CN101726338A - Method for measuring nozzle flow characteristic of inert gas fire-extinguishing system - Google Patents

Abstract

The invention relates to a method for measuring the flow characteristic of a nozzle of an inert gas fire-extinguishing system. The method comprises the following steps: (1) arranging a static pressure, dynamic pressure or total pressure sensor and a temperature sensor on the same section of the upstream pipe of the nozzle to measure the static pressure, dynamic pressure or total pressure and the temperature; (2) measuring and calculating the sectional area of the pipe and the area of the nozzle exit at the pressure-measuring point; (3) substituting the measured static pressure, dynamic pressure or total pressure, the temperature, the sectional area of the pipe and the area of the nozzle exit into the flow calculation formula of the extrusive gas of the nozzle to calculate the Q value; (4) substituting the flow Q value into the spraying rate calculation formula to calculate the phi value; and (5) adopitng the spraying rates of the nozzle at different spraying static pressures to draw a flow characteristic curve through a data processing method. By using the method of the invention, the measuring device and measuring procedure of the flow characteristic of the nozzle in the inert gas fire-extinguishing system are simplified, the measuring time is shortened, the work efficiency of the measurement is increased, the mechanical error generated in the measuring process is avoided, and the measuring precision is increased.

Description

The measuring method of nozzle flow characteristic of inert gas fire-extinguishing system

Technical field

The present invention relates to measure the method for inert gas fire-fighting system, particularly a kind of measuring method of nozzle flow characteristic of inert gas fire-extinguishing system.

Background technology

Nozzle flow characteristic of inert gas fire-extinguishing system is to describe nozzle relation between gas spraying rate and the nozzle static pressure in course of injection.At present, the measurement of nozzle flow characteristic mainly is the discharge characteristic that the mass change amount of inert gas in static pressure by the gaging nozzle porch and the steel cylinder is calculated nozzle.Use this method, mainly measure two parameters, the one, the static pressure of gaging nozzle porch, another is by the gaseous mass in the weight method measurement steel cylinder, thereby obtains the quality of nozzle ejection gas, solves mass rate by the mass change amount again.Because it is the astable flow condition of a kind of high-voltage high-speed that inert gas fire-fighting system sprays, to use this method and measure quality, there is relative hysteresis quality in measuring process, and measuring accuracy exists not enough.

Weight method is measured the principle of the gas flow in the steel cylinder: after starting the fire-extinguishing bottle on the weighing platform, the fire-extinguishing bottle container value is unlocked, and gas extinguishing agent flows to nozzle by connecting tube, is discharged in the guard space again.After fire extinguishing agent sprays from steel cylinder, the quality of fire extinguishing agent changes in the steel cylinder, the weighing platform that is in equilibrium state when initial is no longer kept original equilibrium state, along with constantly spurting of extinguishing medium, balancer one end constantly sinks, and the quality signal that load sensor will spurt fire extinguishing agent is transferred to computing machine.The pressure transducer that install at the nozzle place also is transferred to computing machine with gas at ducted pressure signal, and computing machine is handled the qualitative data and the pressure data that collect, gets the flow curve of delivery nozzle.But because the existence of transfer pipeline, the data of load sensor and pressure transducer collection have asynchronism, so there is relative hysteresis quality in data.Because the data of two sensor measurements are not instantaneous synchrodatas, therefore, the precision of measurement result also is subjected to corresponding influence, and measurement mechanism and process of measurement are comparatively complicated simultaneously.

Summary of the invention

In order to overcome the deficiency of existing measuring method, the invention provides a kind of method of new measurement nozzle flow characteristic of inert gas fire-extinguishing system, this method will change into by the nozzle ejection flow that weight method obtains by measuring channel static pressure, dynamic pressure (or stagnation pressure) and temperature value, and obtain nozzle flow, and then calculate the spraying rate of nozzle by the computing formula of deriving.Not only simplify measurement mechanism, and improved measuring accuracy.

The measuring method of nozzle flow characteristic of inert gas fire-extinguishing system is characterized in that: comprise the steps:

(1), static pressure, dynamic pressure or total-pressure probe and temperature sensor are installed in the same cross section of nozzle upstream pipeline, measure static pressure, dynamic pressure or stagnation pressure and the temperature value at this place, sectional position;

(2), measure the long-pending and exit area of nozzle of calculating pressure tap pipeline section;

(3), static pressure, dynamic pressure or stagnation pressure value, temperature value, the pressure tap pipeline section of measuring amassed the flow rate calculation formula of value and exit area of nozzle value substitution nozzle ejection gas:

$Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s\·P_d}{\mathrm{RT}}}$ 1. or $Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s(P_0-P_s)}{\mathrm{RT}}}$ ②

