Amount Of Airflow Research Articles

Numerical simulation to evaluate gas diffusion of turbulent flow in mine ventilation system

Tracer gas technique is a method to analyze the airflow path, measure the airflow quantity, and detect any recirculation or leakages in underground mine. In addition, it is also possible to evaluate the axial gas diffusion of gas in turbulent bulk flow by utilizing the tracer gas data. This paper discussed about the measurement using tracer gas technique in Cibaliung Underground Mine, Indonesia and the evaluation of effective axial diffusion coefficient, E, by numerical simulation. In addition, a scheme to treat network flow in mine ventilation system was also proposed. The effective axial diffusion coefficient for each airway was evaluated based on Taylor’s theoretical equation. It is found that the evaluated diffusion coefficient agrees well with Taylor’s equation by considering that the wall friction factor, f, is higher than those for smooth pipe flow. It also shows that the value of effective diffusion coefficient can be inherently determined and the value is constant when matching with other measurements. Furthermore, there are possibilities to utilize the tracer gas measurement data to evaluate the airway friction factors.

Method to assess quality and quantity of outdoor ventilation airflow received by occupants

Ventilation with outdoor air is one important way to improve indoor air quality and keep occupants healthy and comfortable. Assessment of ventilation performance and effective outdoor ventilation airflow received by occupants at their workspace or respiration zone is necessary. A new scale, the first factor of outdoor air effect (FFOAE), was developed for this purpose and is based on the relationship between local components composition and the combined effect of outdoor air stream and contamination sources. The transfer efficiency of the outdoor air component,the time efficiency of indoor airflow, and the transfer efficiency of the contaminant component were reflected simultaneously in the first factor of outdoor air effect. With the aid of the FFOAE, impacts of indoor airflow pattern, supplied outdoor airflow rate, contamination sources emission intensities, and their distribution on ventilation performance, quality, and quantity of outdoor ventilation airflow received by occupants are discussed by numerical simulations.

PERFORMANCE ANALYSIS OF COUNTER FLOW WET COOLING TOWER

This paper presents an experimental work, which studies the performance of a counter-flow type cooling tower. The experimental trials have been carried out in a counter-flow type cooling tower test rig with mechanical draft. Expanded Wire Mesh type of film packing has been used for experimentation. The packing is made of mild steel with height ranging from 800 to 1255 mm. This study investigates the effect of the air and water flow on the cooling tower range, as well as the tower characteristics for different air flow and water flow quantities. The variation of temperature along the height of pack is measured by means of suitable thermocouples at five different places. The results show that the mass flow rate has adverse effect on the number of transfer unit. Also tower range would be increased by decreasing the inlet wet bulb air temperature.

Reliability estimation of auxiliary ventilation systems in long tunnels during construction

Ventilation system should blow large quantity of airflow particularly in case of toxic or explosive gasses emission from the wall rocks and face, especially in long tunnels. In these cases, multiple jet fans are usually required, so that they could be grouped together as serial, parallel or combined arrangements through ventilation system or equally spaced along the tunnel. There is a serious requirement to have some reserved jet fans along with the main once, so that the operation of the ventilation system could be reliable. Operation of a ventilation system is usually evaluated by experiences and engineering judgments which follow empirical methods. The aim of this paper is to introduce an approach to evaluate reliability of ventilation system in the long tunnels. The method is based upon using the failure rate time to determine the probability of the failure of an active jet fan and also the repair rate time to determine the probability of repairing the out of work ones .In this approach, the active and standby jet fans are modelled as a stochastic process. Therefore, the probability of replacing each failed jet fan with a standby jet fan is estimated using Markov Chains theory .From this point of view a more realistic decision-making for the number of standby jet fans and also reducing the risk as well as uncertainties can be based upon the analysis of such a results.

Mine ventilation measurements with tracer gas method and evaluations of turbulent diffusion coefficient

Tracer gas measurements have been carried out at the Pongkor underground gold mine, Indonesia, to evaluate mine ventilation flows and to investigate the effective turbulent diffusion coefficients in mine airways. The airflow routes and quantity, and the diffusion coefficient have been obtained by matching the measurements with numerical simulations using the advection-diffusion equation. Two leakages with flow quantity of 26.7 and 36.7 m3/s were detected. Reduction of leakages have been measured with the method after stopping the leakage routes. The turbulent diffusion coefficients for the simple airways have good agreement with the Taylor equation. However, for complex airways in operating mines, the coefficients show higher values (1.5 to 32 times) than that obtained by the Taylor equation and these have been compared with the data measured in the Kushiro coal mine, Japan. It is mainly affected by the ratio of airway length over equivalent diameter and airway frictions, but airflow mixing along the airway also has an effect on the diffusion coefficient.

