Equivalence Ratio Research Articles

The laminar burning velocity of propyl acetate at high pressures and temperatures

Since propyl acetate has the potential to be used as a biofuel in heat engines, it is necessary to ascertain and comprehend its combustion properties. Using equivalence ratios of 0.7–1.4, the laminar burning velocity of propyl acetate was studied in the constant volume combustion vessel at the initial pressures of 1, 2, and 4 bar and initial temperatures of 390 K, 420 K, and 450 K. The constant volume method was used to determine the burning velocity via extrapolations at the initial condition. In addition, a ten-fitted empirical correlation was formulated to calculate the burning velocity for pressures and temperatures as high as 8 bar and 534 K, respectively. The extrapolated burning velocity showed good agreement with the numerical simulation burning velocity, and the correlated burning velocity agreed well with the extrapolated burning velocity. The laminar burning flux was also investigated and was ascertained that laminar burning flux increases as the initial pressure and temperature increase. The fuel mixture density significantly influences the burning flux as the initial pressure rises, whereas the laminar burning velocity has a notable impact on the burning flux as the initial temperature rises. In summary, this study advances our knowledge of propyl acetate combustion, particularly concerning its flame propagation at higher pressures and temperatures and its potential application in combustion engines, and the data are of great engineering value for developing and understanding the combustion science of propyl acetate.

Suppression effects of different extinguishing agents on vent gases fires from lithium-ion batteries after thermal runaway: A comprehensive experimental and numerical study

During the thermal runaway process of lithium-ion batteries, the release of vaporized electrolyte and combustible gases can lead to the formation of a jet flame, posing a significant fire or explosion risk. In order to deal with the threat of lithium-ion battery vent gas fires to the safety of energy storage power stations, it's crucial to identify effective fire extinguishing agents for lithium-ion battery systems. This study employs a combination of experimental and numerical simulation methods to assess the suppression capabilities of CO2, N2, and HFC-227ea on vent gas/air premixed flames originating from lithium-ion batteries with various cathode materials. Laminar flame speed of vent gas/air/extinguishing agent premixed flames at specific equivalence ratios were measured using a Bunsen burner device under ambient temperature and atmospheric pressure conditions. Additionally, numerical calculations of laminar flame speed and adiabatic flame temperature were conducted using CHEMKIN-Pro, accompanied by an analysis of the chemical inhibition mechanism of HFC-227ea. The findings reveal that although HFC-227ea may slightly elevate the adiabatic flame temperature at lower equivalence ratios, its overall fire extinguishing efficacy surpasses that of CO2 and N2. These results offer valuable insights for selecting appropriate fire extinguishing agents for energy storage power stations, thereby enhancing the safety standards of energy storage systems.

Experimental study on the seismic performance of prestressed wood joints with buckling-restrained rods

Adding energy dissipaters to prestressed wood joints with reinforced beam-column interfaces is the main way to improve their seismic performance. In this paper, three quasistatic tests for beam-column edge joints with buckling-restrained rods (BRRs) were performed, and the effects of different reinforcements for beam-column interfaces and BRR connection methods on the stiffness, bearing capacity, energy dissipation, and self-centering performance of the joints were analysed. First, for BRRs connected with steel supports, the core member exhibited significant multi-wave deformation; for BRRs connected with steel pins, the slippage of the steel pins can easily lead to bending failure of the BRR end. Second, after adding BRRs, the bearing capacity of the joints increased by 24.8% on average, the final degradation rate of the secant stiffness decreased by 13.8% on average, and the equivalent viscous damping ratio at 0.03 rad drift increased by 17.3% on average. Third, compared with the joint reinforced by the combination of the U-shaped steel plate and screws, the skeleton curve of the joint reinforced by the combination of the flat steel plate and screws had little difference, but the final prestressing loss and residual drift were reduced by 14% and 74%, respectively. It was recommended to use the simpler reinforcement combining the flat steel plate and screws to improve construction efficiency. Finally, compared with steel pins, BRRs connected with steel supports were more conducive to improving the seismic performance of joints at large drifts. Among them, the equivalent viscous damping ratio increased by 29.3% on average. This study can give designers flexibility when selecting the interface reinforcements and BRR connection methods. These research results highlight the good seismic performance of prestressed wood joints with BRRs, which is conducive to further promoting the application of prestressed wood structures.

