Fuel Nozzle Aerodynamic Design Using CFD Analysis

1997 ◽  
Vol 119 (3) ◽  
pp. 527-534 ◽  
Author(s):  
D. S. Crocker ◽  
E. J. Fuller ◽  
C. E. Smith
Keyword(s):  
Fuel Injection ◽  
Swirling Flow ◽  
Turbulence Models ◽  
Cfd Analysis ◽  
Aerodynamic Design ◽  
Flow Area ◽  
Measured Velocity ◽  
Fuel Nozzle ◽  
Cfd Analyses ◽  
Good Agreement

The aerodynamic design of airflow passages in fuel injection systems can be significantly enhanced by the use of CFD analysis. Attempts to improve the efficiency of the fuel nozzle design process by using CFD analyses have generally been unsuccessful in the past due to the difficulties of modeling swirling flow in complex geometries. Some of the issues that have been obstacles to successful and timely analysis of fuel nozzle aerodynamics include grid generation, turbulence models, and definition of boundary conditions. This study attempts to address these obstacles and demonstrate a CFD methodology capable of modeling swirling flow within the internal air passages of fuel nozzles. The CFD code CFD-ACE was used for the analyses. Results of nonreacting analyses and comparison with experimental data are presented for three different fuel nozzles. The three nozzles have distinctly different designs (including axial and radial inflow swirlers) and thus demonstrate the flexibility of the design methodology. Particular emphasis is given to techniques involved in predicting the effective flow area (ACd) of the nozzles. Good agreement between CFD predictions of the ACd (made prior to experiments) and the measured ACd was obtained. Comparisons between predicted and measured velocity profiles also showed good agreement.

scholarly journals Fuel Nozzle Aerodynamic Design Using CFD Analysis

1996 ◽  
Author(s):  
D. Scott Crocker ◽  
Eric J. Fuller ◽  
Clifford E. Smith
Keyword(s):  
Fuel Injection ◽  
Swirling Flow ◽  
Turbulence Models ◽  
Cfd Analysis ◽  
Aerodynamic Design ◽  
Flow Area ◽  
Measured Velocity ◽  
Fuel Nozzle ◽  
Cfd Analyses ◽  
Good Agreement

The aerodynamic design of airflow passages in fuel injection systems can be significantly enhanced by the use of CFD analysis. Attempts to improve the efficiency of the fuel nozzle design process by using CFD analyses have generally been unsuccessful in the past due to the difficulties of modeling swirling flow in complex geometries. Some of the issues that have been obstacles to successful and timely analysis of fuel nozzle aerodynamics include grid generation, turbulence models, and definition of boundary conditions. This study attempts to address these obstacles and demonstrate a CFD methodology capable of modeling swirling flow within the internal air passages of fuel nozzles. The CFD code CFD-ACE was used for the analyses. Results of non-reacting analyses and comparison with experimental data are presented for three different fuel nozzles. The three nozzles have distinctly different designs (including axial and radial inflow swirlers) and thus demonstrate the flexibility of the design methodology. Particular emphasis is given to techniques involved in predicting the effective flow area (ACd) of the nozzles. Good agreement between CFD predictions of the ACd (made prior to experiments) and the measured ACd was obtained. Comparisons between predicted and measured velocity profiles also showed good agreement.

Passive Control of Combustion Instability in Lean Premixed Combustors

1999 ◽  
Author(s):  
Robert C. Steele ◽  
Luke H. Cowell ◽  
Steven M. Cannon ◽  
Clifford E. Smith
Keyword(s):  
Passive Control ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Time Lag ◽  
Stable Configuration ◽  
Cfd Analysis ◽  
Fuel Injector ◽  
Pressure Oscillations ◽  
Excessive Pressure ◽  
Lean Premixed

A Solar fuel injector that provides lean premixed combustion conditions has been studied in a combined experimental and numerical investigation. Lean premixed conditions can be accompanied by excessive combustion driven pressure oscillations which must be eliminated before the release of a final combustor design. In order to eliminate the pressure oscillations the location of fuel injection was parametrically evaluated to determine a stable configuration. It was observed that small axial changes in the position of the fuel spokes within the premix duct of the fuel injector had a significant positive effect on decoupling the excitation of the natural acoustic modes of the combustion system. In order to further understand the phenomenon, a time-accurate 2D CFD analysis was performed. 2D analysis was first calibrated using 3D steady-state CFD computations of the premixer in order to model the radial distribution of velocities in the pre mixer caused by non-uniform inlet conditions and swirling flow. 2D time-accurate calculations were then performed on the baseline configuration. The calculations captured the coupling of heat release with the combustor acoustics, which resulted in excessive pressure oscillations. When the axial location of the fuel injection was moved, the CFD analysis accurately captured the fuel time lag to the flame-front, and qualitatively matched the experimental findings.

