RU2583979C2 - Method for determining characteristics of actuation of pyrotechnic articles under thermal action and device therefor - Google Patents

Abstract

FIELD: pyrotechnics.

SUBSTANCE: group of inventions relates to equipment for testing of pyrotechnic articles (PI). Method of determining characteristics of spontaneous actuation of PI includes applying thermal action on housing with a given heating rate until its spontaneous actuation and measuring temperature of PI housing at which spontaneous actuation occurred. Said operation is repeated in turns with other similar PI with specified pitch at heating rate to obtain dependence of temperature of spontaneous operation of heating time of housing to define time of spontaneous actuation PI in emergent lowering using calculated rate of heating housing of PI. Device comprises heater with working chamber, temperature measurement means installed on housing of PI and connected to temperature recorder, power supply with controlled output, connected to heater, which is made in form of a heat radiator and located along outer contour of working chamber. Working chamber is made of transparent electrically insulating material and together with heater is placed into insulating jacket.

EFFECT: possibility of determining time of spontaneous actuation of PI depending on rate of heating of housing of PI.

2 cl, 2 dwg

Description

The invention relates mainly to the field of rocket and space and aviation technology, namely to test equipment, and is intended to determine the response characteristics of various pyrotechnic products (PI) (pyro bolts, pyro locks, pyroenergy sensors, etc.) subjected to heat.

The invention is primarily aimed at solving the question of whether, at a given rate of heating of the PI housing, spontaneous operation can occur, and if so, after what period of time. This problem statement is relevant, for example, in the design of returned spacecraft and the selection of pyrotechnic products for separation means. During ballistic (abnormal) descent of the returned apparatus in case of separation means failure after applying an impulse to detonate the PI, it is necessary to know when the PI will spontaneously trigger from heating when entering dense atmospheric layers.

There is a method for determining the response characteristics of household FIs, namely, a method for determining the fact of non-flammability (lack of spontaneous tripping) of household PIs when exposed to heat and a device for its implementation (Ministry of Internal Affairs of the Russian Federation, State Fire Service. Fire safety standards. "Pyrotechnic products for domestic use. Fire safety requirements Test Methods ”, NPB 255-99, p. 27).

This method is as follows

. A thermoelectric converter (thermocouple) is placed in the center of the thermostat (a device for creating and maintaining a constant temperature). PIs are suspended on a wire near the center of the thermostat so that the thermocouple junction (sensor for measuring temperature) is placed on the wall in the middle of the PI. Turn on the thermostat and heat it with the set heating rate (1-2 ° C / min) to the set temperature (100 ° C). After this, the PI is thermostated (maintained at a constant temperature of the thermostat) for 30 minutes. Tests are performed sequentially with at least three PIs. If during the tests a spontaneous increase in temperature is recorded (both during the process of entering the mode and during the temperature control of the PI), the thermostat is turned off. After completing the tests and cooling the thermostat to room temperature, open the door and inspect the PI.

PIs are considered resistant to heat if in none of the three tests did ignition occur at a given temperature.

PIs are considered unstable to heat if at least in one of the three tests it ignites, and also if there was a spontaneous temperature increase in the process of entering the mode (above the established rate of temperature increase) or in thermostating mode at a given temperature.

A device for implementing this method includes:

- a heater in the form of a thermostat with a working chamber with a capacity of at least 40 cubic meters. dm and a temperature regulator, allowing to maintain a constant temperature in the working chamber in the range from 60 ° C to 250 ° C with an error of not more than 3 ° C;

- thermoelectric converter, made in the form of a thermocouple with a maximum diameter of the working junction of not more than 1.5 mm;

- potentiometer;

- wire with a diameter of 1-2 mm from heat-conducting metal;

- stopwatch with accuracy class not lower than 3.

The disadvantage of this method is that the fact of non-ignition (not fire) PI is determined only for one specific temperature of 100 ° C. However, it is impossible to find out how PI will behave at higher temperatures.

Another disadvantage of the known method is that the holding time in the thermostat is arbitrarily assigned about 30 minutes. For some PIs, this exposure may be enough, but for others it may not. As experiments have shown, the temperature of spontaneous ignition of a charge depends on the heating rate of the PI casing: the higher the heating rate, the higher the temperature to heat the casing by the time of spontaneous operation. With a decrease in the heating rate, the temperature of spontaneous operation decreases and gradually becomes a constant value. The moment of transition to a constant value for each PI is different. It can be either more or less than the test time by a known method. If it is less, then when testing PI, it takes too much time, and if it is more, then testing with a positive result passes an unsuitable PI.

The next drawback is the two-stage heating mode (heating with a varying rate from 1 to 2 ° C / min and holding at a constant temperature). Such a heating mode is not suitable for determining the temperature of spontaneous operation of the PI, since there is an uncertainty in the effect on the actuation of the heating section and the holding section at a constant temperature.

Thus, the known method cannot provide the characteristics of the operation of the PI (time of spontaneous response) when exposed to heat and another approach is needed here, namely, that experimentally determines the dependence of the temperature of the case of PI during spontaneous operation on the heating rate, which is used to judge the time of spontaneous triggering of PI in operating conditions during thermal exposure.

