Burning Velocity Research Articles

Effect of H2 addition on laminar burning velocity of NH3/DME blends by experimental and numerical method using a reduced mechanism

Blending dimethyl ether (DME) into ammonia (NH3) can efficiently enhance the combustion of pure NH3, and has attracted increasing attention. Partial dissociation of NH3 can convert NH3/DME to NH3/DME/H2 mixtures. This work measured the Markstein length and laminar burning velocity of NH3/DME/air mixtures for different blend ratios (100/0, 80/20, 40/60, and 0/100) with various H2 additions (0%, 20%, and 40%) at ϕ = 0.7–1.7, 0.1 MPa, and 298 K using a spherical constant-volume combustion method. A reduced kinetics mechanism was developed and optimized based on own prior detailed mechanism. This model gives more accurate predictions for NH3, DME, NH3/DME, and NH3/DME/H2 compared to previous models in terms of laminar burning velocity, ignition delay time, and species concentration. The experimental and modeling results show that the measured Markstein length of NH3/DME/H2 blends as a function of equivalence ratio presents different states for different NH3/DME blend ratios. The existence of H2 can effectively increase the laminar burning velocity of NH3/DME/air mixtures. Relative increase in laminar burning velocity (ESL) shows a non-monotonic tendency with increasing equivalence ratio for different H2 additions. The peak value of ESL for NH3/DME/air mixtures with various H2 additions appears at around ϕ = 1.5. This can be attributed to the dominant effect of C-contain and N-contain reactions rather than HO reactions at the rich burn side. Similar to ESL, the free radicals that dominate laminar burning velocity may transit from H, O, and OH to CH and NH radicals at around ϕ = 1.3 ∼ 1.6. The thermal effect also contributes to the ESL and laminar burning velocity for rich fuel.

The Effect of Wire Mesh on Premix Combustion with Butane Fuel in Bunsen Burners

Combustion is an important process in a variety of industrial, laboratory and household applications, and the use of devices that control the characteristics of the fire is essential. Bunsen burner is one of the common laboratory equipment used to produce flames in experiments and heating processes. Wire mesh is placed above the Bunsen burner to control air flow and has a crucial role in premix combustion by affecting efficiency, stability and heat distribution. In this study, an experimental investigation will be carried out on Bunsen burners using wire mesh 30, 40, and 50. Furthermore, parameters such as flame stability, flame height, and combustion speed will be measured. The results of this study indicate that the looser the wire mesh density, the burning speed tends to decrease. When using wire mesh 30, the value of the combustion velocity reaches 3.09 cm/s. Meanwhile, when using wire mesh 50, the value of the combustion velocity increased to 3.24 cm/s. This indicates that the wire mesh is getting tighter, air and fuel flow can move faster, thus increasing the combustion velocity. In addition, the density of wire mesh also affects the high flame produced. By using wire mesh 30, the flame height reached 29.69 mm, while using wire mesh 50, the flame height reached 21.56 mm. This shows that the higher the wire mesh density, the flame tends to be more stable and has a smaller height.

Laminar burning velocities and Markstein numbers for pure hydrogen and methane/hydrogen/air mixtures at elevated pressures

Spherically expanding flame propagations have been employed to measure flame speeds for H2/CH4/air mixtures over a wide range of H2 fractions (30 %, 50 %, 70 and 100 % hydrogen by volume), at initial temperatures of 303 K and 360 K, and pressures of 0.1, 0.5 and 1.0 MPa. The equivalence ratio (ϕ) was varied from 0.5 to 2.5 for pure hydrogen and from 0.8 to 1.2 for methane/hydrogen mixtures. Experimental laminar burning velocities and Markstein numbers for methane/hydrogen/air mixtures at high pressures, which are crucial for gas turbine applications, are very rare in the literature. Moreover, simulations using three recent chemical kinetic mechanisms (Konnov-2018 detailed reaction, Aramco-2.0-2016 and San Diego Methane detailed mechanism (version 20161214)) were compared against the experimentally derived laminar burning velocities. The maximum laminar burning velocity for 30 % and 50 % H2 occurs at ϕ = 1.1. However, it shifts to ϕ = 1.2 for 70 % H2 and to ϕ = 1.7 for a pure H2 flame. The laminar burning velocities increased with hydrogen fraction and temperature, and decreased with pressure. Unexpected behaviour was recorded for pure H2 flames at low temperature and ϕ = 1.5, 1.7 wherein ul did not decrease when the pressure increased from 0.1 to 0.5 MPa. Although, the measurement uncertainty is large at these conditions, the flame structure analysis showed a minimum decline in the mass fractions of the active species (H, O, and OH) with the rise in the initial pressure. Markstein length (Lb) and Markstein number (Mab and Masr) varied non-monotonically with hydrogen volume fraction, pressure and temperature. There was generally good agreement between simulations and experimentally derived laminar burning velocities, however, for experiments of rich-pure hydrogen at high initial pressures, the level of agreement decreased but remained within the limits of experimental uncertainty.

