CN106594971A - Method for controlling minimum air volume of mechanical ventilation system in cavern - Google Patents

Abstract

The invention discloses a method for controlling the minimum air volume of a mechanical ventilation system in a cavern. The method comprises the following steps: (1) acquiring parameters; (2) calculating the pressure difference value delta P1 between the inner and outer sides of the cavern in an opening state; (3) calculating the flow coefficient c; (4) calculating the minimum air leakage rate Q1 of the cavern under the action of mechanical air supply, and then calculating the pressure difference value delta P2 between the inner and outer sides of the cavern at the moment; and (5) calculating the pressure value delta P3 provided by a mechanical air supply system, calculating the air supply volume Q2 required by the mechanical ventilation system through delta P3 and c, and determining the air exhaust volume Q3 required by the mechanical ventilation system according to the air volume balance, wherein the mechanical ventilation system is controlled by a pressure sensor in the cavern to control the system air supply and exhaust volume according to the air supply volume Q2 and the air exhaust volume Q3, and thus the pressure difference value between the inner and outer sides of the cavern is kept at delta P3. According to the method disclosed by the invention, the mechanical ventilation system is additionally arranged for the cavern. Through the control over the system air supply and exhaust volume as well as the static pressure in the cavern, a micro-positive pressure state of the cavern can be formed, high-humidity air in the atmosphere can be prevented from diffusing towards the cavern, and a stable humidity environment can be provided for cultural relics in the cavern during rain.

Description

The minimum air quantity control method of mechanical ventilation system in grottoes

Technical field

The invention belongs to field of heating ventilation air conditioning, and in particular to a kind of control method of mechanical ventilation system minimum air quantity.

Background technology

In recent years the weather in Dunhuang is varied from, and heavy showers phenomenon in a short time occurs.Heavy showers weather is to when earth polar arid Desert climate brings greatly impact, and in a short time relative air humidity value steeply rises.Relative humidity highest is close to outside cave 100%, relative humidity is up to 80% in cave, holds layer deliquescence of interior part crystal salt with reaching Mogao Grottoes grottoes mural painting wet Degree.Relative humidity stability is broken in grottoes, causes grottoes precipice body moisture and salt regime, accelerates mural painting disease process.At present, prevent Air highly humid air to the method that grottoes permeate mainly closes cave door, stops reception visitor.But, due to Mogao Grottoes historical relic Particular/special requirement, must leave ventilating blind window on the door of cave, even if causing grottoes to close cave door, its air-tightness is poor, still can not Stop that highly humid air permeates to grottoes.Zhang Zhengmo et al. is carried out to relative humidity in the 85th cave cave after the daily rain amount of July 15 in 2012 Test observation, the 85th cave belongs to non-opening grottoes, finds at relative humidity noon 12 on the 16th or so to rise to 62%, reaches Relative humidity early warning value (62%) in Dunhuang Research Inst.'s regulation cave.It can be seen that closing the door to the effect for preventing highly humid air from spreading to grottoes It is unsatisfactory.Set up mechanical ventilation system for grottoes, by control give, exhaust air rate, make grottoes form stable pressure-fired, can be effective Highly humid air outside cave is prevented to spread to grottoes；Meanwhile, static pressure fluctuation is possible to destroy humid air or liquid in grottoes wall body in cave The migration balance of water, the water translocation in wall body has driven the migration of salinity, so as to activate mural painting salt damage, therefore, static pressure in cave Can not be excessive.The force ventilation for forming pressure-fired in cave is sent, air draft quantifier elimination is for preventing outside cave highly humid air to hole Permeate in cave most important.But, do not have the machinery with anti-steam infiltration as purpose of design in current HVAC industry and lead to Wind system send, air draft method for determination of amount, and the research of current HVAC industry lacks indoor static pressure and hands over indoor and outdoor air Relation research between the amount of changing, also lacks the relation research of accurate air output and indoor static pressure, it is thus determined that preventing high humidity outside cave Static pressure in cave required for air penetration, and determine suitable supply and exhaust value, it is the key issue for needing to solve at present.

