Strut Losses in a Diverging Annular Diffuser With Swirling Flow

2006 ◽  
Author(s):  
G. K. Feldcamp ◽  
A. M. Birk
Keyword(s):  
Total Pressure ◽  
Swirling Flow ◽  
Pressure Recovery ◽  
Swirl Number ◽  
Pressure Losses ◽  
Swirl Angle ◽  
Wide Range ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
The Ideal

An experimental investigation into the overall influence of struts spanning a double divergent annular diffuser followed by a straight cored annular diffuser has been undertaken in order to determine the performance of various strut configurations over a wide range of inlet swirl conditions. Two strut profiles have been investigated in four and eight strut configurations. Results have shown that the presence of struts under no swirl conditions have a relatively small effect on the overall total pressure loss. Increasing the inlet swirl angle to 20° has shown that the struts are able to assist in recovery of the swirling flow such that the pressure recovery nearly approaches that without struts, despite increased total pressure losses. Performance at 40° swirl is highly dependent on strut profile; the higher thickness-to-chord ratio strut configurations show minimal decrease in pressure recovery compared to 20° swirl, while the lower thickness-to-chord ratio configurations experiences a significant decrease as the result of significant flow separation from the struts. The exit swirl number has been shown to correlate strongly with the strut profile shape, while the number of struts had only a secondary influence. The exit velocity profiles show significant distortions at 40° swirl, and as a result the ideal pressure recovery calculated from the inlet and exit profiles change with strut configuration at 40° swirl.

Performance characteristics of flow in annular diffuser using CFD

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hardial Singh ◽  
Bharat Bhushan Arora
Keyword(s):  
Swirling Flow ◽  
Flow Behavior ◽  
Pressure Recovery ◽  
Ansys Fluent ◽  
Pressure Loss Coefficient ◽  
Swirl Angle ◽  
Swirl Intensity ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Total Pressure Loss Coefficient

Abstract An annular diffuser is a critical component of the turbomachinery, and its prime function is to reduce the flow velocity. The current work is carried to study the effect of four different geometrical designs of an annular diffuser using the ANSYS Fluent. The numerical simulations were carried out to examine the effect of fully developed turbulent swirling and non-swirling flow. The flow behavior of the annular diffuser is analyzed at Reynolds number 2.5 × 105. The simulated results reveal pressure recovery improvement at the casing wall with adequate swirl intensity at the diffuser inlet. Swirl intensity suppresses the flow separation on the casing and moves the flow from the hub wall to the casing wall of the annulus region. The results also show that the Equal Hub and Diverging Casing (EHDC) annular diffuser in comparison to other diffusers has a higher static pressure recovery (C p  = 0.76) and a lower total pressure loss coefficient of (C L  = 0.12) at a 17° swirl angle.

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°.

Effect of Prediffuser Angle on the Static Pressure Recovery in Flow Through Casing-Liner Annulus of a Gas Turbine Combustor at Various Swirl Levels

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Prakash Ghose ◽  
Amitava Datta ◽  
Achintya Mukhopadhyay
Keyword(s):  
Gas Turbine ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Recovery ◽  
Gas Turbine Combustor ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Inlet Swirl ◽  
Flow Through ◽  
The Ideal

A numerical study has been performed in an axisymmetric diffuser followed by a casing-liner annulus of a typical gas turbine combustor to analyze the flow structure and pressure recovery in the geometry. Static pressure recovery in a gas turbine combustor is important to ensure high pressure of air around the liner. However, the irreversible pressure losses reduce the static pressure recovery from the ideal value. The presence of swirl in the flow from compressor and prediffuser geometry before the dump diffuser influences the flow pattern significantly. In this study, flow structures are numerically predicted with different prediffuser angles and inlet swirl levels for different dump gaps. Streamline distributions and pressure plots on the casing and liner walls are analyzed. Static pressure recovery coefficients are obtained from the pressure distributions across the combustor. The effect of dump gap on the static pressure recovery has also been evaluated. It is observed that the best static pressure recovery can be obtained at optimum values of inlet swirl level and prediffuser angle. Dump gap is found to have significant influence on the static pressure recovery only at small prediffuser angle.

