Natural Air Supply Research Articles

Integrating physical knowledge and artificial intelligence approaches for simulation and optimization of direct urea fuel cell

Direct urea fuel cell (DUFC) has recently gained attention as a potentially effective fuel cell because of urea’s ease of use, low-cost, high-energy density, and toxicity-free nature. To develop a fast and accurate mathematical tool to model and optimize the performance of DUFC, this study, for the first time, combined the kinetic model and artificial intelligence approaches. Accordingly, an artificial neural network (ANN) model was developed based on the synthetic datasets produced from the verified kinetic model and then was optimized by particle swarm optimization to determine the optimal conditions for DUFC. The peak power density output and substrate-based energy recovery were chosen as the target functions that depend on several fundamental operating and designing parameters (i.e., types of catholyte, membrane thickness, diffusion layer thickness and porosity, feeding flow rate, temperature, urea and KOH concentrations). Along with significantly reducing the computational simulation time to the kinetic model (from 1500 s to 2 s), the proposed approach exhibited superior accuracy compared to the response surface methodology. With nickel nanoparticles as the anode catalyst material and pure oxygen as the catholyte, the highest power density output and energy recovery from DUFC were predicted at 15.1 mW/cm2 and 19.6 %, respectively. On the other hand, with the natural air supply, the optimal power density and energy recovery values were only 14.4 mW/cm2 and 18.9 %, respectively, due to lower oxygen concentration. These poor performances suggest that more efficient catalyst materials for DUFC need to be further investigated and applied.

Экспериментальное исследование влияния температуры распылителя на характеристики сжигания дизельного топлива в атмосферном горелочном устройстве

In this work, using diesel fuel as an example, we studied the combustion characteristics of liquid hydrocarbons when atomized by a high-speed air jet. This approach to spraying liquid fuel in combustion processes has a number of advantages over traditional spraying: the ability to supply fuel with a low degree of purification and to reduce the likelihood of fuel equipment coking. Using an atmospheric burner device with natural air supply into the mixing chamber, the depen¬dences of the composition of intermediate and final combustion products were studied, and the flame temperature was measured at various fuel flow rates and parameters of the atomizing air jet (flow rate, temperature). A comparison was made of the obtained characteristics for equivalent modes at different temperatures of the supplied atomizer. It was found that when heated air is used as a sprayer, higher flame temperatures are ensured, which ensures a more complete fuel burnout and a decrease in CO concentration in the flue gases, but at the same time, a slight increase in NOx is observed.

Combustion of diesel fuel sprayed with cold or heated air in an atmospheric burner

In this work the combustion characteristics of liquid hydrocarbons when atomized by a high speed air jet were studied, using diesel fuel as an example. This approach to spraying liquid fuel in combustion processes has a number of advantages over traditional spraying: the ability to supply fuel with a low degree of purification, reducing the chance of coking of fuel equipment. Using an atmospheric burner device with natural air supply into the mixing chamber, the dependences of the composition of intermediate and final combustion products were studied, and the flame temperature was measured at various fuel flow rates and parameters of the atomizing air jet (flow rate, temperature). A comparison of the obtained characteristics was made for equivalent modes at different temperatures of the supplied atomizer. It was found that when heated air is used as a sprayer, higher flame temperatures are ensured, which ensures more complete fuel burnout and a decrease in CO concentration in the flue gases, but at the same time, a slight increase in NOx was observed.

Numerical analysis of a pre-chamber vortex burner with a steam blast atomizer

The combustion of diesel fuel in a pre-chamber vortex burner with a steam blast atomizer has been studied numerically. The well-proven k-w SST (URANS) model was chosen for calculations. Combustion was simulated using the Eddy Dissipation Concept (EDC) model, taking into account detailed chemical mechanisms in turbulent reacting flows. The results of testing the selected mathematical model showed good agreement of calculations with the known experimental data, a high agreement of the results was achieved: temperature, CO, NOx, O2, and CO2. The influence of steam and fuel flow rates on the flow structure and physicochemical processes in the burner and at the nozzle outlet has been studied. The structure of the flow inside the burner was shown. A high-velocity jet of steam ejects fuel, oxidizer flow and hot combustion products, forming a large zone of circulation and intense mixing. The influence of burner operating regimes on fuel underburning and environmental performance has been investigated. It was found that in the selected range an increase in the relative steam flow rate leads to almost complete combustion of fuel inside the burner. In the combustion chamber with a natural air supply, the excess air ratio was (0.96–1.23). For the considered fuel flow rate of (0.8–1.2 kg/h), the concentration of toxic emissions meets the environmental standard EN:267 – CO < 40 ppm, NOx < 50 ppm. The minimum emissions of CO = 5 ppm and NOx = 27 ppm are achieved at mass steam concentration of 44–50%.

