JPS6014140A - Method and apparatus for measuring gas content containing in liquid - Google Patents

Abstract

PURPOSE:To measure a gas content contg. in a liquid by varying a pressure of the liquid while flowing the liquid through a liquid flow passage with maintaining a flow rate per unit time constant, and measuring pressures and flow velocities at high and low pressures respectively. CONSTITUTION:The liquid flow passage 2 for circulating liquid in a containing tank 1 is provided with a ball valve 5, a liquid pump 6, a pressure gauge 7, a change-over valve 8, a pressure detector 9, a current meter 10, a change-over valve 11, a gas mixing apparatus 12, a check valve 13 and a ball valve 14. A variable throttle valve 15 is controlled so that a quantity per unit time of liquid sent out from the pump 6 becomes constant independently of the liquid pressure variation in case the gas content is measured. Next, the apparatus 12 is operated to mix the gas into liquid. The pressure and the flow velocity at high pressure are detected by the detector 9 and the meter 10 respectively. Next, the valves 8, 11 are changed over, the pressure and the flow velocity at low pressure are detected, and the mixing rate of gas in liquid is measured by a controlling device 27.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas content measuring method and apparatus for measuring the gas content mixed in a plastic liquid component or the like.

In reaction injection molding, in which molded products are produced by colliding and mixing at least two plastic liquid components that react with each other, the purpose of this is to make the foam structure inside the molded product denser, improve its physical properties and appearance, and increase its commercial value. In this case, air is mixed into the plastic liquid component as fine bubbles. Conventionally, 1fi (Japanese Unexamined Patent Publication No. 56-21036), in which the flow of the plastic liquid component is stopped and the gas content is measured, has the disadvantage that circulation must be stopped during the measurement.

The present invention provides a liquid pump, a gas mixing device, a pressure switching device, a pressure detector, and a current meter in a liquid flow path, and maintains a constant flow rate per unit time. The above-mentioned drawbacks of the conventional method were solved by measuring the gas content in the liquid by changing the pressure of the liquid and visually measuring the pressure and flow rate at high pressure and the pressure and flow rate at low pressure. It is an object of the present invention to provide a gas content measuring method and a measuring device capable of measuring the gas content while continuously flowing a liquid such as a plastic liquid component without stopping the flow of the liquid.

The present invention will be explained below based on the drawings.

The drawing shows an outline of a RIM high-pressure reaction molding apparatus using the gas content measuring device of the present invention, and in the drawing, 1 is a storage tank for storing a plus book liquid component (liquid). This storage tank 1 has both ends 2 of a liquid flow path 2 made of a pipe.
a and 2b are connected, and a stirring blade 4 rotated by a motor 3 is provided inside. The liquid flow path 2 circulates the liquid in the storage tank 1, and includes a ball valve 5, a liquid pump 6, a pressure 817, a switching valve 8, a pressure JJ detector 9, a flow rate it10, and a switching valve 11. , gas mixing device 12, Chetsugi valve 13
, ball valves 14 are provided in the above order. A liquid flow path 17.18 equipped with a variable throttle 15.16 is branched from the two switching valves 8.11.
The other ends of these channels 17 and 18 are located between the switching valve 8 and the pressure detector 9, and between the switching valve 11 and the gas entrainment device 1.
2 are respectively connected to the liquid flow paths 2 between them.

Further, a gas supply source 20 is connected to the gas mixing device 12 via a pipe 19, and this pipe 19 is connected to an air regulator 21, an air pressure gauge 22, an air flow rate control valve 23, Air flow meter 24
, an air solenoid valve 25, and an air pump valve 26 are provided so that a desired amount of gas can be mixed into the liquid that is circulated through the liquid flow path 2 by the operation of the liquid pump 6.

Furthermore, a control device 27 is connected to the pressure detector 9, flow meter 10, and air solenoid valve 25. This control device 27 is a meter that calculates the amount of gas contained in the liquid flowing in the liquid stream N2 from the liquid pressure measured by the pressure detector and the liquid flow rate measured by the current meter 10. The unit 28 compares the actual measured value of the gas content calculated by the calculating unit 28 with the set value of the gas content stored in advance in the storage unit 33, and if the actual measured value is smaller than the set value, A comparison command section 29 is provided which opens the air solenoid valve 25 and closes the air solenoid valve 25 when the two are equal or larger.

