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28
D, = Z ,M ,,
l vx 2 1 pl 3
Z , CPl2 + Z1
+ D
+C
f B
pl 3
— + Dpl 2
Z p12
}+b.
pl 3
—+C12 +—
Z..... pl2 Z1
/
Bpl 2 \ Zvxl
1 f B
■I
vxn V vx1
pl 2
— + Dpl 2
Z pl2
+ ^
+D
pl 3
B
pl 2 Z
+ D,
'pl2 )> (4)
Substituting the values of Z^, Z„ 2, Zra 3, Zra 3, A'pl 3, Bfl 3, Cpi3, D'pi3, Api2, Bpi2 ,Cpi2, Dpi2 in the equation (), we obtain:
' Zp2Shïpl2 ^
A = chYpi A
pl 3 dshk
ChYpl 2lpl 2 +
1
Z1
+ Zvpl 2ShY pl 2 ^ sh7pl 3dshk ;
pl 3 dshk y
(5)
'vpl 3
Bl = Zvx2 [chYpl Jo* (chYpl2lpl2 +
1
Zvpl 2ShYpl 2
+ Zvp,2ShY„p2* Z ShYpl JdM ] + Zvp,3ShYpl JdM * ^
ChYpl 2lpl 2 +
'vpl 3
Zvpl 2ShYp,
'vpl2 i pl2 ''vxn
+ Zpi 2shYp, 2* chYp, iLk'' (6)
C = chYpi hhA
ChYpl 2l,
pl 2 pl 2
'vpl 2 1 pl 2 1
7'
''vxn
+ shYpl2lpl2
vpl 2
,Zpl2shYp,
Z1
1
+ — (-^Z^- + chYpl 2lpl 2)] + — shYpl 3lM * ^
'vpl 3
Z,pl2ShYpl2 ^ , , ! *, p + chYp,2pi21 ;
Dl = Zvx 2{chYpl ¿J-
chYpi 2I
pl2 pl 2
1
(7)
7j
"'vxn
+ — shYpl 2lpl 2 +^
vpl 2
+z^(
1 ^rpZ^Yp,2 + ^ ^ 2)] + _L_ shypi }lj!hk *
-'vpl 3
ZP 2shYp.
^Zi ~ + ChYpl2lpl2 } + Zvpl3ShYpl* ^
chYpi 2l,
pl2 pl2
\ vxn
1
Z1
+ —- shYpt 2lpi 2 + —
Z
-'vpl 2
+chYpi A
It is known that
pl 2 pl 2 zi /
pl 3 dshk
Z„pl 2ShYpl
+ chypl 21
Z'
pl 2 pl 2
V
vxn \ vxn
' pli?pl2
2ShY" 2 + chY J,
r U .
T _ mm .
— >
from whence
(8)
(9)
(10) (11)
(12)
(13)
(14)
where
Zpl — the resistance of the transfer track circuit during normal for the locomotive receiver.
Conclusions: The proposed analytical expressions for which you can analyze and synthesis of track circuits without isolating joints for locomotive receiver to develop and track circuits without isolating joints for railway lines in Uzbekistan.
U . = U +1. * Z' ;
mm 1 1 vxn '
U = I * B ■ I = I * D
U . = I, * B, +1, * D, * Z1 ;
mm till vxn
U ■
T __mm_
l~ B, + D, * Z1ym '' Zpi = B, + D, - ZL,
References:
1. Aliyev R. M. The equations and methods for determining the coefficients of continuous welded rail four-pole track circuits//Herald TashIIT. - Tashkent, 2008. - № 2. - P. 62.
2. Bryleev A. M., Kravtsov Y. A., Shishlyakov A. V The theory, structure and operation of track circuits. - M.: Transport, 1978. 344 p.
*
*
Sokolyanskiy Vladimir Vladislavovich, Research institute of mine rescue work, fire safety and civil defense «Respirator» Donetsk City, Ukrain E-mail: vv_sokol@mail.ru
Ways of increase of heat stability of a cabin of the fire truck
Abstract: Various means of passive heat protection of a cabin are offered for ensuring safe work of the driver of a fire truck in case of destructive fire. On the basis of experimental data and mathematical modeling the heat stability of a car cabin is defined. The comparative characteristic of efficiency of application of various means of heat protection is submitted.
Keywords: cabin of the fire truck, heat current of the fire, heat protection, safe internal environment, heat stability
Most often extinguishing of fires by means of fire trucks is are set at a long distance from the front of the flame. How-made by supplying of fire extinguishing substances on the ever in cases of extinguishing of fires by means of water supply hose lines streched to necessary length. In such cases trucks by hydraulic guns it is necessary to approach fire trucks to the
seat of fire. Such conditions are created at extinguishing of forest fires, fires at the gas- and oil-extracting and producing enterprises, timber yards, at elimination of major industrial accidents, etc.