Reactive molecular dynamics simulation and chemical kinetic modeling of ammonia/methane co-combustion

Under the vision of “low carbonization”, ammonia (NH3), as a carbon-free hydrogen-rich fuel, blended with reactive additives, is an effective means to achieve low carbon emissions and reduce the consumption of traditional fossil fuels. In this work, the combustion behaviors of NH3 and CH4, the distribution of main products and the formation and reduction characteristics of NO at different temperatures, CH4 mixing ratios, and O2 equivalence ratios are explored by means of reactive molecular dynamics simulation to reveal the microscopic mechanism of NH3/CH4 co-combustion. The calculated results show that CH4 takes the lead in producing H radicals which react with O2 to generate OH radicals to promote the oxidation of NH3, and it is found that the co-combustion process of NH3/CH4 in the radical chain transfer stage is similar to the respective pyrolysis and oxidation reactions of CH4 and NH3. Accordingly, an optimized kinetic mechanism of NH3/CH4 co-combustion is constructed based on the mechanisms proposed by Glarborg et al. and Okafor et al. by incorporating the NH3 pyrolysis sub-mechanisms related to NH2, HNO, and N2H2 and the skeletal mechanism of CH4 oxidation. The optimized mechanisms of NH3/CH4 co-combustion are found to improve the prediction of the ignition delay time (IDT) and laminar burning velocity (LBV) of NH3/CH4 mixture under wide ranges of conditions compared to the original mechanisms of Glarborg et al. and Okafor et al. To decrease the computational cost of three-dimensional combustion numerical simulations, the skeletal mechanism models are established by simplification of the optimized mechanisms of NH3/CH4 co-combustion using direct relation graph method with error propagation and sensitivity analysis, which can provide nearly the same estimates of IDTs and LBVs as the optimized mechanisms mentioned above.

Ammonia/syngas MILD combustion by a novel burner

Ammonia has received increasing attention as one of the most attractive energy carriers because of its carbon-free nature and the established reliable and economic infrastructure for its storage and distribution. However, the low burning velocity and nitrogen-containment of pure NH3 can cause some challenges for its combustion control such as flame instability and large NOx emissions. To overcome these issues, strategies of co-burning NH3 with highly reactive fuels such as CH4 or H2 have been developed and applied. Syngas, which can be produced from biomass pyrolysis, is a promising alternative fuel in the transition from carbon-based fuels to carbon-free fuels. Therefore, comparing to co-firing NH3 with CH4, co-firing NH3 with syngas is a better environmentally friendly option to improve the NH3 combustion property. However, co-firing NH3 with syngas faces severer combustion instability, NOx emissions and NH3 leakage due to the low heating value of syngas. To the best of the authors’ knowledge, the NH3/syngas combustion with low NOx emissions and zero NH3 leakage has not been achieved in a lab-scale combustor. In the present study, NH3/syngas MILD combustion was carried out in a novel burner developed in our previous work. In the novel burner, the high-temperature and diluted air produced by the lean premixed syngas combustion is the key to accomplish the MILD combustion of NH3. The impact of the temperature and O2 mole fraction of the HTDA on the emissions of NO, NO2, N2O, NH3, and CO was experimentally investigated with varying equivalence ratios and NH3 flow rates. The chemical reactor network was employed to analyze the experimental observation from the chemical kinetic aspect.

