Piston aeroengine
It is an aeroengine used in early aircraft or helicopters to drive propellers or rotors. The power of large piston aero engines can reach 2500 kilowatts. Later it was replaced by gas turbine engines with high power and good high-speed performance. However, low-power piston aero engines are still widely used in light aircraft, helicopters and ultra-light aircraft.
Gas turbine engine
This type of engine is the most widely used. Including turbojet engines, turbofan engines, turboprop engines and turboshaft engines, all have compressors, combustion chambers and gas turbines. Turboprop engines are mainly used for aircraft with a speed of less than 800 kilometers per hour; turboshaft engines are mainly used for powering helicopters; turbofan engines are mainly used for aircraft with higher speeds; turbojet engines are mainly used for supersonic aircraft.
Ramjet engine
It is characterized by a compressorless air machine and a gas turbine. The air entering the combustion chamber is pressurized by the ramjet effect during high-speed flight. It has a simple structure and large thrust, and is especially suitable for high-speed and high-altitude flight. Due to the inability to start by itself and poor performance at low speeds, the scope of application is limited and is only used on missiles and air-launched target missiles.
Others
The above-mentioned engines all absorb air from the atmosphere as the oxidant for fuel combustion, so they are also called air-absorbing engines. Others include rocket engines, pulse engines and aerospace electric motors. The propellant (oxidizer and combustion agent) of the rocket engine is all carried by itself. The fuel consumption is too large and it is not suitable for long-term operation. It is generally used as the engine of the launch vehicle and is only used for short-term acceleration on the aircraft (such as starting the accelerator). Pulse engines are mainly used in low-speed target drones and aviation model aircraft. Aviation electric motors driven by solar cells are only used in light aircraft and are still in the experimental stage.
Piston engine period
Early liquid-cooled engines dominated. At the end of the 19th century, when internal combustion engines began to be used in automobiles, people immediately thought of using internal combustion engines in aircraft as the power source for aircraft flight, and began experiments in this area.
In 1903, the Wright brothers in the United States modified a 4-cylinder, horizontal in-line water-cooled engine and successfully used it on their "Aviator One" aircraft for flight tests. This engine only produces 8.95 kW of power, but weighs 81 kg, with a power-to-weight ratio of 0.11kW/daN. The engine drives two wooden propellers with a diameter of 2.6m through two chains like those on bicycles. The first flight had only 12 seconds of airtime and a flight distance of 36.6m. But it is the first successful flight of a powered, manned, sustained, stable, and maneuverable heavier-than-air aircraft in human history.
Fueled by the use of aircraft for war purposes, aviation began to flourish especially in Europe, with France leading the way. Although the United States invented powered aircraft and built the first military aircraft, it did not have even one usable new aircraft when it entered the war. Among the 6,287 aircraft of the American aviation squadrons on the front line, 4,791 were French aircraft, such as the "Spade" fighter equipped with Hispano-Siza V-type liquid-cooled engine. The power of this engine has reached 130~220kW, and the thrust-to-weight ratio is about 0.7kW/daN. The aircraft speed exceeds 200km/h and the ceiling is 6650m.
At that time, the flight speed of the aircraft was still relatively low, and it was difficult to cool the air-cooled engine. In order to cool down, the engine is exposed and the resistance is large. Therefore, most aircraft, especially fighter jets, use liquid-cooled engines. During this period, the rotating cylinder air-cooled radial engine invented by the French Séguin brothers in 1908 became popular for a while. This kind of engine with a fixed crankshaft and rotating cylinders was eventually limited by the increase in power. After the cooling problem of the fixed-cylinder air-cooled radial engine was solved, it withdrew from the stage of history.