CFD Analysis of Gear Windage Losses: Validation and Parametric Aerodynamic Studies

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Matthew J. Hill ◽  
Robert F. Kunz ◽  
Richard B. Medvitz ◽  
Robert F. Handschuh ◽  
Lyle N. Long ◽  
...  
Keyword(s):  
Experimental Data ◽  
Spur Gear ◽  
Mitigation Strategies ◽  
Test Facility ◽  
Cfd Analysis ◽  
Physical Mechanisms ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method ◽  
Cfd Analyses ◽  
Good Agreement

A computational fluid dynamics (CFD) method has been applied to gear configurations with and without shrouding. The goals of this work have been to validate the numerical and modeling approaches used for these applications and to develop physical understanding of the aerodynamics of gear windage loss. Several spur gear geometries are considered, for which experimental data are available. Various canonical shrouding configurations and free spinning (no shroud) cases are studied. Comparisons are made with experimental data from open literature, and data recently obtained in the NASA Glenn Research Center Gear Windage Test Facility, Cleveland, OH. The results show good agreement with the experiment. The parametric shroud configuration studies carried out in the Glenn experiments and the CFD analyses elucidate the physical mechanisms of windage losses as well as mitigation strategies due to shrouding and newly proposed tooth contour modifications.

CFD Modeling of Combustion Instability in Premixed Axisymmetric Combustors

1997 ◽  
Author(s):  
Clifford E. Smith ◽  
Andy D. Leonard
Keyword(s):  
Combustion Instability ◽  
Combustion Products ◽  
Cfd Modeling ◽  
Cfd Analysis ◽  
Fuel Injector ◽  
Air Velocity ◽  
Flow Area ◽  
Exhaust Duct ◽  
Fuel Nozzle ◽  
Unstable Case

Time-accurate CFD analysis is used to model combustion instability in a premixed axisymmetric combustor typical of industrial gas turbine engines. The experiment of Richards and Janus (1997) is modeled; the hardware consists of a fuel injector similar to industrial premix fuel nozzles, a water-cooled can combustor, an uncooled refractory plug that reduces flow area, and a long exhaust duct. The CFD calculation domain extends from the air swirler within the fuel nozzle to the exhaust duct exit. Two cases are modeled using 2D time-accurate axisymmetric CFD analysis: a low nozzle air velocity (u = 30 m/s) case that exhibits combustion instability and a high nozzle air velocity (u = 60 m/s) case that does not. The CFD analysis agrees well with the experimental measurements, including peak-to-peak pressure variation and instability frequency for the unstable case. For the unstable case, the airflow through the swirler actually flows upstream part of the time, and hot combustion products are forced into the premix annulus. The potential of using a time-accurate CFD approach for modeling combustion instability in complex 3D combustors is discussed.

Passive Control of Combustion Instability in Lean Premixed Combustors

2000 ◽  
Vol 122 (3) ◽  
pp. 412-419 ◽  
Author(s):  
Robert C. Steele ◽  
Luke H. Cowell ◽  
Steven M. Cannon ◽  
Clifford E. Smith
Keyword(s):  
Passive Control ◽  
Fuel Injection ◽  
Swirling Flow ◽  
Time Lag ◽  
Stable Configuration ◽  
Cfd Analysis ◽  
Fuel Injector ◽  
Pressure Oscillations ◽  
Excessive Pressure ◽  
Lean Premixed

A Solar fuel injector that provides lean premixed combustion conditions has been studied in a combined experimental and numerical investigation. Lean premixed conditions can be accompanied by excessive combustion driven pressure oscillations which must be eliminated before the release of a final combustor design. In order to eliminate the pressure oscillations the location of fuel injection was parametrically evaluated to determine a stable configuration. It was observed that small axial changes in the position of the fuel spokes within the premix duct of the fuel injector had a significant positive effect on decoupling the excitation of the natural acoustic modes of the combustion system. In order to further understand the phenomenon, a time-accurate 2D CFD analysis was performed. 2D analysis was first calibrated using 3D steady-state CFD computations of the premixer in order to model the radial distribution of velocities in the premixer caused by non-uniform inlet conditions and swirling flow. 2D time-accurate calculations were then performed on the baseline configuration. The calculations captured the coupling of heat release with the combustor acoustics, which resulted in excessive pressure oscillations. When the axial location of the fuel injection was moved, the CFD analysis accurately captured the fuel time lag to the flame-front, and qualitatively matched the experimental findings. [S0742-4795(00)01103-0]

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

scholarly journals Numerical and experimental study on turbulence statistics in a large fan-stirred combustion vessel

2021 ◽  
Vol 62 (5) ◽  
Author(s):  
M. E. Morsy ◽  
J. Yang
Keyword(s):  
Isotropic Turbulence ◽  
Burning Velocity ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Initial Pressure ◽  
Dynamics Modeling ◽  
Turbulence Statistics ◽  
Experimental Conditions ◽  
Measured Velocity