The known method is taken as a prototype, because it is designed to determine the response characteristics of the PI and it is used to heat the test PI, as in the claimed invention.

The disadvantage of the device for implementing the known method is the relatively large inertia of the thermostat and the inability to control the temperature directly of the PI case, since the thermocouple measures the air temperature in the center of the heat chamber near the PI and it takes 30 minutes to keep the temperature of the air and the PI case equal.

Using the known device, it is possible to heat the PI housing only with relatively low heating rates of 1-2 ° C / min. In known emergency situations, the design of spacecraft containing PI, according to calculated estimates, was heated to 500 ... 600 ° C for 5 ... 7 minutes. As a result, the PI spontaneously triggered. Thus, the heating rates of interest are one to two orders of magnitude higher than the heating rates of known devices. When many PIs used in aeronautical and space technology are triggered, fragments that can destroy an expensive thermostat break out, and the known device is simply unsuitable for testing such PIs .

The known device does not provide protection against fragments when the PI is triggered, thereby not ensuring the safety of the work at the proper level.

The known device is taken as a prototype, since it is designed to determine the characteristics of the triggering of PI during thermal exposure, contains a heater, a working chamber and a temperature measuring device, as in the claimed invention.

The objective of the claimed invention is:

- the ability to predict the behavior of PI under thermal loads and in the design of apparatus with safe structural failure;

- the ability to analyze the behavior of PIs in emergency and emergency situations associated with high thermal effects on onboard PIs, for example, during abnormal descent from orbit.

The technical result of the invention is the ability to determine the time of spontaneous operation of the PI, depending on the rate of heating of the housing of the PI.

The technical result is achieved due to the fact that the method for determining the response characteristics of pyrotechnic products during thermal exposure includes the thermal effect on the body of the pyrotechnic product with a given heating rate and the fact of its spontaneous operation being determined, the thermal effect on the pyrotechnic product is carried out with a given constant heating rate of the case until it spontaneous operation and fix the temperature of the body of the pyrotechnic product at which spontaneous arbitrary operation, repeat this operation alternately with other similar pyrotechnic products with a given step in the heating rate until the temperature of the spontaneous operation depends on the heating time of the case, which determines the time of spontaneous operation of the pyrotechnic product during emergency lowering of the standard product using the calculated heating rate of the pyrotechnic body .

The technical result is achieved by the fact that in the device for determining the response characteristics of pyrotechnic products under thermal loads, containing a heater with a working chamber, a temperature measuring device connected to a temperature recorder, an insulating casing, an adjustable power supply connected to a heater, which is made in in the form of a heat radiator and placed along the external contour of the working chamber, while the working chamber is made of a transparent electrically insulating material and those with a heater placed in an insulating jacket, and the temperature measuring means is mounted on the housing of the pyrotechnic product.

The invention is illustrated by drawings (Fig. 1 and Fig. 2).

In FIG. 1 shows an example of a device for determining the response characteristics of PI (explosive pyro-bolt) during thermal exposure. In FIG. 1 adopted the following notation:

1 - PI (pyro bolt);

2 - quartz tube;

3 - thermal emitter;

4 - power supply with adjustable power;

5 - temperature sensor (thermocouple);

6 - temperature recorder;

7 - an insulating casing.

In FIG. Figure 2 presents a temperature chart of spontaneous operation versus time of heating of the test PI cases, on which the results of experimental data on tests of seven pyro-bolts and their average dependence “A” are plotted. The following notation is accepted here: SS - spontaneous operation; MTR - spontaneous operation is absent.

Pyro bolt (1) is placed inside a quartz tube (2), on which a heat emitter (3) is placed, made of, for example, a nichrome wire wound in the form of a spiral on the outer surface of a quartz tube (2) and connected to a power source with adjustable power ( four). A temperature sensor (5) is attached to the pyro-bolt body (1), which is connected to a temperature recorder (6). A quartz tube (2) with an emitter (3) is placed in an insulating protective (against flying apart fragments) casing (7). A quartz tube with a wound nichrome wire is cheap and easy to manufacture and is a disposable replaceable element, replaceable, like PI after each operation.

The emitter (3) can provide rapid heating of the PI housing to temperatures of about 1100 ° C, which allows heating PIs placed in the working chamber (for example, quartz tube 2) with high heating rates, by orders of magnitude higher than the heating rates in ordinary thermostats, for example 100 -500 ° C / min. The temperature sensor (5), for example, a thermocouple, is mounted on the PI housing (1) and connected to the input of the temperature recorder (6).

The proposed method can be implemented using the device shown in FIG. 1 as follows.

On the PI (1), placed in a quartz tube (2), heat is applied by a heat radiator (3) from a regulated power supply (4) by heating the PI case with a given constant rate until the PI spontaneously trips and fix it with a temperature sensor (5) using the temperature recorder (6) the temperature of the PI case at which a spontaneous operation occurs. This temperature is recorded by a sharp jump in temperature in the diagram “temperature - housing heating time”, since the quartz tube (2) with a heat emitter (3) located inside the insulating casing (7), which prevents the PI fragments from flying apart, is destroyed by pyrobolt fragments. The operation is repeated alternately with other similar pyrotechnic products with a predetermined step in the heating rate until the dependence “A” is obtained: spontaneous response temperature (T _csr ) versus the rate (time) of heating the PI case (Fig. 2), which is used to judge the time of spontaneous response of the PI , for example, during an emergency descent of a standard product, using the calculated rate of heating of the PI case.

