Design of Turbulent Flame Aerosol Reactors by Mixing-Limited Fluid Dynamics

2011 ◽  
Vol 50 (6) ◽  
pp. 3159-3168 ◽  
Author(s):  
Arto J. Gröhn ◽  
Beat Buesser ◽  
Jorma K. Jokiniemi ◽  
Sotiris E. Pratsinis
Keyword(s):  
Fluid Dynamics ◽  
Turbulent Flame ◽  
Aerosol Reactors

Reactive computational fluid dynamics modelling of methane–hydrogen admixtures in internal combustion engines: Part I – RANS

2020 ◽  
pp. 146808742091638
Author(s):  
Jann Koch ◽  
Christian Schürch ◽  
Yuri M Wright ◽  
Konstantinos Boulouchos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Internal Combustion Engines ◽  
Turbulent Flame ◽  
Internal Combustion ◽  
Flame Speed ◽  
Combustion Engines ◽  
Hydrogen Addition ◽  
Dynamics Modelling ◽  
Modelling Approach

The effects of hydrogen addition to internal combustion engines operated by natural gas/methane has been widely demonstrated experimentally in the literature. Already small hydrogen contents in the fuel show promising benefits with respect to increased engine efficiency, lower CO2 emissions, extended lean operating limits and a higher exhaust gas recirculation tolerance while maintaining the knock resistance of methane. In this article, the influence of hydrogen addition to methane on a spark ignited single cylinder engine is investigated. This article proposes a modelling approach to consider hydrogen addition within three-dimensional reactive computational fluid dynamics in order to establish a framework to gain further insights into the involved processes. Experiments have been performed on a single-cylinder spark-ignition engine situated at a test bed and cater as reference data for validating the proposed reactive computational fluid dynamics modelling approach based around the G-Equation combustion model. Within the course of the first part, crucial aspects relevant to the modelling of the mean engine cycle are highlighted. In this article, a simplified early combustion phase model which considers the transition towards a fully developed turbulent flame following ignition is introduced, along with a second submodel considering combined effects of the walls. The sensitivity of the combustion process towards the modelling approach is presented. The submodels were calibrated for a reference operating point, and a sweep in hydrogen content in the fuel as well as stoichiometric and lean operation has been considered. It is shown that the flame speed coefficient A appearing in the used turbulent flame speed closure, weighting the influence of the turbulent fluctuating speed [Formula: see text], has to be adjusted for different hydrogen contents. The introduced submodels allowed for significant improvement of the in-cylinder pressure and heat release rate evolution throughout all considered operating conditions.

Accelerating Computational Fluid Dynamics Simulations of Engine Knock Using a Concurrent Cycles Approach

2020 ◽  
Author(s):  
Daniel Probst ◽  
Sameera Wijeyakulasuriya ◽  
Pinaki Pal ◽  
Christopher Kolodziej ◽  
Eric Pomraning
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Direct Injection ◽  
Turbulent Flame ◽  
Sampling Rate ◽  
Operating Conditions ◽  
Gasoline Direct Injection ◽  
Simulation Data ◽  
Low Frequencies ◽  
Operating Points

Abstract Knock is a major design challenge for spark-ignited engines. Knock constrains high load operation and limits efficiency gains that can be achieved by implementing higher compression ratios. The propensity to knock depends on the interaction among fuel properties, engine geometry, and operating conditions. Moreover, cycle-to-cycle variability (CCV) in knock intensity is commonly encountered under abnormal combustion conditions. In this situation, knock needs to be assessed with multiple engine cycles. Therefore, when using computational fluid dynamics (CFD) to predict knock behavior, multi-cycle simulations must be performed. The wall clock time for simulating multiple consecutive engine cycles is prohibitive, especially for a statistically valid sample size (i.e. 30–100 cycles). In this work, 3-d CFD simulations were used to model knocking phenomena in the cooperative fuel research (CFR) engine. Unsteady Reynolds-Averaged Navier Stokes (uRANS) simulations were performed with a hybrid combustion modeling approach using the G-equation method to track the turbulent flame front and finite-rate chemistry model to predict end-gas autoignition. To circumvent the high cost of running simulations with a large number of consecutive engine cycles, a concurrent perturbation method (CPM) was evaluated to predict knock CCV. The CPM was based on previous work by the authors, in which concurrent engine cycles were used to predict engine CCV in a non-knocking gasoline direct injection (GDI) engine. Concurrent cycles were initialized by perturbing a saved flow field with a random isotropic velocity field. By initializing each cycle with a perturbation sufficiently early in the cycle, each case yields a distinct and valid prediction of combustion due to the chaotic nature of the system. Three operating points were simulated, with different spark timings corresponding to heavy knock, light knock, and no knock. For all the operating points, other conditions were based on the standard research octane number (RON) test specification for iso-octane. The spark timing of the heavy knock case was the same as that of the RON test. The in-cylinder pressure fluctuations were isolated using a frequency filtering method. A bandpass filter was applied to eliminate high and low frequencies. The knocking pressures were calculated consistently between the experimental and simulation data, including the sampling frequency of the data. The simulation data was sampled to match the sampling rate of the experimental data. The knock intensities were compared for the concurrently obtained cycles, the consecutively obtained cycles, and experimental cycles. Knock predictions from the concurrent and consecutive simulations compared well to each other and with experiments, thereby demonstrating the validity of the CPM approach.

