The principle of the turbofan engine The turbofan engine is a branch of the jet engine. From the blood relationship, the turbofan engine should be regarded as a variant of the turbojet engine. Structurally, the turbofan engine is simply a fan installed before (after) the turbojet engine. However, it is the several-page fan in this area that strictly distinguishes the turbojet engine from the turbofan engine. The turbofan engine is also blue with a few pages of fan blades on its own body. Modern military fighters require ever higher maneuverability, and higher thrust-to-weight ratios give the fighters high vertical maneuverability and excellent horizontal acceleration. Moreover, in the wartime, if the airport is damaged by the other party, the fighter can also use the large thrust to reduce the take-off and landing distance of the aircraft. For example, if the F-15A equipped with F-100-PW-100 is partially damaged when the runway of the square machine is partially destroyed, the F-15 can be fully energized to take off at a take-off distance of less than 300 meters. When landing, you can use a 60-degree angle of attack for low-speed leveling. Without a parachute and reverse thrust, a 500-meter runway can be safely landed. A higher thrust-to-weight ratio is what every fighter pilot dreams of. However, the thrust-to-weight ratio of the fighter is limited by the engine in a large degree. If the thrust-to-weight ratio of the aircraft engine is less than 6 or less, the air combat thrust-to-weight ratio of the aircraft is difficult to reach 1, if the thrust-to-weight ratio of the aircraft is forcibly increased. The designed aircraft will pay a considerable price for the voyage, weapon mounting, and strength of the aircraft. For example, the Su-11 fighter designed by the former Soviet Union used the ÐЛ-7Ф-1-100 turbojet engine with a thrust-to-weight ratio of 4.085. In order to achieve a thrust-to-weight ratio of 1, the Su-11's power unit weighs 26.1% of the aircraft's take-off weight. The corresponding price is that the aircraft's combat radius is only about 300 kilometers. In civil passenger aircraft, transport aircraft and military bombers, transport aircraft. With the use of new materials, the fuselage structure of the aircraft is getting bigger and bigger, the take-off weight is getting bigger and bigger, and the thrust requirement for the engine is getting higher and higher. Before the advent of high-speed turbofan engines with large thrusts, one could only solve the problem of insufficient thrust of the engine by using a large aircraft to hang more engines. For example, eight J-57-P-43W turbojet engines were hung under the wing of the B-52G bomber. The engine's single maximum takeoff thrust is only 6,237 kg (spray). If the B-52 was born a few years later, it could not hang so many engines. Now, if you don't consider the reliability of the power system, it is not a bad idea to have only one engine for an airplane like the B-52. The turbofan engine was born in response to people's increasing thrust requirements for aero-engines. Because the easiest way to increase the thrust of a jet engine is to increase the air flow to the engine. First, history In the 1950s and early 1960s, turbojet engines, which were aerodynamics, were quite mature. At that time, the total supercharging ratio of the turbojet engine could reach about 14, and the maximum temperature before the turbine reached a level of 1000 degrees. Under such conditions, the turbojet engine performs a partial energy output to make it possible. At that time, the thrust requirement for the engine was so urgent. It was natural to think of adding a fan to the turbojet engine to increase the windward area and increase the air flow to increase the thrust of the engine. At that time, people found through calculations that with the technical level of the vortex jet at that time, after the turbojet engine was installed with a fan and turned into a turbofan engine, its technical performance would be greatly improved. When the fan air flow of the turbofan engine is as large as the air flow of the core engine (the channel ratio is 1:1), the ground takeoff thrust of the engine is increased by about 40%, and the fuel consumption during high altitude cruise. The volume has dropped by 15% and the efficiency of the engine has been greatly improved. Such a new aerodynamic power with the advantages that turbojet engines can't match has naturally received great attention from the powerful powers of the West. All countries have invested a great deal of manpower, material resources and enthusiasm to study the prototype turbofan engine. The British walked ahead of the Americans on the road originally developed by the turbofan engine. The British Rolls-Royce company has invested considerable energy in developing its "Comverse" turbofan engine since 1948. In 1953, Conway conducted the first interview. After another six years of incision, the "Comverse MK-508" was finalized in September 1959. This eleven-year-old pregnant woman's dystocia has the comprehensive performance of the turbojet engine at that time. "Comverse" adopts the overall structure of the double-rotor front fan. The ratio of the feeder to the ratio of 0.3 is 3.83. The maximum thrust of the ground gantry is 7945 kg, the cruise thrust of the high altitude is 2905 kg, and