scholarly journals Numerical Investigation of flow through Annular diffusing duct

2011 ◽  
pp. 60-63
Author(s):  
Prasanta K. Sinha ◽  
Ananta Kumar Das ◽  
Bireswar Majumdar
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Line Length ◽  
Area Ratio ◽  
Experimental Results ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Mean Velocity ◽  
Inlet Conditions

In the present investigation the distribution of mean velocity, static pressure and total pressure are experimentally studied on an annular curved diffuser of 30° angle of turn with an area ratio of 1.283 and centerline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent and then a series of parametric investigations are conducted with same centre line length and inlet diameter but with different area ratios varying from 1.15 to 3.75. The measurements were taken at Reynolds number 2.25 x 105 based on inlet diameter and mass average inlet velocity. Predicted results of coefficient of mass averaged static pressure recovery (30%) and coefficient of mass averaged total pressure loss (21%) are in good agreement with the experimental results of coefficient of mass averaged static pressure recovery (26%) and coefficient of mass averaged total pressure loss (17%) respectively. Standard k-ε model in Fluent solver was chosen for validation. From the parametric investigation it is observed that static pressure recovery increases up to an area ratio of 2.86 and between the area ration 2.86 to 3.75, pressure recovery decreases steadily. The coefficient of total pressure loss almost remains constant with the change in area ratio for similar inlet conditions.

Flow Investigation Through a 30° Turn Diffusing Duct in Subsonic Flow Regime

2009 ◽  
Author(s):  
Prasanta K. Sinha ◽  
Biswajit Haldar ◽  
Amar N. Mullick ◽  
Bireswar Majumdar
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Pressure Probe ◽  
Mean Velocity

Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate effective operation of the combustor by reducing the total pressure loss. The performance characteristics of these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of axial velocity, transverse velocity, mean velocity, static and total pressures are experimentally studied on a curved diffuser of 30° angle of turn with an area ratio of 1.27. The centreline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent, the commercial CFD software. The measurements of axial velocity, transverse velocity, mean velocity, static pressure and total pressure distribution were taken at Reynolds number 1.9 × 105 based on inlet diameter and mass average inlet velocity. The mean velocity and all the three components of mean velocity were measured with the help of a pre-calibrated five-hole pressure probe. The velocity distribution shows that the flow is symmetrical and uniform at the inlet and exit sections and high velocity cores are accumulated at the top concave surface due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The mass average static pressure recovery and total pressure loss within the curved diffuser increases continuously from inlet to exit and they attained maximum values of 35% and 14% respectively. A comparison between the experimental and predicated results shows a good qualitative agreement between the two. Standard k-ε model in Fluent solver was chosen for validation. It has been observed that coefficient of pressure recovery Cpr for the computational investigation was obtained as 38% compared to the experimental investigation which was 35% and the coefficient of pressure loss is obtained as 13% in computation investigation compared to the 14% in experimental study, which indicates a very good qualitative matching.

The Influence of Inlet Conditions on the Performance of Annular Diffusers

1980 ◽  
Vol 102 (3) ◽  
pp. 357-363 ◽  
Author(s):  
S. J. Stevens ◽  
G. J. Williams
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Turbulence Structure ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Outlet Flow ◽  
Inlet Conditions ◽  
Uniform Diameter

Low speed tests have been carried out to investigate the performance and mechanism of flow in two annular diffusers having center bodies of uniform diameter and conically diverging outer walls. In the first part of the investigation the diffusers were tested over a range of naturally developed inlet velocity profiles ranging from near-uniform to fully developed flow. Information is presented concerning the pressure recovery, total pressure loss, and characteristics of the outlet flow. Measurements have also been made of the mean velocity profile and turbulence structure at a number of stations along the length of the diffusers. The second part of the test program was devoted to studying the effects of increased inlet turbulence. The results show a marked improvement in the stability of the outlet flow and gains in pressure recovery, up to a maximum of 20 percent, with only small increases in total pressure loss.

Numerically Optimizing an Annular Diffuser Using a Genetic Algorithm With Three Objectives

2012 ◽  
Author(s):  
David J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Genetic Algorithm ◽  
Pressure Loss ◽  
Total Pressure ◽  
Exhaust System ◽  
Outer Wall ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Annular Diffuser ◽  
Inlet Conditions ◽  
Wall Profile

A genetic algorithm was implemented to determine preferential solutions of a short annular diffuser exhaust system of length 1.5Do (outer annulus diameters). Five free variables defined the centre body shape and two variables determined the outer wall profile. Diffuser performance was evaluated using three objectives—(i) diffuser pressure recovery, (ii) outlet velocity uniformity, and (iii) total pressure loss—that were calculated from steady state solutions obtained using the computational fluid dynamics software FLUENT 13.0 with the realizable k-ε turbulence model and enhanced wall treatment. Inlet conditions were ReDh = 8.5 × 104 and M = 0.23. After thirty-five generations, a paraboloid-shaped centre body with length 0.74Do and initial annular expansion of approximately 14° produced preferential solutions. A configuration with a converging outer wall above the centre body developed greater outlet flow uniformity and lower total pressure loss whereas a straight outer wall followed by the solid diffuser generated more static pressure recovery.

