Analysis of Flow Migration in an Ultra-Compact Combustor

2011 ◽  
Author(s):  
Brian T. Bohan ◽  
Marc D. Polanka
Keyword(s):  
Ambient Pressure ◽  
Flow Characteristics ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Realistic Condition ◽  
Core Flow ◽  
Mixing Properties ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Outside Diameter

The Ultra Compact Combustor (UCC) has the potential to offer improved thrust-to-weight and overall efficiency in a turbojet engine. The thrust-to-weight improvement is due to a reduction in engine weight by shortening the combustor section through the use of the revolutionary UCC design. The improved efficiency is achieved by using an increased fuel-to-air mass ratio, and allowing the fuel to fully combust prior to exiting the UCC system. Furthermore, g-loaded combustion offers increased flame speeds that can lead to smaller combustion volumes. The circumferential combustion of the fuel in the UCC cavity results in hot gases present at the outside diameter of the core flow. This orientation creates an issue in that the flow from the circumferential cavity needs to migrate radially and blend with the core flow to present a uniform temperature distribution to the high-pressure turbine rotor. A computational fluid dynamics (CFD) analysis is presented for the flow patterns in the combustor section of a representative fighter-scale engine. The analysis included a study of secondary flows, cavity flow characteristics, shear layer interactions and mixing properties. An initial understanding of primary factors that impact the radial migration is presented. Computational comparisons were also made between an engine realistic condition and an ambient pressure rig environment.

Analysis of Flow Migration in an Ultra-Compact Combustor

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Brian T. Bohan ◽  
Marc D. Polanka
Keyword(s):  
Ambient Pressure ◽  
Turbine Rotor ◽  
Combustion Model ◽  
Velocity Control ◽  
Realistic Condition ◽  
Core Flow ◽  
Pressure Losses ◽  
The Core ◽  
Computational Fluid Dynamics Cfd

The ultra-compact combustor (UCC) has the potential to offer improved thrust-to-weight and overall efficiency in a turbojet engine. The thrust-to-weight improvement is due to a reduction in engine weight by shortening the combustor section through the use of the revolutionary circumferential combustor design. The improved efficiency is achieved by using an increased fuel-to-air mass ratio and allowing the fuel to fully combust prior to exiting the UCC system. Furthermore, g-loaded combustion offers increased flame speeds that can lead to smaller combustion volumes. One of the issues with the UCC is that the circumferential combustion of the fuel results in hot gases present at the outside diameter of the core flow. These hot gases need to migrate radially from the circumferential cavity and blend with the core flow to present a uniform temperature distribution to the high-pressure turbine rotor. The current research focused on correlations to control the UCC cavity velocity, control the temperature profile throughout the UCC section, analyze the exhaust species exiting the combustor, and quantify pressure losses in the system. To achieve these goals, a computational fluid dynamics (CFD) analysis was used on a UCC geometry scaled to a representative fighter-scale engine. The analysis included a study of cavity to core flow interaction characteristics, a 5- and 12-species combustion model of liquid and gaseous fuel, and determination of species exiting the combustor. Computational comparisons were also made between an engine realistic condition and an ambient pressure rig environment.

Effects of Core Flow Swirl on the Flow Characteristics of a Scalloped Forced Mixer

2011 ◽  
Author(s):  
Zhijun Lei ◽  
Ali Mahallati ◽  
Mark Cunningham ◽  
Patrick Germain
Keyword(s):  
Pressure Ratio ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Pressure Probe ◽  
Streamwise Vortices ◽  
Core Flow ◽  
The Core ◽  
Flow Swirl ◽  
Swirl Angle ◽  
Oil Flow

This paper presents a detailed experimental investigation of the influence of core flow swirl on the mixing and performance of a scaled turbofan mixer with 12 scalloped lobes. Measurements were made downstream of the mixer in a co-annular wind tunnel. The core-to-bypass velocity ratio was set to 2:1, temperature ratio to 1.0, and pressure ratio to 1.03, giving a Reynolds number of 5.2 × 105, based on the core flow velocity and equivalent hydraulic diameter. In the core flow, the background turbulence intensity was raised to 5% and the swirl angle was varied using five vane geometries from 0° to 30°. Seven-hole pressure probe measurements and surface oil flow visualization were used to describe the flowfield and the mixer performance. At low swirl angles, additional streamwise vortices were generated by the deformation of normal vortices due to the scalloped lobes. With increased core swirl, greater than 10°, the additional streamwise vortices were generated mainly due to radial velocity deflection, rather than stretching and deformation of normal vortices. At high swirl angles, stronger streamwise vortices and rapid interaction between various vortices promoted downstream mixing. Mixing was enhanced with minimal or no total pressure and thrust losses for the inlet swirl angles less than 10°. However, the reversed flow downstream of the center-body was a dominant contributor to the loss of thrust at the maximum core flow swirl angle of 30°.

