Distribution Of CO2 Concentration Research Articles

An improved prediction model for miscibility characterization and optimization of CO2 and associated gas co-injection

Insufficient reservoir pressure and gas source problems seriously limit effective applications of CO2 flooding in hydrocarbon reservoirs. An attractive strategy is to co-inject the produced associated hydrocarbon gas with CO2 to achieve miscible/near-miscible flooding to enhance oil recovery. However, the composition of the injected mixture and the in-situ spatio-temporal composition evolution of the displacing/displaced fluids significantly affect the CO2-oil miscibility and the overall hydrocarbon recovery performance. In this work, based on slim tube simulation results, a prediction model of minimum miscible pressure (MMP)/minimum near-miscible pressure (MNMP) is established. This model takes into account the effects of CO2 concentration distribution, oil composition and temperature changes to achieve accurate spatiotemporal characterization of miscibility in the reservoir. In addition, the distribution law of the phase and components front for the impure CO2 injection process was also investigated. The miscible volume factor and recovery efficiency were used as the basis for judging the minimum injection concentration limit of CO2. The simulation results of slim tube experiment indicate that the MMP and MNMP obtained are 16.74 MPa and 12.35 MPa, respectively. Furthermore, the error caused by the traditional slim tube experiment can be reduced by using the CO2 produced fraction. It is found that CO2 injection concentration and reservoir temperature are the main factors affecting miscibility, but injection rate has less effect. Moreover, the fast migration of CH4 front leads to the shrinkage of miscible/near-miscible zone, which is not conducive to CO2 flooding. Finally, the CO2 injection concentration of non-breakthrough stage, breakthrough stage and large-scale breakthrough stage was determined to be 78.3%, 61.5% and 29.2%, respectively. This work provides strong evidence for the treatment of associated gas reinjection, which is beneficial for optimization of carbon capture, EOR-utilization and storage (CCUS-EOR) projects.

Assessment of airborne viral transmission risks in a large-scale building using onsite measurements and CFD method

Screening patients for potential respiratory infections through nucleic acid sampling was a critical non-pharmacologic intervention during a respiratory infectious disease pandemic. Evaluating the cross-infection risk of crowded activities conducted indoors is necessary. We conducted a field study of this event in a large-scale stadium and measured the variation in CO2 concentrations. We conducted simulations on the stadium's flow field, CO2 and N2O concentration distribution using the CFD method, which was validated by the on-site measured data. We simulated the diffusion of virus aerosols exhaled by the sampled individuals under an all-fresh and primary return air system, respectively. It was found that space morphology and airflow pattern are the main factors influencing the concentration distribution of human exhaled contaminants. Primary return air systems can reduce the infection risk for sampled individuals by the filtration system and improve the airflow pattern. With the ratio of fresh air to return air of 1.2, the primary return air systems with 70 %, 85 %, and 95 % filtration levels can reduce the infection risk by an average of 54.5 %, 58.3 %, and 62.1 %, respectively, compared to all-fresh air system. It is necessary to optimize the processes and queue setups for nucleic acid sampling activities in the room based on the room airflow characteristics and the return air system using an efficient filtration system.

Investigation of Pipeline CO2 Leakage and Diffusion on Offshore Platforms Based on Numerical Simulation.

Pipeline transportation of CO2 is the key link to realize carbon capture, utilization, and storage. CO2 pipeline transportation may face the risk of leakage, which poses a great threat to the production process and personnel safety. It is of great significance to study the leakage and diffusion characteristics of CO2 in pipeline transportation for the safety design and personnel protection of the offshore CO2 storage platform. In order to study the leakage and diffusion characteristics of CO2 in pipeline transportation on offshore platforms, a physical model of a target platform and several numerical models were built, and a series of pipeline CO2 leakage and diffusion simulations were carried out using the method of numerical simulation. Based on the simulation results, the temperature distribution and CO2 concentration distribution on the offshore platforms after leakage were measured and analyzed. The influence of leakage direction (horizontal and oblique 45° upward) was also studied. Dangerous areas on the platform and suggestions for staff evacuation were given according to the simulation results. The research results of this work can provide guidance for the safe operation of offshore CO2 storage platforms.

