The Effect of the Geometric Modifications of the Venturi on the Non-Reactive Flow and Combustion Behavior Using a Counter-Rotating Radial-Radial Swirler

2017 ◽  
Author(s):  
Sheng-Chieh Lin ◽  
Xionghui Wang ◽  
Wessam Estefanos ◽  
Samir Tambe ◽  
San-Mou Jeng
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Behavior ◽  
Dynamic Pressure ◽  
Vertical Plane ◽  
Reactive Flow ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Ambient Conditions ◽  
Cross Sectional

An experimental study was conducted to perform an analysis of the effect of the geometric modifications of the venturi on the non-reactive and reactive flow behavior using a counter-rotating radial-radial swirler. In the non-reactive flow tests, measurements were taken in a central vertical plane and horizontal (cross-sectional) plane at the exit of the swirler, using a High-Speed, Two Dimensional, Particle Image Velocimetry (2D PIV) system. The size of the swirler used in the non-reactive flow tests is a 4.76X scaled size of the swirler used in combustion. The 4.76X swirler models were tested in air flow seeded with olive oil at Re = 51,500, corresponding to the pressure drop across the 1X swirler models of 4% of atmospheric pressure at ambient conditions. Compared with the 1X swirler models, the 4.76X swirler models provide high spatial and temporal resolutions from the enhanced visibility of the flow characteristics and lower velocities at the same Re. Four swirler configurations of high swirl number (SN ≈ 1.0) were used, with no modification for the baseline configuration (configuration 1), and with the chevrons on the venturi for the straight chevrons configuration (configuration 2). The design of the inclined venturi was used for the converging venturi configuration (configuration 3), and chevrons were added on the converging venturi for the converging chevrons configuration (configuration 4). In the combustion tests, the 1X swirler models were tested using 478K preheated air at 4% pressure drop across the swirler, and different chamber lengths. Measurements were conducted using a regular camera to capture the flame image, and dynamic pressure transducers to obtain the acoustic pressure oscillations. Four configurations were studied and compared in the non-reactive and reactive flows with the objective of understanding the mechanisms responsible in reducing the extent of the combustion instabilities. Results of this study show that the converging venturi in configuration 3 appears to be the best design in eliminating the combustion instabilities in the fuel-lean region as compared to the other configurations. This indicates that the prevention of the frequencies coupling between the heat release rate and acoustic oscillations has been achieved by using the design of the converging venturi.

Experimental Investigation of Combustion Dynamics in a Turbulent Syngas Combustor

2017 ◽  
Author(s):  
Nikhil Ashokbhai Baraiya ◽  
Baladandayuthapani Nagarajan ◽  
Satynarayanan R. Chakravarthy
Keyword(s):  
High Speed ◽  
Equivalence Ratio ◽  
Bluff Body ◽  
Dynamic Pressure ◽  
Fuel Mixture ◽  
High Amplitude ◽  
Acoustic Oscillations ◽  
Combustion Dynamics ◽  
Dynamic Pressure Measurement ◽  
Body Location

In the present work, the proportion of carbon monoxide to hydrogen is widely varied to simulate different compositions of synthesis gas and the potential of the fuel mixture to excite combustion oscillations in a laboratory-scale turbulent bluff body combustor is investigated. The effect of parameters such as the bluff body location and equivalence ratio on the self-excited acoustic oscillations of the combustor is studied. The flame oscillations are mapped by means of simultaneous high-speed CH* and OH* chemiluminescence imaging along with dynamic pressure measurement. Mode shifts are observed as the bluff body location or the air flow Reynolds number/overall equivalence ratio are varied for different fuel compositions. It is observed that the fuel mixtures that are hydrogen-rich excite high amplitude pressure oscillations as compared to other fuel composition cases. Higher H2 content in the mixture is also capable of exciting significantly higher natural acoustic modes of the combustor so long as CO is present, but not without the latter. The interchangeability factor Wobbe Index is not entirely sufficient to understand the unsteady flame response to the chemical composition.