Calculate the Q value; Wherein: Q---the mass rate kg/s of nozzle ejection gas; A ₀---nozzle pressure tap pipeline section area m ²A ₁---exit area of nozzle m ²P _s---the static pressure Pa that the same section gas of measurement point sprays; P _d---the dynamic pressure Pa that the same section gas of measurement point sprays; P ₀---the general pressure Pa that the same section gas of measurement point sprays; T---the same section gas of measurement point adiabatic temperature K; R---ideal gas constant J/ (molK);

(4), with the flow Q value of the nozzle that the calculates ejection gas spraying rate computing formula of substitution nozzle again:

$\mathrm{\Φ}=\frac{Q}{A_1}$ ③

Calculate the φ value; Wherein: φ---the spraying rate kg/ (sm of nozzle ²);

(5), by data processing method the spraying rate that nozzle sprays under the static pressure in difference is depicted as rating curve.

The beneficial effect that the present invention produced is: adopt this method, simplify the measurement mechanism and the process of measurement of nozzle flow characteristic of inert gas fire-extinguishing system, shortened Measuring Time, improved surveying work efficient, avoided simultaneously in measuring process, producing machine error, improved measuring accuracy.

Embodiment

Below the invention will be further described: a kind of measuring method of nozzle flow characteristic of inert gas fire-extinguishing system comprises the steps:

(1), static pressure, dynamic pressure or total-pressure probe and temperature sensor are installed in the same cross section of nozzle upstream pipeline, measure static pressure, dynamic pressure or stagnation pressure and the temperature value at this place, sectional position;

(2), measure the long-pending and exit area of nozzle of calculating pressure tap pipeline section;

(3), static pressure, dynamic pressure or stagnation pressure value, temperature value, the pressure tap pipeline section of measuring amassed the flow rate calculation formula of value and exit area of nozzle value substitution nozzle ejection gas:

$Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s\·P_d}{\mathrm{RT}}}$ 1. or $Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s(P_0-P_s)}{\mathrm{RT}}}$ ②

Calculate the Q value; 1. formula is used to adopt static pressure, dynamic pressure transducer to measure calculating; 2. formula is used to adopt static pressure, total-pressure probe to measure calculating; Wherein: Q---the flow kg/s of nozzle ejection gas; A ₀---nozzle pressure tap pipeline section area m ²A ₁---exit area of nozzle m ²P _s---the static pressure Pa that the same section gas of measurement point sprays; Pd---the dynamic pressure Pa that the same section gas of measurement point sprays; P ₀---the general pressure Pa that the same section gas of measurement point sprays; T---the same section gas of measurement point adiabatic temperature K; R---ideal gas constant J/ (molK);

(4), with the flow Q value of the nozzle that the calculates ejection gas spraying rate computing formula of substitution nozzle again:

$\mathrm{\Φ}=\frac{Q}{A_1}$ ③

Calculate the φ value; Wherein: φ---the spraying rate kg/ (sm of nozzle ²);

(5), the φ value that goes out of known calculations and the static pressure Ps value of measuring the same section gas of nozzle, can find out nozzle at the different static pressure P that spray of gas _sDown, the spraying rates of nozzle under the different injection of gas static pressure are depicted as rating curve by data processing method with the relation of spraying rate φ.

The flow rate calculation formula of nozzle ejection gas 1. 2. derivation is as follows:

Computing formula according to the inert gas fire-fighting system nozzle orifice coefficient:

$G=\frac{Q}{A_1\·\sqrt{2\mathrm{\ρ}{P}_s}}---\left(1\right)$

Wherein: G---nozzle orifice coefficient; Q---the flow kg/s of nozzle ejection gas; A ₁---exit area of nozzle m ²ρ---nozzle pressure tap gas density kg/m ³Ps---nozzle measurement point gas-static power Pa;

Q=ρ uA in the known formula ₀(2)

Wherein: u---nozzle measurement point gas flow speed m/s; A ₀---nozzle measurement point pipeline section area m ²With formula (2) substitution formula (1):

$G=\frac{Q}{A_1\·\sqrt{2\mathrm{\ρ}{P}_s}}=\frac{\mathrm{\ρ}\·u\·A_0}{A_1\sqrt{2\mathrm{\ρ}\·P_s}}=\frac{A_0}{A_1}\·\sqrt{\frac{1/2\·\mathrm{\ρ}\·u^2}{P_s}}---\left(3\right)$

In the formula (3), known

Dynamic pressure P for the same section gas of measurement point _dTherefore, formula (3) is reduced to:

$G=\frac{A_0}{A_1}\·\sqrt{\frac{1/2\·\mathrm{\ρ}\·u^2}{P_s}}=\frac{A_0}{A_1}\·\sqrt{\frac{P_d}{P_s}}---\left(4\right)$

Again because of P _d+ P _s=P ₀, P ₀Be the general pressure of the same section gas of measurement point, formula (4) can also be deformed into:

$G=\frac{A_0}{A_1}\·\sqrt{\frac{P_d}{P_s}}=\frac{A_0}{A_1}\·\sqrt{\frac{P_0-P_s}{P_s}}=\frac{A_0}{A_1}\·\sqrt{\frac{P_0}{P_s}-1}---\left(5\right)$

By formula (5) as can be seen, only need gas stagnation pressure P in the gaging nozzle upstream line ₀, static pressure P _s, pressure tap pipeline section area A ₀With exit area of nozzle A ₁Can calculate nozzle orifice coefficient.

