Emission Characteristics Of CO Research Articles

H-atom abstraction reactions of C1-C4 alkanes by ketenyl radical: Kinetic investigation and analysis

The kinetics of 16 H-atom abstraction reactions of C1-C4 alkanes by ketenyl radical (HCCO) are studied to enhance the existing combustion mechanisms. Firstly, the obtain the lowest-energy conformer, vibration frequencies and single point energies for the reactants, prepolymers, transition states, and products are determined using the CCSD(T)/cc-pVQZ//B3LYP/6-311G+(d,p) theory level. Subsequently, temperature-dependent reaction rate constants for the major channels are predicted by the TST method. Finally, the H-atom abstraction reactions are validated under multiple temperature conditions, and the effects of the reactions on auto-ignition process and CO emission characteristics of n-heptane/NG mixture are researched. The results indicate that the H-atom abstraction reactions by Cα-atom play a significant role for the diesel/NG combustion. To combine the reaction pathways and rate constants into the existing kinetic mechanisms resulted in more accurate predictions of the ignition delay time. Furthermore, these kinetics data are valuable for revealing the CO emissions of the dual-fuel engines.

NO and CO Emission Characteristics of Laminar and Turbulent Counterflow Premixed Hydrogen-Rich Syngas/Air Flames

Burning hydrogen-rich syngas fuels derived from various sources in combustion equipment is an effective pathway to enhance energy security and of significant practical implications. Emissions from the combustion of hydrogen-rich fuels have been a main concern in both academia and industry. In this study, the NO and CO emission characteristics of both laminar and turbulent counterflow premixed hydrogen-rich syngas/air flames were experimentally and numerically studied. The results showed that for both laminar and turbulent counterflow premixed flames, the peak NO mole fraction increased as the equivalence ratio increased from 0.6 to 1.0 and decreased as the strain rate increased. Compared with the laminar flames at the same bulk flow velocity, turbulent flames demonstrated a lower peak NO mole fraction but broader NO formation region. Using the analogy theorem, a one-dimensional turbulent counterflow flame model was established, and the numerical results indicated that the small-scale turbulence-induced heat and mass transport enhancements significantly affected NO emission. Considering NO formation at the same level of fuel consumption, the NO formation of the turbulent flame was significantly lower than that of the laminar flame at the same level of fuel consumption, implying that the turbulence-induced heat and mass transfer enhancement favored NOx suppression.

Experimental investigations on emission characteristics of heavy-duty hybrid electric vehicles

The emission characteristics under different operating modes (engine mode and hybrid mode) and different test cycles (C-WTVC and CHTC) of a heavy-duty hybrid electric dump truck was investigated on the chassis dynamometer. The emission performance was recorded using Portable Emissions Measurement System (PEMS) and analyzed combined with the characteristic parameters of the test conditions. It is found that the NOx emission under hybrid mode is higher than that under engine mode, while the CO emission under hybrid mode is lower than engine mode. Under engine mode, the NOx emission of CHTC is higher than that of C-WTVC. However, under hybrid mode, the NOx emission of CHTC is lower than C-WTVC. Analysis of CO emission characteristics shows that under engine mode, CO emission is concentrated at low speed and small load condition, while under hybrid mode, CO emission is concentrated at high speed and large load condition.

Effect of acoustic excitation on the combustion and emission characteristics of methane-ammonia-air swirling flame

The blending characteristics of ammonia with conventional fuels have recently received much attention from researchers. This paper investigated the effect of acoustic excitation on the combustion and emission characteristics of methane-ammonia-air swirling flame on a laboratory-scale swirl burner. The high-speed schlieren imaging system was used to visualize the flame flow under acoustic excitation. The emission characteristics of CO and NOx at different excitation frequencies (70–270 Hz) and sound pressure levels (SPL, 117–128 dB) were determined. Results show that adding ammonia causes a significant increase in NOx emission and an increase in CO emission under fuel-rich conditions. The flame shows a layered V-shape with periodic development under weak low-frequency (70 Hz) acoustic excitation and an inverted cone with step distribution under high-frequency (270 Hz) acoustic excitation. Low-frequency acoustic excitation can reduce CO and NOx emissions under fuel-lean conditions. Especially for the excitation condition of 120 Hz (Prel = 0.3), NOx and CO emissions are reduced by 203 ppmvd and 170 ppmvd, respectively. However, when the excitation is stronger, the CO emission will rise sharply due to the destruction of the flame structure. Besides, the more intense acoustic excitation will cause a decrease in CO emission and an increase in NOx emission under fuel-rich conditions.

