RU2633764C2 - Supersonic combustion ramjet fuel - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention describes the fuel for supersonic ramjet engine (SRE) on the basis of the synthetic high-density fuel T-10. The combustion promoter-tert-butyl hydroperoxide and antioxidant-ionol (wt %) fuel T-10 95.495-94.492 was additionally introduced into the fuel; tert-butyhydroperoxide 4.5-5.5; ionol 0.005-0.008.

EFFECT: creation of the fuel for hypersonic ramjet engine with extended storage times, increased normal combustion rate, and the reduced ignition delay period, when burning in the turbulent flow in the hypersonic ramjet engine chamber, while introducing in it the tert-butyl hydroperoxide as the combustion promoter and ionol as the antioxidant.

1 ex, 1 tbl

Description

The present invention relates to fuels for jet engines, in particular to compositions of hydrocarbon fuels containing additives (combustion promoters) that increase the value of the normal burning rate and shorten the ignition delay period of hydrocarbon fuels.

It is known that one of the most effective methods of increasing the normal burning rate and shortening the ignition delay period is the introduction of activating additives into the fuel - combustion promoters [1], which include organic peroxides.

Known additive to hydrocarbon fuel [4], consisting of halogenated hydrocarbon, hydroperoxide (cumyl hydroperoxide or tertiary butyl hydroperoxide), naphthalene or alkyl derivatives of naphthalene and an organic solvent, added to hydrocarbon fuel such as fuel oil, diesel fuel or gasoline in an amount of 1-2 parts per a thousand and improving the starting characteristics of diesel fuel and further improving combustion efficiency. According to the authors, benzoyl peroxide is the least preferred as the hydroperoxide included in the additive. This invention was intended to be used as a fuel additive for internal combustion engines.

Known additive to gasoline and diesel fuel [3], consisting of alcohol, toluene and hydrogen peroxide in a ratio of 16/18/1 to increase the octane and cetane number and increase the efficiency of fuel combustion. The invention was also intended to be used as an additive to hydrocarbon jet fuel.

The closest analogue of the claimed technical solution is "Fuel for a pulse detonation engine" [5]. Having significant advantages over previous analogues, the indicated technical solution has some drawbacks: benzoyl peroxide used in the additive is an aromatic compound that increases the fuel forming ability of the fuel, in addition, this additive is a solid substance, insoluble in hydrocarbon fuels, requiring preliminary dissolution in benzene, which is also an aromatic compound, and, in the case of using this fuel additive for scramjet engine, the burning rate is the dust will decrease due to the formation of soot on the walls of the combustion chamber.

An object of the present invention is to provide fuel for a scramjet with an increased normal burning rate and a reduced ignition delay period when burning in a scramjet chamber by adding an additive consisting of TBHP to it to obtain a hydrocarbon fuel composition for a scramjet based on synthetic high-density fuel T-10 s composition (wt.%):

fuel T-10 95,495-94,492 tert-butyroperoxide 4,5-5,5 ionol 0.005-0.008

A comparative analysis of the technical solution with the known one shows that the claimed technical solution is characterized in that the fuel composition contains 4.5-5.5% TBHP and 0.005-0.008% ionol. TBHP in comparison with benzoyl peroxide has a lower carbon-forming ability and does not require additional dissolution for introduction into the fuel. Also, a fuel composition containing 4.5-5.5% TBHP in comparison with the closest analogue containing 0.7-1% TBHP in the fuel composition [6] has higher rates of normal burning rate and a shorter ignition delay period. Also, the proposed fuel composition T-10 and 4.5-5.5% TBHP has lower concentration limits of ignition in comparison with the previously proposed compositions [6]. The addition of ionol antioxidant 0.005-0.008% to the fuel composition can increase the shelf life, extend the shelf life of the fuel composition and increase the reliability of operation of the scramjet [8, 9].

The fuel composition according to this invention is prepared by directly introducing a calculated amount of a promoting additive and an antioxidant directly into the fuel.

The activating effect of TBHP is due to the replacement of the primary decomposition of hydrocarbon fuel with a more energetically favorable decomposition reaction of the prodononator. According to the literature [2], the decomposition of prodonators occurs with an activation energy of 0.12 - 0.14 MJ / mol instead of 0.37-0.49 MJ / mol in the case of hydrocarbons. In addition, along with the primary decomposition of hydrocarbons, it is possible to replace hydrocarbon radicals with oxygen atoms, which serve as high-temperature ignition centers. Additive TBGP to fuel T-10 affects the increase in acidity of the fuel composition as a whole due to the oxidation of hydrocarbon fuel and slightly reduces the ignition temperature of the fuel composition.