Between the two world wars, several important inventions appeared in the field of piston engines: the engine fairing not only reduced the resistance of the aircraft, but also solved the cooling problem of the air-cooled engine, and could even The design of two-row or four-row cylinder engines creates conditions for increasing power; the exhaust gas turbocharger increases the intake pressure under high-altitude conditions and improves the high-altitude performance of the engine; the variable-pitch propeller can increase the efficiency of the propeller and the engine power output; the cooling exhaust valve filled with metallic sodium solves the overheating problem of the exhaust valve; spraying a mixture of water and methanol into the cylinder can increase the power by one-third in a short time; high-octane fuel increases It improves the anti-knock performance of the fuel and gradually increases the pre-combustion pressure in the cylinder from 2 to 3 to 5 to 6, or even 8 to 9, which not only increases the power per liter but also reduces the fuel consumption rate.
Since the mid-1920s, air-cooled engines have developed rapidly, but liquid-cooled engines still have a place. During this period, after the fairing solved the resistance and cooling problems, air-cooled radial engines due to It has developed rapidly due to its advantages such as high rigidity, light weight, good reliability, maintainability and survivability, and large power growth potential, and has begun to replace liquid-cooled engines on large bombers, transport aircraft and ground attack aircraft. In the mid-1920s, the American Wright Company and Pratt & Whitney Company successively developed single-row "Cyclone" and "Hurricane" as well as "Wasp" and "Bumblebee" engines, with a maximum power of more than 400kW and a power-to-weight ratio of more than 1kW/ daN. By the outbreak of World War II, due to the successful development of the dual-exhaust cold star engine, the engine power had increased to 600~820kW. At this time, the flight speed of the propeller fighter has exceeded 500km/h and the flight altitude has reached 10,000m.
During the Second World War, air-cooled radial engines continued to develop in the direction of high power. Among the more famous ones are Pratt & Whitney's two-row "Double Wasp" ((R-2800)) and the four-row "Giant Wasp" (R-4360). The former was finalized on July 1, 1939, with an initial power of 1230kW. , it developed 5 series and dozens of modifications, with the final power reaching 2088kW, which was used in a large number of military and civilian aircraft and helicopters. 24,000 R-2800 engines were produced for the P-47 fighter alone, including the P-47. The J's maximum speed is 805km/h. Although it is controversial, it is said that it was the fastest fighter in World War II. This engine holds a special place in aviation museums or aviation exhibitions. The R-2800 is always placed in the central position. Some aviation history books even say that it would have been much more difficult for the Allies to win in World War II without the R-2800 engine. The latter had four rows of 28 cylinders. With a capacity of 71.5L and a power of 2200~3000kW, it is the most powerful piston engine in the world and is used in some large bombers and transport aircraft. In 1941, the B-36 bomber designed around six R-4360 engines was one of the few propelled aircraft. One, but not put into use.
Wright's R-2600 and R-3350 engines are also famous dual-exhaust cold star engines. The former was launched in 1939 with a power of 1120kW and was used in the first. A Boeing "Clipper" 314 four-engine seaplane that flew ticket-buying passengers across the Atlantic, as well as some smaller torpedo planes, bombers and attack aircraft, the latter was put into service in 1941, initially with a power of 2088kW, and was mainly used. Based on the famous B-29 "Flying Fortress" strategic bomber, the R-3350 developed an important modification after the war - the turbine combination engine. The exhaust of the engine drives three exhaust gas turbines evenly distributed around the circumference. It can produce 150kW of power in the maximum state. In this way, the power of R-3350 was increased to 2535kW, and the fuel consumption rate was as low as 0.23kg/(kW·h). In September 1946, P2V1 was equipped with two R-3350 turbine combination engines. The "Neptune" aircraft set a world record for an airborne flight distance of 18,090km. The competition between liquid-cooled engines and air-cooled engines continued in World War II. Although liquid-cooled engines have many shortcomings, their The small windward area is particularly advantageous for high-speed fighter jets. Moreover, the fighter jet flies at a high altitude and is less threatened by ground fire, so the vulnerability of liquid-cooled engines is not prominent. Therefore, it is used in many fighter jets.
For example, four of the five most produced fighter jets in the United States during this war used liquid-cooled engines. Among them, it is worth mentioning the Merlin engine of the British Rolls-Royce Company. When it first flew on the "Hurricane" fighter in November 1935, the power reached 708kW; when flying on the "Spitfire" fighter in 1936, the power was increased to 783kW.
