Optimization of the ventilation scheme for increasing production capacity of underground mines

Currently, many underground mines are revising their design solutions to increase their production capacity. This tendency is explained by the decreasing ore grades, as well as by the extensive introduction of mechanization in underground mining operations that has improved the output of mobile equipment by increasing the box capacity and engine power. Dieselpowered mobile vehicles are the most common in underground mining practice. The advantages of such engines are obvious as they generate more power than other types of engines. However, the high air demand for mine ventilation limits their application. This is associated with the need to increase the cross-sections of permanent mine workings in order to comply with the standard air flow rate with account of the increased ventilation capacity along with an increase in the inventory of mobile equipment in order to ensure the specified output of the mine. The specific features of mining operations are defined by the stage-wise character of commissioning various blocks of the deposit. Managing of production and development works provides an opportunity to ventilate the mine sections due to their consecutive commissioning, locally, with an isolated stream of air by means of mine workings that do not have the intersection of air streams. This provides a reduction of critical path of air travel up to 30% and reduction of the general mine ventilating pressure drop by at least 20% at constant air flow rate. The results of the work can be used in designing the ventilation system of underground mines both under construction and in operation.

Effect of an Electric Field on an Optical Breakdown in the Air Stream

Experimental data on the effect of an electric field on the plasma of an optical discharge in an air flow have been obtained. Two configurations of an external electric field under the action of an optical discharge on the plasma are considered. To create an electric field, flat (the field along the beam and across the flow) and ring electrodes (the field across the laser beam and along the flow) were used. It was found that there are two modes of combined discharge (optical and electrical). When the field was created symmetrically with respect to the flow axis, an electrical breakdown was observed from the nozzle exit (positively charged electrode) to the focusing point of the laser beam, while no streamers were observed in the optical discharge wake. In another case, an electric discharge is realized between flat electrodes simultaneously with optical breakdown. In a field of constant strength above 3 kV/cm, the presence of an optical discharge plasma promoted electrical breakdown of the medium. In this case, the parameters of the electrical breakdown depended on the shape of the electrodes, the polarity of the applied voltage, and the air flow rate.

Numerical and Experimental Investigation of a Non-Premixed Double Swirl Combustor

This paper focuses on a detailed numerical investigation combined with experimental research for a non-premixed swirl combustor, which aims to analyze the effects of the blade angle of the outer swirler and equivalence ratio on flow and combustion characteristics. In the experiment, the temperature in the furnace was obtained with a thermocouple, while a realizable k-ε turbulence model and two-step reaction mechanism of methane and air are used in the numerical method. The calculation results are in good agreement with the experimental data. The results reveal that the air flow rate through the swirler accounts for a small amount of the total air due to the influence of the draft fan, and there is no central recirculation zone (CRZ) despite the presence of the swirler. It was also found that NO emissions gradually decrease as the blade angle of the outer swirler increases. It was also indicated that the average temperature is 100 K higher than the general combustor with a 58° blade angle in the furnace by increasing the equivalent ratio of the tertiary air area, and the NO emissions reduced by approximately 25%. This study can provide guidance for the operation and structural design of non-premixed swirl combustors.

Evaluation of Drying Air Conditions for Antiozonant Wax Drying Process in the Spray Drying Tower

The drying technique of Antiozonant Wax (AOW) using drying air in the spray drying tower has a considerable effect on the produced AOW powder. In this study, the drying air flow rate was measured in such a way that AOW can transform into a powder with a size of 800 mesh. The diameter and height of the spray drying tower are 1 and 6 m, respectively. Meanwhile, the AOW flow rate to the spray drying tower varies from 100 kg/hour to 500 kg/hour. The intake AOW temperature was 70 °C and at the outlet was 40 °C, while the drying air temperatures in and out of the spray drying tower were 30 and 55 °C, respectively. From the calculation results, the flow rate of the drying air is directly proportional to the flow rate of the AOW into the spray drying tower but inversely proportional to the speed of the AOW powder down the spray drying tower. In the meantime, the drying period for AOW to become a powder is between 1.033 – 1.279 s, not significantly different. It gives insight into the need to dry air in the spray drying tower configuration so that the findings will conform to the predetermined requirements.