Effect of Swirl on the Performance of an Annular Diffuser

2015 ◽  
Vol 787 ◽  
pp. 318-321
Author(s):  
R. Prakash ◽  
V. Karthik Srinivas ◽  
H. Anand ◽  
G. Adithya ◽  
N. Lakshmi Narayanan
Keyword(s):  
General Pattern ◽  
Pressure Recovery ◽  
Maximum Pressure ◽  
Swirl Number ◽  
Number Range ◽  
Flow Parameters ◽  
Efficient Performance ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Numerical Variation

Annular diffusers are primarily used to convert the kinetic energy of the exhaust flow into pressure energy. The performance of the diffusers are often measured using pressure recovery maps, that generally do not consider the distortion of flow at the inlet due to other upstream machine components. A high swirl velocity at the inlet could often account for large energy losses and hence it is necessary to curb the swirl component by appropriate design considerations. In this present work,it is desired to establish the swirl number range at the inlet of an annular diffuser for its effective and efficient performance and increased pressure recovery of the diffuser. “Swirl effect” on the fluid flow parameters with and without struts is compared, to give the idea of the numerical variation in the parameters.Computational fluid dynamics (CFD) analysis was performed to determine the maximum pressure recovery based on variations in the inlet swirl number. Thus, the flow was studied under varied conditions and a relation between the input parameters and the general pattern of flow for the specified input conditions was critically examined.

Effects of Scalloping on the Mixing Mechanisms of Forced Mixers With Highly Swirling Core Flow

2012 ◽  
Author(s):  
Alex Wright ◽  
Zhijun Lei ◽  
Ali Mahallati ◽  
Mark Cunningham ◽  
Julio Militzer
Keyword(s):  
Swirling Flow ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Suction Surface ◽  
Reduced Pressure ◽  
Core Flow ◽  
Pressure Losses ◽  
Swirl Angle ◽  
Inlet Swirl ◽  
Mixing Rates

This paper presents a detailed experimental and computational investigation of the effects of scalloping on the mixing mechanisms of a scaled 12-lobe turbofan mixer. Scalloping was achieved by eliminating approximately 70% of the lobe sidewall area. Measurements were made downstream of the mixer in a co-annular wind tunnel and the simulations were carried out using an unstructured RANS solver, Numeca FINE/Hexa, with k-ω SST model. In the core flow, the swirl angle was varied from 0° to 30°. At high swirl angles, a three-dimensional separation bubble was formed on the lobe’s suction surface penetration region and resulted in the generation of a vortex at the lobe valley. The valley vortex quickly dissipated downstream. Most of the swirl was removed by the lobes, but scalloping allowed residual swirl to persist downstream of the mixer. The interaction of the swirling flow and the vortices resulted in improved mixing rates for the scalloped mixer. Inlet swirl up to 10° provided improved mixing rates, reduced pressure loss and thrust loss for both mixers. High inlet swirl resulted in improved mixing but produced higher pressure and thrust losses as compared to the zero swirl case. At high swirl, the scalloped mixer resulted in better mixing and lower pressure losses than the unscalloped mixer, but at the expense of reduced thrust.

scholarly journals Effect of swirl flow on the performance of parallel hub axial annular diffuser

2021 ◽  
Author(s):  
Hardial Singh ◽  
◽  
Arora B.B ◽  
Keyword(s):  
Swirling Flow ◽  
Cone Angle ◽  
Axial Flow ◽  
Swirl Flow ◽  
Recovery Coefficient ◽  
Pressure Loss Coefficient ◽  
Swirl Angle ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Result Analysis