Expansion Coefficients and Propagation Speeds of Premixed n-Butane–Air Flames

The propagation speeds of premixed n-butane–air mixtures (2.0–5.7 vol%) were investigated under various initial conditions (pressures of 0.4–1.2 bar; temperatures of 289–500 K). The study consists of both, experimental measurements using two different enclosures (a sphere and a cylinder) and kinetic modeling via a dedicated computing program. The propagation speeds of premixed n-butane–air mixtures were obtained via the adiabatic model of flame propagation, which allows us to obtain these important parameters using the normal burning velocities and expansion coefficients. The expansion coefficients were calculated using thermodynamic data as the ratio of burnt to unburnt gas densities, assuming that an equilibrium was established in the flame front. The propagation speeds obtained based on the experimental burning velocities were analyzed for comparison with the computed velocities. Finally, the dependence of the propagation speed on the initial pressure and temperature was discussed.

Traditional vs. Energetic and Perchlorate vs. "Green": A Comparative Study of the Choice of Binders and Oxidising Agents.

The aim of this article is to compare rocket propellants containing a traditional binder (hydroxyl-terminated polybutadiene) and an energetic binder (glycidyl azide polymer), as well as a perchlorate oxidising agent and a "green" one, i.e., ammonium perchlorate and phase-stabilised ammonium nitrate. We have outlined the effects of individual substances on the sensitivity parameters and decomposition temperature of the produced solid propellants. The linear combustion velocity was determined using electrical methods. Heats of combustion for the propellant samples and the thermal decomposition features of the utilised binders were investigated via differential scanning calorimetry (DSC). Activation energy values for the energetic decomposition of the propellants were determined via the Kissinger method, based on DSC measurements at varied heating rates.

The Lean-Burn Limit Extending Experiment on Gasoline Engine with Dual Injection Strategy and High Power Ignition System

In the context of the energy crisis and global warming, improving thermal efficiency is the most important issue in research on gasoline engines, and lean mixture combustion strategy is becoming the most promising method. Thus, a high compression ratio, a high-power interval ignition system, and a stratified combustion scheme achieved via dual injection were novelly adopted in a single cylinder gasoline engine in this study. The results show that the lean combustion limit could be literally extended and improved thermal efficiency was observed under the ultra-lean condition. Meanwhile, reverse combustion performance trends were observed by altering the second injection proportion from 30% to 45% under the lean condition (λ = 1.6) and ultra-lean condition (λ = 1.9). This was related to a combustion velocity change caused by great concentration gradient at the middle and end combustion stage. Finally, according to research on the effects of altering the timing of the second injection, it is clear that the dual injection strategy is an ideal method for realizing operation under the lean condition (λ = 1.6). But for the operation under the ultra-lean condition (λ = 1.9), more injection times and suitable air flow organization are needed to enhance the robustness of mixture distribution.

Enhancement in ignition and combustion of solid propellants by interfacial modification of Al/AP composites with transition metals

To improve the ignition and combustion behaviors of Al, the strategy of interfacial modification using transition metals (TMs) for the Al/AP composites to produce the multi-layered core-shell structured Al@TMs@AP composite fuels is provided. The relevant Al-based composite fuels are fabricated using spray granulation method and their morphologies are characterized by SEM and TEM techniques. The ignition and combustion of the solid propellants prepared with the core-shell structured composite fuels are evaluated and compared with that of reference propellant formulated with typical compositions using laser ignition setup and combustion diagnostic system. Results indicate that the heats of reaction measured for the Al@TMs@AP contained propellants are increased by as high as 13%, suggesting the completeness in combustion of Al is greatly improved by construction of Al composites with the multi-layered core-shell structure. The ignition delay times are apparently shortened from 421 ms to 373 ms for the propellants with Al@TMs@AP involved, which proves that the promoted ignition of Al is achieved by surface modification with transition metals. Additionally, the significantly increased burning velocity is monitored for the Al@TMs@AP contained propellants at low-pressure regime leading to the corresponding pressure exponents to be reduced by more than 20%, which is beneficial to the stability in operation of solid rocket motors. At last, the higher combustion wave temperature and finer particle size in CCPs are observed for the propellants containing surface modified Al, and the plausible combustion mechanism is proposed based on the phase composition analysis for the CCPs of studied propellants.