The content of the invention

The purpose of patent of the present invention is the minimum air quantity control method for providing mechanical ventilation system in a kind of grottoes, to solve Certainly above-mentioned technical problem.The present invention exchanges the present situation for causing that relative humidity increases in cave for cave inner air and outer air, is that grottoes are set up Mechanical ventilation system, is sent, exhaust air rate by control system, static pressure in control grottoes so as to form stable slight positive pressure state, support Air highly humid air processed spreads from door and window gap to grottoes, and a stable wet ring is provided for the historical relic in cave in flush period Border, is conducive to the protection of historical relic.

To achieve these goals, the present invention is adopted the following technical scheme that：

The minimum air quantity control method of mechanical ventilation system, comprises the following steps in grottoes：

1) grottoes internal and external temperature is gathered, calculates grottoes inside and outside temperature difference Δ T；Wind speed, wind direction outside collection cave；Collection grottoes enter Depth and grottoes height；The active force for judging to be divulged information in grottoes by the parameter for gathering；

2) according to step 1) in the active force of ventilation that obtains, calculate natural ventilating status lower opening cave inside and outside differential pressure value ΔP₁；

3) according to cave inside and outside differential pressure value Δ P under open state₁Calculated flow rate coefficient c；

4) the lower grottoes minimum inleakage of calculating machine air-supply effect is Q₁, then calculate now grottoes inside and outside differential pressure Δ P₂；

5) the pressure value Δ P that calculating machine supply air system is provided₃, the pressure value that emchanical air supply system is provided is equal to grottoes door The pressure absolute value that the pressure value of both sides is produced plus hot pressing, Action of Wind pressure：

ΔP₃=Δ P₂+|ΔP₁| (13)

By Δ P₃The air quantity Q for determining that mechanical ventilation system needs output is calculated with c₂；Control machinery ventilating system is according to meter The air quantity Q of calculation₂Control system minimum supply air rate, when cave inner air pressure presses Δ P more than outside atmosphere₃When, exhaust blower is opened, its Exhaust air rate is air output Q₂With inleakage Q₁Difference Q₃, air balance is now formed in cave, pressure no longer increases in cave, makes cave It is interior to form stable pressure-fired environment.

According to air balance principle, air output Q₂With inleakage Q₁Difference Q₃For the exhaust air rate of grottoes, made in grottoes with this Form stable pressure environment.

Further, step 1) in by the active force of ventilation in grottoes by formula (3) calculating：

Wherein：

Re- Reynolds numbers；

Big gas velocity, m/s outside u- caves；

The viscosity of ν-air, m²/s；

L- grottoes depth, m；

Gr- grashof numbers；

G- acceleration of gravitys；

Δ T- grottoes internal-external temperature differences, DEG C；

H- grottoes height, m.

Further, whenWhen, cave inside and outside differential pressure value Δ P under open state is calculated by formula (6)₁；

Wherein, ρ-atmospheric density, kg/m³；Mean temperature in-grottoes, DEG C；

WhenWhen, if the outer wind direction of grottoes blows to grottoes, calculated under open state by formula (7) Cave inside and outside differential pressure value Δ P₁；If during the parallel cave door of the outer wind direction of grottoes, by formula (8) cave inside and outside differential pressure under open state is calculated Value Δ P₁；

Further, step 3) according to formula (9) calculated flow rate coefficient：

In formula：

C- discharge coefficients, m³/(s·Pa^b)；

C_DThe air exchange coefficient of-grottoes opening, dimensionless；

A_effThe effective vent area of-grottoes, m²；

N- flow indexs, value is between 0.5～1.

Further, step 4) specifically include：

Q₁=u × A_eff (10)

In formula：

Q₁- can resist air outside cave to grottoes permeate by minimum inleakage, m at the door opening of cave³/s；

Q₁=c Δ P₂ ⁿ (11)

In formula：

ΔP₂- ensure Q₁Cave inside and outside differential pressure, Pa.

