JP6596264B2 - Ignition electrode for low temperature liquefied gas combustion and explosion test - Google Patents

Description

  The present invention relates to an ignition electrode used for a combustion / explosion test in a system in which a low-temperature liquefied gas or a system coexisting with a low-temperature liquefied gas, and more particularly to an ignition electrode for a low-temperature liquefied gas combustion / explosion test.

In order to handle flammable low-temperature liquefied gas safely, it is necessary to measure conditions that cause combustion and explosion such as measurement of explosion range, surface catalytic effect, minimum ignition energy, and power of explosion.
As an example of a test apparatus used for such measurement, as an object for combustible gas, for example, an “explosion limit region measuring apparatus” disclosed in Patent Document 1 and disclosed in Patent Document 2 “ There is an example of a simple facility such as a “flammable gas / steam explosion test device”.
Further, as a test apparatus for powder, for example, “Dust explosion test apparatus” disclosed in Patent Document 3, “Dust explosion test apparatus and dust explosion test method” disclosed in Patent Document 4, patent There are a “minimum ignition energy evaluation apparatus for powder” disclosed in Document 5 and a “powder ignition test apparatus” disclosed in Patent Document 6.
These are tests in a space released at atmospheric pressure, and it was difficult to apply to tests at temperatures other than room temperature and tests involving liquefied gas.

  Prior art related to the explosive experiment of low-temperature liquefied gas includes igniting and exploding a mixture of liquid oxygen and liquid methane with an ignition source installed above a stainless steel container containing a mixture of liquid oxygen and liquid methane. The examined example is disclosed in Non-Patent Document 1.

Japanese Patent Laid-Open No. 8-145921 JP 2010-8135 A JP 2000-310583 A JP 2011-220813 A JP2013-152196A JP-A-11-201925

Kanto Shun et al., The Abstracts of 2008 Annual Meeting of the Japanese Society for Thermopharmaceutical Science, pp.29-30 (2008)

As a method of igniting a combustible gas or a mixture of a combustible gas and a combustion-supporting gas, discharge is a common method (for example, ISO-10156: Gases and gas mixture-Determination of fire potential and oxidizing ability for the selection of cylinder valve outlets).
On the other hand, as a method of igniting a low-temperature liquefied gas in a liquid state, there are a method of igniting discharge in a gas phase in which a low-temperature liquefied gas coexists and propagating a flame to the liquid phase, or a method of igniting by directly discharging in the liquid phase .
Non-Patent Document 1 corresponds to a method of igniting in the gas phase, but in this method, the evaporation rate of the liquid mixture of liquid oxygen and liquid methane, which is the specimen, is very large due to the intrusion heat from the outside air into the container. Therefore, not only the composition of the analyte sample cannot be estimated in both the gas phase and the liquid phase, but also a large number of analyte samples are required. A lot of cost was necessary.

On the other hand, the method of directly discharging and igniting in the liquid phase has problems of the distance between the discharge electrodes and the dielectric breakdown strength.
In general, the relationship between the discharge and the distance between the discharge electrodes depends on the dielectric breakdown strength of the discharge atmosphere, and the dielectric breakdown strength in the liquid phase is often larger than in the gas phase. For example, the dielectric breakdown strength of air at room temperature is 3 MV / m, whereas the dielectric breakdown strength of liquid nitrogen is 56 to 65 MV / m.
This means that the discharge in the liquid phase not only requires a very large electromotive force (potential difference between the electrodes), but also the distance between the electrodes must be accurately adjusted to obtain the required discharge. Suggest.

  In addition, in a temperature range that is significantly lower than room temperature, such as a liquid mixture of liquid oxygen and liquid hydrocarbon, the distance between the electrodes of the discharge electrode may fluctuate compared to that at room temperature due to heat shrinkage. It was. Furthermore, repeated discharges inevitably wear the tip of the discharge electrode, and a mechanism for adjusting the distance between the electrodes during the test is necessary. If the reproducibility of the discharge cannot be obtained if the distance between the electrodes varies, and the reproducibility of the discharge in the liquid phase cannot be secured, the minimum ignition energy and explosion range of the low-temperature liquefied gas should be measured by the combustion / explosion test. I can't.