Airborne Dust Capture and Induced Airflow of Various Spray Nozzle Designs

Water spray characteristics, including droplet size and velocity, airborne dust capture potential, and induced airflow quantity for various spray nozzle designs were evaluated to provide basic information for improving spray applications. Water droplet size and velocity characteristics were initially measured by a Phase Doppler Particle Analyzer (PDPA) for hollow cone, full cone, flat fan, and air atomized spray nozzles at similar operating parameters. Airflow inducement and dust capture experiments were also conducted under the same operating parameters to examine any salient features of the spray nozzle type, droplet characteristics, induced airflow, and airborne dust capture. Test results indicate that there are trade offs between airflow inducement and dust capture efficiency. A spray nozzle with a wider discharge angle was observed to induce more airflow, but at reduced dust capture efficiencies. Increasing spray nozzle fluid pressure(s) generally reduced water droplet sizes with concurrent increases...

A Study on Expanding the Application Range of the Method for Predicting the Flow Capacity of the Special Drainage Fitting Systems : Part 1-Behavior of the Air Flow Quantity and the Air Pressure by Change of the Piping Layout

A Study on Expanding the Application Range of the Method for Predicting the Flow Capacity of the Special Drainage Fitting Systems : Part 1-Behavior of the Air Flow Quantity and the Air Pressure by Change of the Piping Layout

Morphologie und rhinologische Bedeutung der Intumescentia septi nasi anterior*

The intumescentia septi nasi anterior is a protuberance on each side of the anterior part of the nasal septum containing "cavernous" tissue. None of the previous studies devoted to the general aspects of endonasal "cavernous" tissue refer to the incidence and rhinological function of the intumescentia. This investigation revealed an incidence of more than 80% in 170 individuals without any rhinological symptoms. The external morphology observed in 7 cadavers indicated a close topographical correlation of the position of the middle turbinate, the depth of the lateral nasal wall and the extension of the intumescentia. Histological examination showed a glandular mass interspersed with a dense vascular network similar to the "cavernous" tissue found within the lateral turbinates. Various filling conditions of the intumescentia have no significant influence on rhinomanometrical parameters and the quantity of nasal airflow. However, visualization of the endonasal flow within a nasal model containing the septal protuberance indicated that the intumescentia considerably alters the quality and local velocities of the endonasal airstream. Considering the results of the study, the intumescentia must be regarded as a completely normal formation of particular rhinophysiological importance, which, up until now, has not been mentioned in rhinosurgery.

Airflow and Temperature Patterns Through Large Round Bales

A hay dryer with capacity for 84 soft-centre bales was tested to determine airflow patterns. Capping bales was critical for improving airflow distribution as shown by mapping of isobars. Moisture removal rates have been measured as high as 295 kg (650 lbs) per hour. The variation in quantity of airflow, and hence moisture removal from bale to bale should be minimized by proper sizing of laterals.

Studies on Combustion, Vibration, and Noise in High-Speed Diesel Engines Through Newly Developed Measuring Instruments

The authors have been conducting studies on the reduction of exhaust emissions using a high-speed diesel engine. By applying composite countermeasures consisting of five items: (1) timing retard, (2) optimization of fuel injection system, (3) water-in-oil type emulsified fuel, (4) application of ignition improver, and (5) an increase in airflow quantity, an exhaust NOx level less than half of the original was attained while retaining the original low levels of fuel consumption, smoke density, and engine noise. The authors developed new measuring instruments in order to grasp the true nature of combustion, especially to clarify the delicate change in combustion. By using these instruments, the combustion phenomena were analyzed accurately, speedily, and synthetically on various aspects such as combustion mode, vibration, noise, thermal loading, heat balance, etc. The complicated combustion behavior in the cylinder has been clarified in part by simultaneous measurement of cylinder pressure at several points.

Studies on combustion and exhaust emissions in a high speed diesel engine. (1st report. Reduction in exhaust NOx).