As is well known, a measuring cylinder 30 and a mixing head 31 are connected to the storage tank 1, and the plastic liquid component supplied from the storage tank 1 is sent to the mixing head 31, and is then connected to another measuring cylinder (not shown). By mixing with other plastic liquid components sent from other companies, molded products can be obtained by reaction of the liquid components. In addition, 32 is a display unit that displays whether the measured value of the gas content is larger than, smaller than, or equal to the set value, and 34 is a switching unit that switches the two switching valves 8 and 11 in synchronization with each other. Akujiko: [That's it. A flow meter can be used instead of the current meter 10.

The switching valve 11 and the variable throttle 16 constitute a pressure switching device.

Next, the operation of the gas content measuring device configured as described above will be explained.

When measuring the gas content using this device, the amount of liquid sent out from the liquid pump 6 per unit time is kept constant regardless of the pressure fluctuation of the liquid at the pressure detector 9. , adjust the variable aperture 15.

That is, the liquid discharged from the liquid pump 6 does not pass through the liquid flow path 17 but goes straight through the switching valve 8, and the flow rate meter 1
In the state shown in the figure in which the flow direction of the liquid that has passed through the section 9 is switched by the switching valve 11 and flows into the liquid flow path 18, the liquid is circulated and the pressure of the pressure drop 7 is read. Next, the switching valve 8° 11 is switched, and the liquid discharged from the liquid pump 6 is made to flow into the liquid flow path 17, and the liquid that has passed through the flow meter 10 is made to go straight without passing through the variable throttle 16, thereby circulating the liquid. The variable throttle 15 is adjusted so that the pressure gauge 7 shows the same pressure as before. By this operation, the discharge pressure of the liquid pump 6 is always the same regardless of the switching state of the downstream valve, so the discharge flow rate also becomes uniform.

When the above adjustment is completed/υ, the liquid pump 6 is operated to circulate the liquid through the liquid flow path 2, while the gas mixing device 12 is operated to mix gas into the liquid as fine bubbles.

In the case shown in the figure, the liquid sent out from the liquid pump 6 goes straight through the switching valve 8, flows into the liquid flow path 18 at the next switching valve 11, passes through the variable throttle 16, and flows to the gas mixing device 12, but the variable throttle 16, the pressure of the liquid increases, and air bubbles within the liquid are compressed in accordance with the pressure. The pressure and flow rate at this time are detected by a pressure detector 9 and a current meter 10.

After detecting pressure J and flow velocity at high pressure, switch )(
The two switching valves 8.11 are simultaneously switched by the action of the actuator 34 for "a", and the liquid that had previously flowed straight through the switching valve 8 is caused to flow into the liquid flow path 17 and pass through the variable throttle 15. The liquid that has been flowing into the liquid channel 18 until now is made to go straight and flows into the gas mixing device 12. In this case, the liquid returned from the liquid channel 17 to the liquid channel 2 flows without resistance, so the liquid pressure horn is The pressure sensor 9 and the flow meter 10 detect the pressure and flow rate as before.] - As shown, the fluid pressure at the pressure sensor 9 is Even if it changes, the circulation resistance of the entire liquid is made equal by adjusting the variable throttle 15, so the liquid flow rate per unit time will not change.

The detection results of pressure and flow velocity at high pressure and low pressure are immediately sent to the control device 27. Based on the pressure and flow velocity detected by the pressure detector 9 and the current meter 10, the control device 27 calculates the amount of gas mixed into the liquid by calculating the formula % (%) calculated as follows. Calculate the ratio (Xa).

The calculation is subject to the following three conditions.

(1) The flow rate of the liquid sent out from the liquid pump 6 is constant.

(2) The air state equation (PV = constant) holds true even when mixed with liquid.

(3) Liquids are incompressible.

