Method and system for feeding a gas-turbine engine with liquid fuel

Abstract

A method is provided for supplying a liquid fuel to a gas-turbine engine, e.g. aviation engine. It includes selective fuel delivery through several fuel delivery lines for different engine operating modes based on a required engine power, providing, e.g. feeding the engine operating at minimal power with base or traditional for this type of engine fuel through a base fuel delivery line; in other operating modes the fuel is fed to the engine either through conditioned fuel delivery line with preliminary conditioning of base fuel or through both said fuel delivery lines simultaneously with mixing both fuel flows directly before entering an engine combustion chamber, e.g., in a line connecting intake manifold for the base fuel and each individual fuel injector.

Description

FIELD OF INVENTION

A gas-turbine engine is used to present new solutions of this patent as most illustrative example. Similar method and fuel supplying systems can be easily used with any type of engines operating on different liquid fuels.

BACKGROUND OF THE INVENTION

The efficiency of the fuel combustion determines the main operational characteristics of the engine: overall efficiency, noise, emissions, etc. Typical fuel supply systems and systems for injecting and dispersing fuel in the combustion chamber have their own limitations.

Usually to improve gas turbine engine performance a two-stage combustion changing system is suggested. In such type of engine a diffuse combustion mode is used to start the engine or operate it at decreased loads. When gas turbine engine operate at normal loads or continuous working loads a premix fuel/air combustion mode is used that improve emission efficiency.

There are known approaches where to reduce fuel consumption an incombustible liquid, water, is added. At high temperature in the combustion chamber water evaporates and resulted superheated steam significantly increases the pressure in the combustion chamber. Thereby rises the enthalpy of the combustion process as well as overall engine efficiency. In practice such approaches were used with short-lived engines such as engines for military applications. Experiments with gas-turbine engines used for natural gas pumping showed fuel efficiency of up to 25%, but adverse effect on service life. The life of the gas-turbine engine operating at constant loads reduced significantly (in more than 10 times) due to corrosion of working parts as during vaporization there are some liquid water droplets that do not evaporate fast enough. Special treatments of the water to reduce its corrosion activity did not give acceptable results. In case of gas-turbine engines operating at variable loads such as engines for marine and aviation applications the problem of corrosion becomes more aggravated and does not allow using that approach.

In general the technology of utilizing the combustion heat by addition of evaporative liquid is under development by some companies. For example, BMW has announced about development of a special additional turbine to be installed downstream the main turbine and injection of water in the exhaust stream in the inlet of the additional turbine. Similar approaches are under development in some US companies in order to increase the engine efficiency and reduce fuel cost.

SUMMARY OF THE INVENTION

A new method of fuel preparation before injection provides increased working pressure in the combustion chamber while injecting less fuel through inject nozzles of the gas-turbine engine. The fuel supply system provides feeding fuel in exclusively liquid continuous phase whereas a gas or gases are previously dissolved in the fuel. Resulted gas in the fuel under-saturated solution containing sorbed gas/gases in bound form is generate power when engine operates at loads greater than idle load, e.g. at nominal loads or at most continuous working loads.

When injecting gas in fuel solution in the combustion chamber of the gas-turbine engine the conditions prevailing in the combustion chamber provides intensive gas expansion out of the solution thereby results in the finest fuel atomization. In suggested method there are two factors of achieving such results: sharp drop of the pressure at the injector end with hydrodynamic breakage of injected fuel spray and continuous chain physical breakage of the fuel microdroplets due to active gas desorption (“degassing”) from the solution. Continuous degassing prevents microdroplets coalescence. So the conditioned (with dissolved gases) fuel burns close to detonation mode, i.e., with high flame propagation. At the same time the combustion process is stable and controllable.

