Effects Of Equivalence Ratio Research Articles

Experimental research on ignition characteristics of hot jet matched with single-channel wave rotor combustor

An experimental system employing hot jet ignition was used to investigate the effects of hot jet equivalence ratio, jet flow rate, and premixture equivalence ratio on the ignition and flame propagation characteristics of a single-channel wave rotor combustor. The study revealed that the hot jet equivalence ratio and jet flow rate exert a notable influence on the initial flame front position. The ignition delay time for the wave rotor combustor remains approximately 4 ms within the tested parameter range, regardless of variations in the jet conditions. The stable flame propagation velocity primarily depends on the premixture equivalence ratio within the wave rotor channel, with optimal flame propagation achieved at a specific ratio. Additionally, the premixture equivalence ratio inside the wave rotor channel significantly impacts the shape of the flame front.

Effects of thermal pretreatment and equivalence ratio on DME/$${\hbox {O}}_2$$/$${\hbox {O}}_3$$ detonations

Effects of thermal pretreatment and equivalence ratio on DME/$${\hbox {O}}_2$$/$${\hbox {O}}_3$$ detonations

Large eddy simulations of pilot-stage equivalence ratio effects on combustion instabilities in a coaxial staged model combustor

In this paper, the effects of pilot-stage equivalence ratio on combustion instabilities in a coaxial staged model combustor are investigated using the Wall-Modeled Large Eddy Simulation. The global equivalence ratio is maintained constant, and the Stratification Ratio of the first main-stage and the second main-stage is set to 1; the dynamic mode decomposition and system identification methods are employed to analyze the flame dynamics, velocity, heat release rate modes, and flame transfer function (FTF) of the model combustor under different pilot-stage equivalence ratios. The results show that when the pilot-stage equivalence ratio is 0.6, the oscillation amplitude of heat release rate (HRR) exceeds 7.5% of the global average HRR, and the velocity oscillation and the global HRR oscillation in the combustor are coupled. As the pilot-stage equivalence ratio increases to 0.8, the oscillation amplitude of HRR decreases to 2.5%, and the oscillation of velocity and global HRR in the combustor are decoupled. Furthermore, the maximum value of FTF decreases from 3.5 to below 1 with the increase in the pilot-stage equivalence ratio.

Numerical Investigation of Combustion Instabilities in Swirling Flames with Hydrogen Enrichment

This work presents a numerical study on technically premixed, swirl-stabilised flames in the PRECCINSTA model combustor. The employed method, BOFFIN-LES, comprises a fully compressible formulation to study unsteady combustion with thermo-acoustic instabilities. To allow for this, the iso-thermal flows are first investigated, based on which three reacting cases are established. The investigation delves into various aspects including flame topology, flow characteristics, and the related thermo-acoustic and hydrodynamic instabilities are studied and results are benchmarked against available measurement data. The dominant feedback mechanism of the observed thermo-acoustic fluctuations is identified; the evolution of the helical vortex is discussed together with the related flame stabilisation process. Furthermore, the interplay of the thermo-acoustic oscillations, helical structure, and the flame stabilisation process is summarised in the end, with the potential effect of the wall-heat transfer on them discussed. This work establishes that the Large Eddy Simulation (LES) effectively captures the iso-thermal flow dynamics and the flame topology under various operating conditions, with a good prediction of the thermo-acoustic frequencies in all the cases. The dominant driving mechanism of the observed thermo-acoustic fluctuations was identified as a combined effect of equivalence ratio and velocity fluctuations in all the cases investigated. The effect of Hydrogen enrichment on modifying the flame topology and changing the thermo-acoustic instability features are well predicted by the simulations. Moreover, different modes of the helical vortex are detected, and their periodic excitement, evolution, and effect on flame stabilisation are discussed in great detail. To conclude, this LES-based investigation offers valuable insights into the complex interplay of unsteady combustion, acoustic fluctuations, flow dynamics, and solid boundaries within swirling flames subjected to unsteady conditions.