Experimental and Numerical Investigation of Near-Nozzle Flow Behaviour Under Flash Boiling Conditions

2017 ◽  
Author(s):  
Bo Wang ◽  
Xinyu Zhang ◽  
Yuying Yan ◽  
Jean-Paul Kone
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Near Field ◽  
Air Entrainment ◽  
Nozzle Flow ◽  
Ambient Conditions ◽  
Fuel Temperature ◽  
Long Distance ◽  
Significant Difference ◽  
Flash Boiling

Precise control of the spray behavior is key to fully realize the potential benefits of modern GDI engines. Flash boiling is known to alert the spray behavior significantly; and thus, a complete understanding of its mechanism is essential. In this work, a study of the effect of the fuel properties on the near-nozzle flow characteristics of a single-hole GDI injector under the flash boiling conditions is presented. The performance of hexane and a typical gasoline surrogate iso-octane has been studied both experimentally and numerically. Fuel temperature varied from 20 and 100 °C with ambient pressures of 20, 50 and 100 kPa. For the experiment, microscopic imaging was conducted with a high-speed camera coupled with a long-distance microscope; and a convex lens was used to provide enough illumination to the interested area. The numerical studies were performed at the maximum needle lift using OpenFOAM, an open-source Computational Fluid Dynamics (CFD) code. Phase change was captured with the Homogeneous Relaxation Model (HRM); and turbulence was modeled using RNG k–ε model. The results have shown that while the near-field flow behavior of hexane and isooctane was similar under ambient conditions, a significant difference was observed between the two under the flash boiling conditions. The onset and development of flash boiling of isooctane was retarded compared to hexane due to its much lower vapor pressure. Spray contraction has been observed in the down-stream due to fuel vaporization and air entrainment. The CFD results were shown to agree well with the experimental data.

scholarly journals Flame Edge Dynamics and Interaction in a Multi-Nozzle Can Combustor With Fuel Staging

2019 ◽  
Author(s):  
Daniel Doleiden ◽  
Wyatt Culler ◽  
Ankit Tyagi ◽  
Stephen Peluso ◽  
Jacqueline O’Connor
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Pollutant Emissions ◽  
Destructive Interference ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Oscillation Phase ◽  
Phase Cancellation ◽  
Flame Dynamics ◽  
Fuel Staging

Abstract The characterization and mitigation of thermoacoustic combustion instabilities in gas turbine engines is necessary to reduce pollutant emissions, premature wear, and component failure associated with unstable flames. Fuel staging, a technique in which the fuel flow to a multi-nozzle combustor is unevenly distributed between the nozzles, has been shown to mitigate the intensity of self-excited combustion instabilities in multiple nozzle combustors. In our previous work, we hypothesized that staging suppresses instability through a phase-cancellation effect in which the heat release rate from the staged nozzle oscillates out of phase with that of the other nozzles, leading to destructive interference that suppresses the instability. This previous theory, however, was based on chemiluminescence imaging, which is a line-of-sight integrated technique. In this work, we use high-speed laser-induced fluorescence to further investigate instability suppression in two staging configurations: center-nozzle and outer-nozzle staging. An edge-tracking algorithm is used to compute local flame edge displacement as a function of time, allowing instability-driven edge oscillation phase coherence and other instantaneous flame dynamics to be spectrally and spatially resolved. Analysis of flame edge oscillations shows the presence of convecting coherent fluctuations of the flame edge caused by periodic vortex shedding. When the system is unstable, these two flame edges oscillate together as a result of high-intensity longitudinal-mode acoustic oscillations in the combustor that drive periodic vortex shedding at each of the nozzle exits. In the stable cases, however, the phase between the oscillations of the center and outer flame edges is greater than 90 degrees (∼114 degrees), suggesting that the phase-cancellation hypothesis may be valid. This analysis allows a better understanding of the instantaneous flame dynamics behind flame edge oscillation phase offset and fuel staging-based instability suppression.

Combustion Stability and Emissions in a Lean Premixed Industrial Gas Turbine Burner Due to Changes in the Fuel Profile

2009 ◽  
Author(s):  
A. Lindholm ◽  
D. Lo¨rstad ◽  
P. Magnusson ◽  
P. Andersson ◽  
T. Larsson
Keyword(s):  
Pressure Drop ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Speed ◽  
Dynamic Pressure ◽  
Image Intensifier ◽  
Flame Stabilization ◽  
Combustion Stability ◽  
Fuel Profile ◽  
Industrial Gas Turbine

This paper deals with an experimental investigation of dry low emission (DLE) burners for industrial gas turbines. Changes in the fuel profile, pressure drop over the burner and external pilot flame stabilization have been investigated regarding combustion stability and emissions. This has been achieved by parallel experimental work in a water rig and a newly commissioned atmospheric combustion test rig. Some verifying tests in a high pressure rig were also conducted. The work in the water rig has been directed towards evaluating different fuel profiles at the burner exit due to changes in the fuel outlet geometry. Variations of the fuel outlet geometry were achieved by altering the effective area of the hardware configuration of the fuel outlet ports or by moving or adding fuel outlet ports. A few of the tested configurations in the water rig was chosen for further evaluation by atmospheric combustion tests with respect to combustion stability and emissions. A more general study on combustion stability and emissions was also performed for different burners, burner configurations and variations in pressure drop over the burner. The pressure drop over the burner in the test corresponds very well to the pressure drop measured over a single burner in an annular combustion chamber of an industrial gas turbine at different loads. The combustion was monitored by a high speed video camera equipped with an image intensifier. Simultaneously the dynamic pressure was measured by a piezoelectric pressure transducer, making it possible to know when each image was taken relative to the pressure. Results for different hardware configurations will be shown considering the frequency response from the flame and the dynamic pressure as well as the characteristic combustion instability close to lean blowout.