In accordance with the invention to further increase the efficiency of the gas-turbine engine an incombustible evaporative liquid, e.g., demineralized and filtered water, treated with atomizing gasses under high pressure, is introduced in small amounts in the combustion of light petroleum fuel—kerosene, gasoline or diesel. When water with dissolved gasses, especially a mixture of CO2 with air, is injected in the combustion chamber the dissolved gasses burst out of solution; as a result incombustible liquid quickly evaporate and transfer to a state of superheated steam increasing the pressure in the combustion chamber of the gas-turbine engine.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a schematic view of the system for feeding gas-turbine engine according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A new method of fuel preparation before injection provides increased working pressure while injecting less fuel through combustion chamber nozzles of the gas-turbine engine. The fuel supply system provides feeding fuel in exclusively liquid continuous phase whereas a gas or gases are previously dissolved in the fuel. Resulted gas in the fuel under-saturated solution containing sorbed gas/gases in bound form is generate power when engine operates at loads greater than idling, e.g. at nominal loads or at most continuous loads.

When injecting gas in fuel solution in the combustion chamber of the gas-turbine engine the conditions prevailing in the combustion chamber provides intensive gas expansion out of the solution thereby results in the finest fuel atomization. In suggested method there are two factors of achieving such results: sharp drop of the pressure at the injector end with hydrodynamic breakage of injected fuel spray and continuous chain physical breakage of the fuel microdroplets due to active gas desorption (“degassing”) from the solution. Continuous degassing prevents microdroplets coalescence. So the conditioned (with dissolved gases) fuel burns close to detonation mode, i.e., with high flame propagation. At the same time the combustion process is stable and controllable.

In suggested embodiments of the invention there are three modes of fuel combustion: a) diffusion combustion mode for idle or at low loads, e.g., at taxiing before take-off or after landing; b) base combustion mode with designed fuel/air mixture at increased loads, e.g., at taking-off; c) economical combustion mode at most continuous working loads.

Experiments with gasoline and diesel engine show that with conditioned fuel the fuel efficiency is 15-19% and engine power rises up to 9%. At peak loads engine reaches max torque at lower rpm (in 2.5-3 times) and keeps increased torque (≧80% of max torque) in all further power range. The engine is capable to increase power more rapidly. In case of gas-turbine engine at peak loads, supplying more conditioned fuel gives increased power, thrust.

In base and economical combustion modes when engine power exceeds idle load fuel can be supplied through either base fuel line or conditioned fuel line or both with set flows ratio. Special controllable valves (1, 2) in lines from main fuel pump (11) and valves (3, 4) in lines to inject nozzles are provided to control fuel flows through required lines. To supply the conditioned fuel valve (2), slide-valve (8) in the air supply line and valve (6) in exhaust gases intake (7) line are open. Air from air supply pump (14) is fed to a nozzle of ejector-mixer (15). Air stream ejected through nozzle creates vacuum in the mixing chamber and the exhaust gases are sucked in the ejector-mixer (15). Both flows are merged in set ratio and mixed flow is fed to the fuel conditioner. Experiments showed that 1.5% by weight of both mentioned gases are enough to achieve the abovementioned results.

In accordance with the invention to further increase the efficiency of the gas-turbine engine an incombustible evaporative liquid, e.g., demineralized and filtered water, treated with atomizing gasses under high pressure, is introduced in small amounts in the combustion of light petroleum fuel—kerosene, gasoline or diesel. When water with dissolved gasses, especially a mixture of CO2 with air, is injected in the combustion chamber the dissolved gasses burst out of solution; as a result incombustible liquid quickly evaporate and transfer to a state of superheated steam increasing the pressure in the combustion chamber of the gas-turbine engine.

Experiments confirm estimated parameters of vaporization of finely divided droplets having very small size and high curved surface. According to the Kelvin equation the smaller droplet radius the higher vapor pressure over the droplet surface is: for droplets of super fine size of less than 5×10−3 μm the vapor pressure over droplet surface rises in more than 10 times and at the same dramatically increase the surface of evaporation in more than 300 time. To study the evaporation dynamics of the liquid phase with dissolve gases the following experiments with gas-turbine engine and gasoline engine were carried out: a) a gas mixture (35% CO2+65% Air) were dissolved in water at the gas pressure of 10 bar to form a solution; b) injection of the solution charge (5.5% of fuel charge for gas-turbine engine and 6.5% of fuel charge for gasoline engine) into the combustion chamber. In both cases the evaporation period for the solution charge was less than 0.001 s and the pressure in the combustion chamber increased in 17-22%. This allow to suggest that that the injected charge is dispersed to a “nano” level.