Reconfirmation of the symbiosis on carbon emissions and air pollution: A spatial spillover perspective

Many studies have confirmed the co-emission characteristics of air pollution and carbon emissions. However, studies on the evolution and synergistic factors of the symbiosis of air pollution and carbon emissions over long time scales from a spatial spillover perspective are rare. Here, we identify the spatial evolution and agglomeration characteristics of carbon emissions and air pollution symbiosis by applying local autocorrelation analysis and geographical concentration and by using the dynamic spatial autoregressive model for multiple synergistic factors at city levels during 2006–2019 in China. The results are: (1) The spatial agglomeration and symbiosis of carbon emission and air pollution are similar and show strong spatial locking, as well as path-dependent properties. (2) The spatial imbalance of carbon emission agglomeration and pollution agglomeration gradually improved over time; the concentration centers are all located in Henan province, shifting northward. (3) The symbiosis between both carbon emission agglomeration and pollution agglomeration has significant “spatial and temporal scale effects”, and the economic growth is nonlinear. Additionally, innovation vitality has a negative synergistic driving effect on this relationship. In addition to the results above, rapid industrialization and urbanization are taking place in China. Hence, serious actions against greenhouse gases and air pollutants are imminently needed.

Effects of Thermal Thickness and Charring Properties of Solid Combustibles on Heat Release and CO Emission Characteristics

In this study, a series of ISO 5660-1 cone calorimetry experiments were performed to understand how the heat release rate (HRR) and CO emission are affected by the thermal thickness and charring properties of solid combustibles. To this end, HRRs and CO emissions measured from burning Douglas-fir wood (which produces a charring layer during combustion) and poly methyl methacrylate (PMMA) (which does not produce a charring layer) in the ISO 5660-1 cone calorimetry experiments were compared. Relative to PMMA, Douglas-fir wood produced a lower rate of heat release and CO emission, helping lessen human damage in fires. Results obtained from the ISO 5660-1 cone calorimetry experiments clearly demonstrate that the heat release rate varies depending on the thermal thickness and the presence of charring layer within solid combustibles. Unlike PMMA, the charring layer developed for Douglas-fir wood during combustion further increases the thermal thickness, reducing the amount of thermal decomposition and the heat released from fire. The cone calorimetry experiment results also indicate that increases in charring properties of solid combustibles were directly correlated with reductions in the HRR and increases in the CO emission.

Experimental investigation on influence of metal based additives on performance, combustion and emission parameters of diesel engine

A biodiesel substitute for regular diesel is widely seen as having greater social advantages, such as decreasing greenhouse gas emissions and sustaining rural agriculture economies, than conventional diesel fuel. As a natural fuel, biodiesel has a variety of feedstocks such as vegetable oils and animal fats. A biodegradable material made from fatty acid esters such as methyl and ethyl. Oils such as palm oil, soya bean oil, sunflower oil, etc., produce the majority of today's biodiesel fuels due to their eco-friendliness and sustainability.. Transesterification of waste chicken fat oil to produce biodiesel in a 1:1 ratio, followed by testing the performance and emission characteristics of a C.I engine running on the biodiesel. There will be three distinct proportions of B10, B20, and B30 blends of biodiesel with diesel and 100 ppm of metal oxide (sio and nio) additive in order to improve fuel ignition and cold starting. When using Conventional Diesel at 180 bar, performance measures such as Brake Power (BP), Brake Specific Fuel Consumption (BSFC), and NOx, HC, and CO emission characteristics of the stated engine at 1500 rpm are analysed. The B20 Biofuel sample was shown to be the most efficient and economical compared to the other two samples, B10 and B30. Nickle oxide and silicon oxide nanoparticles in the B20 blend are particularly interesting due to their features such as improved heat transfer rate.