Techno-economic assessment of sugarcane bagasse pith-based briquette production and performance analysis of briquette feed gasifier-engine system

Utilizing agriculture co-products and agricultural residues directly leads to Energy, Economic, and Environmental sustainability. Sugar production industries produce a considerable amount of sugarcane bagasse (SB) as a co-product, whereas SB is used in paper-mill sectors, which have a large amount of waste as sugarcane bagasse pith (SBP). In this view, the novelty of the present study aims to ensure the economic viability of the SBP briquette production plant, after that, briquette-based producer gas (PG) generation and application to compression ignition (CI) engine for diesel substitution. The economic analysis includes the Net Present Value (NPV) and Profitability Index (PI) for the feasibility check. And gasifier-engine analysis includes the effect of gasification equivalence ratio (GER), engine compression ratio (CR), and load on engine brake thermal efficiency (BTE), diesel saving, Sound, Exhaust gas temperature (EGT), and emissions (CO, HC, CO2, NOx). Further, operating variables were optimized with the desirability approach of Response surface methodology (RSM). In the result, NPV and PI values were found to be Rs 49,64,379.5 (≈0.06 million USD) and 1.98, respectively. However, the economic feasibility of the plant is sensitive to capital cost, briquette market price, and discount percentages. Regarding gasifier-engine performance, the maximum diesel substitution was found to be 66.15% at dual fuel (DF) mode engine run. RSM-based optimization result showed the optimum operating setting of 0.10 GER, 16 CR, and 9.93 kg load at 1500 rpm with a composite desirability of 0.798. Accordingly, at optimal input parameters, the magnitudes of engine performance as BTE, Sound, CO, HC, CO2, and NOx were found to be 27.18%, 91.21 db, 0.10%vol., 53.19 ppm, 2.33%vol., and 8.43 ppm respectively. Thus, the higher value of the economic index and substantial amount of diesel fuel saving through the gasifier-engine system ensures the economic feasibility of briquetting and power generation technology.

An Experimental and Kinetic Study of Phenylacetylene Ignition at High Temperatures

ABSTRACT Phenylacetylene plays a critical role as an intermediate in PAH formation in hydrocarbon flames. In this work, the autoignition characteristics of phenylacetylene were investigated behind reflected shock waves. Ignition delay times were measured at temperatures ranging from 1228 to 1813 K, pressures of 2, 4, and 10 atm, equivalence ratios of 0.5, 1.0, and 2.0, as well as fuel mole fractions of 0.1% and 0.2%. The effects of temperature, pressure, equivalence ratio, and mole fractions on ignition delay time were investigated, and quantitative relationships were obtained by regression analysis of the experimental data. A detailed oxidation mechanism of phenylacetylene based on NUIGMech1.1 was proposed and verified using ignition data. Reaction pathway and sensitivity analyses have been carried out to investigate the significant reaction pathways in the ignition process and key reactions that affect the ignition delay time. The addition reactions by O and OH species contribute significantly to phenylacetylene consumption and promote fuel ignition. Finally, a comparison of the ignition delay times of ethylbenzene, styrene, and phenylacetylene was conducted in this study, and kinetic analyses have been conducted to investigate the impact of different side chains attached to aromatic rings on the ignition of these C8 aromatics.

Experimental investigation and optimization of the gasification parameters of macadamia nutshells in a batch-fed bubbling fluidized bed gasifier with air preheating

Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas, which is considered as renewable energy. This work investigated the gasification of macadamia nutshells in air-preheated, batch-fed fluidized bed gasifier. The study conducted a parametric analysis to assess the effect of equivalence ratio (ER) and air temperature on the gasifier temperature profile and its performance based on gas composition, higher heating value (HHV), and gas yield. The research was conducted within the range of 0.15–0.35 for the ER and 25–825 °C for the air temperature. Multi-objective numerical optimization was conducted using response surface methodology (RSM). From the parametric study, a distinct temperature profile was observed along the gasifier height, with the peak temperature near the top of the fluidized bed section and the lowest temperature at the top of the gasifier. Air preheating mostly favored gasification temperature at the lower part of the gasifier and showed rare significance at the top. No improvement in gasifier performance was observed beyond an air temperature of 620 °C, which was identified as the ideal air-preheating temperature. Analysis of variance (ANOVA) revealed that the ER was the most influential parameter in the production of combustible gasses, syngas HHV and gas yield. Air preheating did not have a significant effect on methane production and gas yield. The most optimal values for ER and air temperature were obtained as 0.195 °C and 620 °C, respectively, producing optimal values of 9.54, 14.65%, 2.03, 4.02 MJ·Nm−3, and 1.82 Nm3·kg−1 for hydrogen, carbon monoxide, methane, HHV, and gas yield, respectively.