the fuel consumption at the maximum thrust is 0.735 kg/ In hours/kg, the compressor's total boost ratio is 14, and the total fan boost ratio is 1.90, and the British also used air-cooled turbine blades for the first time on Conway. When Conway finally finalized, the British couldn't wait to put him on the VC-10! Americans are slower than the British in the development of turbofan engines, but their technical starting point is very high. The Americans did not follow the old road developed by the British from scratch. The US Pratt & Whitney Company used its rich technical reserves on the turbojet engine and adopted the core of the internal core of the very mature J-57 as a new turbofan. engine. The J-57 is a turbojet engine designed by the Americans since 1947. It was designed in 1949 and officially put into production in 1953. J57 produced a total of 21,226 units in the production phase, one of the three largest turbojet engines in the world. It has been equipped with F-100, F-101, F-102, B-52 and other models. The J-57 also has a breakthrough in technology. He is the world's first jet engine with a dual-rotor structure. Single-rotor to dual-rotor is a major advancement in jet engine technology. Not only the core engine, but even the fan Pratt & Whitney also used the fairly mature parts, and the long blades of the J91 nuclear-powered jet engine that was revoked were used by Pratt & Whitney as fans of the new turbofan. . In July 1960, Pratt & Whitney's JT3D turbofan engine was born. JT3D's final set-up time is only a few months behind Rolls-Royce's Conway, but the performance is greatly improved. JT3D also adopts the design of double-shaft front fan. The maximum thrust of the ground gantry is 8165 kg, the cruise thrust of high altitude is 2038 kg, the maximum thrust fuel consumption is 0.535 kg/h/kg, the thrust-to-weight ratio is 4.22, the ratio of the channel is 1.37, and the total pressure of the compressor is 1. Compared with 13.55, the total fan boost ratio is 1.74 (the above data is the data of the JT3D-3B engine). JT3D is very useful, and Boeing 707 and DC-8 are all JT3D. Not only in civilian use, but also in military use, JT3D is also very popular. The B-52H, C-141A, and E-3A are all military-type TF-33 of JT-3D. Luo Luo and Pu Hui, among the three major aviation power giants in the world, have successively launched their own first-generation turbofan works. At almost the same time, one of the Big Three also launched its first generation turbofan engine. In the eighth month after Luo Luo launched "Conway", Pu Hui launched the month before JT-3D. General Dynamics has also finalized its first generation turbofan engine CJ805-23. The ground gantry of the CL805-23 has a maximum thrust of 7169 kg, a push-to-weight ratio of 4.15, a duct ratio of 1.5, a compressor boost ratio of 13, a fan boost ratio of 1.6, and a maximum thrust fuel consumption of 0.558 kg/h/kg. Like Puhui, General Dynamics also developed its own turbofan engine based on the existing turbojet engine. The core engine used as the new turbofan is the J79. J-79 and the design began in 1952, and in 1956, a total of more than 16,500 units were produced. Like the J-57, he is one of the three highest-volume turbojet engines ever produced. Unlike the J57's dual rotor structure, the J79 is a single rotor structure. For the first time on the J-79, the compressor's adjustable rectifying blades and the afterburning full-range adjustable nozzles were used. The J-79 is also the first aircraft to be used for two-sonic flight. General Dynamics' CJ805-23 turbofan engine is one of the other alternatives to turbofan engines. What makes the CJ805-23 so special is its fan position. He is the only turbofan engine designed with a rear fan. In the 1950s and 1960s, people encountered great difficulties in designing the first generation of turbofan engines. First, because the linear speed of the wing tip portion of the fan blade exceeds the speed of sound after the large-diameter fan is linked with the relatively small-diameter low-pressure compressor, this problem is difficult to solve at that time because there is no formula available for calculation. Use time and again to find and solve problems. The second is because the fan is forced to work by the fan because of the fan before the compressor. The third is the vibration caused by the high speed rotation of the elongated fan blades. General Dynamics' rear fan design completely avoided these three major difficulties. The rear fan of the CJ805-23 is actually a double-section blade with the lower half of the blade being the turbine blade and the upper half being the fan blade. Such a blade is placed at the end of the inner core engine like a free turbine with a vortex shaft. The blade has no mechanical connection to the rotor of the core engine, so that the speed of the fan can be designed as desired, and the rear of the blade does not adversely affect the compressor. However, while avoiding difficulties, it also caused new problems. The first is the uneven heating of the blades. The turbine part of the rear fan blades of the CJ805-23 has a maximum temperature of 560 degrees during operation, while the minimum temperature of the fan section is only 38 degrees. Secondly, since the rear fan does not work at the cold end of the engine like the front fan, but works at