By formula (1) distortion can be got: $Q=G\·A\·\sqrt{2\mathrm{\ρ}\·P_s}---\left(6\right)$

Again because of The Ideal-Gas Equation: P _s=ρ RT (7)

Wherein: R---ideal gas constant, R=8.31, J/ (molK); T---gas adiabatic temperature, K.

In formula (7) substitution formula (6), can get:

$Q=G\·A\·P_s\sqrt{\frac{2}{\mathrm{RT}}}---\left(8\right)$

In formula (5) substitution formula (8), can get:

$Q=G\·A\·P_s\sqrt{\frac{2}{\mathrm{RT}}}=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s\·P_d}{\mathrm{RT}}}=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s(P_0-P_s)}{\mathrm{RT}}}---\left(9\right)$

Formula (9) is 1. 2. the former formula of flow rate calculation formula of the nozzle ejection gas in this method step (3).By formula (9) as can be known, measure the static pressure P at nozzle entrance place _s, general pressure P ₀Or dynamic pressure P _d, gas temperature T, nozzle pressure tap pipeline section area A ₀, exit area of nozzle A ₁, just can calculate the flow Q that nozzle sprays gas, again by flow Q, just can solve the spraying rate φ of nozzle, as shown in Equation (10).

$\mathrm{\Φ}=\frac{Q}{A_1}$ (10)

Wherein: φ---the spraying rate of nozzle, kg/ (sm ²).

The discharge characteristic of nozzle is described nozzle exactly at different expulsion pressure P _sDown and the relation of spraying rate φ.By data processing method nozzle is depicted as a curve at the spraying rate under the different pressures, this curve is referred to as rating curve.

Therefore, the measuring method of the nozzle flow characteristic of inert gas fire-extinguishing system that proposes among the present invention is: adopt response is fast, precision is high static pressure, dynamic pressure (or stagnation pressure) sensor and temperature sensor, be installed in the same cross section of nozzle upstream pipeline, measure static pressure, dynamic pressure (or stagnation pressure) and the temperature value of this section.In addition, also to measure the long-pending and exit area of nozzle of pressure tap pipeline section.Calculate the nozzle flow and the nozzle ejection rate of the coefficient of flow of inert gas fire-fighting system nozzle, corresponding different pipeline pressures by formula (5), formula (9) and formula (10), thereby obtain the nozzle flow characteristic curve of inert gas fire-fighting system.

Claims (1)

1. the measuring method of a nozzle flow characteristic of inert gas fire-extinguishing system is characterized in that: comprise the steps:

(1), static pressure, dynamic pressure or total-pressure probe and temperature sensor are installed in the same cross section of nozzle upstream pipeline, measure static pressure, dynamic pressure or stagnation pressure and the temperature value at this place, sectional position;

(2), measure the long-pending and exit area of nozzle of calculating pressure tap pipeline section;

(3), static pressure, dynamic pressure or stagnation pressure value, temperature value, the pressure tap pipeline section of measuring amassed the flow rate calculation formula of value and exit area of nozzle value substitution nozzle ejection gas:

$Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s\·P_d}{\mathrm{RT}}}$ 1. or $Q=\frac{A_0^2}{A_1}\sqrt{\frac{2P_s(P_0-P_s)}{\mathrm{RT}}}$ ②

Calculate the Q value; Wherein: Q---the mass rate kg/s of nozzle ejection gas;

A ₀---nozzle pressure tap pipeline section area m ²

A ₁---exit area of nozzle m ²

P _s---the static pressure Pa that the same section gas of measurement point sprays;

P _d---the dynamic pressure Pa that the same section gas of measurement point sprays;

P ₀---the general pressure Pa that the same section gas of measurement point sprays;

T---the same section gas of measurement point adiabatic temperature K;

R---ideal gas constant J/ (molK);

(4), with the mass rate Q value of the nozzle that the calculates ejection gas spraying rate computing formula of substitution nozzle again:

$\mathrm{\Φ}=\frac{Q}{A_1}$ ③

Calculate the φ value; Wherein: φ---the spraying rate kg/ (sm of nozzle ²);

(5), by data processing method the spraying rate that nozzle sprays under the static pressure in difference is depicted as rating curve.