Experiment and Numerical Studies of the Effect of Equivalent Ratio on Combustion Characteristics in Fluidized Bed Gasifier

The effect of equivalent ratio on fluidized bed gasifier on using kernel mixed palm cake as feedstock was studied experimentally and numerically. A 3-D numerical model of the reactor, similar to the experimental setup, was created using the commercial computational fluid dynamics (CFD) software ANSYS 2019 (Fluent). The fuel feed rate was fixed at 3 kg/hour and the mass flow rate of the air was varied, setting it to equivalent ratios (ER) of 0.1, 0.3, 0.5, and 0.7. The axial temperature profile in the reactor was compared between experimental measurements and numerical simulations and a good agreement was found. Carbon monoxide and volatiles increased when the equivalent ratio decreased, according to the simulations. It was found that ER = 0.1 and ER = 0.3 are suitable equivalent ratios, although the former would not give continuous combustion due to too low reactor temperature.

Investigation of hydrogen production via waste plastic gasification in a fluidized bed reactor using Aspen Plus

Plastic waste-to-energy conversion via gasification is a promising method for hydrogen production. In this study, the effects of waste plastic type, equivalence ratio, operating temperature and pressure on the hydrogen production from waste plastics in a fluidized bed reactor were investigated. A precise model of the air gasification process of five different types of waste plastics was developed using modules available in Aspen Plus. Following the model validation, a parametric study was conducted by varying the temperature in the range of 600 °C–1200 °C, the equivalence ratio between 0.05 and 0.50, and the pressure between 1 bar and 50 bar. This study provides valuable information on the impact of different process parameters on the air gasification of various waste plastics which has not been reported extensively. The conversion behaviours of air gasification process for waste plastics were characterized based on syngas composition, syngas lower heating value, hydrogen yield and cold gas efficiency. The simulation results for hydrogen production, which ranged from 15.33 Nm3/ton feed to 284.40 Nm3/ton feed for all plastics, were found to be consistent with experimental results. As a result, the optimal conditions for achieving maximum hydrogen yield in the waste plastic gasification process have been determined and reported.

Experimental and kinetic modeling study of the autoignition and oxidation of ammonia/ethane mixtures in a rapid compression machine and a jet-stirred reactor

Ignition delay times and speciation data of ammonia/ethane (NH3/C2H6) fuel blends were measured in a rapid compression machine (RCM) and in a jet-stirred reactor coupled with molecular beam mass spectrometry (JSR-MBMS), respectively. Specifically, the RCM experiments were conducted at elevated pressures of 20 and 40 bar, intermediate temperatures between 890 and 1110 K, three equivalence ratios of 0.5, 1.0 and 2.0 and for three C2H6 mole fractions from 1% to 10%. Besides, the JSR measurements were conducted at atmospheric pressure, intermediate temperatures between 700 and 1180 K, three equivalence ratios of 0.5, 1.0 and 2.0 and three C2H6 mole fractions from 10% to 50%. The experimental results demonstrate that adding C2H6 into NH3 leads to a more reactive mixture. A kinetic model from our recent work on ammonia/ethanol fuel blends (M. Li et al., Proc. Combust. Inst., 2022) has been updated and validated with the new data obtained in this work. The updated model (PTB-NH3/C2 mech) can reproduce the effects of ethane fraction and equivalence ratio on IDT/speciation and show an overall satisfactory agreement between experimental results and predictions. Based on the kinetic analyses, for all conditions investigated in this study, the generation of OH radicals from HO2 and H radicals dominates the characteristic of the auto-ignition process in the RCM and the NH3 consumption process in the JSR, respectively. Apart from that, the addition of ethane provides additional OH from a relatively low temperature (e.g., around 850 K in a JSR condition) and triggers the interactions between hydrocarbon and ammonia systems, e.g., the reactions of C2H6/C2H4/CH3+NH2, which play an important role in the combustion of ammonia.

