Gas Combustion Research Articles

CFD modeling of thermal processes in the firebox and heat load distribution on the screen surface firebox

Using ANSYS FLUENT numerical modeling and mathematical modeling, the main characteristics of combustion processes during the combustion of natural gas were determined. In this work, the combustion processes and NOx formation in the firebox were modeled at different loads of the GM- 50-14/250 boiler. The temperature distribution along the height of the firebox and the heat load on the screen panels were determined. The results of calculations by two types of models were compared with each other and with the data of measurements on the operating equipment. The environmental performance of the firebox, namely the formation of NOx at different heat loads, was determined. The maximum boiler capacity at which its operation meets European environmental standards was determined. The deviation of calculations on the formation of NOx in the GM-50-14/250 boiler at 40% of the rated power compared to the results of field tests using ANSYS FLUENT modeling was 8%, and using the mathematical model - 27%. When operating at rated power, the deviations of the results decreased to 2% and 8%, respectively. The deviation of the results of thermal calculations of the combustion in the firebox by different types of modeling in the active combustion zone and at the outlet of the firebox is up to 3% at different loads.

Numerical investigation on the exhaust gas combustion of an SOFC in a catalytic multichannel burner

The utilization of the exhaust gas of a solid oxide fuel cell is important to improve the energy efficiency and control pollutant emission. In this work, the combustion of solid oxide fuel cell exhaust gas (H2/CO) in a honeycomb ceramic catalytic burner is investigated numerically. A 2D numerical combustion model with 17 channels is built to analyze the influence of channel position on thermal performance and combustion characteristics. The high burnout of H2 and CO is obtained as 96.75% and 97.75%, respectively. The channels can be divided into three groups from the inside to the outside as follows: part 1, from the 9th channel to the 13th channel; part 2, from the 14th channel to the 16th channel; and part 3, the 17th channel. The channels in the same group presented the same results of flow, temperature, and combustion. Compared with the other channels, the outermost channel shows notable differences in depressing the temperature of the whole channel, moving the maximum temperature downstream, enlarging the temperature bias of the lower and upper walls, and enlarging the combustion zone. H2 and CO perform different combustion processes in the honeycomb ceramic catalytic burner. Compared with H2, the initial position of CO conversion is more affected by channel distribution. In the 17th channel, the CO oxidation rate is controlled mostly by the slower oxygen adsorption and the resulting low O(s) coverage. In the 9th channel, the CO oxidation rate is controlled mostly by the wall temperature and fuel-limited. The burnout rate of H2 changes from 95% to 99.9% with the channel position, but the burnout of CO varies little. The closer the channel to the outer wall, the higher the proportion of heterogeneous reaction and the more the generated heat. The generated heat by the channel can present a diversity of 4%.

Source analysis and health risk assessment of polycyclic aromatic hydrocarbon (PAHs) in total suspended particulate matter (TSP) from Bengbu, China

The polycyclic aromatic hydrocarbon (PAH) concentrations in total suspended particulate matter (TSP) samples collected from October, 2021 to September, 2022 were analyzed to clarify the pollution characteristics and sources of 16 PAHs in the atmospheric TSP in Bengbu City. The ρ(PAHs) concentrations ranged from 1.71 to 43.85 ng/m3 and higher concentrations were detected in winter, followed by spring, autumn, and summer. The positive matrix factorization analysis revealed that, in spring and summer, PAH pollution was caused mainly by industrial emissions, gasoline and diesel fuel combustion, whereas in autumn and winter, it was coal, biomass and natural gas combustion. The cluster and potential source factor analyses showed that long-range transport was a significant factor. During spring, autumn, and winter, the northern and northwestern regions had a significant impact, whereas the coastal area south of Bengbu had the greatest influence in summer. The health risk assessment revealed that the annual total carcinogenic equivalent concentration values for PAHs varied from 0.0159 to 7.437 ng/m3, which was classified as moderate. Furthermore, the annual incremental lifetime cancer risk values ranged from 1.431 × 10−4 to 3.671 × 10−3 for adults and from 6.823 × 10−5 to 1.749 × 10−3 for children, which were higher than the standard.

