Experimental and Computational Analyses of Methane and Hydrogen Mixing in a Model Premixer

2010 ◽  
Author(s):  
Amin Akbari ◽  
Scott Hill ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Schmidt Number ◽  
Fuel Injection ◽  
Agricultural Waste ◽  
Cross Flow ◽  
Flux Ratio ◽  
Turbulence Models ◽  
Systematic Evaluation ◽  
Efficient Design ◽  
Efficient Manner ◽  
Turbulent Schmidt Number

The mixing of fuel and air in combustion systems plays a key role in overall operability and emissions performance. Such systems are also being looked to for operation on a wide array of potential fuel types, including those derived from renewable sources such as biomass or agricultural waste. The optimization of premixers for such systems is greatly enhanced if efficient design tools can be utilized. The increased capability of computational systems has allowed tools such as computational fluid dynamics to be regularly used for such purpose. However, to be applied with confidence, validation is required. In the present work, a systematic evaluation of fuel mixing in a specific geometry which entails cross flow fuel injection into axial non-swirling air streams has been carried out for methane and hydrogen. Fuel concentration is measured at different planes downstream of the point of injection. In parallel, different CFD approaches are used to predict the concentration fields resulting from the mixing of fuel and air. Different steady turbulence models including variants of Reynolds Averaged Navier Stokes (RANS) have been applied. In addition, unsteady RANS and Large Eddy Simulation (LES) are used. To accomplish mass transport with any of the RANS approaches, the concept of the turbulent Schmidt number is generally used. As a result, the sensitivity of the RANS simulations to different turbulent Schmidt number values is also examined. In general, the results show that the Reynolds Stress Model, with use of an appropriate turbulent Schmidt number for the fuel used, provides the best agreement with the measured values of the variation in fuel distribution over a given plane in a relatively time efficient manner. It is also found that, for a fixed momentum flux ratio, both hydrogen and methane penetrate and disperse in a similar manner for the flowfield studied despite their significant differences in density and diffusivity.

Experimental and Computational Analyses of Methane and Hydrogen Mixing in a Model Premixer

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Amin Akbari ◽  
Scott Hill ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Schmidt Number ◽  
Fuel Injection ◽  
Agricultural Waste ◽  
Flux Ratio ◽  
Systematic Evaluation ◽  
Efficient Design ◽  
Efficient Manner ◽  
Turbulent Schmidt Number

The mixing of fuel and air in combustion systems plays a key role in overall operability and emissions performance. Such systems are also being looked to for operation on a wide array of potential fuel types, including those derived from renewable sources such as biomass or agricultural waste. The optimization of premixers for such systems is greatly enhanced if efficient design tools can be utilized. The increased capability of computational systems has allowed tools such as computational fluid dynamics to be regularly used for such purpose. However, to be applied with confidence, validation is required. In the present work, a systematic evaluation of fuel mixing in a specific geometry, which entails cross flow fuel injection into axial nonswirling air streams has been carried out for methane and hydrogen. Fuel concentration is measured at different planes downstream of the point of injection. In parallel, different computational fluid dynamics approaches are used to predict the concentration fields resulting from the mixing of fuel and air. Different steady turbulence models including variants of Reynolds averaged Navier–Stokes (RANS) have been applied. In addition, unsteady RANS and large eddy simulation are used. To accomplish mass transport with any of the RANS approaches, the concept of the turbulent Schmidt number is generally used. As a result, the sensitivity of the RANS simulations to different turbulent Schmidt number values is also examined. In general, the results show that the Reynolds stress model, with use of an appropriate turbulent Schmidt number for the fuel used, provides the best agreement with the measured values of the variation in fuel distribution over a given plane in a relatively time efficient manner. It is also found that, for a fixed momentum flux ratio, both hydrogen and methane penetrate and disperse in a similar manner for the flow field studied despite their significant differences in density and diffusivity.