1) a: Atmospheric pressure (1,033 kg/cm2>Pl: First pressure condition kGl/d (absolute pressure) P2: Second pressure condition kQ/cm2 (absolute pressure) Vm: L holiday M4d Va: Under Pa Volume of entrained gas under P+ d V+: Volume of entrained gas under P+ d V2: Volume of entrained gas under P2 d S+: Velocity of liquid under P+ CTII/5ecS2
:Velocity of liquid under P2 cyn/5ecA: Cross-sectional area of liquid flow path 2 d Considering the volume of liquid passing per unit time, Va xl
, 033=V+ P+ =V2 P2V2 = Va
xl, 033/P2 ・・・・・・・・・(1) Vl = Va X 1 , 033/P+ −・・=・=
= (2) V2 - Vl = Va X 1.033/P
2-Vaxl, 033/P+ = 1.033Va (1/P2 - .1/P+)・
・・・・・・・・・・・・・・・ (3) Vl +VII
l =Sz XA Vllll =S+ A-V+' =S+ A-1,0
33Va /P ・・・・・・・・・(4) Vz +Vm =S2 XA ・・・・・・・・・(5
) (4), from formulas (5), V2 +S+ A-Vl = 82 A Vz Vl = S2 A-8t A = A (S2-8t > ...... (6) (3)
, from formula (6), 1.033Va (1/P2 -1/P+ )=A (
32-8+ ) 1.033Va (PI P2 )/PI P2=A
<82 -8+),', Va'=A (S2 -8t>・PI P
2/((PI-P2)Xl,033)...
... (7) Mixing rate Xa == Va / (
Vm→-Va) From formula (4), Xa = Va/ (St A-1,033Va /P+
4-Va) -Va/(S+△10Va (1-1,033)/P+)
) From equation (7), (below in the margins), there is a roar.

Calculation of the above equation is performed by the calculation section 28, and the first result is compared with the set value of gas mixture stored in advance in the storage section 33, and if the actual measured value and the set value are equal, the operation is continued in that state. continues, and when the actual measured value is smaller than the set value, the T-ar solenoid valve 25 is activated by a command issued from the comparison command unit 29, and gas is mixed into the liquid from the gas mixing device 12, and the actual measurement is performed. When is larger than the set value, the condition is maintained as it is, and if necessary, the storage tank 7 is replenished with liquid that is not mixed with gas.

In J3 and RIM high-pressure reaction molding, various fillers such as glass fibers are sometimes mixed into the plastic liquid component. The current meter should be of a type that has a sensor mounted around the outer circumference of the pipe, and that does not affect measurement accuracy even if fillers such as air bubbles or glass fibers are mixed into the liquid. Those who satisfy this,
One example is the ultrasonic Doppler underflow m system.

As explained above, in the present invention, the liquid mixed with gas by the gas mixing device is
The pressure of the liquid is changed while keeping it constant and flowing through the liquid flow path, and the pressure and flow rate (flow rate) of the high pressure a4 of the liquid are changed.
Since the gas mixed in the liquid is measured by measuring the pressure and flow rate (flow rate) at constant pressure C1, it is necessary to introduce the liquid component into a cylinder etc. and stop the flow. Unlike conventional measuring methods, it is possible to efficiently measure gas content without harming the molding operation.In addition, the device is simple, responsive, accurate, and quick. Qi 1 Ho content can be measured.

[Brief explanation of drawings]

The drawing is a block diagram showing an embodiment of the gas-containing measuring device of the present invention. 2...Liquid channel, 6...Liquid pump,
9...Pressure detector, 10... Current velocity meter,
11...Switching valve, 12...Gas mixing device, 16...Variable throttle. Applicant Niigata Iron Works Co., Ltd. Asahi Glass Co., Ltd.

Claims (2)

[Claims] (1) While the liquid mixed with gas by the gas mixing device is kept flowing through the liquid flow path at a constant flow rate per unit time, the pressure of the liquid is changed, and the pressure and flow rate of the liquid at high pressure, A method for determining the gas content of a liquid, characterized by measuring the amount of gas mixed in the liquid by measuring the pressure and flow rate at low pressure. (2) A liquid pump that flows the liquid into the liquid flow path while keeping the flow rate constant per unit time, a gas mixing device that mixes gas into the liquid flowing through the liquid flow path, and a gas mixing device that mixes gas into the liquid flowing through the liquid flow path; A pressure switching device for switching the pressure of the liquid flowing through the flow path, a pressure detector that measures the pressure of the liquid flowing through the liquid flow path, and a current meter that measures the flow velocity of the liquid flowing through the liquid flow path are designed. A device for measuring the gas content contained in a liquid.