JPS62226016A - Differential pressure type flow rate measuring device - Google Patents

Abstract

PURPOSE:To exactly measure a flow rate even if the titled device is applied to a place where there is a temperature difference, by correcting a differential pressure therein, by the fluid temperature of each side of inflow and outflow of a throttle mechanism which has been provided in a passage. CONSTITUTION:Temperature sensors 17, 19 are provided on either side of inflow and outflow of an air heater 3, respectively, and temperatures of air flowing through an air duct 1 are detected and supplied to a temperature correcting part 13. To this correcting part 13, the differential pressure in either side of inflow and outflow of the heater, which has been measured by a differential pressure transmitting device 11, is supplied. In the correcting part 13, the air density of each side of inflow and outflow of the heater is corrected by using a prescribed expression, respectively, by said each temperature which has been detected, and thereafter, brought to evolution operation 15, and an air flow rate is calculated. Accordingly, by considering the temperature of each side of inflow and outflow of the heater 3, each air density is corrected, and a derived air flow rate is supplied to a fuel device. Also, in the fuel device, an air fuel ratio is controlled by adjusting a fuel supply quantity from this air flow rate signal. Therefore, the air fuel ratio becomes an exact value which agrees with a target value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a differential pressure type flow measuring device used for controlling the air-fuel ratio of a boiler.

(Prior Art) In boiler combustion devices and the like, it is necessary to mix and contact combustible gas and fuel blown from a burner with air to ensure sufficient combustion. For this reason, the flow rate of the air is measured using, for example, a differential pressure type flow rate measuring device, and combustion is performed based on an appropriate air-fuel ratio based on the air flow rate.

Additionally, in general, boilers use an air heater (AI-1) that preheats the air in order to improve combustion efficiency, and the differential pressure flow measurement device measures the inflow and outflow sides of the air flowing through this air heater due to the nature of the plant. The airflow ■ is measured using the differential pressure between the sides.

2. Description of the Related Art Conventionally, as a differential pressure type flow mountain measuring device used for boiler air-fuel ratio control, etc., the one shown in FIG. 3 has been known.

In the figure, 1 is an air duct, and an air heater 3 is inserted at a predetermined location of this air duct 1, so that the air flowing through the air duct 1 is preheated.

The preheated air is supplied to a combustion device (not shown) and mixed with fuel.

” 2. Inside the air heater 3 is a ∆ rewiring constriction portion 5 /Jt.
The pressures P+ and P2 on the inflow and outflow sides are g
It is led to a differential pressure transmitter 11 by the three pressure pipes 7 and 9, and by this differential pressure transmitter 11, the inflow side pressure P1 and the outflow side pressure P
The differential pressure between P+ and P2 is determined. The calculated differential pressure PI P2 is supplied to the temperature correction section 13.

The air density T for a fixed temperature (for example, 20° C.) is set in advance in the temperature correction unit 13, and temperature correction is performed using the following equation (1) derived from the Be J. Renoulli theorem.

Here, Q is the left foot of air, and 1< is the coefficient 1g is the acceleration of gravity.

Then, after the temperature is corrected in the temperature correction unit 13 as shown in the double series, the square root calculation unit 15 performs a square root process 11 and the air flow f
f1Q is found. The determined air flow rate Q is output to a fuel system (not shown). The fuel system signs the fuel supply amount from the supplied airflow flQ and controls the air-fuel ratio to an appropriate value.

However, in the conventional differential pressure type flow measuring device described above, although there is a significant difference in air density due to the temperature difference between the inflow side and the outflow side of the air heater 3, the differential pressure between the inflow side and the outflow side PI P2 Since the air flow ωQ flowing through the air duct 1 is calculated uniquely, accurate desire measurement cannot be performed.

(Problems to be Solved by the Invention) As mentioned above, in the conventional differential pressure type flow measuring device applied to a place where there is a temperature difference, there is no correction based on the temperature difference, and it is difficult to accurately measure the air flow rate. Unable to measure camellia. For this reason, for example, when controlling the air-fuel ratio using the determined air flow ff1Q, the actual air-fuel ratio may differ greatly from the target value, resulting in the generation of black smoke due to lack of air, generation of excess heat due to excess air, etc. A problem had occurred.

The present invention is based on the above-mentioned circumstances, and its object is to provide a differential pressure flow rate measuring device that can accurately measure the flow rate of fluid even when applied to locations with temperature differences.

Configuration 1 of the invention C (Means for solving the problems) In order to solve the above problems, the present invention measures the differential pressure between the inflow side and the outflow side of a throttling mechanism provided in a fluid flow path. temperature detection means for detecting the temperature of each fluid on the inflow side and/or the outflow side; and differential pressure correction means for correcting the measured differential pressure based on the detected fluid temperature. The configuration is as follows.