An integrated experimental and CFD analysis of ceiling-fan-integrated air conditioning system: Indoor air quality and air velocity

The Ceiling-Fan-Integrated-Air Conditioning (CFIAC) represents an innovative HVAC design, which involves directing supply air towards the vicinity of ceiling fans, facilitating the mixture and distribution of air within a room. By eliminating the need for terminal ductwork and diffusers, CFIAC offers an efficient cooling solution for occupants. This study employs experimental and CFD methodologies to assess various parameters, including airflow, air pollution, and temperature related to this system. Experimental tests were conducted in a controlled chamber, with the lowest inlet air velocity and the temperature, where supply air was projected from a high-sidewall vent directly towards a ceiling fan's centerline. Different operational conditions of the ceiling fan were examined (off, Level 2 and Level 4 downwards, and Upwards). Carbon dioxide (CO2), employed as a tracer gas, was released near a thermal manikin at three distinct locations within the chamber: the middle, lower left, and upper right, and the corresponding CO2 concentration distributions were evaluated. Additionally, air velocity measurements were collected and analyzed. The effectiveness of ventilation and potential health exposure was quantified using the age of air and intake fraction (IF) metrics. The findings indicate that operating the fan at Level 4 with downward airflow enhances air velocities and heat loss while reducing CO2 concentrations and age of air by an average of 14 % and 4 min, respectively. Moreover, the IF values for Level 4 operations, both downward and upward, were marginally lower compared to those recorded for Level 2 downward and fan-off scenarios, suggesting a decreased risk of cross-infection.

Study on fire characteristics of lithium battery of new energy vehicles in a tunnel

In order to explore fire safety of lithium battery of new energy vehicles in a tunnel, a numerical calculation model for lithium battery of new energy vehicle was established. This paper used eight heat release rate (HRR) for lithium battery of new energy vehicle calculation models, and conducted a series of simulation calculations to analyze and compare the fire development characteristics of fuel vehicles and new energy vehicles with different HRR in a tunnel. This paper investigated temperature distribution below the ceiling and smoke diffusion in a tunnel, as well as the distribution of CO2 and CO concentrations, to explore the spread of lithium battery of new energy vehicle fires in a tunnel. Then, the accuracy of the numerical simulation was verified through comparison with existing examples. The results showed that there is a correlation between the temperature distribution below the ceiling in a tunnel and the HRR of lithium battery of new energy vehicle fires, with higher HRR and higher temperature below the ceiling in a tunnel. In addition, the heat release of fuel vehicles in a tunnel is lower than that of lithium battery of new energy vehicles. The analysis of the ceiling temperature of new energy vehicles in tunnels after a fire showed that for different HRR, the temperature below the ceiling increases with the increase of HRR. In tunnel fires, lithium battery of new energy vehicles generate higher temperature, smoke, and CO emission concentrations than fuel vehicles. Therefore, the risk of fire for lithium battery of new energy vehicles in tunnels is higher than that of fuel vehicles, and their fire safety needs to be paid more attention.

Distribution of exchangeable cobalt in low-land rice cultivated soils in Sri Lanka as affected by the differences in climate, soil and water source