Abstract Particle image velocimetry (PIV) has become a popular non-intrusive tool for measuring various types of flows. However, when measuring three-dimensional flows with two-dimensional (2D) PIV, there are some uncertainties in the measured velocity field due to out-of-plane motion, which might alter turbulence statistics and distort the overall flow characteristics. In the present study, three different turbulence models are employed and compared. Mean and fluctuating fields obtained by three-dimensional computational fluid dynamics modeling are compared to experimental data. Turbulence statistics such as integral length scale, Taylor microscale, Kolmogorov scale, turbulence kinetic energy, dissipation rate, and velocity correlations are calculated at different experimental conditions (i.e., pressure, temperature, fan speed, etc.). A reasonably isotropic and homogeneous turbulence with large turbulence intensities is achieved in the central region extending to almost 45 mm radius. This radius decreases with increasing the initial pressure. The influence of the third dimension velocity component on the measured characteristics is negligible. This is a result of the axisymmetric features of the flow pattern in the current vessel. The results prove that the present vessel can be conveniently adopted for several turbulent combustion studies including mainly the determination of turbulent burning velocity for gaseous premixed flames in nearly homogeneous isotropic turbulence. Graphic abstract

Computational Investigation of Different Turbulent Models When Predicting Airflow in an Enclosure

2008 ◽  
Author(s):  
Xi Wang ◽  
Hassan Naji ◽  
Ahmed Mezrhab
Keyword(s):  
Numerical Investigation ◽  
Turbulence Models ◽  
Turbulent Stress ◽  
Computational Investigation ◽  
Isothermal Case ◽  
The Mean ◽  
Turbulent Models ◽  
Rsm Model ◽  
Cold Case ◽  
Good Agreement

In the present study, a numerical investigation is carried out for an isothermal case, a hot case and a cold case with FLUENT code. Three turbulence models are considered: the k-ε realisable model, the RNG k-ε model and the RSM linear model. The obtained results are compared to experiments and show generally a good agreement for the mean velocities and temperatures, but less satisfactory for the turbulent stress. The performance of the RSM model is remarkable. Even if none of the models is able to give the exact experimental pattern on the map of turbulence, the RSM model seems able to predict such configuration.

Study of the Change of Performance of an Elastic Vertical Hydrofoil With Deformation

2014 ◽  
Author(s):  
Alexander Führing ◽  
Subha Kumpaty ◽  
Chris Stack
Keyword(s):  
Water Flow ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Turbulence Models ◽  
Flow Property ◽  
Performance Data ◽  
Cfd Analysis ◽  
Ansys Fluent ◽  
Drag Forces ◽  
Fluid Flow Analysis

In external and internal fluid flow analysis using numerical methods, most attention is paid to the properties of the flow assuming absolute rigidity of the solid bodies involved. However, this is often not the case for water flow or other fluids with high density. The pressure forces cause the geometry to deform which in turn changes the flow properties around it. Thus, a one-way and two-way Fluid-Structure Interaction (FSI) coupling is proposed and compared to a CFD analysis of a windsurfing fin in order to quantify the differences in performance data as well as the properties of the flow. This leads to information about the necessity of the use of FSI in comparison to regular CFD analysis and gives indication of the value of the enhanced results of the deformable analysis applied to water flow around an elastically deformable hydrofoil under different angles of attack. The performance data and flow property evaluation is done in ANSYS Fluent using the k-ω SST and k-ε model with a y+ of 1 and 35 respectively in order to be able to compare the behavior of both turbulence models. It is found that the overall lift coefficient in general is lower and that the flow is less turbulent because of softer transition due to the deformed geometry reducing drag forces. It is also found that the deformation of the tip of the hydrofoil leads to vertical lift forces. For the FSI analysis, one-way and two-way coupling were incorporated leading to the ability to compare results. It has been found that one-way coupling is sufficient as long as there is no stall present at any time.

Flow Characteristics of Transitional Boundary Layers on an Airfoil in Wakes

2000 ◽  
Vol 122 (3) ◽  
pp. 522-532 ◽  
Author(s):  
H. Lee ◽  
S.-H. Kang
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Skin Friction ◽  
Velocity Fluctuation ◽  
Plate Boundary ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Transitional Region ◽  
Mean Velocity ◽  
Measured Velocity

Transition characteristics of a boundary layer on a NACA0012 airfoil are investigated by measuring unsteady velocity using hot wire anemometry. The airfoil is installed in the incoming wake generated by an airfoil aligned in tandem with zero angle of attack. Reynolds number based on the airfoil chord varies from 2.0×105 to 6.0×105; distance between two airfoils varies from 0.25 to 1.0 of the chord length. To measure skin friction coefficient identifying the transition onset and completion, an extended wall law is devised to accommodate transitional flows with pressure gradient and nonuniform inflows. Variations of the skin friction are quite similar to that of the flat plate boundary layer in the uniform turbulent inflow of high intensity. Measured velocity profiles are coincident with families generated by the modified wall law in the range up to y+=40. Turbulence intensity of the incoming wake shifts the onset location of transition upstream. The transitional region becomes longer as the airfoils approach one another and the Reynolds number increases. The mean velocity profile gradually varies from a laminar to logarithmic one during the transition. The maximum values of rms velocity fluctuations are located near y+=15-20. A strong positive skewness of velocity fluctuation is observed at the onset of transition and the overall rms level of velocity fluctuation reaches 3.0–3.5 in wall units. The database obtained will be useful in developing and evaluating turbulence models and computational schemes for transitional boundary layer. [S0098-2202(00)01603-5]

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