the hot end of the engine, the reliability of the fan also decreases, and the most important requirement for the aircraft's power is Nothing is wrong. Moreover, the design of the rear of the fan makes the flight resistance of the engine larger than that of the engine in front of the fan due to the shape. When the "Convey", JT-3D, and CJ805-23 turbofan engines were downlined, people were constantly rethinking the development of turbofan engines. It has been found that if a turbofan engine starts to be trial-produced on a piece of white paper like Kangwei, it will take at least a decade or so for the new engine to be put into production. However, if a turbojet engine is developed using a turbojet engine as an internal engine like the JT-3D or CJ805-23, since the most technically difficult part of the engine is solved, Time is still a lot of money, manpower and material resources. In this context, in order to shorten the development time of new turbofans and reduce development costs. The US government has implemented the "Advanced Turbine Gas Generator Program" since 1959, with the clear requirements for future aviation power. The goal of this plan is to use the latest research results. Pilot a gas core machine and conduct an interview car to expose the problems of each part. Zooming in or out on top of this gas core machine, and adding other components, such as compressors, fans, etc., can be assembled into different types of aero-turbine engines. Such as turbofans, turbojets, turboshafts, turboprops, etc. The "Advanced Turbine Gas Generator Program" is actually a pre-research project with a current look. From today's point of view, the direction of this project is undoubtedly correct. The US government is actually motivating the two major power companies in the country to operate the most difficult part of the aerodynamic system. Because the most serious technical difficulties in gas turbine engines are generated on this gas core machine with gas generator and gas turbine as the main body. On each engine powered by high-temperature gas to drive the gas turbine, the gas core machine consisting of a gas generator and a gas turbine will be the location of the highest temperature and maximum pressure that will be launched. Therefore, it is subjected to the greatest stress and the most demanding working conditions. However, the difficulty of the gas core machine is not only the pressure and temperature, the huge centrifugal force brought by the high number of revolutions, the huge impact of the aircraft during acceleration, but also the overload and overload caused by the aircraft when maneuvering. To cause deformation of the parts. Taking out any one of the many difficulties will be a huge engineering problem. But if these problems are not solved, then a more advanced jet engine will not be able to talk about it. Under this plan, both Pratt & Whitney and General Dynamics quickly launched their own gas core machines. Pratt & Whitney's core machine is called STF-200 and General Dynamics' gas core machine is GE-1. The pre-research initiated by Americans 40 years ago is still playing his role. Nowadays, all kinds of aero engines produced by Pratt & Whitney and General Dynamics are really asking for their roots. They are all from the two ancestors of STF-200 and GE-1. Second, single rotor and multiple rotors When developing a new turbofan engine, the first problem to be solved was his overall structural problem. The problem with the overall structure is that the number of rotors of the engine is somewhat. At present, the overall structure of the turbofan engine is nothing more than three types, one is a single rotor, the other is a twin, and the third is a three rotor. The structure of the single rotor is the simplest. The whole engine has only one shaft, and the fan, compressor and turbine are all on this axis. The benefits of a simple structure are self-evident - save money! On the one hand, the savings will always come back on the other side. First of all, in theory, the compressor of a single-rotor turbofan engine can be made into any number of stages in order to achieve a certain boost ratio. However, because of the structural limitations of a single rotor, its fans, low-pressure compressors, high-pressure compressors, low-pressure turbines, and high-pressure turbines must all be mounted on the same spindle so that they must maintain the same speed during operation. The problem is relative. When the engine of a single rotor suddenly drops when the engine is working (such as slamming the small throttle), the high pressure part of the compressor will be seriously degraded due to the lack of sufficient number of revolutions. When the efficiency of the high pressure part decreases, the load of the low pressure part of the compressor rises sharply. When the low pressure compressor partially overloads, it will cause the engine to wheezing. In normal flight, the engine's vibration is absolutely right. It is allowed, because in normal flight, the engine will fall off in all likelihood. In order to solve the overload of the low-pressure part during operation, it is only necessary to install the guide vane in front of the compressor and deflate on the intermediate stage of the compressor, that is, to discharge a part of the air to be pressurized to reduce the low-pressure