The present invention generally relates to turbofan propulsion systems for aircraft.
Aircraft gas turbines and ramjet engines are widely used propulsion systems with excellent figures of specific thrust in kgf/kg and specific fuel consumption per unit of thrust per hour in kg/kgf*hour.
The design of ramjet engine (aero thermodynamic duct), a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust, is the simplest among all thermal engines. The efficiency of ramjet engines is the highest among all other thermal engines. However, their main disadvantage is they produce no thrust when stationary (no ram air) and are most efficient only at supersonic speeds. Therefore, ramjet-powered vehicles require an assisted take-off, and are pre-accelerated to the speed of sound using turbojet engines in aircraft, or using a rocket booster in missile.
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine, consisting of a rotating gas compressor, a combustor and a compressor-driving turbine. The thermodynamic cycle of a gas turbine engine consists of atmospheric air flows through the compressor that brings it to higher pressure; energy is then added by injecting fuel into the air and igniting it so that the combustion generates a high-temperature flow; this high-temperature pressurized gas enters a turbine, producing a shaft work output in the process, used to drive the compressor; the unused energy is dispersed in the exhaust gases.
The manufacturing cost of gas turbines is higher than that of other thermal engines.
There are axial, radial, tangential and transverse (lateral) types of gas turbines. Tangential jet turbines are of greatest interest because they can operate without rotor blades. In tangential jet turbines, the torque on the rotor is created by a reactive force of the tangentially directed outflow jet from rotating nozzles.
In the 20th century, several designs of tangential turbofan jet engines were developed. The following prior arts have been used by the present inventors as analogues and prototypes in the development of the present invention.
One of such turbines is Rotary Jet Reaction Turbine (U.S. Pat. No. 43,336,374A), a jet type engine that includes a rotor through which air is drawn and compressed by centrifugal force with the air thus heated and compressed being mixed at the periphery of the rotor with fuel to ignite the same and establish a jet which causes the rotor to rotate. In some cases the air may be precompressed prior to its delivery to a hollow shaft from which it travels radially outwardly through hollow spokes for compression and heating prior to its mixture with fuel that is introduced through a small tube extending through a corresponding one of such hollow spokes. The resulting combustion gases are directed through guides onto turbine buckets on a second rotor which rotates in a direction opposite to that of the air and fuel conducting rotor and the exhaust gases are discharged in a direction extending parallel to the axis of rotation, i.e., sideways. A common output shaft is coupled to these two oppositely rotating rotors for powering, for example, an automobile with energy derived from both such rotors.
The advantage of the described engine is the constructive integration of the centrifugal compressor located in the spokes of the turbo wheel with the turbine rotor. Design complexity and necessity of torque synchronizing are the disadvantages of such engine.
The invention according to patent Thermal Engine with Rotating Nozzles (FR934755A) describes a rotary turbine with rotating nozzles, in which thrust is tangentially applied to the rotor, characterized by the use of combustion products as the working fluid, characterized by the arrangement of the combustion chamber in the plant, wherein the combustion chambers being formed at least partly in the turbine rotor or in another rotating part of the plant, and the combustion chamber contributes to the driving force by creating reactive thrust.
The engine according to patent Rotary Turbine Engine of the Reaction Type (WO2000039440A1) is a a rotary turbine engine of the reaction type, comprising an impeller with shaped blades, an impeller rotation axis, an inlet of the fluid between the blades, combustion chambers between said blades, and a fluid shaped outlet. Combustion chambers and nozzles are fixed on the rotor. A compressor is mechanically connected to the rotor for compressing air within the air intake. Fuel is supplied to the combustion chambers through fuel lines and nozzles from the fuel pump.
The torque in a tangential turbine is created by reactive thrust force of hot gases flowing out of the tangentially directed nozzle(s). As a result the rotor rotates around its axis. The thrust force performs the work equal to the thrust force multiplied by the distance traveled by the nozzle. The higher the velocity of the gas flowing out of the nozzle, the higher the efficiency of thermal energy conversion into mechanical energy. The efficiency of a jet engine substantially increases when the flowing gas velocity exceeds the speed of sound.
The efficiency of the tangential turbine increases when the circumferential speed of the rotating rotor with nozzles becomes supersonic.
Considering all of the above, the present inventors have developed a turbofan propulsion system, based on a reactive tangential turbine, with increased efficiency, simplified design, reduced manufacturing costs and increased service life.