Statistical Evaluation of CFD Predictions of Measured Mixing Properties of Hydrogen and Methane for Lean Premixed Combustion

2011 ◽  
Author(s):  
Amin Akbari ◽  
Scott Hill ◽  
Vincent McDonell ◽  
Scott Samuelsen
Keyword(s):  
Fuel Injection ◽  
Turbulence Models ◽  
Numerical Results ◽  
Community Research ◽  
Systematic Evaluation ◽  
Design Matrix ◽  
Injection Point ◽  
Mixing Properties ◽  
Lean Combustion ◽  
Turbulent Schmidt Number

Hydrogen is a fuel of interest to the combustion community research as a promising sustainable alternative fuel to replace fossil fuels. The combustion of hydrogen produces only emission of water vapor and NOx. To alleviate the NOx emission, lean combustion has been proposed and utilized in last three decades for natural gas. Therefore, evaluation of mixing properties of both methane and hydrogen in lean combustion technology such as premixers is crucial for design purposes. Increased capability of computational systems has allowed tools such as computational fluid dynamics to be regularly used for purpose of design screening. In the present work, systematic evaluation of different CFD approaches is accomplished for axial injection of fuel into non swirling air. The study has been undertaken for both methane and hydrogen. Different Reynolds Averaged Navier Stokes (RANS) turbulence models including k–ε and RSM, which are relatively attractive as being computationally efficient, are evaluated. Further, the sensitivity of RANS models to different turbulent Schmidt number (Sct), as an important parameter in mass transport analysis, has been investigated. To evaluate the numerical results, fuel concentration is measured in different locations downstream of the injection point. This is accomplished by means of flame ionization detector (FID). Finally, a comprehensive comparison has been made between numerical and experimental results to identify the best numerical approach. To provide quantitative assessment, the simulations follow a statistically design matrix which allows analysis of variance to be used to identify the preferred simulation strategies. The results suggest high sensitivity of numerical results to different Sct and relatively low sensitivity to turbulence models. However, this general trend is the opposite for radial fuel injection.

CFD Predictions of Isothermal Fuel-Air Mixing in a Radial Swirl Low NOx Combustor Using Various RANS Turbulence Models

2012 ◽  
Author(s):  
Phil T. King ◽  
Gordon E. Andrews ◽  
Mohamed M. Pourkashanian ◽  
Andy C. McIntosh
Keyword(s):  
Fuel Injection ◽  
Turbulence Models ◽  
Problem Area ◽  
Combustion Modeling ◽  
Fuel Jet ◽  
Turbulent Schmidt Number ◽  
Air Mixing ◽  
Rans Turbulence Models ◽  
Reasonable Prediction ◽  
Future Work

A radial swirl DLE combustion system was investigated for its gaseous fuel-air mixing performance using various different RANS turbulence models. Two different configurations were investigated; vane passage fuel injection and fuel injection from the wall of an outlet throat directly into the shear layer. The results showed that for vane passage fuel injection, only the standard k-ε and standard Spalart-Allmaras models were able to provide a reasonable prediction for the combustor fuel-air distribution, out of all the RANS models and their variants available in Fluent v6.3, although both models predicted that the fuel and air were better mixed than in the measurements. For outlet throat wall fuel injection no models were able to provide a reasonable prediction. This same issue is also reported by several other researchers and represents a serious problem area in combustion modeling for low NOx applications. Improved fuel jet penetration was achieved by using an extremely low value of 0.1 for the turbulent Schmidt number, therefore future work will concentrate on using a localized value of Sc in the vicinity of the fuel injection hole.

