The domestic aviation engine CJ2000 for the domestic long-range wide-body passenger aircraft C929 has been officially announced by China Aviation Development not long ago, with a thrust of more than 35 tons and a fan diameter of more than 3 meters. Behind this excellent engine, it embodies the hard work and wisdom of countless AECC people, and it has gone through many hardships and extremely rigorous tests before it finally came out.
As the pinnacle of modern engineering technology, the aero engine is not only the only power for the aircraft to soar into the sky, but also the only energy source for the aircraft control, air conditioning, oxygen supply, lighting and the power system of the whole aircraft.
However, before such an aero engine can be finalized, it must withstand numerous rigorous tests on the ground and in the air, which can total more than tens of thousands of hours, and the entire test cycle often takes years or even decades. The number of engines used in the test ranges from dozens to hundreds, and the cost is at least billions of dollars.
It is reported that the domestic 35-ton high-thrust turbofan engine CJ2000 for the domestic wide-body passenger aircraft C929 has produced 20 engines for ground platform testing alone. In terms of testing standards and safety, reliability, economy, and life testing, the engineers of the mainland have not lowered their requirements, on the contrary, they have even surpassed the Western aviation development powers in some individual standards. This not only shows the excellence of AECC in the field of aero engines, but also reflects the strict requirements for domestic engines.
CJ2000, as a turbofan engine with a large bypass ratio, high thrust and large size, which was approved in 2018, has previously passed the technical verification with a high-performance core machine. In the mainland, the aero engine project is a little different from the aircraft, and under normal circumstances, the engine project will be officially approved only after the technical verification machine is available. However, its name at that time was "AEF3500", which means that the thrust could reach 35 tons.
On the way to forensics, CJ2000 has also undergone countless tests and rigorous tests to ensure that its design and manufacture can work stably under various extreme working conditions and harsh conditions. There are at least ten of them for the major items tested.
1. Ground bench test: This is one of the most critical tests in the engine development process. On the ground bench, the engine will be subjected to continuous operation for a long time and under high loads to verify its performance, reliability and durability. During the test, the engine will be subjected to a variety of complex operating conditions, such as high temperature, high pressure, high speed, etc., to test its ability to withstand extreme fuel conditions and lubrication conditions, including testing the performance of the fuel and lubricating oil after the engine is contaminated.
2. Flight bench test: On the basis of the ground bench test, the engine also needs to be tested in flight. Flight tests are designed to verify the performance of the engine in real flight conditions. During the test, the engine will be installed on the aircraft to perform various flight tasks such as takeoff, climb, cruise, descent, etc. The rigor of flight tests is also very high, requiring the engine to maintain good performance in complex flight environments.
3. Environmental adaptability test: Before the engine is finalized, it is necessary to carry out field environmental adaptability test to verify its ability to operate in different climate and geographical environments. The test items include performance tests in high-temperature, cold, plateau, humid and hot environments, which require the engine to work normally in extreme environments, including starting, running and shutting down under extreme heat and cold conditions.
4. Noise and emission testing: The noise and emission of the engine is an important indicator to measure its environmental performance, so it is necessary to carry out strict noise and emission testing to meet international and domestic environmental protection regulations. The engine is required to reduce noise and emissions as much as possible while maintaining performance.
5. Safety testing: The safety of the engine is of paramount importance, so multiple safety tests are required before finalization. The test items include engine fault diagnosis, fire prevention, explosion protection, etc., which require the engine to ensure flight safety in the event of failure or abnormal conditions.
6. Life test: The life of the engine directly affects the cost of the aircraft. This experiment requires continuous operation of the engine for a long period of time, simulating its performance and reliability throughout its life cycle, and requires the engine to maintain good performance after a long period of operation.
7. Water swallowing test: Simulates the situation of the engine inhaling water in flight, and tests whether the engine can maintain stable operation after swallowing a large amount of water, whether it causes damage or degrades performance. It is required that the thrust drop of the engine after water swallowing is not lower than the specified value, and at the same time, parameters such as temperature and vibration do not exceed the safety limit. Based on this, the engineers will evaluate the engine's waterproofing, drainage, and resistance to heat and moisture.
8. Hail test: Simulate the situation of the engine encountering hail when flying at high altitude, and test whether the engine can maintain normal operation after being hit by hail. The hail used in the test ranged in size from 10 mm to 50 mm and weighed from a few grams to tens of grams to simulate the effects of different sizes of hail on the engine. At the same time, the shape, hardness and impact velocity of the hail are also important factors to consider when testing.
9. Sand swallowing test: This test is an important test to evaluate the reliability of the engine after inhaling foreign objects such as sand particles, which can effectively help engineers evaluate the withstand capacity of various engine components in extreme environments, and is essential to ensure that the engine can maintain stable operation in the harsh environment of deserts or other sandy areas. During the test, sand particles of specific particle size and hardness are injected into the engine inlet through a special device, so that the engine can run at different speeds and powers, simulating different working conditions in flight.
10. Bird strike test: Simulates the situation of the engine encountering a bird strike in flight, and tests the protection ability of the engine and the performance after being hit. The weight and size of the birds used in the bumping test ranged from hundreds of grams to kilograms, and the size of the wings ranged from tens of centimeters to nearly 100 centimeters. For the speed of bird strikes, engineers will also set different settings for the firing cannon that simulates bird strikes according to the actual situation.
In fact, the CJ2000 engine is far more than these test items in the rigorous test, there are maintenance tests, fuel efficiency tests, vibration tests, corrosion tests, thermal shock tests, etc., as well as component tests including combustion chambers, fuel nozzles, air intakes, compressors, plane grilles, tail nozzles, turbines and many other components.
In addition, the engine is evaluated for flight hours and cycles, as well as analysis of gas, vibration, oil, thermal cycles and maintenance records, and a comprehensive test management platform such as engine health management system (EHM) and remaining service life prediction model has been established.