A Comprehensive Review of Syngas Production, Fuel Properties, and Operational Parameters for Biomass Conversion

This study aims to provide an overview of the growing need for renewable energy conversion and aligns with the broader context of environmentally friendly energy, specifically through producing syngas from biomass. Unlike natural gas, which is mainly composed of methane, syngas contains a mixture of combustible CO, H2, and CnHm. Therefore, optimizing its production requires a thorough examination of various operational parameters such as the gasifying agent, the equivalence ratio, the biofuel type, and the state, particularly in densified forms like pellets or briquettes. As new biomass sources are continually discovered and tested, operational parameters are also constantly evaluated, and new techniques are continuously developed. Indeed, these techniques include different gasifier types and the use or non-use of catalysts during biofuel conversion. The present study focuses on these critical aspects to examine their effect on the efficiency of syngas production. It is worth mentioning that syngas is the primary gaseous product from gasification. Moreover, it is essential to note that the pyrolysis process (prior to gasification) can produce, in addition to tar and char, a mixture of gases. The common feature among these gases is their versatility in energy generation, heat production, and chemical synthesis. The analysis encompasses the resulting gas features, including the yield and composition, mainly through the hydrogen-to-carbon monoxide ratio and the carbon monoxide-to-carbon dioxide ratio, as well as the lower heating value and considerations of the tar yield.

Gasification characteristics and sulfur migration mechanism during supercritical water partial oxidation of 2-methylthiophene

Supercritical water partial oxidation (SCWPO), as a clean and efficient energy conversion technology, offers new insights for the clean treatment of thiophene compounds, which are a significant source of potential pollutants. However, the detailed reaction mechanism of thiophene compounds in the SCWPO process is still unclear. Therefore, the effects of parameters on gasification characteristics and sulfur migration were investigated in the quartz tube reactor during the SCWPO of 2-methylthiophene (2-MT). The results demonstrated that extending the reaction time, increasing the reaction temperature, and reducing the feed concentration favored gaseous product generation. The SCWPO environment with the low equivalent ratio (ER) was favorable for the generation of hydrogen-rich gas. When the conditions were 750 °C, 4 wt%, 15 min, ER = 0.2, the highest H2 yield was 18.59 mol kg−1. With the addition of oxidants, the SCWPO environment promoted the conversion of sulfur from S-2, S-o to S+4, S+6. This conversion reduced the sulfur content in the gas, making it stored in a more environmentally friendly form. Notably, the presence of SOx was not detected during the SCWPO process. Finally, a detailed reaction mechanism for the SCWPO of 2-MT was proposed based on the comprehensive analysis of experimental products.

Experimental study on reactivity and inorganic component transformation of activated fuels in a fluidized bed

The gasification and combustion of activated fuels produced from fluidized bed are beneficial for achieving clean and efficient coal utilization. In this study, a high-calcium coal was used for the activation process, carried out in a high-temperature vertical fluidized bed. The carbon and ash characteristics of activated fuels were studied. The reactivity of activated fuels was characterized using Raman test, and scanning electron microscopy coupled with energy-dispersive spectrometry (SEM-EDS). Inorganic components were characterized using X-ray diffraction (XRD), and X-ray fluorescence spectrometry (XRF). With the increase of temperature and equivalence ratio (ER), the graphitization degree of activated fuels decreases, and a higher proportion of active sites leads to, a better activation effect. The activation effect is optimized at the equivalence ratio of 0.45. As the temperature rises, the calcium-containing minerals in the raw coal are gradually transformed into anorthite (CaAl2SiO7), and the anhydrite (CaSO4) reacted with the reducing gas (CO) to produce oldhamite (CaS); Fe2O3 as a fluxing agent, is prone to melting with silica-aluminates at high temperature. As the particle size of activated fuel increased, the relative enrichment index (REI) of heavy metals decreases.