part of the compressor. Load. However, the efficiency of the engine will be greatly reduced, and the effect of releasing the pressurized gas on the compressor with high boost ratio is not very obvious. The more terrible problem occurs on the fan. Since the fan must be synchronized with the compressor, the single-rotor turbofan engine limited by the high number of revolutions of the compressor can only use a relatively small channel ratio. For example, the M-53 single-rotor turbofan engine used in the Mirage-2000 has a path of only 0.3. The corresponding engine's thrust-to-weight ratio is also relatively small, only 5.8. In order to improve the working efficiency of the compressor and reduce the vibration of the engine during operation, it is thought to solve the problem with the double rotor, that is, the low pressure compressor and the high pressure compressor of the engine are operated under different rotation speeds. In this way, the low pressure compressor and the low pressure turbine form a low pressure rotor, and the high pressure compressor and the high pressure turbine cooperate to form a high pressure rotor. The rotational speed of the low pressure rotor can be relatively low. Since the temperature of the air in the compressor rises due to compression, and the speed of sound increases as the temperature of the air rises, the rotational speed of the high-pressure rotor can be designed to be relatively high. Now that the speed is increased, the diameter of the high-pressure rotor can be made smaller, so that a "bee waist" is formed on the twin-rotor jet engine, and some auxiliary equipment of the engine such as fuel regulator, starting device, etc. It can be easily installed in this "bee waist" position to reduce the windward area of ​​the engine and reduce flight resistance. The advantages of the two-rotor engine are not only these, because the high-pressure rotor of the dual-rotor engine is generally light in weight and has low starting inertia, so when designing the dual-rotor engine, only the high-pressure rotor is designed to be driven by the starter. In this way, compared with the single-rotor engine, the starting of the double rotor is relatively easy, the starting energy is also required to be small, and the weight of the starting device is relatively reduced. However, turbofan engines with dual rotor construction are not perfect. In a turbofan engine with a double-rotor structure, since the fan is to be linked with the low-pressure compressor, the fan and the low-pressure compressor must be placed on each other. The fan must increase the number of revolutions for the compressor, so that the centrifugal force and the tip speed of the relatively large diameter fan are also large. The huge centrifugal force requires the weight of the fan not to be too large, and the weight of the fan cannot be too large. In the big case, the blade length of the fan can't be too long, the diameter of the fan is small, and the channel is not natural. The practice proves that the higher the machine ratio, the greater the engine thrust and the more fuel-efficient. . In order to reduce the number of revolutions of the low-pressure compressor, the compressor's working efficiency of the compressor is naturally reduced. The consequence of the reduction of the single-stage boost ratio is that the compressor fan has to be increased. The number of stages to maintain a certain total boost ratio. This makes it difficult to reduce the weight of the compressor. To understand the contradiction between the number of compressors and fans. It is natural to think of a three-rotor structure. The so-called three-rotor is another fan-stage rotor on the two-rotor engine. In this way, the fan, the high pressure compressor and the low pressure compressor are all self-contained rotors, each having its own rotational speed. There is no relatively fixed mechanical coupling between the three rotors. In this way, the fan and the low-pressure rotor can be operated without each other, but can be operated at the most tested speed. Designers can design engine fan speeds, fan diameters, and channel ratios relatively freely. The rotation speed of the low-pressure compressor can also be prevented from the elbow of the fan. After the rotation speed of the low-pressure compressor is increased, the efficiency of the compression is increased, the number of stages is reduced, the weight is reduced, and the length of the engine can be further reduced. However, the structure of the engine of the three-rotor structure is further complicated compared to the two-rotor engine. The three-rotor engine has three coaxial rotors that are nested together, so that the bearing fulcrum is almost twice as large as that of the double-rotor engine, and the supporting structure is more complicated. The lubrication of the bearing and the sealing between the compressors It is also more difficult. The three-rotor engine has a lot more engineering problems than the two-rotor engine, but the British company Luo Luo has a special liking for him, because there are huge benefits behind the surface difficulties, Luo Luo's RB-211 The three rotor structure is used. The increase in the number of rotors has resulted in a simplification of fans, compressors, and turbines. The three-rotor RB-211 is compared with the JT-9D of the twin-rotor