Influence Of Equivalence Ratio Research Articles

Effect of equivalence ratio on gas distribution and performance parameters in air-gasification of asphaltene: A model based on Artificial Neural Network (ANN)

Air-gasification of asphaltene was carried out in a bench scale fluidized bed. A neural network model was also developed to study the influence of equivalence ratio (ER) on gas distribution, lower caloric value (LHV) of producer gas, and performance indicators (char conversion and cold gas efficiencies). The contents of CO and H2 were initially increased from 53.2 to 55.4 vol% and 35.4 to 37.6 vol% as ER increased to 0.35, and then decreased to 43.3 vol% and 27.7 vol% at ER of 0.5, respectively. The results also indicated that the LHV of the produced syngas was significantly decreased with ER increasing because of more oxidation reactions at higher ERs.

Combustion characteristics of natural gas injected into a constant volume vessel

The combustion characteristics of injected natural gas based on experiments were carried out in a constant volume vessel. The influences of equivalence ratio, temperature and premix ratio on the flame morphology and combustion characteristics were analyzed. The flame front is wrinkled and twisted during the flame propagation, which shows the extreme randomness of injection combustion caused by the strong turbulence. The maximum pressure and maximum heat release rate of injection combustion are larger than premixed combustion, with less time reaching the maximum pressure, according to the progress of the pressure in the vessel. The initial and main combustion durations of the injection combustion are also shorter than that of premixed combustion.

Influences of equivalence ratio, oxygen concentration and fluidization velocity on the characteristics of oxygen-enriched gasification products from biomass in a pilot-scale fluidized bed

The influences of equivalence ratio (ER), oxygen concentration (OC) and fluidization velocity (FV) on the gasification performance in a pilot-scale fluidized bed with capacity of 1 ton biomass (the mixture of agricultural residue) per day were investigated using oxygen-enriched air as gasification agent and high-alumina bauxite as bed material. The characteristics of syngas (lower heating value (LHV), gas yield (Y), carbon conversion (CC) and cold gas efficiency (CGE)), bio-char (LHV and Proximate analysis) and tar (tar yield and LHV) were used to evaluate the gasification performance in this study. The results showed that 0.161 was the optimal ER due to the high quality of syngas produced and relatively lower tar generation with ER changing from 0.115 to 0.243 at OC ≈ 40% and FV ≈ 1.20.29.7% was the optimal OC due to the highest Y and CC and relatively low tar generation when OC varied from 21% to 44.7% at ER ≈ 1.40 and FV ≈ 1.15. Although higher FV could improve syngas quality, it also resulted in the higher tar yield and heavier wear, therefore, the optimal gasification performance was achieved at moderate FV (FV = 1.13). This study proved that oxygen-enriched gasification in a large-scale fluidized bed was an effective option to produce gaseous biofuels with high quality.

Gasification of Furniture Waste Sawdust in a Cyclone Gasifier

Sawdust is one of the major biomass that was produced over 1 million ton per year in Thailand. A large amount of sawdust can be used as renewable energy. Gasification is one of the high-efficiency processes to convert biomass to the gaseous product. Sawdust is suitable to be converted to the gaseous product due to its high proportion of volatile (73%). In this work, sawdust thermal conversion was investigated by using a stairmand type cyclone gasifier with 100 mm diameter. The operation of the cyclone with short residence time and high efficiency of particulate separation from the gaseous product is suitable for a small particle like sawdust. The influences of equivalence ratio (0.15-0.60) and reactor temperature (700°C, 800°C and 900°C) on the waste conversion performance were determined. The gas composition (CO, CO2, CH4, H2, and CnHm), carbon and hydrogen conversions, lower heating value and cold gasification efficiency were reported. The data analysis indicated the optimum equivalence ratio is 0.45. Excessively lower or higher equivalence ratio negatively affected the gas composition and heating value of gaseous product. The optimum of reactor temperature is 900°C. The lower temperature also adversely affected the gaseous product, conversion of carbon and hydrogen. The lower heating value of product gas is range from 0.95-3.45 MJ/m3 and the cold gasification efficiency is range from 28-68%. The optimal condition of sawdust gasification in cyclone gasifier is equivalence ratio of 0.45 and temperature of 900°C at which total carbon and hydrogen conversionsare 90% and 60%, respectively.