Cobalt (Co) is considered a beneficial element for plants. However, when soils contain excessive amounts of Co, it could cause phytotoxicity. Despite this, the current status of Co in Sri Lankan rice-cultivated soils is not known. Therefore, this study was conducted to (i) determine the distribution of exchangeable Co concentration, and (ii) examine the interactive effects of climatic zone (CZ), agro-climatic zone (ACZ), soil order, water source, and their interactions in determining exchangeable Co concentration in lowland rice fields in Sri Lanka. A total of 8,292 soil samples representing six ACZs, six soil orders, and three water sources were collected using a stratified random sampling approach. Cobalt was extracted in 0.01 M CaCl2 and measured using Inductively Coupled Plasma Mass Spectrophotometry. Exchangeable Co concentration ranged between 0.03-2,409 μg kg−1 with a mean value of 185.9 μg kg−1. Over 77.5% of the soil samples tested were Co deficient, i.e. <250 μg kg−1. Samples collected from the Intermediate zone, particularly Intermediate zone Mid country, had higher Co concentration than that reported in other ACZs (p<0.05). Among the soil orders, Histosols had higher (232 μg kg−1) and Vertisols had lower (91 μg kg−1) Co concentrations (p<0.05). Moreover, Co concentration was negatively correlated with soil pH (r=−0.3391, p<0.0001) and rice crop productivity (r=−0.1512, p<0.0001). Although exchangeable Co concentration in rice cultivated soils was low, it is important to implement strategies such as proper waste management, treatment of industrial effluents, and the use of safer and more sustainable practices in the chemical and mining industries to minimize further accumulation of Co exceeding the critical limit (i.e. 30 - 40 mg Co kg−1 rice grain), and to ensure the safety of rice production in situations where geological and anthropogenic activities can increase soil exchangeable Co concentration.

Predicting high-resolution air quality using machine learning: Integration of large eddy simulation and urban morphology data

Accurately predicting air pollutants, especially in urban areas with well-defined spatial structures, is crucial. Over the past decade, machine learning techniques have been widely used to forecast urban air quality. However, traditional machine learning approaches have limitations in accuracy and interpretability for predicting pollutants. In this study, we propose a convolutional neural network (CNN) model to predict the spatial distribution of CO concentration in Nanjing urban area at 10 m resolution. Our model incorporates various factors as input, such as building height, topography, emissions, and is trained against the outputs simulated by the parallelized large-eddy simulation model (PALM). The PALM model has 48 different scenarios that varied in emissions, wind speeds, and wind directions. The results display a strong consistency between the two models. Furthermore, we evaluate the performance of our model using a 10-fold cross-validation and out-of-sample cross-validation approach. This yields a robust correlation (with both R2 > 0.8) and a low RMSE between the CO predicted by the PALM and CNN models, which demonstrates the generalization capability of our CNN model. The CNN can extract crucial features from the resulted weight contribution map. This map indicates that the CO concentration at a location is more influenced by nearby buildings and emissions than distant ones. The interpretable patterns uncovered by our model are related to neighborhood effects, wind speeds, directions, and the impact of orientation on urban CO distribution. The model also shows high prediction accuracy (R > 0.8) when applied to another city. Overall, the integration of our CNN framework with the PALM model enhances the accuracy of air quality predictions, while enabling a fluid dynamic laws interpretation, providing effective tools for air quality management.

The Spatio-Temporal Distribution Characteristics of Carbon Dioxide Derived from the Trajectory Mapping of Ground Observation Network Data in Shanxi Province, One of China’s Largest Emission Regions

In this study, the trajectory mapping domain-filling technology, which can provide more reliable statistical estimates of long-lived gas concentrations in a broader geographical area based on limited station data, is used to map the CO2 concentration data of six ground observation stations to the entire Shanxi Province. The technology combines a dynamical model of the atmosphere with trace gas observations, combining forward and backward trajectories to greatly expand the information on long-lived CO2 gas concentrations over a trajectory path. The mapped results show good agreement with the observation results, which reveals the generalizability of the trajectory mapping domain-filling technology. The results show that the spatio-temporal distribution characteristics of CO2 concentration in the entire Shanxi region is significant: during the five years, the provincial average CO2 concentration exhibits an overall increasing trend. The CO2 concentration increases from the north to the south across the province. Influenced by the economic growth rate and COVID-19, there are differences in the annual variation characteristics of the CO2 concentration across the entire province, with the highest year-on-year growth in 2019 and a year-on-year decrease in 2020. The increasing rate of the CO2 concentration in the northern low-value areas is faster than that in the southern high-value areas. Overall, there is a decreasing trend in the CO2 concentration growth from the north to the south in the entire province. There are seasonal differences in the CO2 concentration distribution across the entire province. The CO2 concentration and amplitude are higher in autumn and winter than they are in spring and summer. This study can provide scientific support and methodological reference for the spatio-temporal distribution characteristics analysis of GHGs at the provincial–regional scale, as well as at the national and global scales.