Further, step 5) in by formula (14) calculating machine ventilating system need output air quantity Q₂：

Q₂=c Δ P₃ ⁿ (14)

By the exhaust air rate Q of formula (15) calculating machine ventilating system₃：

Q₃=Q₂-Q₁ (15)。

Relative to prior art, the invention has the advantages that：The present invention is exchanged for cave inner air and outer air and causes cave The present situation that interior relative humidity increases, is that grottoes set up mechanical ventilation system, is sent by control system, exhaust air rate, in control grottoes Static pressure so as to form stable slight positive pressure state, resists air highly humid air and spreads to grottoes, is the historical relic in cave in flush period One stable wet environment is provided, is conducive to the protection of historical relic.

Specific embodiment

The invention provides the air quantity control method of mechanical ventilation system in the grottoes of purpose of design is diffused as with anti-steam, At least to solve effectively provide grottoes static pressure and system institute in grottoes under mechanical ventilation system effect in correlation technique Need to give, the problem of exhaust air rate.

1st, the determination methods of grottoes gravity-flow ventilation driving force.

Grottoes inside and outside differential pressure is very micro value under natural ventilating status, it is difficult to tested.Can be by judgingClearly draw Play the driving force that grottoes inner air and outer air is exchanged, the test value difference of wind speed, wind direction according to the temperature difference inside and outside grottoes and cave area Using the theoretical formula method grottoes inner air and outer air pressure reduction of the grottoes inside and outside differential pressure under hot pressing function, blast hot pressing comprehensive function. However, it is desirable to it is clear that, the value calculated using formula is the cave inside and outside differential pressure of big opening.

UtilizeJudge the active force of ventilation in grottoes.Wherein R_e(Reynolds number) represents the ratio of inertia force and viscous force, G_rInclude in (grashof number) number the contrast parameter of the ratio of buoyancy lift and viscous force, inertia force and buoyancy lift byTable Show.WhenWhen, can regard that buoyancy lift accounts for the ventilation of mastery reaction, i.e. single-open and meets Ventilation rule as, The impact of blast is not considered；WhenWhen, inertia force and buoyancy lift collective effect, i.e. single-open can be regarded as Ventilation meets blast, hot pressing collective effect ventilation rule；WhenWhen, inertia force can be regarded as account for mastery reaction, i.e. one side and open Mouthful ventilation meet Action of Wind pressure ventilation rule, but this kind of situation air wind speed cave outside that mostly occurs is more than in the case of 10m/s, base Originally such situation can not be considered.

Wherein：

In formula：

Re- Reynolds numbers (sign flow patterns)

Big gas velocity, m/s outside u- caves；

The viscosity of ν-air, m²/s；

L- grottoes depth, m.

In formula：

Gr- grashof numbers (characterize the size of free convection)；

G- acceleration of gravitys；

Δ T- grottoes internal-external temperature differences, DEG C；

H- grottoes height, m.

2nd, grottoes grottoes inside and outside differential pressure Δ P under different ventilation law effects₁Determination method.

2.1st, whenWhen, grottoes inner air and outer air exchanges the unilateral ventilation of big opening that flowing meets under hot pressing function, Its flowing law meets Bernoulli equation (4) and Warren formula (5)：

In formula：

Q- grottoes inner air and outer air exchange capacities, m³/s；

C_DThe air exchange coefficient of-grottoes opening, dimensionless, its value takes 1；

A_effThe effective vent area of-grottoes, m²；

Δ P- grottoes inside and outside differential pressures, Pa；

ρ-atmospheric density, kg/m³；

In formula：

Q_stack- grottoes inner air and outer air the exchange capacity caused by hot pressing, m³/s；

A_effThe effective vent area of-grottoes, m²；

The H- door upper and lower opening discrepancy in elevation, m；

Δ T-grottoes internal-external temperature difference, DEG C；

Mean temperature in-grottoes, DEG C.