Time/frequency domain analysis of detonation wave propagation mechanism in a linear rotating detonation combustor

Controlling the rotating detonation combustor (RDC) is crucial for enhancing propulsion system safety, efficiency, and overall performance. Swift and precise identification of the operational mode of RDC is of great significance for refining the propulsion dynamics of detonation-based technologies. In this study, two-dimensional numerical simulations are performed to investigate time-domain characteristics and frequency-domain characteristics of various operational modes of the RDC, hydrogen–air mixtures are used as fuel, and fast Fourier transformation (FFT) is applied to the analysis of frequency-domain. The alteration of the RDC operational mode is achieved through adjustments to the chemical equivalent ratio (ER) of the fuel, spanning from 0.52 to 3.50. Our findings reveal four distinct operational modes within this equivalent ratio range: ignition failure (ER ≤ 0.52 and ER ≥ 3.50), collision failure (ER = 0.85, 1.60 and 1.65), single wave (0.53 ≤ ER ≤ 0.80 and 1.70 ≤ ER ≤ 3.40) and multiple wave mode (0.90 ≤ ER ≤ 1.50). For the ignition failure mode, the detonation waves in RDC decouple from the flame and fail after ignition. In the collision failure mode, the inability of detonation waves to propagate sustainably within the RDC is evident. Frequency-domain analysis underscores the significance of a characteristic low-frequency (0.3 kHz) in distinguishing this mode from others. For single wave mode, it represents the steady and continuous propagation of a detonation wave in the RDC. Frequency-domain analysis reveals characteristic frequencies approximately equal to integer multiples of the propagation frequency (fD), where fD ∼ 10fD serves as the primary characteristic frequencies. The multiple wave mode can be categorized into two subtypes: the forward and reverse single detonation waves appear alternately or the forward and reverse single detonation waves finally co-direction double detonation waves. In the former subtype, characteristic frequencies are integer multiples of the fD, but the amplitude distribution is different with single wave mode. In contrast, primary characteristic frequencies of the latter subtype are fD ∼ 4fD, accompanied by two adjacent characteristic frequencies near each integer multiples of fD. These findings promise advancements in the controllability of RDC and lay the foundations for the development of RDC control systems.

Hybrid CFD/techno-economic assessments of carbon capturing combustion system integrated with PEM electrolyzer for efficient hydrogen production

The issue of global warming is a significant challenge in the field of environmental science, resulting primarily from the burning of fossil fuels and the subsequent increase in greenhouse gas (GHG) emissions, thus emphasizing the importance of utilizing renewable energy vectors, carbon capture technology, oxy-fuel combustion, and carbon-free fuels like hydrogen to mitigate these negative effects. In this study, the possibility of utilizing low-calorific value biogas in a gas turbine (GT) combustor under various combustion conditions is numerically simulated, and techno-economic analysis of energy systems coupled with the GT combustor is conducted. Herein, two distinct energy systems utilizing different combustion modes for H2 production via PEM electrolyzer have been designed and examined. This investigation focuses on the impact of various influencing factors in oxy-fuel combustion mode, such as the equivalence ratio and the O2 content in the two types of oxidizers, on the rate of hydrogen production, power generation, energy/exergy efficiencies, and the economic index of the proposed energy system. Additionally, a suitable system for large-scale operation is identified among the presented systems. The findings of the study demonstrate that the energy system based on the O2/CO2 combustion mode exhibits a higher rate of hydrogen production compared to the O2/H2O combustion mode and particularly, within the equivalence ratio range of 0.55≤ϕ ≤ 0.85, the hydrogen production rate in the O2/CO2 combustion mode decreases from 5.16 kg/h to 3.72 kg/h.

Emission Spectra of Ammonia Laminar Flames in Spherically Propagating Flames and a Modified McKenna Burner