3D models guide the design of hollow fiber membrane contactors with complex internal structures for CO2 capture

AbstractMembrane contactors have good prospects in the field of CO2 capture. In this study, the effects of operation conditions (gas velocity, liquid flow, CO2 pressure, amine concentration, and CO2 loading) on CO2 absorption flux (JCO2) for CO2 absorption into N‐methyl‐4‐piperidinol (MPDL) solution in membrane contactors were investigated through experiments and simulations. A three‐dimensional (3D) model was developed using COMSOL Multiphysics software to study the comprehensive CO2 mass transfer process in the multifiber membrane contactor and the effect of the number of fibers on the flow and CO2 concentration distribution without simplifying the geometry compared with those of traditional one‐dimensional (1D) and two‐dimensional (2D) models. Non‐ideal effects occurring in hollow fiber membrane contactors can be explained using a 3D modeling. By comparing the simulated with the experimental , the effectiveness of the model was determined. The simulation results emphasize that the spatial concentration distribution has a great correlation with the corresponding velocity distribution. Additionally, reducing the uneven velocity distribution of gas and liquid is a very important factor to improve the mass transfer performance of CO2. Increasing the number of fibers with a constant total volumetric flux can reduce the thickness of the boundary layer and promote the mass transfer.

Numerical investigations of supersonic combustion characteristics of thermally cracked fuels at typical pyrolysis temperatures

Insight into supersonic combustion characteristics of thermally cracked fuels in a scramjet combustor is crucial for the development of next-generation supersonic flight vehicles. In the present study, four typical thermally cracked fuels at pyrolysis temperatures of 450, 550, 600, and 650 ℃ (denoted as ckori, ck550, ck600, and ck650) were selected. Improved delayed detached eddy simulation (IDDES) modeling with a compact skeletal mechanism and a transported multi-regime flamelet model was carried out to simulate the supersonic combustion of the target fuels in a full-scale scramjet combustor. Supersonic flow, mixing, and combustion characteristics of these fuels were quantitatively compared. Discrepancies in the combustion process are mainly at the cavity region, where the mixing efficiencies and combustion intensities of the first three fuels increase monotonically with the increasing pyrolysis temperature, while that of ck650 locates between ck550 and ck600. The increase in pyrolysis gas content will enhance the mixing process, while the increase in injection pressure will suppress the heat/mass transport between fuel and incoming air. The mixing process dominates the distributions of intermediate radicals and main products. The first three fuels tend to combust under fuel-rich condition, while ck650 tends to combust under the stoichiometric condition, which explains the distributions of OH, CO, and CO2 concentrations. The premixed and non-premixed combustion modes coexist in the model scramjet combustor, and the non-premixed combustion mode dominates the combustion process of thermally cracked fuel.

Eco-friendly strategy for CO2 enrichment performance in commercial greenhouses based on the CO2 spatial distribution and photosynthesis

CO2 enrichment is an essential environmental control technology due to its significantly enhancing effect on crop production capacity. Despite being a key energy consumer in protected agriculture (i.e. greenhouse systems), CO2 enrichment remains at a low energy use efficiency level, highlighting the need for developing more energy-efficiency strategies for CO2 enrichment. Therefore, this study employed the computational fluid dynamics (CFD) simulation method to replicate the CO2 diffusion process resulting from CO2 enrichment in three commercial strawberry greenhouses with varying geometric characteristics. Based on the CFD-simulated CO2 concentration distributions, the leaf photosynthetic rate was calculated using a mathematical model group. The CO2 enrichment efficiency was then analysed by calculating the ratio of increased photosynthesis across the cultivation area to the amount of energy (in CO2 equivalent) used. The efficiency peaked when the average CO2 concentration was approximately 500 μmol mol−1, thereby providing guidance for determining the target concentration of CO2 enrichment in production. Although this study is limited as the CFD simulation only considered a typical short-period CO2 enrichment event, future research will provide a broader analysis by considering changes throughout the day.