Pengaruh Kecepatan Fluida Pendingin (Udara) Terhadap Unjuk Kerja Dan Karakteristik Perpindahan Panas Pada Radiator Sepeda Motor Yamaha Nmax 155CC

Penelitian ini menggunakan metode ɛ-NTU untuk menganalisis data. Radiator yang digunakan adalah radiator sepeda motor Yamaha Nmax 155cc dengan jenis aliran vertical, flat tube dan louvered fins, kipas/fan sebagai sumber angin simulasi, dengan campuran 50% air + 50% coolant radiator. Laju aliran air konstan 4 lpm dan temperatur fluida panas konstan 80. Variasi kecepatan aliran udara yang digunakan pada pengujian kali ini adalah 4-8 m/s dan diatur menggunakan Dimmer sebagai alat bantu. Dari pengujian yang telah dilakukan didapat laju massa aliran udara yang paling besar terjadi pada kecepatan kipas 8 m/s. Laju perpindahan panas yang paling besar terjadi dikecepatan kipas 8 m/s sebesar 0,0735 kW dan panas menyeluruh terbesar juga terjadi dikecepatan kipas 8 m/s yaitu sebesar 9,50 W/m2°C. Efisiensi radiator maksimum terjadi pada kecepatan kipas 5 m/s dengan nilai sebesar 7,59. Kata kunci: Efektifitas, Metode ε-NTU, Radiator Nmax 155cc. This study uses the ε-NTU method to analyze the data. The radiator used is a 155cc Yamaha Nmax motorcycle radiator with vertical flow type, flat tube and louvered fins, fan/fan as a simulation source, with a mixture of 50% water + 50% coolant radiator. The water flow rate is constant 4 lpm and the hot fluid temperature is constant 80℃. The variation of air flow velocity used in this test is 4-8 m/s and is adjusted using a dimmer as a tool. From the tests that have been carried out, the largest air flow rate occurs at a fan speed of 8 m/s. The highest heat transfer rate occurs at a fan speed of 8 m/s at 0.0735 kW and the largest overall heat also occurs at a fan speed of 8 m/s at 9.50 W/m2°C. The maximum radiator efficiency occurs at a fan speed of 5 m/s with a value of 7.59 Keywords: Effectivenes, ɛ-NTU Method, Nmax 155cc Radiator

Research Active Posterior Rhinomanometry Tomography Method for Nasal Breathing Determining Violations

This study analyzes the existing methods for studying nasal breathing. The aspects of verifying the results of rhinomanometric diagnostics according to the data of spiral computed tomography are considered, and the methodological features of dynamic posterior active rhinomanometry and the main indicators of respiration are also analyzed. The possibilities of testing respiratory olfactory disorders are considered, the analysis of errors in rhinomanometric measurements is carried out. In the conclusions, practical recommendations are given that have been developed for the design and operation of tools for functional diagnostics of nasal breathing disorders. It is advisable, according to the data of dynamic rhinomanometry, to assess the functioning of the nasal valve by the shape of the air flow rate signals during forced breathing and the structures of the soft palate by the residual nasopharyngeal pressure drop. It is imperative to take into account not only the maximum coefficient of aerodynamic nose drag, but also the values of the pressure drop and air flow rate in the area of transition to the turbulent quadratic flow regime. From the point of view of the physiology of the nasal response, it is necessary to look at the dynamic change to the current mode, given the hour of the forced response, so that it will ensure the maximum possible acidity in the legend. When planning functional rhinosurgical operations, it is necessary to apply the calculation method using computed tomography, which makes it possible to predict the functional result of surgery.

Habitat Cooling by a Canadian Well in Ouagadougou (Burkina Faso): Numerical Approach

In the Sahelian zone, air cooling in house by air-soil heat exchanger is an alternative in the context of insufficient of electrical energy. This work is about cooling of a habitat in Ouagadougou by numerical approach. Numerical results provided a better understanding of the influence of parameters such as tube length, air velocity and soil temperature on the thermal efficiency of this system. We analyze the effects of parameters such as renewal air flow rate, soil temperature and number of tubes. The results show that during the hot periods of the day, the Canadian well cool air in habitat.

