Resume Abstract

Abstract

Content

• 1. Goals and tasks
• 2. Relevance of the work of
• 3. A summary of the results of the master's work
• 4. Scientific novelty
• 5. Conclusion
• 6. List of sources

1. Goals and tasks

The purpose of the Master Thesis – study of the stability of air flows in inclined workings on condition of formation of thermal fire depression in several ventilation contours in the conditions of mine Dobropolskaya. In this paper, we consider the following objectives:

• development of a computer model of mine ventilation network;

• determination of ventilation circuit, where thermal fire depression is formed;

• determination of the maximum thermal fire depression in each separate part (separate ventilation circuit) of inclined working;

• simulation of simultaneous action of maximum thermal fire depression in all defined branches (circuits);

• analysis of the simulation results;

• development of measures to improve the sustainability of ventilation in inclined workings in fires.

2. Relevance of the work of

In accordance with the Rules for Safety in Coal Mines [1] sustainability assessment of ventilation at fires in inclined workings should be conducted in Ukrainian mines in the preparation of emergency response plan.

The current method of determining the thermal fire depression in inclined working [2] in the preparation of emergency response plan, allows one to calculate it only for a single working or part of the working (between the two nearest conjugations). At the same time, when the inclined working consists of several parts, there is a danger of formation of thermal depression in several ventilation circuits simultaneously. In an emergency, it can lead to an unexpected rollover of air flow, ventilation disruption and loss of life. Prevention of loss of stability of ventilation at fires in the inclined workings is an actual scientific and practical problem.

3. A summary of the results of the master's work

In the Master Thesis computer model of mine ventilation network Dobropolskaya is designed, conditions to maintain a stable ventilation of inclined workings in fires are researched and measures to ensure the sustainable movement of air flows in an emergency are developed.

In the compilation of the model, virtual images 424 of ventilation nodes and 613 branches were created. Length of the working, cross section, angle of inclination, height, and, where appropriate, the number of people on the branch are introduced in the table of branches (Edit > Table of branches). The yellow colour indicates the number of nodes, and the blue–branch numbers.

4. Scientific novelty

In the special part of the Master Thesis methodology of determining thermal fire depression simultaneously in several ventilation circuits will be used. Under the conditions of the mine Dobropolskaya such a calculation is performed for the first time.

Let us consider conditions of the formation of thermal fire depression in the example of parallel ‐ serial connection of two inclined workings (figure3).

Let us assume that in the inclined working 1–2–3–4 with downwards movement of the air, the fire broke out in the upper part (1–2) near the node 1. Fire gases, moving along the inclined working, will increase the temperature of the air and ventilation in the three circuits (1–2–7–8–1, 2–3–6–7–2, 3–4–5–6–3), contour thermal fire depressions will appear – ht1, ht2, ht3 (curly arrows show the direction of action of contour depressions). These sources of traction counteract downward movement of air and their combined effect may result in overturning stream on separate sites, and throughout the inclined working.

The existing methodology of sustainability assessment of ventilation does not TAKE INTO ACCOUNT the possibility of action of thermal depression in several circuits simultaneously. It is foreseen to model its action only in one circuit – where fire centre is located [2, 3].

Analysis of studies devoted to the terms of the spread of fire gases and the formation of temperature over the fire centre [4] has shown that already at a distance of 400 meters from the centre (in the direction of the movement of ventilation flow) temperature is reduced to 40°C. That is, it becomes close to the natural temperature of the air in a coal mine. On this basis, it can be assumed that the determination and simulation of thermal fire depression (simultaneously in several circuits) should be done only for those ventilation circuits that are connected to the emergency section of working for 400 meters over the fire centre (in the direction of air flow). So for example, if the length of working 1–2–3–4 is equal to 400 meters, it is necessary to model the effect of thermal depression simultaneously in three circuits, and if the length of site 1–2–3 is 400 meters, then the initially simultaneously in two circuits (1–2–7–8–1 and 2–3–6–7–2), and then simultaneously in the other two circuits (2 –3–6–7–2 and 3–4–5–6–3).

The feature of determining the stability of the air flow under simultaneous action of thermal fire depression in several circuits is that, when it is necessary to take into account the increase of the resistance of emergency working due to expansion of air in fire centre. Herewith resistance of emergency working can be maximum tripled [5]. In other words, the effect of a fire in one circuit reduces the critical depression of other circuits with inclined workings. Thus, if a fire occurs in site 1–2, then except the introduction of this branch thermal depression (–ht1) it is necessary to increase simultaneously the resistance of this branch. With the increasing resistance of the branch with a fire centre decreases the critical depression of underlaying of branches [6].