Study on Spatial and Temporal Distribution Characteristics of the Cooking Oil Fume Particulate and Carbon Dioxide Based on CFD and Experimental Analyses

The cooking oil fume particulate (COFP) produced by indoor cooking can harm human health seriously, and therefore requires urgent monitoring and optimization. In this paper, the kitchen cooking simulation process was established by using computational fluid dynamics (CFD) based on the fluid dynamics theory. Combined with the user defined function (UDF), the spatial and temporal distributions of COFP and carbon dioxide (CO2) during the cooking process were simulated and analyzed, respectively. Both simulation results were verified using experimental data. Moreover, this paper introduces a COFP concentration correlation function that utilizes the spatiotemporal correlation between COFP and CO2 concentrations during the cooking process. The function is based on the spatiotemporal distribution of CO2 concentration. By comparing it with traditional calculations, the proposed function is shown to achieve a remarkable 70% improvement in efficiency and maintain an accuracy rate exceeding 90%. This enables the rapid analysis and control of COFP concentration through monitoring and analyzing CO2 levels in the kitchen.

Numerical Simulation of the Ventilation and Fire Conditions in an Underground Garage with an Induced Ventilation System

The increasing quantity of air pollutants generated by automobiles can cause significant harm in relatively enclosed indoor environments. Studying the distribution of pollutants under different conditions in underground parking garages is of great significance for improving indoor air quality and reducing casualties in the event of a fire. This article presents a geometric model of an underground parking garage based on PHOENICS modeling. The related results of CO concentration distribution and fire temperature distribution under ventilation and fire conditions are obtained. Based on the CO concentration and velocity distribution as well as the temperature distribution during a fire, reasonable suggestions are proposed to improve indoor air quality and reduce casualty rates in fire incidents. The results show that under ventilation conditions, adjusting the position of the induced ventilation fan can maintain CO concentrations below 30 ppm in partitions one to three and below 37 ppm in partitions four to six. The temperature of smoke gases remained below 50 °C during the evacuation time, and only a small area exhibited CO levels exceeding 2000 ppm. The existing ventilation exhaust system provides effective fire protection, as it minimally affects personnel evacuation due to the relatively lower smoke temperature.

Improving atmospheric CO2 retrieval based on the collaborative use of Greenhouse gases Monitoring Instrument and Directional Polarimetric Camera sensors on Chinese hyperspectral satellite GF5-02

ABSTRACT The Greenhouse Gas Monitoring Instrument (GMI) onboard the Chinese hyperspectral satellite GF5–02 can provide abundant observations of global atmospheric CO2, which plays an important role in climate research. CO2 retrieval precision is the key to determining the application value of the GMI. To reduce the influence of atmospheric scattering on retrieval, we combined the Directional Polarimetric Camera (DPC) data on the same satellite to improve the anti-interference ability of GMI CO2 retrieval and ensure its retrieval precision. To realize the reliability and feasibility of the collaborative use of the GMI and DPC, this paper designs the pointing registration method of the GMI based on coastline observations, the spatial resolution matching method and the collaborative cloud screening method of the GMI and DPC observations. Combined with the DPC, which supplied the spectral data and aerosol product, the retrieval ability of the coupled bidirectional reflectance distribution function CO2 retrieval (CBCR) method developed for GMI CO2 retrieval was improved, with the retrieval efficiency of CO2 products increasing by 27%, and the CO2 retrieval precision increasing from 3.3 ppm to 2.7 ppm. Moreover, collaborative use not only guaranteed the GMI’s ability to detect global and area CO2 concentration distribution characteristics, such as significant concentration differences between the Northern and Southern Hemispheres in winter and high CO2 concentrations in urban agglomeration areas caused by human activities, but also extended the GMI’s potential for monitoring anomalous events, such as the Tonga volcanic eruption.

