End Gas Research Articles

G-11 定容燃焼容器によるノック発生過程の予混合火炎およびエンドガスの挙動に対する火炎温度の影響の考察

G-11 定容燃焼容器によるノック発生過程の予混合火炎およびエンドガスの挙動に対する火炎温度の影響の考察

TECHNICAL, TECHNOLOGICAL AND INVESTMENT BENEFITS OF COKE GAS COOLING USING SPIRAL FINAL GAS COOLER

The article describes technical and technological advantages of the cooling of coke oven gas using spiral heat exchangers and gas coolers. Based on the analysis of a number of relative and absolute indicators the eff ectiveness of using spiral end gas refrigerators was assessed on the example of «NEXSON GROUP» equipment. The aim was to prove the technical and economic advantages of the cooling of coke oven gas cycle closing using spiral fi nal gas coolers. Achieving this goal is possible with the next sequential addressing number of tasks: to present the procedure of exercising the technological scheme of cooling of coke oven gascycle closing using spiral gas cooler; to compare the main circuit of cooling of coke oven gas cycle closing based on the most representative assessment of performance; and to assess the eff ectiveness of investments aimed at closing of cycle with the cooling of coke oven gas using spiral gas cooler. The article discusses and describes the basic elements of the author’s theory of benefi ts of using the spiral end of the gas cooler for cooling of coke oven gas, supplemented with illustrative material and calculations, providing relevant argumentation base. The authors have made general conclusion about the technical and technological benefi ts and economic feasibility of using the spiral gas coolers for coke production in the case of implementation of such a scheme by the closing cycle of new construction and through rehabilitation of existing facilities. Statements and conclusions of the work can be applied by management of metallurgical holdings for the purpose of theoretical foundation of corporate development programs, as well as regional government to identify ways to increase environmental security in the region and enhance its attractiveness.

Trace detection of research department explosive (RDX) using electrochemical gas sensor

Scientific interest in the detection of the high-explosive research department explosive (RDX) continues to escalate from a national security perspective. In this article, selective and sensitive detection of trace RDX is demonstrated. The screening system is based on a concentrator front end and electrochemical potentiometric gas sensor as the backend. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of RDX (down to 20ng). The sensitivity was found to depend on the flow rate. The sensitivity was found to increase with increasing flow rate. A 42% increase in sensitivity was observed with a flow rate of 500ml/min. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.

Two-Stage Turbocharging for the Downsizing of SI V-Engines

One of the most critical challenges for the specific power increase of turbocharged SI engines is the low end torque, limited by two aspects. First, the big size of the compressor necessary to deliver the maximum airflow does not allow high boost pressures at low speed, due to the surge line proximity. Second, the flame front velocity may become slower than the end gas auto-ignition rate, thus increasing the risk of knocking.This study is based on a current SI GDI V8 turbocharged engine, modeled by means of CFD tools, both 1d and 3d. The goal of the activity is to lower by 20% the displacement, without reducing brake torque, all over the engine speed range.It was decided to adopt a smaller bore, keeping stroke constant. Obviously, the combustion chamber, the valves and the intake-exhaust ports have been re-designed, as well as the whole intake and exhaust system. Instead of the two turbochargers, one for each bank of cylinders, a triple-turbocharger layout has been considered.The development of the engine has been carried out by means of 1D engine cycle simulations, using predictive knock models, calibrated with the support of both experiments and CFD-3d simulations. A few operating conditions for the final configuration have been also analyzed by means of a 3-d CFD tool.The paper presents the results of this activity, and describes in details the guidelines followed for the development of the engine.