Flow Characteristics of Double Serpentine Convergent Nozzle With Different Inlet Configuration

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Sun Xiao-Lin ◽  
Wang Zhan-Xue ◽  
Zhou Li ◽  
Shi Jing-Wei ◽  
Cheng Wen
Keyword(s):  
Flow Characteristics ◽  
Complex Flow ◽  
Convergent Nozzle ◽  
Core Flow ◽  
The Core ◽  
Setting Angle ◽  
Swirl Angle ◽  
Swirl Flows ◽  
Flow Features ◽  
Inlet Swirl

Serpentine nozzles have been used in stealth fighters to increase their survivability. For real turbofan aero-engines, the existence of the double ducts (bypass and core flow), the tail cone, the struts, the lobed mixers, and the swirl flows from the engine turbine, could lead to complex flow features of serpentine nozzle. The aim of this paper is to ascertain the effect of different inlet configurations on the flow characteristics of a double serpentine convergent nozzle. The detailed flow features of the double serpentine convergent nozzle including/excluding the tail cone and the struts are investigated. The effects of inlet swirl angles and strut setting angles on the flow field and performance of the serpentine nozzle are also computed. The results show that the vortices, which inherently exist at the corners, are not affected by the existence of the bypass, the tail cone, and the struts. The existence of the tail cone and the struts leads to differences in the high-vorticity regions of the core flow. The static temperature contours are dependent on the distributions of the x-streamwise vorticity around the core flow. The high static temperature region is decreased with the increase of the inlet swirl angle and the setting angle of the struts. The performance loss of the serpentine nozzle is mostly caused by its inherent losses such as the friction loss and the shock loss. The performance of the serpentine nozzle is decreased as the inlet swirl angle and the setting angle of the struts increase.

scholarly journals The Effects of the Presence of a Kitchen House on the Wind Flow Surrounding a Low-Rise Building

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6243
Author(s):  
Siti Noratikah Che Deraman ◽  
Saddam Hussein Abo Sabah ◽  
Shaharudin Shah Zaini ◽  
Taksiah A. Majid ◽  
Amin Al-Fakih
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Pattern ◽  
Air Flow ◽  
Flow Characteristics ◽  
Wind Flow ◽  
Cfd Simulations ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Gap Height

Most Malaysian rural houses are categorized as non-engineered buildings and vulnerable to damage during events such as windstorms due to the fact that these houses lack engineering considerations. These houses are characterized by having an attached kitchen house, and many of these houses were previously damaged by thunderstorms. The current research investigated the air flow characteristics changes surrounding these houses as a result of the presence of the kitchen. The roof pitch, position, gap height, and overhang were investigated using computational fluid dynamics (CFD) simulations. The results showed that the kitchen position at the center resulted in a slight increase in the suction on the ridge of the roof; however, it significantly altered the flow pattern in the windward and leeward directions. The results also showed that the roof overhang, roof pitch, and kitchen position contributed severely to the damage of the rural house. Moreover, the highest suction occurred at the roof ridge when the kitchen was located at the center of the rural house (Cp = −2.28). Therefore, the authors believe that it is more advantageous to have a kitchen connected to the core as it reduces the pressure on the roof of the core during thunderstorm events.

RANS Analyses of Turbofan Nozzles With Internal Wedge Deflectors for Noise Reduction

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
James R. DeBonis
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Noise Reduction ◽  
Turbulent Kinetic Energy ◽  
Large Scale ◽  
Navier Stokes ◽  
Core Flow ◽  
The Core ◽  
Computational Fluid Dynamics Cfd ◽  
Performance Results

