RU2523510C1 - Method of gas turbine engine afterburning - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed method consists in the fuel feed into combustion chamber or compressor in amount required for its complete combustion. Besides, extra fuel is fed into combustion chamber in amount required for decrease in the temperature of gases in combustion chamber to safe limit (atmospheric supercharging). At activation of said atmospheric supercharging and exiting from the turbine igniter of whatever type is fired at a time.

EFFECT: perfected process.

2 cl

Description

The invention relates to gas turbine engines (GTE) and is intended mainly for helicopters, tanks and warships.

A known method of forcing turbo engines by injection into the combustion chamber or in front of the compressor of water or a mixture of water with fuel (methanol), see Vyunov S.A. "Design and Design of Aircraft Gas Turbine Engines", M., "Mechanical Engineering", 2004, p. 417-419. However, water as a working fluid is not the best option: it has a high heat of vaporization - 2500 kJ / kg, a large heat capacity - 4190 J / (kg · K), a large heat capacity of water vapor - about 2 kJ / (kg · K) (it varies with temperature and pressure). That is, to heat one kilogram of water to water vapor with a temperature of 1400 degrees, it will take approximately (excluding compression) 5519 kJ.

Also known is the "Method of afterburner of a turbo engine" patent No. 2474718, in which a combustible substance is injected. This new method of afterburning for turbo engines by injection into the combustion chamber either in front of the compressor, or into the compressor stage of a combustible liquid or gas is called “atmosphere” (from the Greek “atmosphere” - evaporation). And the fuel intended for cooling the gases in front of the turbine is called "fuel oil".

The objective and technical result of the invention is a safe increase in the power of a gas turbine engine.

To this end, this method of afterburning of a gas turbine engine consists in supplying to the combustion chamber or to the compressor the amount of fuel necessary for its complete combustion in the air entering the engine, and supplying to the combustion chamber additional fuel in an amount necessary to reduce the temperature of the gases in the combustion chamber to a safe the limit.

This increases the heat in the combustion chamber, and increases the amount of working fluid for the turbine. As a result, the angular velocity of rotation of the turbine and the torque on its blades increase.

An almost optimal working fluid for this method is the substance that is always present on the helicopter - kerosene: the heat of vaporization is about 220 kJ / kg (i.e. 11.4 times less), the half heat capacity is 2.1 kJ / (kg · K) , the heat capacity of the vapor is approximately 1.65 kJ / (kg · K). That is, to heat one kilogram of kerosene to a state of steam of 1400 degrees, you need about 2575 kJ. True, water has a larger coefficient of increase in volume during evaporation. But kerosene at a temperature of 1400 degrees can undergo cracking and thermal decomposition to hydrogen. That is, instead of one molecule, 15-16 molecules can be formed, and, accordingly, the volume of the working fluid and its flow rate will increase.

In this case, by the way, a non-hazardous side effect can occur: a thin layer of graphite can form on the blades and guide vanes of the turbine. It does not affect the operation of the turbine and quickly burns after turning off the atmosphere.

Other flammable liquids may also be used, including liquefied flammable gas, such as ethyl ether, alcohol, propane or chilled methane. And although in this case they need a separate tank for the airplane, they can be fed into the combustion chamber as ordinary fuel if necessary and used in the normal economic flight mode.

It would seem, what are the advantages of this afterburner method, because an evaporating agent (fuel instead of water) will need about twice as much? But the fact is that, firstly, there is more working fluid, which already increases engine thrust, and secondly, if instead of one water molecule we take an equivalent amount of kerosene with the averaged formula C ₁₃ H ₂₈ , then it theoretically can decompose to carbon and 2.87 hydrogen molecules. Yes, even with a slight exothermic effect (for methane - 4.67 mJ / kg).

But the main advantage of this afterburner method is that it is not necessary to have, for example, a water supply in a helicopter. It may never come in handy. And in case of emergency (for example, if a combat missile hits one of the two engines), you can fly to a place convenient for landing on one engine in the atmosphere mode. In this case, fuel consumption will be several times greater than with the "maximum", but the goal will be achieved.