(Use) The differential pressure between the fluid pressure on the inflow side and the fluid pressure on the outflow side of the throttle line groove provided in the fluid is measured by the differential pressure measuring means.

Further, the temperature of each fluid on the inflow side and/or the outflow side of the n orifices is detected by the temperature detection means.

Then, the differential pressure correction means corrects the measured differential pressure based on the detected fluid temperature, and determines the correct flow rate.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of a differential pressure type flow rate measuring device N according to the present invention, and in this embodiment, the present invention is applied to a boiler similarly to the conventional example. Note that the same components as those of the conventional example shown in FIG. 3 are given the same reference numerals, and here,
Only the ¥ character part of the present invention will be explained.

As shown in the figure, in this embodiment, the conventional differential pressure type flow M
In addition to the measuring device, temperature hinges 17 and 19 are provided on the inlet and outlet sides of the air heater 3 to detect the temperatures T+ and T2 of the inlet and outlet air flowing through the air duct 1, respectively.

The detected temperatures T+ and T2 are supplied to the temperature correction section 13. In addition, this temperature correction section 13 includes a differential pressure transmitter 1
The differential pressure P+-P2 between the inflow side and the outflow side of the air heater 3 measured in step 1 is supplied.

The temperature correction unit 13 uses the following equation (2) derived from Bernoulli's theorem to calculate each temperature T1. The inflow side air density γ1 and the outflow side air density γ2 are corrected by T2.

be done. CV is a velocity coefficient, CC is a contraction coefficient, and m is an area ratio a/Δ between the cross section 1a of the orifice constriction portion 5 and the inner area Δ of the air duct 1.

After the temperature is corrected by the temperature correction unit 13 as described above,
A square root calculation is performed in the square root calculation unit 15, and the air flow ff1Q
is calculated.

Therefore, since the air densities γ1 and γ2 are corrected in consideration of the temperature T1 on the inflow side of the air heater 3 and the temperature T2 on the outflow side heated by the air heater 3, the air flow ff1Q determined in this way is corrected. is supplied as a precise signal to a fuel system (not shown).

In the fuel system, the fuel supply port is adjusted based on this air flow rate signal to control the air-fuel ratio. Therefore, this air-fuel ratio becomes an appropriate value that matches the target value, and problems such as the generation of black smoke caused by insufficient air and the generation of excess heat caused by excess air can be prevented.

FIG. 2 shows another embodiment 1 of the differential pressure type flow rate measuring device according to the present invention.
91 is shown.

In this embodiment, in contrast to the embodiment shown in FIG.
A temperature sensor 19 is installed only on the outflow side of the air heater 3.

In this case, the inflow side air density γ1 is assumed to be a constant,
The following equation (3) is applied.

Here f(T2)=(γ-/1', -1)P.

As can be understood from the above equation (3), this embodiment is applied when the inflow side pressure P1 and temperature T1 of the air heater hardly change, and has the same effect as the embodiment shown in FIG. present.

In each of the above embodiments, the temperature sensors 17 and 19 are provided on both the inflow side and the outflow side from the air heater (Fig. 1), and the case where the temperature sensor 19 is provided only on the outflow side (Fig. 2). Although described above, the temperature sensor 17 may be provided only on the inflow side. In this case, the outlet pressure P
This is applied when there is almost no change between temperature T2 and temperature T2.

[Effects of the Invention] As described above, according to the present invention, the differential pressure between the inflow side and the outflow side can be reduced by the temperature of each fluid on the inflow side and/or the outflow side of the throttling mechanism provided in the flow path. Since the correction is performed, the flow rate of the fluid flowing in the flow path can be accurately calculated. Therefore, when the present invention is applied to air flow measurement in air-fuel ratio control, etc., the air-fuel ratio (q) will match the target value, problems such as insufficient air or excess air can be resolved, and the result will be non-polluting. Highly reliable air-fuel ratio control can be achieved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram of one embodiment of the differential pressure type flow m measuring device according to the present invention, Fig. 2 is a block diagram of another embodiment, and Fig. 3 is a conventional differential pressure type flow m measuring device. It is a block diagram of a flow m measuring device. 1... Air duct 3... Air heater 5.
... Orifice constriction section 11 ... Differential pressure transmitter 13 ...
・Temperature correction section 15...square root calculation section 17.19
...Temperature sensor agent Patent attorney Kensuke Chika Agent Patent attorney Hiroshi Mitsumata Figure 1 Q Figure 2 Figure 8

Claims (1)

[Scope of Claims] Differential pressure measuring means for measuring the differential pressure of a fluid between the inflow side and the outflow side of a throttle mechanism provided in the middle of a flow path; A differential pressure type flow rate measuring device comprising: a temperature detecting means for detecting; and a differential pressure correcting means for correcting the measured differential pressure based on the detected fluid temperature on the inflow side and/or the outflow side. .