High temperature oxidation of residual oil pyrolysis intermediates for modeling gasification and combustion processes

Developing chemical kinetic models for residual oil pyrolysis, gasification, and combustion is very challenging due to the large number of components and molecular complexity. This study provides experimental data for model development and validation for two residual oils, heavy fuel oil (HFO) and vacuum residual oil (VRO). This study aims to identify and quantify the HFO and VRO pyrolysis intermediates and validate an oxidation chemical kinetic model of the pyrolysis intermediates to provide data for future residual oil model development using hybrid chemistry (HyChem) and functional groups for mechanism development (FGMech) approaches. The pyrolysis experiments were conducted in a bench-scale tubular reactor at atmospheric pressure and a temperature of 1273 K. Detailed compositions of the yields from the pyrolysis of HFO and VRO were analyzed using gas chromatography-flame ionization detection (GC-FID) for the gas yields and gas chromatography-mass spectrometry/flame ionization detection (GC–MS/FID) for the liquids. Elemental analysis was conducted for the solid residuals. The experiment results show similar pyrolysis products from HFO and VRO. A surrogate of major components of the gas products and representatives of benzene and naphthalene derivatives (major compounds identified in liquid products) of the liquid products was formulated and its chemistry was studied by measuring ignition delay times (IDTs) in a shock tube. IDT measurements were conducted for stoichiometric and rich (ϕ = 1 and 3) mixtures, pressures of 20 and 40 bar, and diluents of nitrogen and carbon dioxide. Brute force IDT sensitivity analyses were used to study the effect of pressure, equivalence ratio and diluents on the reactivity of the mixture.

Experimental studies on the OH∗ chemiluminescence and structure characteristics in NH3/H2 and NH3/cracked gas swirl flames

Ammonia (NH3) has been gaining popularity as a carbon-free alternative fuel in recent years. OH∗ chemiluminescence is a promising method to study the structure of ammonia flames, but research on this aspect is still lacking. In this study, the OH∗ chemiluminescence distributions and structure characteristics in NH3/H2 and NH3/cracked gas swirl flames are experimentally investigated. The OH∗ distributions of NH3/H2 and NH3/cracked gas under different addition levels and equivalence ratios are compared. The results show that the increase of equivalence ratio and hydrogen doping level significantly increased the OH∗ chemiluminescence peak of NH3/air swirling flame. Especially in fuel-lean flames, the equivalence ratio effect is greater than the NH3 dilution effect, while the two effects are comparable in equivalence and fuel-rich conditions. The stretching effect of NH3/cracked gas is stronger, and the flame width is narrower than that of NH3/H2 flame, but the peak value of OH∗ radiation is higher.

Effect of equivalence ratio and mixing time on combustion of ammonia/oxygen/argon mixture using a constant volume combustion chamber with sub-chamber

Effect of equivalence ratio and mixing time on combustion of ammonia/oxygen/argon mixture using a constant volume combustion chamber with sub-chamber

The turbulent flame structure in a steam diluted H2/Air micromix flame

In order to safely organize hydrogen flame with low NOx emission in traditional gas turbines and industrial burners, an attractive combustion technology is the steam diluted micromix combustion technology. The effects of equivalence ratio (φ), steam dilution ratio (D) and nozzle diameter (d) on the turbulent flame structure in a steam diluted H2/air micromix flame were investigated experimentally with a 10 kHz high-speed OH∗ chemiluminescence imaging system to detect the instantaneous flame zone. With the increase of equivalence ratio (φ) or the decrease of steam dilution ratio (D), the overall OH∗ signal intensity and the area of OH∗ signal increase. The maximum OH∗ signal intensity along the axial direction (Z) is distributed far from the nozzle outlet with the increase of nozzle diameter (d). Two types of flame were found for time-averaged images, namely the anchored flame and the lifted flame. And the increase of hydrogen velocity could lead to the changing of flame from anchored to lifted due to lower uniformity of the fuel-air mixture at the nozzle outlet. The instantaneous flames for larger nozzle diameter appear as “M” or “V” shape, and the changing of flame shape indicates an unstable combustion. This was further discussed with the OH∗ spatial distribution uniformity (SDU) and its variation determined by the coefficient of variation (CV) parameter.