CO emission regularity and its influencing factors in a fully mechanized caving face

To explore the problem of CO concentration overrun in fully mechanized caving faces, a multiphysical field coupling model of CO emission regularity was established in this study based on the gas flow theory, gas concentration field theory, and heat transfer theory. Taking the 014N1−1 working face of the No. 1 coal seam in Ruian coal mine as the research object, the model was applied to simulate the CO concentration in the fully mechanized caving face. The simulation results were found to be consistent with the field detection results. Based on the simulation results, the effects of advancing speed and wind velocity on the CO emissions in the gob and the CO concentration distribution in the working face were analyzed. The results showed that, the lower the wind velocity, the greater the CO emissions. With increasing advancing speed, the CO emissions in the gob first increased, reached maximum, and then decreased. The production conditions were found to be most suitable when the advancing speed and wind velocity were 2 and 1.8 m/s, respectively. Moreover, the CO emission characteristics of the fully mechanized caving face under the conditions of periodic roof weighting, production process, and atmospheric pressure change were monitored and analyzed. We verified the presence of CO in the coal seam and its emission with the progress of coal seam mining. Our results will be useful in the research and analysis of CO emission source, emission regularity, and overrun warning in fully mechanized working faces.

Analysis of ship emission characteristics under real-world conditions in China

The actual emission characteristics of CO, THC, NOx, and PM from 50 ships were tested by a portable emission measurement system. Statistical analysis of emission data was carried out based on model years and engine types. The results show that with the increase of the model year, the specific emissions of pollutants increase gradually, that is, the stage I ships (before 2000 years) emit more pollutants. For CO, the specific emissions for stage Ⅱ ships (between 2001 and 2010 years) increase by 3.99%–26.39% compared with those for stage Ⅲ ships (between 2011 and 2016 years), and for stage I and Ⅱ ships, the maximum specific emissions increase by 25.34%–36.95 under the same operating modes; The specific emissions of THC are similar to those of CO. The specific emissions of THC increase by 45.84%–52.97% for stage I and Ⅱ ships and the weighted emissions of stage Ⅱ ships are 9.37% higher than that of stage Ⅲ. For NOx, the specific emissions of stage I, Ⅱ and Ⅲ ships are gradually reduced by 1.64%–13.44% and 6.83%–23.19% respectively, and the specific emissions under cruise condition are increased by 16.15%–36.47% compared with maneuvering condition. Due to the limitation of fuel products and test methods, PM emission characteristics are slightly different from other pollutants for different stage ships, but weighted emissions considering errors are reduced by 22.49%–25.59%. For different engine types, the specific emissions of high speed engines are higher than those of medium speed engines, especially for CO and THC pollutants, which are 16.05%–36.61% and 6.52%–73.31% higher respectively; On the contrary, for NOx, the emissions for each stage ships are reduced by 8.21%–8.82% compared with those for other stages, and PM has no consistent trend. At the same time, compared with foreign experimental data (European, USA, Sweden, et al.), the emissions of domestic ships, traveling on major routes (Yangtze river basin and Shandong coastal area and so on) in China, are about 1.1–5.11 times than that of other countries.

CO emission of domestic gas cooker on Dutton diagram

The gas distribution system tends to be connected with multiple gas sources to meet the increasing demand for natural gas. However, different sources may cause a fluctuation of the constituents and lead to an increase of CO emission on domestic gas cookers. The purpose of this paper is to study CO emission characteristics of domestic gas cookers under variable three-component mixtures based on Dutton approach. In this paper, two typical gas cookers with round-port burner and strip-port burner were tested under different three-component mixtures. With reference to Dutton’s approach, CO emissions for three-component mixtures were experimentally measured. A universal formula is derived from fitting the experiment data to predict the CO emission of the cooker. The influence of initial primary air coefficient to this formula is discussed. A series of CO iso-lines are revealed on the Dutton diagram. A method to determine the limit gas was discussed based on CO iso-lines on the Dutton diagram.