Experimental Investigation of Pressure Drop of Gas/Non-Newtonian Flow in Horizontal Pipes

2020 ◽  
Author(s):  
Faraj Ben Rajeb ◽  
Mohamed Odan ◽  
Syed Imtiaz ◽  
Yan Zhang ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Oil And Gas ◽  
Flow Behavior ◽  
Pressure Sensors ◽  
Newtonian Flow ◽  
Two Phase ◽  
Point Pressure ◽  
To Come ◽  
Gas Liquid Flow

Abstract Two-phase flow of gas/non-Newtonian fluid through pipes is commonly occurred in chemical industry and oil and gas refinery. Many correlations have been developed to evaluate pressure drop for non-Newtonian fluids. Based on that, these systems are not governed by Newtonian law of viscosity. However, only little experimental work has been devoted to study non-Newtonian flow behavior. In this present work, experimental setup has been conducted to investigate non-Newtonian two-phase (gas/ liquid) flow through pipes. Several concentrations of Xanthan Gum have been used as non-Newtonian liquid in the experiments and compressed air has been used as a gas. The flow rate and pressure of liquid and gas are changed by using a pump placed ahead of the mixing point. Pressure and temperature values are recorded by pressure sensors and thermocouples fixed at specific points along the pipe loop. Results of theses experiments are leaded to come up with experimental model for pressure drop of gas/non-Newtonian flow in pipes. Moreover, the flow regimes of two-phase gas/non-Newtonian flow at different conditions have been visualized through transparent tubes using a high-speed camera.

scholarly journals Flame Edge Dynamics and Interaction in a Multinozzle Can Combustor With Fuel Staging

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Daniel Doleiden ◽  
Wyatt Culler ◽  
Ankit Tyagi ◽  
Stephen Peluso ◽  
Jacqueline O'Connor
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Pollutant Emissions ◽  
Destructive Interference ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Previous Theory ◽  
Oscillation Phase ◽  
Flame Dynamics ◽  
Fuel Staging

The characterization and mitigation of thermoacoustic combustion instabilities in gas turbine engines are necessary to reduce pollutant emissions, premature wear, and component failure associated with unstable flames. Fuel staging, a technique in which the fuel flow to a multinozzle combustor is unevenly distributed between the nozzles, has been shown to mitigate the intensity of self-excited combustion instabilities in multiple nozzle combustors. In our previous work, we hypothesized that staging suppresses instability through a phase-cancelation effect in which the heat release rate from the staged nozzle oscillates out of phase with that of the other nozzles, leading to destructive interference that suppresses the instability. This previous theory, however, was based on chemiluminescence imaging, which is a line-of-sight integrated technique. In this work, we use high-speed laser-induced fluorescence to further investigate instability suppression in two staging configurations: center-nozzle and outer-nozzle staging. An edge-tracking algorithm is used to compute local flame edge displacement as a function of time, allowing instability-driven edge oscillation phase coherence and other instantaneous flame dynamics to be spectrally and spatially resolved. Analysis of flame edge oscillations shows the presence of convecting coherent fluctuations of the flame edge caused by periodic vortex shedding. When the system is unstable, these two flame edges oscillate together as a result of high-intensity longitudinal-mode acoustic oscillations in the combustor that drive periodic vortex shedding at each of the nozzle exits. In the stable cases, however, the phase between the oscillations of the center and outer flame edges is greater than 90 deg (∼114 deg), suggesting that the phase-cancelation hypothesis may be valid. This analysis allows a better understanding of the instantaneous flame dynamics behind flame edge oscillation phase offset and fuel staging-based instability suppression.

scholarly journals CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method

2021 ◽  
Vol 11 (9) ◽  
pp. 3934
Author(s):  
Federico Lluesma-Rodríguez ◽  
Temoatzin González ◽  
Sergio Hoyas
Keyword(s):  
Shock Waves ◽  
Power Consumption ◽  
High Speed ◽  
Cfd Simulation ◽  
Aerodynamic Drag ◽  
Flow Behavior ◽  
Critical Conditions ◽  
Vehicle Speed ◽  
Blockage Ratio ◽  
The Cost

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

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