To realize this improvement valve (25) is open and a liquid from a incombustible evaporative liquid source is supplied to a evaporative incombustible liquid conditioner (24) as well as a gas mixture from the ejector-mixer (15) to form a gas in water solution. A charge of gas in water solution according to operating load conditions is injected in the combustion chamber thus increasing enthalpy of the combustion process and engine performance while preventing deterioration of the internal components of the engine due to momentary evaporation of the liquid phase.

Instead of ejector-mixer (15) compact compressors of less than 150 W can be used to supply gas/gases to fuel and liquid conditioners of engines having power over 500 hp. Air compressor (26) is supplied air to prepare base fuel/air mixture and to purge supply lines and nozzles and drain remained fuel and liquid from appropriate conditioners at engine shut-off.

This invention does not described well known practices, such as fuel and gases pressure control. It follows to note that fuel and liquid are supplied to appropriate conditioners at pressure greater than gas/gases pressure in that conditioner.

It is understandable that this invention may be realized in any other modifications and structural designs without departing from the spirit of the invention and within the scope and range of equivalent claims.

Claims

1. A method for supplying a liquid fuel to a gas-turbine engine, e.g. aviation engine, including selective fuel delivery through several fuel delivery lines for different engine operating modes based on a required engine power, providing, e.g. feeding the engine operating at minimal power with base or traditional for this type of engine fuel through a base fuel delivery line; in other operating modes the fuel is fed to the engine either through conditioned fuel delivery line with preliminary conditioning of base fuel or through both said fuel delivery lines simultaneously with mixing both fuel flows directly before entering an engine combustion chamber, e.g., in a line connecting intake manifold for the base fuel and each individual fuel injector.

2. A method in accordance with claim 1 where engine operating modes and fuel delivery lines accordingly are selected based on the most optimal conditions of engine operation, such as a. cold startb. idlec. maximum loadd. most continuous working loade. peak load mode, boost mode

3. A method in accordance with claim 2 which comprises two or more separate fuel delivery lines to the combustion chamber; a traditional, base fuel is fed to the entry point of the combustion chamber through at least one delivery line; this base delivery line is used exclusively in operating modes with low power: cold start mode, idle mode and shut-down mode. In these operating modes the conditioned delivery line is filled with the base fuel and the conditioned fuel from gas charger is returned to the fuel tank using a high pressure pump, installed after the gas charger, and 3-way valve, connected to the delivery lines for the basic and conditioned fuels and installed before the gas charger.

4. A method in accordance with claim 3 wherein the second delivery line is used to feed the conditioned fuel, previously treated with a gas or gas mixture under high pressure and presented as a homogeneous “liquid-gas” solution without a free gas phase; the conditioned fuel then is preferably cooled to −50° C. . . . +25° C. according to operation conditions.

5. A method in accordance with claim 4 wherein the pressure in the conditioned fuel delivery line is kept raised relative to the base fuel delivery line; both lines are connected in the combustion chamber entry point; a mixing apparatus is attached to the outlet of the conditioned fuel delivery line allowing metered mixing two or more flows.

6. A method in accordance with claim 4 wherein the conditioning of the base fuel is performed with filtering from solid particles and preferably cooled and compressed exhaust gases and/or air that are additionally compressed and/or mixed at optimum partial pressure before dissolving into the fuel.

7. A method in accordance with claim 4 wherein oxygen or hydrogen or other gases containing said components, such as methane or natural gas, are used for fuel conditioning.