Study on laminar combustion characteristic of low calorific value gas blended with hydrogen in a constant volume combustion bomb

Abstract In this paper, the laminar combustion velocity of low calorific value gases blended with hydrogen was experimentally studied in the constant volume combustion bomb. An experimental system of constant volume combustion bomb was set up, and the variation trend of laminar flame velocity of low calorific value blended hydrogen was analyzed under different initial conditions. The experimental results show that increasing the initial pressure will reduce the laminar combustion velocity of the flame, while increasing the initial temperature will increase the laminar combustion velocity of the flame. With the increase of hydrogen ratio, the laminar combustion velocity of flame and instability of flame increases. The influence of equivalence ratio on laminar combustion velocity of flame is quite complex, generally, the burning speed of the rich mixture is greater than that of the lean mixture. This research can provide experimental basis for the design and development of low calorific value gas blended with hydrogen engine.

Influence of equivalence ratio on the propagation characteristics of rotating detonation wave

An experimental study on a rotating detonation engine was carried out to analyze the initiation and propagation characteristics of rotating detonation wave. Propellants were hydrogen/air mixture and ignited by a pre-detonator. The rotating detonation wave was initiated and propagated successfully with various equivalence ratios. Piezoelectric pressure transducers were used to monitor high-frequency pressure signals. Experimental results indicated that after the ignition, the rotating detonation wave was not initiated directly. With the increase of the equivalence ratio, the formation time of rotating detonation wave decreased rapidly. Meanwhile, the rotating detonation wave sequentially exhibited three propagation modes: dual-wave to single-wave transition mode, single-wave with the propagation direction reversal mode, and single-wave one-way mode. The maximum propagation frequency and velocity of the rotating detonation were obtained at the equivalence ratio of 1.0, while the minimum frequency fluctuation was obtained at the equivalence ratio of 0.89. In addition, the rotating detonation wave height and the bending angle β of the oblique shock wave were obtained. This research determined the boundary of the stable propagation modes of rotating detonation waves and found that their frequency fluctuations substantially increase when the equivalence ratio is below about 0.7.

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

This paper is an experimental study of the kinetics of gasification of olive kernel by using a thermogravimetric fluidized bed reactor technique. Gasification of ‘as received’ and torrefied olive kernels were investigated in a lab-scale bubbling fluidized bed gasifier, operating at up to 3.2 kg/h. The effect of bed temperature between 550 and 750 °C in 50 °C increments on the gasification product gas at mass-based equivalence ratios of 0.15 and 0.2 was studied. To explore the potential of torrefied biomass, the gasification results were compared to that of the ‘as received’ biomass. The product gas from torrefied biomass produced higher H2, CO and CH4 concentrations at identical oxidant flow rates in addition to higher cold gas efficiency and higher product gas heating value. The influence of equivalence ratio in gasification was also investigated at reactor temperatures of 750 °C and five equivalence ratios (0.15, 0.2, 0.25, 0.3, and 0.35). The results revealed that the torrefied biomass has the highest HHV at an equivalence ratio of 0.2 with a value of 6.09 MJ/Nm3, while ‘as received’ biomass 4.72 MJ/Nm3. Kinetic experiments under isothermal conditions were performed for the gasification of the materials in continuous mode. A mass balance model was successfully used to provide the capability of separately determining the rate constant of the reactions taking place. The kinetic parameters were calculated by a first order reaction model giving activation energies for ‘as received’ olive kernels of 84 kJ/mol and for torrefied olive kernels of 106 kJ/mol.

Study on Gasoline-Air Mixture Deflagration Flame with Different Equivalence Ratios in a Closed Vessel

ABSTRACTAn experimental investigation was carried out on the influence of equivalence ratio on gasoline-air mixture deflagration in a closed vessel. High-speed flame images, flame illuminance, illumination duration, overpressure and reaction produces were recorded for equivalence ratios ranging between the flammable limits. Efforts were made to explore the potential relationships between the visual character presented on the flame images and the deflagration parameters, e.g., the equivalence ratio, the flame duration, and the maximum overpressure. Results show that the gasoline-air mixture presents a smooth spherical flame with lean fuel, a spherical cellular flame with rich fuel, and a curled flocculent flame with very rich fuel. The three flame patterns could be quantitatively identified by calculating the edge pixel amounts and the average b* value (in a Lab color space) of the flame images. The maximum flame illuminance, illumination duration, reaction products, rate of pressure rise, and maximum pressure showed a discriminating value and variation trend versus equivalence ratio under different flame patterns. The rich flame could be considered as the most dangerous flame regime among the three because of its fastest pressure rising speed and highest maximum overpressure. The result is of value to the fundamental research as well as the video-based flame detecting technology.