Effect of hydrogen addition on the laminar burning velocity and the flame stability of n-dodecane reacting with air at elevated pressures

The effects of hydrogen addition on the premixed laminar burning characteristics of n-dodecane reacting in air were experimentally investigated using the freely expanding spherical flame method. The initial operating conditions were temperature = 425 K, pressure = 1 ˗ 4 bar, equivalence ratio = 0.8–1.4, and mole fraction of H2 in n-dodecane-H2 mixture = 0–40%. Nonlinear stretch extrapolation schemes were implemented to minimize the uncertainty in the estimation of unstretched flame speed as the binary fuel mixtures of n-dodecane and H2 had non-unity Lewis numbers. All experimental operating conditions were simulated in CHEMKIN using a planar flame model with three different reaction mechanisms. The statistical uncertainty estimated for the LBV was below ±6.93%. The LBV increased by three/two times at off–stoichiometric/stoichiometric mixtures as the mole fraction of hydrogen (XH2) increased from 0 to 40% in n-dodecane. The rich mixtures of n-dodecane-air (ϕ = 1.4) were unstable to thermo-diffusive effects due to the lower mass diffusivity of n-dodecane and Le < 1, in contrast, H2 blending to the n-dodecane by keeping the other parameters being same transformed it from an unstable to a stable one. The effective Lewis number and Markstein length decreased with an increasing XH2 in n-dodecane, indicating that the mixtures were stable to thermo-diffusive effects, but with further increase in XH2, there may be a transition in flame stability. H2 addition resulted in an earlier onset of hydrodynamic instability due to a reduction in the flame thickness. In addition, sensitivity analysis was performed to identify the key reactions responsible for the enhanced reactivity associated with H2 addition. The reaction pathway and emission analysis showed a significant reduction in CO2 and CO emissions. Finally, an increase of initial pressure decreased the LBV for all investigated mixtures.

Explosion behaviors of hydrogen-nitrous oxide mixtures with propane addition

In the present work, the explosion of hydrogen-propane-nitrous oxide mixtures with various equivalence ratios (ϕ=0.2-2.4), propane fractions (ωC=0-1.0) and initial pressures (P0=50-100 kPa) at ambient temperature (288 K, room temperature) was experimentally performed in a standard 3.375-L cubic vessel. The maximum explosion pressure (Pmax), maximum pressure rise rate ((dp/dt)max) and explosion time (te) were obtained in light of pressure–time curves, and the normalized maximum explosion pressure (Pmax/P0) and normalized explosion time (td/te) were analyzed as well. Moreover, the adiabatic pressure (Pad) and laminar burning velocity (SL) were also calculated for argumentation. The results indicate that with the increase of ωC, Pmax and (dp/dt)max both present three characteristic variation trends for different ϕ, while the inflections of Pmax-ϕ and (dp/dt)max-ϕ transient gradually from lean to rich mixtures. Besides, te and td/te are monotonously rising with ωC, illustrating that propane addition can remarkably decelerate the explosion process. In addition, with the increase of P0, Pmax/P0 raises monotonously and is asymptotic to Pad/P0 at ωC⩽0.2, demonstrating that heat loss decreases under higher P0. Linear dependence is also found between (dp/dt)max and P0 for any composition. Furthermore, te monotonically decreases with P0, due to the flame acceleration occurring in the combustion period. In general, the presence of nitrous oxide (N2O) with a large content makes the explosion extremely unstable, and a spot of propane can dramatically alter the explosion characteristics of H2-N2O mixtures. These results will be meaningful for the development of explosion-mitigation devices and technology in case of underlying explosion and fire hazards.

The State of the Art of Laminar Burning Velocities of H2-Enriched n-C4H10–Air Mixtures