Computational fluid dynamics (CFD) was used to evaluate the flow field and thrust performance of a promising concept for reducing the noise at take-off of dual-stream turbofan nozzles. The concept, offset stream technology, reduces the jet noise observed on the ground by diverting (offsetting) a portion of the fan flow below the core flow, thickening and lengthening this layer between the high-velocity core flow and the ground observers. In this study a wedge placed in the internal fan stream is used as the diverter. Wind, a Reynolds averaged Navier–Stokes (RANS) code, was used to analyze the flow field of the exhaust plume and to calculate nozzle performance. Results showed that the wedge diverts all of the fan flow to the lower side of the nozzle, and the turbulent kinetic energy on the observer side of the nozzle is reduced. This reduction in turbulent kinetic energy should correspond to a reduction in noise. However, because all of the fan flow is diverted, the upper portion of the core flow is exposed to the freestream, and the turbulent kinetic energy on the upper side of the nozzle is increased, creating an unintended noise source. The blockage due to the wedge reduces the fan mass flow proportional to its blockage, and the overall thrust is consequently reduced. The CFD predictions are in very good agreement with experimental flow field data, demonstrating that RANS CFD can accurately predict the velocity and turbulent kinetic energy fields. While this initial design of a large scale wedge nozzle did not meet noise reduction or thrust goals, this study identified areas for improvement and demonstrated that RANS CFD can be used to improve the concept.

Unsteady Flow/Quasi-Steady Heat Transfer Computations on a Turbine Rotor and Comparison With Experiments

2001 ◽  
Vol 124 (1) ◽  
pp. 152-159 ◽  
Author(s):  
T. Korakianitis ◽  
P. Papagiannidis ◽  
N. E. Vlachopoulos
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Turbine Rotor ◽  
Frequency Parameter ◽  
Unsteady Heat Transfer ◽  
Core Flow ◽  
The Core ◽  
Reduced Frequency ◽  
Steady Heat

The unsteady flow in stator–rotor interactions affects the structural integrity, aerodynamic performance of the stages, and blade-surface heat transfer. Numerous viscous and inviscid computer programs are used for the prediction of unsteady flows in two-dimensional and three-dimensional stator–rotor interactions. The relative effects of the various components of flow unsteadiness on heat transfer are under investigation. In this paper it is shown that for subsonic cases, the reduced frequency parameter for boundary-layer calculations is about two orders of magnitude smaller than the reduced frequency parameter for the core flow. This means that for typical stator–rotor interactions, the unsteady flow terms are needed to resolve the location of disturbances in the core flow, but in many cases the instantaneous disturbances can be input in steady-flow boundary-layer computations to evaluate boundary-layer effects in a quasi-steady approximation. This hypothesis is tested by comparing computations with experimental data on a turbine rotor for which there are extensive experimental heat transfer data available in the open literature. An unsteady compressible inviscid two-dimensional computer program is used to predict the propagation of the upstream stator disturbances into the downstream rotor passages. The viscous wake (velocity defect) and potential flow (pressure fluctuation) perturbations from the upstream stator are modeled at the computational rotor–inlet boundary. The effects of these interactions on the unsteady rotor flow result in computed instantaneous velocity and pressure fields. The period of the rotor unsteadiness is one stator pitch. The instantaneous velocity fields on the rotor surfaces are input in a steady-flow differential boundary-layer program, which is used to compute the instantaneous heat transfer rate on the rotor blades. The results of these quasi-steady heat-transfer computations are compared with the results of unsteady heat transfer experiments and with the results of previous unsteady heat transfer computations. The unsteady flow fields explain the unsteady amplitudes and phases of the increases and decreases in instantaneous heat transfer rate. It is concluded that the present method is accurate for quantitative predictions of unsteady heat transfer in subsonic turbine flows.

Numerical investigation on the flow field of a modified vortex spinning system for producing core-spun yarns

2019 ◽  
Vol 89 (19-20) ◽  
pp. 4028-4045
Author(s):  
Zeguang Pei ◽  
Ge Chen
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Swirling Flow ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Secondary Flows ◽  
Wall Region ◽  
The Core ◽  
Spun Yarns ◽  
Bottom Roller

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained.

Unsteady-Flow/Quasi-Steady Heat Transfer Computations on a Turbine Rotor and Comparison With Experiments

1993 ◽  
Author(s):  
T. Korakianitis ◽  
P. Papagiannidis ◽  
N. E. Vlachopoulos
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Turbine Rotor ◽  
Frequency Parameter ◽  
Unsteady Heat Transfer ◽  
Core Flow ◽  
The Core ◽  
Reduced Frequency ◽  
Steady Heat