The zone, from which the extinguishing is made, is limited to the maximum length of a stream of fire extinguishing substances and is in close proximity to the object of extinguishing. So, at water supply by hydraulic guns of the trucks length of the stream reaches 60 m, and length of the foam is up to 30 m. Supply of powder is made on distance of 30-35 m, and for trucks of gas-water extinguishing this value makes only 10-12m.
At fire extinguishing directly from the truck the tactical effectiveness of divisions increases as time of fighting expansion is reduced; besides, length of a stream of fire extinguishing substances increases, as there are no pressure losses in hoses.
Fire trucks are created on the chassis of serial trucks. Knots and component parts of cars are projected and made for operation in the conditions of influence of solar radiation, environmental temperature, wind and rainfall (humidity).
In the zones, which are directly adjoining the fire front, conditions of use of fire trucks cardinally differ from operating conditions of trucks of economical purpose. At extinguishing of the fires fire trucks are exposed to powerful thermal influence that leads to heating of their external surfaces. Truck walls under the influence of heat flows of 7-25 kW/sq.m heat up to 200-400 °C. Internal surfaces heat up to 80220 °C. These values of temperatures of heating are reached within 2-3 min. and fire extinguishing in such conditions becomes dangerous to the truck.
Duration of fighting work of a fire tanker at water supply by means of hydraulic guns from the tank, and also giving of fire extinguishing substances by trucks of the powder or combined extinguishing in zones of influence of heat emission is commensurable their expenditures over time. It strongly limits duration of safe work on hydraulic guns control. If in due time not to change the fighting position, fire trucks can fail and staff in cabins can get thermal injuries. Thus, safety of the fire truck on the fires is defined generally by the level of its resistance to the influence of heat emission — heat stability.
Heat stability of the fire truck is the property to keep during certain time in the conditions of powerful thermal influences the holding and defend ability of the body and the cabin, safe parameters of microclimate in the cabin and heat condition of mechanisms and systems of the truck. Therefore, possibility of fire extinguishing by the fire truck without change of the fighting position will be defined by heat stability.
Especially weak part of the fire truck is its cabin. The driver can maneuver in fire zone, operate the fixed monitor, in case of danger he can bring the truck out of the dangerous zone only until in the cabin the safe microclimate is held [6]. Therefore we must pay paramount attention to the issues of heat protection of the fire truck cabin.
There are two essentially various ways of heat protection of the truck cabin: active and passive. Certainly the effective way of active heat protection has an essential shortcoming: the fire extinguishing substance (water) that could be spent for fire extinguishing is spent for heat protection. Therefore such way is expedient only at stationary installation of the fire truck at a water source; at movement (change of fighting position) of the truck this way is undesirable.
Passive thermal protection is simpler, but at the correct application a rather effective remedy. The advantage of such way is also that it can be applied at production of a cabin as well as in use of the truck and even directly at the place of major fire as a protection express tool.
For the protection of the truck cabin against powerful heat emission the following technical means are offered [8]:
1) filling of the air layer of constructions with heat-insulating material. As heat-insulating material the felted fabric with sheet thickness of 15mm was tested;
2) covering of external surfaces of safeguards with materials with high heat-reflective properties. The walls covered with aluminum foil with thickness of 0,05mm and painted by aluminum paint were tested;
3) shielding of constructions in the air gap (aluminum foil or aluminum paint on one or both walls of the air gap);
4) application of special cockpit windows. Were subj ected to tests: windows with the pasted aluminized polyethylene terephthalate film, tinted windows with the deposited oxine-tin-antimony film, organic windows with thickness of 6mm, double windows of the automobile tempered glass and the plexiglas established outside without air gap;
5) use of a mesh screen on windows. The steel mesh by diameter of 3mm with sizes of cells 10mm*10mm, established outside of the cabin windows was applied.
Except individual ways were tested also:
6) complex of heat-shielding means allowing long usual operation of the fire truck equipped by means of heat protection. The complex of means consists of the external walls painted by aluminum paint and air gaps of safeguards filled with mineral wool, sheet plexiglas and the metal mesh at car windows;
7) express tool of heat protection, brought on the special fire fighting equipment and established on the fire trucks arriving to the fire place in possible short terms. The express tool includes pasting by aluminum foil of external surfaces of the cabin, pasting of windows with the aluminized polyethylene terephthalate film and installation on windows of the metal mesh.