Experimental study on the explosion characteristics of NH3/DME/air mixtures

Co-firing ammonia (NH3) fuel with dimethyl ether (DME) is a promising approach of achieving clean combustion. However, the fundamental explosion characteristics of NH3/DME blends have not been well understood. This paper presents an experimental study of the explosion characteristics of NH3/DME blends using a spherical constant-volume combustion chamber. The effects of equivalence ratio (ϕ = 0.7–1.5), initial pressure (Pu = 0.05–0.5 MPa), and DME fraction (XDME = 0–100%) on the explosions were examined. The results show that peak explosion pressure Pmax, maximum pressure rise rate (dP/dt)max, and deflagration index KG, vary non-monotonically with equivalence ratio, and reach peak values at around ϕ = 1.1–1.2. DME addition has a positive effect on explosion intensity. Both (dP/dt)max and KG show a linear increase trend with increasing DME, while the growth rate of Pmax decreases with DME fraction. The relatively higher increase in Pmax between 0 %DME and 20 %DME is mainly due to greater heat release. Pmax increases with increasing initial pressure, and this is because of the increase in mixture mass promoting the heat release, and the enhanced possibility of effective collision between molecules of gas mixtures. The influence of initial pressure on (dP/dt)max and KG depends on the equivalence ratio. Both (dP/dt)max and KG show a linear increase with increasing initial pressure at ϕ = 1.0 and 1.5, whereas they are insensitive to initial pressure at ϕ = 0.7. This is because the decrease in laminar burning velocity leads to a significant increase in explosion time at ϕ = 0.7 compared to ϕ = 1.0 and 1.5. In addition, the actual explosion pressure is closely associated with non-negligible heat loss during flame propagation, and the heat loss decreases with the addition of DME, but increases with increasing initial pressure.

Explosion dynamics of premixed LPG/H2 fuel in a confined space

To reveal the impact law of H2 on the kinetics of LPG explosion reaction, a list of explosion experiments were conducted in a 10 L duct with LPG/H2 as the research object. The influence of H2 volume fraction on the explosion characteristics of LPG was investigated, and analyzed the combustion mechanism of mixed-gas. Results indicate that the flame development of LPG/H2 mixed under different RH conditions is divided into four different development modes. The Pmax increase, and the explosion relief pressure decrease as the RH elevates. The effect of equivalence ratio on the Thermo-Diffusive instability and Darrieus-Landau instability of LPG/H2 mixture is large. Under the same conditions, there is a noticeable discrepancy in the flame duration and explosive pressure duration. The chain reaction (R2: H2 + OOH + H, R3: H2 + OHH2 + OH), which produces a significant amount of H, OH important radicals and boosts the reaction activity, is the principal way that hydrogenation affects the reaction of LPG/H2 gas combination. The impact of H2 on LPG in terms of reaction mechanism is explained and confirmed by the fact that hydrogenation encourages the rise of the sensitivity coefficient of the fundamental reactions of the LPG/H2 mixture explosion.

Solar-assisted gasification of agriculture residues for green hydrogen production

The present study proposes a novel way of green hydrogen (H2) synthesis by steam – air biomass gasification assisted by solar energy. In view of environmental problems arising due to stubble burning of agricultural residues in India, bagasse, rice straw and wheat straw are selected as biomass samples. Biomass gasification process is simulated in ASPEN Plus software and then effects of gasification temperature (Tg), equivalence ratio (ER) and steam – to – air mass ratio (S/A) on molar H2 content of producer gas (MHC), higher heating value of producer gas (HHV) and cold gas efficiency (CGE) are studied. The process is optimized using Response Surface Methodology (RSM). It is found that Tg=800 °C – 900 °C, ER=0.2 and S/A=1.8–2.2 are optimum ranges to maximize MHC, HHV and CGE, yielding about 40 % MHC, 6 MJ/kg HHV with 80 % CGE. At optimum operational conditions, steam required for steam-air gasification of a 15 kWth gasifier is calculated. This steam is superheated by solar tower. Total heliostat area requirement is calculated to be 40 m2–65 m2 for different input temperatures of superheated steam (Ts) during steam-air gasification.