ABSTRACT Ammonia (NH3) has received significant attention recently as a promising carbon-free, low-cost, and safe candidate as a chemical energy storage element and/or fuel alternative. As for any new fuel, fundamental aspects of the combustion process, such as the detailed chemical kinetic pathways of NH3 oxidation, flame propagation and stability, and emissions, are to be understood to predict its combustion behavior in practical systems. One aspect of improving our understanding of the combustion behavior of NH3 is to explore the emission spectra of spherically expanding and/or Bunsen-type flames under controlled laboratory conditions. In this study, flame spectra from NH3-containing mixtures were obtained utilizing two different experimental flame configurations, namely a spherically propagating flame and a modified Mckenna burner flame. Two different fuel mixtures were investigated. The first was an oxy-ammonia mixture consisting of NH3 + (25% O2 +75% N2) with the goal of studying neat ammonia. The second mixture consisted of H2:NH3:N2 with a ratio of 45:40:15 by volume. Several excited-state species within the UV-visible spectral region were identified. For instance, NO* emission features were found between 220 and 280 nm. In addition, OH* emission was detected around 310 nm, and an NH* feature was seen around 337 nm. Moreover, a broadband intensity was reported over the visible range (400 ~ 800 nm), where several NH2* features were also detected. The effect of the mixture on the flame spectra was investigated by examining the two different mixtures utilizing the same experimental apparatus (spherical flame in this case), and it was shown that the mixture has an effect on the presence of NH2* features, which was also backed by chemical kinetics predictions for the NH2* mole fraction profiles. It was shown (from kinetics) that the oxy-ammonia mixture produced more NH2* than the H2:NH3:N2 mixture by up to 113%. Additionally, the effects of the flame configuration were also investigated by studying the same mixture (the H2:NH3:N2 mixture in this case), and it was revealed that the spectra produced using the modified Mckenna burner had less noise, and all features were easily identified. Lastly, laminar flame speeds of the oxy-ammonia mixture were measured using the spherical flame apparatus. The laminar flame speed followed the expected pattern, peaking near a 1.1 equivalence ratio with a measured flame speed of 22.7 cm/s.

Investigations of Combustion Characteristics of N-Dodecane/Air Mixtures at High Temperatures Through Laminar Burning Velocity Measurements

ABSTRACT In this work, combustion characteristics of premixed n-dodecane/air mixtures are investigated at elevated mixture temperatures through laminar burning velocity measurements at atmospheric pressure and elevated temperatures using an externally heated diverging channel method. The experiments were conducted up to high-temperature conditions of 610 K at varying equivalence ratios (ϕ = 0.7–1.3) to mimic the conditions of practical application devices. With an increase in the mixture temperature, the laminar burning velocity increases because of the rise in reactant enthalpy. The peak laminar burning velocity is observed at ϕ = 1.1 for all the mixture temperatures, except at 600 K, where the maximum laminar burning velocity is observed for stoichiometric conditions. The minimum temperature exponent exists for a slightly rich mixture condition (ϕ = 1.1). Out of all mechanisms, the laminar burning velocity predictions using the Lawrence Livermore National Laboratory model are consistent with the present data at all mixture temperatures. Normalized sensitivity analysis is analyzed using the Lawrence Livermore National Laboratory mechanism to understand the key reactions affecting the laminar burning velocity of the n-dodecane/air mixture. The chain branching reaction R16: H + O2 <=> O + OH has a major influence on the enhancement of the laminar burning velocity. Reaction pathway analysis is carried out at stoichiometric conditions for mixture temperatures of 400 K and 600 K, where it is observed that the elemental flux of the reaction, converting CO to CO2, gets reduced by 42.91% at the high-temperature condition.

Numerical study of the combustion process and NOx evolution mechanism of ammonia-hydrogen compound fuel engine under different intake conditions

To explore the distinction between generation atmosphere of fuel NOx and thermal NOx in an ammonia-hydrogen compound fuel engine, a numerical calculation model was established based on a detailed ammonia-hydrogen oxidation mechanism. The combustion process and NOx evolution mechanism of the ammonia-hydrogen compound fuel engine under different intake conditions were studied. The researchresults for different equivalence ratios show that the in-cylinder hydrogen volume is the primary factor influencing the initial heat release. When the equivalence ratio is between 0.89 and 1.14, the mixture exhibits a higher combustion rate, leading to a shorter CD and an earlier CA50. At this point, the heat release process closer to TDC contributes improving engine combustion efficiency and indicated efficiency. Therefore, when the equivalence ratio is between 0.89 and 1.00, combustion efficiency is higher than 98 % and indicated efficiency is higher than 43 %, the ammonia-hydrogen compound fuel engine achieves relatively higher economy. Both over-rich and over-dilute mixtures induce an enhancement of fuel NOx, while the higher in-cylinder temperature caused by stoichiometric combustion leads to a boom of thermal NOx. Consequently, the total NOx emission from the ammonia-hydrogen compound fuel engine is higher at equivalence ratios between 0.80 and 1.00, and the NOx emission reaches its peak at an equivalence ratio of 0.89. Analysis of the evolution process of key N components in the cylinder shows that incomplete combustion plays a significant role in fuel NOx emissions, while thermal NOx emissions are mainly influenced by the distribution of in-cylinder components and combustion temperature. Specifically, thermal NOx emissions primarily depend on the in-cylinder components distribution in the narrow equivalence ratio range around stoichiometric ratio, and are significantly affected by in-cylinder temperature under other conditions. The in-cylinder oxygen concentration significantly affects fuel NOx emissions under most operating conditions. Further optimization of intake temperature shows that combustion efficiency exceeds 90 % when the intake temperature is above 280 K. When the intake temperature reaches 310 K, the combustion efficiency reaches up to 98 %, thus an intake temperature of about 310 K is sufficient to meet the need for improving the combustion efficiency of ammonia-hydrogen compound fuel engine. To achieve high efficiency and lower NOx emissions, appropriate lean combustion combined with an intake temperature slightly above room temperature is recommended.

