Flow Characteristics in S-Shaped Diffusing Duct

Majumdar, B. C.; Singh, Sadhna; Agrawal, D. P.

doi:10.1515/tjj.1997.14.1.45

Cited by 17 publications

(7 citation statements)

References 8 publications

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“…The overall static pressure recovery and total pressure loss coef®cients (+0.012) are 0.45 and 0.29, 0.40 and 0.33 and 0.35 and 0.28 for the diffusers with turning angles of 158/158, 22.58/22.58 and 308/308 respectively. The values of the pressure recovery coef®cient achieved are even lower than the values achieved by Majumdar et al [23] and Anand et al [25] for the rectangular S-shaped diffuser with a 908/908 turning angle. The likely reasons for these low values could be the loss of energy due to the generation of secondary¯ows and roughness of the surface (0.5 mm).…”

Section: Performance Characteristicscontrasting

confidence: 66%

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Effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers

Anand

Rai

Singh

2003

Proceedings of the Institution of Mechanical Engineers, Part G:

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The effect of the turning angle on the¯ow and performance characteristics of long Sshaped circular diffusers (length±inlet diameter ratio, L=D iˆ1 1:4) having an area ratio of 1.9 and centre-line length of 600 mm has been established. The experiments are carried out for three S-shaped circular diffusers having angles of turn of 158/158, 22.58/22.58 and 308/308. Velocity, static pressure and total pressure distributions at different planes along the length of the diffusers are measured using a ®ve-hole impact probe. The turbulence intensity distribution at the same planes is also measured using a normal hot-wire probe. The static pressure recovery coef®cients for 158/158, 22.58/22.58 and 308/308 diffusers are evaluated as 0.45, 0.40 and 0.35 respectively, whereas the ideal static pressure recovery coef®cient is 0.72. The low performance is attributed to the generation of secondary¯ows due to geometrical curvature and additional losses as a result of the high surface roughness (*0.5 mm) of the diffusers. The pressure recovery coef®cient of these circular test diffusers is comparatively lower than that of an S-shaped rectangular diffuser of nearly the same area ratio, even with a larger turning angle (908/908), i.e. 0.53. The total pressure loss coef®cient for all the diffusers is nearly the same and seems to be independent of the angle of turn. The¯ow distribution is more uniform at the exit for the higher angle of turn diffusers. NOTATIONA i cross-sectional area at the diffuser inlet (m 2 ) AR area ratioˆ…D o =D i † 2 C loss coef®cient of total pressure losŝ …P o i ¡ P oo †=P dyn…in † C p coef®cient of static pressure recoverŷ …P s o ¡ P s i †=P dyn…in † CC concave surface CR curvature ratioˆ2R c =D i CV convex surface dA elemental area to calculate the massaveraged quantities D i diameter of the test diffusers at the inlet (m) D n Dean numberˆR n =CR 1=2 D o diameter of the test diffusers at exit (m) F any¯ow parameter (static pressure, total pressure, velocity, etc.) L centre-line length (m) P dyn…in † dynamic pressure at the inlet 1 2rU 2 ave…in † …N=m 2 † P o i mass-averaged total pressure at the inlet (N/m 2 ) P oo mass-averaged total pressure at the outlet (N/m 2 ) P s i mass-averaged static pressure at the inlet (N/m 2 ) P so mass-averaged static pressure at the outlet (N/m 2 ) P wall wall static pressure (N/m 2 ) R radius of test diffuser (m) R c radius of curvature (m) R i radius at inlet (m) R n Reynolds numberˆrD i U ave…in † =m u 0 mean¯uctuating component of velocity (m/s) U local time-averaged (10 s) total velocity (m/s) U ave…in † mass-averaged velocity at the inlet (m/s) U long velocity in the axial direction (m/s) U sec cross-¯ow velocity (secondary motion) (m/s) x distance along the centre-line of the diffuser from the inlet plane (m)The MS was Downloaded from a pitch angle (deg) b turning angle of the curved diffuser (deg) y yaw angle (angle of rotation of the ®ve-hole probe) (deg) m absolute viscosity (Ns/m 2 ) r¯uid density (kg/m 3 ) f total angular position of the section from the inlet (deg)

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Section: Performance Characteristicscontrasting

confidence: 66%

“…The overall performance of the circular diffuser is comparatively lower than the rectangular diffuser Fig. 7 Variations of performance parameters along the length of the test diffusers having a larger turning angle (908/908) [23,25]. This may be due to the higher surface roughness of the present diffusers.…”

Section: Resultsmentioning

confidence: 93%

Effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers

Anand

Rai

Singh

2003

Proceedings of the Institution of Mechanical Engineers, Part G:

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“…In the present study, the k±e turbulence model is used as the closure equation. The geometry used for validation of the CFD code`FLUENT ' [17] is the same as used by Majumdar et al [10] and Singh et al [12]. The experimental results are compared with the predictions with air as the working¯uid.…”

Section: Validation Of the Codementioning

confidence: 99%

“…The experimental results are compared with the predictions with air as the working¯uid. The 908/908 rectangular diffuser geometry of Majumdar et al [10] and 158/158 circular diffuser [12] are modelled in GAMBIT. The boundary conditions at the inlet are speci®ed by assigning known values of the variables.…”

Section: Validation Of the Codementioning

confidence: 99%

Effect of angle-of-turn on the performance of divided intake ducts

Bharani¹,

Singh²,

Seshadri³

et al. 2004

Proceedings of the Institution of Mechanical Engineers, Part G:

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Investigations using computational¯uid dynamics (CFD) have been carried out on divided intake ducts having angles-of-turn as 22.58/22.58, 308/308 and 458/458 and area ratios of 2 and 3. It is observed that the core¯ow in the duct remains towards the convex walls up to the outlet plane with lower magnitudes in the centre of plane. Cross-velocity magnitudes are found to be less than 10 per cent of the longitudinal velocity at the outlet plane. Pressure recovery is found to decrease with the increase in the angle-of-turn for both area ratios.

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“…al. [2][3][4] has made detailed measurements on S-shaped rectangular duct having an area ratio 2 with inlet aspect ratio 6. Anand et al [5,6] [7] has developed an optimization theory for 3-D subsonic S-duct to reduce total pressure distortion and sustain total pressure recovery.…”

Section: Introductionmentioning

confidence: 99%