CN109057848B - method for determining maximum value of wind ratio number of closed type circulation ventilation of extra-long road tunnel - Google Patents
method for determining maximum value of wind ratio number of closed type circulation ventilation of extra-long road tunnel Download PDFInfo
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- E21F1/00—Ventilation of mines or tunnels; Distribution of ventilating currents
- E21F1/003—Ventilation of traffic tunnels
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
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Abstract
The invention discloses a method for determining a maximum value of a wind division ratio number of closed circulation ventilation of an extra-long road tunnel. The method mainly comprises the following steps: firstly, determining the nonlinear relation between the critical effective air volume of the dust remover and the air dividing ratio; then, a derivation rule in advanced mathematics is applied to calculate a first order partial derivative and a second order partial derivative of the critical effective air quantity of the dust remover to the air distribution ratio; according to the determination method of the extreme value, the first order partial derivative and the second order partial derivative in the higher mathematics, when the first order partial derivative is equal to 0 and the second order partial derivative is less than 0, a maximum value exists, and therefore a calculation formula of the maximum value of the wind ratio number of the starting wind is established. When the actual wind ratio of the closed type controllable circulating ventilation system is larger than the maximum value of the wind ratio, the concentration of the smoke dust of the parallel wind flow in the short tunnel channel exceeds the allowable concentration, and the vehicle continuously running in the short tunnel channel is unsafe, so that the pre-evaluation of the closed type circulating ventilation system can be quickly and quickly completed.
Description
Technical Field
the invention belongs to the technical field of tunnel disaster prevention and reduction, and particularly relates to a method for determining a maximum value of a wind ratio number for closed controllable circulating ventilation of a tunnel of an extra-long highway.
Background
the highway tunnel is a half-sunk or shallow-buried narrow and long space, and is an important problem which is always concerned by the industry in treating pollutants such as smoke dust and the like generated by vehicles running in the tunnel. The method generally adopts a mechanical ventilation method to dilute pollutants such as smoke dust, CO and the like, discharges dirty air to the environment outside the tunnel, and belongs to a straight-flow system scheme. The ventilation system of the long-distance or extra-long-distance highway tunnel must be matched with a ventilation vertical shaft to meet the wind demand of diluting pollutants in the tunnel. The ventilation of the tunnel of the extra-long highway particularly relates to the optimization of influence factors such as a vertical shaft excavation position, a ventilator, a jet fan group, an air duct and the like, and is a leading-edge problem in the industry.
at present, external fresh air is introduced into the tunnel to dilute pollutants discharged by vehicles, and then the polluted air is discharged out of the tunnel, which is the traditional tunnel ventilation with high energy consumption. Adopting shaft sectional air supply, introducing external fresh air, diluting pollutants in the extra-long tunnel, ensuring the concentration of the pollutants to be within a safe value, and finally discharging dirty air through the sectional shaft; the common ventilation system of the shaft sectional air supply and exhaust tunnel is practiced by Kwa G S, Xia Yong Xue and the like. For the method of the application model tests such as traffic wind, the superordinate and Wang and the like formed by driving in the tunnel, the condition that the driving direction of the air supply outlet and the tunnel is 6 degrees, and the included angle between the air exhaust outlet and the driving direction of the tunnel is not more than 30 degrees is obtained; then, the supernumerary and the like clearly indicate that the ventilation shaft air supply and exhaust type longitudinal ventilation system always has the problems of large civil engineering cost and large operation energy consumption. Aiming at an extra-long tunnel with high construction cost of a ventilation shaft or without a set condition, double-hole complementary ventilation is firstly proposed by Berner and the like by utilizing the characteristic of uneven ventilation load of an uplink and a downlink; by using model experiments and numerical simulation, Zhangguanpeng verifies and checks design parameters, and double-hole complementary ventilation is applied to the brocade tunnel; through experimental actual measurement, the flow field in the tunnel under the double-hole complementary ventilation is deeply researched by the moleon and the like, the feasibility of the ventilation mode is further demonstrated, and the double-hole complementary ventilation mode is generally suitable for the highway tunnel between 4km and 7 km. However, the problems that the ventilation cost of the extra-long tunnel is high, the shaft excavation position is restricted by geology and city planning and the like are still outstanding, and a method for determining the maximum value of the wind division ratio number for closed type controllable circulating ventilation of the extra-long road tunnel is not formed.