Contrast Warren formula and bernoulli formula, can obtainWhen grottoes inside and outside differential pressure coincidence formula 6 It is described：

In formula：

ΔP₁The lower grottoes inside and outside differential pressure of-gravity-flow ventilation effect, Pa.

2.2nd, whenWhen, according to wind speed, wind direction outside cave internal-external temperature difference and cave, determine grottoes inside and outside differential pressure：

2.2.1, outside cave wind direction for just aweather when：The cave inside and outside differential pressure that just aweather causing with hot pressing collective effect, grottoes are cold Relational expression outside wall and the cave external environment temperature difference, cave between three variables of wind speed：

2.2.2 when, wind direction is Parallel airflow outside cave：Parallel airflow is cold with cave inside and outside differential pressure, grottoes that hot pressing collective effect causes Relational expression outside wall and the cave external environment temperature difference temperature difference, cave between three variables of wind speed：

3rd, the determination method of grottoes cave inside and outside differential pressure under gravity-flow ventilation driving force effect and under the influence of the door air-tightness of cave.

It is effective air penetration area by architectural openings and gap conversion, with the index air-tightness of grottoes is weighed.When When cave door is closed, grottoes inner air and outer air is only swapped by the ventilation shutter on the door of cave, and air hinders through the flowing of opening Power increases, and causes cave inside and outside differential pressure to reduce, and needs to consider cave door air-tightness so that it is determined that cave inside and outside differential pressure.Reflect theoretical upper body On present 9.Understand the discharge coefficient c of air permeation characteristics equation with effective air penetration area of cave door and driving by formula 9 The cave inside and outside differential pressure that power causes is determined.

In formula：

C- discharge coefficients, m³/(s·Pa^b)；

N- flow indexs, relevant with flow velocity, flow regime, value is between 0.5～1.

4th, the air quantity control method of mechanical ventilation system.

(when having gas from grottoes outwardly, and its speed u of leaking out all the time not less than 0.5m/s by cave crack between a door and its frame gap When, can effectively prevent air outside cave from permeating to grottoes, according to the air velocity and the available ventilation area A of cave door_eff, calculate At this moment grottoes minimum inleakage is Q₁(formula 10), using formula 11 now cave inside and outside differential pressure Δ P is can be calculated₂。

Q₁=u × A_eff (10)

In formula：

Q₁- can resist air outside cave to grottoes permeate by minimum inleakage, m at the door opening of cave³/s。

Q₁=c Δ P₂ ⁿ (11)

In formula：

ΔP₂- ensure Q₁Cave inside and outside differential pressure, Pa.

After grottoes are additionally arranged mechanical ventilation system, grottoes inside is produced with the pressure reduction of environment by three kinds of different effects, The pressure head Δ P that hot pressing, blast and mechanical fan are produced₃, it is shown below：

ΔP₂=Δ P₁+ΔP₃ (12)

In formula：

ΔP₃The cave inside and outside differential pressure that-mechanical fan is produced, Pa.

Pressure value (the Δ P that then emchanical air supply system is provided₃) it is equal to pressure value (the Δ P of door both sides₂) deduct hot pressing, blast Pressure value (the Δ P that effect is produced₁).The Δ P wherein under gravity-flow ventilation effect₁Have on the occasion of also there is a negative value, and the purpose of force ventilation It is to make the interior static pressure everywhere of grottoes be all higher than atmospheric pressure, therefore Δ P herein₁Take negative value.I.e.

ΔP₃=Δ P₂+|ΔP₁| (13)

By Δ P₃, c substitute into formula 14 can determine that mechanical ventilation system need output air quantity Q₂：

Q₂=c Δ P₃ ⁿ (14)

In formula：

Q₂- mechanical ventilation system needs the air quantity of output, m³/s。

When pressure increases to design load in cave, if continuing air of the conveying more than inleakage into cave, it will cause in cave Air pressure continues to increase, it is therefore desirable to open exhaust equipment, and air output is equal to the summation of inleakage and exhaust air rate in cave, makes shape in cave Into stable air pressure environment.