  Furthermore, in the explosion test using a large amount of specimen sample, it is preferable to use as little specimen sample as possible because the power of explosion is greater, and it is suitable for small explosion test equipment using a small quantity of specimen sample. Therefore, it has been desired to make the discharge electrode small and simple. However, there has never been an ignition discharge device that ignites reproducibly and accurately in the liquid phase of flammable and combustion-supporting low-temperature liquefied gas.

  The present invention has been made to solve the above-described problems, and when performing a combustion / explosion test of a liquid state low-temperature liquefied gas or a system in which a low-temperature liquefied gas coexists, the liquid-state low-temperature liquefied gas or An object of the present invention is to provide a low temperature liquefied gas combustion / explosion ignition electrode for ignition in a system in which a low temperature liquefied gas coexists.

(1) A low temperature liquefied gas combustion / explosion test ignition electrode according to the present invention is used for a combustion / explosion test apparatus of a system in which a low temperature liquefied gas or a low temperature liquefied gas coexists,
A ground electrode provided on the inner wall surface of the liquid reservoir in the liquefaction container for storing the low-temperature liquefied gas in a liquid state;
And an electrode rod provided so that the distance between the electrodes and the ground electrode can be adjusted.
The low-temperature liquefied gas or the system in which the low-temperature liquefied gas coexists include liquid oxygen + liquid methane, liquid oxygen + liquid propane and the like, and a mixed system of flammable liquefied gas and liquid oxygen + solid metal powder A solid resin and a solid mixture having an active surface are included, and these are collectively referred to as “a system in which a low-temperature liquefied gas or a low-temperature liquefied gas coexists”.

(2) In the above described (1), an electrode rod insertion tube in which the electrode rod is inserted and one end side communicates with the liquefaction container;
A seal portion through which the electrode rod is inserted to seal the other end of the electrode rod insertion tube;
An inter-electrode distance adjusting unit that adjusts the inter-electrode distance is provided.

(3) In the above-described (1) or (2), the ground electrode may be configured such that the thickness of a liquid reservoir portion in which the liquid low-temperature liquefied gas is stored in the liquefaction container is t. The contact area S with the inner wall surface of the portion is 4πt ² or more.

  In the present invention, the ground electrode provided on the inner wall surface of the liquid reservoir in the liquefaction container for storing the low-temperature liquefied gas in the liquid state, and the electrode rod provided in such a manner that the distance between the electrodes can be adjusted. As a result, it is possible to ignite the low-temperature liquefied gas by reproducibly and accurately discharging in the liquid phase of a small amount of low-temperature liquefied gas, and as a result, estimate the minimum ignition energy and explosion range, or powder It is possible to repeatedly perform combustion / explosion tests at low temperatures in a system in which a liquefied gas coexists with a surface effect having a catalytic effect.

It is explanatory drawing explaining the internal structure of the ignition electrode for low temperature liquefied gas combustion and an explosion test which concerns on embodiment of this invention. It is explanatory drawing explaining the whole structure of the ignition electrode for low temperature liquefied gas combustion and an explosion test which concerns on embodiment of this invention. It is explanatory drawing explaining the relationship between the thickness of the liquid reservoir which concerns on embodiment of this invention, and the shape of a ground electrode. It is a block diagram of the ignition circuit which concerns on embodiment of this invention. It is explanatory drawing explaining the discharge at the time of using a container as a ground electrode which is one side of a discharge electrode.

  First, after describing the desirable form of the ignition electrode used for the combustion / explosion test of the liquid low-temperature liquefied gas, the ignition electrode for the low-temperature liquefied gas combustion / explosion test according to the present invention (hereinafter sometimes simply referred to as “ignition electrode”). Exist).

<Preferred form of ignition electrode>
In general, when providing an ignition electrode in the liquid phase of liquefied combustible gas and combustion-supporting gas, a method of providing two electrodes in the liquid, and a method of providing a ground electrode (earth) and one electrode There is.
The method of providing two electrodes makes it easy to determine the distance between the electrodes in advance, but has a disadvantage that the structure and wiring are complicated.