disclosure of Invention
the invention aims to provide a method for determining the maximum value of the wind ratio of the closed type circulating ventilation of an extra-long highway tunnel, so that the pre-evaluation of the implementation of a closed type circulating ventilation system can be quickly and rapidly completed.
the purpose of the invention is realized by the following technical scheme: the method for determining the maximum value of the wind division ratio of the closed type circulating ventilation system of the extra-long highway tunnel is used for determining the maximum value of the wind division ratio of the closed type controllable circulating ventilation system of the extra-long highway tunnel; the closed controllable circulating ventilation system for the extra-long highway tunnel comprises a circulating air duct which is arranged in a tunnel bypass tunnel and is parallel to the tunnel, an upstream tunnel is arranged between a tunnel inlet and an induced air section of the circulating air duct, a downstream tunnel is arranged between an injection section of the circulating air duct and a tunnel outlet, the circulating air duct is communicated with the tunnel through the induced air section and the injection section at two ends of the circulating air duct, and a short tunnel is arranged between the upstream tunnel and the downstream tunnel; a dust remover is arranged in the circulating air duct;
The method is characterized by comprising the following steps:
Determining the nonlinear relation between the critical effective air volume of the dust remover and the air dividing ratio:
(a) The calculation formula for determining the critical effective air volume of the dust remover is as shown in formula (1):
Q＝ω·Q (1)；
in the formula, Q eta omega c is critical effective air quantity of the dust remover, m 3/s; q eta is the flow rate of unpurified circulating air flowing into the dust remover, and m 3/s; omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number;
(b) the calculation formula for determining the flow rate of the unpurified circulating air flowing into the dust remover is as follows (2):
Q＝e·Q (2)；
in the formula: e is a fractional wind ratio number and a dimensionless number; qr is the flow rate of external fresh air introduced from the tunnel inlet, m 3/s;
(c) the calculation formula for determining the critical effective air volume coefficient of the dust remover is as shown in formula (3):
in the formula: delta 1c is the critical smoke concentration of the upstream air flow, m-1; delta is the smoke tolerance concentration for the ventilation design, m-1;
(d) On the premise of meeting the ventilation design requirement, when delta 2 is delta, determining the critical smoke concentration calculation formula of the upstream wind flow as formula (4):
In the formula: delta 2 is the concentration of the smoke dust of the parallel air flow of the short tunnel, and m-1; c is a smoke flow comprehensive influence factor m/s; ls is the length of the tunnel short track, m;
(e) Substituting the formula (4) into the formula (3), and then substituting the formula (3) and the formula (2) into the formula (1) to obtain a nonlinear relation formula of the critical effective air volume and the air distribution ratio of the dust remover, wherein the nonlinear relation formula is as shown in the formula (5):
(II) applying a derivation rule in advanced mathematics, wherein a first-order partial derivative of the critical effective air quantity of the dust remover to the fractional air ratio is as shown in the formula (6):
And (III) applying a derivation rule in advanced mathematics, wherein a second-order partial derivative of the critical effective air quantity of the dust remover to the air distribution ratio is as shown in the formula (7):
fourthly, according to the determination method of the extreme value, the first order partial derivative and the second order partial derivative in the higher mathematics, when the first order partial derivative of the formula (6) is equal to 0 and the second order partial derivative of the formula (7) is less than 0, a maximum value exists; in equation (6), e is replaced by ec, and the equation is made to establish the maximum of the fractional wind ratio as calculated in equation (8):
in the formula, ec is the maximum value of the number of the wind division ratio, and is a dimensionless number; c is a dependent variable ratio of the comprehensive influence factor of the smoke flow and the design concentration, and m 2/s;
the formula (8) shows that when the actual wind ratio of the closed type controllable circulating ventilation system is larger than the maximum value of the wind ratio, the concentration of the smoke dust of the parallel wind flow in the short tunnel channel exceeds the allowable concentration, and the vehicle running in the short tunnel channel is unsafe.