A Numerical Investigation on the Potentials of Water Injection to Increase Knock Resistance and Reduce Fuel Consumption in Highly Downsized GDI Engines

3D CFD analyses are used to analyse the effects of port-injection of water in a high performance turbocharged GDI engine. Particularly, water injection is adopted to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock resistance. A full-load / maximum power engine operation of a currently made turbocharged GDI engine is investigated comparing the actual adopted fuel-only rich mixture to stoichiometric-to-lean mixtures, for which water is added in the intake port under constant charge cooling in the combustion chamber. In order to find the optimum fuel/water balance, preliminary analyses are carried out using a chemical reactor to evaluate the effects of charge dilution and mixture modification on both autoignition delays and laminar flame speeds. Thanks to the lower chemical reactivity of the diluted end gases, the water-injected engine allows the spark advance (SA) to be increased; as a consequence, engine power target is met, or even crossed, with a simultaneous relevant reduction of fuel consumption.

Prediction of the knocking combustion and NOx formation for fuel gases with different methane numbers

The knocking combustion and the nitric oxide emissions are important boundary conditions with respect to a further efficiency increase in large gas engines. It was, therefore, the aim of the presented work to model the self-ignition of the end gas and the nitric oxide formation for different burn gas mixtures using detailed reaction kinetics. The investigations were based on a one-dimensional gas exchange model with an adapted, predictive combustion model. An empirical model of the cyclic variations was implemented. In contrast to previous approaches, particularly the fast burning cycles were analysed in order to predict the knocking combustion. All models were validated with measurements from a one-cylinder research engine. The comparison with test bench results showed that a good correlation with the measurements could be achieved for the engine performance, the combustion as well as for the nitric oxide formation and the knock tendency. The numerical models will further be used to optimize the combustion process.

Effects of thermodynamic conditions on the end gas combustion mode associated with engine knock

Super-knock is the main obstacle to improve power density and engine efficiency of modern gasoline engines. To understand the mechanism of super-knock, this study presents an investigation on the end gas combustion process of stoichiometric isooctane/oxygen/nitrogen mixture using a rapid compression machine (RCM), under the thermodynamic conditions close to those of production engines. The combustion process was captured by simultaneous high speed direct photography and pressure acquisition in the RCM. Three end gas combustion modes: no-auto-ignition, sequential auto-ignition, and detonation under different initial conditions were identified and characterized. The super-knock in engine was confirmed to be the result of detonation by comparing the pressure oscillation, thermodynamic state, and pressure rise relative to isochoric combustion with those of detonation observed in the RCM. The experimental results also indicate that the possibility of detonation occurrence increases with increasing initial pressure under the same compression ratio. However, comparing to the pressure, temperature has less effect on detonation formation. It was found that the end gas combustion mode is closely related to the mixture energy density. Generally, as the mixture energy density increases, the end gas combustion mode gradually transits from no-auto-ignition to sequential auto-ignition, and then to detonation. The first auto-ignition spots commonly appear in the mixture near the cylinder wall. The detonation was initiated by near-wall auto-ignition.

Continuous process of biogas purification and co-production of nano calcium carbonate in multistage membrane reactors

CO2 capture is one of the key technologies in biogas production. Using lime slurry to purify biogas and co-production of nano calcium carbonate is an economical approach. In this work, multistage cross flow membrane reactors with continuous process were designed. Factors that influence CO2 absorption efficiency such as Ca(OH)2 slurry concentration, flow rate, additives, gas flow rate, membrane length and the connecting pipe length were studied to select the proper parameters. Results show that high slurry flow rate, low gas flow rate, long membrane and connecting pipe and the dosage of additives may enhance CO2 absorption, while Ca(OH)2 concentration has little impact on it. The hydrophobicity modification on the ceramic membrane using a silane coupling agent was also carried out. The change from hydrophilicity to hydrophobicity gave the reactor a higher mass transfer efficiency. Using the parameters carefully chosen based on the work above, the two-stage membrane reactors assembled successfully purified the gas (with end gas CO2 content lower than 3%) and produced nano calcium carbonate with 72.8nm average particle size. Extension of the experiment showed that this apparatus could run smoothly for at least 5h. This work may provide a new method in biogas purification and nano calcium carbonate synthesis.