Waterborne and Airborne Microfibers Shed from Non-Woven Materials in Water and Air Environments

Nonwoven products are widely used in various fields, including many disposable products, such as wipes, diapers, and masks. However, microfibers shed from these products in the aquatic and air environment have not been fully described. In the present study, several commercial single-use nonwoven products and a series of meltblown nonwoven materials produced in a pilot plant were investigated regarding their microfiber generation during their use in aquatic and air environments. Microfibers shed in water were studied using a Launder Ometer equipment (1- 65 mg of microfibers per gram material), and microfibers shed in air were evaluated using a dusting testing machine that shakes a piece of the nonwoven back and forth (~0 to 6000 microfibers (4 mg of microfibers) per gram material). The raw materials and bonding technologies applied to the commercial nonwovens affected the microfiber generation both in water and air conditions. Meltblown nonwoven fabrics generated fewer microfibers compared to the other commercial nonwovens studied here, and the manufacturing factors, such as DCD (Die to collector distance) and air flow rate, affected the tendency of microfiber generation. Microfibers of nonwovens shed in water and air environment were compared to selected textile materials and paper tissue materials. The results herein suggest that it is possible to control the tendency of microfiber shedding through the choice of operating parameters during nonwoven manufacturing processes.

Features Importance Analysis of Diesel Vehicles’ NOx and CO2 Emission Predictions in Real Road Driving Based on Gradient Boosting Regression Model

In order to have an accurate and fast prediction of the artificial intelligence (AI) model, the choice of input features is at least as important as the choice of model. The effect of input features selection on the emission models of light diesel vehicles driven on real roads was investigated in this paper. The gradient boosting regression (GBR) model was used to train and to predict the emissions of nitrogen oxide (NOx), carbon dioxide (CO2), and the fuel consumption of real driving diesel vehicles in urban scenarios, the suburbs, and on highways. A portable emissions measurement system (PEMS) system was used to collect data of vehicles as well as environmental conditions. The vehicle was run on two routes. The model was trained with the first route data and was used to predict the emissions of the second route. There were ten features related to the NOx model and nine features associated with the CO2 model. The importance of each feature was sorted, and a different number of features were used as input to train the models. The best NOx model had the coefficient of determination (R2) values of 0.99, 0.99, and 0.99 in each driving pattern (urban, suburbs, and highways). Predictions of the second route had the R2 values of 0.88, 0.89, and 0.96 respectively. The best CO2 model had the R2 values of 0.98, 0.99, and 0.99 in each driving pattern, respectively. Predictions of the second route had the R2 values are 0.79, 0.82, and 0.83, respectively. The most important features for the NOx model are mass air flow rate (g/s), exhaust flow rate (m3/min), and CO2 (ppm), while the important features for the CO2 model are exhaust flow rate (m3/min) and mass air flow rate (g/s). It is noted that the regression models based on the top three features may give predictions very close to the measured data.

Occurrence of Biting Midges (Diptera: Culicoides) on Dairy Farms in Eastern Slovakia in Relation to Abiotic Factors

Within the scope of our research, we have performed 59 trapping sessions and collected 15,756 biting midges from 20 species at four farms (Kluknava, Ostrov, Turňa nad Bodovou and Zemplínska Teplica), The most frequent types of captured insects were representatives of the Avaritia subgenus, C. obsoletus/C. scoticus, representing on average 85.1 % (13,295 individuals) of the fauna of the biting midges, with the exception of the farm in Ostrov where this group represented only 41.7 % of the fauna. At this particular farm, the most frequently trapped insects belonged to the Culicoides subgenus (54.1 %), in particular the C. bysta, C. lupicaris, C. newsteadi, C. Pulicaris and C. Punctatus species. During the trapping sessions, we monitored factors affecting the number of trapped biting midges, such as the temperature, relative air humidity and airflow rate: the air temperature during the trapping of the biting midges ranged from 9.8 to 26.2 °C; the relative air humidity ranged from 35.1 to 100 %; and the air flow rate ranged from no wind to a wind velocity of 8.2 m.s-1. However, in the final evaluation, we failed to observe a statistically significant correlation between the air flow and the number of trapped biting midges. The largest amounts of biting midges were trapped at temperatures ranging from 15.8 to 24.6 °C and at a relative air humidity ranging from 54.2 % to 68.6 %. While monitoring the seasonal dynamics of the physiological conditions of biting midge females at the selected farms, we confirmed that during the period from June to August, the most frequently trapped females were parous (50.1 %; 7,826 individuals). In addition, nulliparous females comprised 43.8 % (6,842 individuals) and were continuously trapped throughout the season (April— November).