Flow Measurements in a Fishtail Diffuser With Strong Curvature

1999 ◽  
Vol 121 (2) ◽  
pp. 410-417 ◽  
Author(s):  
M. I. Yaras
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Cross Sectional ◽  
Inlet Flow ◽  
Inlet Conditions ◽  
Strong Curvature

The paper presents detailed measurements of the incompressible flow development in a large-scale 90 deg curved diffuser with strong curvature and significant streamwise variation in cross-sectional aspect ratio. The flow path approximates the so-called fishtail diffuser utilized on small gas turbine engines for the transition between the centrifugal impeller and the combustion chamber. Two variations of the inlet flow, differing in boundary layer thickness and turbulence intensity, are considered. Measurements consist of three components of velocity, static pressure and total pressure distributions at several cross-sectional planes throughout the diffusing bend. The development and mutual interaction of multiple pairs of streamwise vortices, redistribution of the streamwise flow under the influence of these vortices, the resultant streamwise variations in mass-averaged total-pressure and static pressure, and the effect of inlet conditions on these aspects of the flow are examined. The strengths of the vortical structures are found to be sensitive to the inlet flow conditions, with the inlet flow comprising a thinner boundary layer and lower turbulence intensity yielding stronger secondary flows. For both inlet conditions a pair of streamwise vortices develop rapidly within the bend, reaching their peak strength at about 30 deg into the bend. The development of a second pair of vortices commences downstream of this location and continues for the remainder of the bend. Little evidence of the first vortex pair remains at the exit of the diffusing bend. The mass-averaged total pressure loss is found to be insensitive to the range of inlet-flow variations considered herein. However, the rate of generation of this loss along the length of the diffusing bend differs between the two test cases. For the case with the thinner inlet boundary layer, stronger secondary flows result in larger distortion of the streamwise velocity field. Consequently, the static pressure recovery is somewhat lower for this test case. The difference between the streamwise distributions of measured and ideal static pressure is found to be primarily due to total pressure loss in the case of the thick inlet boundary layer. For the thin inlet boundary layer case, however, total pressure loss and flow distortion are observed to influence the pressure recovery by comparable amounts.

scholarly journals Optimization Study of the Dump Diffuser in Gas Turbine to Reduce Pressure Loss

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Fei Xing ◽  
Hao Su ◽  
Shining Chan ◽  
Leilei Xu ◽  
Xinyi Yu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Method ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Test Model ◽  
Gap Ratio ◽  
Efficient Combustion ◽  
The Impact

As a key component-connecting compressor and the entrance of combustion chamber, the diffuser is able to increase the pressure and slow down the airflow in order to promote efficient combustion as well as avoid a large amount of pressure loss. In this paper, experimental investigation and numerical studies have been carried out to understand the effects of air bleeding from dump region and dump gap ratio on the total pressure loss and static pressure recovery of the dump diffusers. The ultimate objective is optimizing the dump diffuser design to get the maximum static pressure recovery and minimum total pressure loss. A simplified test model is used to study the effect of the air bleeding from the outer dump region and the dump gap ratio on the total pressure loss and static pressure recovery in the dump diffuser. The impact of the dump gap ratio in the performance of the dump diffusers has also been discussed. Nearly all the pressure raise occurs in the prediffuser, and most of the total pressure loss occurs in the dump region. For the recirculating area in the dump region, the controllable vortex can be introduced. Bleeding air from the outer dump region can improve the velocity distribution near the flame tube. The results show that when 0.4% of the air is bled from outer dump region, the performance of the dump diffuser is optimal. Hence, the controllable vortex method is effective for improving the performance of the dump diffuser.

Experimental Study of the Flow and Pressure Drop Performances in Advanced Combustor Distributor Diffuser

2013 ◽  
Author(s):  
H. X. Liang ◽  
J. Q. Suo ◽  
M. Li
Keyword(s):  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Performance ◽  
Area Ratio ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Flow Rates ◽  
Turbine Engine ◽  
Outlet Flow

