Assessment of Scale Resolved CFD Methods for the Investigation of Lean Burn Spray Flames

2016 ◽  
Author(s):  
A. Andreini ◽  
D. Bertini ◽  
L. Mazzei ◽  
S. Puggelli
Keyword(s):  
Steady State ◽  
Numerical Models ◽  
Combustion Model ◽  
Experimental Investigations ◽  
Strong Impact ◽  
Lean Burn ◽  
Two Phase ◽  
Spray Flames ◽  
Flamelet Generated Manifold ◽  
Reactive Processes

Incoming standards on NOx emissions are motivating many aero-engines manufacturers to adopt the lean burn combustion concept. However, several technological issues have to be faced in this transition, among which limited availability of air for cooling purpose and thermoacoustics phenomena that should be managed to safely implement this burning mode. In this scenario, standard numerical design tools are not often capable of characterizing such devices. Thus, considering also the difficulties of experimental investigations in a highly pressurized and reactive environment, unsteady scale resolved CFD methods are required to correctly understand the combustor performances. In the last years Large Eddy (LES) and hybrid RANS-LES models such as Scale Adaptive Simulations (SAS) have undergone considerable developments. Such approaches have been already applied for gaseous flames, leading to a strong enhancement in phenomena prediction with respect to standard steady-state simulations. However, huge research efforts are still required when spray flames are considered, since all the numerical models chosen to describe spray dynamics and the related reactive processes can have a strong impact on the accuracy of the whole simulation. In this work a set of scale resolved simulations have been carried out on the DLR Generic Single Sector Combustor spray flame for which measurements both in non-reactive and reactive test conditions are available. Exploiting a two-phase Eulerian-Lagrangian approach combined with a Flamelet Generated Manifold (FGM) combustion model, LES simulations have been performed in order to assess the potential improvements with respect to steady state solutions. Additional comparisons have also been accomplished with SAS calculations based on Eddy Dissipation combustion model (EDM). The comparison with experimental results shows that the chosen unsteady strategies lead to a more physical description of reactive processes with respect to RANS simulations. FGM model showed some limitations in reproducing the partially-premixed nature of the flame, whereas SAS-EDM proved to be a robust modelling strategy within an industrial perspective. A new set of spray boundary conditions for liquid injection is also proposed whose realiability is proved through a detailed comparison against experimental data.

Assessment of Scale-Resolved Computational Fluid Dynamics Methods for the Investigation of Lean Burn Spray Flames

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Stefano Puggelli ◽  
Davide Bertini ◽  
Lorenzo Mazzei ◽  
Antonio Andreini
Keyword(s):  
Detailed Comparison ◽  
Navier Stokes ◽  
Combustion Model ◽  
Experimental Investigations ◽  
Lean Burn ◽  
Two Phase ◽  
Physical Description ◽  
Spray Flames ◽  
Flamelet Generated Manifold ◽  
Modeling Strategy

Incoming standards on NOx emissions are motivating many aero-engines manufacturers to adopt the lean burn combustion concept. However, several technological issues have to be faced in this transition, among which limited availability of air for cooling purpose and thermoacoustics phenomena. In this scenario, standard numerical design tools are not often capable of characterizing such devices. Thus, considering also the difficulties of experimental investigations in a highly pressurized and reactive environment, unsteady scale-resolved CFD methods are required to correctly understand the combustor performances. In this work, a set of scale-resolved simulations have been carried out on the Deutsches Zentrum für Luft- und Raumfahrt (DLR) generic single-sector combustor spray flame for which measurements both in nonreactive and reactive test conditions are available. Exploiting a two-phase Eulerian–Lagrangian approach combined with a flamelet generated manifold (FGM) combustion model, LES simulations have been performed in order to assess the potential improvements with respect to steady-state solutions. Additional comparisons have also been accomplished with scale-adaptive simulation (SAS) calculations based on eddy dissipation combustion model (EDM). The comparison with experimental results shows that the chosen unsteady strategies lead to a more physical description of reactive processes with respect to Reynolds-averaged Navier–Stokes (RANS) simulations. FGM model showed some limitations in reproducing the partially premixed nature of the flame, whereas SAS–EDM proved to be a robust modeling strategy within an industrial perspective. A new set of spray boundary conditions for liquid injection is also proposed whose reliability is proved through a detailed comparison against experimental data.