Currently, hydrogen-enriched n-butane blends present a real interest due to their potential to reduce emissions and increase the efficiency of combustion processes, as an alternative fuel for internal combustion engines. This paper summarises the recent research on laminar burning velocities of hydrogen-enriched n-C4H10–air mixtures. The laminar burning velocity is a significative parameter that characterises the combustion process of any fuel–air mixture. Accurately measured or computed laminar burning velocities have an important role in the design, testing, and performance of n-C4H10–H2 fuelled devices. With this perspective, a brief review on the influence of hydrogen amount, initial pressure and temperature, and equivalence ratio on the laminar burning velocity of hydrogen-enriched n-C4H10–air mixtures is presented. Hydrogen has a strong influence on the combustion of butane–air mixtures. It was observed that a parabola with a maximum at a value slightly higher than the stoichiometric ratio describes the variation in the laminar burning velocity of hydrogen-enriched n-butane–air mixtures with the equivalence ratio. An increase in initial pressure or hydrogen amount led to an increase in this important combustion parameter, while an increase in initial pressure led to a decrease in laminar burning velocity. Overall, these studies demonstrate that hydrogen addition to n-C4H10–air mixtures can increase the laminar burning velocity and flame temperature and improve flame stability. These findings could be useful for the optimisation of combustion processes, particularly in internal combustion engines and gas turbines. However, the literature shows a paucity of investigations on the laminar burning velocities of hydrogen-enriched n-C4H10–air mixtures at initial temperatures and pressures differing from those in ambient conditions. This suggests that experimental and theoretical investigations of these flames at sub-atmospheric and elevated pressures and temperatures are necessary.

Experimental and simulation study of NH3–H2-Air flame dynamics at elevated temperature in a closed duct

Ammonia allows for long-distance and large-scale storage transport of renewable energy sources. The reactivity of NH3-Air flame can be enhanced by doping with hydrogen and by increasing the initial temperature. The flame combustion characteristics of NH3–H2-Air are studied in a rectangular closed pipe with a mole fraction of 45% H2, an equivalence ratio (φ) of 0.8–1.2 and 0.1 MPa. The initial temperatures (Tu) of the mixture are 300 K, 375 K and 450 K. Experimental studies of flame front speed, flame tip structure evolution, and overpressure dynamics are performed. Laminar burning velocity (SL), peak mole fraction of key radicals, and flame instability of NH3–H2-Air flames are simulated in Chemkin Pro-software using the Mathieu and Petersen mechanism. The results show that the relatively low equivalence ratio and initial temperature promote the structural changes of the flame tip, forming a “tulip” flame and a distorted “tulip”. As the equivalence ratio increases, the flame front speed and overpressure increase and the flame oscillates slightly. The distortion in the lip of the “tulip” is more pronounced. The increase in temperature promotes flame propagation in the early stages and the pressure decreases. Reactive activity increases with increasing temperature, the peak mole fraction of NH2 and H radicals increases, and SL increases. At normal temperature, the flame is affected by thermo-diffusive instability only when lean mixture. The Darrieus-Landau instability increases as the equivalence ratio increases. Conversely, the Darrieus-Landau instability decreases with increasing temperature. Therefore, the current experimental and simulation results help to understand the laminar combustion characteristics of NH3–H2-Air at high temperatures.

Effect of ammonia addition on laminar burning velocity of CH4/H2 premixed flames at high pressure and temperature conditions

Global emissions of nearly 30% stem from fossil fuel combustion for long-distance transportation vehicles. Therefore, investigations on newer alternatives for clean and green fuels is desired in pursuance of net-zero carbon emissions by 2050. Given this contemplation, the current study aims at studying the effect of ammonia addition, a carbon-free fuel, on laminar burning velocity of CH4/H2 fuel blends at high-pressure and high-temperature conditions utilizing the high-pressure diverging-channel method. The NH3 varies from 0% to 30% in the CH4/H2 fuel blend by volume. With regard to adiabatic flame temperature, this NH3/CH4/H2 mixture is comparable to pure CH4-air mixtures, but with a reduction in carbon emissions of about 26.6%. The research involves conducting measurements at high temperatures between 300 K and 750 K, pressures between 1 atm and 5 atm, and equivalence ratios between ϕ = 0.7 and 1.4. When the pressure is 5 atm, the obtained burning velocities of NH3/CH4/H2 blends are analogous to that of CH4-air mixtures. The temperature exponent, α, does not change when the NH3 fraction or pressure changes, but at high temperatures there is a slight shift in the pressure exponent, β. The experimental results suggest that the Okafor and Li kinetic models align well with the measurements made in the current work up to 5 atm, while the Reduced GRI Mech 3.0 mechanism overestimates the burning velocity values. Additionally, an increase in NH3 fraction and pressure results in a decrease in burning velocity and NO formation due to the presence of NHi (i = 0–2) radicals. Overall, this study convincingly demonstrates the viability of NH3/CH4/H2-air mixtures as a practical alternative to reduce carbon emissions.