A Comparison Between Conventional and MILD Combustion Processes of Turbulent Stratified Mixtures

ABSTRACT The relative enhancements of volume-integrated burning rate and flame surface area under turbulence and heat release rate contributions due to different combustion and flame propagation modes have been compared between conventional and Moderate or Intense Low Oxygen Dilution (MILD) combustion of stratified mixtures (for a global mean equivalence ratio of 0.8) for the first time using three-dimensional Direct Numerical Simulation (DNS) data. The burning rate enhancement under turbulence is found to be comparable to the enhancement of flame surface area for the conventional stratified flames considered here, whereas the burning rate enhancement is found to be considerably greater than flame area augmentation in the MILD cases analyzed here. It has been found that almost all the heat release rate arises due to the lean-premixed mode of combustion for the conventional stratified flame cases considered here. In contrast, the lean premixed mode of combustion accounts for about 50% of the total heat release rate for the MILD cases where rich-premixed and non-premixed modes of combustion contribute significantly to the overall heat release rate. Under the conditions analyzed here, more than 75% of heat release rate arises from the propagation-dominated regions for both MILD combustion and stratified flame cases, but the trend is stronger in the conventional stratified mixture combustion. More than 80% of heat release rate in the globally lean conventional stratified flame cases considered here originates from back-supported flame propagation, whereas both front and back-supported flame propagation modes have comparable contributions to heat release in the MILD combustion cases. The non-premixed mode of combustion has been found to play a more important role in the MILD combustion cases than in the case of conventional stratified flames. This implies that the closures, which work reasonably well for MILD combustion of homogeneous mixtures, may not be sufficient for modeling of MILD combustion of stratified/inhomogeneous mixtures.

A novel swiss-roll counterflow micro-combustor: Experimental investigation of methane-oxygen flame behavior over time

This study introduces a novel Swiss-roll micro-combustor design that employs a non-premixed counterflow flame for efficient and stable micro-combustion. This design addresses practical system challenges by (1) stabilizing the flame, (2) enhancing heat recovery and gas preheating, (3) aligning gas momentum with the exhaust, and (4) minimizing disruptive fluid motion within the channels. This research investigates the dynamic behavior and combustion characteristics of a methane-oxygen flame within the combustor across a range of equivalence ratios (1.50–3.38). A synergistic approach combining flame dynamics analysis, spectroscopy, and RGB image processing explores the interplay between flame temperature, strain rate, and equivalence ratio. The results demonstrate the effectiveness of the RGB method as a cost-efficient tool for predicting variations in C2∗ and CH∗ radicals and light-intensity radiations. While flame thickness and length exhibit complex dependencies on the fuel-to-oxygen ratio and wall temperature, specific radical emissions vary dynamically with the equivalence ratio. Notably, equivalence ratios of 1.94 and 2.26 exhibit minimal temporal variations in flame properties, suggesting optimal stability and predictability for practical applications. The investigated flame is classified as a “cool flame,” and efficiency declines with richer mixtures due to increased exhaust heat loss and incomplete combustion. This work paves the way for further micro-combustor design optimization and unlocks the potential of non-premixed counterflow flames in diverse micro-scale applications.