But this gas turbine engine has one operational feature - with a large degree of gas expansion in the turbine, when the outlet temperature drops below 700 degrees C (the self-ignition temperature of hydrogen), the hydrogen released as a result of thermal decomposition of hydrocarbons can mix with the air and form explosive gas mixture. If this mixture is accidentally or intentionally ignited, a strong explosion will occur. To prevent this, when you turn on the atmosphere, you must simultaneously turn on the ignition device of any type (gasoline burner, gas burner, pyroshashka, etc.) at the outlet of the turbine to the atmosphere. Almost without alterations, an arsonist from flamethrowers can be used. The efficiency of the electric candle is doubtful, since at the exit from the nozzle the hydrogen has not yet mixed with the surrounding air.

Moreover, the ignition device may not burn continuously, but only for a short time to ignite hydrogen, which will then burn on its own until the end of the atmosphere mode.

The supply of additional fuel has several nuances. Firstly, it is not necessary to supply all the fuel to the main nozzles: they are not designed to increase the flow rate up to 10 times, and combustion will be bad - with the formation of products of incomplete combustion, which will reduce the exothermic effect of combustion by about 1.36 times.

But the last circumstance can be used to regulate this seemingly unregulated mode - you can reduce the afterburner power by supplying fuel to the main nozzles in an amount slightly exceeding its stoichiometric amount. At the same time, fuel consumption will be much less.

Secondly, the length of the torch when applying fuel to common nozzles due to the cooling effect of excess fuel can increase dramatically, therefore it is better to supply fuel to a stoichiometric composition (hereinafter referred to as “stoichiofuel”, that is, the amount of primary or secondary, liquid or gaseous fuel supplied to the main nozzles or to the compressor stage and intended to achieve a stoichiometric composition with atmospheric oxygen) to the main nozzles or to the penultimate or penultimate compressor stage. This will cool the incoming air and increase its mass flow rate. Stoichiofuel should not be fed to the beginning of the compressor, otherwise the fuel will be discarded by centrifugal force to the outer shell of the compressor and will enter the combustion chamber in film form.

And the rest of the fuel should be fed to the end of the torch of the main burners (the end of the torch means the end of the zone of almost complete - 95-99% - combustion of stoichiofuel supplied to the main nozzles and to the compressor stage).

Thirdly, when supplying fuel to the compressor stage, it must be ensured that it does not spontaneously ignite there from compression or that the flame does not enter the stage through the combustion chamber. To avoid the latter, it is necessary that in the guide lattice of the last stage there is a narrowing, providing a supersonic flow. Then the flame cannot spread through this section.

Fourth, if the supply of additional fuel is not turned on instantly, then during the transition process, it is possible to achieve a stoichiometric composition for a short time without excess fuel, which will lead to turbine failure. To prevent this from happening, a non-combustible liquid, such as water, must be supplied to the combustion chamber or to the compressor in an increasing amount during the transition period.

The water used may contain antifreeze additives, for example glycols, to prevent freezing and a wetting agent, for example PO-6. To prevent foam from forming in the water tank, water and air can be separated in the tank with a rubber bag. A wetting agent is needed to lubricate the moving parts of the pump. Since the lubricating properties of wetting agents have not been specifically studied, experiments in this direction may be required. It is also possible to use an oil emulsion.

And only after reaching the stoichiometric composition should water be replaced by fuel. It is desirable - smooth, so as not to cause a temporary, and even more so sharp decrease or increase in the supply of cooling agent, as this can lead to either a melting of the turbine or surging of the compressor.

However, a very fast, almost instantaneous supply of stoichiofuel and at the same time fuel oil will not lead to melting of the turbine, since the time of exposure to elevated temperature will be short. Although this increases the likelihood of a breakdown in surge.

EXAMPLE: A GTE combustion chamber has two rows of nozzles. For an emergency increase in power, a stoichiometric amount of fuel (that is, the full use of oxygen available in the air) is supplied to the first row (along the gas path), and such a quantity of fuel is supplied to the second row of nozzles that the temperature of the gases in front of the turbine does not increase, or maybe even decreased (taking into account the increase in the angular velocity of rotation of the turbine.

Claims (2)

1. The method of boosting a gas turbine engine, which consists in supplying to the combustion chamber or to the compressor the amount of fuel necessary for its complete combustion, and supplying to the combustion chamber additional fuel in the amount necessary to reduce the temperature of the gases in the combustion chamber to a safe limit, and when turned on During atmospheric use, an ignition device of any type should be simultaneously turned on at the exit of the turbine into the atmosphere. 2. The method according to claim 1, characterized in that the igniter is a gas burner or pyroshash.