Specifically, the determination methods of the formulas (2), (3) and (4) in the steps (a), (b), (c) and (d) are as follows:
according to the existing engineering calculation method, the tunnel smoke flow calculation formula is obtained as the following formula (9):
in the formula, QVI is the tunnel smoke flow, m 2/s; qVI is the standard emission of smoke dust, m 2/veh.km; fa (VI) is a dimensionless number considering the vehicle condition coefficient of smoke; fd is the vehicle density coefficient and is a dimensionless number; fh (VI) is a dimensionless altitude coefficient considering the smoke; fiv (VI) is a dimensionless number considering the longitudinal slope-vehicle speed coefficient of the smoke; nD is the number of vehicle types of the diesel vehicle and is a dimensionless number; nm is the traffic volume of the corresponding vehicle type, veh/h; fm (VI) is the model coefficient of the diesel vehicle considering smoke dust, and is a dimensionless number; l is the tunnel length, m;
wherein, the calculation formula of the comprehensive influence factor C of the smoke flow is as follows:
In the formula (9), when the reference emission is unchanged, and the dimensionless numbers of the vehicle condition, the vehicle density, the gradient, the vehicle speed and the vehicle type of the diesel vehicle are unchanged, and the influence caused by the altitude change can be ignored, the tunnel smoke flow is a function of the tunnel length and the comprehensive influence factor;
(II) applying the formulas (9) and (10), the soot concentration of the upstream air flow passing through the upstream tunnel is calculated by the formula (11):
in the formula, delta 1 is the smoke concentration of the upstream air flow, and m-1; l1 is the length of the upstream tunnel, m; qr is the flow rate of external fresh air introduced from the tunnel inlet, m 3/s;
(III) the fractional wind ratio is determined by equation (12):
In the formula: e is a fractional wind ratio number and a dimensionless number; q is the air flow rate of the air which is divided to the induced draft section of the circulating air duct, and m 3/s;
according to the mass conservation principle, the wind amount calculation formula of the parallel wind flow of the short tunnel channel is as follows (13):
Q＝(1-e)·Q (13)；
in the formula, Qs is the air volume of the parallel air flow of the short tunnel, and m 3/s;
because the unpurified circulating air flow Q eta flowing into the dust remover is the air flow Q divided to the induced air section of the circulating air duct, in the formula (12), Q eta is replaced by Q, and the formula (12) is deformed, so that the calculation formula of the unpurified circulating air flow Q flowing into the dust remover is obtained as the formula (2):
Q＝e·Q (2)；
(IV) the method for calculating the smoke concentration of the parallel air flow of the short tunnel comprises the following steps:
The smoke flow of the parallel wind flow comes from two parts, wherein in the first part, the smoke flow carried by the upstream wind flow; secondly, the flow of smoke and dust generated by the emission of vehicles running in the short tunnel;
the flow of the smoke carried by the upstream air flow influencing the flow of the smoke of the parallel air flow is calculated as the following formula (14):
Q＝δQ (14)；
where Qs1(VI) is the soot flow rate from the upstream stream, m 2/s;
Substituting formula (13) for formula (14) to give formula (15):
Q＝δ(1-e)Q (15)；
in addition, the flow rate of the smoke generated by the emission of the vehicle running in the short tunnel road is calculated as the following formula (16):
Q＝C·L (16)；
in the formula, Qs2(VI) is the newly added smoke flow in the parallel wind flow of the short tunnel, m 2/s; ls is the length of the tunnel short track, m;
according to the basic principle of physics, applying the formula (15), the formula (16) and the formula (13) to obtain the smoke concentration of the parallel wind flow of the tunnel short channel, and calculating the smoke concentration as the formula (17):
in the formula, delta 2 is the smoke concentration of the parallel wind flow, and m-1;
(V) determining the effective air volume coefficient of the dust remover:
in order to characterize the effect of the smoke concentration of the circulating air flow on the performance and the limit utilization of the dust remover, the effective air quantity coefficient of the dust remover is defined as the ratio of the smoke concentration of the unpurified circulating air flow flowing into the dust remover, namely the smoke concentration of the upstream air flow to the smoke allowable concentration of the ventilation design, namely the formula (18) shows:
in the formula, omega is the effective air quantity coefficient of the dust remover and has no dimensional number; δ 1 is the smoke concentration of the upstream air stream; delta is the allowable concentration of smoke dust in the tunnel ventilation design, m-1;
(VI) determining the critical smoke concentration of the upstream air flow and the critical effective air volume coefficient of the dust remover:
On the premise of meeting the ventilation design requirement, when δ 2 is δ, applying and deforming equation (17), and replacing δ 1 with δ 1c to obtain the critical smoke concentration calculation equation of the upstream wind flow as equation (4):
in the formula, delta 1c is the critical smoke concentration of the upstream air flow of the upstream tunnel, and m-1;
In the formula (18), replacing δ 1 with δ 1c and replacing ω with ω c, the calculation formula of the critical effective air volume coefficient of the dust remover is obtained as the formula (3):
In the formula, omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number.