Aviation Engine
Both aircraft were famous fighter jets during World War II, with speeds reaching 624km/h and 750km/h respectively. The power of the Merlin engine reached 1238kW at the end of the war, and even set a record of 1491kW. The American Parker Company produced the Merlin engine according to the patent and used it to modify the P-51 "Mustang" fighter jet, turning an ordinary aircraft into the best wartime fighter jet. The "Mustang" fighter uses an unusual five-blade propeller. After installing a Merlin engine, the maximum speed reaches 760km/h and the flight altitude is 15,000m. In addition to having the fastest speed at the time, another outstanding advantage of the "Mustang" fighter was its amazing long-distance capability. It could escort Allied bombers all the way to Berlin. By the end of the war, the "Mustang" fighter jets had shot down 4,950 enemy aircraft in air combat, ranking first on the European battlefield. In the Far East and Pacific battlefields, it was the entry of the F6F "Hellcat" fighter equipped with an air-cooled engine that ended the dominance of the Japanese "Zero" fighter. Aviation historians regard the "Mustang" aircraft as the pinnacle of propeller-driven fighters.
The most important technological advances after the beginning of World War II and after the war were direct oil injection, turbine combination engines and low-pressure ignition.
Driven by the two world wars, the performance of engines improved rapidly. The unit power increased from less than 10 kW to about 2500 kW, and the power-to-weight ratio increased from 0.11 kW/daN to 1.5 kW/daN. Around that, the power per liter increases from several kilowatts to forty or fifty kilowatts per liter of displacement, and the fuel consumption rate decreases from about 0.50 kg/(kW·h) to 0.23~0.27 kg/(kW·h). The renovation life is extended from dozens of hours to 2000~3000h. By the end of World War II, the piston engine had developed quite maturely. The flight speed of propeller aircraft powered by it increased from 16km/h to nearly 800km/h, and the flight altitude reached 15,000m. It can be said that the piston engine has reached the peak of its development.
Piston engines in the jet age
After the end of World War II, the invention of the turbojet engine ushered in the jet age, and piston engines gradually withdrew from the main aviation field. However, horizontally opposed cylinder piston engines with power less than 370 kW are still widely used in light low-speed aircraft and helicopters, such as administrative aircraft, agricultural and forestry aircraft, exploration aircraft, sports aircraft, private aircraft and various unmanned aerial vehicles. Rotary piston engines It is making its mark on drones, and NASA is also developing a new two-stroke diesel engine that uses aviation kerosene for use by the next generation of small general-purpose aircraft.
NASA in the United States has implemented a general aviation propulsion plan to provide power technology for future general-purpose light aircraft that are safe, comfortable, easy to operate, and affordable. This kind of light aircraft is roughly 4 to 6 seats, and the flying speed is about 365 km/h. One option is to use a turbofan engine. The aircraft using it is slightly larger, has 6 seats, and has a higher speed. Another option is to use a Diesel cycle piston engine. The aircraft using it has 4 seats and the speed is low. The requirements for the engine are: power of 150 kW; fuel consumption rate of 0.22 kg/(kW·h); meeting future emission requirements; manufacturing and maintenance costs reduced by half. By 2000, the program had conducted more than 500 hours of engine ground testing, with a power of 130 kW and a fuel consumption rate of 0.23 kg/(kW·h).
Gas turbine engine period
The second period spans from the end of World War II to the present. Over the past 60 years, aviation gas turbine engines have replaced piston engines, ushered in the jet age, and dominated aviation power. Driven by technological development (see Table 1), turbojet engines, turbofan engines, turboprop engines, propeller fan engines and turboshaft engines have played their respective roles in different flight fields at different times, making aircraft performance span Go to one new level after another.
