Influence of Inlet Shape on Twin Intake Duct Performance

2005 ◽  
Author(s):  
K. Saha ◽  
S. N. Singh ◽  
V. Seshadri
Keyword(s):  
Static Pressure ◽  
Cross Flow ◽  
Geometrical Parameters ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Secondary Motion ◽  
Vortical Motion ◽  
Total Pressure Loss Coefficient ◽  
Pressure Recovery Coefficient ◽  
Oval Shape

Performance of twin intake ducts with different inlet shapes has been analyzed using a commercial CFD (Computational Fluid Dynamics) code. The performance has been evaluated for incompressible flow at a fixed Reynolds number (1.4×105). The shapes studied are rectangular (Aspect ratio = 2), square, semicircular, elliptic-1, elliptic-2 (inverse-elliptic) and oval shape with all the other geometrical parameters remaining same. The performance of the twin intake ducts in terms of the static pressure recovery coefficient, total pressure loss coefficient and distortion coefficient, and the secondary motion at the merging plane and the downstream planes show that the inverse elliptic shape is the best followed by semi-circular inlet. The vectors plots of secondary motion at the merging plane and downstream have shown the presence of twin pairs of vortical motion possibly caused by the change in centerline curvature. The cross flow vector plots also show four distinct vortices after merger.

Effects of casing angle on the performance of parallel hub axial annular diffuser

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Hardial Singh ◽  
B.B. Arora
Keyword(s):  
Static Pressure ◽  
Swirling Flow ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Swirl Angle ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Total Pressure Loss Coefficient ◽  
Pressure Recovery Coefficient

Abstract In this paper, the effects of non-swirling and swirling flow on the performance of parallel hub axial annular diffuser has been investigated. The study was conducted on a fully developed swirling flow and non-swirling flow to predict the separation of the flow from the wall. Three different annular diffusers were used with casing wall angles of 3°, 6°, and 9°. Furthermore, various swirl angles (0–25°) at the inlet of diffusers have been investigated to analyze the performance across the length. It was found that parallel hub axial annular diffuser performance increases up to a certain length as the inlet swirl angle increases. However, the performance also improves as the diffuser area ratio (AR) increases. The performance is evaluated based on the static pressure recovery coefficient (Cp) and the total pressure loss coefficient (CTL). The highest possible pressure recovery is achieved by the 12° swirl angle with a casing angle of 6°.

scholarly journals Effects of casing angle on the performance of parallel hub axial annular diffuser

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Hardial Singh ◽  
B.B. Arora
Keyword(s):  
Static Pressure ◽  
Swirling Flow ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Swirl Angle ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Total Pressure Loss Coefficient ◽  
Pressure Recovery Coefficient

AbstractIn this paper, the effects of non-swirling and swirling flow on the performance of parallel hub axial annular diffuser has been investigated. The study was conducted on a fully developed swirling flow and non-swirling flow to predict the separation of the flow from the wall. Three different annular diffusers were used with casing wall angles of 3°, 6°, and 9°. Furthermore, various swirl angles (0–25°) at the inlet of diffusers have been investigated to analyze the performance across the length. It was found that parallel hub axial annular diffuser performance increases up to a certain length as the inlet swirl angle increases. However, the performance also improves as the diffuser area ratio (AR) increases. The performance is evaluated based on the static pressure recovery coefficient (Cp) and the total pressure loss coefficient (CTL). The highest possible pressure recovery is achieved by the 12° swirl angle with a casing angle of 6°.

Numerical Investigation of Vaneless Diffuser by Pinching and Rotation

2019 ◽  
Author(s):  
Porika Niveditha ◽  
Bhamidi V. S. S. S. Prasad
Keyword(s):  
Pressure Loss ◽  
Static Pressure ◽  
Stagnation Pressure ◽  
Pressure Recovery ◽  
Vaneless Diffuser ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Energy Coefficient ◽  
Pressure Recovery Coefficient ◽  
Isentropic Efficiency

Abstract Non-conventional diffuser designs are introduced to minimize the energy losses associated with diffusion and to enhance stable operating range of the diffusion system. This is achieved by reducing width of the diffuser by modifying a hub or shroud curves by keeping the diffuser diameter ratio constant which is often known as pinch. The comparison of modified compressor with base model is accomplished by using performance characteristics such as static pressure recovery coefficient, stagnation pressure loss coefficient, energy coefficient and isentropic efficiency. Simulations are performed at various hub pinch (5%–20%), shroud pinch (5%–20%) and combined hub and shroud pinch (5%–20%). Among all the cases shroud pinch of 10% shows best results in terms of stagnation pressure loss coefficient, static pressure recovery coefficient and energy coefficient. Further, simulations are carried out with forced rotating vaneless diffuser. It gives better results in terms of pressure rise with lower stagnation pressure losses. But there is a moderate decrement in isentropic efficiency of compressor when compared to the base model.