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensor

In this paper, selective and sensitive detection of trace amounts of 2, 4, 6-trinitrotoluene is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (down to 250 ng). The sensitivity was found to depend on the flow rate and sensor orientation. The sensitivity was found to increase with increasing flow rate. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.

601 Observation of Premixed Flame and End Gas on Occurrence of Knock in a Constant Volume Vessel

601 Observation of Premixed Flame and End Gas on Occurrence of Knock in a Constant Volume Vessel

High image quality type-II superlattice detector for 3.3 μm detection of volatile organic compounds

Recent improvements in material quality, structure design and processing have made type-II superlattice a competing high end detector technology. This has also made it an attractive material of choice to meet the industrial need of high end gas detection, as for example detection of methane and other volatile organic compounds (VOC). A heterojunction structure with a cut off at 5μm but intended for detection of VOC at 3.3μm will be presented. The detector format is 320×256 pixels with 30μm pitch using the ISC9705 read out circuit. The detector operability is 99.8% and NETD 12 mK (7ms integration time, object temperature 30°C and F#2.6, no cold filter used). The uniformity is at least on par with QWIP detectors. Anti-reflective coating is used and the substrate is fully removed. High quality imaging at operating temperature 110K will be presented.

A numerical study on pressure wave-induced end gas auto-ignition near top dead center of a downsized spark ignition engine

Auto-ignition of end gas is known as a main cause of knock in SI engine. In order to study the characters of auto-ignition induced by pressure wave, different levels of hot zones characterized by temperature gradients are created in end gas, which are then ignited by incident pressure wave developed from main flame. Evolutions of pressure and temperature in end gas are monitored to investigate pressure incidence and end gas auto-ignition. Computational Fluid Dynamics (CFD) calculations are carried out in a simplified two-dimensional symmetrical computational domain. Turbulence is modeled by renormalization-group (RNG) k–ε model and the turbulence-chemistry interaction is modeled using Eddy Dissipation Concept (EDC) with a detailed chemical kinetic mechanism for hydrogen oxidation. Ignition delay sensitivity analysis is also employed to investigate chemical kinetics during the incidence of pressure wave. The results show that the incidence of pressure wave has significantly different effects on auto-ignition characteristics, thus resulting in different ignition delays, pressure oscillations and enhancements of reflected pressure wave.

The potential of catalysed exhaust gas recirculation to improve high-load operation in spark ignition engines

Within the literature, there are a number of studies investigating the benefits of exhaust gas recirculation, and as a result it has become established as a promising technology for combustion control to allow engine downsizing technology to be advanced. Aside from the dilution effect of exhaust gas recirculation, some of the components, such as NO, CO, and hydrocarbons, can have significant chemical effects. The literature shows that the component within exhaust gas recirculation which has the largest chemical effect on combustion is NO, which can promote or inhibit the onset of autoignition causing reactions within the end gas at high load. The reduction in NOx gases in catalysed exhaust gas recirculation can increase the knock limit at high load, with some authors reporting up to a 5∘ crank angle improvement in combustion phasing. There is conflicting evidence on whether this translates to an improvement in fuel consumption, with one study finding a decrease of up to 2% comparing to another finding an increase of 1.5%-3.5%. Crude calculations on the emissions of a 2.0-L direct injection spark ignition engine operating at high load show that in an extreme case the reduction in the calorific value of the inlet charge due to catalysis of the recirculated gases can be up to 4.5%. Despite the potential benefits, the literature on catalysed exhaust gas recirculation is fairly limited and the evidence seems so far inconclusive as to whether this technology may have the potential to further enhance the benefits of exhaust gas recirculation. This article uses current literature to ascertain the potential benefits of catalysed exhaust gas recirculation, compare to pre-catalyst exhaust gas recirculation, and investigates its individual components in more detail to explain how chemical interactions can either promote or inhibit ignition depending on their concentration and temperature.