Turbojet/turbofan engine
British Whittle and German Ohain successfully developed centrifugal turbojet on July 14, 1937 and September 1937 respectively. Engines WU and HeS3B. The former has a thrust of 530daN, but the Gloster E28/39 aircraft that made its first test flight on May 15, 1941 was equipped with its improved W1B, with a thrust of 540daN and a thrust-to-weight ratio of 2.20. The latter has a thrust of 490 daN and a thrust-to-weight ratio of 1.38. It was first installed on the Heinkel He-178 aircraft and successfully tested on August 27, 1939. This is the world's first jet aircraft to successfully test fly, ushering in a new era of jet propulsion and a new era of aviation.
The world's first practical turbojet engine was Germany's Eumo-004. Bench testing began in October 1940. The thrust reached 980daN in December 1941. It was installed on July 18, 1942. Successful test flight on Messerschmitt Me-262 aircraft. From September 1944 to May 1945, the Me-262*** shot down 613 Allied aircraft and lost 200 of its own (including non-combat losses). Britain's first practical turbojet engine was the Wieland launched by Rolls-Royce in April 1943, with a thrust of 755 daN and a thrust-to-weight ratio of 2.0. After the engine was put into production that year, it was equipped with the "Meteor" fighter jet and was handed over to the British Air Force in May 1944. The aircraft successfully intercepted German V-1 missiles over the English Channel.
After the war, the United States, the Soviet Union, and France successively developed their first-generation turbojet engines by buying patents or using materials and personnel obtained from Germany. Among them, the J47 axial flow turbojet engine of the American General Electric Company and the RD-45 centrifugal turbojet engine of the Soviet Klimov Design Bureau both have a thrust of about 2650 daN and a thrust-to-weight ratio of 2 to 3. They were launched in 1949 respectively. In 1948, it was installed on F-86 and MiG-15 fighter jets. These two aircraft launched a life-and-death air battle during the Korean War. In the early 1950s, the introduction of afterburners enabled engines to significantly increase thrust in a short period of time, providing enough thrust for aircraft to break through the sound barrier. Typical engines include the American J57 and the Soviet RD-9B. Their afterburning thrusts are 7000daN and 3250daN respectively, and their thrust-to-weight ratios are 3.5 and 4.5 respectively. They are installed on the supersonic single-engine F-100 and twin-engine MiG-19 fighter jets.
In the late 1950s and early 1960s, various countries developed a number of turbojet engines suitable for M2 and above aircraft, such as J79, J75, Evonne, Olympus, Atta 9C, and R-11 With R-13, the thrust-to-weight ratio has reached 5~6. In the mid-1960s, the J58 and R-31 turbojet engines for the M3 first-class aircraft were also developed. By the early 1970s, the Olympus 593 turbojet engine used in the "Concorde" supersonic passenger aircraft was finalized, with a maximum thrust of 17,000 daN. No more important turbojet engines were produced since then.
The development of turbofan engines originated from World War II. The world's first operating turbofan engine was the DB670 (or 109-007) developed by Germany's Daimler-Benz. It reached a thrust of 840 kilograms on the test bench in April 1943, but it failed due to technical difficulties and war reasons. obtain further development. The world's first mass-produced turbofan engine was the British Conway, which was finalized in 1959. It has a thrust of 5730daN and is used on VC-10, DC-8 and Boeing 707 passenger aircraft. There are two types of bypass ratios: 0.3 and 0.6, and the fuel consumption rate is 10% to 20% lower than that of turbojet engines of the same period. In 1960, the United States successfully modified and developed the JT3D turbofan engine based on the JT3C turbojet engine, with a thrust of more than 7700 daN and a bypass ratio of 1.4. It was used on Boeing 707 and DC-8 passenger aircraft and military transport aircraft.
In the future, turbofan engines will develop in two directions: military afterburning engines with low bypass ratios and civilian engines with high bypass ratios. In terms of low-bypass-ratio military afterburning turbofan engines, in the 1960s, the United Kingdom and the United States developed the Spey-MK202 and TF30 based on civilian turbofan engines, which were respectively used in the "Phantom" F-4M purchased by the United Kingdom. /K fighter and the American F111 (later used in the F-14 fighter).