Life Cycle Environmental Assessment of Three Excavated Soil and Rock (ESR) Treatment Methods: A Case Study in Shenzhen City

This study aimed to quantitatively assess the environmental impacts of different methods used for treating excavated soil and rock (ESR) in Shenzhen, namely landfilling, sintering, and non-sintering, using the life cycle assessment (LCA) method. The findings indicate that recycling ESR through sintering or non-sintering processes offers more sustainable alternatives than landfilling. The recycled products derived from ESR can effectively replace traditional building materials, thereby reducing their environmental impacts. However, when comparing the environmental impacts of sintering and non-sintering processes, the latter demonstrated more significant impacts, particularly in terms of global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP). Furthermore, it is worth noting that the environmental impacts of the sintering processes are influenced by fuel type and exhaust gas emissions, with natural gas combustion yielding more substantial overall environmental benefits. Moreover, ESR landfilling poses constraints on sustainable development and land resource occupation. This study contributes to a better understanding of the environmental impacts associated with ESR landfilling and recycling, provides management departments with optimal ESR management suggestions, and alleviates environmental pressure from urban development.

Optimization Of Gas Turbine Performance 2.1 Using the Overhaul Combustion Inspection Method

Gas turbines are one type of internal combustion drive, the initial mover utilizes gas combustion as a fluid to rotate the turbine with internal combustion. Gas turbines at private companies producing electricity use the initial movers, namely gas turbines and steam turbines. Therefore, it is also called the "Steam Gas Power Plant/PLTGU.”Private company especially in Block 2, uses two gas turbine units with Mitsubishi GT 2.1 specifications which are used as the initial drive of the generator. Types of overhauls in gas turbines are divided into three, including turbine inspection, combustor inspection, and major inspection. In maintaining the reliability of the GT 2.1 Gas Turbine, an overhaul combustion inspection was carried out in the combustion chamber because there was an increase in heat rate of 17,9% which caused a decrease in thermal efficiency and net turbine power of the GT 2.1 Gas Turbine by 17% and 2,1%. So that steps are taken to optimize the GT 2.1 Gas Turbine with the combustion inspection method by repairing and cleaning the combustion bucket nozzle. Increased thermal efficiency by 27,8% or 27,13% to 36,01% from data before overhaul. This was also followed by an increase in compressor power and turbine power so that the net turbine power increased by 38% or 141339,35 hp to 195246,54 hp.

Experimental investigation on combustion and emission characteristics of non-premixed ammonia/hydrogen flame

The use of ammonia and hydrogen as fuels to decarbonise the heavy transport industry has attracted worldwide attention. In this work, a swirl-enhanced combustion test rig has been built to investigate the combustion and emission characteristics of non-premixed ammonia/hydrogen flames. The blowoff limits were first examined to ensure that a range of stable flames could be achieved. Emissions containing nitric oxide (NO), nitrous oxide (NO2), ammonia slip (NH3) and unburnt hydrogen (H2) were then measured with a variety of global equivalence ratios, hydrogen blending ratios, inlet gas temperature, swirl numbers and combustion chamber insulation conditions. The structure of non-premixed ammonia/hydrogen flames and the relationship between excited hydroxyl radicals (OH*) and NO emission were revealed using OH* chemiluminescence profiles. The stable non-premixed ammonia/hydrogen flames were achieved when the hydrogen blending ratio was greater than 20%. The optimal emission performance was achieved under stoichiometric conditions, as determined by combustion efficiency. The insulation conditions of the combustor wall played a key role in the emission results, as significant growth of NO and NO2 as well as a reduction of ammonia slip were found. Although a lower swirl number improved the flame stability range, the increases in NO and NO2 emissions were observed.

Ignition and combustion characteristics of micro/nano-Al and Al@Ni alloy powders at elevated pressures

Nanosizing and alloying of aluminum (Al) promisingly improve ignition and combustion performance of Al-based propellants. To aim this, lased-induced ignition and combustion characteristics of micro/nano-Al and aluminum@nickel (Al@Ni) alloy powders at elevated pressures (0.1–3.0 MPa) were investigated and the pressure effect on these characteristics was correspondingly evaluated. Comparative results demonstrate that nanosizing and alloying significantly shorten ignition delay and total burn time at elevated pressures, with ignition delay reduction of 98.04% and 52.28% at 1.0 MPa for nano-Al and Al@Ni alloy compared to micro-Al counterpart. Nanosizing and alloying can decrease crucial pressure values (‘mid-pressure extinction domains’) influencing ignition delay, and promote the transfer from the surface to gaseous combustion mode. Maximum combustion temperatures of nano-Al are higher than micro-Al and Al@Ni alloy. During combustion, the combustion of Al@Ni alloy is further intensified due to the microexplosion, while possibly inhibited at higher pressures.