A Technology of Multiple Smelting Furnaces per Termite Mound: Iron Production in Chongwe, Lusaka, Zambia

Abstract With exception of Maluma (1979) and Musambachime (2016, 2017), there have been no archaeometallurgical publications on the technology and culture of iron production in Zambia. This paper presents archaeological and archaeometallurgical evidence of a technology of iron production in Chongwe in terms of spatial organization, the process of metal production (either a three-stage process involving smelting in relatively tall furnaces, refining in miniature (vintengwe) furnaces, and smithing on a hearth or a two-stage process involving smelting and smithing), furnace air supply mechanisms, liquid slag handling techniques, variation in the geochemistry of ore and clay, and the nature of the final smelting products. Archaeological field data collection techniques included ethnoarchaeological interviews, (furnace) excavation, surface collections, and surface walkover surveys, while laboratory analytical techniques included optical microscopy (OM), scanning electron microscopy (SEM), and x-ray fluorescence (XRF). New field evidence indicates that iron production in Chongwe in the previous two centuries was secluded from respective pre-modern settlements for socio-cultural and technical reasons. There are no settlement remains in and around Chongwe smelting sites. Also, most of the archaeological data in Chongwe are supportive of the two-stage process that did not involve iron refining in vintengwe furnaces. There were no iron refining sites in Chongwe. Archaeological evidence also strongly points to the use of natural air supply mechanism for the smelting furnaces because proximal ends of tuyères inter alia were not trumpeted. All smelting sites were systematically located on termite mounds. There were three to four smelting furnaces located on the western side of a termite mound. The presence of tuyère mould slags and thin and elongated slag microstructures strongly indicates that liquid slag was tapped outside the furnace apparently through tuyères and was left to cool quickly. Presence of primary wüstite and iron particles in the slags strongly suggests the production of iron as the final smelting product in Chongwe. The results are compared with the archaeology, chemistry, and mineralogy of iron production from other parts of sub-Saharan Africa, particularly in the Lake Tanganyika-Nyasa Corridor. The presence of three to four smelting furnaces per termite mound makes iron production in Chongwe a unique technology in the Corridor.

The scope of inducing natural air supply via the façade

ABSTRACTAn overview is given of recent developments in the use of a system of inducing natural air supply via the façade in the Netherlands. This is followed by a review of the results of measurements from climate chamber experiments of its inducing ventilation performance and detailed insights gained from related experiments of climate chamber measurements for a school and a hospital. Finally, lessons learned from practical experience gained in a newly built office and two schools are outlined. These studies of different systems of natural air supply via the facade are used to inform a scoping review of options for use in the design of new buildings using such systems in the future. Because turbulence is an important comfort-parameter, having a positive as well as negative influence on comfort and with physical principles that are, in relation to a number of parameters, still unknown, the issue of turbulence within such systems is discussed in more detail.

Measurement of Indoor Air Quality in Chinese Charcoal Barbecue Restaurants

An assessment of Chinese charcoal barbecue restaurants was carried out to assess the impact of ventilation systems on the indoor air quality. This study focused on the temperature field, relative humidity field and concentration distribution. The indoor environments of the sampled restaurants were related to the fuel of heat sources and the mechanical exhaust system, especially the local exhaust system. For most of time, CO2 values did not exceed the acceptable level. CO is the main contaminant of this kind of charcoal barbecue restaurants. From the data available we could find restaurant C3 produced the largest amount of CO (38.5 PPM) in cooking mode because of natural air supply. While restaurant C2 generated the largest amount of CO (42.6 PPM) in idle mode due to the temporary use of exhaust hood. There was a little difference between the mean temperatures and relative humidity before and after dinner.

Performance evaluation of longitudinal and transverse ventilation for thermal and smoke control in a looped urban traffic link tunnel

The complex structure of the urban traffic link tunnel (UTLT) exacerbates fire accident risk and increases the difficulty of smoke control, especially for a UTLT with looped tunnel systems. The applicability of the traditional tunnel smoke control methods, e.g., transverse ventilation and longitudinal ventilation, needs further investigation for UTLTs. Experiments were conducted in a small-scale model to investigate the effectiveness of both two ventilation modes for a looped UTLT. In a longitudinally ventilated UTLT, the critical velocities, as the minimal air velocities for preventing smoke infiltrating into the regions upstream of the fire and entering the downstream tunnel branches that are adjacent to the smoke discharge route, should be guaranteed. Multiple operational modes of longitudinal ventilation could be feasible for achieving the desired performance of smoke control. For transverse ventilation, both the effects of the exhaust flow rate and the air supply rate are investigated. To confine the smoke in the tunnel branch where fire occurs, an effective exhaust flow rate could be twice the smoke production rate. Forced air supply could be unnecessary for a UTLT due to the abundance of natural air supply routes. Longitudinal ventilation leads to lower smoke flow temperatures than transverse ventilation does in UTLTs.