of the same technical stage with the same stage: the JT-9D has 46 blades, while the RB-211 has only 33; the total number of compressors and turbines JT The -9D has 22 grades, while the RB-211 has only 19 grades; the compressor blade JT-9D has 1486 pieces, the RB-211 has only 826 pieces; the turbine rotor blade RB211 is also less than the JT9D, the former is 522 pieces, while the latter is up to 708 pieces; but from the support bearing, the RB-211 has eight bearing support points, while the JT9D has only four. Third, the fan The external thrust of the turbofan engine is completely derived from the thrust generated by the fan. The quality of the fan directly affects the performance of the engine. This is due to the high-signal ratio turbofan engine. The development of fans for turbofan engines has also undergone several processes. At the beginning of the turbofan engine, due to the limitation of the core power of the internal core and the mechanical strength of the fan material, the duct ratio of the turbofan engine cannot be made very large, for example, in the three originators of the turbofan engine. Compared with the largest CJ805-23, it is only 1.5, and the fan used in the CJ805-23 is a unique rear fan. In the two engines designed by the front fan, the JT3D has a larger channel ratio of 1.37. To achieve such a ratio, the total air flow ratio is also 271% larger than the air flow of its prototype J-57. As the air flow increases, the windward area of ​​the engine also increases. The blades of the fan also have to be long. The JT3D's primary fan has a blade length of 418.2 mm. The longest compressor blade on the J57 is about two hundred millimeters. When the fan blade becomes slender, its bending and torsional stress increase, and the problem of vibration during operation also emerges. In order to solve the trouble caused by the slender fan blades, Pratt & Whitney adopted a damping boss method to reduce the vibration caused by the fan blades. The boss is located approximately sixty-five percent from the root of the fan blade. After the fan section of the JT3D engine is assembled, the bosses on the fan blades are connected to form a circular hoop on the blades. When the fan blades are running, frictional damping is generated between the bosses and the bosses to reduce the vibration of the blades. The damping effect is obvious after the addition of the damping boss, but the disadvantages of the damping boss are also obvious. First he increased the weight of the blade, and second he lowered the efficiency of the fan blade. Moreover, if the design is improper, the air will be distorted when the air flows through the boss at a high speed, and the distortion of the airflow will cause the blade to generate more vibration. Moreover, if the quality of the blade is increased by this method, the fan itself will generate a larger centrifugal force when the engine is running. Such fan blades are difficult to make longer, and there is no longer blade ratio without a longer blade. Moreover, the mechanical strength of the slender fan blades is also very low. During the take-off and landing of the aircraft, the engine sucks in foreign objects, such as birds, and the blades of the fan are more likely to be damaged. The fan blades are broken at high speed. It will break through the external machine like a bullet and cause a big disaster. A perfect solution to the fan problem is to increase the width and thickness of the fan blades. In this way, the blade can obtain greater strength to reduce the damage of vibration and foreign objects, and the damping boss can be eliminated if the vibration is reduced to a certain extent. But the thicker blades will also have a huge centrifugal force during operation. This necessitates the reinforcement of the blades and roots and the wheel on which the blades are mounted. But aero engines can't afford such a weight. The problem of fan blades greatly limits the development of turbofan engines. A difficult problem with higher numbers of revolutions, higher mechanical strength, longer blades, and lighter weight was finally solved in the early 1980s. In October 1984, the RB211-535E4 was put into use under the wing of Boeing 757. It is a turbofan engine with an intergenerational significance. It is his fan that makes it so famous. Luo Luo Company used a creative method to solve the difficult problem that plagued the big fan than the turbofan engine fan. The fan blade of the new engine is called "wide chord without shoulder and hollow sandwich structure blade". As the name suggests, the blades of the new fan use a wide chord shape to increase the mechanical strength and hollow structure to reduce weight. The new hollow blade is divided into three sections: the leaf basin, the leaf back, and the leaf core. Its leaf basin and leaf back are made of two titanium alloy sheets, respectively. Between the two sheets is the "core" of the honeycomb structure which is also made of titanium alloy. The leaf basin, the leaf back and the leaf core are integrated by active diffusion welding. The new blades achieve great strength with extremely light weight. Such a piece of titanium alloy sandwich solved the big problem that has plagued the aerospace industry for decades. The new fan is not only lightweight, but also strong, and because of the elimination of