This can be illustrated by an example of a specific implementation.

Pirobolt No. 1 spontaneously triggered when the temperature reached 180 ° C with a heating rate of 29.7 ° C / min. Pyrobolt No. 2 spontaneously triggered upon reaching a temperature of 160 ° C with a heating rate of 11.2 ° C / min and subsequent exposure for 55 s at this temperature. Pyrobolt No. 3 spontaneously did not work when the temperature reached 125 ° C with a heating rate of 2.2 ° C / min and exposure at this temperature for 1800 s. Pyrobolt No. 4 did not spontaneously work upon reaching a temperature of 125 ° C with a heating rate of 4.6 ° C / min and holding at this temperature for 7200 s. Pyrobolt No. 5 spontaneously triggered when heated to 140 ° C with a heating rate of 3.6 ° C / min and subsequent exposure at this temperature for 540 s. At the same time, pyrobolt No. 6, heated to a temperature of 140 ° C with a heating rate of 5.5 ° C / min, did not work after an exposure of 180 s. Pyrobolt No. 7, heated to 140 ° C with a heating rate of 7.1 ° C / min, did not work after holding for 480 s, and spontaneously worked only after re-heating to a temperature of 160 ° C at a rate of 8.2 ° C / min (at Fig. 2 is marked as No. 7 bis).

From the results obtained, it follows that pyro-bolts No. 1, 2, 5, and 7 bis spontaneously triggered when in the diagram “spontaneous response temperature - heating time of the housing” the heating temperature of the pyro-bolts turned out to be near the averaging dependence “A”. At the same time, only bolts No. 1 and No. 2 were heated at a constant rate, and bolts No. 5 and No. 7 bis were held for a certain period of time until they triggered spontaneously at a constant temperature.

The heating curves of spontaneous pyro-bolts that did not work spontaneously are located on the diagram below the dependence T _csr , although the maximum temperature of some bolts (No. 6 and No. 7) exceeded the temperature of spontaneous operation at large heating times.

Therefore, the fact of spontaneous operation at a given heating time and a given temperature weakly depends on the heating mode and the dependence obtained by the indicated method on T _cav on the heating time of the pyrobolt body can be used to predict the behavior of PI during abnormal heating. It is enough to superimpose the calculated PI heating curve on the dependence T _csr and the point of their intersection will determine the time of spontaneous operation.

It can be seen from the diagram that with an increase in the heating rate, the temperatures T _cs increase sharply. The physical meaning of this phenomenon is that at high heat fluxes only the surface of the PI casing is heated to high temperatures, the charge located inside the casing is heated due to the thermal resistance (thermal inertia) of the structure to the temperature of spontaneous operation only after a certain time.

With a decrease in the heating rate, the averaging dependence of “A” on time becomes more gentle and, starting from a certain characteristic time, turns into a horizontal line. Here, the temperature of spontaneous operation no longer depends on the heating time (stationary region). This characteristic time is different for each PI. In our case, depicted in FIG. 2, this time is 80-90 minutes. On the other hand, the value of T _csr at low heating rates can serve as the upper limit of the temperature range of safe storage temperatures (T _xp ). Thus, this technical solution allows for more reliable obtaining of such operational characteristics as the temperature of safe storage of PI.

During the descent of spacecraft from the orbit of the Earth in emergency situations, high rates of heating of the PI can be realized.

Having such a characteristic of PI as the dependence of T _csr on the rate (time) of heating, we can say when and at what temperature the spontaneous operation takes place.

All of the above confirms the attainability of the claimed technical result.

Claims (2)

1. A method for determining the characteristics of the spontaneous actuation of a pyrotechnic product during thermal exposure, including thermal action on the body of the pyrotechnic product with a given heating rate, characterized in that the operation of thermal action on the pyrotechnic product with a given constant heating rate of its body until the moment of spontaneous operation and fix the temperature the body of the pyrotechnic product, in which a spontaneous operation occurred, this operation is repeated by next to other similar pyrotechnic products with a given step in the heating rate until the dependence of the temperature of the spontaneous operation of the product on the heating time of the body, according to which using the calculated heating rate of the body of the pyrotechnic product, the time of the spontaneous operation of the pyrotechnic product during its emergency descent is determined. 2. A device for determining the characteristics of spontaneous operation of a pyrotechnic product when exposed to heat, comprising a heater with a working chamber and a temperature measuring device connected to a temperature recorder, characterized in that it contains an adjustable power supply connected to said heater, which is made in the form of a thermal the emitter and is placed along the outer contour of the working chamber, while the working chamber is made of a transparent electrically insulating material and e with the heater is placed in an insulating casing, and the temperature measuring means is configured to install a pyrotechnic product on the housing.

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