The authors have been conducting studies on the reduction of exhaust emissions using a high speed diesel engine with a bore of 110 mm and a maximum speed of 2 500 rpm. By applying composite countermeasures consisting of five items ; 1) timing retard, 2) optimization of fuel injection system, 3) water-in-oil type emulsified duel, 4) application of ignition improver and 5) an increase in air flow quantity, an exhaust NOx level about a half of the original was attained while retaining the original low levels of fuel consumption, smoke density and engine noise. Especially, in combustion tests on water-in-oil type emulsified fuel, it is clearly demonstrated that not only exhaust NOx but also smoke density are significantly reduced due to an increase in the excess air ratio of the fuel spray.

Health hazards of diesel and electric vehicles in an underground coal mine

Results of an engineering assessment of potential health hazards, both air quality and noise, are reported for diesel and electric face-haulage equipment operating in the same underground coal mine. The effects of four parameters were investigated: (1) type of car, (2) number of cars, (3) sample location, and (4) airflow quantity. Instruments were chosen for integrated gas sampling (long-term detector tubes) that were reliable, reasonably priced, and suitable for routine use in the underground environment. Particulates and noise were measured instantaneously with direct-reading instruments. In the section using diesel ram cars, none of the shift-long measurements of carbon monoxide, carbon dioxide, particulates, or noise violated threshold limit values (TLVs). About 2% of the measurements of nitrogen dioxide and nitric oxide exceeded TLVs. Particulates were excessive only in the section using electric shuttle cars. When three rather than two diesel cars were used, emissions increased approximately proportionately. Of three locations sampled, in all instances, the discharge point consistently registered higher than the face and on board the cars, but there was only a poor correlation between diesel-emission concentrations and airflow quantity. Evidence was lacking of a significant health hazard due to diesels at the mine under study.

An Improved Method for Accurate Prediction of Mass Flows Through Combustor Liner Holes

A theory is devised for predicting the coefficients of discharge for some types of combustor liner holes and for calculating the local quantity of airflow into the liner. The resulting equations are tested against reliable empirical data and they show an agreement of better than 99 percent. The new correlation is particularly amenable to the preliminary design and development of combustors and could usefully be incorporated into numerical modeling techniques. The theory is also used to devise a simple but very accurate method of correlating experimental data that has advantages over many of the methods in current use.

ラムジェットエンジンの研究 ＩＩＩ エンジン要素としての空気取入口の作動特性

A computer program which is capable of computing performance of a fixed geometry two dimensional extemal compression supersonic inlet installed in a ramjet engine which satisfies the required air mass flow rate for the engine to operate at off design condition, was developed. The program can calculate quantity of possible air flow which may income through the inlet under the critical operation that is state of operation such as normal shock wave stands on the throat position of the air inlet, and required air flow for the engine which the ramjet engine requires to generate combustion gas that is exhausted through a jet nozzle of the engine under given engine operating condition and critical air inlet operation. When possible air flow exceeds required one, possible air flow decreases down to required one by subcritical operation. When possible air flow is less than required one, a pressure recovery factor of the air inlet is lower down till required air flow decreases down and equal to possible one by supercritical operation. It was found that influence of the inlet/nozzle characteristics on the position, i.e. the strength, of the normal shock wave is very sensitive. In particular, in supercritical regime where a ramjet engine is considered to stably operate, the pressure losses due to the normal shock wave becomes predominant compared to all the other losses, such as due to the oblique shock waves, combustor and nozzle. Thus, the characteristics significantly affect the global engine performance. Useful correlation for predicting the pressure recovery in super critical regime was also found from the numerical results, which is an exponential function of the flight and design Mach numbers and gas propenies. The correlation gave a good agreement with the available experimental data of an actual ramjet engine.

高速舶用ディーゼル機関における低質油の燃焼と燃料噴射について

To find a basic principle of residual fuel combustion, tests were conducted on heavy fuels of 34.4 cSt and 75.9 cSt at 50°C (200 and 500 sec RW No. 1 at 100°F) using small-sized, high speed diesel engines with a cylinder bore of 110 mm, a stroke of 125 mm and speeds of 2500 and 2600 rpm. Using a natural-aspirated engine, the effects of individual factors on engine performance were confirmed by changing the fuel injection mode, the cooling water temperature, the suction air flow quantity and the temperature respectively. Then using a turbocharged engine, the optimum combustion method was established by chiefly improving the fuel injection mode. Fuel combustion was evaluated by means of accurate indicator diagrams obtained by the CB-366 combustion analyzer. The reliability and durability of the engines were confirmed through thermal load analysis based on temperature measurements of the combustion chamber walls.