The unsteady flow in stator-rotor interactions affects the structural integrity, aerodynamic performance of the cascades, and blade-surface heat transfer. Numerous viscous and inviscid computer programs are currently becoming available for the prediction of unsteady flows in two-dimensional and three-dimensional stator-rotor interactions. The relative effects of the various components of flow unsteadiness on heat transfer are currently under investigation. In this paper it is shown that for subsonic cases the reduced frequency parameter for boundary-layer calculations is about two orders of magnitude smaller than the reduced frequency parameter for the core flow. This means that for typical stator-rotor interactions the unsteady flow terms are needed to resolve the location of disturbances in the core flow, but in many cases the instantaneous disturbances can be input in steady-flow boundary-layer computations to evaluate boundary-layer effects in a quasi-steady approximation. This hypothesis is tested by comparing computations with experimental data on a turbine rotor for which there is extensive experimental heat-transfer data available in the open literature. An unsteady compressible inviscid two-dimensional computer program is used to predict the propagation of the upstream stator disturbances into the downstream rotor passages. The viscous wake (velocity defect) and potential flow (pressure fluctuation) perturbations from the upstream stator are modeled at the computational rotor-inlet boundary. The effects of these interactions on the unsteady rotor flow result in computed instantaneous velocity and pressure fields. The period of the rotor unsteadiness is one stator pitch. The instantaneous velocity fields on the rotor surfaces are input in a steady-flow differential boundary-layer program, which is used to compute the instantaneous heat-transfer rate on the rotor blades. The results of these quasi-steady heat-transfer computations are compared with the results of unsteady heat-transfer experiments and with the results of previous unsteady heat-transfer computations. The unsteady flow fields explain the unsteady amplitudes and phases of the increases and decreases in instantaneous heat-transfer rate. It is concluded that the present method is accurate for quantitative predictions of unsteady heat transfer in subsonic turbine flows.

Effects of Core Flow Swirl on the Flow Characteristics of a Scalloped Forced Mixer

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Zhijun Lei ◽  
Ali Mahallati ◽  
Mark Cunningham ◽  
Patrick Germain
Keyword(s):  
Pressure Ratio ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Equivalent Diameter ◽  
Streamwise Vortices ◽  
Core Flow ◽  
The Core ◽  
Flow Swirl ◽  
Swirl Angle ◽  
And Performance

This paper presents a detailed experimental investigation of the influence of core flow swirl on the mixing and performance of a scaled turbofan mixer with 12 scalloped lobes. Measurements were made downstream of the mixer in a coaxial wind tunnel. The core-to-bypass velocity ratio was set to 2:1, temperature ratio to 1.0, and pressure ratio to 1.03, giving a Reynolds number of 5.2 × 105, based on the core flow velocity and equivalent diameter. In the core flow, the background turbulence intensity was raised to 5% and the swirl angle was varied from 0 deg to 30 deg with five vane geometries. At low swirl angles, additional streamwise vortices were generated by the deformation of normal vortices due to the scalloped lobes. With increased core swirl, greater than 10 deg, the additional streamwise vortices were generated mainly due to radial velocity deflection, rather than stretching and deformation of normal vortices. At high swirl angles, stronger streamwise vortices and rapid interaction between various vortices promoted downstream mixing. Mixing was enhanced with minimal pressure and thrust losses for the inlet swirl angles less than 10 deg. However, the reversed flow downstream of the center body was a dominant contributor to the loss of thrust at the maximum core flow swirl angle of 30 deg.

Performance of lamella clarifiers for juice and syrup clarification

2017 ◽  
pp. 144-150
Author(s):  
Peter W. Rein ◽  
M. Getaz ◽  
A. Raghunandan ◽  
N. du Pleissis ◽  
H. Saleh ◽  
...  
Keyword(s):  
Residence Time ◽  
Flow Characteristics ◽  
Preliminary Test ◽  
Practical Experience ◽  
Operating Costs ◽  
Capital Costs ◽  
Computational Fluid Dynamics Cfd ◽  
Improved Performance ◽  
Work Done ◽  
Good Flow

A new design for syrup and juice clarifiers is presented. The design takes advantage of the considerably improved performance of clarifiers incorporating lamella plates, and the reasons for the improvement are outlined. Computational fluid dynamics (CFD) work done to simulate the performance is summarised. This design enables the residence time to be dramatically reduced and the simplified design leads to cheaper and better clarifiers. Practical experience with factory scale units is described, confirming the good flow characteristics. The results of preliminary test work on a factory syrup clarifier are presented, which is also shown to operate efficiently as a phosphatation clarifier. In addition the performance of a full-scale juice clarifier has been evaluated and compared with the performance of a Rapidorr clarifier. This work confirms the considerable advantages which this type of design provides, in realising substantial reductions in residence time, capital costs and operating costs.

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