Development and validation of a novel quasi-dimensional combustion model for un-scavenged prechamber gas engines with numerical simulations and engine experiments

2020 ◽  
pp. 146808742095133 ◽  
Author(s):  
Konstantinos Bardis ◽  
Panagiotis Kyrtatos ◽  
Guoqing Xu ◽  
Christophe Barro ◽  
Yuri Martin Wright ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Design Parameters ◽  
Combustion Model ◽  
Experimental Investigations ◽  
Computationally Efficient ◽  
Lean Burn ◽  
Dimensional Models ◽  
Three Dimensional Models

Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters.

Spray Flames Simulation Using a Two Phase Combustion Model With Single Droplet Combustion Mode

2012 ◽  
Author(s):  
F. Wang ◽  
Y. Huang
Keyword(s):  
Droplet Diameter ◽  
Navier Stokes ◽  
Combustion Model ◽  
Droplet Combustion ◽  
Single Droplet ◽  
Two Phase ◽  
Spray Flame ◽  
Spray Flames ◽  
The Individual ◽  
Individual Droplet

There are three combustion regimes of individual droplet combustion behavior: the fully enveloped flame, the partially enveloped flame, and the wake flame. From PLIF measurement results, single droplet combustion phenomenon happens in spray flame, as well as lean type gas turbine combustion chamber sometimes. The drag coefficient, evaporation rate, and combustion rate are different according to the burning modes. At present, in Reynolds Averaged Navier Stokes (RANS) method and Large Eddy Simulation (LES) method, the droplets are treated as point source because the grid scale is bigger than the droplet diameter. A two phase combustion model with the consideration of the individual droplet burning mode is proposed before. In this paper, this model is tested by spray flames here again. Furthermore, this model was used in a concept lean premixed pre-vaporized (LPP) combustion case too. In spray flame, the predicted results are close to the experimental data.

Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Emissions

2018 ◽  
Author(s):  
L. Mazzei ◽  
S. Puggelli ◽  
D. Bertini ◽  
A. Andreini ◽  
B. Facchini ◽  
...  
Keyword(s):  
Combustion Process ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Combustion Model ◽  
Flame Spray ◽  
Lean Burn ◽  
Flamelet Generated Manifold ◽  
Nozzle Guide ◽  
Nozzle Guide Vanes ◽  
The Impact

Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NOx and soot in particular). Its implementation however involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. Also the conditions at the combustor exit are a concern, as high turbulence, residual swirl and the impossibility to adjust the temperature profile with dilution holes determine a harsher environment for nozzle guide vanes. This work describes the final stages of the design of an aeronautical effusion-cooled lean burn combustor. Full annular tests were carried out to measure temperature profiles and emissions (CO and NOx) at the combustor exit. Different operating conditions of the ICAO cycle were tested, considering Idle, Cruise, Approach and Take-Off. Scale-adaptive simulations with the Flamelet Generated Manifold combustion model were performed to extend the validation of the employed CFD methodology and to reproduce the experimental data in terms of RTDF/OTDF profiles as well as emission indexes. The satisfactory agreement paved the way to an exploitation of the methodology to provide a deeper understanding of the flow physics within the combustion chamber, highlighting the impact of the different operating conditions on flame, spray evolution and pollutant formation.

Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors

2000 ◽  
Vol 123 (4) ◽  
pp. 817-823 ◽  
Author(s):  
G. Klose ◽  
R. Schmehl ◽  
R. Meier ◽  
G. Maier ◽  
R. Koch ◽  
...  
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Numerical Models ◽  
Computational Method ◽  
Phase Model ◽  
Combustion Model ◽  
Phase Flow ◽  
Two Phase ◽  
Low Emission ◽  
Good Agreement

The development of low-emission aero-engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows. In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an eddy dissipation (ED) and a presumed-shape-PDF (JPDF) combustion model. The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.