  On the other hand, the method of providing a ground electrode and one electrode does not specify the actual discharge position from the electrode toward the ground electrode, so the inter-electrode distance (discharge distance) between the electrode and the ground electrode is constant. It seems difficult to do. For example, when the ground electrode is a container 51 composed of a hemispherical part 51 a and a cylindrical part 51 b as shown in FIG. 3 and is discharged from the electrode rod 53 toward the container 51, the discharge location is the hemispherical part of the container 51. Depending on whether it is 51a or cylindrical part 51b, the discharge distance differs, and if the discharge distance is long, it is difficult not only to generate a discharge but also to estimate the discharge energy even if it is discharged.

  In addition, when the discharge is repeated, the distance between the electrodes becomes longer due to melting or the like, or when the low temperature liquefied gas is stored and discharged in the liquid phase, thermal contraction due to temperature change In some cases, the discharge distance may change from that at room temperature. Therefore, in order to discharge with good reproducibility even when discharging is repeatedly performed or when low-temperature liquefied gas is stored, a mechanism capable of arbitrarily adjusting the distance between electrodes is required.

  From the above, as a desirable form of the ignition electrode, from the viewpoint of simplifying the structure and wiring, one is a ground electrode, the other is a single electrode, and the discharge location can be specified, When discharging is performed in the liquid phase of a low-temperature liquefied gas, a mechanism capable of arbitrarily adjusting the distance between the electrodes is provided.

Next, each structure of the ignition electrode which has such a desirable form ignition electrode is demonstrated based on FIGS.
An ignition electrode 1 according to an embodiment of the present invention ignites the low-temperature liquefied gas by discharging in the liquid of the low-temperature liquefied gas in a combustion / explosion test apparatus of a system in which low-temperature liquefied gas or a low-temperature liquefied gas coexists. The ground electrode 17 provided on the inner wall surface of the liquid reservoir 15 in the liquefaction container 13 storing the low-temperature liquefied gas in the liquid state, and the electrode provided so that the distance between the electrodes can be adjusted. A rod 19; an electrode rod insertion tube 23 into which the electrode rod 19 is inserted and communicated with the liquid reservoir portion 15 at one end side; and a seal portion 25 through which the electrode rod 19 is inserted to seal the other end side of the electrode rod insertion tube 23 And an inter-electrode distance adjusting unit 27 for adjusting the inter-electrode distance.
Hereinafter, each configuration will be described in detail.

<Liquefaction container>
The liquefaction container 13 includes a cooling block 14 that cools and liquefies the gaseous low-temperature liquefied gas introduced from the gas introduction unit 11, and a liquid storage unit 15 that stores the low-temperature liquefied gas that has been liquefied into a liquid state. It consists of
The gas introduction unit 11 is provided on the side surface of the liquefaction vessel 13 for introducing a gaseous low-temperature liquefied gas, and is connected to an external gas supply source (primary side) by joining a pipe by brazing or the like. The

  The cooling block 14 receives the supply of the gaseous low-temperature liquefied gas from the gas introduction unit 11 and receives cold supply from, for example, a refrigerator (not shown) to liquefy the gaseous low-temperature liquefied gas. It is preferable that the low-temperature liquefied gas in the gaseous state introduced from the gas introduction part 11 is formed of copper having high thermal conductivity capable of transmitting sufficient cold heat.

As shown in FIG. 1, the liquid reservoir portion 15 is formed of a cylindrical container having a bottom portion 15 a and stores the low-temperature liquefied gas cooled and liquefied by the cooling block 14. Etc. are joined.
Furthermore, in order to obtain an appropriate discharge distance between the liquid reservoir 15 and the electrode rod 19, the bottom 15a is provided with a protruding ground electrode 17.

The liquid reservoir 15 is preferably made of copper, brass, or the like, which has good heat conduction and is relatively easy to join and process.
Furthermore, the liquid reservoir 15 needs to have a strength that can withstand the conditions for storing the liquefied low-temperature liquefied gas, but it is as thin as possible and manufactured with the smallest mass as long as it can be manufactured. It is desirable. The reason is as follows.

Usually, the low temperature liquefied gas combustion / explosion test is performed by accommodating the liquefied container 13 for storing the liquefied gas in a gaseous state in a pressure and temperature controlled container (not shown).
If the thickness of the liquid reservoir 15 is large and the mass of the cylindrical body or the bottom 15a is large, the material forming the liquid reservoir 15 during the combustion / explosion test will cause a large amount of debris in the pressure-resistant thermostatic container. As a result, the kinetic energy of the scattered fragments increases and the risk of damage to the pressure resistant thermostatic container increases.