Experimental and modeling study of full- condition combustion characteristics of exhaust gas burners for solid oxide fuel cells

SOFC exhaust gas burner is an essential component of the SOFC thermal management system. The burner in the whole operating conditions of safe and stable combustion and smooth transition in the switching operating conditions is of great significance to the long-term and efficient operation of the SOFC power generation system. This paper builds an experimental test platform for the SOFC exhaust gas burner, tests the combustion performance of the burner in full operating conditions and operating conditions switching process, and establishes a prediction model for the combustion performance of SOFC exhaust gas burner by machine learning algorithm. The results show that the SOFC exhaust gas burner can meet the requirements of safe and stable combustion in all operating conditions and smooth transition between operating conditions; reliable combustion is achieved at the stable power generation condition with excess air factor of 7 ∼ 26, and the average cathode and anode pressure drop in the stable power generation condition is 142 Pa and 185 Pa, respectively; BP neural networks, support vector machines and random forests are used to establish a prediction model for the performance of the SOFC exhaust gas burner, and the random forests achieve the best prediction effect.

Formaldehyde Exposure Racial Disparities in Southeast Texas.

Formaldehyde (HCHO) exposures during a full year were calculated for different race/ethnicity groups living in Southeast Texas using a chemical transport model tagged to track nine emission categories. Petroleum and industrial emissions were the largest anthropogenic sources of HCHO exposure in Southeast Texas, accounting for 44% of the total HCHO population exposure. Approximately 50% of the HCHO exposures associated with petroleum and industrial sources were directly emitted (primary), while the other 50% formed in the atmosphere (secondary) from precursor emissions of reactive compounds such as ethylene and propylene. Biogenic emissions also formed secondary HCHO that accounted for 11% of the total population-weighted exposure across the study domain. Off-road equipment contributed 3.7% to total population-weighted exposure in Houston, while natural gas combustion contributed 5% in Beaumont. Mobile sources accounted for 3.7% of the total HCHO population exposure, with less than 10% secondary contribution. Exposure disparity patterns changed with the location. Hispanic and Latino residents were exposed to HCHO concentrations +1.75% above average in Houston due to petroleum and industrial sources and natural gas sources. Black and African American residents in Beaumont were exposed to HCHO concentrations +7% above average due to petroleum and industrial sources, off-road equipment, and food cooking. Asian residents in Beaumont were exposed to HCHO concentrations that were +2.5% above average due to HCHO associated with petroleum and industrial sources, off-road vehicles, and food cooking. White residents were exposed to below average HCHO concentrations in all domains because their homes were located further from primary HCHO emission sources. Given the unique features of the exposure disparities in each region, tailored solutions should be developed by local stakeholders. Potential options to consider in the development of those solutions include modifying processes to reduce emissions, installing control equipment to capture emissions, or increasing the distance between industrial sources and residential neighborhoods.

Research on Dual Fuel Combustion Characteristics of PFI Natural Gas +DI Gasoline in Large Cylinder Diameter Engine

A 3D simulation model of a single cylinder of a natural gas engine was established. PFI natural gas DI gasoline was used to control the time matching between injection and ignition, so that gasoline could form a small active stratified area near the spark plug. The combustion characteristics under different matching conditions were studied, and finally compared with pure natural gas. It is found that gasoline can be used in large cylinder diameter natural gas engine in a small range, which can accelerate the combustion of natural gas fuel, shorten the time used by CA0-CA5 by 77.6%, shorten the time used by CA5-CA90 by 26.5%, and increase the indicated thermal efficiency of natural gas engine by 1.4%.