The now exhaust air rate Q of mechanical ventilation system₃：

Q₃=Q₂-Q₁ (15)

The method for designing of mechanical ventilation system air quantity of the invention includes：Clearly cause Mogao Grottoes grottoes gravity-flow ventilation Driving force, calculate cave inside and outside differential pressure value Δ P under the open state caused by the driving force₁；According to gap leak out speed and The static pressure required in cave calculates the pressure difference Δ P needed inside and outside cave₂；ΔP₂With | Δ P₁| summation be mechanical ventilation system The pressure value Δ P for providing is provided₃, the air quantity that mechanical ventilation system needs can determine that with this.

The air quantity control method of mechanical ventilation system, comprises the following steps in a kind of grottoes of the present invention：

1) grottoes internal and external temperature is gathered, calculates grottoes inside and outside temperature difference Δ T；Wind speed, wind direction outside collection cave；Collection grottoes enter Depth and grottoes height；The active force of ventilation in grottoes is judged by formula (3)；

If 2)Cave inside and outside differential pressure value Δ P under open state is calculated by formula (6)₁；IfWhen the outer wind direction of its grottoes blows to grottoes, cave inside and outside differential pressure value Δ P under open state is calculated by formula 7₁, During the parallel cave door of the outer wind direction of its grottoes, cave inside and outside differential pressure value Δ P under open state is calculated by formula (8)₁；

3) by formula (9) calculated flow rate coefficient c；

4) the lower grottoes minimum inleakage of calculating machine air-supply effect is Q₁, using formula (11) external pressure in now cave is calculated Difference Δ P₂；

5) the pressure value Δ P that calculating machine supply air system is provided₃, the pressure value that emchanical air supply system is provided is equal to grottoes door The pressure absolute value that the pressure value of both sides is produced plus hot pressing, Action of Wind pressure：

ΔP₃=Δ P₂+|ΔP₁| (13)

By Δ P₃, c substitute into formula (14) calculate determine mechanical ventilation system need output air quantity Q₂；Control machinery air-supply system Unite according to the air quantity Q for calculating₂Control system air output, when pressure reaches design load in cave, while exhaust system is opened, according to The air quantity Q of calculating₃Control system exhaust air rate, makes the pressure differential inside and outside grottoes be maintained Δ P₃, can effectively prevent outside grottoes Highly humid air is penetrated in grottoes.

Claims (6)

1. in grottoes mechanical ventilation system minimum air quantity control method, it is characterised in that comprise the following steps：

1) grottoes internal and external temperature is gathered, calculates grottoes inside and outside temperature difference Δ T；Wind speed, wind direction outside collection cave；Collection grottoes height and Depth；The active force for judging to be divulged information in grottoes by the parameter for gathering；

2) according to step 1) in obtain ventilation active force, calculate open state under cave inside and outside differential pressure value Δ P₁；

3) according to cave inside and outside differential pressure value Δ P under open state₁Calculated flow rate coefficient c；

4) the lower grottoes minimum inleakage of calculating machine air-supply effect is Q₁, then calculate now grottoes inside and outside differential pressure Δ P₂；

5) the pressure value Δ P that calculating machine supply air system is provided₃, the pressure value that emchanical air supply system is provided is equal to grottoes door both sides Pressure value plus hot pressing, Action of Wind pressure produce pressure absolute value：

ΔP₃=Δ P₂+|ΔP₁| (13)

By Δ P₃The air quantity Q for determining that mechanical ventilation system needs output is calculated with c₂；Control machinery ventilating system is according to calculating Air quantity Q₂Control system minimum supply air rate, Δ P is pressed to cave inner air pressure more than outside atmosphere₃When, open exhaust blower, its air draft Measure as air output Q₂With inleakage Q₁Difference Q₃, air balance is now formed in cave, pressure no longer increases in cave, makes shape in cave Into stable pressure-fired environment.

