I had been greatly puzzled by why so many PDF members insisted that the WS-15 engine has not been tested on J-20, and that it has running with either WS-10X or AL-31FN.
I can explain this away by thinking that non-Chinese members are simply want to knock down China's achievement, but what about Chinese members's reluctance to accept WS-15 has been tested on J-20?
The secrecy surrounding WS-15's progress has a lot to do with it, but that's not all.
A more rational explanation could be that many PDF members are not familiar with "
The Role of Computational Fluid Dynamics Analysis in Engine Design". That is using the power of supercomputer to help with engine design.
Since 2000, China has been making great stride in Supercomputer, "With over 93 petaflops of processing power, the
Sunway TaihuLight is far and away the most powerful supercomputer in the world, absolutely smashing its nearest competitor, the Tianhe-2 (another Chinese Supercomputer), which is humming away on a still-not-to-be-scoffed-at 34 petaflops."
And now US and China is tied for 171 systems each within Top500 list outlines the world's most powerful supercomputers.
The use of Supercomputers can greatly simplify the engine design process by simulate the entire engine within the computer, and model the complex airflow within it. A process that takes years to understand could now be simulated could now be modeled with only several hours of computation.
You can be sure that WS-15 engineers has spent thousands of hours in Supercomputer simulation before any parts was built. This is not an option anymore. It's a must if you want a powerful engine that pushes the limit of available materials, engine design and manufacturing process. And the insights gained and time saved by CFD is calculable.
Here is what we know about WS-15:
The WS-15 engine core pre-study was initiated in 1990 with the help of the Russian experts.
In 2000, the engine core was constructed.
15 years later, in 2005, the engine core passed all the performance test in ground bench testing.
In 2006, the WS-15 Engine Project was officially initiated.
Then the stream of official/semi-official news about WS-15 engine project ceased, it went dark.
And around this time, the J-20 design was finalized, and construction began around 2007. In 2009, the Vice Command of PLAAF announced that J-20 will soon make its first flight, and will enter service by 2017-2019.
I believe, by 2010, the first J-20 was fully assembled and first flight was made in the same year. The second J-20, with the same version number 2001, made its first flight in Jan. 11, 2011. This J-20 with the white exhaust nozzle is the WS-15 prototype, IMO.
Based on what I know about CFD, and CAD/CAM (Computer Aided Design and Manufacturing), between 2006 and 2011, IMO, it's entirely possible that Chinese engineers could have assembled a prototype of WS-15, using existing components from WS-15 and AL-31FN, so they could test it in a real setting as soon as possible.
The first WS-15 prototype, of course, would have to be first ground tested, high attitude chamber tested, and a derated WS-15 would be tested on an old plane like J-11. The J-11(
max thrust 120kN-135kN) can not test the full power (180kN) of WS-15, so it must derated or restricted. Only the J-20 designed for WS-15 can test the full thrust of WS-15.
The Engine Core consists of the Compressor, Combustor, and Turbine, but not include the afterburner assembly and exhaust nozzle.
View attachment 363389
https://www.sharcnet.ca/Software/Ansys/16.2.3/en-us/help/wb_icom/icom_cfd_role.html
"
The Role of CFD Analysis in Engine Design"
As described in
Introduction to Internal Combustion Engines, IC engines involve complex fluid dynamic interactions between air flow, fuel injection, moving geometries, and combustion. Fluid dynamics phenomena like jet formation, wall impingement with swirl and tumble, and turbulence production are critical for high efficiency engine performance and meeting emissions criteria. The design problems that are encountered include port-flow design, combustion chamber shape design, variable valve timing, injection and ignition timing, and design for low or idle speeds.
There are several tools which are used in practice during the design process. These include experimental investigation using test or flow bench setups, 1D codes, analytical models, empirical/historical data, and finally, computational fluid dynamics (CFD). Of these, CFD has the potential for providing detailed and useful information and insights that can be fed back into the design process. This is because in CFD analysis, the fundamental equations that describe fluid flow are being solved directly on a mesh that describes the 3D geometry, with sub-models for turbulence, fuel injection, chemistry, and combustion. Several techniques and sub-models are used for modeling moving geometry motion and its effect on fluid flow.
Using CFD results, the flow phenomena can be visualized on 3D geometry and analyzed numerically, providing tremendous insight into the complex interactions that occur inside the engine. This allows you to compare different designs and quantify the trade-offs such as soot vs NOx, swirl vs tumble and impact on turbulence production, combustion efficiency vs pollutant formation, which helps determine optimal designs. Hence CFD analysis is used extensively as part of the design process in automotive engineering, power generation, and transportation. With the rise of modern and inexpensive computing power and 3D CAD systems, it has become much easier for analysts to perform CFD analysis. In increasing order of complexity, the CFD analyses performed can be classified into