Frequency domain analysis of knock images

High speed imaging-based knock analysis has mainly focused on time domain information, e.g. the spark triggered flame speed, the time when end gas auto-ignition occurs and the end gas flame speed after auto-ignition. This study presents a frequency domain analysis on the knock images recorded using a high speed camera with direct photography in a rapid compression machine (RCM). To clearly visualize the pressure wave oscillation in the combustion chamber, the images were high-pass-filtered to extract the luminosity oscillation. The luminosity spectrum was then obtained by applying fast Fourier transform (FFT) to three basic colour components (red, green and blue) of the high-pass-filtered images. Compared to the pressure spectrum, the luminosity spectra better identify the resonant modes of pressure wave oscillation. More importantly, the resonant mode shapes can be clearly visualized by reconstructing the images based on the amplitudes of luminosity spectra at the corresponding resonant frequencies, which agree well with the analytical solutions for mode shapes of gas vibration in a cylindrical cavity.

A predictive model for knock onset in spark-ignition engines with cooled EGR

A predictive knock model is crucial for one dimensional (1-D) engine cycle simulation that has been proven to be a powerful tool in both optimization of the conceptual design and reduction of calibration efforts in development of spark-ignition (SI) engines. With application of advanced technologies such as exhaust gas recirculation (EGR) in modern SI engines, update of knock model is needed to give an acceptable prediction of knock onset. In this study, bench tests of a turbocharged gasoline SI engine with cooled EGR system operated under knocking conditions were conducted, the cylinder pressure traces were analyzed by the band-pass filtering technique, and the crank angle of knock onset was determined by the signal energy ratio (SER) and image processing method. A knock model considering multi-variable effects including pressure, temperature, EGR ratio and excess air ratio (λ) is formulated and calibrated with the experimental data using the multi-island genetic algorithm (GA). The calculation method of the end gas temperature, the impacts of the ratio of specific heats as well as the temperature at the intake valve closure on the end gas temperature are discussed. The performance of the new model is compared with the widely-used phenomenological knock models such as Douaud–Eyzat model and Hoepke model. While the widely-used knock models fail to give acceptable predictions when increasing EGR with fuel enrichment operations, the new model predicts the knock onset with high accuracy under the fuel enrichment conditions both with and without EGR. Performance of the newly developed model is also examined in a different engine and a higher predictive accuracy of the new model than other models is obtained.

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensors

In this article, selective and sensitive detection of trace amounts of 2, 4, 6-trinitrotoluene (TNT) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (down to 250 ng). The sensitivity was found to increase with increasing flow rate.

Trace Detection of 2, 4, 6-Trinitrotoluene Using Electrochemical Gas Sensors

In this article, selective and sensitive detection of trace amounts of 2, 4, 6-trinitrotoluene (TNT) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors with integrated heaters were used to capture the signature of the explosive. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (down to 250 ng). The sensitivity was found to depend on the flow rate and sensor orientation. The sensitivity was found to increase with increasing flow rate. This detection technique has the potential to become an orthogonal technique to the existing explosive screening technologies for reducing the number of false positives/false negatives in a cost-effective manner.

Veillonella seminalis sp. nov., a novel anaerobic Gram-stain-negative coccus from human clinical samples, and emended description of the genus Veillonella.