Experimental Study of Flow in a High Aspect Ratio 90 Deg Curved Diffuser

1998 ◽  
Vol 120 (1) ◽  
pp. 83-89 ◽  
Author(s):  
B. Majumdar ◽  
Ratan Mohan ◽  
S. N. Singh ◽  
D. P. Agrawal
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Static Pressure ◽  
Pressure Probe ◽  
Hot Wire ◽  
Recovery Coefficient ◽  
Wire Probe ◽  
Concave Wall ◽  
Vortical Motion ◽  
Pressure Recovery Coefficient

Measurements for developing turbulent flow in a high aspect ratio (AS = 6), small area ratio (AR = 2), 90 deg curved diffuser have been made. Mean velocities, static and total pressures, and turbulence intensities were measured using a three-hole pressure probe and a hot-wire probe. Flow visualization studies were also made using a tuft probe. Experiments show that, except for a very small zone near the exit, there is no flow reversal in any part of the diffuser. Streamwise bulk flow is seen to shift toward the concave wall side in the downstream half of the diffuser, under the influence of centrifugal force. One pair of counter-rotating vortical motion was identified at 30 deg turn, which break into more pairs (at least two) of counter-rotating vortices in the downstream. The z-plane velocity profiles show a nearly 2-D flow in the initial part of the diffuser but subsequently the flow becomes increasingly 3-D. A static pressure recovery coefficient of 51 percent was achieved.

scholarly journals Effect of Clearance Gap in Spiral Casing Design of a Centrifugal Fan with Optimized Impellers

2019 ◽  
Vol 4 (9) ◽  
pp. 181-185
Author(s):  
Ardit Gjeta
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Geometrical Parameters ◽  
Centrifugal Fan ◽  
Recovery Coefficient ◽  
Parameter Variations ◽  
Set Up ◽  
Operating Points ◽  
Spiral Casing ◽  
Pressure Recovery Coefficient

Industrial fans are subject to European Union energy labeling and Ecodesign requirements. By using more efficient industrial fans, Europe will save 34 TWh and avoid 16 million tones of CO2 emissions annually by 2020 [1]. In this paper, the effect of the clearance gap between the impeller and the volute, on the performance of a centrifugal fan was investigated using open source CFD software OpenFOAM [2]. An automized loop with RANS and data post-processing is set up using Matlab, for allowing a large number of parameter variations. We conducted numerical analysis for all operating points, where starting points are optimal impellers for the whole range of specific speeds [3], [4]. The effect of volute angle and geometrical parameters related to the tongue [5], on total pressure loss, static pressure recovery coefficient and on efficiency are presented.

Outlet Surface Area Influence in Spiral Casing Design on Centrifugal Fan Performance

2020 ◽  
Vol 5 (1) ◽  
pp. 37-41
Author(s):  
Ardit Gjeta ◽  
Lorenc Malka
Keyword(s):  
Surface Area ◽  
Static Pressure ◽  
Total Efficiency ◽  
Centrifugal Fan ◽  
Recovery Coefficient ◽  
Fan Performance ◽  
Parameter Variations ◽  
Set Up ◽  
Spiral Casing ◽  
Pressure Recovery Coefficient

In this paper, the effect of the outlet surface area of the spiral casing on the performance of a centrifugal fan was investigated using open source CFD software OpenFOAM [1]. An automized loop with RANS and data post-processing is set up using Matlab, for allowing a large number of parameter variations. The effect was analyzed as a function of total pressure loss and static pressure recovery coefficient and on total efficiency as well.

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

2003 ◽  
Vol 217 (1) ◽  
pp. 29-41 ◽  
Author(s):  
R B Anand ◽  
L Rai ◽  
S N Singh
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Area Ratio ◽  
Secondary Flows ◽  
Performance Characteristics ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Turning Angle ◽  
And Performance ◽  
Pressure Recovery Coefficient

The effect of the turning angle on the flow and performance characteristics of long S-shaped circular diffusers (length-inlet diameter ratio, L/Di = 11:4) 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 15°/15°, 22.5°/22.5° and 30°/30°. Velocity, static pressure and total pressure distributions at different planes along the length of the diffusers are measured using a five-hole impact probe. The turbulence intensity distribution at the same planes is also measured using a normal hot-wire probe. The static pressure recovery coefficients for 15°/15°, 22.5°/22.5° and 30°/30° diffusers are evaluated as 0.45, 0.40 and 0.35 respectively, whereas the ideal static pressure recovery coefficient is 0.72. The low performance is attributed to the generation of secondary flows due to geometrical curvature and additional losses as a result of the high surface roughness (~0.5 mm) of the diffusers. The pressure recovery coefficient 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 (90°/90°), i.e. 0.53. The total pressure loss coefficient for all the diffusers is nearly the same and seems to be independent of the angle of turn. The flow distribution is more uniform at the exit for the higher angle of turn diffusers.