In the present work, the parallel hub axial flow annular diffuser's performance characteristics with divergent casing varying between equivalent cone angle (10°, 15°, and 20°) with area ratio 3 have been evaluated computationally as well as experimentally. The performance of three diffusers were tested at different inlet swirl angles (from 0° to 25°) for swirling and non-swirling flow. Simulations have been carried out on a fully developed flow at Reynolds number 2.5×105. The results were analyzed based on the velocity profiles, static pressure recovery coefficient, and the total pressure loss coefficient. The result analysis shows that the inlet swirl flow improves the recovery of pressure and also delays the flow separation on the casing. Moreover,the findings also show that the best performance was achieved in equivalent cone angle 10° at the inlet swirl angle of 7.5° compared to other diffusers.

Numerical Analysis on the CO-NO Formation Production near Burner Throat in Swirling Flow Combustion System

2014 ◽  
Vol 69 (2) ◽  
Author(s):  
Mohamad Shaiful Ashrul Ishak ◽  
Mohammad Nazri Mohd Jaafar
Keyword(s):  
Swirling Flow ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Recirculation Region ◽  
Mixing Enhancement ◽  
Ansys Fluent ◽  
Pressure Losses ◽  
No Formation ◽  
Swirl Angle ◽  
Air Mixing

The main purpose of this paper is to study the Computational Fluid Dynamics (CFD) prediction on CO-NO formation production inside the combustor close to burner throat while varying the swirl angle of the radial swirler. Air swirler adds sufficient swirling to the inlet flow to generate central recirculation region (CRZ) which is necessary for flame stability and fuel air mixing enhancement. Therefore, designing an appropriate air swirler is a challenge to produce stable, efficient and low emission combustion with low pressure losses. A liquid fuel burner system with different radial air swirler with 280 mm inside diameter combustor of 1000 mm length has been investigated. Analysis were carried out using four different radial air swirlers having 30°, 40°, 50° and 60° vane angles. The flow behavior was investigated numerically using CFD solver Ansys Fluent. This study has provided characteristic insight into the formation and production of CO and pollutant NO inside the combustion chamber. Results show that the swirling action is augmented with the increase in the swirl angle, which leads to increase in the center core reverse flow, therefore reducing the CO and pollutant NO formation. The outcome of this work will help in finding out the optimum swirling angle which will lead to less emission.  

Effects of Rotating Blade Wakes on Separation and Pressure Recovery in Turbine Exhaust Diffusers

2008 ◽  
Author(s):  
Olaf Sieker ◽  
Joerg R. Seume
Keyword(s):  
Boundary Layer ◽  
High Energy ◽  
Flow Coefficient ◽  
Pressure Recovery ◽  
High Mass ◽  
Scale Model ◽  
Swirl Number ◽  
Annular Diffuser ◽  
Bladed Rotor ◽  
Turbine Exhaust