Ten isolates of unknown, Gram-stain-negative, anaerobic cocci were recovered from human clinical samples, mainly from semen. On the basis of their phenotypic features, including morphology, main metabolic end products, gas production, nitrate reduction and decarboxylation of succinate, the strains were identified as members of the genus Veillonella. Multi-locus sequence analysis and corresponding phylogenies were based on 16S rRNA, dnaK and rpoB genes, and on the newly proposed gltA gene. The strains shared high levels of genetic sequence similarity and were related most closely to Veillonella ratti. The strains could not be differentiated from V. ratti on the basis of 16S rRNA gene sequence analysis while gltA, rpoB and dnaK gene sequences showed 85.1, 93.5 and 90.2% similarity with those of the type strain of V. ratti, respectively. Phylogenetic analyses revealed that the isolates formed a robust clade in the V. ratti-Veillonella criceti-Veillonella magna subgroup of the genus Veillonella. As observed for V. criceti, the isolates were able to ferment fructose. In contrast to other members of the genus Veillonella, the 10 strains were not able to metabolize lactate. Cellular fatty acid composition was consistent with that of other species of the genus Veillonella. From these data, the 10 isolates are considered to belong to a novel species in the genus Veillonella, for which the name Veillonella seminalis sp. nov. is proposed. The type strain is ADV 4313.2(T) ( = CIP 107810(T) = LMG 28162(T)). Veillonella strain ACS-216-V-Col6b subjected to whole genome sequencing as part as the Human Microbiome Project is another representative of V. seminalis sp. nov. An emended description of the genus Veillonella is also proposed.

Physicochemical effects of varying fuel composition on knock characteristics of natural gas mixtures

The physicochemical origins of how changes in fuel composition affect autoignition of the end gas, leading to engine knock, are analyzed for a natural gas engine. Experiments in a lean-burn, high-speed medium-BMEP gas engine are performed using a reference natural gas with systematically varied fractions of admixed ethane, propane and hydrogen. Thermodynamic analysis of the measured non-knocking pressure histories shows that, in addition to the expected changes arising from changes in the heat capacity of the mixture, changes in the combustion duration relative to the compression cycle (the combustion “phasing”) caused by variations in burning velocity dominate the effects of fuel composition on the temperature (and pressure) of the end gas. Thus, despite the increase in the heat capacity of the fuel–air mixture with addition of ethane and propane, the change in combustion phasing is actually seen to increase the maximum end-gas temperature slightly for these fuel components. By the same token, the substantial change in combustion duration upon hydrogen addition strongly increases the end-gas temperature, beyond that caused by the decrease in mixture heat capacity. The impact of these variations in in-cylinder conditions on the knock tendency of the fuel have been assessed using autoignition delay times computed using SENKIN and a detailed chemical mechanism for the end gas under the conditions extant in the engine. The results show that the ignition-promoting effect of hydrogen is mainly the result of the increase in end-gas temperature and pressure, while addition of ethane and propane promotes ignition primarily by changing the chemical autoignition behavior of the fuel itself. Comparison of the computed end-gas autoignition delay time, based on the complete measured pressure history of each gas, with the measured Knock-Limited Spark Timing shows that the computed delay time accurately reflects the measured knock tendency of the fuels.

Ending Natural Gas Flaring in Nigeria’s Oil Fields

Nigeria has one of the largest ten natural gas reserves in the world and roughly 50% of the deposits are discovered in association with oil. Over the years most of the associated gas is flared, with the attendant damage to the environment and a huge economic loss. Several efforts have recently been made to curtail gas flaring, including the establishment of a liquefied natural gas plant, a pipeline to transport gas to some neighbouring countries, and legislative measures to regulate the oil and gas industry. Additional projects are being planned and some of these are at various stages of completion. This work presents a three-scenario analysis of current and planned projects aimed at ending gas flaring activities over a study period 30 years (2010 - 2040). The first scenario is a business-as-usual case based on existing infrastructures. The second scenario assumes all firm projects are implemented as planned, while the third scenario assumes that, in addition to the firm projects, further projects are implemented. Results of the analysis indicate that existing infrastructure will not be sufficient to end gas flaring in the country. The implementation of firm planned projects in the second scenario will only reduce gas flaring to about 10% in 2040. The third scenario of additional projects ensures total elimination of gas flaring. The last two scenarios indicate that 2018 is the year when significant reduction in gas flaring can be achieved in Nigeria. Results also indicate that beyond the firm planned projects in the second scenario, proper timing and sizing of additional projects will be very critical in order to minimise stress on non-associated gas reserves.