The Effect of Combustion Phase According to the Premixed Ethanol Ratio Based on the Same Total Lower Heating Value on the Formation and Oxidation of Exhaust Emissions in a Reactivity-Controlled Compression Ignition Engine

A compression ignition engine generates power by using the auto-ignition characteristics of fuel injected into the cylinder. Although it has high fuel efficiency, it discharges a lot of exhaust emissions such as NOX and PM. Therefore, there is much ongoing research aiming to reduce the exhaust emissions by using the technologies applied in this regard, such as PCCI, HCCI, etc. However, these methods still discharge large exhaust emissions. The RCCI method, which combines the spark ignition method and compression ignition method, is attracting attention. So, in this work, the objective of this study is to numerically investigate the effect of combustion phase according to the premixed ethanol ratio based on the same total heating value in-cylinder by changing the initial air composition on the formation and oxidation of exhaust emissions in the RCCI engine. The heating value of the premixed ethanol ratio varied from 0% to 40% based on the same total lower heating value in-cylinder in steps of 10%. It was assumed that the ethanol introduced into the cylinder through the premixing chamber was evaporated, and the initial air composition in the cylinder was changed and set. It was revealed that when the premixed ratio based on the same total lower heating value was increased, the introduced fuel amount into the crevice volume with advancing the start of energizing timing was decreased, which increased the peak cylinder pressure. In addition, the ignition delay was also longer due to the low cylinder temperature by the evaporation latent heat of the ethanol, which reduced the compression loss, so the IMEP value was increased. The rich equivalence ratio had a narrow distribution in the cylinder, which caused a reduction in cylinder temperature, so the NO formation amount was reduced. The ISCO value increased the increase in premixed ethanol ratio based on the same total lower heating value in-cylinder because the flame propagation of ethanol by combustion of diesel did not work well, and the CO formed by combustion was slowly oxidized due to the cylinder’s low temperature as a result of the evaporation latent heat of ethanol. From these results, the optimal operating conditions for simultaneously reducing the exhaust emissions and improving the combustion performance were judged such that the start of energizing timing was BTDC 23 deg, and the premixed ethanol ratio based on the same total lower heating value in-cylinder was 40%.

Impact toughness and wear resistance of different equivalent ratios of 316 L and 2Cr13 by laser melting deposition on Q235 steel

Impact toughness and wear resistance of different equivalent ratios of 316 L and 2Cr13 by laser melting deposition on Q235 steel

Effect of injection and ignition strategy on an ammonia direct injection–Hydrogen jet ignition (ADI-HJI) engine

High-efficiency, low-emission ammonia-hydrogen engines with low hydrogen energy share (XH2) help promote a carbon-neutral transition in heavy-duty, long-distance transportation. In this study, numerical investigations were carried out on a hydrogen jet ignition (HJI) ammonia engine to study the effects of ammonia port fuel injection (PFI) and ammonia direct injection (ADI) on the engine performance, including combustion and emission characteristics, at XH2 = 3 % with varied spark timing (ST). The results show that the ADI mode has higher volumetric efficiency, lower in-cylinder temperature, and lower heat transfer loss compared with the PFI mode, and more retarded injection can further increase the volumetric efficiency and reduce the temperature. ADI mode results in a more inhomogeneous fuel distribution and a lower local equivalence ratio, with hydrogen consumed earlier than ammonia, potentially resulting in more rapid early-stage combustion. ADI mode with multiple injections is more conducive to engine performance than single injection and can achieve the higher indicated mean effective pressure (IMEP) and indicated thermal efficiency (ITE) than PFI mode. By further optimizing ST, the ADI mode improves ITE by 2.8 % and reduces NO emission by 70 % compared with the PFI mode under acceptable NH3 and N2O emission conditions.