Three-dimensional computational fluid dynamics simulation of hydrogen engines using a turbulent flame speed closure combustion model

2012 ◽  
Vol 13 (5) ◽  
pp. 464-481 ◽  
Author(s):  
Udo Gerke ◽  
Konstantinos Boulouchos
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Three Dimensional ◽  
Flame Speed ◽  
Combustion Model ◽  
Laminar Flame Speed ◽  
Release Rates ◽  
Turbulent Flame Speed

The mixture formation and combustion process of a hydrogen direct-injection internal combustion engine is computed using a modified version of a commercial three-dimensional computational fluid dynamics code. The aim of the work is the evaluation of hydrogen laminar flame speed correlations and turbulent flame speed closures with respect to combustion of premixed and stratified mixtures at various levels of air-to-fuel equivalence ratio. Heat-release rates derived from in-cylinder pressure traces are used for the validation of the combustion simulations. A turbulent combustion model with closures for a turbulent flame speed is investigated. The value of the computed heat-release rates mainly depends on the quality of laminar burning velocities and standard of turbulence quantities provided to the combustion model. Combustion simulations performed with experimentally derived laminar flame speed data give better results than those using laminar flame speeds obtained from a kinetic scheme. However, experimental data of hydrogen laminar flame speeds found in the literature are limited regarding the range of pressures, temperatures and air-to-fuel equivalence ratios, and do not comply with the demand of high-pressure engine-relevant conditions.

scholarly journals Simulation of Hydrogen-Air-Diluents Mixture Combustion in an Acceleration Tube with FlameFoam Solver

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5504
Author(s):  
Mantas Povilaitis ◽  
Justina Jaseliūnaitė
Keyword(s):  
Fluid Dynamics ◽  
Flame Propagation ◽  
Turbulent Combustion ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Turbulence Models ◽  
Dynamics Simulation ◽  
Severe Accident ◽  
Variable Model ◽  
Sst Model

During a severe accident in a nuclear power plant, hydrogen can be generated, leading to risks of possible deflagration and containment integrity failure. To manage severe accidents, great experimental, analytical, and benchmarking efforts are being made to understand combustible gas distribution, deflagration, and detonation processes. In one of the benchmarks—SARNET H2—flame acceleration due to obstacle-induced turbulence was investigated in the ENACCEF facility. The turbulent combustion problem is overly complex because it involves coupling between fluid dynamics, mass/heat transfer, and chemistry. There are still unknowns in understanding the mechanisms of turbulent flame propagation, therefore many methods in interpreting combustion and turbulent speed are present. Based on SARNET H2 benchmark results, a two-dimensional computational fluid dynamics simulation of turbulent hydrogen flame propagation in the ENACCEF facility was performed. Four combustible mixtures with different diluents concentrations were considered—13% H2 and 0%/10%/20%/30% of diluents in air. The aim of this numerical simulation was to validate the custom-built turbulent combustion OpenFOAM solver based on the progress variable model—flameFoam. Furthermore, another objective was to perform parametric analysis in relation to turbulent speed correlations and turbulence models and interpret the k-ω SST model blending function F1 behavior during the combustion process. The obtained results show that in the simulated case all three turbulent speed correlations behave similarly and can be used to reproduce observable flame speed; also, the k-ε model provides more accurate results than the k-ω SST turbulence model. It is shown in the paper that the k-ω SST model misinterprets the sudden parameter gradients resulting from turbulent combustion.

Numerical study of combustion characteristics and emissions of a diesel–methane dual-fuel engine for a wide range of injection timings

2018 ◽  
Vol 21 (5) ◽  
pp. 781-793 ◽  
Author(s):  
Xingyi (Hunter) Dai ◽  
Satbir Singh ◽  
Sundar R Krishnan ◽  
Kalyan K Srinivasan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Release ◽  
Combustion Chamber ◽  
Heat Release Rate ◽  
Diesel Fuel ◽  
Release Rate ◽  
Turbulent Flame ◽  
Dual Fuel ◽  
Model Predictions

Computational fluid dynamics simulations are performed to investigate the combustion and emission characteristics of a diesel/natural gas dual-fuel engine. The computational fluid dynamics model is validated against experimental measurements of cylinder pressure, heat release rate, and exhaust emissions from a single-cylinder research engine. The model predictions of in-cylinder diesel spray distribution and location of diesel ignition sites are related to the behavior observed in measured and predicted heat release rate and emissions. Various distributions of diesel fuel inside the combustion chamber are obtained by modifying the diesel injection timing and the spray included angle. Model predictions suggest that the distribution of diesel fuel in the combustion chamber has a significant impact on the characteristics of heat release rate, explaining experimental observations. Regimes of combustion in the dual-fuel engine are identified. Turbulent flame speed calculations, premixed turbulent combustion regime diagram analysis, and high-temperature front propagation speed estimation indicated that the dual-fuel combustion in this engine was supported by successive local auto-ignition and not by turbulent flame propagation.

Generalized Riemann Problems in Computational Fluid Dynamics

2003 ◽  
Author(s):  
Matania Ben-Artzi ◽  
Joseph Falcovitz
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Riemann Problems ◽  
Generalized Riemann Problems

Computational Fluid Dynamics

2002 ◽  
Author(s):  
T. J. Chung
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics

Partial Differential Equations in Fluid Dynamics

2008 ◽  
Author(s):  
Isom H. Herron ◽  
Michael R. Foster
Keyword(s):  
Fluid Dynamics ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Partial Differential

An Introduction to Fluid Dynamics

2000 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Fluid Dynamics

A First Course in Fluid Dynamics

1983 ◽  
Author(s):  
A. R. Paterson
Keyword(s):  
Fluid Dynamics
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