Their thrust-to-weight ratio is similar to that of turbojet engines of the same period, but their intermediate fuel consumption is low, which greatly increases the aircraft's range. In the 1970s and 1980s, various countries developed turbofan engines with a thrust-to-weight ratio of 8, such as the F!00, F404, and F110 of the United States, the RB199 of the three Western European countries, and the RD-33 and AL-31F of the former Soviet Union. They are equipped with third-generation fighter jets on the front line, such as F-15, F-16, F-18, Tornado, MiG-29 and Su-27. A turbofan engine with a thrust-to-weight ratio of 10 has been successfully developed and will be put into service soon. They include the US F-22/F119, Western Europe's EFA2000/EJ200 and the French Rafale/M88. Among them, the F-22/F119 has the representative characteristics of the fourth-generation fighter aircraft-supersonic cruise, short take-off and landing, super maneuverability and stealth capabilities. The JSF power unit F136, which can perform supersonic vertical takeoff and short landing, is under development and is expected to be put into service from 2010 to 2012.
Since the first generation of high-bypass ratio (4~6) turbofan engines with a thrust of more than 20,000 daN was put into use in the 1970s, a new era of large wide-body passenger aircraft has been ushered in. Later, high-bypass-ratio turbofan engines of different thrust levels with thrust less than 20,000 daN were developed and widely used in various mainline and regional passenger aircraft. More than 13,000 units of the CFM56 series with thrust levels of 10,000 to 15,000 daN have been produced, and have set a record of more than 30,000 hours of on-board life. Since civilian turbofan engines have been put into use, cruise fuel consumption has been reduced by half, noise has been reduced by 20dB, and CO, UHC, and NOX have been reduced by 70%, 90%, and 45% respectively. The second-generation high-bypass ratio (6~9) turbofan engine that was put into use on the Boeing 777 in the mid-1990s has a thrust of more than 35,000 daN. Among them, General Electric's GE90-115B set a world record for engine thrust of 56,900 daN in February 2003. Pratt & Whitney is developing a new generation of turbofan engine PW8000. This gear-driven turbofan engine has a thrust of 11,000~16,000daN, a bypass ratio of 11, and a fuel consumption rate reduced by 9%.
Turboprop/Turboshaft Engine
The first turboprop engine was the Jendrassik Cs-1 designed in Hungary in 1937 and commissioned in 1940. The aircraft was originally planned to be used in the country's Varga RMI-1 X/H twin-engine reconnaissance/bomber but the aircraft project was cancelled. In 1942, the United Kingdom began development of its first turboprop engine, the Rolls-Royce RB.50 Trent. The aircraft first operated in June 1944. After 633 hours of testing, it was installed on a Gloster "Meteor" fighter on September 20, 1945, and conducted 298 hours of flight experiments. Since then, the United Kingdom, the United States, and the former Soviet Union have successively developed a variety of turboprop engines, such as Dart, T56, AI-20, and AI-24. These turboprop engines have low fuel consumption and high take-off thrust, and are equipped with some important transport aircraft and bombers. The turboprop engine T56/501, which was put into service in the United States in 1956, is installed on C-130 transport aircraft, P3-C reconnaissance aircraft and E-2C early warning aircraft. Its power range is 2580~4414 kW, with multiple military and civilian series. More than 17,000 units have been produced and exported to more than 50 countries and regions. It is one of the most produced turboprop engines in the world and is still in production today. . The former Soviet Union's HK-12M has a maximum power of 11,000kW and is used in Tu-95 "Bear" bombers, An-22 military transport aircraft and Tu-114 civilian transport aircraft. Eventually, due to the limitations of propellers in absorbing power, size and flight speed, turboprop engines were gradually replaced by turbofan engines on large aircraft, but they still have a place on small and medium-sized transport aircraft and general aircraft. Among them, Pratt & Whitney Canada's PT6A engine is a typical representative. Over the past 40 years, this engine series with a power range of 350~1100kW has developed more than 30 modifications and is used in nearly 100 types of aircraft in 144 countries. It is produced globally. More than 30,000 units were purchased. In the 1990s, the United States developed a new generation of high-speed regional aircraft based on the T56 and T406. The AE2100 is currently the most advanced turboprop engine with a power range of 2983 to 5966 kW. Its take-off fuel consumption is extremely low at 0.249 kg/ (kW·h).