The acoustic model of oscillations of gas combustion in coaxial pipes

Organization of pulse combustion mode is one of the possible solutions to the problem of energy efficiency installations using hydrocarbon fuel. For grate combustion of solid fuels, in particular, solid industrial wastes are considered to be promising coaxial system, allowing the admission of secondary air to the combustion zone. In this paper we proposed an acoustic model of oscillations of gas when burning solid fuel in the system is coaxially arranged pipes with natural air supply. The description of the motion of the gas in the system during one period of oscillation.

Portable Rice Hull Stove: An Innovation

This research is an innovation of the portable rice hull stove equipment to save time, investment, manpower and the environment. A desired distance of 5 cm bottom height of the inside burner from ash retainer is obtained as the critical point in achieving the best combustion process. The unique characteristic of this innovative design is the perforated inside and outside burners and the detachable inside burner for easy replacement and durability of this stove. Specifically, this rice hull stove consists of eleven major parts to wit: 1) inside burner & holder; 2) hopper; 3) flame controller; 4) combustion chamber; 5) outer burner; 6) tensioner (optional); 7) pot (base) rest; 8) retainer of rice hull fuel; 9) perforated holes (natural air supply); 10) leverage (optional) for ash/ aeration and disposal in the ash/char chamber); and 11) tripod stand. For easy removal of the ash and char in the stove at the ash chamber, a flat floppy type ash remover was keenly studied and observed through hand and or foot tapping of the leverage for every 2- to 5-minute combustion. The workability of the equipment was tested through an actual cooking utilizing the different input cooking materials like clean rice, fish, etc., and different weights of rice hull fuel. The rice hull stove has the following thermal efficiencies: for clean rice, it is 9.76%; for drinking water, it is 23.06%; for vegetable, it is 11.33%; for fried fish, it is 11.33%, and for fried chicken, it is 15.40%.

Ventilation Measurement and Simulation Optimization for Aerobic Composting Workshop of a Large Sludge Treatment Engineering

Based on measured ventilation condition in the built aerobic composting plant of large sludge treatment engineering,using the methord of CFD, four kinds of scheme for the new aerobic composting plant were analysed,which contain two types of ventilation(natural air supply mechanical exhaust and mechanical air mechanical ventilation)and two kinds of supply air rates (4x105m3/h and 8x105m3/h). Studies have shown that the methord of mechanical air supply and exhaust is better than the original natural air mechanical exhaust in this plant; The methord of mechanical air supply and exhaust is recommended to reduce ammonia content for personal breathing zone and ventilation energy consumption.

Measurement of temperature, relative humidity, concentration distribution and flow field in four typical Chinese commercial kitchens

An assessment of a current situation of Chinese commercial kitchen was carried out to assess the impact of the typical ventilation systems of four commercial kitchens on their indoor thermal environment in China. To understand the effect of the ventilation system, this study only focused on velocity field, temperature field, relative humidity field, and concentration distribution varying with following whether cooking or not. From the data available we could find for the kitchens that use the mechanical air supply system, the temperature and CO2 concentration of the non-cooking area exceeded the value of the measurement points that besides the cooking range. For the middle and small scales commercial kitchens, that use the natural air supply system, the temperature and CO2 concentration was far more than the acceptable level. In addition, the variation of relative humidity was contrary to the trend of temperature variation, which is different to the previous study result. The measurement results indicated the ventilation system in typical Chinese commercial kitchens couldn't remove the waste heat and impurities effectively. The reason is diversiform.

