Spark Ignition Simulations and the Generation of Ignition Maps by Means of a Turbulent Flame Speed Closure Approach

2010 ◽  
Author(s):  
Jan M. Boyde ◽  
Massimiliano Di Domenico ◽  
Berthold Noll ◽  
Manfred Aigner
Keyword(s):  
Turbulent Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Test Case ◽  
Ignition Energy ◽  
Mean Flow ◽  
Flame Kernel ◽  
Turbulent Flame Speed ◽  
Flow Parameters ◽  
Partially Premixed

This paper presents a numerical investigation of ignition phenomena in turbulent partially premixed methane/air flames. In this work, a turbulent flame speed closure model (TFC) is employed with an ignition delay module extension. The model is applied to two partially premixed test cases under standard conditions in the configuration of a shearless flame and a counter flow flame, respectively. For both setups, the flame kernel propagation and consequent establishment or extinction of the flame are examined. A shearless configuration represents the first test case under investigation. The study demonstrates the large influence of the mean flow parameters on achieving a successful ignition of the domain. The second test case under examination is a counterflow geometry. A sensitivity analysis with respect to spark ignition position and ignition energy is performed. The simulations show that flame kernel spreading is largely influenced by the magnitude of turbulence occurring in the flow, leading to an enhanced propagation in areas with a moderate turbulence degree, whereas high turbulence can be detrimental for the flame establishment due to extensive heat losses. Another observation is that a successful ignition of the domain can occur, even in cases in which the ignition energy is not placed in an area with flammable mixture. The comparison with experimental data shows a good agreement, both in terms of successful ignition and flame kernel propagation.

G-equation based ignition model for direct injection spark ignition engines

2021 ◽  
pp. 146808742110139
Author(s):  
Arun C Ravindran ◽  
Sage L Kokjohn ◽  
Benjamin Petersen
Keyword(s):  
Heat Release ◽  
Direct Injection ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Discharge Process ◽  
Flame Kernel ◽  
Turbulent Flame Speed ◽  
Direct Injection Spark Ignition ◽  
Kernel Growth ◽  
Spark Energy

To accurately model the Direct Injection Spark Ignition (DISI) combustion process, it is important to account for the effects of the spark energy discharge process. The proximity of the injected fuel spray and spark electrodes leads to steep gradients in local velocities and equivalence ratios, particularly under cold-start conditions when multiple injection strategies are employed. The variations in the local properties at the spark plug location play a significant role in the growth of the initial flame kernel established by the spark and its subsequent evolution into a turbulent flame. In the present work, an ignition model is presented that is compatible with the G-Equation combustion model, which responds to the effects of spark energy discharge and the associated plasma expansion effects. The model is referred to as the Plasma Velocity on G-surface (PVG) model, and it uses the G-surface to capture the early kernel growth. The model derives its theory from the Discrete Particle Ignition (DPIK) model, which accounts for the effects of electrode heat transfer, spark energy, and chemical heat release from the fuel on the early flame kernel growth. The local turbulent flame speed has been calculated based on the instantaneous location of the flame kernel on the Borghi-Peters regime diagram. The model has been validated against the experimental measurements given by Maly and Vogel,1 and the constant volume flame growth measurements provided by Nwagwe et al.2 Multi-cycle simulations were performed in CONVERGE3 using the PVG ignition model in combination with the G-Equation-based GLR4 model in a RANS framework to capture the combustion characteristics of a DISI engine. Good agreements with the experimental pressure trace and apparent heat-release rates were obtained. Additionally, the PVG ignition model was observed to substantially reduce the sensitivity of the default G-sourcing ignition method employed by CONVERGE.

Impact of Fuel Properties and Flame Stretch on the Turbulent Flame Speed in Spark-Ignition Engines

2013 ◽  
Author(s):  
Pierre Brequigny ◽  
Christine Mounaïm-Rousselle ◽  
Fabien Halter ◽  
Bruno Moreau ◽  
Thomas Dubois
Keyword(s):  
Turbulent Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Fuel Properties ◽  
Spark Ignition Engines ◽  
Turbulent Flame Speed ◽  
Flame Stretch

Measurements of Stretch Statistics at Flame Leading Points for High Hydrogen Content Fuels