In the late 1980s, there was a boom in propeller-fan engines whose performance was between turboprop engines and turbofan engines. Some well-known engine companies have conducted predictions and tests to varying degrees. Among them, General Electric's unducted fan (UDF) GE36 has conducted flight tests.
Since the French Turbomeca Company developed the 206 kW Aduster I turboshaft engine in 1950 and equipped it with the American S52-5 helicopter for its first successful flight, turboshaft engines have become more popular in the helicopter field. Gradually replacing the piston engine and becoming the most important form of power. Over the past half century, four generations of turboshaft engines have been successfully developed, and the power-to-weight ratio has increased from 2kW/daN to 6.8~7.1 kW/daN. The third generation turboshaft engine was designed in the 1970s and put into production in the 1980s. The main representative models include Makira, T700-GE-701A and TV3-117VM, equipped with AS322 "Super Puma", UH-60A, AH-64A, Mi-24 and Ka-52. The fourth-generation turboshaft engine is a new generation of engines developed in the late 1980s and early 1990s. Representative models include the RTM322 jointly developed by Britain and France, the T800-LHT-800 from the United States, the MTR390 and MTR390 jointly developed by Germany, France and Britain. Russian TVD1500, used on NH-90, EH-101, WAH-64, RAH-66 "Comanche", PAH-2/HAP/HAC "Tiger" and Ka-52. The largest turboshaft engine in the world is the Ukrainian D-136, with a take-off power of 7500 kW. A Mi-26 helicopter equipped with two engines can carry 20 tons of cargo. The tilt-rotor V-22, powered by the T406 turboshaft engine, breaks through the upper limit of conventional rotorcraft's flight speed of 400 km/h, suddenly increasing to 638 km/h.
The significant technological progress made in the 60 years since the advent of aviation gas turbine engines can be demonstrated by the following figures:
The thrust-to-weight ratio of fighter engines in service has increased from 2 to 7~9. There are 9~10 that have been finalized and are about to be put into use. The maximum thrust of civilian high-bypass-ratio turbofan engines has exceeded 50,000 daN. The cruise fuel consumption rate has dropped from 1.0 kg/(daN·h) of turbojet engines in the 1950s to 0.55 kg/(daN·h). The noise has dropped by 20dB. CO, UHC and NOx dropped by 70%, 90% and 45% respectively.
The power-to-weight ratio of helicopter turboshaft engines in service has increased from 2kW/daN to 4.6~6.1 kW/daN, and those that have been finalized and are about to be put into use reach 6.8~7.1 kW/daN.
The engine reliability and durability are doubled. The in-flight shutdown rate of military engines is generally 0.2~0.4/1,000 engine flight hours, and that of civilian engines is 0.002~0.02/1,000 engine flight hours. The finalization requirement of the fighter engine is to pass the 4300~6000TAC cycle test, which is equivalent to more than 10 years of normal use, and the life of the hot-end parts reaches 2000h; the life of the hot-end parts of the civil engine is 7000~10000h, and the on-board life of the whole engine reaches 15000~20 000 h, which is equivalent to about 10 years of use.
In short, aviation turbine engines have developed quite maturely and have made important contributions to the development of various aircraft, including the M3-level combat/reconnaissance aircraft, which has supersonic cruise, stealth, short take-off and landing and Super-maneuverable fighter jets, subsonic vertical take-off and landing fighter jets, wide-body passenger aircraft that meet the 180-minute twin-engine extended range passenger aircraft (ETOPS) requirement, giant helicopters with a payload of 20 tons, and tilt-rotor aircraft with speeds exceeding 600km/h. At the same time, it also lays the foundation for various aviation modified light ground gas turbines.