RU2239621C1 - Method of preparing charge of blended solid rocket fuel - Google Patents

Abstract

FIELD: rocket fuels.

SUBSTANCE: method comprises formation of charge at temperature of fuel body by 10-20^оС below curing temperature and curing under pressure. Press mold, prior to be filled, is heated for 0.5 to 12 h at temperature by 5-10^оС superior to molding temperature and charge is then formed in press mold heated with air supplied under casing or flexible jacket of press mold at temperature by 10^оС superior to molding temperature.

EFFECT: improved quality of charge regarding its solidity and equilibrium temperature, and excluded undesired pressure surge during curing.

2 dwg, 1 tbl

Description

The invention relates to the field of manufacturing a charge of a rocket engine (RD) from a mixed rocket solid fuel (SRTT), and in particular to a technology of molding and solidification of a charge under pressure.

An analysis of domestic and foreign patent literature established that a method of forming charges is known (French patent No. 2376094), which involves pouring cold fuel mass into a cold mold, followed by heating the fuel mass, mold and piston, forming a charge by immersing the piston in the cavity of the press - forms and solidification of a charge under pressure.

The main disadvantage of this method is the high probability of formation of defects in the charge in the form of air inclusions as a result of air collapse when filling a cold mold with a cold fuel mass, due to the high rheological properties of the mass at low temperature.

There is also known a method of manufacturing a charge of SRTT according to the patent of the Russian Federation No. 2179543, which is taken by the authors as a prototype, providing for the formation of a charge at a temperature of the fuel mass 10-20 ° C below the curing temperature, curing the charge at a temperature of 65-85 ° C and pressure in the press form 1.5-6.0 MPa.

The disadvantages of the prototype are:

1. The operation to prepare the mold for filling (depressurization of the mold, docking it with the molding machine, etc.) without preheating, especially after transporting it to the molding phase in the winter, leads to condensation of moisture from the surrounding air to the inner surface of the mold due to the negative temperature difference between the mold material and the ambient air. Due to contact with moisture, the properties of the fuel in the boundary layer with the housing deteriorate.

2. Filling the mold without preheating and without heating during molding leads, firstly, to a decrease in the temperature of the fuel mass in the mold due to heat transfer from the fuel mass to the unheated wall of the mold and, as a result, to an unaccounted pressure increase in the mold when it is heated during the curing phase to a temperature of 65-85 ° C and to a change in the equilibrium temperature of the charge. Secondly, it leads to a deterioration in the flow conditions of the fuel mass in the mold due to its cooling in the wall layer with the housing, which increases the likelihood of defects in the charge.

The technical task of the invention is to ensure the quality of the charge in terms of solidity, in equilibrium temperature and the elimination of an unaccounted pressure increase in the mold during curing and deterioration of the fuel properties at the border with the housing due to the heating of the mold before molding and its heating by air during molding.

The proposed method of manufacturing a charge SRTT includes forming a charge from the fuel mass and solidifying the charge under pressure. In this case, charge formation is carried out at a temperature of the fuel mass of 10-20 ° C below the curing temperature.

The technical result is achieved as follows.

The charge is formed from the fuel mass by filling the mold with the fuel mass while constantly heating the mold with air supplied under the casing or flexible cover of the mold with a temperature 10 ° C higher or equal to the temperature of the fuel mass. Before charge formation, the mold is prepared by heating it at a temperature of 5-10 ° C above the temperature of the fuel mass for 0.5-12 hours.

In the proposed method, heating the mold before molding and heating it during molding are provided to exclude an uncalculated increase in pressure during curing, to exclude the formation of defects in the charge due to cooling of the fuel mass in the mold and to prevent deterioration of the fuel properties at the border with the housing beyond moisture condensation on the inner surface of the mold before molding.

Based on these conditions, the temperature of heating the mold before molding is selected 5-10 ° C above the temperature of the fuel mass. If the temperature difference between heating and fuel mass is less than 5 ° C due to the small temperature difference, the task is not fulfilled - the mold does not warm up to the required temperature. With a difference of more than 10 ° C, a deterioration of the fuel property at the boundary with the housing is possible due to the entrainment of volatile components from the composition of the fixing layer at elevated temperatures.

The duration of heating the mold before molding (τ) depends on the initial temperature of the mold (T _n ) before heating from the temperature to which it is necessary to warm the mold before filling (T _to ), from the temperature of the coolant (T _t ) during heating and is determined from the graphical dependence shown in figures 1, 2. The dependencies are built separately for each type of charge according to the data obtained by calculation, based on the geometric dimensions, thermophysical properties of the mold, fuel and heat transfer coefficient from the heat carrier Fir to the mold.

The temperature to which it is necessary to warm the mold before filling T _to , in turn, is calculated by the formula:

where T _with - the temperature of the fuel mass in the mold by the end of the formation of the charge, ° C;

T _f - temperature of the fuel mass, ° C;

M _s , M _p - mass of fuel in charge and mold, respectively, kg;

With _t , With _p - the specific heat of the fuel and the material of the mold, respectively, kcal / kg

In the process of charge formation, it is proposed to constantly heat the mold with air supplied under the casing or flexible cover of the mold with a temperature 10 ° C higher or equal to the temperature of the fuel mass. When the temperature of the heating air (T _in ), below the temperature of the fuel mass, there is a decrease in the temperature of the fuel mass in the mold by the end of molding, which leads to an uncalculated increase in pressure during charge curing. Heating a mold with an air temperature above 10 ° C than the temperature of the fuel mass leads to an increase in the equilibrium charge temperature.

Examples of specific performance of the method are given in the table. In options 1-7, the initial temperature of the mold before heating T _n = 25 ° C (curves with a solid line in figure 1), the mass of fuel in charge M _s = 650 kg, the mass of the mold M _p = 900 kg, specific fuel heat capacity C _t = 0.338 kcal / kg, mold C = 0.105 kcal / kg. Options 8.9 differ from options 1-7 by the initial mold temperature before heating, which is T _p = 15 ° C (see curves with a dashed line in figure 1). In options 10-12, in contrast to options 1-7, the mass of fuel in the charge M _s = 60 kg, the mass of the mold M _p = 150 kg. The curve of the mold temperature during heating before molding for options 10-12 is shown in figure 2.

From the data of the table it can be seen that the manufacture of the charge according to the proposed modes of the method (options 1, 2, 8, 11) provides a high-quality charge. The deviation of the process parameters beyond the limits provided by the method leads to a deterioration in the charge quality in terms of solidity (options 3, 10, 12), to an uncalculated increase in pressure during curing (options 3, 6, 9, 10, 12), to an increase in the equilibrium charge temperature (options 4, 5, 7) and to deterioration of fuel quality in the boundary layer with the body (options 4, 5, 9).

The proposed method of manufacturing a charge SRTT with a positive result has passed an experimental test at the plant. O.M. Kirova. The method provides the manufacture of high-quality charges SRTT.

Claims (1)

A method of manufacturing a charge of mixed solid rocket fuel, comprising forming a charge from a fuel mass and curing the charge under pressure, wherein the charge is formed at a temperature of the fuel mass 10-20 ° C. below the curing temperature, characterized in that the charge is formed from the fuel mass by filling the mold with fuel mass while constantly heating the mold with air supplied under the casing or flexible cover of the mold with a temperature 10 ° C higher or equal to the temperature of the fuel mass, before ormovaniem charge carried preparing the mold by warming it at a temperature 5-10 ° C above the fuel mass temperature for 0.5-12 hours.

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