2014 ◽  
Author(s):  
Andrew Marshall ◽  
Julia Lundrigan ◽  
Prabhakar Venkateswaran ◽  
Jerry Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Flame Front ◽  
Hydrogen Content ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Composition ◽  
Mean Flow ◽  
Tangential Strain ◽  
High Hydrogen ◽  
High Hydrogen Content ◽  
Turbulent Flame Speed

Fuel composition has a strong influence on the turbulent flame speed, even at very high turbulence intensities. An important implication of this result is that the turbulent flame speed cannot be extrapolated from one fuel to the next using only the laminar flame speed and turbulence intensity as scaling variables. This paper presents curvature and tangential strain rate statistics of premixed turbulent flames for high hydrogen content fuels. Global (unconditioned) stretch statistics are presented as well as measurements conditioned on the leading points of the flame front. These measurements are motivated by previous experimental and theoretical work that suggests the turbulent flame speed is controlled by the flame front characteristics at these points. The data were acquired with high speed particle image velocimetry (PIV) in a low swirl burner (LSB). We attained measurements for several H2:CO mixtures over a range of mean flow velocities and turbulence intensities. The results show that fuel composition has a systematic, yet weak effect on curvatures and tangential strain rates at the leading points. Instead, stretch statistics at the leading points are more strongly influenced by mean flow velocity and turbulence level. It has been argued that the increased turbulent flame speeds seen with increasing hydrogen content are the result of increasing flame stretch rates, and therefore SL,max values, at the flame leading points. However, the differences observed with changing fuel compositions are not significant enough to support this hypothesis. Additional analysis is needed to understand the physical mechanisms through which the turbulent flame speed is altered by fuel composition effects.

scholarly journals A MEAN VALUE MODEL FOR ESTIMATION OF LAMINAR AND TURBULENT FLAME SPEED IN SPARK-IGNITION ENGINE

2015 ◽  
Vol 11 ◽  
pp. 2224-2234 ◽  
Author(s):  
Ali Ghanaati ◽  
◽  
Intan Z. Mat Darus ◽  
Mohd Farid Muhamad Said ◽  
Amin Mahmoudzadeh Andwari ◽  
...  
Keyword(s):  
Turbulent Flame ◽  
Spark Ignition ◽  
Mean Value ◽  
Flame Speed ◽  
Spark Ignition Engine ◽  
Turbulent Flame Speed ◽  
Mean Value Model ◽  
Value Model

Effects of Hydrogen Addition on the Flame Speeds of Natural Gas Blends Under Uniform Turbulent Conditions

2015 ◽  
Author(s):  
S. Ravi ◽  
A. Morones ◽  
E. L. Petersen ◽  
F. Güthe
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Mean Flow ◽  
Hydrogen Addition ◽  
Turbulent Flame Speed ◽  
Preferential Diffusion ◽  
Wide Range ◽  
H2 Addition

Natural gas is the primary fuel for stationary, powergeneration gas turbines, and it is necessary to understand its combustion characteristics under engine-relevant (turbulent) conditions. Since its composition varies depending on the fuel source, a natural gas surrogate (NG 18% C2+) and admixtures with H2 have been utilized recently by the authors to aid chemical kinetics modeling using ignition delay times and laminar flame speed experiments. The present study focused on measuring turbulent flame speeds (displacement speeds) of natural gas (NG2) and methane with H2 using a fan-stirred flame bomb. The apparatus is a closed, cylindrical chamber fitted with four radial impellers that generate a central spherical volume of homogeneous and isotropic turbulence with negligible mean flow. Schlieren imaging was used to visually track the growth of the spherically expanding turbulent kernels during the constant-pressure period. The turbulence levels were fixed at an average RMS intensity level of 1.5 m/s and at an integral length scale of 27 mm. Turbulent flame speeds (ST,0.1) of NG2 blends were measured over a wide range of equivalence ratios between 0.7 and 1.3. ST,0.1 for the natural gas surrogate closely matched with those of methane for near-stoichiometric mixtures. However, preferential-diffusion effects (fuel effects) were observed under turbulent conditions for off-stoichiometric cases. The effects of hydrogen addition on the turbulent flame speeds of NG2 (25/75 and 50/50 (by volume) blends of H2/NG2) were also investigated and were compared with the flame speeds reported in a recent paper by the authors (ASME GT2014-26742) on the effects of hydrogen addition to turbulent flame speeds of methane. The effect of the hydrogen addition was to increase the turbulent flame speed (by about a factor of two for 50% H2 addition), although this effect was much more pronounced for the lean and stoichiometric mixtures. Interestingly, the flame speeds (both laminar and turbulent) of the CH4 blends with H2 were slightly larger than those for the NG2 blend at equivalent conditions, or about 10–20% larger at 50% H2 addition. This behavior can be explained kinetically by the increased importance of the inhibiting reaction CH3 + H (+M) ↔ CH4 (+M), where ethane oxidation produces more CH3 radicals than methane at similar conditions.

