With all that said, why is it so difficult to build a civil aviation engine? This has to mention two difficulties in the development of modern jet engines, the first is control, and the second is materials.
1, control problem
(Turbofan Engine Air Flow Control)
The control of jet engine is mainly divided into two aspects, the first is pressure control and the second is temperature control.
For example, how to increase the pressure at the outlet of the high-pressure compressor, so as to increase the pressure ratio of the compressor? How to improve the temperature and pressure of the exhaust gas from the tail port to make the engine have stronger thrust? How to reduce the exhaust temperature of low-pressure turbine, so as to improve the overall efficiency of the engine? How to prevent engine surge?
All these require a lot of improvements in aerodynamic and thermal schemes and a lot of experiments by researchers to explore. If these problems can't be solved, it will affect the working condition of the engine and cause serious situations such as structural damage and idle stop.
2, the material problem
(Forming Process and Crystal Structure of Turbine Blades)
Steam turbines always work under extreme high temperature and high pressure conditions, and the harsh environment has very strict requirements on its material manufacturing technology.
At present, the mainstream turbine blades in the world are mainly hollow blades made by powder metallurgy technology, and the hollow structure inside the blades has a special trend and configuration. Moreover, in order to avoid stress concentration and structural defects caused by split casting, blades and bladed disks need to be cast at one time, which is technically difficult.
In addition to turbines, the manufacture of wide chord blades of turbofan engines also requires high technology.
(Wide chord blade forming process)
For example, the blade basin/blade back titanium skin and titanium alloy honeycomb sandwich blade structure designed to reduce weight and increase strength.
In addition, diffusion bonding/superplastic forming of wide chord fan blades is also a very difficult forming process.
(hollow digging shovel)
This kind of blade adopts a wavy reinforcing structure with two titanium alloys sandwiched in the middle, which can reduce the weight and improve the strength of the whole fan blade.