  Further, if the pressure resistance of the liquid reservoir 15 is high, the liquid reservoir 15 is damaged while maintaining a high pressure. Therefore, the material of the damaged liquid reservoir 15 is scattered in a state where large kinetic energy is accumulated and The risk of collision with the pressure and temperature constant container and damage to the pressure and temperature constant container is further increased.

  Therefore, it is desirable that the liquid reservoir 15 be manufactured with the container wall of the liquid reservoir 15 as thin as possible in order to suppress damage to the surroundings of the pressure-resistant thermostatic container or the like when explosion occurs due to ignition discharge. As a result, the accumulated energy until breakage is reduced and the amount of scattered material is also reduced, so that damage to the pressure-resistant thermostatic container can be reduced.

  On the other hand, if the wall thickness of the liquid reservoir 15 becomes too thin, if the current density increases on the wall surface of the liquid reservoir 15 when repeated ignition discharge is performed to perform a combustion / explosion test, the low-temperature liquefied gas in the liquefaction vessel 13 If the concentration of the liquid is outside the explosion range or the ignition energy is low, the wall surface of the liquid reservoir 15 may be damaged without being ignited by discharge, and the liquefied low-temperature liquefied gas may not be retained. is there. In this case, as described later, it is necessary to secure a contact area S of the contact surface between the ground electrode 17 and the inner wall surface of the liquid reservoir 15 in accordance with the thickness t of the liquid reservoir 15.

<Ground electrode>
The ground electrode 17 is provided on the inner wall surface of the liquid reservoir 15 so that when a small amount of the low-temperature liquefied gas is stored in the liquid reservoir 15, the discharge location is in the liquid phase of the low-temperature liquefied gas. It is desirable to provide the bottom 15 a of the liquid reservoir 15.

  In order to specify the discharge location, the ground electrode 17 is preferably a projection having a conical shape as shown in FIGS. 1 and 5, for example. Further, by using such a projection, the current density at the time of discharge is increased. The tip of the protrusion is set to the highest value, and the current density decreases toward the contact surface that contacts the inner wall surface of the liquid reservoir 15. If the current density increases at a position away from the discharge location (the electric circuit becomes narrow), damage at the position may be caused.

Therefore, in order to prevent the liquid reservoir 15 from being damaged, it is necessary to sufficiently reduce the current density at the contact surface where the ground electrode 17 and the liquid reservoir 15 are in contact. For this purpose, it is desirable that the contact area S of the contact surface satisfy a relationship of S ≧ 4πt ² where t is the thickness of the liquid reservoir 15.
By doing so, the thickness of the liquid reservoir portion 15 can be reduced while minimizing the damage to the liquid reservoir portion 15 by reducing the current density in the liquid reservoir portion 15 when discharged, and when ignition occurs The possibility of damage to the surroundings can be minimized.

  When the minimum ignition energy of the liquid phase of the low-temperature liquefied gas is obtained, the length of the ground electrode 17 is such a length as to be submerged in the liquid, but not limited thereto, the minimum ignition energy of the gas phase of the low-temperature liquefied gas is determined. When it is desired, the length of the tip of the ground electrode 17 may be in the gas phase. In this case, the insertion depth of the electrode rod 19 to be described later is appropriately selected so that the distance between the electrodes can be adjusted.

<Electrode bar>
The electrode rod 19 is for discharging between the ground electrode 17 and the electrode rod 19 so that the tip of the electrode rod 19 is below the liquid level of the liquid low-temperature liquefied gas stored in the liquid reservoir 15. The rod insertion tube 23 is inserted into the liquid reservoir 15.
Furthermore, the electrode rod 19 is covered with an insulating coating 21 in order to maintain electrical insulation from the liquefaction container 13.
The electrode rod 19 is preferably made of a material having good electrical conductivity, such as copper, but aluminum that easily burns in an oxygen atmosphere is not preferred even if the electrical conductivity is good.