The present invention is a turbofan propulsion system, based on a tangential gas turbine that is structurally a part of the propulsion system's centrifugal compressor, wherein the gas turbine's combustion chambers with nozzles are placed to rotate around a larger radius circle at a supersonic circumferential speed, and the fan blades are placed to rotate around a smaller radius circle at a subsonic circumferential speed, therefore increasing the efficiency of the propulsion system. The said turbofan propulsion system is distinguished by the following features:
The present invention provides a tangential turbofan propulsion system, comprising a rotor 1 and a hollow shaft 2 placed to rotate around an axis of rotation (
A plurality of at least two identical ramjet channels 5 are rigidly placed inside the rim 3 along its circumference (
Each ramjet channel 5 comprises an air intake 9 with a centrally placed body-fairing 10 and an annular diffuser 11, a combustion chamber 12, a fuel supply channel 13, a spark plug 14, the nozzle 7 (De Laval-type nozzle) (
The ramjet channel 5 is a variable cross-section pipe with two successive constrictions and the said nozzle 7 at the channel's back end (
The body-fairing 10, while in its rear position opens up the air intake 9 for the air incoming from the compressor 19 into the combustion chamber 12 (
At a supersonic speed of the oncoming airflow, the dynamic pressure applied to the body-fairing 10 pushes it back by overcoming resistance of the spring 20, and automatically opens up the air inflow from the air intake 9 to the combustion chamber 12. In this mode, the engine operates as a scramjet: the air is compressed by shock waves 21 to a high degree of compression, the airflow velocity inside the chamber 12 becomes supersonic, the combustion of fuel in the combustion chamber 12 is of detonation-type, the speed of the combustion gas outflow through the critical section of the ramjet is supersonic, and the De Laval-type nozzle 7 further accelerates the exhaust gases and increases the efficiency of the propulsion system (
The propulsion system's starting compressor 19 has two stages: axial and radial. The said compressor is rigidly attached to the shaft 2 and rotates with it.
The axial part of the compressor 22, is a an air intake forward open in the direction of motion. Oblique profiled blades 23 are placed on the inner surface of the air intake bowl, capturing air during rotation, compress it and direct it to the radial stage of compressor through windows 24 in the side walls of the said bowl-shaped air intake (
Each window 24 passes the compressed air into the radial channel 18 of the compressor's second stage. The radial channels 18 pass placed within the radial spokes 4 of the rotor, are in essence the walls of each radial channel 18, thus forming one rigid radial spoke 4 (
The walls of the radial channel 18 of the radial spoke 4 are so shaped that each spoke forms an aerodynamically efficient body, fan blade 25, thus reducing the weight of the propulsion system. In addition, the thin metal walls of the radial channel 18 of the compressor 19 can effectively and quickly cool down the hot compressed air inside the radial channel 18, by transferring heat from the channel to the cold air flowing around the fan blades 25 (
In the present embodiment, the propulsion system is managed electronically and/or electromechanically and/or mechanically, by controlling the amount of fuel getting into the fuel channels 13 and amount of air getting into the radial channels 18. The flow of fuel into the fuel channel 13 and the corresponding combustion chamber 12, and the flow of air into the same combustion chamber through the radial channel 18 of the compressor are managed simultaneously. This is done to reduce the loss of mechanical energy on air compression, preventing its supply into the idle combustion chambers 12.
The said propulsion system must be start-assisted by an external source of mechanical energy, for example compressed air. When the compressed air is supplied through the air intake 22 onto the blades 23, the compressor 19 itself serves as a starter. The compressed air from the said air intake flows through the windows 24 into the radial channels 18, then through the side orifices 17 into the combustion chambers 12. At this time, the combustion chambers are closed from the side of the air intakes 19 by their respective body-fairings 10, forcing the compressed air flow out of the nozzles 7 creating a jet thrust. The thrust force is directed tangentially relative to the rotor rim 3 and causes the rotor 1 to rotate in the opposite direction.
When the said rotor reaches sufficient rotational speed, the compressor starts capturing air through the air intake 22 and compresses it in the radial channels 18 under the centrifugal force. As a result of the air moving into the distal part of the narrowing radial channels 18, the air is getting heated and compressed. At the end of the radial channels 18, compressed and heated air passes through the narrow side orifices 17 into the combustion chambers 12 of the turbine (
When the rotor 1 with the radial fuel channels 13 rotate, a pressure gradient is created in the said channels by a centrifugal force, directed from the center of rotation to the periphery. Thus, a significant pressure is created in front of the injectors 16, and a rarefaction is created at the distal end of the fuel channels 13. As a result, the fuel is being sucked out of a fuel tank (not shown) through the hollow rotor shaft 2. The rotating radial fuel channels 13 act as a centrifugal fuel pump. The higher the angular speed of the rotor the more fuel is supplied to the combustion chambers 12.