the damping boss on the traditional slender blade, his work efficiency is higher. The number of fan blades has also been reduced by nearly a third, and the fan blades of the RB211-535E4 engine are only twenty-four. On July 15, 1991, the new wide-chord blade was subjected to a major test. An A320 of Indian Airlines took in a 5.44 kg Indian vulture with its V-2500 turbofan engine equipped with wide-chord blades during the take-off phase! The giant bird slammed into the front end of the engine, the fan, at a speed of almost three hundred kilometers! However, the engine was still working normally after such a heavy blow, and the aircraft landed safely. After landing, it was found that only 6 of the 22 wide-chord fans of the V-2500 were deformed by a huge impact force, and no blade broke. The engine was re-introduced only after the blade was replaced in the field. This unexpected impact proved the great success of the "wide-string non-shouldered hollow sandwich structure blade". The problem of solving a wide-chord fan is not the only hollow structure. In fact, when the diameter of the fan is further increased, the fan blades of the hollow structure are also overweight. For example, the GE-90 turbofan engine used on the Boeing 777 has a fan diameter of 3.142 meters. Even titanium alloy blades with hollow honeycomb structures can't work. General Dynamics then used advanced reinforced epoxy carbon fiber composites to make giant fan blades. The fan blade structure made of carbon fiber composite material is extremely light in weight and extremely strong. However, when a fan made of a composite material is hit by a large bird during operation, a delamination phenomenon occurs. In order to further increase the safety factor of GE-90, General Dynamics also coated a layer of titanium alloy on the leading edge of the fan and stitched it with Kevlar on its trailing edge. So far, the GE-90's fan can be described as foolproof. When the fan of a high-passage turbofan engine transitions from a conventional elongated narrow-chord blade to a wide-chord blade, the number of stages of the fan also undergoes a transition from a multi-stage fan to a single-stage fan. At the beginning of the turbofan engine, the fan's single-stage boost ratio can only be multi-stage series to increase the total boost ratio of the fan. For example, the JT3D's fan is two-stage, and its average single-stage boost ratio is 1.32. The total boost ratio of the fan through the two-stage series is 1.74. Multi-stage fans have almost no advantages compared with single-stage fans. They are heavy and inefficient. In fact, they are an incompetent choice when the turbofan engine is not very mature. With the step-by-step improvement of the single-stage supercharging ratio of the fan, the single-stage fan is now dominated by the turbofan engine of the medium and high ratio. For example, the single-stage fan used on the GE-90 has a boost ratio of up to 1.65. This high single-stage boost ratio eliminates the need to cascade the second-stage fan. However, the low duct ratio turbofan engine used on the fighter aircraft still uses a multi-stage wind stage structure. For example, the F100-PW-100 turbofan engine used on the F-15A consists of three stages with a total boost ratio of 2.95. The low duct turbofan engine takes such a high fan boost ratio as a result of the combination of a fan and a low pressure compressor. The low duct ratio turbofan engine used on the fighter jet is a double rotor structure consisting of a fan rotor and a compressor rotor in order to reduce the weight. Due to the limited internal volume of the fighter aircraft, it is unrealistic to use a high-passage turbofan engine with a large air flow rate. However, in order to increase the thrust, only the engine outlet pressure can be raised, and the fan must not only provide all the external thrusts but also Part of the task of the compressor, but the fan can only use a relatively high boost ratio. In fact, the multi-stage fan of the turbo fan engine with low-signal ratio is also a kind of impatience. If the single-stage supercharging ratio of the fan can reach the structure of the multi-stage fan of about 3, it will not appear again. If you want the fan's single-stage boost ratio to reach 3 levels, it can only further increase the fan's speed and make a fuss about the fan's airfoil. The blades of the fan must have a certain blade in addition to the wide-chord blade. The sweep angle is used to overcome the shock generated by the fan rotating at high speed. Only the single-stage fan boost ratio of 3 stages is possible. This will happen within twenty years. Fourth, the compressor Compressors, as the name suggests, are a kind of machinery used to compress air. Compressors used in jet engines can be divided into two categories according to their structure and working principle, one is a centrifugal compressor, and the other is an axial compressor. The shape of the detached compressor is like an obtuse flat cone. There are several spiral blades on the cone. When the disc of the compressor is running, the air will be "caught" by the spiral blades. Under the huge centrifugal force brought by the high-speed rotation, the air will be The gap between the compressor disc and the compressor casing is broken in, thereby achieving supercharging of the air. Unlike centrifugal