Comparative study of NH3 and H2 impacts on combustion and emission characteristics of n-Hexadecane under different flame conditions

The addition of renewable fuel to hydrocarbon fuel mitigated the carbon monoxide, carbon dioxide and soot particle emissions of internal combustion engines. A comparative study of the ammonia and hydrogen effect on combustion and emission characteristics of n-hexadecane flames was executed at various flame conditions. The results showed that alternative fuels had a stronger impact on peak temperature at diffusion flame conditions rather than at premixed flame conditions. The premixed flame released carbon monoxide emission lower than the diffusion flames with/without additional fuels. The carbon monoxide emissions decreased highly with ammonia enrichment instead of hydrogen. At premixed and coflow diffusion flame conditions, the ammonia highly reduced carbon dioxide emission compared to hydrogen. Hydrogen addition reduced the nitrogen oxide emission, whereas it was increased by ammonia. The soot particle number density was reduced highly by hydrogen addition instead of ammonia at the premixed flow flame and diffusion coflow flame conditions. The impact of hydrogen on the reduction of soot mass concentration emissions was greater than that of ammonia at all combustion conditions. It is suggested that H2 ≥ 70% should be mixed in n-hexadecane fuel because a higher burning velocity can be achieved with a higher emission reduction. A reduction in the emission of carbon-related species can be realized with a small reduction in burning velocity at NH3 < 70%.

Numerical and experimental investigation of many-objective optimization for efficient temperature and velocity fields reconstruction via acoustic tomography

Accurate and high-quality measurement of temperature and velocity fields is important in combustion and flow diagnosis, especially for the control of boiler operations and optimization of combustion processes. Nonlinear acoustic tomography (NAT) is an appealing approach to simultaneously monitor temperature and velocity fields by observing the changes in sound speed they induce. However, the inherent ill-posedness of the tomographic inverse problem and the lack of a priori information may lead to poor robustness, low precision, and the presence of artifacts. On the other hand, the inclusion of a priori information, such as smoothness and box constraints, may require the use of hyperparameters that hinder quasi real-time reconstruction and may degrade performance in actual applications. In this study, we aim to ensure quasi real-time reconstruction and alleviate the ill-posedness of the NAT problem by eliminating the regularization parameters and transforming the inverse problem into a many-objective optimization problem with four objectives. The knee point-driven evolutionary algorithm with improved environmental selection strategy (KEA-IES) is proposed to simultaneously reconstruct the arbitrary inhomogeneous temperature and aerodynamic fields in a furnace. Apart from the investigation of the performance of KEA-IES and the influence of various factors, including measurement noise, function evaluation number, population size, and functional norms, on the quality of the reconstruction, an experimental AT system with independent 16 T/R channels is developed to evaluate the proposed method. The results show that combustion flame temperature and velocity fields can be monitored simultaneously by using the proposed KEA-IES with more accuracy, less consumed time, and better noise immunity compared with the state-of-the-art algorithms. The proposed method can provide valuable guidance in the development of a non-intrusive real-time pyrometry and velocimetry system, particularly for applications with large velocity fields and temperature gradients. Furthermore, its capability in complex combustion and flow diagnosis will offer benefits in terms of energy conservation, emission reduction, boiler operations supervision, and combustion process optimization.

Flammability Properties of the Pyrolysis Gas Generated from Willow Wood

Willow wood presents a real interest for biomass pyrolysis due to its fast growth, renewability, and high energy density. Following the pyrolysis of willow wood in an inert atmosphere, a multi-fuel gaseous mixture was obtained, with the following composition (by volume): 38.20% CO/21.87% H2/17.44% CH4/1.15% O2/17.15% CO2/4.19% N2. The propagation of laminar premixed flames in these multifuel mixtures with air was investigated numerically for initial temperatures from 298 to 500 K, initial pressures from 1 to 20 bar, and fuel equivalence ratios between 0.60 and 2.00. The combustion of these gaseous mixtures as free laminar premixed flames was simulated by means of the INSFLA package and an extended reaction mechanism with 592 elementary reactions and 53 species. The modelling of the gas-phase combustion delivered several important parameters: the laminar burning velocities, Su, the maximum flame temperatures, Tfl,max, the flame front thicknesses, dfl, and the peak concentrations of the main reaction intermediates. The obtained parameters, discussed in correlation with the initial pressure and temperature, afforded the determination of the overall activation parameters of multifuel oxidation with air.