In view of the above, a new scenario for determining the stability of ventilation of inclined workings with a downward movement of air should be used. It should be used only in the case where the calculations have shown that according to the existing methodology ventilation of inclined workings at a fire will be sustainable. Following sequence of actions is suggested:

1. We determine ventilation circuits, where thermal fire depression (in inclined workings throughout 400m behind fire centre).
2. We determine the maximum thermal fire depression in each separate part (separate ventilation circuit) of inclined working by the existing methodology.
3. We calculate an emergency resistance of branch with fire centre.
4. We model simultaneous action of the maximum thermal fire depression in all defined branches (circuits).
5. We perform analysis of the simulation result and if ventilation remained stable, we stop further research.

This variant of determining the stability of ventilation allows you to immediately respond to a question about the need for further calculations and simulation of various options for forming thermal fire depression. If simulation of this variant indicates that ventilation is unstable, then it is necessary to go to the second stage of the calculations and take into account regularity of cooling fire gases along the inclined working. To do this, you need to calculate the maximum air temperature in the fire centre (Тmax) and the temperature at the end of site of inclined working (Тe.). For example, assuming that fire centre emerged at the beginning of the first site (near the node 1) and the maximum temperature in the burning centre is 1000°C, we calculate the air temperature near the nodes 3 and 4.

Knowing the final temperature at all sites of inclined working, depending on the location of occurrence of fire and the length of workings the total thermal depression on the entire length and for separate sites can be determined. When calculating temperatures and thermal depression sectional area of the entire working (1–2–3–4) and the angle of its inclination is the weighted average.

The calculation formula for the thermal fire depression (ht) is as follows [3]:

ht = 12 Z (0,766 + ln Tmax / Te),

where Z – vertical height of the combustion zone;

The difference of values of thermal depressions for separate parts of inclined working will determine the value of circuit thermal fire depressions. For example, the value of thermal depression (ht2) forming in the circuit 2–3–6–7–2 (fire centre at the site 1–2) is determined as the difference between the thermal fire depression counted separately for the site 1–2–3 and site 1–2

ht2 = h1–2–3 – h1–2.

Verification of new methodology is performed using computer program IRS Ventilation of mines – EPLA in the conditions of the coal mine Dobropolskaya.

Studies carried out confirm the need for the development and adoption of a new methodology for assessing the stability of the ventilation at fires in inclined workings of underground structures.

5. Conclusion

The problem Simulation fire allows automatic recalculating amount of thermal fire depression in mine working, calculating emergency air distribution, determining location of a possible rollover (change of direction) of the air, highlighting all workings in which fire gases fall (zone of exceeding the limit of gas). Number of emergency working is indicated, gets from DB its numerical characteristics. The simulation results of fire emergence are submitted to ventilation scheme (figure5). Emergency working is marked in red and working in which the products of combustion fall (zone of exceeding the limit of gas) – yellow.

In contrast to the natural draft of thermal depression that occurs at a fire in inclined or vertical working, has a local character, as the gases that are produced at a fire, moving on the working are intensively cooled.

At present in Master Thesis computer model of mine ventilation network in the conditions of the mine Dobropolskaya is developed. Database consisting of graphical and numerical information is prepared. Study of the stability of air flows in inclined workings on condition of formation thermal fire depression simultaneously in several ventilation circuits will be held in the future.

6. List of sources

1. Правила безопасности в угольных шахтах. – К.: Держохоронпраці. – 2005 г., – 398 с.
2. Болбат И.Э., Лебедев В.И., Трофимо В.А. Аварийные вентиляционные режимы в угольных шахтах. – М.: Недра. – 1992. – 206 с.
3. Рекомендации по выбору эффективных режимов проветривания шахт при авариях. – Донецк: НИИГД. – 1995. – 168 с.
4. Осипов С.Н., Жадан В.М. Вентиляция шахт при подземных пожарах. – М.: Недра, 1973. – 156 с.
5. Зинченко И.Н., Романченко С.Б., Ревякин А.В. Расчет на IBM PC температуры и депрессии вентиляционной струи при пожарах/ Горноспасательное дело: Cб.науч.тр. / НИИГД. – Донецк, 1986. – С. 52–59.
6. Трофимов В.А., Кавера А.Л., Калинич Н.М., Негрей А.Г. Влияние увеличения сопротивления наклонной выработки на устойчивость ее проветривания при пожаре/ Сб. докл. Вентиляция подземных сооружений и промышленная безопасность в ХХІ столетии. – Донецк: ДонНТУ. – 2012. – С. 73–76.
7. Трофимов В.А., Кавера А.Л., Каплун А.Ю., Принцева О.А. Исследование устойчивости проветривания в горных выработках шахты после увеличения сопротивления воздухоподающих стволов /Сб. докл. Вентиляция подземных сооружений и промышленная безопасность в ХХІ столетии. – Донецк: ДонНТУ. – 2013. – С. 45–48.
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