RU2065069C1 - Method of ensuring stable combustion in liquid-propellant rocket engine - Google Patents

Abstract

FIELD: liquid-propellant rocket engines. SUBSTANCE: zone of combustion is created at propellant lead when one component is fed to combustion chamber by shutting off several injectors temporarily by one of propellant component. To this end, pyropots are fitted in injectors which are burnt out in course of launch, or easily fusible elements are fitted in injector including those made of Wood's alloy or indium alloy; neutral gas may be also fed to injectors. EFFECT: enhanced efficiency. 6 cl, 4 dwg

Description

 The invention relates to the field of liquid-propellant rocket engines (LRE), and specifically to ensuring sustainable combustion in a LRE.

 Ensuring sustainable combustion in the rocket engine (in the traction chamber, in the gas generator) is one of the problems that the developers of the rocket engine have to solve. Instability manifests itself in spontaneous oscillations with a large amplitude of parameters that determine the working process of the rocket engine (pressure, speed, gas temperature, etc.). Of particular danger is the high-frequency instability, which is characterized by the occurrence of gas oscillations in the combustion chamber and gas generator with a frequency of over 1000 Hz at the starting mode, which leads to the destruction of the material part (Cosmonautics: Encyclopedia. M. Sov. Encyclopedia, 1985, article "Instability of the working process") . As a rule, high-frequency combustion instability occurs in the LRE launch mode.

 A known method of ensuring the stability of combustion in a rocket engine, including the creation of a damping gas-liquid volume in the combustion zone (combustion chamber, gas generator) (Instability of combustion in a rocket engine. Transl. From English. M. 1975, S. 621-625).

 There is a method of ensuring sustainable combustion in a liquid propellant rocket engine, including the creation of a combustion zone when starting up ahead of the supply to the combustion chamber of one of the fuel components by temporarily blocking nozzles along one of the fuel components (M.I. Shevelyuk. Theoretical principles for the design of liquid propellant rocket engines. M. Oborongiz, 1960 , pp. 616-618, 620-623 (prototype).

 However, this method, designed to create at the initial moment a vapor-gas (drip-liquid) cloud-damping volume, is not effective in the process of reaching the nominal mode.

 The invention solves the technical problem of creating a simple and effective way to ensure sustainable combustion in the liquid propellant rocket engine in the process of output in nominal mode. This problem is solved due to the fact that in the method of ensuring stable combustion in the liquid propellant rocket engine, which includes creating a combustion zone when starting to feed one of the fuel components by temporarily blocking the nozzles along one of the fuel components, according to the invention, the overlap is carried out on the part of the nozzles. Overlapping nozzles can be carried out by installing pyrosoils in them, which burn out during the start-up process, in addition, overlapping can be achieved by installing fusible elements, including those made of Wood alloy or indium alloys, in addition, overlapping nozzles can be carried out by supplying neutral gas to them, which can use nitrogen.

 From the application of the invention, a technical result is expected, consisting in increasing the reliability of the liquid propellant rocket engine in the starting mode in the process of reaching the nominal mode.

 Let us explain the essence of the invention with a specific example of its implementation, in relation to an engine of the RD-107 type, installed on the Vostok and Soyuz launch vehicles. The combustion chamber of this rocket engine contains a nozzle head (Fig. 1) with a central inlet pipe 1, a cover 2, and two flat bottoms 3 and 4, in which 277 two-component 5 and 60 one-component 6 centrifugal nozzles are placed, with a tangential supply of liquid oxygen (oxidizing agent) and kerosene (fuel). The nozzle arrangement is shown in FIG. 2, and the design of the nozzles in FIG. 3, 4. Liquid oxygen enters the nozzles from the upper cavity of the head through pipe 1, and kerosene from the periphery of the head after passing through the chamber (Fig. 1 4 are borrowed from the book: Cosmonautics / Encyclopedia. M. Sov. Encyclopedia, 1985, p. 426).