<Electrode bar insertion tube>
The electrode rod insertion tube 23 is inserted through the electrode rod 19 covered with the insulating coating 21, and one end side thereof is connected to the cooling block 14 and communicates with the liquid reservoir 15.

<Seal part>
The seal portion 25 is for the electrode rod 19 to penetrate and seal the other end side of the electrode rod insertion tube 23. By tightening the nut 29 and the gland 31 and pressing the seal member 25a, the electrode rod insertion tube 23 is sealed. Increases the sealing performance.
The material of the seal member 25a is preferably a resin such as Teflon (registered trademark) that has good insulation and high gas sealability at room temperature.

<Distance adjustment part between electrodes>
The interelectrode distance adjusting unit 27 adjusts the interelectrode distance between the tip of the electrode rod 19 and the tip of the ground electrode 17. As an example of the inter-electrode distance adjusting unit 27, there is a combination of a male threaded portion 27a threaded on the electrode rod 19 and a female threaded portion 27b fixed to the electrode rod insertion tube 23 as shown in FIG. The distance between the electrodes can be arbitrarily adjusted by turning the electrode rod 19.

When the ignition electrode 1 having the above configuration is connected to an ignition circuit 41 as shown in FIG. 4 for discharging, for example, the low-temperature liquefied gas composition in the liquefaction vessel 13, the capacitance, the maximum voltage when discharged, etc. It is possible to determine the optimum interelectrode distance by measurement.
Furthermore, by using the ignition electrode 1, it is possible to measure the minimum ignition energy of the liquid low-temperature liquefied gas stored in the liquefaction container 13. However, the following points should be noted when measuring the minimum ignition energy.

First, whether or not an ignition phenomenon occurs due to discharge in the liquefaction vessel 13 is greatly influenced by the low-temperature liquefied gas composition and discharge energy in the liquefaction vessel 13.
For example, if the combustible material and the combustible material are present in the equivalent ratio required for complete combustion, either the combustible material or the combustible material concentration is very high while the ignition is performed with very low ignition energy. In a lean case, if the ignition energy is low, ignition will not occur even within the explosion range. For example, in an oxygen gas-methane gas mixed material (room temperature), when the equivalent ratio is 1, the minimum ignition energy required for ignition is about 0.3 mJ, but when the equivalent ratio is 0.8 or 1.2, the minimum ignition energy is about 2 mJ. By the way, the ignition energy when specifying the explosion range is 10 J, and the general explosion range should be considered as “a concentration range where an explosion occurs even at 10 J discharge”.

  On the other hand, the discharge energy largely depends on the low-temperature liquefied gas composition and state in the liquefaction vessel 13. When the distance between the tip of the electrode rod 19 and the tip of the ground electrode 17 is very short, the dielectric breakdown voltage is constant, so that the discharge occurs even with a small potential difference and the discharge energy is measured to be small. As the distance increases, the discharge energy gradually increases. Further, when the distance between the electrodes becomes longer and exceeds the dielectric breakdown distance with respect to the voltage supplied to the ignition electrode 1, the discharge itself is not performed. Therefore, when igniting by discharge, it is necessary to set the distance between the electrodes appropriately.

  Although it is desirable that the discharge energy is originally a difference between the amount of electricity stored in the spark igniter 43 and the amount of electricity remaining in the spark igniter 43 after discharge, it is extremely difficult to accurately measure the amount of electricity before and after the discharge. It is difficult to. In addition, there is a method of obtaining the discharge energy by measuring the current and voltage at the time of discharge using the current / voltage measuring device 45, but it is difficult to measure the instantaneous current value due to the limitation of the device response accuracy. . On the other hand, a method of connecting a capacitance meter (not shown) to the ignition electrode 1 and measuring the capacitance before discharge and estimating the discharge energy from the measured value of the maximum potential difference between the electrodes during discharge is compared. Simple and accurate.

  With these considerations in mind, while keeping the low-temperature liquefied gas composition in the liquefaction vessel 13 constant, the distance between the electrodes is changed little by little to discharge each time, and the presence or absence of ignition, the capacitance and the maximum voltage are determined. If the discharge energy is estimated by measuring or the like, the minimum ignition energy for the low-temperature liquefied gas composition in the liquefaction vessel 13 can be observed.