Some Studies on Low Solidity Vaned Diffusers of a Centrifugal Compressor Stage

2005 ◽  
Author(s):  
T. Ch. Siva Reddy ◽  
G. V. Ramana Murty ◽  
Prasad Mukkavilli ◽  
D. N. Reddy
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Pressure Recovery ◽  
Compressor Stage ◽  
Recovery Coefficient ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Centrifugal Compressor Stage ◽  
Pressure Recovery Coefficient

Numerical simulation of impeller and low solidity vaned diffuser (LSD) of a centrifugal compressor stage is performed individually using CFX- BladeGen and BladeGenPlus codes. The tip mach number for the chosen study was 0.35. The same configuration was used for experimental investigation for a comparative study. The LSD vane is formed using standard NACA profile with marginal modification at trailing edge. The performance parameters obtained form numerical studies at the exit of impeller and the diffuser have been compared with the corresponding experimental data. These parameters are pressure ratio, polytropic efficiency and flow angle at the impeller exit where as the parameters those have been compared at the exit of diffuser are the static pressure recovery coefficient and the exit flow angle. In addition, the numerical prediction of the blade loading in terms of blade surface pressure distribution on LSD vane has been compared with the corresponding experimental results. Static pressure recovery coefficient and flow angle at diffuser exit is seen to match closely at higher flows. The difference at lower flows could be due to the effect of interaction between impeller and diffuser combinations, as the numerical analysis was done separately for impeller and diffuser and the effect of impeller diffuser interaction was not considered.

A Preliminary Study of Annular Diffusers With Constant Diameter Outer Walls (Suitable for Turbine Exits)

1983 ◽  
Author(s):  
R. C. Adkins ◽  
O. H. Jacobsen ◽  
P. Chevalier
Keyword(s):  
Static Pressure ◽  
Short Length ◽  
Pressure Recovery ◽  
Recovery Coefficient ◽  
Constant Diameter ◽  
Preliminary Study ◽  
Pressure Recovery Coefficient

A systemmatic series of tests has been conducted on a family of annular diffusers where the outer casing is maintained at constant diameter. Such a diffuser is typical of turbine exits. Data, in the form of static pressure recovery coefficient is plotted against diffuser length for several different designs of centerbody closure. It has been shown that such diffusers can have short length centerbodies for which a set of design guides has been established.

scholarly journals Experimental and Computational Study of Hybrid Diffusers for Gas Turbine Combustors

2003 ◽  
Author(s):  
A. Duncan Walker ◽  
Paul A. Denman ◽  
James J. McGuirk
Keyword(s):  
Gas Turbine ◽  
Computational Study ◽  
Detailed Examination ◽  
Momentum Equation ◽  
Finite Limit ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Radial Depth ◽  
Flow Mechanisms ◽  
Total Pressure Loss Coefficient

The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the prediffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This paper will report on one such unconventional diffuser; the hybrid diffuser which, under the action of bleed, has been shown to achieve high rates of diffusion in relatively short lengths. However, previous studies have not been conducted under representative conditions and have failed to provide a complete description of the relevant flow mechanisms making optimisation difficult. Utilising an isothermal representation of a modern gas turbine combustor an experimental investigation was undertaken to study the performance of a hybrid diffuser compared to that of a conventional, single passage, dump diffuser system. The hybrid diffuser achieved a 53% increase in area ratio within the same axial length generating a 13% increase in the pre-diffuser static pressure recovery coefficient which, in turn, produced a 25% reduction in the combustor feed annulus total pressure loss coefficient. A computational investigation was also undertaken in order to investigate the governing flow mechanisms. A detailed examination of the flow field, including an analysis of the terms within the momentum equation, demonstrated that the controlling flow mechanisms were not simply a boundary layer bleed but involve a more complex interaction between the accelerating bleed flow and the diffusing mainstream flow. A greater understanding of these mechanisms enabled a more practical design of hybrid diffuser to be developed that not only simplified the geometry but also improved the quality of the bleed air making it more attractive for use in component cooling.

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