compressors, axial compressors are composed of multi-stage fans, each of which produces a certain boost ratio. The multiplier ratio of the fans of each stage is the total boost ratio of the compressor. . Most of the compressors on modern turbofan engines are axial-flow compressors. The axial-flow compressors have the advantages of small volume, large flow, and high unit efficiency. However, in some cases, centrifugal compressors are also useful. Although the centrifugal compressor is relatively inefficient and heavy, the centrifugal compressor has a relatively stable operation and a simple structure, and the single-stage supercharging ratio is several times higher than that of the axial compressor. For example, in the TFE1042-70 turbofan engine with dual-rotor structure used in IDF of Taiwan, the high-pressure compressor adopts a four-stage axial flow type and a first-stage centrifugal type combined compressor to reduce the number of compressor stages. . To put it another way, such combined compressors are not used much on turbofan engines, but the turboshaft engines used in helicopters are now generally a combination of several stages of axial flow and a centrifugal one. Such as the domestic vortex shaft 6, The turboshaft 8 engine is a combined compressor composed of a first-stage axial flow type and a first-stage centrifugal type. The T700 engine on the US Black Hawk helicopter has a 5-stage axial flow plus a 1-stage centrifugal type. The compressor is a relatively core component of the turbofan engine. The use of a dual rotor structure on a turbofan engine is largely to meet the needs of the compressor. The efficiency of the compressor directly affects the working efficiency of the engine. At present, the goal is to increase the single-stage boost ratio of the compressor. For example, the compressor fan used on the J-79 has 17 stages, and the average single-stage boost ratio is 1.16, so the total boost ratio of the 17-stage blades is about 12.5, and the GE-90 used on the Boeing 777. The average single-stage boost ratio of the compressor is increased to 1.36, so that the total boost ratio of the ten-stage booster blade can reach about 23. The F-22's power F-119 engine's compressor is even better. The total boost ratio of the 3-stage fan and the 6-stage high-pressure compressor is about 25, and the average single-stage boost ratio is 1.43. The increase in the average single-stage boost ratio is beneficial for reducing the number of stages of the compressor, reducing the total amount of the engine, and shortening the overall length of the engine. However, as the compressor's boost ratio is getting higher and higher, the problem of compressor surge and compressor heat protection has emerged. In the compressor, the temperature of the air is also rising as it is pressurized. For example, when the supercharge ratio of the aircraft on the ground takeoff compressor reaches about 25, the outlet temperature of the compressor will exceed 500 degrees. In the low-passage turbofan engine used in the fighter aircraft, the temperature is also increased due to the punching action in the middle and low-altitude flight. When the total pressure ratio of the compressor reaches about 30, the outlet temperature of the compressor will reach about 600 degrees. Such a high temperature makes titanium alloy difficult, and can only be replaced by a high-temperature resistant nickel-based alloy. However, the base weight of the nickel-based alloy is too large compared with the titanium alloy, so the material needs to be improved, so people develop it again. A new type of high temperature resistant titanium alloy. How the turbine engine works The working principle of the turbojet engine, the following figure is an action model. 1. The single-rotor turbojet engine consists of five major components: the intake port, the compressor, the combustion chamber, the turbine and the nozzle. 2. Working principle: a sufficient amount of air is smoothly introduced into the compressor through the inlet port with minimal flow loss; the compressor rotates the air at high speed to work on the air to compress the air to increase the pressure of the air; the high pressure air is in the combustion chamber and Fuel mixing, combustion, chemical energy is converted into heat, forming high temperature and high pressure gas; high temperature and high pressure gas first expands in the turbine, pushing the turbine to rotate, to drive the compressor; then the gas continues to expand in the nozzle, accelerate gas, improve gas The speed of the gas is ejected at a higher speed to generate thrust. 3, several important parameters: 1) total gas before the turbine: this is a key parameter, but also a limited parameter. Its high and low level indicates the performance of the engine. It should not exceed the maximum allowable value during use, otherwise the engine should be inspected and repaired. 2) Engine exhaust temperature: EGT, which is an important monitoring parameter of the engine, its high and low reflects the total temperature of the gas before the turbine. 3）å‘动机的压力比：EPR，是指低压涡轮åŽçš„总压与低压压气机进å£å¤„的总压之比，对åŒä¸€ç±»åž‹çš„å‘动机æ¥è¯´ï¼ŒEPR高，表明å‘动机的推力就大。 Motorcycle Bags,Motorbike Saddle Bag,Motorbike Back Seat Bag,Motorcycle Backpack Waterproof Dongguan C.Y. RedApple Industrial Limited , https://www.redapplebags.com