scholarly journals Numerical Investigation of the Impact of H2 Enrichment on Lean Biogas/Air Flames: An Analytical Modelling Approach

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 369
Author(s):  
Filipe M. Quintino ◽  
Edgar C. Fernandes
Keyword(s):  
Laminar Flame ◽  
A Priori ◽  
Kinetic Mechanism ◽  
Laminar Flame Speed ◽  
Independent Variables ◽  
New Correlation ◽  
Dilution Effects ◽  
The Impact ◽  
Good Agreement ◽  
Modelling Approach

The transition from natural gas to renewable gases such as biogas and hydrogen creates an interchangeability challenge. The laminar flame speed SL is a critical parameter in appliance design as it is a unique characteristic of the flame mixture. It is thus essential to evaluate the impact of renewable gases on SL. In this work, 1D simulations were conducted in Cantera with the USC-Mech 2.0 kinetic mechanism. The SL of three base biogas blends (BG100, BG90 and BG80) was computed for H2 enrichment up to 50% in volume, equivalence ratio 0.8≤ϕ≤1.0, p=1 atm and Tu=298 K. It was found that the effect of H2 enrichment is higher for base blends with higher CO2 content as the thermal-diffusive and dilution effects of carbon dioxide are mitigated by hydrogen. The introduction of H2 also increases the H radical pool, which is linked with the increase in SL. A new correlation to model the impact of H2 enrichment, SL(xH2)=ζ(ϕ)/SL′(xCO2)xH2exH2+SL′(xCO2), is proposed, which exhibits good agreement with the literature data and simulations. This equation can be directly used to estimate SL without the need for a priori adaptations of fit parameters as the contributions of CO2 and H2 are isolated in independent variables.

Study of Fuel Composition, Burner Material and Tip Temperature Effects on Flashback of Enclosed Jet Flame

2013 ◽  
Author(s):  
Zhixuan Duan ◽  
Brendan Shaffer ◽  
Vincent McDonell
Keyword(s):  
Laminar Flame ◽  
Specific Effect ◽  
Premixed Combustion ◽  
Heat Transfer Analysis ◽  
Fuel Composition ◽  
Laminar Flame Speed ◽  
High Hydrogen ◽  
Jet Flame ◽  
Multiple Parameters ◽  
The Impact

Flashback is a key challenge for low NOx premixed combustion of high hydrogen content fuels. Previous work has systematically investigated the impact of fuel composition on flashback propensity, and noted that burner tip temperature played an important role on flashback, yet did not quantify any specific effect. The present work further investigates the coupling of flashback with burner tip temperature and leads to models for flashback propensity as a function of parameters studied. To achieve this, a jet burner configuration with interchangeable burner materials was developed along with automated flashback detection and rim temperature monitoring. An inline heater provides preheated air up to 810 K. Key observations include that for a given condition, tip temperature of a quartz burner at flashback is higher than that of a stainless burner. As a reasult, the flashback propensity of a quartz tube is about double of that of a stainless tube. A polynomial model based on analysis of variance is presented and shows that, if the tip temperature is introduced as a parameter, better correlations result. A physical model is developed and illustates that the critical velocity gradient is proportional to the laminar flame speed computed using the measured tip temperature. Addition of multiple parameters further refined the prediction of the flashback propensity, and the effects of materials are discussed qualitatively using a simple heat transfer analysis.

An Experimental and Modeling Study of Laminar Flame Speeds of Alternative Aviation Fuels

2011 ◽  
Author(s):  
Thomas Kick ◽  
Trupti Kathrotia ◽  
Marina Braun-Unkhoff ◽  
Uwe Riedel
Keyword(s):  
Laminar Flame ◽  
Cone Angle ◽  
Reaction Model ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Alternative Aviation Fuels ◽  
Predicted Values ◽  
Angle Method ◽  
Eu Project ◽  
Good Agreement

The present work reports on measurements of burning velocities of synthetic fuel air mixtures exploiting the cone-angle method, as part of the EU project ALFA-BIRD. The GtL (Gas-to-Liquid)-air mixtures — (i) 100% GtL and (ii) GtL+20% hexanol, respectively — were studied at atmospheric pressure, with values of the equivalence ratio φ ranging between φ ∼ 1.0 and φ ∼ 1.3, at preheat temperatures To = 423 K (GtL+20% hexanol) as well as To = 473 K (for 100% GtL and GtL+20% hexanol). A comparison between experimentally obtained burning velocities and predicted values of laminar flame speed is presented, too. In general, good agreement was found between predicted and measured data for the range of conditions considered in the present study. The predictive capability of the detailed reaction model consisting of 3479 reactions involving 490 species will be discussed focusing on the laminar flame speed and the combustion of the components (n-decane, iso-octane, and 1-hexanol) of the surrogate used.