Study on the Influence of Different Gas Concentrations on Coal Spontaneous Combustion

ABSTRACT The coexistence of gas and spontaneous coal combustion poses a serious threat to mine production safety. Therefore, studying the compound disaster of gas and spontaneous coal combustion and revealing the impact of gas concentration on the characteristic parameters of coal spontaneous combustion are of great significance for understanding the mechanism of compound disasters involving coal and gas and for comprehensive management. Based on theoretical analysis, this paper selects four typical types of cannel coal、non-caking coal、meager coal、anthracite coal as research subjects, and conducts programmed heating experiments on coal samples under different gas concentration conditions, aiming to provide a theoretical basis for the prevention and control of spontaneous coal combustion in a gas environment. Experimental results show that with the increase in temperature of the coal samples, the oxygen consumption rate and heating emission intensity exhibit a trend of slow increase followed by rapid increase. With the increase in gas concentration in the environment, the production of CO and CO2, oxygen consumption rate, and heat emission intensity of coal spontaneous combustion all show a decreasing trend. This is mainly because the high gas concentration occupies the adsorption sites on coal molecules, thereby hindering the reaction between coal and oxygen. Additionally, by calculating the thermodynamic parameters of the coal samples, it was found that the apparent activation energy increases with the increase in gas concentration, further confirming that the increase in gas concentration in the environment significantly inhibits the spontaneous combustion process of coal.

Improvement energy performance for GHG mitigation - a case of FPSO vessel platform in Oil & Gas offshore production

This study offers an in-depth review of specific facets of the oil and gas industry, emphasizing the role of Floating Production, Storage, and Offloading (FPSO) vessels. It delves into diverse topics, highlighting potential opportunities, a solid research methodology for emissions quantification, and the pivotal challenge of reducing GHG emissions. Among the multitude of opportunities analyzed within the industry's value chain, the upstream sector - encompassing both exploration and production of oil and natural gas - receives considerable focus. This sector can be further divided into key segments characterized by high energy consumption and consequent significant emissions. Notably, the combustion of natural gas for power generation stands out, contributing a substantial 68% of CO2 emissions at related facilities. This process is a primary target for mitigation and energy efficiency enhancements. The intricate interplay between energy generation and CO2 emissions stands at the forefront of current research, emphasizing the need for improving vessel energy efficiency. This paper employs a case-based methodology, evaluating the effectiveness of energy efficiency measures within an FPSO setting and their resulting impact on GHG emissions. Central to this inquiry is a detailed examination of the FPSO Fluminense, strategically located within Brazil's Campos Basin, with the study meticulously examining the relationship between advancements in energy efficiency and emission reductions. While translating these insights into practical applications poses challenges, the momentum generated by rigorous research, combined with policy recommendations addressing GHG emissions in the oil sector, can indeed chart a path toward a more robust, sustainable, and integrated energy future.

Risk analysis and production safety design of supercritical carbon dioxide storage in gasification combustion cavity

The storage of supercritical carbon dioxide in the coal underground gasification combustion cavity can not only reduce greenhouse gas emissions, help control global climate change, but also avoid potential geological hazards caused by the long-term existence of coal-burning holes. It is an important innovative development direction for the global coal industry. However, currently, there is insufficient examination of the practicality and hazards of UCG-CCS through industrial trials, which considerably restricts the spread and use of UCG-CCS. This study employs theoretical analysis and numerical simulation to examine the geological feasibility of UCG-CCS. It finds that the risk of carbon dioxide leakage in UCG-CCS is predominantly due to overlying rock fractures being diffused by the integrity of the cover layer and the parameters of the gasification furnace. It has also been found that the development height of cap rock fractures is closely related to CO2 injection pressure and gasification furnace width. As CO2 injection pressure increases, the capping fracture exhibits a descending trend resembling a stair-step; as gasification furnace width decreases, the development height of cap rock fractures decreases. On this basis, the technical approach and design method of preventing carbon dioxide leakage in UCG-CCS are proposed. The research findings have significant theoretical and practical implications for site selection and risk assessment in UCG-CCS process engineering.

Black carbon instrument responses to laboratory generated particles

Accurate measurement of black carbon (BC) particles is vital for climate models as well as air quality assessments. While the need for BC particle measurement has been recognized, standardization of instruments and procedures for ambient measurement is still underway. In this study, we used laboratory generated soot particles to assess nine instruments targeting BC mass concentration measurement. The measurement matrix included different BC concentrations (ranging from atmospheric levels to combustion emission levels), different particle coatings, two particle sources (gas burner and spark generator) and two dilution methods. The nine instruments included six different models: aethalometers AE33 and MA200, thermo-optical OC-EC analysis, multi-angle absorption photometer MAAP 5012, photoacoustic instrument MSS, and soot particle aerosol mass spectrometer SP-AMS. The main discrepancy we observed was that the SP-AMS results were systematically lower, approximately only half of the BC measured by other instruments. A portion of this is explained by particle losses in the aerodynamic lens of the SP-AMS and the parameters used in the data analysis. Some smaller discrepancies were identified for the other instruments, but overall, the median values from were within 25 % of each other. Instruments’ operation principles and covered concentration ranges need to be carefully considered especially in emission measurements where the aerosols can have high temporal variation as well as high BC concentrations. In general, the results can decrease the uncertainties in climate and air quality studies by providing tools for more accurate and comparable BC measurements and when the existing BC data is interpreted.