compared with the prior art, the invention has the following beneficial effects:
the method can be used for determining the maximum value of the wind division ratio of the closed type controllable circulating ventilation of the tunnel of the extra-long highway, can avoid the complicated calculation of dimensional numerical parameters such as the length of the tunnel, the section size and the like, or the network calculation of a ventilation system, or the computation of fluid dynamics numerical simulation which is complicated and time-consuming, quickly and quickly determine the maximum value of the wind division ratio of the closed type controllable circulating ventilation of the tunnel of the extra-long highway, and check the parallel short channels and the ratio-dependent variables of the circulating air channels, thereby ensuring the running safety of vehicles in the parallel short channels.
Drawings
Fig. 1 is a schematic structural diagram of a closed type controllable circulating ventilation system of an extra-long road tunnel.
fig. 2 is a schematic diagram of the wind flow principle of the closed type controllable circulating ventilation system of the extra-long road tunnel.
Fig. 3 is a graph showing the influence of the tunnel stub length (i.e., the parallel stub length) on the maximum value of the air ratio (fresh air flow rate is 300m3/s) according to the embodiment of the present invention.
fig. 4 is a graph showing the influence of the tunnel stub length (i.e., the parallel stub length) on the maximum value of the air ratio (fresh air flow rate is 340m3/s) according to the embodiment of the present invention.
fig. 5 is a graph showing the influence of the tunnel stub length (i.e., the parallel stub length) on the maximum value of the air ratio (fresh air flow rate is 360m3/s) according to the embodiment of the present invention.
fig. 6 is a graph showing the influence of the tunnel stub length (i.e., the parallel stub length) on the maximum value of the air ratio (fresh air flow rate is 400m3/s) according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
referring to fig. 1 and 2, the closed controllable circulating ventilation system for the tunnel of the extra-long highway comprises a circulating air duct 5 which is arranged in a bypass tunnel of the tunnel and is parallel to the tunnel, an upstream tunnel 2 is arranged between an air induction section 3 of the tunnel inlet 1 and the circulating air duct 5, a downstream tunnel 8 is arranged between an ejection section 7 of the circulating air duct 5 and a tunnel outlet 9, the circulating air duct 5 is communicated with the tunnel through the air induction section 3 and the ejection section 7 at two ends of the circulating air duct, and a short tunnel 10 is arranged between the upstream tunnel 2 and the downstream tunnel 8; the circulating air duct 5 is internally provided with a dust remover 11, 4 is an inlet of the dust remover, and 6 is an outlet of the dust remover.
when the closed controllable circulating ventilation system is used, fresh air flow A of the environment outside the tunnel is introduced through the tunnel inlet 1, flows through the upstream tunnel 2 of the circulating air duct 5, and is continuously mixed and carries pollutants such as smoke dust, CO and the like to form upstream air flow B. Part of the upstream air flow B flows into the short tunnel channel 10 to continuously dilute the pollutants into a parallel air flow F. And the other part of the upstream air flow B passes through the circulating air duct induced air section 3 and flows into the circulating air duct 5, and is called as unpurified circulating air flow C. Under the action of the dust remover 11, the unpurified circulating air flow C passes through the dust remover 11 to remove particulate pollutants such as smoke dust and the like, is purified and flows out of the dust remover outlet 6 to be converted into purified circulating air flow D. In the circulating air duct injection section 7, the purified circulating air flow D is mixed with the parallel air flow F flowing through the tunnel short duct 10, and then the purified circulating air flow D is converted into the downstream air flow E. In the downstream tunnel 8 of the circulating air duct, the downstream air flow E continues to dilute the pollutants and ensures that the concentration of pollutants in the downstream tunnel 8 of the circulating air duct remains within the prescribed safety values, ensuring the need for air.