CFD Modeling of the Atomization of Plain Liquid Jets in Cross Flow for Gas Turbine Applications

2004 ◽  
Author(s):  
Sachin Khosla ◽  
D. Scott Crocker
Keyword(s):  
Momentum Flux ◽  
Drop Size ◽  
Fuel Injection ◽  
Cross Flow ◽  
Flux Ratio ◽  
Wake Flow ◽  
Cfd Modeling ◽  
Liquid Jets ◽  
Momentum Flux Ratio ◽  
Primary Breakup

A numerical model for liquid jet atomization in a subsonic gas cross flow has been developed and incorporated into a CFD code. The model is designed primarily for the shear breakup regime, which is appropriate for many fuel injection applications. The model considers Weber number and momentum flux ratio ranges that are dominated by either jet surface breakup or column breakup. A boundary layer stripping model has been modified to account for both shearing from the column and shear primary breakup of large drops. Further secondary breakup was modeled with the Rayleigh-Taylor model. The effect of drop distortion on the drag is also considered. Results of the model have been compared with experimental data for jet-A liquid jets in air cross flows with varying pressure, air velocity, and liquid-to-gas momentum flux ratio. Comparisons were made for drop volume flux and drop size as a function of distance from the injector wall. Trends were captured for liquid penetration associated with varying momentum flux ratio, and for drop size as a function distance from the wall. In general, agreement between measurements and CFD predictions were quite good. Areas of disagreement could be reasonably explained by the model’s inherent inability to capture the wake flow behind the liquid column.

Sprays in Cross Flow: Dependence on Weber Number

2007 ◽  
Author(s):  
Eugene Lubarsky ◽  
Jonathan R. Reichel ◽  
Ben T. Zinn ◽  
Rob McAmis
Keyword(s):  
Weber Number ◽  
Momentum Flux ◽  
Fuel Injection ◽  
Flow Direction ◽  
Air Flow ◽  
Cross Flow ◽  
Flux Ratio ◽  
Elevated Pressure ◽  
Momentum Flux Ratio ◽  
Breakup Mechanism

This paper describes an experimental investigation of the spray created by Jet A fuel injection from a plate containing sharp edged orifice 0.018 inches (457 μm) in diameter and L/D ratio of 10 into the crossflow of preheated air (555 K) at elevated pressure in the test section (4 ata) and liquid to air momentum-flux ratio of 40. A 2 component Phase Doppler Particle Analyzer used for measuring the characteristics of the spray. The Weber number of the spray in crossflow was varied between 33 and 2020 and the effect of Weber number on spray properties was investigated. It was seen that shear breakup mechanism dominates at Weber number greater than about 100. Droplets’ diameters were found to be in the range of 15-30 microns for higher values of Weber numbers, while larger droplets (100-200 microns) were observed at Weber number of 33. Larger droplets were observed at the periphery of the spray. The droplet velocities and diameters were measured in a plane 30mm downstream of the orifice along the centerline of the spray at an incoming air flow Mach number of 0.2 and liquid to air momentum-flux ratio of 40. The droplets reach a maximum of 90% of the flow velocity at this location. The velocity of droplets in the directions perpendicular to the air flow direction is higher at the periphery of the spray possibly due to the presence of larger droplets. The RMS values of the droplet velocities are highest slightly off center of the centerline of the spray showing the presence of strong vortices formed due to the liquid jet in crossflow. The data presented here could serve as benchmark data for CFD code validation.

scholarly journals Experimental and Computational Studies of Turbulent Mass Transfer in a Mixing Channel

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Lene K. Hjertager Osenbroch ◽  
Bjorn H. Hjertager ◽  
Tron Solberg
Keyword(s):  
Mass Transfer ◽  
Schmidt Number ◽  
Turbulence Models ◽  
Computational Studies ◽  
Square Channel ◽  
Numerical Predictions ◽  
Turbulent Schmidt Number ◽  
Passive Mixing ◽  
Local Mean ◽  
Presumed Pdf

Experiments are carried out for passive mixing in order to obtain local mean and turbulent velocities and concentrations. The mixing takes place in a square channel with two inlets separated by a block. A combined PIV/PLIF technique is used to obtain instantaneous velocity and concentration fields. Three different flow cases are studied. The 2D numerical predictions of the mixing channel show that none of the k - ? turbulence models tested is suitable for the flow cases studied here. The turbulent Schmidt number is reduced to obtain a better agreement between the measured and predicted mean and fluctuating concentrations. The multi-peak presumed PDF mixing model is tested and comparisons with experiments are encouraging.