공동주택의 하이브리드 환기시스템 성능평가 연구

본 연구는 공동주택에서 하이브리드 환기시스템의 적용성을 검토하고, 하이브리드 환기시스템의 성능을 향상하기 위해 CFD시뮬레이션을 이용하여 설계방안을 제시하고자 하였다. 연구대상으로는 전용 <TEX>$51m^2$</TEX>, <TEX>$84m^2$</TEX>의 공동주택을 선정하였으며, 하이브리드 환기시스템은 창틀자연급기와 각실을 덕트로 연결하여 배기하는 시스템(Hybrid 1)과 창틀자연급기와 욕실 거실배기가 혼합된 시스템(Hybrid 2)을 적용하였다. 이때 각 시스템별 배기구의 위치를 변수로 하여 CFD를 수행하였다. <TEX>$51m^2$</TEX>, <TEX>$84m^2$</TEX> 모두 Hybrid 2가 Hybrid 1보다 환기효율이 우수한 것으로 나타났으며, 평균공기연령 또한 낮은 것으로 나타났다. Hybrid 1의 경우, 덕트 배기구의 위치가 각 실 입구에 설치하는 것보다 실 안쪽 모서리에 설치하여 기류이동을 많이 유발할 수 있는 유형이 효과적인 것으로 나타났다. Hybrid 2의 경우, 욕실 고정압팬에 덕트를 연결하여 거실중심에 배기구를 설치하는 시스템이 환기효율이 가장 우수한 것으로 나타났다. 그러나 <TEX>$51m^2$</TEX>의 경우 Hybrid 2가 Hybrid 1보다 20%의 향상된 환기효율을 나타낸 반면, <TEX>$84m^2$</TEX>의 경우는 14%의 향상된 환기효율을 나타내 공동주택 규모에 따른 적정한 하이브리드 환기시스템에 대한 검토가 필요하다. The purpose of this study was to evaluate the applicability of hybrid ventilation system in apartment housings and present a design method to improve the performance of hybrid ventilation system using the CFD simulation. As the object of CFD simulation, a small apartment houses with area of <TEX>$51m^2$</TEX> and <TEX>$81m^2$</TEX> were selected and evaluated. The test hybrid ventilation system are window frame natural air supply & duct exhaust hybrid system(Hybrid 1) and window frame natural air supply & bathroom and livingroom exhaust hybrid ventilation system(Hybrid 2). To evaluate the ventilation efficiency, we used the locations of diffuser installed for each system as the variables through the CFD simulation. In the case of Hybrid 1, the ventilation efficiency of the exhaust duct diffuser located on the inside room was higher rather than the exhaust duct diffuser located on the entrance. In the case of Hybrid 2, the most efficient system was the system that the diffuser connecting the bathroom static pressure fan is installed on the center of the living room. The ventilation efficiency of the Hybrid 2 in the case of <TEX>$51m^2$</TEX> type was more than 20% of the Hybrid 1. But, The ventilation efficiency of the Hybrid 2 in the case of <TEX>$84m^2$</TEX> type was more than 14% of the Hybrid 1. Therefore, to apply the Hybrid ventilation, a study that considers various variable should be conducted.

Characteristics of Polychlorinated Dibenzo-p-dioxins/Dibenzofuran from Joss Paper Burned in Taiwanese Temples

Two types of furnaces (a mid-size furnace denoted as Furnace 1 and a small-size one denoted as Furnace 2) commonly used for burning joss paper, located in two temples in southern Taiwan, were selected for this study. With similar burning devices (semi-open systems), both furnaces can be used to burn joss paper with the aid of natural air supply through the inlets of furnace. In order to characterize peak emission of PCDD/Fs (usually on festival days) in the selected temples, the sampling campaigns were conducted during the festival period in September 2008. It was found that the mean total I-TEQ contents in the original (unburned) joss paper from Furnaces 1 and 2 were 1.41 and 4.51 ng I-TEQ/kg, respectively. The mean total I-TEQ content in the residue of burned joss paper from Furnace 1 (7.97 ng I-TEQ/kg) was approximately 15-fold that of Furnace 2 (0.490 ng I-TEQ/kg). OCDD was the most abundant congener in the joss paper and in the residues from burned joss paper. Moreover, the emission factor of total PCDD/Fs I-TEQ content of Furnace 1 (0.176 ng I-TEQ/g-feedstock) was one to two orders of magnitude higher than that of Furnace 2 (0.0203 I-TEQ/g-feedstock). This phenomenon is probably associated with the high chlorine content in the unburned joss paper of Furnace 1, and high exhaust temperature from burning joss paper in Furnace 1 (271℃) was possibly within a range that might highly promote de novo formation of PCDD/Fs. It is necessary for the investigated furnaces to install air pollution control devices in order to reduce the PCDD/F emission from joss paper burning.

Increasing coke output per furnace

Reducing the time for batch removal from the coal-charging machine increases the height of the available furnace space and permits enlargement of the one-time charge in coke furnaces. With natural air supply to the arch region and wetting of the bunker surface with solar oil, the time for batch removal is reduced by 19 and 20.9%, respectively and the height of the available space is increased. The effect is greatest in charging with forced air supply.