The usefulness of the additive TBHP and ionol to the fuel T-10 and their mass content in the fuel composition TBHP 4.5-5.5%, ionol 0.005-0.008% will become apparent from the following example.

EXAMPLE

Prepared according to this invention, a fuel composition with the following composition (wt.%):

fuel T-10 95,495-94,492 tert-butyroperoxide 4,5-5,5 ionol 0.005-0.008

As a fuel-air mixture, a stoichiometric vapor mixture of a prepared fuel composition based on T-10 fuel with air was used.

The burning activity of the fuel composition was carried out in a laboratory setting to assess the combustion characteristics of hydrocarbon fuels for promising engines [7, 10]. The design of the laboratory setup provides variation by independent process factors: temperature and pressure of the mixture, the amount of injected fuel or mixture (liquid or gas), and also operate from a network with a voltage of 220 V and a current frequency of 50 Hz.

The installation provides the determination of the following combustion characteristics:

- normal flame propagation rates in gas and gas-gas mixtures at initial temperatures from 273 to 600 K and pressures up to 5.0 MPa;

- delays self-ignition of these mixtures at temperatures up to 1000 K in the millisecond range.

The inner surface of the reactor is inert to the substances used and their products of combustion and does not have catalytic and other effects affecting the burning rate of the tested fuels.

The system for preparing and introducing the mixture provides work with both gaseous, including mixed, and liquid fuels.

The facility provides for the possibility of sampling combustion products to analyze their composition using modern physicochemical research methods.

The studied fuel composition was prepared in a measured tank and kept there for better mixing for several hours. The air-fuel mixture was prepared directly in the mixer of the installation, heated to a temperature at which a pre-measured amount of fuel completely evaporates in it, is introduced into the evacuated (or partially filled with air) mixer using a syringe. Given a coefficient of excess air, knowing the molecular weight of the fuel composition and the ratio of the oxidizing agent, calculate its volume, which must be submitted to the mixer. The amount of fuel supplied (its share in the volume of the mixer) is controlled by a change in pressure.

After this, the mixture is introduced into the reactor through a valve with an adjustable bypass duration.

The fuel composition was heated in the mixer to 200 ° C for 20 s, then the fuel-air mixture is introduced through an electromagnetic valve into the combustion chamber with temperatures of 300, 350, 400, 450 ° C.

The obtained experimental data of the normal burning rate and the ignition delay period of the proposed fuel composition for scramjet engine are presented in table 1.

According to the experimental data presented, as the temperature in the combustion chamber increases, the normal combustion rate increases, and the ELV decreases.

It was also experimentally established that with a further increase in the concentration of TBHP in the fuel T-10, the increase in the rate of normal combustion and the reduction in ELVs are very small, but the acidity of the fuel composition increases, which complicates and degrades the operational properties of the fuel composition.

In turn, the addition of an antioxidant - ionol to the fuel composition in an amount of 0.005-0.008% made it possible to increase the shelf life, extend the shelf life of the fuel composition from 6 to 8 months versus 1-2 months without adding an antioxidant.

The presented fuel composition solves the problem of creating a fast-burning hydrocarbon fuel for scramjet engine, with increased retention, based on synthetic high-density fuel T-10.

Information sources

1. Zamansky V.M., Borisov A.A. The mechanism and promotion of self-ignition of promising fuels // Itogi Nauki i Tekhniki. Kinetics and catalysis. - M.: VINITI. - 1989. - T. 19. - S. 87-98.

2. Williams F.A. Combustion theory. - M .: Publishing house "Science" the main edition of the physical and mathematical literature. - 1971. - S. 250-270.

3. US patent No. 4294586, 1981

4. US patent No. 4286969, 1981

5. Patent RU No. 2387701, 2008

6. Patent RU No. 2484123, 2013

7. STO 08151164-0144-2013.

8. Pozina M.E. Hydrogen peroxide and peroxide compounds. - M .: State scientific and technical publishing house of chemical literature. - 1951. - S. 255-270.

9. Shamb U., Setterfield C., Wentworth R. Hydrogen peroxide. - M .: Publishing house of foreign literature. - 1958, S. 445-453.

10. Zabaykin V.A., Kobyzhsky S.A., Petrov M.D. Organization of kerosene combustion in a model scramjet engine // Physics of Combustion and Explosion. - 1992. - No. 4. - S. 18-26.

Claims (2)

Fuel for a hypersonic ramjet engine based on synthetic high-density fuel T-10, characterized in that the combustion promoter is additionally introduced into the fuel - tert-butyl hydroperoxide and antioxidant - ionol to obtain the composition (wt.%): fuel T-10 95,495-94,492 tert-butyroperoxide 4,5-5,5 ionol 0.005-0.008