Performance, combustion and emission characteristics of juliflora biodiesel fuelled DI diesel engine

The focus of this investigation is on biodiesel produced from juliflora seeds using the 2-stage acid transesterification process followed by alkali transesterification process producing 80% yield of Juliflra Oil Methyl Ester. Experiments were conducted on single cylinder diesel engine using juliflora biodiesel and its diesel blends. The experimental results of fuel blends (B20, B30, B40, and B100) were compared with those from diesel (D100). The results indicated the performance and combustion characteristics of B20 as almost in line with those of diesel fuel trend. Brake Specific Fuel Consumption (BSFC) for blends B20 and B30 (0.27kg/KWh) at full load was closer to diesel (0.26 kg/KWh). The BTE for Juliflora Biodiesel B100 is 31.11% and it was closer to diesel (32.05%) at full load. However the emission characteristics of CO, HC and smoke for biodiesel and its blends were smaller or equal compared to diesel throughout the experiment. At full load, the NOx for biodiesel B100 was 1832 ppm which was a little higher than diesel fuel (1821 ppm). This led to the conclusion of B20 being most suitable blend of other blends and it is substitute of diesel which will reduce diesel consumption by 20%.

An Experimental Investigation on the NO and CO Emission Characteristics of a Swirl Convergent-Divergent Nozzle at Elevated Pressure

The behavior of the pollutants NO and CO at elevated combustor pressure are of special importance due to the continuing trend toward developing engines operating at higher pressure ratios to yield higher thermal efficiency. An experiment was performed to examine the NO and CO emissions for a swirl convergent-divergent nozzle at elevated pressure. The NO and CO correlations were obtained. Meanwhile, the flame length, exhaust gas oxygen concentration, exit temperature and global flame residence time were also determined to analyze the NO and CO emission characteristics. The results showed that, with the increase in combustor pressure P, flame length decreased proportionally to P−0.49; exit O2 volume fraction increased and exit temperature was reduced. The global flame residence time decreased proportionally to P−0.43. As pressure increased, The NO and Emission Index of NO (EINO) levels decreased proportionally to P−0.53 and P−0.6 respectively, which is mainly attributed to the influence of global flame residence time; the NO and EINO increased almost proportionally with the increase in global flame residence time. The EINO scaling EINO (ρue/d) was proportional to Fr0.42, which indicated that compared with pure fuel, the fuel diluted with primary air can cause a decrease in the exponent of the Fr power function. At higher pressure, the CO and Emission Index of CO (EICO) decreased proportionally to P−0.35 and P−0.4, respectively, due to the increased unburned methane and high pressure which accelerated chemical reaction kinetics to promote the conversion of CO to CO2.

Biodiesel production using waste cooking oil: a waste to energy conversion strategy

In this study, biodiesel was produced using waste cooking oil that was discarded as a waste in the environment. The properties of the feedstock were determined using standard ASTM methods. The transesterification process was implemented to extract the biodiesel, and this process was optimized and standardized by selecting three different parameters: molar ratio (methanol:oil), catalyst concentration (KOH) and reaction temperature. The physicochemical properties of the biodiesel so produced were tested and analyzed using gas chromatography. Biodiesel and diesel were mixed in different volumetric ratios, and the exhaust emission characteristics of the blends were determined by testing the blends on a variable compression ratio engine. The study concluded that waste cooking oil has a great potential for waste to energy process. The highest yield of 93.8% was obtained by optimizing the process. Emission characteristics of CO for B50 blend showed a downward trend while NO x emission was found to be greater for blending ratios above 10%. B10 showed the best results pertaining to lower NO x and CO emissions.

