total pressure loss (Hu et al 1999). Presz et al (1994) found that the scalloping could generate additional vortices, which are upstream the lobe exit plane.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Scalloping Width and Position on Jet Mixing of Lobed Nozzles

Liu

Huang

Sheng

et al. 2015

J.Aerosp. Technol. Manag.

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A series of geometric models of lobed nozzles with a central plug was created by different scalloping positions and widths. The shapes of lower and upper edges, cutting depth were kept unchanged. In this study, by the use of numerical simulation, the effects of scalloped width and position on the performance of jet mixing in the pumping condition were analyzed. The results indicated that, as the position of scalloped lower edge kept constant, the radial position of the accelerated mixing region of sidewalls did not change. The accelerated mixing region is enlarged as scalloped width increased, while the growth rate of enlarged region is less than the growth rate of scalloping width. When the scalloped region with the same width moved outward in the radial direction, the mixing rate of the region of the lobe outer edges increased. However, the distance for complete mixing of the primary stream in the core region was increased. It was also found that inward moving of scalloped lower edge enhanced the effect of strengthening streamwise vortices but induced more pressure loss.

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Experimental investigation of exhaust system mixers for a high bypass turbofan engine

Cited by 4 publications

References 3 publications

Kelvin - Helmholtz and Streamwise Vortices in the Near Wake of a Single-Lobe Forced Mixer

Kelvin - Helmholtz and Streamwise Vortices in the Near Wake of a Single-Lobe Forced Mixer

Parametric Effects on Internal Aerodynamics of Lobed Mixer-Ejector With Curved Mixing Duct

The Effects of Scalloping Width and Position on Jet Mixing of Lobed Nozzles

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