Chapter 1685: Always Give Back to the Old Business

Two days later, Beijing.

China United Aviation Power Group headquarters building.

Chang Haonan, along with his guards, pushed open the soundproof door of a small conference room on the top floor.

Inside, around ten people were already sitting around the oval conference table. They were all key designers from the core research institutes under the Aviation Industry Corporation of China.

The burly bald man in the lead was none other than Academician Liu Yongquan, who was now the group's chief engineer and chief engineer of the variable cycle engine project.

Seeing Chang Haonan come in, at Liu Yongquan's signal, everyone stood up and a brief and restrained applause rang out in the conference room.

Chang Haonan raised his hand and pressed down twice, signaling everyone to sit down.

"Everyone, it's been a while."

He walked towards the main seat while greeting his old friends.

Liu Yongquan skillfully helped Chang Haonan open the multimedia control system interface embedded in the desktop, and said half-jokingly:

"Mr. Chang, it's been a while since you've personally attended our technical coordination meetings... We've all been secretly worried that you might have forgotten about our 'traditional projects'."

"Forgot?" Chang Haonan skillfully plugged the video cable into the laptop's port. He shook his head and laughed, "No one can forget how to eat."

He looked around at the experts present, his tone filled with a hint of relief:

"It's just that in the aerospace engine sector... everyone has worked very hard over the years, overcoming many tough challenges. The situation is stable and steady. The opponent probably feels that there is no opportunity for them to exploit the situation for the time being, so they haven't considered this a major 'battleground'."

"No, as soon as the situation over there stabilized, I rushed over."

Hearing this, everyone present involuntarily straightened up a little.

Just over a decade ago, aero engines were an obvious shortcoming in China's aviation system and even the entire industrial system.

But now it has become a hard-footed crab that others dare not name.

Of course, Chang Haonan made great contributions to this, but others also made outstanding efforts.

Zhang Zhenhua, who was sitting opposite Liu Yongquan, also took over the conversation:

"Mr. Chang, Academician Liu, speaking of this, I was deeply touched when I went to Shanghai to assist in hosting the Etihad delegation."

He signed a package deal with Etihad Airways yesterday and returned to Beijing from Shanghai a few hours ago:

"I used to subconsciously think that our CAAC certification was inferior to EASA and FAA, and I was worried that users would not accept it. But it turns out that the oil tycoons saw it more clearly and didn't take the airworthiness mutual recognition agreement seriously at all. They directly stated that as long as the CAAC certification is passed, they will also recognize it..."

Liu Yongquan nodded:

"The situation has indeed changed too rapidly, especially over the past six months. We have been confronting Washington's all-around suppression head-on, and ultimately gained the upper hand. This has caused many people, even many of our own people, to finally realize that the balance of power has shifted."

Zhang Zhenhua laughed self-deprecatingly at the words: "Not to mention others, even I haven't really adjusted my mindset yet."

"It's inevitable to feel uncomfortable at work, but you just have to get used to it slowly..."

As he spoke, the projection was fully ready.

Chang Haonan stopped chatting and clicked on an encrypted file labeled "Topological Dimensionality Reduction Analysis of Three-Dimensional Flow Field of Variable Geometry Diverter Ring".

A set of highly abstract framework diagrams consisting of complex topological structures and partial differential equations emerged.

"Okay, let's put aside the reminiscing and sentimentalizing for now."

He cleared his throat and began today's topic seriously:

"Everyone here is a veteran in the aeroengine field, and aerodynamics is one of the most direct and mature fields for applying the general solution of the NS equations. Therefore, I will not start with the basics in today's meeting."

Chang Haonan clicked the mouse to switch the projection screen.

A three-dimensional design of a mechanical device with an intricate structure and a ring-shaped layout occupied the entire screen.

The fine connecting rods, delicate hinge points and layered fan blade structure are clearly visible.

He pointed the red dot of his laser pointer at the ring-shaped device on the screen. "This is the design proposal for the variable geometry splitter ring on the fifth-generation WS-25 dual-cycle engine submitted by Comrade Yongquan three months ago."

As he said this, he looked to his left at Liu Yongquan.