Investigation on varied sewage sludge producer gas and methane blend equivalence ratios operated SI engine intact with Miller cycle strategy

Decentralised power generation through a gasifier-engine genset can reduce both reliance on power grid and pollution. However, the low calorific value of the produced gaseous fuel moderates engine power and efficiency, which is a big challenge for its utilisation. For early and cost-effective solution prediction, a simulation tool of adequate precision can effectively envisage dual-fuel (DF) mode engine performance. Thus, this study simulates DF-SI engines with late inlet valve closures (LIVCs) to improve thermal efficiency using the Miller cycle strategy. Simulation is performed using quasi-dimensional thermodynamic modelling (QDTM). After validating the model using referred experimental results, QDTM was employed to study the parametric impacts of inputs (blends, LIVC and equivalence ratio) variations on performance and emissions response parameters. Power improves by blending sewage sludge-based producer gas with methane. Multi-objective optimisation through the response surface method (RSM) determined the optimum operating parameters as 0.814 equivalence ratio, 68.23% SSPG-blend and 55.9° CA (ABDC) LIVC. Corresponding optimal responses were 5.906 bar IMEP, 3.85 kW BP, 28.6% BTE, 12.596 MJ/kWh BSEC, 0.134 V% CO and 2045.29 ppm NO emissions. ANOVA-based optimal results presented a composite desirability of 0.843 with a 95% confidence level. Conclusively, methane mix and LIVC approach increase the power and efficiency of the DF-SI engine; additionally, optimisation guides to balance power and emission trade-off.

Biosolid Gasification Performance Prediction Using a Stoichiometric Thermodynamic Model.

The gasification process can recover energy from biosolids produced in wastewater treatment. This paper developed a stoichiometric thermodynamic equilibrium model for biosolid gasification based on the biosolid properties, thermodynamic database, and equilibrium constants. If the calculation result showed that the quantity of char was negative, the quantity of char was put to zero, and the simulation was carried out again. The model was first verified by woody gasification under isothermal conditions, and the influence of a given temperature on biosolid gasification was simulated. The model further investigated the effects of different feedstock types, moisture contents, equivalence ratios, and reaction extensions on the adiabatic temperature, exergy efficiency, and syngas properties under autothermal conditions. The four factors were all the main factors for adiabatic temperature. The exergy efficiency depended more on the operation conditions than on the feedstock type. The H2 concentration of the dry syngas in biosolid gasification exhibited a curve both against the given temperature under isothermal conditions and against the moisture content under autothermal conditions.

Experimental and numerical study on the influence of N2/H2 on the laminar combustion characteristics of syngas premixed flames

This paper primarily analyzes the influence of N2 and H2 content on the laminar combustion characteristics of low calorific value syngas, using a constant-volume combustion bomb to measure the laminar combustion velocity (SL) of the fuel and compare it with five commonly used mechanisms. The study reveals that higher N2 content significantly reduces the SL of CO/CH4/CO2 mixed fuels, primarily due to a general decrease in the mole fractions of key intermediates and net reaction rates. Increasing H2 content leads to an increase in the SL of CO/CH4/CO2/N2 mixed fuels. The thermal effect becomes increasingly prominent with the elevation of H2 content, while the proportion of thermal effect initially decreases and subsequently increases as the equivalence ratio rises. With the increase in N2 content, the mole fraction of NO experiences a significant decrease, and the rate of decline in thermal NO production is even faster. Conversely, with the increase in H2 content, the rate of rise in non-thermal NO generation is faster, and the mole fraction of NO tends to increase.

Effects of equivalent ratio and initial temperature on the explosion characteristics of ethanol, acetone, and ethyl acetate

In this paper, the effects of equivalence ratio (0.8–2.0) and temperature (30°C–120°C) on ethanol, acetone, and, ethyl acetate vapors explosion characteristics through experimental and numerical studies were investigated. The explosion overpressure and flame propagation velocity were recorded through the pressure transducer and high-speed camera. The results showed that the flame propagation velocity, peak explosion overpressure, and peak growth rate of explosion overpressure increased first and then decreased with the increase of equivalence ratio. The cracks on the flame surface enhanced with the increase of the equivalence ratio. As the initial temperature increased, peak explosion overpressure, the flame propagation velocity, and peak growth rate of explosion overpressure gradually increased. The sensitivity analysis of laminar burning velocity indicated that with the change of equivalence ratio and initial temperature, the shared elementary reactions that increased the reactivity were H + O2 &amp;lt;=&amp;gt; O + OH, HCO + M &amp;lt;=&amp;gt; H + CO + M, and CO + OH &amp;lt;=&amp;gt; CO2 + H, and the shared elementary reaction that reduced the reactivity was H + OH + M &amp;lt;=&amp;gt; H2O + M. The main factor affecting laminar burning velocity was the mole fraction of H and OH radicals.