Influence of equivalence ratio on plasma assisted detonation initiation by alternating current dielectric barrier discharge under rich burn condition

In order to study the effect of different equivalence ratios on plasma assisted detonation initiation under a rich burn condition, a loosely coupled method was adopted to simulate the detonation formation by alternating current dielectric barrier discharge in a hydrogen–oxygen gas mixture with different equivalence ratios. The spatial and temporal evolution of discharge products were analyzed first. Then, the species distribution, Mach number, thrust wall pressure, and whole history of detonation formation were examined in detail. Results showed that the shapes of the temporal and spatial distribution of discharge products do not change when equivalence ratio varies in one discharge cycle. However, due to the variation of the percentage of fuel and oxidizer, and its impact on the discharge elementary reactions, the number density of every key active particle declines while the decline amplitude decreases when equivalence ratio rises. Although the magnitudes of species concentration are not altered by the plasma, the reacted region extends towards the downstream flow more quickly. The influence of equivalence ratio on plasma assisted detonation initiation becomes remarkable until late in the subsonic stage of the flowfield evolution process in the combustor under a rich burn condition. Furthermore, a larger equivalence ratio leads to a better accelerating effect of the plasma. Through analyzing the dynamic process of thrust wall pressure, it is also found that the DDT process is expedited more notably under a larger equivalence ratio, yet the magnitude of pressure is independent of the plasma. The provision of active particles for the combustion reaction by the plasma and its dilution effect on the fuel are the two intrinsic reasons for the reduction of DDT time and distance and the increase of this reduction degree, when equivalence ratio rises.

Operability Limits of Tubular Injectors With Vortex Generators for a Hydrogen-Fueled Recuperated 100 kW Class Gas Turbine

Abstract Vortex generators are known to be effective in augmenting the mixing of fuel jets with air. The configuration investigated in this study is a tubular air passage with fuel injection from one single orifice placed in the side wall. In the range of typical gas turbine combustor inlet temperatures, the performance vortex generator premixers (VGPs) have already been investigated for natural gas as well as for blends of natural gas and hydrogen. However, for highly reactive fuels, the application of VGPs in recuperated gas turbines is particularly challenging because the high combustor inlet temperature leads to potential risk with regard to premature self-ignition and flame flashback. As the current knowledge does not cover the temperature range far above the self-ignition temperature, an experimental investigation of the operational limits of VGPs is currently being conducted at the Thermodynamics Institute of the Technical University of Munich, Garching, Germany, which is particularly focused on reactive fuels and the thermodynamic conditions present in recuperated gas turbines with pressure ratios of 4–5. For the study presented in this paper, an atmospheric combustion VGP test rig has been designed, which facilitates investigations in a wide range of operating conditions in order to comply with the situation in recuperated microgas turbines (MGT), namely, global equivalence ratios between 0.2 and 0.7, air preheating temperatures between 288 K and 1100 K, and air bulk flow rates between 6 and 16 g/s. Both the entire mixing zone in the VGP and the primary combustion zone of the test rig are optically accessible. High-speed OH* chemiluminescence imaging is used for the detection of the flashback and blow-off limits of the investigated VGPs. Flashback and blow-off limits of hydrogen in a wide temperature range covering the autoignition regime are presented, addressing the influences of equivalence ratio, air preheating temperature, and momentum ratio between air and hydrogen on the operational limits in terms of bulk flow velocity. It is shown that flashback and blow-off limits are increasingly influenced by autoignition in the ultrahigh temperature regime.