Numerical Techniques Applied to Hydraulic Turbines: A Perspective Review

2016 ◽  
Vol 68 (1) ◽  
Author(s):  
Chirag Trivedi ◽  
Michel J. Cervantes ◽  
Ole Gunnar Dahlhaug
Keyword(s):  
Steady State ◽  
Numerical Models ◽  
Guide Vane ◽  
Numerical Technique ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Numerical Techniques ◽  
Transient Conditions ◽  
Hydraulic Turbines

Applications of computational fluid dynamic (CFD) techniques to hydropower have increased rapidly in the last three decades. The majority of the experimental investigations of hydraulic turbines were supported by numerical studies and this has become a standard practice. In the paper, applied numerical techniques and flow modeling approaches to simulate the hydraulic turbines are discussed. Both steady-state and transient operating conditions of the turbines are considered for the review. The steady-state conditions include the best efficiency point (BEP), high load (HL), and part load (PL). The transient conditions include load variation, startup, shutdown, and total load rejection. The performance of the applied numerical models and turbulence modeling with respect to the operating conditions are discussed. The recently developed numerical technique (transient blade row modeling) using the Fourier transformation (FT) method is discussed. This technique allows guide vane and blade passages to be modeled with the pitch ratio other than unity. Numerical modeling and simulation of hydraulic turbines during the transient operating conditions is one of the most challenging tasks because guide vanes' angular movement is time-dependent and mesh should be dynamic/moving. Different approaches applied to simulate the transient conditions and their limitations are discussed. Overall, this review summarizes the role of numerical techniques, advantages, limitations, and upcoming challenges within hydropower.

scholarly journals Dynamical and technological consequences of multiple isolas of steady states in a catalytic fluidised-bed reactor

2017 ◽  
Vol 38 (3) ◽  
pp. 411-422
Author(s):  
Katarzyna Bizon
Keyword(s):  
Steady State ◽  
Quantitative Description ◽  
Product Yield ◽  
Steady States ◽  
Strong Impact ◽  
Fluidised Bed ◽  
Two Phase ◽  
Medium Temperature ◽  
Fluidised Bed Reactor ◽  
The Impact

Abstract Steady-state characteristics of a catalytic fluidised bed reactor and its dynamical consequences are analyzed. The occurrence of an untypical steady-state structure manifesting in a form of multiple isolas is described. A two-phase bubbling bed model is used for a quantitative description of the bed of catalyst. The influence of heat exchange intensity and a fluidisation ratio onto the generation of isolated solution branches is presented for two kinetic schemes. Dynamical consequences of the coexistence of such untypical branches of steady states are presented. The impact of linear growth of the fluidisation ratio and step change of the cooling medium temperature onto the desired product yield is analyzed. The results presented in this study confirm that the identification of a region of the occurrence of multiple isolas is important due to their strong impact both on the process start-up and its control.

Evaluation of Advanced Two-Phase Flow and Combustion Models for Predicting Low Emission Combustors

2000 ◽  
Author(s):  
G. Klose ◽  
R. Schmehl ◽  
R. Meier ◽  
G. Meier ◽  
R. Koch ◽  
...  
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Numerical Models ◽  
Computational Method ◽  
Phase Model ◽  
Combustion Model ◽  
Phase Flow ◽  
Two Phase ◽  
Low Emission ◽  
Good Agreement

The development of low emission aero engine combustors strongly depends on the availability of accurate and efficient numerical models. The prediction of the interaction between two-phase flow and chemical combustion is one of the major objectives of the simulation of combustor flows. In this paper, predictions of a swirl stabilized model combustor are compared to experimental data. The computational method is based on an Eulerian two-phase model in conjunction with an Eddy Dissipation (ED) and a presumed-shape-PDF (JPDF) combustion model. The combination of an Eulerian two-phase model with a JPDF combustion model is a novelty. It was found to give good agreement to the experimental data.

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