Influence of Urban Spatial Structure on the Spatial Distribution of Gaseous Pollutants

The spatial distribution pattern of urban spatial structure affects air flow and local meteorological conditions, which in turn influence the diffusion of air pollutants. This study built the urban spatial structure index system based on DEM, urban road networks, and big data. The ordinary kriging interpolation method was used to analyze the spatial distribution of gaseous pollutant concentrations in Jinan City. Correlation analysis, stepwise regression analysis, and bivariate global spatial autocorrelation analysis were used to study the influence of the urban spatial structure index on the spatial distribution of gaseous pollutant concentration. The main conclusions were as follows: (1) Evident spatial and temporal differences were observed in the concentration distribution of gaseous pollutants in Jinan. The spatial distribution of NO2 and CO concentrations showed a gradual decrease from north to south. Spatial heterogeneity was observed in the distribution of SO2 and O3 concentrations. (2) The urban spatial structure indicators had varying effects on the spatial distribution of different gaseous pollutant concentrations. The important factors that influenced the spatial distribution of urban gaseous pollutant concentrations included terrain elevation, building density, building volume, and floor area ratio. The greater the terrain undulation, the denser the building distribution, the greater the difference in building volume, and the greater the plot ratio, the greater the impact on the diffusion and spatial distribution of urban gaseous pollutants. (3) The spatial distribution of urban gaseous pollutant concentrations was significantly affected by the urban spatial structure indicators in the surrounding areas. Furthermore, the spatial distributions of NO2, SO2, CO, and O3 concentrations had a significant negative spatial correlation with the average DEM and standard deviation of the surrounding adjacent areas and a significant positive spatial correlation with the average and standard deviation of building height, standard deviation of building area, and building density in the surrounding adjacent areas (in June).

Catalytic formic acid dehydrogenation via hexagonal-boron nitride supported palladium

Formic acid dehydrogenation is an effective pathway for hydrogen storage, transportation, and in situ supply; however, the problems of catalyst sintering and agglomeration remain challenging. In this regard, this study aims at modulating hexagonal boron nitride-supported Pd catalyst with strong metal support interactions, thereby promoting its long-term stability. Effects of particle sizes of h-BN (500 nm, 1–2 μm, 5–10 μm) and dehydrogenation temperatures on formic acid conversion, hydrogen yield, CO concentration, and product distribution are investigated. The nano-scaled h-BN supported Pd nanoparticles show the best performance of 24.25 mmol H2 mL-1 HCOOH with a H2 concentration of 44.7 vol%. Characterizations such as N2 adsorption and desorption, XRD, TEM-EDX mapping, and XPS are used to study the physicochemical properties of the as-synthesized and reacted catalysts. Specifically, the diffraction peaks of Pd cannot be detected from XRD, possibly attributing to the homogeneous dispersion of its nanoparticles, as confirmed by the TEM-EDX mapping results. The durability tests indicate that the Pd/h-BN (500 nm) catalyst remains long-term stability under a temperature as high as 160 °C. Moreover, results from XPS reveal that there is a strong interaction between the Pd nanoparticles and the hexagonal BN support, as proved by the electronic transformation from Pd to N by XPS, thereby enhancing the stability of the Pd/h-BN catalyst.

Anomalous elastic properties of mudrocks bounding reservoirs with high concentrations of naturally occurring CO2

Very high concentrations of CO2 have been encountered in solution as carbonic acid in hydrocarbon reservoirs in parts of the Greater Sarawak Basin, offshore Borneo, Malaysia. Concentrations can exceed 80%. Anomalous features in 3D seismic data also are found in areas with high CO2 concentrations. These features appear as halos around reservoirs, cutting across stratigraphy and indicating a hardening of the nonreservoir rocks within the envelope of the halo. These halos can extend for hundreds of meters above and below a reservoir. Elastic log data from wells that pass through and adjacent to these seismic anomalies indicate that mudrocks within the anomalies have higher densities and velocities than would be predicted from locally derived compaction trends. Combinable magnetic resonance measurements indicate that the anomalous properties are the result of lower-than-expected capillary-bound microporosities. It is proposed that carbonic acid in the reservoir fluids diffuses into the bounding rocks, causing a loss of porosity. The amount of porosity lost depends on the clay content of the mudrock and the initial level of compaction, with shallower, more clay-rich shales able to lose more porosity. The anomalous seismic signatures result from a sharp transition (over approximately 5 m) at the diagenetic front between normal and altered rocks. The alteration can significantly change the amplitude variation with offset response of the reservoirs and therefore the ability to correctly predict fluid phase and reservoir quality. No anomalies are observed when the concentration of CO2 in the reservoir is less than 10% but always present when CO2 exceeds 20%. Therefore, it is possible to map the general distribution of high CO2 concentration from seismic data. There is no indication that the scale, amplitude, or shape of the anomalies gives an indication of the concentration of CO2.