Turbulent Consumption Speed Scaling of H2/CO Blends

2011 ◽  
Author(s):  
Prabhakar Venkateswaran ◽  
Andrew D. Marshall ◽  
David R. Noble ◽  
Jerry M. Seitzman ◽  
Tim C. Lieuwen
Keyword(s):  
Laminar Flame ◽  
Turbulent Flame ◽  
Practical Interest ◽  
Flame Speed ◽  
Fuel Composition ◽  
Laminar Flame Speed ◽  
Volume Data ◽  
Mean Flow ◽  
Turbulent Flame Speed ◽  
Kinetic Calculations

This paper describes measurements and analysis of global turbulent consumption speeds, ST,GC, of hydrogen/carbon monoxide (H2/CO) mixtures. The turbulent flame properties of such mixtures are of fundamental interest because of their strong stretch sensitivity and of practical interest since they are the primary constituents of syngas fuels. Data are analyzed at mean flow velocities and turbulence intensities of 4 < U0 < 50 m/s and 1 < u′rms/SL,0 < 100, respectively, for H2/CO blends ranging from 30–90% H2 by volume. Data from two sets of experiments are reported. In the first, fuel blends ranging from 30–90% H2 and mixture equivalence ratio, Φ, were adjusted at each fuel composition to have nominally the same un-stretched laminar flame speed, SL,0. In the second set, equivalence ratios were varied at constant H2 levels. The data clearly corroborate results from other studies that show significant sensitivity of ST,GC to fuel composition. For example, at a fixed u′rms, ST,GC of a 90% H2 case (at Φ = 0.48) is a factor of three times larger than the baseline Φ = 0.9, CH4/air mixture that has the same SL,0 value. We also describe physics-based correlations of these data, using leading points concepts and detailed kinetic calculations of their stretch sensitivities. These results are used to develop an inequality for negative Markstein length flames that bounds the turbulent flame speed data and show that the data can be collapsed using the maximum stretched laminar flame speed, SL,max, rather than SL,0.

Measurements of Stretch Statistics at Flame Leading Points for High Hydrogen Content Fuels

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Andrew Marshall ◽  
Julia Lundrigan ◽  
Prabhakar Venkateswaran ◽  
Jerry Seitzman ◽  
Tim Lieuwen
Keyword(s):  
Flame Front ◽  
Hydrogen Content ◽  
Turbulent Flame ◽  
Flame Speed ◽  
Fuel Composition ◽  
Mean Flow ◽  
Tangential Strain ◽  
High Hydrogen ◽  
High Hydrogen Content ◽  
Turbulent Flame Speed

Fuel composition has a strong influence on the turbulent flame speed, even at very high turbulence intensities. An important implication of this result is that the turbulent flame speed cannot be extrapolated from one fuel to the next using only the laminar flame speed and turbulence intensity as scaling variables. This paper presents curvature and tangential strain rate statistics of premixed turbulent flames for high hydrogen content (HHC) fuels. Global (unconditioned) stretch statistics are presented as well as measurements conditioned on the leading points of the flame front. These measurements are motivated by previous experimental and theoretical work that suggests the turbulent flame speed is controlled by the flame front characteristics at these points. The data were acquired with high-speed particle image velocimetry (PIV) in a low-swirl burner (LSB). We attained measurements for several H2:CO mixtures over a range of mean flow velocities and turbulence intensities. The results show that fuel composition has a systematic, yet weak effect on curvatures and tangential strain rates at the leading points. Instead, stretch statistics at the leading points are more strongly influenced by mean flow velocity and turbulence level. It has been argued that the increased turbulent flame speeds seen with increasing hydrogen content are the result of increasing flame stretch rates, and therefore, SL,max values, at the flame leading points. However, the differences observed with changing fuel compositions are not significant enough to support this hypothesis. Additional analysis is needed to understand the physical mechanisms through which the turbulent flame speed is altered by fuel composition effects.

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