  Further, the inter-electrode distance between the tip of the electrode rod 19 and the tip of the ground electrode 17 is adjusted by the inter-electrode distance adjusting unit 27 by changing the low-temperature liquefied gas composition in the liquefaction vessel 13 and obtaining predetermined discharge energy. By discharging, the explosion range can be measured using the ignition electrode 1.

  As described above, the ignition electrode 1 according to the present embodiment can be used as an ignition source of the low-temperature liquefied gas by discharging in the liquid phase of the low-temperature liquefied gas. It is possible to repeatedly and accurately measure and observe phenomena accompanied by explosion and combustion of liquefied gas, such as measurement of the explosion range and the influence of impurities.

  In Example 1, in order to verify whether or not discharge is possible by specifying the discharge location using the ground electrode and adjusting the distance between the electrodes, a discharge test was performed using the ignition electrode 1 connected to the ignition circuit 41 shown in FIG. went. Hereinafter, the results of the discharge test will be described.

First, the degree of damage in the liquid reservoir 15 when the discharge was repeatedly performed without providing the ground electrode 17 in the liquid reservoir 15 of the ignition electrode 1 was confirmed.
In the discharge test according to the first embodiment, gaseous nitrogen (N ₂ ) is introduced from the gas introduction unit 11, and nitrogen is liquefied by the cooling block 14, and about 5 cc of liquid nitrogen (LN ₂ ) is stored in the liquid storage unit 15. Reserved in.
Thereafter, the spark igniter 43 was repeatedly discharged in liquid nitrogen.

As a result of measuring the current and voltage at the time of discharge with the current / voltage measuring device 45 in the ignition circuit 41, both current and voltage varied in the repeated discharge.
Furthermore, the liquid reservoir 15 was damaged and liquid nitrogen leaked and evaporated. After the discharge test was completed, the ignition electrode 1 was returned to room temperature, and the damage state of the liquid reservoir 15 was observed. As a result, the bottom 15a of the liquid reservoir 15 was damaged. In the discharge test, the thickness of the liquid reservoir 15 was 0.2 mm.

  Next, a ground electrode 17 was provided on the bottom 15a of the liquid reservoir 15, and a discharge test was performed. In the first embodiment, the ground electrode 17 is conical (see FIG. 5), and the diameter of the surface of the liquid reservoir 15 that contacts the bottom 15a is φd = 1 mm.

Similar to the above discharge test, nitrogen (N ₂ ) in a gaseous state is introduced from the gas introduction part 11 and liquefied by cooling the nitrogen to about 77 K by the cooling block 14, and about 5 cc of liquid nitrogen (LN ₂ ) is obtained. The liquid was stored in the liquid reservoir 15.

First, a capacitance meter (not shown) is connected to the ignition electrode 1 to measure the capacitance.
Next, the spark igniter 43 and the current / voltage measuring device 45 are connected to the ignition electrode 1 (see FIG. 4), and an appropriate voltage is applied to the ignition electrode by the spark igniter 43 to cause the ignition electrode 1 to discharge. The discharge voltage was measured by 45.

This test was performed both when the inter-electrode distance was adjusted by the inter-electrode distance adjusting unit 27 and when the inter-electrode distance was not adjusted.
As a result, by providing the ground electrode 17 on the bottom portion 15a of the liquid reservoir 15, there is no variation in both current and voltage, and it is consistent with the estimated value of discharge energy by capacitance measurement, and repeated discharge. Could be done.

  As described above, in the ignition electrode 1 for low-temperature liquefied gas combustion / explosion test, the ground electrode 17 having a protruding tip is provided in the liquid reservoir portion 15 of the low-temperature liquefied gas, thereby stably discharging even in the liquid low-temperature liquefied gas. In addition, it was shown that an appropriate discharge distance can be adjusted by adjusting the distance between the ignition electrodes.

  In Example 2, a verification experiment was conducted on the feasibility and reproducibility of discharge ignition using the ignition electrode 1 connected to the ignition circuit 41 shown in FIG. Hereinafter, the results of the discharge ignition explosion test will be described.