Effect of 2-Butanone addition on laminar burning velocity of gasoline XP95 at higher mixture temperatures

2-Butanone, a product of pyrolysis of biomass, micro-biological fermentation of agricultural waste, possesses several advantages as a next generation biofuel for spark ignition engines. Very little is known about its combustion behavior due to non-availability of detailed combustion measurements. In this study, the laminar burning velocities (LBV) of 2-Butanone were measured and compared with benchmarked ethanol and gasoline using the externally heated diverging channel method. The measurements were conducted for 2-Butanone (B), premium gasoline (XP95) and their three different fuel blends (volume fraction: 10% B + 90% XP95, 30% B + 70% XP95, and 50% B + 50% XP95) for fuel-air equivalence ratios (ϕ) = 0.6–1.4, at elevated mixture temperatures of 300–620 K, and atmospheric pressure (1 bar). The present measurements of 2-Butanone show a good match with the values reported in literature and exhibit a good consistency with the predictions of Hemken 2017 reaction mechanism. The sensitivity analysis reveals that the inhibition effect of the key reaction R43: CH3 + H (+M) ⇔ CH4 (+M) is reduced by 34%, when the mixture temperature increased from 305 K to 620 K at ϕ = 1.1 and increased by 39% with an increase in mixture equivalence ratio from 0.7 to 1.3 at 620 K. The LBV of 2-Butanone shows a slight difference with ethanol and gasoline for leaner mixtures (ϕ = 0.6, 0.7). However, with increase in mixture strength (ϕ ≥ 0.8), the LBV becomes significantly higher than that of gasoline XP95 and slightly lower than ethanol regardless of the mixture temperature. With addition of 2-Butanone in gasoline XP95, the LBV improved by 14%, 24.6%, and 36.1% for 10% B + 90% XP95, 30% B + 70% XP95, and 50% B + 50% XP95 blends respectively, at ϕ = 1.0, 620 K. From the improved flame behavior of 2- Butanone under typical engine operating conditions against benchmarked ethanol, makes it a suitable biofuel substitute for gasoline in a sustainable transportation application.

An experimental and modeling study on the laminar burning velocities of ammonia + oxygen + argon mixtures

Most often, the laminar burning velocity (SL) of ammonia was measured in mixtures diluted by nitrogen bearing in mind its potential use as an alternative carbon-free fuel. Replacing the diluent with argon can increase the flame temperature and thus provide additional targets for validating pertinent detailed kinetic models. The SL data for ammonia + oxygen + argon mixtures are scarce; therefore, in the present study, new measurements have been performed using the heat flux method at an initial temperature of 298 K and atmospheric pressure over an equivalence ratio range of 0.4–1.5. The argon mole percentage in the mixture has been changed from 30 to 60%. Nine recent ammonia kinetic models are selected and validated against these new experimental data, where it is found that the models by Han et al. (Combust. Flame 228 (2021):13), Shrestha et al. (Proc. Combust. Inst. 38 (2021):2163), and Okafor et al. (Combust. Flame 204 (2019):162) provide the best predictions. Further sensitivity analysis showed that the most crucial nitrogen-related reactions for SL in present flames found in the model of Shrestha et al. are different from the other two, and flux analysis elucidated that the main consumption fluxes of NH2 radical are different among the three models. The model of Han et al., which is from the authors’ group, was revisited, and the rate constants for three reactions NH2+H(+M)=NH3(+M), NNH+ONH+NO, and NH2+OHNO+H were modified. Available speciation data from shock tube and flame studies are used to select the most suitable rate constants among expressions recommended in the literature. The updated model performs well in reproducing a range of SL, ignition delay times, and speciation data from a jet-stirred reactor for ammonia + oxygen + argon mixtures.

3-D Map Producing for Groundwater Level using Kriging Interpolation Method

The effect of the initial pressure upon the laminar flame speed, for a methane-air mixtures, has been detected paractically, for a wide range of equivalence ratio. In this work, a measurement system is designed in order to measure the laminar flame speed using a constant volume method with a thermocouples technique. The laminar burning velocity is measured, by using the density ratio method. The comparison of the present work results and the previous ones show good agreement between them. This indicates that the measurements and the calculations employed in the present work are successful and precise