2. in grottoes according to claim 1 mechanical ventilation system minimum air quantity control method, it is characterised in that step 1) calculated by formula (3) by the active force of ventilation in grottoes in：

$\frac{{\mathrm{Re}}^2}{Gr}=\frac{u^2}{g\mathrm{\Δ}T}\·\frac{L^2}{H^3}---\left(3\right)$

Wherein：

Re- Reynolds numbers；

U- caves outer air flow speed, m/s；

The viscosity of ν-air, m²/s；

L- grottoes depth, m；

Gr- grashof numbers；

G- acceleration of gravitys；

Δ T- grottoes internal-external temperature differences, DEG C；

H- grottoes height, m.

3. in grottoes according to claim 2 mechanical ventilation system air quantity control method, it is characterised in that

WhenWhen, cave inside and outside differential pressure value Δ P under open state is calculated by formula (6)₁；

${\mathrm{\ΔP}}_1=\frac{gH\mathrm{\ρ}\mathrm{\Δ}T}{18{\stackrel{\‾}{T}}_{ave}}---\left(6\right)$

Wherein, ρ-atmospheric density, kg/m³；Mean temperature in-grottoes, DEG C；

WhenWhen, if the outer wind direction of grottoes blows to grottoes, by cave under formula (7) calculating open state External pressure difference DELTA P₁；If during the parallel cave door of the outer wind direction of grottoes, by formula (8) cave inside and outside differential pressure value Δ under open state is calculated P₁；

$\left\{\begin{array}{cc}u\≤3m/s& \left|{\mathrm{\ΔP}}_1\right|=0.2u^2-0.56u+0.015\mathrm{\Δ}T+0.77\\ u>3m/s& \left|{\mathrm{\ΔP}}_1\right|=0.1u^2+0.37u-0.27\mathrm{\Δ}T-1.62\end{array}\right.---\left(7\right)$

$\{\begin{array}{cc}u\≤2m/s& \left|{\mathrm{\ΔP}}_1\right|=0.18u^2-0.48u-0.002\mathrm{\Δ}T+0.3\\ u>2m/s& \left|{\mathrm{\ΔP}}_1\right|=0.025u^2+0.25u-0.009\mathrm{\Δ}T-0.64\end{array}---\left(8\right)$

4. in grottoes according to claim 3 mechanical ventilation system air quantity control method, it is characterised in that step 3) in According to formula (9) calculated flow rate coefficient：

$c=C_D{A}_{eff}\sqrt{\frac{2}{\mathrm{\ρ}}}{\left(\right|{\mathrm{\ΔP}}_1\left|\right)}^{0.5-n}---\left(9\right)$

In formula：

C- discharge coefficients, m³/(s·Pa^b)；

C_DThe air exchange coefficient of-grottoes opening, dimensionless；

A_effThe effective vent area of-grottoes, m²；

N- flow indexs, value is between 0.5～1.

5. in grottoes according to claim 4 mechanical ventilation system air quantity control method, it is characterised in that step 4) tool Body includes：

Q₁=u × A_eff (10)

In formula：

Q₁- can resist air outside cave to grottoes permeate by minimum inleakage, m at the door opening of cave³/s；

Q₁=c Δ P₂ ⁿ (11)

In formula：

ΔP₂- ensure Q₁Cave inside and outside differential pressure, Pa.

6. in grottoes according to claim 5 mechanical ventilation system air quantity control method, it is characterised in that step 5) in The air output Q needed by formula (14) calculating machine ventilating system₂：

Q₂=c Δ P₃ ⁿ (14)

The exhaust air rate Q needed by formula (15) calculating machine ventilating system₃：

Q₃=Q₂-Q₁ (15)。