Emissions of NO and CO from counterflow combustion of CH4 under MILD and oxyfuel conditions

This paper reports on the NO and CO emission characteristics of counterflow combustion of methane simulated under MILD or/and oxyfuel conditions. Simulations using CHEMKIN are conducted for various injection conditions of fuel and oxidizer. Note that the terms “oxyfuel”, “MILD-N2” and “MILD-CO2” combustion adopted hereafter represent the conventional oxy-combustion and those MILD combustions diluted by N2 and CO2, respectively. It is observed that the NO emission of MILD-CO2 combustion is ultra-low for all cases of investigation, even when increasing the combustion temperature up to 2000 K or adding more N2 (up to 20%) to either the fuel stream (to simulate nitrogen-containing fuels like biomass) or the oxidizer stream (to simulate the air-ingress). A higher temperature allowed under MILD-CO2 combustion suggests the improvement of energy efficiency for the MILD combustion technology. Moreover, the presence of steam in the oxidant reduces both NO and CO emissions of combustion for all cases.The relative importance analysis reveals that the N2O-intermediate mechanism for producing NO prevails in MILD-CO2 combustion while the prompt and thermal mechanisms predominate MILD-N2 and oxyfuel combustion, respectively. In addition, the sensitivity analysis identifies those main reactions that play important roles for the NO emission under these combustion conditions.

Effects of H2/CO/CH4 syngas composition variation on the NO x and CO emission characteristics in a partially-premixed gas turbine combustor

This paper reports the effects of variations in the fuel composition of H2/CO/CH4 syngas on the characteristics of NO x and CO emissions in a partially-premixed gas turbine combustor. Combustion tests were conducted on a full range of fuel compositions by varying each component gas from 0% to 100% at heat inputs of 40 and 50 kWth. Flame temperature, combustor liner temperature, ignition delay time, and flame structure were investigated computationally and experimentally to judge whether they are significant indicators of NO x and CO formation. The characteristics of and reasons for NO x and CO emissions were investigated by analyzing the emission mechanisms and relationships among fuel property, equivalence ratio, flame temperature, liner temperature, flame shape. The flame structures were investigated using the following flame visualization methods: (1) time-averaged OH* chemiluminescence and its Abel-deconvolution; (2) direct photography; and (3) instantaneous OH-PLIF. The flame structures were greatly changed by the fuel composition and heat input, and they were subjected to key affecting parameters of the temperatures of the flames and the liners. NO x and CO emissions also largely varied according to fuel composition and heat input, showing neither linearly nor exponentially clear proportional trends toward the syngas compositions because of the singular conditions. For example, only the 100% CO flame at low load emitted lots of CO, whereas complete combustion was observed in other cases. However, the qualitative observations showed that the root causes of NO x emission behaviors were flame temperature and flame structure, which were directly related to the residence time in the flame. Various sets of practical test results were obtained, and these results could contribute to the optimal selection of the fuel-feeding condition when fuel is changed from natural gas to syngas in order to minimize NO x and CO emissions with stable combustion.

A comparison of the thermal and emission characteristics of co and counter swirl inverse diffusion flames

In this work the influence of co-swirl and counter-swirl burners on the inverse diffusion flame (IDF) characteristics has been studied using liquefied petroleum gas (LPG). The flame shape of the co and counter IDFs were compared. The momentum exchange between the air and fuel jets for swirled IDF burners effects on the produced flame length and stability. The analysis of the results showed that the co-swirling IDF is shorter and more stable than the counter swirling one. The influence of the air jet Reynolds number (Re) consequently the primary equivalence ratio (Φ) on the flame centerline temperature and exhaust gas emissions were examined. The results showed that for the co swirling IDF the centerline temperature profile is higher than the centerline temperature profile of the counter swirl IDF for all values of Φ used in this study. The CO and NOx emissions comparison were made for the two swirled burners. It was found that Re and swirl directions are two key factors for reducing CO emissions. This study indicates that the CO emission is decreased by using co-swirl IDF.