Skeletal Mechanism for C2H4 Combustion With PAH Formation

2008 ◽  
Author(s):  
N. Slavinskaya ◽  
A. Zizin ◽  
M. Braun-Unkhoff ◽  
C. Lenfers
Keyword(s):  
Experimental Data ◽  
Laminar Flame ◽  
Polyaromatic Hydrocarbons ◽  
Kinetic Mechanism ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Skeletal Model ◽  
Temporal Profiles ◽  
Detailed Kinetic Mechanism ◽  
Good Agreement

A semi-detailed kinetic mechanism with 100 species and 816 reactions for ethylene combustion including PAH formation was elaborated. The model includes the C2H5OH sub mechanism combustion as well. This mechanism has in view to be the base of further kinetic schemes of practical fuels (reference fuels). The mechanism was reduced to a skeletal model with 72 species and 580 reactions. The elaborated models were validated on experimental data bases of heat release as well as formation of polyaromatic hydrocarbons and soot in laminar premixed C2H4, C2H4 / C2H5OH flames taken from literature. The calculated ignition delay times, laminar flame speeds, as well as temporal profiles of small and large aromatics and also soot particles are in good agreement with experimental data obtained for pressures 1 – 5 bar, temperatures T0 = 1100 – 2300 K, fuel/oxygen equivalence ratio φ = 0.5 – 2.

scholarly journals The Mainz profile algorithm (MAPA)

2019 ◽  
Vol 12 (3) ◽  
pp. 1785-1806 ◽  
Author(s):  
Steffen Beirle ◽  
Steffen Dörner ◽  
Sebastian Donner ◽  
Julia Remmers ◽  
Yang Wang ◽  
...  
Keyword(s):  
A Priori ◽  
Scaling Factor ◽  
Least Square ◽  
Trace Gas ◽  
Vertical Profiles ◽  
Mixing Ratios ◽  
Surface Mixing ◽  
Sensitivity Studies ◽  
The Impact ◽  
Good Agreement

Abstract. The Mainz profile algorithm (MAPA) derives vertical profiles of aerosol extinction and trace gas concentrations from MAX-DOAS measurements of slant column densities under multiple elevation angles. This paper presents (a) a detailed description of the MAPA (v0.98), (b) results for the CINDI-2 campaign, and (c) sensitivity studies on the impact of a priori assumptions such as flag thresholds. Like previous profile retrieval schemes developed at MPIC, MAPA is based on a profile parameterization combining box profiles, which also might be lifted, and exponential profiles. But in contrast to previous inversion schemes based on least-square fits, MAPA follows a Monte Carlo approach for deriving those profile parameters yielding best match to the MAX-DOAS observations. This is much faster and directly provides physically meaningful distributions of profile parameters. In addition, MAPA includes an elaborated flagging scheme for the identification of questionable or dubious results. The AODs derived with MAPA for the CINDI-2 campaign show good agreement with AERONET if a scaling factor of 0.8 is applied for O4, and the respective NO2 and HCHO surface mixing ratios match those derived from coincident long-path DOAS measurements. MAPA results are robust with respect to modifications of the a priori MAPA settings within plausible limits.

Temporal instability modes of supersonic round jets

2010 ◽  
Vol 662 ◽  
pp. 173-196 ◽  
Author(s):  
LUIS PARRAS ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
A Priori ◽  
Temporal Stability ◽  
Jet Noise ◽  
Base Flow ◽  
Round Jets ◽  
Instability Modes ◽  
Theoretical Predictions ◽  
Mode Characteristics ◽  
The Impact ◽  
Good Agreement

In this study, a comprehensive inviscid temporal stability analysis of a compressible round jet is performed for Mach numbers ranging from 1 to 10. We show that in addition to the Kelvin–Helmholtz instability modes, there exist for each azimuthal wavenumber three other types of modes (counterflow subsonic waves, subsonic waves and supersonic waves) whose characteristics are analysed in detail using a WKBJ theory in the limit of large axial wavenumber. The theory is constructed for any velocity and temperature profile. It provides the phase velocity and the spatial structure of the modes and describes qualitatively the effects of base-flow modifications on the mode characteristics. The theoretical predictions are compared with numerical results obtained for an hyperbolic tangent model and a good agreement is demonstrated. The results are also discussed in the context of jet noise. We show how the theory can be used to determine a priori the impact of jet modifications on the noise induced by instability.