The latter leaned forward slightly, nodded, and then explained, "Yes, this splitter ring is one of the core actuating mechanisms that enables the WS-25 to achieve 'triple mode', seamlessly switching between subsonic cruise turbofan, supersonic turbofan, and high-speed turbojet. It is integrally installed on the intermediate casing behind the fan outlet and before the high-pressure compressor inlet."

He used his fingers to indicate the key structures on the screen:

"The core structure consists of paired main blades, whose roots are hinged to the inner end wall of the intermediate casing via precision shafts. A smaller sub-blade is hinged to the upper and lower surfaces of each main blade. The core operating logic of the entire mechanism is that when the splitter ring needs to transition from a converging state (high bypass ratio, turbofan mode) to an expanding state (low bypass ratio, approaching turbojet mode), the bypass ratio decreases accordingly."

"The power source for this movement is provided by an electro-hydraulic system, which drives a precise spatial multi-link mechanism through an actuator. This mechanism first causes the main blade to precisely deflect around its root hinge. At the same time, the linkage mechanism activates a set of bevel gear pairs to synchronously drive the sub-blades, causing them to rotate precisely and fit into the gap area between adjacent main blades due to expansion..."

"..."

"The core purpose of this coordinated movement of the mother and child blades is to minimize or even eliminate the airflow leakage and off-design flow separation that are unavoidable in traditional variable geometry mechanisms during actuation, thereby achieving a more efficient, smoother, and less aerodynamically lossy transition between the three modes."

After introducing the basic structure, Liu Yongquan paused for a moment, then his tone became serious:

“目前，这套设计方案的01号和02号原型件已经安装在了涡扇25的03号、04号原型机上进行地面台架测试，但最大的挑战在于理论模型。”

"The two-dimensional aerodynamic model of the flow splitter section that we currently use to support our design is based on simplified assumptions. This model cannot effectively handle the inherent strong nonlinearity and multi-degree-of-freedom coupling problems in transonic flow, especially in the mode switching transition state."

He sighed slightly:

"Specifically, the model struggles to accurately reconstruct the complex vortex interactions between the first duct (core flow) and the second duct (outer duct) during variable geometry, and their resulting disturbances to the downstream compressor inlet flow field. Furthermore, it is unable to accurately describe the transient aerodynamic loads and flow stability boundaries at the moment of switching between different modes. This has led us to rely heavily on extensive and costly iterative trial-and-error testing and high-density ground testing."

"The time pressure is enormous," Liu Yongquan said, frowning. "The next-generation fighter jet project, which Shengjing is responsible for, adapted for the WS-25, is already very advanced in its overall progress. Furthermore, for well-known reasons, the Navy's carrier-based aviation force also hopes to quickly acquire a carrier-based aircraft with powerful supersonic cruise and omnidirectional stealth capabilities to replace the J-15 series."

The others also nodded.

As the balance of power across the Pacific gradually changes, the possibility of Washington choosing to take risks is gradually increasing.

The more times like this happen, the more we need strong military deterrence to force the other side to maintain sufficient strategic determination.

Liu Yongquan continued:

"Therefore, if a decisive breakthrough cannot be made in the short term on the variable geometry splitter ring problem, we will likely have to cancel the dual-cycle function on the first batch of mass-produced WS-25s and revert to a single-cycle solution with a relatively simple structure but significantly limited performance potential. This will have a significant negative impact on the fighter's full-envelope performance and future upgrade space."

Chang Haonan listened quietly to Liu Yongquan's detailed explanation. When he was about to finish his words, he gently waved his hand to signal a pause.

"From today on, we can completely put aside that two-dimensional model."

He said this with a very firm tone:

"For aircraft engines operating below conventional hypersonic speeds, we can directly calculate accurate results for internal flow field problems during the design phase using the general solution of the NS equations, as long as they do not involve the core combustion chamber area with extremely high temperatures and extreme chemical reactions."

The conference room suddenly became so quiet that you could hear a pin drop. All eyes were focused on Chang Haonan and the large screen behind him.

"Not only that." Chang Haonan slowly stood up and walked to the side of the screen. "If the aircraft equipped with this engine has been designed, then we can even provide an optimal solution with the highest adaptability based on the parameters!"