the invention relates to a method for determining the maximum value of the wind ratio number based on the closed type controllable circulating ventilation system of the extra-long highway tunnel, which comprises the following steps:
according to the existing engineering calculation method, the tunnel smoke flow calculation formula is obtained as the following formula (9):
in the formula, QVI is the tunnel smoke flow, m 2/s; qVI is the standard emission of smoke dust, m 2/veh.km; fa (VI) is a dimensionless number considering the vehicle condition coefficient of smoke; fd is the vehicle density coefficient and is a dimensionless number; fh (VI) is a dimensionless altitude coefficient considering the smoke; fiv (VI) is a dimensionless number considering the longitudinal slope-vehicle speed coefficient of the smoke; nD is the number of vehicle types of the diesel vehicle and is a dimensionless number; nm is the traffic volume of the corresponding vehicle type, veh/h; fm (VI) is the model coefficient of the diesel vehicle considering smoke dust, and is a dimensionless number; l is the tunnel length, m;
wherein, the calculation formula of the comprehensive influence factor C of the smoke flow is as follows:
in the formula (9), when the reference emission is unchanged, and the dimensionless numbers of the vehicle condition, the vehicle density, the gradient, the vehicle speed and the vehicle type of the diesel vehicle are unchanged, and the influence caused by the altitude change can be ignored, the tunnel smoke flow is a function of the tunnel length and the comprehensive influence factor;
(II) applying the formulas (9) and (10), the soot concentration of the upstream air flow passing through the upstream tunnel is calculated by the formula (11):
in the formula, delta 1 is the smoke concentration of the upstream air flow, and m-1; l1 is the length of the upstream tunnel, m; qr is the flow rate of external fresh air introduced from the tunnel inlet, m 3/s;
(III) the fractional wind ratio is determined by equation (12):
in the formula: e is a fractional wind ratio number and a dimensionless number; q is the air flow rate of the air which is divided to the induced draft section of the circulating air duct, and m 3/s;
according to the mass conservation principle, the wind amount calculation formula of the parallel wind flow of the short tunnel channel is as follows (13):
Q＝(1-e)·Q (13)；
in the formula, Qs is the air volume of the parallel air flow of the short tunnel, and m 3/s;
because the unpurified circulating air flow Q eta flowing into the dust remover is the air flow Q divided to the induced air section of the circulating air duct, in the formula (12), Q eta is replaced by Q, and the formula (12) is deformed, so that the calculation formula of the unpurified circulating air flow Q flowing into the dust remover is obtained as the formula (2):
Q＝e·Q (2)；
(IV) the method for calculating the smoke concentration of the parallel air flow of the short tunnel comprises the following steps:
the smoke flow of the parallel wind flow comes from two parts, wherein in the first part, the smoke flow carried by the upstream wind flow; secondly, the flow of smoke and dust generated by the emission of vehicles running in the short tunnel;
the flow of the smoke carried by the upstream air flow influencing the flow of the smoke of the parallel air flow is calculated as the following formula (14):
Q＝δQ (14)；
where Qs1(VI) is the soot flow rate from the upstream stream, m 2/s;
substituting formula (13) for formula (14) to give formula (15):
Q＝δ(1-e)Q (15)；
in addition, the flow rate of the smoke generated by the emission of the vehicle running in the short tunnel road is calculated as the following formula (16):
Q＝C·L (16)；
in the formula, Qs2(VI) is the newly added smoke flow in the parallel wind flow of the short tunnel, m 2/s; ls is the length of the tunnel short track, m;
according to the basic principle of physics, applying the formula (15), the formula (16) and the formula (13) to obtain the smoke concentration of the parallel wind flow of the tunnel short channel, and calculating the smoke concentration as the formula (17):
in the formula, delta 2 is the smoke concentration of the parallel wind flow, and m-1;
(V) determining the effective air volume coefficient of the dust remover:
in order to characterize the effect of the smoke concentration of the circulating air flow on the performance and the limit utilization of the dust remover, the effective air quantity coefficient of the dust remover is defined as the ratio of the smoke concentration of the unpurified circulating air flow flowing into the dust remover, namely the smoke concentration of the upstream air flow to the smoke allowable concentration of the ventilation design, namely the formula (18) shows:
in the formula, omega is the effective air quantity coefficient of the dust remover and has no dimensional number; δ 1 is the smoke concentration of the upstream air stream; delta is the allowable concentration of smoke dust in the tunnel ventilation design, m-1;
(VI) determining the critical smoke concentration of the upstream air flow and the critical effective air volume coefficient of the dust remover:
on the premise of meeting the ventilation design requirement, when δ 2 is δ, applying and deforming equation (17), and replacing δ 1 with δ 1c to obtain the critical smoke concentration calculation equation of the upstream wind flow as equation (4):
In the formula, delta 1c is the critical smoke concentration of the upstream air flow of the upstream tunnel, and m-1;
in the formula (18), replacing δ 1 with δ 1c and replacing ω with ω c, the calculation formula of the critical effective air volume coefficient of the dust remover is obtained as the formula (3):
In the formula, omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number.