In the discharge ignition explosion test in Example 2, first, the liquid reservoir 15 is cooled to 90 K or less, and then the distance between the tip of the electrode rod 19 and the tip of the ground electrode 17 is adjusted by the interelectrode distance adjusting unit 27. did.
Thereafter, gaseous oxygen O ₂ was introduced from the gas introduction part 11, the gaseous oxygen was liquefied by the cooling block 14, and about 3 cc of liquid oxygen (LO ₂ ) was stored in the liquid reservoir 15.
Next, methane CH ₄ in a gaseous state is introduced from the gas introduction unit 11 in an amount such that the volume mixing ratio in the gaseous state with the liquid oxygen stored in the liquid reservoir 15 is ₄ vol%, and the cooling block 14 Thus, liquid methane (LCH ₄ ) obtained by liquefying CH ₄ in the gaseous state was stored in the liquid reservoir 15 together with LO ₂ .

While discharge was repeated in the liquid mixture by the spark igniter 43 in a state where the liquid mixture of LO ₂ and ₄ vol% LCH ₄ was stored in the liquid reservoir 15, no explosion was observed.
From this state, the methane in a gaseous state and further introduced through the gas inlet port 11, the methane in the gaseous state is liquefied by cooling the cooling block 14, the mixing of LO ₂ and LCH ₄ which increased the LCH ₄ concentration up to 20 vol% The liquid was stored in the liquid reservoir 15 and discharged in the mixed liquid.
As a result, detonation was observed in the liquid reservoir 15 and it was shown that the combustion explosion test can be carried out in the liquid phase of low-temperature liquefied gas.

In Example 2, the thickness of the liquid reservoir 15 was t = 0.2 mm, while the ground electrode 17 was conical and the diameter of the contact surface with the liquid reservoir 15 was φ1 mm ( (See FIG. 5). At this time, the contact area S of the contact surface between the ground electrode 17 and the liquid reservoir 15 satisfies the relationship of S ≧ 4πt ² where t is the thickness of the liquid reservoir 15. Therefore, the current density at the contact surface can be sufficiently reduced, and damage to the wall surface of the liquid reservoir 15 can be prevented when no explosion is observed even after discharge.

  As described above, by using the low temperature liquefied gas combustion / explosion ignition electrode according to the present invention, in the liquid phase of the low temperature liquefied gas, it is possible to discharge with good reproducibility by adjusting the distance between the electrodes, It was proved that the combustion and explosion tests can be performed by igniting in the liquid phase of a mixture of flammable gas and supporting gas.

DESCRIPTION OF SYMBOLS 1 Ignition electrode 11 Gas introduction part 13 Liquefaction container 14 Cooling block 15 Liquid storage part 15a Bottom part 17 Ground electrode 19 Electrode rod 21 Insulation coating 23 Electrode insertion tube 25 Seal part 25a Seal member 27 Interelectrode distance adjustment part 27a Male thread part 27b Female thread portion 29 Nut 31 Ground 41 Ignition circuit 43 Spark igniter 45 Current / voltage measuring device 51 Container 51a Hemisphere portion 51b Cylindrical portion

Claims (3)

An ignition electrode for a low temperature liquefied gas combustion / explosion test used in a combustion / explosion test apparatus of a system in which low temperature liquefied gas or a low temperature liquefied gas coexists and discharges in a liquid phase ,
A projection-shaped ground electrode provided on the inner wall surface of the liquid reservoir in the liquefaction container for storing the low-temperature liquefied gas in a liquid state;
An ignition electrode for a low-temperature liquefied gas combustion / explosion test, comprising: an electrode rod provided such that the distance between the electrode and the ground electrode can be adjusted. An electrode rod insertion tube in which the electrode rod is inserted and one end side communicates with the liquefaction container;
A seal portion through which the electrode rod is inserted to seal the other end of the electrode rod insertion tube;
The ignition electrode for a low-temperature liquefied gas combustion / explosion test according to claim 1, further comprising an inter-electrode distance adjusting unit that adjusts the inter-electrode distance. The ground electrode has a contact area S with the inner wall surface of the liquid reservoir of 4πt ² or more, where t is the thickness of the liquid reservoir in the liquefaction container where the liquid low-temperature liquefied gas is stored. The ignition electrode for a low-temperature liquefied gas combustion / explosion test according to claim 1 or 2.