Tests of the offered means of heat protection were carried out by theoretical calculations in the program [4] supplemented according to the mathematical model [7] modules of definition of temperature fields in the windows and air gaps of safeguards. Results of theoretical calculations were confirmed by full-scale natural experiments [3]. Divergences between the estimated data and experimental evidence didn't exceed 12-17% for walls of the cabin and 22-25% for its windows.
It is possible to estimate the efficiency of the offered cabin. Comparative efficiency of means of heat protection on
means of heat protection if taking the values of parameters in the extent of decrease in characteristic temperatures and a heat
a cabin of the production car (without the offered means of stream in the cabin in relation to the standard is presented in
heat protection) for a standard of microclimatic parameters in table 1.
Table 1. - Efficiency of heat protection of the truck cabin
Means of heat protection of the truck cabin Extent of decrease,%
of characteristic temperatures of heat
walls windows air flow
Production car (with no heat protection) - - - -
Heat insulation of walls from inside 15-26 0 12-21 18-41
Aluminum foil outside 68-71 0 35-42 62-71
Painting by aluminum paint outside 23-25 0 14-16 28-34
Aluminum foil in the gap 45-49 0 25-31 46-60
Painting of the gap with aluminum paint 10-17 0 5-11 18-21
Metallized film on the automobile glass 0 44-48 12-16 22-31
Tinted (with sputtering) automobile glass 0 5-7 5-7 9-14
Plexiglas instead of automobile glass 0 10-11 5-8 11-15
Plexiglas + automobile glass 0 13-20 8-11 13-20
Mesh screen on automobile glass 0 24-26 7-8 11-14
Complex of means of heat protection 47-51 38-44 37-47 63-73
Express tools of heat protection 70-74 66-70 55-71 94-95
Note. The concept «characteristic temperatures» designates of internal surfaces of the warmed elements of safeguards.
It should be noted that the means protecting nontransparent safeguards reduce temperature of walls and practically do not influence windows temperature. The means protecting windows reduce only the temperature of glasses and reduce the rate of heat stream passing through windows. But as temperatures of walls determine the average air temperature and heat stream in the cabin, the values of the last decrease when using all without exception of means of heat protection.
For determination of the most admissible level of external heat influences and assessment of efficiency of the offered means of heat protection it is necessary to be set by limit the values of microclimatic parameters in the truck cabin and to define the limits of heat stability of cabins with various means of heat protection.
The major heat factor defining the microclimate in the cabin and safety of the person is air temperature. Physiological researches established values of limit temperature: 6070 oC — at humidity up to 20% and 50 oC — at humidity of 70-75% [1, 10].
The cabin walls heat up in the first place under the influence of heat stream of the fire. From them then the air heats up and warmth on the interior of the cabin and on the driver is emissed [2]. Normative documents limit temperature of heated surfaces in systems of heating with value of 95 oC [5]. According to the researches conducted by all-union scientific research institute of labor protection (Tbilisi City) for the limit temperature of heated surfaces of protections the value of 100 oC in the absence of direct contact of the person's body with the heated surface is accepted.
medium-volume air temperature in the cabin and temperatures
The other, not less important factor of heat impact of the fire on the person is the heat emission. The person can be vaguely long without any protective equipment under the influence of heat emission with intensity of 1,0-1,4 kW/sq.m [9]. For staff of fire divisions the admissible value of density of heat stream the value of 2,5-3,0 kW/sq. m. is accepted at which firefighters can be in a usual canvas suit without additional resources of heat protection for a long time, and 4,2 kW/sq.m at which firefighters can work in fighting clothes and helmets with protective glass [9; 10].
On the fire the impulse wave at explosion can also represent danger to the truck and the person. With an excessive pressure of the impulse wave of 20-40 kPas damage of design of the truck is already possible (first of all destruction of windows) and easy damages of the person (bruises, dislocations, temporary loss of hearing), deadly damages of the person are possible with an excessive pressure of 100 kPas and more [10]. However serial cargo and fire trucks are not designed for resistance to the influence of impulse wave and are not tested.
This means that limit thermal parameters of microclimate in the cabin should be considered as the following: radiation temperatures of walls — 100 oC; average air temperature in the cabin — 60 oC; intensity of heat stream in the cabin — 2,5 kW/sq. m. On the basis of these limit parameters of microclimate in the cabin the levels of heat loading of the cabin at which its heat stability persists (table 2) are determined by mathematical model [7].