(VII) applying the principle of mass conservation which is the basis of physics to determine the calculation formula of the critical effective air volume of the dust remover as shown in the formula (1):
Q＝ω·Q (1)；
in the formula, Q eta omega c is critical effective air quantity of the dust remover, m 3/s; q eta is the flow rate of unpurified circulating air flowing into the dust remover, and m 3/s; omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number;
substituting the formula (4) into the formula (3), and then substituting the formula (3) and the formula (2) into the formula (1) to obtain a nonlinear relation formula of the critical effective air volume and the air distribution ratio of the dust remover, wherein the nonlinear relation formula is as shown in the formula (5):
(VIII) applying a derivation rule in higher mathematics, wherein a first-order partial derivative of the critical effective air quantity of the dust remover to the fractional air ratio is as shown in formula (6):
applying a derivation rule in advanced mathematics, wherein a second-order partial derivative of the critical effective air quantity of the dust remover to the air distribution ratio is as follows (7):
when the second order partial derivative of the formula (7) is less than 0 and the first order partial derivative of the formula (6) is equal to 0, further, according to an extreme value judgment method in advanced mathematics, the derivation independent variable in the formula (6) has a maximum value; then, in the formula (6), e is replaced by ec, and the calculation formula of the maximum value of the wind division ratio is obtained as the formula (19):
In the formula: ec is the maximum value of the number of the wind division ratios and is a dimensionless number; c is the dependent ratio of the comprehensive influence factor of the smoke flow and the design concentration, m 2/s;
further, in engineering sense, it can be denied that the maximum value of the wind division ratio number is not likely to be larger than 1, and therefore, equation (19) is simplified to equation ():
the formula (8) shows that the maximum value of the wind division ratio is inversely proportional to the length of the short tunnel and the factor ratio, and the maximum value of the wind division ratio is proportional to the fresh air flow rate.
the following is an experimental example for determining the influence degree of the tunnel short-path length, the fresh air flow volume and the factor ratio on the maximum value of the fractional air ratio, and the specific operation is as follows:
(a) setting the flow rates of fresh air flows as 300m3/s, 340m3/s, 360m3/s and 400m3/s respectively;
(b) setting the factor transformation ratio numbers as 0.05m/s, 0.10m/s, 0.15m/s, 0.20m/s and 0.25m/s respectively;
(c) setting the length range of the short tunnel channel to be 0m to 150 m;
(d) the above values are substituted into the formula (8) to calculate, and the results are shown in fig. 3 to 6.
by analyzing the specific embodiments, the following summary is made: (1) the maximum value of the wind division ratio is reduced along with the increase of the length of the short channel of the tunnel; with the increase of the factor ratio, the maximum value of the wind ratio is reduced; along with the increase of the fresh air flow quantity, the maximum value of the air dividing ratio number is slowly increased. (2) The method quantifies the influence degree of the tunnel short path length, the fresh air flow quantity and the factor ratio on the maximum value of the fractional air ratio.