Effects of air staging on emission characteristics in a conical fluidized-bed combustor firing with sunflower shells

This paper presents experimental results investigated from combustion of sunflower shells in a conical fluidized-bed combustor at feed rate 45 kg/h. Effects of operating parameters, such as excess air (EA) and secondary air to total air ratio (S/T) on combustion performance and emission characteristics of CO, CxHy and NO as well as combustion efficiency (ηc) were studied. Temperature and gas concentrations were measured along the combustor and at the outlet. The secondary air was tangential injected to the combustor at 0.5 m above the fuel feeding system and it was supplied at S/T = 0–0.4 for EA of 20–80%. The high combustion rates were found into two different zones of the combustor; in the bed region with the primary air and in freeboard region which were evidenced by two peaks of CxHy and CO concentrations. According to Thailand emission standard, the optimum operating condition to control CO and NO emissions at the quite high combustion efficiency (∼99%) seems to be EA at 40–60% and S/T = 0.3. Compared with conventional combustion, air staged combustion can reduced the NO emission by 27% when the combustor was operated at EA = 40% and S/T = 0.3. However, CO and CxHy emissions were apparently high.

Experimental and numerical study on NOx and CO emission characteristics of dimethyl ether/air jet diffusion flame

Abstract Dimethyl ether (DME) is one of the most promising alternative fuels emerging in the past few decades. At present, DME is mainly applied to the compression ignition (CI) engines, and numerous studies showed its superior performances in CI engines versus the traditional fuels. More recently, DME was also introduced into the field of industrial boiler to solve the pollution problem raised by coal usage. But the emission behavior of DME in this type of combustion system was not studied as thoroughly. In this paper, experiments and simulations are conducted to study the NOx and CO emission characteristics of the DME/air jet diffusion flame, which may be valuable for design and operation of the DME-fueled industrial boilers. During the measurements, a series of fuel jet velocities (uf) and air co-flow velocities (uco) were designed for the experiments to investigate their effects on NOx and CO emission indices systematically. Additionally, the CFD–CRN method was also employed to analyze NOx formation characteristics in different regions of the flame. The conversion relationship between the nitrogenous species (including NO, NO2, HCN, etc.), NOx formation and consumption pathways, and NOx and CO emission indices of the DME/air jet diffusion flame were analyzed by reaction rate and sensitivity analyses.

Pollutant emission characteristics of rice husk combustion in a vortexing fluidized bed incinerator

Rice husk with high volatile content was burned in a pilot scale vortexing fluidized bed incinerator. The fluidized bed incinerator was constructed of 6 mm stainless steel with 0.45 m in diameter and 5 m in height. The emission characteristics of CO, NO, and SO2 were studied. The effects of operating parameters, such as primary air flow rate, secondary air flow rate, and excess air ratio on the pollutant emissions were also investigated. The results show that a large proportion of combustion occurs at the bed surface and the freeboard zone. The SO2 concentration in the flue gas decreases with increasing excess air ratio, while the NOx concentration shows reverse trend. The flow rate of secondary air has a significant impact on the CO emission. For a fixed primary air flowrate, CO emission decreases with the secondary air flowrate. For a fixed excess air ratio, CO emission decreases with the ratio of secondary to primary air flow. The minimum CO emission of 72 ppm is attained at the operating condition of 40% excess air ratio and 0.6 partition air ratio. The NOx and SO2 concentrations in the flue gas at this condition are 159 and 36 ppm, which conform to the EPA regulation of Taiwan.

An experimental study of heat transfer and pollutant emission characteristics at varying distances between the burner and the heat exchanger in a compact combustion system

The effect of the distance between the burner and the heat exchanger on the heat transfer characteristics and NOx and CO emission characteristics in a compact combustion system was studied. The premixed burner was installed in front of a heat exchanger, and the distance between the burner and the heat exchanger was varied from 30 mm to 50 mm to experimentally investigate the effect of distance for the counter flow and the parallel flow conditions. Distances in the type A, type B and type C heat exchangers were 30 mm, 40 mm and 50 mm, respectively. The results showed that NOx concentration increased at the same equivalence ratio for both flow conditions as the distance between the burner and the heat exchanger increased. On the other hand, CO emission increased for both flow conditions due to the quenching effect as the distance between the burner and the heat exchanger decreased. In the experimental range, the optimal equivalence ratio of heat exchanger type A was 0.75 to minimize pollutant emission. At this condition, the NOx and CO emissions were 32.3 ppm and 85.6 ppm, respectively, and the effectiveness was 0.797.