Testing and Analysis on the Spatial and Temporal Distribution of Light Intensity and CO2 Concentration in Solar Greenhouse

Greenhouses, as important parts of facility agriculture, can reduce the restrictions on agricultural production imposed by the natural environment and make rational and efficient use of production resources. We conducted long-term, continuous testing of temperature, humidity, light intensity, and CO2 concentration parameters in a heliostat greenhouse in the central and western parts of the Inner Mongolia Autonomous Region, a cold and arid region of northern China. A large amount of data was processed by statistical observation, simulation analysis, and 3D reconstruction to obtain the overall distribution, variation pattern, and mathematical model of the regional greenhouse environment in time and space. The results show that the temperature, humidity, light intensity, and CO2 concentration in the greenhouse have significant daily variation patterns, that there are strong coupling relationships between light intensity–CO2 concentration–time and indoor temperature–light intensity–CO2 concentration, that the coefficients of determination (R2) of the mathematical models are 0.88 and 0.89, and that the standard errors (RMSE) are 49.67 ppm and 45.30 ppm, respectively. The environmental parameters were fitted with high accuracy in order to provide scientific data for the cultivation of heliostats in the region.

Modeling of Elevated Pressure Diffusion Flames with Water Addition

ABSTRACT This work investigates high pressure methane diffusion flames with water addition using PeleLM simulation. Particularly, this research uses a coflow burner under the pressure conditions of previous experiments with no water addition up to 11.1 bar. This work provides a comprehensive preliminary understanding of how combustion changes when water vapor is introduced into the fuel flow from 0% to 60% mole fraction. It provides a detailed temperature, CO, and CO2 concentration distribution using the PeleLM adaptive mesh refinement (AMR) code. The results show that the peak temperature in the flame reduces with water addition and increases with pressure increase. The general conclusion is that the pressure influence dominates over the water addition. This computational result helps to understand the scope of change when water is introduced into the high pressure flow and helps the next step of experiment planning.

Effects of Fire Location and Forced Air Volume on Fire Development for Single-Ended Tunnel Fire with Forced Ventilation

Single-ended tunnels are a typical structure and an important part during tunnel construction. In the case of a fire in a single-ended tunnel, forced ventilation is commonly used to create a safe area near the excavation face. This work is aimed at examining the effects of fire location and air volume on fire development for single-ended tunnel fires with forced ventilation. A single-ended tunnel was built in Fire Dynamics Simulator (FDS), and twenty simulation tests were carried out. In the simulation, the distribution of flow field, temperature, and CO concentration in the tunnel were measured and analyzed. The results show that three regions can be identified based on airflow directions and velocity: (1) turbulent flow zone, (2) turbulent flow transition zone, and (3) steady flow zone. It was found that the maximum ceiling temperature rise decreases first with the distance between the fire source and the excavation face (XL), and then increases with a further increase in XL. The simulation results also showed that CO can easily accumulate on the ventilation duct side at the fire source position and the opposite side of the ventilation duct 5.0–15.0 m downstream of the fire source. Both the CO concentration and the maximum ceiling temperature rise decrease with increasing air volume, while the larger forced air volume will result in a higher risk for the downstream regions. The present results are of practical importance in firefighting and personnel evacuation in single-ended tunnels with a forced ventilation system.