Effects of CH4 Content on NO Formation in One-Dimensional Adiabatic Flames Investigated by Saturated Laser-Induced Fluorescence and CHEMKIN Modeling

Experiments applying saturated laser-induced fluorescence (LSF) technology were performed focusing on the influence of equivalence ratio, syngas mixture contents, on NO formation in H2/CO/CH4/CO2/N2/O2 premixed flat flames supplied by a heat flux burner. Experimental data were extracted to validate calculation by CHEMKIN software. Both experiments and CHEMKIN calculation draw one conclusion that NO mole fraction in CH4–air flame peaks at stoichiometric and ϕ 1.3, due to thermal NO and prompt NO routes. All mechanisms applied can well-predict the NO mole fraction at the fuel lean side but failed at the fuel rich side. NO mole fraction in syngas flame is propotional to CH4 ratio as shown in the experimental data, but all the mechanisms failed to predict it with some even having a wrong tendency. A rate of NO production and sensitivity analysis suggests that thermal and prompt NO routes play different roles in each mechanism, and modifications to mechanisms are required to improve NO concnetration prediction...

リーンバーンエンジンにおける当量比の変化が燃焼期間に及ぼす影響

リーンバーンエンジンにおける当量比の変化が燃焼期間に及ぼす影響

Numerical simulation of imbert biomass gasifier to select the feedstock available in remote areas

The performance of a gasifier which is designed for a particular feedstock varies whenever the feedstock is changed. Moreover, to implement the biomass gasification technology in remote places, the performance of existing gasifier should be analysed for its dimensional suitability to work with different feedstock which are available in such locations. Even though, the species transport approach is more appropriate to model the gasification processes, it was not used to analyse all the zones of a gasifier. Hence, in this work, a numerical study was carried out with species transport model by considering all the four zones of a gasifier. This model uses gasification reactions with the corresponding pre‐exponential factor and activation energy to check the performance of a biomass gasifier. Different feedstocks such as coconut shell, rice husk, cow dung, rubber wood and rubber seed kernel shell that are commonly available in the selected region were used in this study. The influences of equivalence ratio on the composition and higher heating value of producer gas, and the temperature distribution inside the gasifier were been studied. Both the experimental and numerical studies demonstrate the best performance when the equivalence ratio is close to 0.25. Among the locally available biomasses, the producer gas from rubber seed kernel shell has the calorific value of 6.08 MJ/Nm3 and therefore it can be used as feedstock in gasifier which is designed for woody biomass. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 708–716, 2017

Hydrogen-rich gas from gasification of Portuguese municipal solid wastes

Gasification has been identified as a promising method of municipal solid waste (MSW) conversion to energy due to its pollution minimization effects and high overall efficiency. Recent studies have been carried out to produce hydrogen through MSW gasification with promising results. Despite this, it is still necessary to develop mathematical models able to assist the advance of this technology and to make way for large-scale commercialization.A previously developed and validated numerical model was used to predict and analyze the viability of hydrogen-rich gas generation from MSW gasification in a semi-industrial fluidized bed gasifier. Influence of equivalence ratio, carbon-dioxide-to-MSW ratio, steam-to-MSW ratio, reactor temperature and catalyst used was investigated. The content of hydrogen in the generated gas increased up to 40% with the presence of NiO/MD catalysts, while reducing the tar content and increasing the gas yield. Finally, to assess the capabilities of the Portuguese wastes results were compared with previously studied Portuguese biomass substrates.

1514 フリッカリング火炎の変動特性に及ぼす当量比と周囲流の影響(OS2-3 熱流体の可視化と計測)

1514 フリッカリング火炎の変動特性に及ぼす当量比と周囲流の影響(OS2-3 熱流体の可視化と計測)

The explosion characteristics of methane, hydrogen and their mixtures: A computational study

The maximum pressure rise rate during gas explosions in enclosures and the deflagration index are important explosion characteristics of premixture. They can be used to quantify the potential severity of an explosion. However, there are large discrepancies in the deflagration index measured by different researchers for the same methane/air or hydrogen/air mixture. In this study, outwardly propagating spherical flames in a closed vessel are simulated by considering detailed chemistry as well as temperature-dependent thermal and transport properties. From simulation, the maximum pressure rise rate and deflagration index of methane, hydrogen and their mixtures are obtained. The influence of equivalence ratio, initial temperature and initial pressure on the maximum pressure rise rate and deflagration index is examined. It is found that the deflagration index has not been accurately measured in previous experiments, and that experiments conducted in cylindrical vessels have under-predicted greatly the deflagration index. For hydrogen/methane mixtures with hydrogen blending level above 70%, the deflagration index is observed to increase exponentially with hydrogen blending level. Moreover, the deflagration index is found to be greatly affected by initial pressure; while the initial temperature has little influence on deflagration index. Finally, based on theoretical analysis we propose a correlation to calculate the maximum pressure rise rate and deflagration index of methane at a broad range of initial pressure. The performance of this correlation is examined and it is demonstrated to provide accurate prediction.