Highly efficient turbine exhaust diffusers can only be designed by taking into account the unsteady interactions with the last rotating row of the turbine. Therefore, a scale model of a typical gas turbine exhaust diffuser consisting of an annular and a conical diffuser is investigated experimentally. To investigate the influence of rotating wakes, a variable-speed rotating spoke wheel with cylindrical spokes as well as with NACA bladed spokes generates high-energy turbulent wakes simulating turbine rotor wakes. For the rotor with the NACA blades, the drive of the wheel is run in motor as well as in generator mode. Additional measurements in a reference configuration without a spoke wheel allow the detailed analysis of changes in the flow pattern. 3-hole pneumatic probes, static pressure taps, as well as a 2D-Laser-Doppler-Velocimeter (LDV) are used to investigate velocity profiles and turbulent characteristics. Without the wakes generated by a spoke wheel, the annular diffuser (with a 20° half cone opening angle) separates at the shroud for all swirl configurations. Increasing the swirl results in increasing pressure recovery at the shroud whereas the hub boundary is destabilized. For a non-rotating spoke rotor and low swirl numbers, the 20° annular diffuser separates at the shroud. Increasing the swirl number, a strong deceleration of the axial velocity at the shroud is generated without separation and a higher pressure recovery is achieved. The boundary layer at the shroud of the 20° annular diffuser separates for all operating points with the bladed rotor. A partly stabilized 20° annular diffuser can only be achieved for much higher values of the flow coefficient than that for the design point. At this high mass flow, the NACA-bladed rotor operates as a turbine, resulting in the generator mode of the electric drive. Contrary to the numerical design calculations, the flow at the shroud of a 15° annular diffuser does not separate for all swirl configurations in the experiment. Pressure recovery of the 15° annular diffuser can be increased by increasing the inlet swirl whereas the hub boundary layer is destabilized. For the NACA bladed rotor, the flow in the 15° annular diffuser as well as the pressure recovery strongly depend on the flow coefficient. For flow coefficients lower than the design value, the flow partly separates at the shroud whereas large flow coefficients result in increased pressure recovery. The pressure recovery also depends on the direction of swirl and thus the swirl number.

Development, Analysis, and Validation of a Simultaneous Inlet Total Pressure and Swirl Distortion Generator

2020 ◽  
Author(s):  
Dustin J. Frohnapfel ◽  
K. Todd Lowe ◽  
Walter F. O’Brien
Keyword(s):  
Total Pressure ◽  
Experimental Validation ◽  
Computational Analysis ◽  
Pressure Recovery ◽  
Turbofan Engine ◽  
Full Field ◽  
Inlet Distortion ◽  
Swirl Angle ◽  
Total Pressure Recovery ◽  
Ground Test

Abstract Over the last decade, the Turbomachinery and Propulsion Research Laboratory at Virginia Tech has researched, invented, developed, computationally analyzed, experimentally tested, and improved turbofan engine inlet distortion generators. This effort began with modernizing and improving inlet total pressure distortion screens originally conceived over half a century ago; continued with the invention of inlet swirl distortion generators (StreamVanes™) made possible only through advances in modern additive manufacturing technology; and has, thus far, culminated in a novel combined device (ScreenVanes™) capable of simulating realistic flight conditions of coupled inlet total pressure and swirl distortion in a ground-test turbofan engine research platform. The present research focuses on the methodology development, computational analysis, and experimental validation of a novel simultaneous inlet total pressure and swirl distortion generator. A case study involving a single bend S-duct inlet distortion profile demonstrates the ability to generate a high-fidelity profile simulation, yet outlines a design process sufficiently generic for application to any arbitrary inlet geometry or distortion profile. A computational fluid dynamics simulation of the S-duct inlet provided the target profile extracted at the aerodynamic interface plane. Next, utilizing a method of inverse propagation, the planar distortion profile was propagated upstream to yield a flow field that could be manufactured by a distortion generator adequately isolated from turbomachinery effects. The total pressure distortion screen and swirl distortion StreamVane components were then designed and computationally analyzed. Upon successful computational reproduction of the S-duct inlet distortion profile, experimental hardware was fabricated and tested to validate the ScreenVane methodology and distortion generating device. Comparison of the S-duct manufactured distortion and the ScreenVane manufactured distortion was used as the primary criterion for profile replication success. Results from a computational analysis of both the S-duct and ScreenVane indicated excellent agreement in distortion pattern shape, extent, and intensity with full-field total pressure recovery and swirl angle profiles matching within approximately 0.80% and 2.6°, respectively. Furthermore, experimental validation of the ScreenVane indicated nearly identical full-field total pressure recovery and swirl angle profile replication of approximately 1.10% and 2.6°, respectively, when compared to the computational results. The investigation concluded that not only was the ScreenVane device capable of accurately simulating a complex inlet distortion profile, but also produced a viable device for full-scale turbofan engine ground test.

Sign in / Sign up

Export Citation Format

Share Document