Dynamic Response Mechanism of Ethanol Atomization–Combustion Instability under a Contrary Equivalence Ratio Adjusting Trend

This study experimentally explored the effects of equivalence ratio settings on ethanol fuel combustion oscillations with a laboratory-scale combustor. A contrary flame equivalence ratio adjusting trend was selected to investigate the dynamic characteristics of an ethanol atomization burner. Research findings denote that optimizing the equivalence ratio settings can prevent the occurrence of combustion instability in ethanol burners. In the combustion chamber, the sound pressure amplitude increased from 138 Pa to 171 Pa and eventually dropped to 38 Pa, as the equivalence ratio increased from 0.45 to 0.90. However, the sound pressure amplitude increased from 35 Pa to 199 Pa and eventually dropped to 162 Pa, as the equivalence ratio decreased from 0.90 to 0.45. The oscillation frequency of the ethanol atomization burner presents a migration characteristic; this is mainly due to thermal effects associated with changes in the equivalence ratio that increase/decrease the speed of sound in burnt gases, leading to increased/decreased oscillation frequencies. The trend of the change in flame heat release rate is basically like that of sound pressure, but the time-series signal of the flame heat release rate is different from that of sound pressure. It can be concluded that the reversible change in equivalence ratio will bring significant changes to the amplitude of combustion oscillations. At the same time, the macroscopic morphology of the flame will also undergo significant changes. The flame front length decreased from 25 cm to 18 cm, and the flame frontal angle increased from 23 to 42 degrees when the equivalence ratio increased. A strange phenomenon has been observed, which is that there is also sound pressure fluctuation inside the atomized air pipeline, and it presents a special square waveform. This study explored the equivalence ratio adjusting trends on ethanol combustion instability, which will provide the theoretical basis for the design of ethanol atomization burners.

Analysis of Calophyllum Inophyllum Biodiesel Combustion with Variations of Magnetic Field Strength

The problems facing the world today are limited fossil fuels and increasing global warming due to fuel emissions. Therefore, there is a need to transition from fossil energy to alternative energy that is environmentally friendly and renewable. Biodiesel is an alternative material that can be used as a substitute for diesel fuel. This research aims to improve the combustion quality of calophyllum inophyllum biodiesel using the magnetic field influence method. The combustion test method uses a Bunsen burner and variations in magnetic strength of 4000 gauss, 8000 gauss and 12000 gauss are given. The equivalent ratios used in combustion analysis are 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1:1.1, and 1:1.2. The fuel and air flowing in the Bunsen pipe are heated to a constant temperature of 250°C for the fuel evaporation process. Then the resulting flame was analyzed for its combustion characteristics with RGB color variables, laminar burning velocity, and flame height. The research results show that the stronger the magnetic field effect, the more optimal the combustion quality will be. This is indicated by the increasingly strong magnetic field effect exerted on the flame, causing the red color intensity to decrease, the laminar burning velocity to increase, and the flame height to decrease. This is because the magnetic field can influence the movement of O2 molecules and cause a change in the orientation of the hydrocarbon from para to ortho. As a result, diffusion combustion becomes minimal and the combustion reaction becomes faster.