A New Approach towards Production of Syngas as a Precursor for Manufacturing Ammonia

Abstract: In this study, rice husk as biomass undergoes drying and gasification process to produce syngas. Moisture from biomass is removed to get dry biomass which is then gasified at 700℃. Ash is produced which is separated through separator and product gas is passed to heat exchanger to reduce its temperature. Finally, syngas is obtained which is a precursor for production of ammonia. The process simulation is done using Aspen Plus software. The model is validated and the effect of gasification temperature, gasification pressure, and equivalence ratio (ER) on gas component composition, gas yield, and gasification efficiency was investigated using Aspen Plus simulation.

An Investigation into Burner Configuration Effects on Premixed Flame Characteristics for LPG Diluted with CO<sub>2</sub>

Meeting stringent emission regulations, the demand for environmentally friendly fuels is increasing by the day. Alternative fuel must be burned alongside conventional fuel to increase the availability of such clean energy sources. The current experimental study investigates the characteristics of the premixed LPG flames with CO2 dilution in tube swirling and non-swirling burners. The study including testing the effects of equivalence ratios, φ, (0.8, 1, 1.2, & 1.4), CO2 dilution ratios (0%, 5%, 7.5%, & 10%), and aspect ratio of the non-swirling burner (2, 4, 6, 8, & 10). Two swirling burners with swirl number was tested, namely 0.78 & 0.48. The dilution of CO2 has been observed lengthens the flame, particularly at higher equivalence ratios and/or flow rates since there is more than one influence, they all agree on a similar influence on flame height. The flame shortens clearly when using a swirling burner. Besides, when increasing the swirl number, the flame height increases slightly. Also, the swirling burner divided the flame's inner core into segments equal to the number of swirl vanes, and a flower-shaped flame was generated at low flow rates. The burner’s aspect ratio affects flame height insignificantly. Flame stability limits increase for a higher equivalence ratio and it enhances due to CO2 addition. The LPG-CO2/air mixture has an improved reply to beat flame flashback. The addition of CO2 expands the flow rate of stable flame by about 40% and 25% for φ = 1 and 1.2 respectively. Utilizing a swirling burner improves flame stability greatly. The limit between flashback and blowout increased by about three times as a result of using a swirling burner.

Experimental study on effect of temperature and equivalence ratio on biomass syngas generation for fluidized bed gasifier techniques

ABSTRACT This paper presents a comparative study of selected woody biomass for the potential of fuel gas generation that can be used for heat and power generation using a Fluidized Bed Gasifier (FBG). The characteristics of produced energy gas using the thermochemical Bubbling Fluidized Gasification Technique for selected woody biomass feedstock materials were studied for selected temperatures. Initially, the CFD analysis has been implemented to determine the feasible equivalence ratio (ER) for the selected biomasses. Using CFD ANSYS solver studied gas-solid interaction and gasification process inside a fluidized bed biomass gasifier. Experimental investigations were conducted on the FBG reactor for a feeding rate of 10 kg/hr of biomass materials. Experimental investigations were conducted on the FBG reactor for a feeding rate of 10 kg/hr of biomass materials. The work characteristics of produced gas were investigated by the experimental process for bagasse, groundnut shell, and wooden shavings as feedstock biomass materials for the gasification bed temperature at 500ºC, 550ºC, and 600ºC and Equivalence Ratio (ER) ratio of 0.30. Air was employed as a gasifying agent, and sand with limestone was used as the fluidized bed material. The results show that the fluidized bed has higher temperatures of 600ºC and above, generating higher Calorific Value (CV) syngas. Among all three feedstocks, groundnut shells produced gas HHV of 4.21 MJ/m3. The lowest HHV for bagasse at 500ºC of 3.01 MJ/m3. The effect of bed temperature on Carbon Conversion Efficiency (CCE) shows maximum CCE for bagasse is 60.86%, noted at 550ºC, and the minimum for wooden shaving at 550ºC is 57.69%.