8. A system for feeding a gas-turbine engine or other type of engines, e.g. spark internal combustion engine or diesel, with liquid fuel comprising: a. a delivery line for base fuel;b. a delivery line for conditioned fuel;c. a gas-charger for fuel conditioning;d. switching valves for switching over between base fuel supply and conditioned fuel supply at different operating modes;e. pressure regulators to control the pressure in the gas-charger;f. gas ejectors to supply the gas or gases to the gas-charger;g. control valves for flushing and replacement of the conditioned fuel delivery lines with base fuel;h. a control subsystem for controlling fuel flows in base and conditioned delivery lines and processes of fuel conditioning and metering depending on engine working load and conditions of operation.

9. A gas-turbine engine operating on liquid fuel which provides addition of non-flammable (e.g., water) or partly flammable (e.g., water-alcohol mixture) evaporative liquid with dissolved gas or gases provided fuel combustion initiation and accelerated evaporation of non-flammable component in order to increase fuel burning enthalpy and engine efficiency.

10. A system for liquid fuel delivery of a gas-turbine engine comprising tanks for liquid fuel, fuel pumps and base fuel delivery lines to transport base fuel to injectors when engine operates at idle and working loads, the system further includes additional fuel delivery lines to transport the conditioned fuel with dissolved gas or gases to engine injectors at increased loads to provide economical combustion. The system is characterized in that it includes a control system providing switching over fuel delivery modes between diffusion combustion at no-load conditions and combustion at increased engine loads according to following options: either exclusively with a base fuel from fuel tanks or exclusively with a conditioned fuel after it activation in a gas charger or with a mix of the base and conditioned fuels. The switching is provided by switch valves installed before the engine injectors to the combustion chamber.

11. An engine, e.g. gas-turbine engine, operating on a liquid or gaseous fuel wherein additional injector nozzles are provided to add a third component—an incombustible evaporative liquid, e.g. water—to the combustion of the fuel mixed with air. The incombustible evaporative liquid is preliminary transferred to a under-saturated “liquid+dissolved gas” solution and thus prepared for ultra-dispersion in the combustion chamber to nano-aerosols of less than 0.005 μm in size. The dissolved gas provides full and momentary evaporation of the incombustible component at injection and transfer of the ultra-dispersed liquid phase to a state of superheated steam with significant pressure increase inside the combustion chamber, increased enthalpy of the combustion process and decreased toxicity of the exhaust gases.

12. An engine in accordance with claim 11 operating on liquid fuel and having at least two independent fuel delivery lines, one of which is used to deliver base fuel, whereas second one is used to deliver conditioned fuel from a gas-charger. The gas-charger is used to prepare a solution—saturation of the base fuel from common to all delivery lines tanks with a gas or gases at increased pressure. The conditioned fuel is supplied to the combustion chamber through the same injector nozzles as for the base fuel, and directly before injector nozzles switching valves are provided in each delivery lines that perform switching of fuel flows to injector nozzles from exclusively base fuel to exclusively conditioned fuel and vice versa.

13. An engine in accordance with claim 12 wherein an additional switching valve is provided at inlet port of the base fuel to the gas-charger for flushing and replacement of the conditioned fuel delivery lines with base fuel at idling or when the engine not in use for a long time.

14. An engine in accordance with claim 11 wherein controllable valves are provided in a line for delivery of the incombustible evaporative liquid, one valve at the beginning of the line and another one just before the injection unit to the combustion chamber. The incombustible evaporative liquid delivery line is also connected to the compressed air source for air blasting of the delivery line from remained fuel at engine shut-off.

15. An engine in accordance with claim 14 wherein the conditioning of the fuel and incombustible evaporative liquid is performed in special gas-chargers with gases dissolving in fuel liquid phase to form a under-supersaturated solution providing that a mixture of gases, e.g. air and exhaust gases, is supplied to the gas-chargers at increases pressure using gas ejectors; the pressure is controlled with pressure regulators having feedback loop with gas sectors of the fuel gas-charger and evaporative liquid gas-charger; the pressure regulators and high-pressure gas ejectors operate in relay mode, preferably, using pulse-frequency modulation.