The fuel is injected under pressure from the radial fuel channels 13 through the injectors 16 into the chambers 12 and ignited by the spark plug 14 (
Displaced by the new portions of air coming under pressure from the radial channels 18 of the compressor 19 into the combustion chambers 12, the combustion gases move along the pressure gradient through the ramjet channels 5 and are being ejected through the nozzles 7 (
When flowing out of the nozzles 7, the combustion gases acquire higher than supersonic velocity and some momentum. According to the law of conservation of momentum, the said nozzles receive an impulse equal in magnitude, but opposite in direction. This impulse is realized in form of thrust force applied to the nozzles 7, and therefore, to the rotor 1.
Thrust force from the plurality of nozzles 7, tangentially directed relative to the rotor's 1 circumference, causes it to rotate in the direction opposite to the combustion gases jet.
As the angular velocity of the rotating rotor increases, the linear circumferential speed of the combustion chambers 12 with air intakes 9 increases accordingly. When the circumferential speed of the rotor becomes supersonic, the oncoming air flow pressure in the air intakes 9 begins exceeding the pressure of the air flow coming from the radial channels 18 of the centrifugal compressor 19. When the force of the dynamic air pressure applied to the body-fairing 10 exceeds the force of the centrifugal air pressure, the spring 20 begins compressing, the said body-fairing moves backward and opens the air inlet to the combustion chambers 12 from the air intakes 9 (
Air flowing at supersonic speed creates on the body-fairing 10 the shock waves 21, which are then reflected from the diffuser 11 and the channel 5 walls, moving along the combustion chambers 12 at supersonic speed (
Simultaneously, with the increase of the angular velocity of the rotor, the fuel pressure in the injectors 16, created by the centrifugal force in the radial fuel channels 13, increases.
The fuel consumption through the said injectors also increases. As a result, the speed of the combustion gases ejected out of the combustion chambers 12 through the nozzles 7 increases significantly, thus increasing the power on the shaft 2, and the turbine changes its operational mode from starting to working. The air-fuel ratio of the mixture entering the combustion chamber 12 is adjusted in advance and remains constant (optimal) regardless of the angular speed of the turbine. Since both the pressure of the fuel in the injectors 16 and the pressure of the air entering the combustion chambers 12 are a function of the angular velocity of the rotor, their said ratio is preserved. This ensures the most complete combustion of fuel and efficient operation.
The relative spatial orientation of the body-fairing 10 and the diffuser 11 is so chosen that the shock air waves 21 from the said body-fairing move towards the said diffuser, and, reflecting from its oblique walls, are focused behind the diffuser at the spatial point 26, which lies on the axis of the combustion chamber 12 (
For efficient atomization of fuel in focused shock air waves, it is recommended using the following type of injectors. The radial fuel channel 13 is plugged at the combustion chamber end, and has a through hole 31 near its plugged end, coaxial with a longitudinal axis of the combustion chamber 12 and spatially coinciding with the focus point 26 (
The hot combustion gases flowing out of the nozzles 7 are directed at some sharp angle a to the tangent of the rotor's circumference, so that the said gases mix with air captured by the fan blades 25 (
The said fan blades 25 are made of metal of aerodynamic shape: streamlined profile, optimal angle of attack, twist of the blades (change in angle of attack depending on the radius). Therefore, through the blade's metal walls the heat exchange effectively occurs between the heated air inside the radial channel 18 structurally integrated with the said blades and the cold outside air, blowing around the blade. Outside air, passing through the turbofan, heats up and increases in volume (
The heated air inside the channel 18 is being cooled, thus reducing its volume and, consequently, its pressure. The resistance to air compression within the said channel decreases and the efficiency of the centrifugal compressor 19 increases. It captures a larger mass of air. A larger mass of air of the same pressure enters the combustion chambers 12, thus the mass, and, hence, the volume of combustion products increases. As a result, the specific power of the engine and the propulsion thrust increase.
Due to the placement of fuel channels 12 inside the blades 25, the fuel inside the said channels is getting preheated. The warmer fuel, due to a decrease in viscosity and surface tension, is injected in smaller drops and burns more completely.
The power output control of the propulsion system is performed by managing the supply of fuel to the combustion chambers 12.