Claims (1)
1. a method for determining the maximum value of the wind division ratio of the closed type circulating ventilation system of an extra-long highway tunnel is used for determining the maximum value of the wind division ratio of the closed type controllable circulating ventilation system of the extra-long highway tunnel; the closed controllable circulating ventilation system for the extra-long highway tunnel comprises a circulating air duct which is arranged in a tunnel bypass tunnel and is parallel to the tunnel, an upstream tunnel is arranged between a tunnel inlet and an induced air section of the circulating air duct, a downstream tunnel is arranged between an injection section of the circulating air duct and a tunnel outlet, the circulating air duct is communicated with the tunnel through the induced air section and the injection section at two ends of the circulating air duct, and a short tunnel is arranged between the upstream tunnel and the downstream tunnel; a dust remover is arranged in the circulating air duct;
the method is characterized by comprising the following steps:
determining the nonlinear relation between the critical effective air volume of the dust remover and the air dividing ratio:
(a) the calculation formula for determining the critical effective air volume of the dust remover is as shown in formula (1):
Q＝ω·Q (1)；
in the formula, Q eta omega c is critical effective air quantity of the dust remover, m 3/s; q eta is the flow rate of unpurified circulating air flowing into the dust remover, and m 3/s; omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number;
(b) the calculation formula for determining the flow rate of the unpurified circulating air flowing into the dust remover is as follows (2):
Q＝e·Q (2)；
in the formula: e is a fractional wind ratio number and a dimensionless number; qr is the flow rate of external fresh air introduced from the tunnel inlet, m 3/s;
(c) the calculation formula for determining the critical effective air volume coefficient of the dust remover is as shown in formula (3):
in the formula: delta 1c is the critical smoke concentration of the upstream air flow, m-1; delta is the smoke tolerance concentration for the ventilation design, m-1;
(d) on the premise of meeting the ventilation design requirement, when delta 2 is delta, determining the critical smoke concentration calculation formula of the upstream wind flow as formula (4):
in the formula: delta 2 is the concentration of the smoke dust of the parallel air flow of the short tunnel, and m-1; c is a smoke flow comprehensive influence factor m/s; ls is the length of the tunnel short track, m;
(e) substituting the formula (4) into the formula (3), and then substituting the formula (3) and the formula (2) into the formula (1) to obtain a nonlinear relation formula of the critical effective air volume and the air distribution ratio of the dust remover, wherein the nonlinear relation formula is as shown in the formula (5):
(II) applying a derivation rule in advanced mathematics, wherein a first-order partial derivative of the critical effective air quantity of the dust remover to the fractional air ratio is as shown in the formula (6):
and (III) applying a derivation rule in advanced mathematics, wherein a second-order partial derivative of the critical effective air quantity of the dust remover to the air distribution ratio is as shown in the formula (7):
fourthly, according to the determination method of the extreme value, the first order partial derivative and the second order partial derivative in the higher mathematics, when the first order partial derivative of the formula (6) is equal to 0 and the second order partial derivative of the formula (7) is less than 0, a maximum value exists; in equation (6), e is replaced by ec, and the equation is made to establish the maximum of the fractional wind ratio as calculated in equation (8):
in the formula, ec is the maximum value of the number of the wind division ratio, and is a dimensionless number; c is a dependent variable ratio of the comprehensive influence factor of the smoke flow and the design concentration, and m 2/s;
the formula (8) shows that when the actual wind ratio of the closed type controllable circulating ventilation system is greater than the maximum value of the wind ratio, the concentration of the smoke dust of the parallel wind flow in the short tunnel channel exceeds the allowable concentration, and the vehicle running in the short tunnel channel is unsafe;
The determination method of the formulas (2), (3) and (4) in the steps (a), (b), (c) and (d) is as follows:
according to the existing engineering calculation method, the tunnel smoke flow calculation formula is obtained as the following formula (9):
in the formula, QVI is the tunnel smoke flow, m 2/s; qVI is the smoke dust reference emission, m2/(veh km); fa (VI) is a dimensionless number considering the vehicle condition coefficient of smoke; fd is the vehicle density coefficient and is a dimensionless number; fh (VI) is a dimensionless altitude coefficient considering the smoke; fiv (VI) is a dimensionless number considering the longitudinal slope-vehicle speed coefficient of the smoke; nD is the number of vehicle types of the diesel vehicle and is a dimensionless number; nm is the traffic volume of the corresponding vehicle type, veh/h; fm (VI) is the model coefficient of the diesel vehicle considering smoke dust, and is a dimensionless number; l is the tunnel length, m;