Study on the critical parameters of spherical detonation direct initiation in hydrogen/oxygen mixtures

Critical parameters of detonation direct initiation are important to the utilization of detonation and the safety of industrial process. The model of detonation direct initiation was established, as shown in the figure in abstract and a criterion for spherical detonation direct initiation was put forward based on ZND theory of detonation wave structure and theory of strong point blast. The critical radius of detonation kernel and the critical energy of spherical detonation direct initiation can be calculated by using the basic properties of gaseous mixture. The critical radius of detonation kernel and the critical energy of spherical detonation direct initiation in hydrogen/oxygen mixtures were studied. The influences of equivalence ratio and initial pressure on the critical parameters of spherical detonation direct initiation were investigated. The calculated critical energy of spherical detonation direct initiation in hydrogen/oxygen mixtures was compared with the experiment result and reasonable agreement was obtained.

ANALYTICAL AND EXPERIMENTAL STUDIES ON A 50 kWth DOWNDRAFT GASIFIER WITH BIOMASS BLENDS AVAILABLE IN THE HILLY REGIONS OF SOUTH INDIA

Biomass Gasification has emerged as the most promising technology for the decentralized heat and power applications. The prediction of the performance of biomass blends in gasifiers is an important area of study for the implementation of this technology in various applications, relevant to remote villages. This paper presents the theoretical and experimental studies conducted on a 50 kWth downdraft biomass gasifier with various combinations of the biomass materials such as wood, coconut shell, rubber seed kernel and coir pith, which are abundantly available in the villages of South India. Two zone kinetic equilibrium model is used for the theoretical simulation. The influence of equivalence ratio and composition of feedstock blends on the quality of producer gas and the conversion efficiency of gasifier were studied, and reported. The experimental and theoretical studies show that the effective utilization of biomass materials as blends can meet the rural energy demand.

Pembakaran Premixed Minyak Nabati pada Bunsen Burner Type Silinder

In the premixed combustion wave propagation combustion occurs is called the flame front. Premixed flame will propagate at the speed of moving towards the reactants unique. If the speed of the reactants is equal to the speed of propagation of fire, the fire (reaction zone) will be stationary. It is necessary to follow up on the influence of equivalence ratio (φ) varied with laminar flame speed (SL) in the premixed combustion of vegetable oil (virgin coconut oil, jatropha and cotton seeds). Research using experimental (true experimental research), which is put through direct observation by the equivalence ratio (φ), 1.5, 1.6, 1.7 and 1.8 m / l, to determine the causal relationship. Then the results showed a pattern of fire Bunsen burner pure coconut oil with equivalence ratio (φ), namely: 2.00, 1.87, 1.78, and 1.66, jatropha oil with equivalence ratio (φ) are: 1.73, 1.62, 1:52, and 1:44 and seed oil kapok with equivalence ratio (φ) are: 1.76, 1.65, 1:55, and 1:46, the richer the air the flame pattern that looks smaller and smaller until the blow off. This happens because the richer the air causes the fuel has an air excess so that the fuel (fuel) burning diffusion semakain reduced and cause combustion close to the surface of the tip of the nozzle Bunsen burner to high flame formed shorter until there blow off or extinguished.

Rubber Seed Kernel as a Substitute for Wood in a Biomass Gasifier – An Experimental Study

The prediction of the performance of different biomass energy sources in gasifiers is an important area of study for the implementation of this technology in various applications, relevant to remote villages. This paper presents the experimental studies conducted on a 50 kW imbert downdraft gasifier with wood and rubber seed kernel which are available abundantly in villages close to hilly regions of South India. The influence of equivalence ratio on the species concentration, gas production rate, HHV of producer gas and gasifier conversion efficiency are discussed. The experimental study shows that the rubber seed kernel can be effectively used as feedstock in biomass gasifiers to meet the decentralized heat and power applications of rural villages.