Tables 2. - Limits of heat stability of the truck cabin of ZIL-131 (3M^-131)
Means of heat protection of the truck cabin Heat stability of the cabin, kW/sq. m.
in consideration of characteristic temperatures in consideration
walls windows air of heat flow
Production car (with no heat protection) 1,7 2,5 4,6 8,0
Heat insulation of walls from inside 2,4 2,5 6,1 10,2
Aluminum foil outside 13,6 2,5 11,0 19,2
Painting by aluminum paint outside 3,5 2,5 6,1 10,6
Aluminum foil in the gap 5,9 2,5 8,5 14,9
Painting of the gap with aluminum paint 2,8 2,5 5,6 9,6
Metallized film on the automobile glass 1,7 7,2 6,1 10,1
Tinted (with sputtering) automobile glass 1,7 2,9 5,1 8,8
Plexiglas instead of automobile glass 1,7 3,0 5,2 8,9
Plexiglas + automobile glass 1,7 3,7 5,6 9,2
Mesh screen on automobile glass 1,7 4,1 5,2 8,9
Complex of means of heat protection 6,4 6,4 13,3 20,1
Express tools of heat protection 16,9 16,8 39,0 >50
According to the results, the greatest impact, of all thermal parameters, on the person in the truck has the temperature ofsur-face of safeguards. According to calculation the cabin of the production car persists heat stability only at the power ofheat stream of1,7 kW/sq.m (on wall temperature). The trucks equipped with means ofthermal protection provide a safe microclimate in cabins at big levels ofheat emission of the fire. As to be expected, the heat stability of cabins of the trucks equipped with a complex of means of heat protection and express tool of heat protection is of the maximum value (respectively 6,4 kW/sq.m and 16,8 kW/sq.m on windows temperature).
Thus, for providing a safe microclimate in the cabin of the fire truck various means of passive heat protection of the
cabin are offered. The efficiency of the offered means was estimated in accordance with the maximum value of heat stream at which the truck cabin keeps heat stability. The heat stability of the truck cabin was checked in four thermal parameters of microclimate: temperatures of internal surface of the warmed wall and the warmed windows, air temperature in the cabin, heat stream in the cabin.
The decrease value in parameters of microclimate in the cabin at application of various means of heat protection changes in very wide limits. According to these values the most effective, as to be expected, are the offered complexes of means of heat protection.
References:
1. Ажаев А. Н. Влияние высокой температуры на работоспособность человека/А. Н. Ажаев, В. И. Зорилэ, А. Н. Кольцов/Космическая биология и авиакосмическая медицина, 1980. - С. 35-38.
2. Бабалов А. Ф. Промышленная теплозащита в металлургии/А. Ф. Бабалов. - М.: Металлургия. - 1971. - 359 с.
3. Исхаков Х. И. Защита автотранспортных средств от воздействия тепловых потоков пожара: дис. ... доктора техн. наук: 05.05.03, 05.26.01/Исхаков Харис Исхакович; Моск. гос. техн. ун-т им. Н. Э. Баумана. - М., 1991. - 338 с.
4. Исхаков Х. И. Программа определения параметров теплообмена замкнутых систем с окружающей средой/Х. И. Исхаков, В. М. Астапенко, А. Н. Шевляков, В. В. Соколянский. - М.: ГФАП СССР № 50900000305, 1990. - 72 с.
5. Опалення, вентилящя та кондицюнування: ДБН В.2.5-б7:2013. - Офщ. вид. - К.: Укрархбудшформ: Мшрегюн Укра'ни, 2013. - 149 с.
6. Соколянский В. В. Микроклимат в кабине пожарного автомобиля/Соколянский В. В., Исхаков Х. И., Кошмаров Ю. А.//Зб. наук. пр. Мгжнародно'' конференцп «Проблеми пожежно'' безпеки». - Ки'в: МВС Укра'ни, 1995. -С. 162-163.
7. Соколянский В. В. Моделирование процесса теплообмена кабины автомобиля с окружающей средой//Вестник Донбасской государственной академии строительства и архитектуры. - Макеевка, 1995. № 95-1 (1). - С. 142-147.
8. Соколянский В. В. Способы тепловой защиты кабины пожарного автомобиля//Вестник Донбасской государственной академии строительства и архитектуры. - Макеевка, 1996. № 96-3 (4). - С. 144-146.
9. Тактика действий подразделений пожарной охраны при пожарах на автоцистернах для перевозки легковоспламеняющихся и горючих жидкостей: рекомендации./ - М.: ВНИИПО, 2004. - 47 с.
10. Теребнев В. В. Справочник спасателя-пожарного: справочник/В. В. Теребнев, Н. С. Артемьев, В. А. Грачев. - М.: Центр пропаганды, 2006. - 294 с.