To implement the proposed method, when assembling the engine into the channels of the oxidizer nozzles occupying a sector with a central angle α (in a specific example, 60 ^° ), cylindrical end-face burning cups are inserted tightly using glue. In the process of prelaunch preparation, a pyro-igniter is inserted into the chamber (combustion zone) of the chamber (according to the operational and technical documentation). When the engine is turned on, the electric commands to open the fuel valves and activate the pyro-igniter are given in a certain sequence determined by the regular start-up sequence. Oxidizer and fuel come to the nozzles, which are mixed in the working space (combustion zone), and the mixture ignites (from the pyro-ignition device), forming high-temperature combustion products that enter the jet nozzle. Moreover, in that part of the chamber space where pyrochecks are installed in the nozzles, the oxidizing agent does not enter, but only the fuel arrives in atomized form, forming a gas-liquid volume filled with evaporating drops (kerosene). This volume acts as a damper in which the vibrational energy generated by the combustion process in the rest of the chamber is dissipated, which prevents the appearance of high-frequency pressure pulsations.

 From the triggering pyro-ignition device, the pyro-cups installed in the nozzles are also ignited. They burn out after about 15 s (which corresponds to the time the engine reaches its rated operating mode according to the standard start-up scheme), opening up access to the oxidizer in the combustion zone of the chamber through all nozzles, and the engine enters into the calculated mode. In this mode, high-frequency ripple in the camera does not occur.

 Note that the composition and dimensions (length) of the nozzle pyros, as well as the places of their installation, are first calculated and then refined experimentally. Instead of pyrosheels, low-melting (for example, plastic) inserts designed for burnout during engine start-up can be installed in nozzles, or nozzle channels can be fused with low-melting compositions (Wood, indium alloys, etc.), counting on their removal when the engine is switched on for due to heat from the combustion zone or due to heating with fuel coming from the cooling path of the chamber. Of all these methods, the use of nozzle pyrosheets seems to be the simplest and most convenient way, providing a stable, controlled start. (The applicability of other methods is limited mainly by engines with a short-term output to rated mode up to approximately 3 s).

 Instead of mechanical blocking of the nozzles, a gas-dynamic method can be used, including filling the nozzle channels with neutral gas (nitrogen, helium). In relation to the nozzle head of the RD-107 engine described above, this method can be carried out as follows. During the start-up process, simultaneously with the use of the pyrotechnic device, they supply (for example, from a special cylinder) gaseous nitrogen under pressure to the nozzle head oxidizer cavity through the nozzle 7 located on the periphery of the cover 2. Nitrogen fills the part of the oxidizer cavity adjacent to the nozzle and enters the corresponding nozzles into the oxidizer channels , which prevents the entry of oxygen into them from the central pipe 1. After a time corresponding to the output of the engine to the nominal mode according to the standard scheme, Chew of nitrogen into the cavity of the head (purging the cavity) is stopped. This operation can also be carried out automatically at a certain excess of oxygen pressure over nitrogen pressure in a purge line equipped with a check valve.

 The technical result from the use of the invention is to increase the reliability of the LRE by preventing high-frequency oscillations of the gas in the combustion zones (combustion chamber, gas generator) in the startup mode.

Claims (6)

 1. A method of ensuring the stability of combustion in a liquid propellant rocket engine, which includes the creation of a combustion zone when starting up ahead of the supply to the combustion chamber of one of the fuel components by temporarily blocking the nozzles along one of the fuel components, characterized in that the overlap is carried out on the part of the nozzles.  2. The method according to claim 1, characterized in that the nozzle overlap is carried out by the installation of pyroshears in them, which burn out during the start-up process.  3. The method according to claim 1, characterized in that the nozzle overlap is carried out by installing fusible elements in them.  4. The method according to claims 1 and 3, characterized in that the low-melting elements are made from an alloy of Wood or from indium.  5. The method according to claim 1, characterized in that the nozzles are shut off by supplying neutral gas to them.  6. The method according to claims 1 and 5, characterized in that nitrogen is used as a neutral gas.

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