A Detailed and Reduced Reaction Mechanism of Biomass-Based Syngas Fuels

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Marina Braun-Unkhoff ◽  
Nadezhda Slavinskaya ◽  
Manfred Aigner
Keyword(s):  
Reaction Mechanism ◽  
Laminar Flame ◽  
Chemical Kinetic ◽  
Laminar Flame Speed ◽  
Predictive Capability ◽  
Kinetic Reaction ◽  
Auto Ignition ◽  
Combustion Properties ◽  
Detailed Chemical ◽  
Good Agreement

In the present work, the elaboration of a reduced kinetic reaction mechanism is described, which predicts reliably fundamental characteristic combustion properties of two biogenic gas mixtures consisting mainly of hydrogen, methane, and carbon monoxide, with small amounts of higher hydrocarbons (ethane and propane) in different proportions. From the in-house detailed chemical kinetic reaction mechanism with about 55 species and 460 reactions, a reduced kinetic reaction mechanism was constructed consisting of 27 species and 130 reactions. Their predictive capability concerning laminar flame speed (measured at T0=323 K, 373 K, and 453 K, at p=1 bar, 3 bars, and 6 bars for equivalence ratios φ between 0.6 and 2.2) and auto ignition data (measured in a shock tube between 1035 K and 1365 K at pressures around 16 bars for φ=0.5 and 1.0) are discussed in detail. Good agreement was found between experimental and calculated values within the investigated parameter range.

Estimating Laminar Flame Speed and Ignition Delay for a Series of Natural Gas Mixtures at IC Engine-Relevant Conditions

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Kelsey Fieseler ◽  
Taylor Linker ◽  
Mark Patterson ◽  
Daniel Rem ◽  
Timothy J. Jacobs
Keyword(s):  
Natural Gas ◽  
Ignition Delay ◽  
Laminar Flame ◽  
Initial Conditions ◽  
Initial Pressure ◽  
Fuel Mixture ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Ic Engine ◽  
The Impact

Abstract Two equations are developed to estimate laminar flame speed and ignition delay for different alkane mixtures at a range of engine-relevant conditions. Fuel mixtures of methane, ethane, propane, butane, and pentane were selected by analyzing the natural gas composition in a natural gas pipeline located in the Midwestern United States. The laminar flame speed and ignition delay were calculated for each mixture at each set of conditions using Cantera, a chemical kinetics solver. The range of initial conditions for laminar flame speed includes temperatures from 300 to 700 K, pressures from 1 to 40 bar, equivalence ratios from 0.4 to 1.2, and residual fractions from 0% to 20%. These data were then fit to a non-linear regression. The range of initial conditions for the ignition delay equation includes temperatures from 1100 to 2000 K, pressures from 1 to 40 bar, equivalence ratios from 0.4 to 1.15, and residual fractions from 0% to 20%. These data were fit to a previously developed equation. Sensitivity studies were conducted on each equation to quantify the impact of the independent variables on the target variable. This showed that, for laminar flame speed, the initial pressure, temperature, and equivalence ratio had the largest impact, with fuel composition having a lesser impact. For ignition delay, the temperature and pressure were shown to have the largest impact. There is a room for improvement, namely, increasing the fuel mixture variability and range of initial conditions, and developing a better fit to the data.