Gas turbine engine uses diffuser system to decelerate the compressor exit flow velocity before it enters combustor, it is important to design the compact structure and high performance of the diffuser for gas turbine engine. The diffuser and combustor dome configurations are critical flow path parameters in the design of a low-pressure-loss, high-performance combustion system. With rising of the inlet Mach number of the combustor, dramatically increasing of the diffuser total pressure loss and flow separation. So a new distributor diffuser was designed. In this paper preliminary results from an experimental investigation into the aerodynamic performance on a rectangle combustor-diffuser system with seven distributor plates were presented. Measurements were taken in the diffuser section to assess the diffuser performance characteristics under various conditions, the appropriate outlet flow field can be attained by changing the plate area ratio and form. Tests were carried out to investigate the influence of distributor diffuser plate geometry. During these measurements for each parametric configuration, data were obtained at 24 different flow rates through the distributor diffuser, it gave the conclusion that the distributor diffuser area ratio could be more than traditional diffusers with shorter construction and higher pressure recovery performance, while the flow loss through it was not beyond the traditional limit. Overall static pressure recovery improves and overall total pressure loss reduces with increasing distributor diffuser area ratio, and the increased flow rates through the distributor diffuser gave rise to a higher total pressure loss. The total pressure loss fraction was less than 2.5% when Mach number changed from 0.3 to 0.38; if the area ratio was more than 2.1, the diffuser loss coefficient remained less than 0.3, pressure recovery coefficient more than 0.5 and area ratio up to 2.45. There exists an area ratio in 1.6∼2.0 which makes diffuser outlet flow field distribution more uniform; Baffle structure can adjust the flow field distribution of outlet diffuser. As a result, the distributor diffuser can be potentially satisfied with demands for high performance combustor.

An Investigation of the Tapered Strut On Aerodynamic Performance of the Exhaust Diffuser Under Different Swirls

2021 ◽  
Author(s):  
Yuxuan Dong ◽  
Zhigang Li ◽  
Jun Li
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Flow Process ◽  
Loss Mechanism ◽  
Recovery Coefficient ◽  
Pressure Recovery Coefficient

Abstract The exhaust diffuser with different struts was numerically calculated by solving three-dimensional Reynolds-Averaged Navier-Stokes (RANS). The flow process and flow loss mechanism in the diffuser were analyzed, the influence of two different structures of tapered struts on the aerodynamic performance of the exhaust diffuser under different inlet pre-swirls was explored, and the aerodynamic performance of the exhaust diffuser with tapered struts was compared with a conventional exhaust diffuser with linear struts. The results show that, compared with the conventional linear strut, under different inlet pre-swirls, two different tapered struts can both weaken the flow separation in the exhaust diffuser, thereby reducing the total pressure loss. When the inlet pre-swirl is greater than 0.35, the total pressure loss coefficient of the exhaust diffuser with structure-C tapered struts decreases by up to 0.07. The two types of tapered struts also change the flow structure at the exhaust diffuser outlet, which affects the uniformity of the outlet airflow, and then affect the static pressure recovery coefficient. Under different inlet pre-swirls, two types of tapered struts can be effective to increase the static pressure recovery coefficient of the exhaust diffuser, for the exhaust diffuser with structure-C tapered struts, the static pressure recovery coefficient can be increased by up to 0.065, relative increase of 20%. The research in this paper shows that the tapered structure can significantly improve the aerodynamic performance of the exhaust diffuser under different inlet pre-swirls.

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.

Secondary Flow Control Using Vortex Generator Jets

2004 ◽  
Vol 126 (4) ◽  
pp. 650-657 ◽  
Author(s):  
R. K. Sullerey ◽  
A. M. Pradeep
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Generator ◽  
Control Flow ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Vortex Generators ◽  
Vortex Generator Jets ◽  
Inflow Conditions

In this paper, results are presented of an experimental investigation into the effectiveness of vortex generator jets in controlling secondary flows in two-dimensional S-duct diffusers. The experiments were performed in uniform and distorted inflow conditions and the performance evaluation of the diffuser was carried out in terms of static pressure recovery and quality of the exit flow. In the case with inflow distortion, tapered fin vortex generators were employed in addition to vortex generator jets to control flow separation that was detected on the wall with inflow distortion. Detailed measurements including total pressure, velocity distribution, surface static pressure, skin friction, and boundary layer measurements were taken at a Reynolds number of 7.8×105. These results are presented in terms of static pressure rise, distortion coefficient, and total pressure loss coefficient at the duct exit. For uniform inflow, the use of vortex generator jets resulted in more than a 30 percent decrease in total pressure loss and flow distortion coefficients. In combination with passive device (tapered fin vortex generators), the vortex generator jets reduce total pressure losses by about 25 percent for distorted inflow conditions. A potential application of this method may include control of secondary flows in turbo machinery.

Experimental investigation of the role of struts in high speed mixing

2013 ◽  
Vol 117 (1188) ◽  
pp. 193-211 ◽  
Author(s):  
S. L. N. Desikan ◽  
J. Kurian
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Mie Scattering ◽  
Total Pressure Loss ◽  
Pressure Losses ◽  
Mixing Performance ◽  
Supersonic Mixing

AbstractThis paper presents the experimental results of the role of struts in supersonic mixing. Experiments were carried out with novel strut configurations to show their capabilities on mixing with reasonable total pressure losses. The performances were compared with the Baseline Strut configurations (BSPI and BSNI). The analysis presented includes the mixing quantifications using Mie scattering signature, flow field visualisation, measurement of wall static pressure and the total pressure loss calculations. The results clearly demonstrated that the proposed strut configurations achieved increased mixing (7-8%) compared to BSPI with increase in total pressure loss (2%). On the other hand, when compared with BSNI, the mixing performance was found to be decreased by 6% with reduced total pressure loss (12%).

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