CFD Prediction of the Trajectory of Hot Exhaust from the Funnel of a Naval Ship in the Presence of Ship Superstructure

2014 ◽  
Vol 156 (A1) ◽  
Keyword(s):  
Temperature Field ◽  
Schmidt Number ◽  
Cfd Simulation ◽  
Cross Flow ◽  
Design Stage ◽  
Trajectory Prediction ◽  
Turbulent Schmidt Number ◽  
Mandatory Requirement ◽  
Naval Ship ◽  
The Many

The superstructure of a modern naval ship is fitted with multitude of sensors for electronic surveillance, weapon discharge, navigation, communication and varieties of deck handling equipment. Locating these electronic equipment/sensors and its integration on board is of paramount importance to achieve optimal operational performance of the naval vessel. Among the many problems in locating these sensors (like stability, EMC EMI etc.,), the presence of entrapped hot gases from the ship exhaust affects the functioning of these electronics. Hence the prediction of temperature profile and trajectories of the ship exhaust plume from the funnel around the superstructure during the design stage is a mandatory requirement for positioning the sensors on superstructure. This trajectory prediction is not amenable to theoretical analysis or empirical calculation procedures in the modern warship superstructure. Experimental and CFD studies conducted on ship superstructure are the only reliable tools that are available to estimate temperature field as well as to study the exhaust smoke superstructure interaction on ships. This paper presents the CFD simulation of the published results for two cases, namely hot jet in a cross flow and hot exhaust with a cross flow on a generic frigate. Simulations have been made using k-ɛ turbulence model with different values of turbulent Schmidt number. It has been observed that temperature field is predicted with reasonable accuracy with turbulent Schmidt number of 0.2.

CFD PREDICTION OF THE TRAJECTORY OF HOT EXHAUST FROM THE FUNNEL OF A NAVAL SHIP IN THE PRESENCE OF SHIP SUPERSTRUCTURE

2021 ◽  
Vol 156 (A1) ◽  
Author(s):  
R Vijayakumar ◽  
S N Singh ◽  
V Seshadri
Keyword(s):  
Temperature Field ◽  
Schmidt Number ◽  
Cfd Simulation ◽  
Cross Flow ◽  
Design Stage ◽  
Trajectory Prediction ◽  
Turbulent Schmidt Number ◽  
Mandatory Requirement ◽  
Naval Ship ◽  
The Many

The superstructure of a modern naval ship is fitted with multitude of sensors for electronic surveillance, weapon discharge, navigation, communication and varieties of deck handling equipment. Locating these electronic equipment/sensors and its integration on board is of paramount importance to achieve optimal operational performance of the naval vessel. Among the many problems in locating these sensors (like stability, EMC EMI etc.,), the presence of entrapped hot gases from the ship exhaust affects the functioning of these electronics. Hence the prediction of temperature profile and trajectories of the ship exhaust plume from the funnel around the superstructure during the design stage is a mandatory requirement for positioning the sensors on superstructure. This trajectory prediction is not amenable to theoretical analysis or empirical calculation procedures in the modern warship superstructure. Experimental and CFD studies conducted on ship superstructure are the only reliable tools that are available to estimate temperature field as well as to study the exhaust smoke superstructure interaction on ships. This paper presents the CFD simulation of the published results for two cases, namely hot jet in a cross flow and hot exhaust with a cross flow on a generic frigate. Simulations have been made using k-ɛ turbulence model with different values of turbulent Schmidt number. It has been observed that temperature field is predicted with reasonable accuracy with turbulent Schmidt number of 0.2.

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