Surge-Induced Structural Loads in Gas Turbines

The axial flow compression system of a modern gas turbine engine normally delivers a large quantity of airflow at relatively high velocity. The sudden stoppage (and reversal) of this flow when an engine surges can result in structural loads in excess of steady state levels. These loads can be quite complex due to inherent asymmetry in the surge event. The increasing requirements for lighter weight engine structures, coupled with the higher pressure ratio cycles required for minimizing fuel consumption, make the accurate prediction of these loads an important part of the engine design process. This paper is aimed toward explaining the fluid mechanics of the surge phenomenon and its impact on engine structures. It offers relatively simple models for estimating surge-induced loads on various engine components. The basis for these models is an empirical correlation of surge-induced inlet overpressure based on engine pressure ratio and bypass ratio. An approximate estimate of the post-surge axial pressure distribution can be derived from this correlation by assuming that surge initiation occurs in the rear of the compression system.

Pneumatic Sinusoidal Loading System

Current systems for the application of cyclic loads to soil specimens are reviewed, and a low-cost system which provides a sinusoidal load trace using normal shop compressed air is described. Loading systems employed for cyclic shear testing of soil commonly employ one of two principles. In one type, a double acting piston is coupled to the specimen and the pressure or load is varied by selection through a directional solenoid vave. In those employing the electrohydraulic closed loop, a double acting hydraulic piston is coupled to the specimen. The pneumatic sinusoidal loader developed from commercially available components has 3 elements: a mechanical sine wave signal generator, a volume booster relay, and double-acting piston. The since wave generator consists of an adjustable eccentric, driven by a variable speed motor, connected to a plunger-operated regulator through a crank arm. The volume booster relays and boosts the quantity of air flow required to keep the output pressure matching the signal pressure from the plunger regulator. The main features are outlined of the new piston which has been designed for low inertial mass and low friction. An advantage of this system is the ease of operation. A graph is presented which illustrates the actual recording of a triaxial liquefaction test performed with the system.

Induction Ramming a Motored High-Speed Four-Stroke Reciprocating Engine—Influence of Inlet Port Pressure Waves on Volumetric Efficiency

This paper describes calculation methods and the results obtained from a computer programme written for studying induction ramming in high-speed reciprocating engines. The calculation uses the method of characteristics for analysing the pressure fluctuations in the intake pipe. The calculated airflow figures are compared with results obtained experimentally from a motored air-cooled four-stroke motorcycle engine. Comparison shows a good correspondence between theoretical and experimental results of both the quantity of air flow and the engine speeds at which airflow peaks and troughs occur. The results also clearly illustrate how flow through the valve is affected by pressure variations at the inlet port.

炭鉱における生産, 保安の中央監視制御システムの開発

Mitsubishi Minami Oyubari Colliery which is located in southern part of Ishikari coal field in Hokkaido started its development since October 1966, and achieved the initially aimed production of 900, 000 tops coking coal annually.In this area, there are many difficuties connected with complicated geological structures, great quantity of reserved methane gas and tendency of spontaneous combustion etc.In development we tried to effect to build a modern colliery, which produces coal with high efficiency and stability. Then we have developed “Centralized Supervisory and Control System” over the whole field of productive installations and the safety. Main parts of the system are installed in the control room of the mine office, while sensors and actuaters are distributed all over the underground as well as the surface.Main function of the room attended usually by two persons are as follows:(1) centralized supervision and control of main facilities…… the gas turbine power station, power substations, compressors, main fans, exhaust blowers, belt conveyers, coal preparation plant and so on(2) automatic measurement and centralized supervision of the safety…… the concentration of methane and carbon monoxide, temperature, quantity of air flow, short circuit of air flow by opening door, local fans, sprinkling pressure, fire alarm, etc(3) gathering and communicating various kind of information quickly and precisely by the inductive wireless systemThis system was almost completed in September 1970, and now the total number of items concerned amounts to 878, that is for control 185, for supervision 568, for measurement 125. This system has till now much contributed to rationalization and mine safety in the colliery. In the near future the production of this colliery will be creased to 1, 300, 000 tons annually.

A computer technique for predicting smoke movement in tall buildings

An approach to the analysis of stack effect has been developed which allows the prediction of internal air flow quantities and associated pressure differentials for specific buildings prior to construction. An example of the application of this analysis is presented for a hypothetical 75-story office building.