Prediction of Ultra-Lean Spark Ignition Engine Performances by Quasi-Dimensional Combustion Model With a Refined Laminar Flame Speed Correlation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Ratnak Sok ◽  
Kyohei Yamaguchi ◽  
Jin Kusaka
Keyword(s):  
Gasoline Engine ◽  
Laminar Flame ◽  
Flame Speed ◽  
Spark Ignition Engine ◽  
Combustion Model ◽  
Laminar Flame Speed ◽  
Gasoline Engines ◽  
Indicated Mean Effective Pressure ◽  
Constant Volume Chamber ◽  
Good Agreement

Abstract The turbulent combustion in gasoline engines is highly dependent on laminar flame speed SL. A major issue of the quasi-dimensional (QD) combustion model is an accurate prediction of the SL, which is unstable under low engine speeds and ultra-lean mixture. This work investigates the applicability of the combustion model with a refined SL correlation for evaluating the combustion characteristics of a high-tumble port gasoline engine operated under ultra-lean mixtures. The SL correlation is modified and validated for a five-component gasoline surrogate. Predicted SL values from the conventional and refined functions are compared with measurements taken from a constant-volume chamber under micro-gravity conditions. The SL data are measured at reference and elevated conditions. The results show that the conventional SL overpredicts the flame speeds under all conditions. Moreover, the conventional model predicts negative SL at equivalence ratio ϕ ≤ 0.3 and ϕ ≥ 1.9, while the revised SL is well validated against the measurements. The improved SL correlation is incorporated into the QD combustion model by a user-defined function. The engine data are measured at 1000–2000 rpm under engine load net indicated mean effective pressure (IMEPn) = 0.4–0.8 MPa and ϕ = 0.5. The predicted engine performances and combustions are well validated with the measured data, and the model sensitivity analysis also shows a good agreement with the engine experiments under cycle-by-cycle variations.

Safety considerations on teenage pedestrian–bus impact

2019 ◽  
Vol 233 (14) ◽  
pp. 3839-3856
Author(s):  
Salvatore Golfo ◽  
Gabriele Virzì Mariotti ◽  
Filippo Carollo ◽  
Antonella Argo ◽  
Gabriele Barbaraci
Keyword(s):  
Thoracic Trauma ◽  
A Priori ◽  
Chest Injury ◽  
Abbreviated Injury Scale ◽  
Head Injury Criterion ◽  
Vehicle Mass ◽  
Biomechanical Parameters ◽  
Safety Considerations ◽  
The Impact ◽  
Good Agreement

This work studies the impact conditions between the adolescent pedestrian and the bus focusing on head and chest injury. The injury to the head is analyzed using both the Head Injury Criterion (HIC) 36 and the HIC15 parameters as established by the most advanced legislation and comparing the risk probability Abbreviated Injury Scale (AIS3+) and AIS4+. The parameter HIC15 gives a higher probability of risk with lower values, and therefore it can be considered more conservative. Moreover, the study of chest injury is performed with two different biomechanical parameters: the Thoracic Trauma Index (TTI) and the TTI(d); the last neglects the pedestrian mass. The results indicate that the parameters are equivalent for the assessment of chest injury. Instead the front pedestrian collision is characterized by 3 ms criterion. The results comparison with those obtained previously with other types of vehicles shows that, in all cases, the impact with the bus is most dangerous for the teenage pedestrian because of the higher values of the biomechanical parameters. Finally, the influence of the vehicle mass has been investigated, emphasizing how it cannot be neglected a priori. Numerical analysis results are in very good agreement with the results carried out experimentally, from several authors, in real accidents where buses are involved.

Development of a New Skeletal Chemical Kinetic Mechanism for Ethanol Reference Fuel

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
O. Samimi Abianeh
Keyword(s):  
Ignition Delay ◽  
Laminar Flame ◽  
Kinetic Mechanism ◽  
Chemical Kinetic ◽  
Flame Speed ◽  
Combustion Mechanism ◽  
Laminar Flame Speed ◽  
Surrogate Fuels ◽  
Chemical Kinetic Mechanism ◽  
Fuel Surrogates

A new skeletal chemical kinetic mechanism of ethanol reference fuel (including ethanol, iso-octane, n-heptane, and toluene combustion mechanisms) consisting of 62 species and 194 reactions is developed for oxidation and combustion of gasoline blend surrogate fuels. The skeletal ethanol chemical kinetic mechanism is added to the toluene reference fuel (TRF) mechanism (including iso-octane, n-heptane, and toluene combustion mechanisms) using reaction paths and semidecoupling model. The ignition delay and laminar flame speed of the new combustion mechanism were modeled by using several fuel surrogates at different pressures, temperatures, and equivalence ratios. The skeletal chemical kinetic mechanism ignition delay and laminar flame speed are validated by comparison to the available experimental data of the shock tube and plate burner. The results indicate that satisfactory agreement between predictions and experimental measurements are achieved.

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