Experimental Investigation of the Effect of the Burner Cap Geometry on the Performance of a Domestic Liquefied Petroleum Gas Stove

Abstract Cooking is an important domestic activity that needs energy. Traditionally, solid fuels such as firewood and charcoal have been used. However, the combustion of solid fuels inside households causes internal pollution and harms the health of users and other occupants. Nowadays, gaseous fuels like natural gas (NG) and liquefied petroleum gas (LPG) are the most used for domestic cooking. Considering the limitation of fossil fuel resources, energy conservation issues, environmental problems, and the increase in demand for gaseous fuels, it is necessary to explore ways to improve the thermal efficiency and emission characteristics of existing cooking systems. Although the use of gaseous fuels reduces domestic air pollution, the earliest domestic gas burners have low heat performance with an efficiency value of approximately 40%. Continuous research and development in stove design and analysis has led to a significant improvement in the thermal performance of commercial gas burners, with efficiencies exceeding 60%. This study’s main objective is to improve an LPG domestic stove through the modification of the cap burner geometry. The effects of various inclination angles (between the top and the lateral cap faces) ranging from 0 deg to 90 deg have been experimentally investigated. Results demonstrated that the thermal efficiency of the burner increases with increasing inclination angle. The highest efficiency was obtained at an angle of 75 deg, and beyond this value, the efficiency dropped. Unfortunately, at this angle value, CO emissions were the highest.

Impact of Gas Flaring on the Environment in the Kurdistan Region of Iraq

Gas flaring is a common practice in the oil and gas industry that involves the burning of natural gas during the extraction and processing of crude oil. Despite its economic benefits, gas flaring has significant negative impacts on the environment. This paper explores the various ways in which gas flaring affects the environment, including the emission of greenhouse gases, air pollution, acid rain, and the destruction of ecosystems. It used a cross-sectional survey research design in generating the primary data used for the study, while the location of the study is Kurdistan. It used a sample size of 375 from a population of 6000 Oil & Gas company workers in Kurdistan. The findings of the study suggest that the negative impacts of gas flaring on the environment are significant, and requires urgent action to mitigate its effects. This paper provides valuable insights for policymakers, stakeholders and researchers interested in addressing the environmental consequences of gas flaring in the oil and gas industry.

Aspects using of CO2 captured from stationary sources

The results of carbon dioxide (CO2), which is emitted into the atmosphere and creates a greenhouse effect as a result of the burning of natural methane gas (CH4) as a fuel in a number of large industrial enterprises in Azerbaijan, and the ways of its capture and efficient use from an economic point of view have been studied. Including, in the production of methanol and urea sulfur, increasing the oil yield of the layer by injecting it into the oil layers, increasing the productivity of plants, producing caustic soda, dry ice, carbonated water, etc. the effectiveness of its use in the fields has been investigated and proposals for scientific and technical solutions have been developed. This is both a decrease in the amount of CO2 gas in the atmosphere, which causes global climate changes, and also a saving of natural methane gas used in the production process. Options for carbon dioxide capture and storage and transportation to the destination have also been developed in the current research work.

Pollution Characteristics，Source Analysis，and Activity Analysis of Atmospheric VOCs During Winter and Summer Pollution in Zhengzhou

In order to study the pollution characteristics of volatile organic compounds （VOCs）， continuous monitoring of VOCs in two pollution processes was conducted in June and December 2021 in Zhengzhou. Combined with meteorological conditions， the pollution characteristics， source contributions， and reactivity of VOCs in winter and summer were compared and analyzed. The results showed that the volume fraction of atmospheric VOCs in two episodes were （27.92±12.68）×10-9 and （24.30±5.93）×10-9， respectively. The volume fraction of atmospheric VOCs in the haze pollution process in winter was larger than that in the ozone pollution process in summer. The analysis results of winter sources were as follows： industrial source （27.0%）， motor vehicle source （22.5%）， combustion source （20.1%）， solvent use source （16.3%）， and oil and gas volatilization source （14.1%）. The analysis results of summer sources were as follows： motor vehicle source （24.8%）， industrial source （24.1%）， solvent source （17.4%）， oil and gas volatilization source （14.2%）， combustion source （11.2%）， and plant source （8.4%）. The results of the smog production model showed that the proportion of days in the synergistic control zone of VOCs during the two pollution processes in summer （66.7%） was smaller than that in winter （100.0%）. The secondary reaction activity results showed that the average ·OH loss rate （L·OH） values in winter and summer were 4.12 s-1 and 4.75 s-1， respectively. The average ozone formation potential （OFP） values in summer were 108.36 μg·m-3. The olefins were dominant in the top ten species due to L·OH and OFP contributions in summer. The total SOAFP values in winter in Zhengzhou were 54.38 μg·m-3. Among the top ten species contributing to SOAFP in winter， nine were aromatic hydrocarbons.