wherein, the calculation formula of the comprehensive influence factor C of the smoke flow is as follows:
in the formula (9), when the reference emission is unchanged, and the dimensionless numbers of the vehicle condition, the vehicle density, the gradient, the vehicle speed and the vehicle type of the diesel vehicle are unchanged, and the influence caused by the altitude change can be ignored, the tunnel smoke flow is a function of the tunnel length and the comprehensive influence factor;
(II) applying the formulas (9) and (10), the soot concentration of the upstream air flow passing through the upstream tunnel is calculated by the formula (11):
in the formula, delta 1 is the smoke concentration of the upstream air flow, and m-1; l1 is the length of the upstream tunnel, m; qr is the flow rate of external fresh air introduced from the tunnel inlet, m 3/s;
(III) the fractional wind ratio is determined by equation (12):
in the formula: e is a fractional wind ratio number and a dimensionless number; q is the air flow rate of the air which is divided to the induced draft section of the circulating air duct, and m 3/s;
according to the mass conservation principle, the wind amount calculation formula of the parallel wind flow of the short tunnel channel is as follows (13):
Q＝(1-e)·Q (13)；
in the formula, Qs is the air volume of the parallel air flow of the short tunnel, and m 3/s;
because the unpurified circulating air flow Q eta flowing into the dust remover is the air flow Q divided to the induced air section of the circulating air duct, in the formula (12), Q eta is replaced by Q, and the formula (12) is deformed, so that the calculation formula of the unpurified circulating air flow Q flowing into the dust remover is obtained as the formula (2):
Q＝e·Q (2)；
(IV) the method for calculating the smoke concentration of the parallel air flow of the short tunnel comprises the following steps:
the smoke flow of the parallel wind flow comes from two parts, wherein in the first part, the smoke flow carried by the upstream wind flow; secondly, the flow of smoke and dust generated by the emission of vehicles running in the short tunnel;
the flow of the smoke carried by the upstream air flow influencing the flow of the smoke of the parallel air flow is calculated as the following formula (14):
Q＝δQ (14)；
where Qs1(VI) is the soot flow rate from the upstream stream, m 2/s;
substituting formula (13) for formula (14) to give formula (15):
Q＝δ(1-e)Q (15)；
in addition, the flow rate of the smoke generated by the emission of the vehicle running in the short tunnel road is calculated as the following formula (16):
Q＝C·L (16)；
In the formula, Qs2(VI) is the newly added smoke flow in the parallel wind flow of the short tunnel, m 2/s; ls is the length of the tunnel short track, m;
according to the basic principle of physics, applying the formula (15), the formula (16) and the formula (13) to obtain the smoke concentration of the parallel wind flow of the tunnel short channel, and calculating the smoke concentration as the formula (17):
in the formula, delta 2 is the smoke concentration of the parallel wind flow, and m-1;
(V) determining the effective air volume coefficient of the dust remover:
in order to characterize the effect of the smoke concentration of the circulating air flow on the performance and the limit utilization of the dust remover, the effective air quantity coefficient of the dust remover is defined as the ratio of the smoke concentration of the unpurified circulating air flow flowing into the dust remover, namely the smoke concentration of the upstream air flow to the smoke allowable concentration of the ventilation design, namely the formula (18) shows:
in the formula, omega is the effective air quantity coefficient of the dust remover and has no dimensional number; δ 1 is the smoke concentration of the upstream air stream; delta is the allowable concentration of smoke dust in the tunnel ventilation design, m-1;
(VI) determining the critical smoke concentration of the upstream air flow and the critical effective air volume coefficient of the dust remover:
on the premise of meeting the ventilation design requirement, when δ 2 is δ, applying and deforming equation (17), and replacing δ 1 with δ 1c to obtain the critical smoke concentration calculation equation of the upstream wind flow as equation (4):
in the formula, delta 1c is the critical smoke concentration of the upstream air flow of the upstream tunnel, and m-1;
in the formula (18), replacing δ 1 with δ 1c and replacing ω with ω c, the calculation formula of the critical effective air volume coefficient of the dust remover is obtained as the formula (3):
in the formula, omega c is the critical effective air quantity coefficient of the dust remover and has no dimensional number.
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