Chapter 1686 Scream and Silence

Fucheng, China Aviation Power Group Turbine Research Institute Test Center.

The SB503 high-altitude simulation test bench, which was completed only last year, is now emitting a low and majestic roar.

In the armored control room separated by a wall, a large screen is clearly displaying the three-dimensional structural cross-section of the WS-25 variable cycle engine No. 04 prototype.

The real-time status of nearly twenty key components is displayed in different color blocks, and the information data bar next to it scrolls through the current operating parameters of the SB503 aerial platform:

Simulated altitude: 15000 meters

Simulated speed: Mach 1.6

Effective thrust: 17800kgf

Core engine speed: 98.7%Nc

Bypass ratio: 0.27 (low bypass ratio turbofan mode)

……

All parameters are stable in the green safety zone. The roar of the engine can be heard through the thick observation window, deep and powerful. The casing itself is hidden in the layers of mist brought by the simulated high-altitude environment, like a giant beast breathing steadily deep in the clouds.

Deputy Chief Designer Qin Xiaoming stood in front of the central control desk, his hands behind his back, his eyes scanning every screen in front of him.

"Control, prepare to execute test sequence C-07, prepare to switch to turbojet mode."

The operator responded quickly: "Executing test sequence C-07, target turbojet mode."

Then, with a quick movement, he flipped the two stalk switches on the control panel marked "Mode Select Valve Control."

About half a second later, a ring-shaped component icon located between the high-pressure compressor and the turbine on the screen began to change from light blue to a striking yellow and flashed rapidly.

The observers simultaneously reported: "The mode selection valve is activated and the opening is increasing... Currently 5%... 10%... 15%..."

Almost at the same time as the report was delivered, the roar of the engine coming from the test bench changed significantly.

The original low sound of the turbofan was replaced by a sharper, more concentrated roar with a strong tearing feeling.

In the monitoring screen, the first-level fan speed indicator bar at the front dropped rapidly, and the number representing the speed jumped sharply, eventually returning to zero and locking.

At the same time, driven by a sophisticated variable-camber mechanism, the fan blades are adjusted from their original large installation angle, used for efficient air extraction, to a "windmill brake" posture that is almost completely perpendicular to the oncoming high-speed airflow, minimizing obstruction to the core airflow.

This is the hallmark of the turbojet operating mode.

However, the atmosphere in the control room did not relax after the switching was completed, but became even more tense.

Several engineers responsible for monitoring key parameters leaned forward slightly, their fingers hovering over the control panel or notebook.

Qin Xiaoming subconsciously clenched his fists and supported himself on the edge of the command platform.

The forearm muscles were tense due to excessive exertion, and the blue veins were clearly visible.

He held his breath and stared at the dense pressure, temperature, and flow sensor readings around the diverter ring assembly on the screen.

"Intake distortion monitoring team, report the situation!" Qin Xiaoming leaned closer to the microphone again, his voice more urgent than before.

"The distortion index Kd2 is showing a slight upward trend, and is still..." An engineer responsible for monitoring the intake system said before his tone suddenly rose. "An abnormal decrease in intake efficiency has been detected!"

Before he finished speaking, the sharp roar coming from the direction of the test bench suddenly became fluctuating, mixed with a heart-pounding, extremely high-frequency "buzzing" vibration!

On the monitoring screen, the image representing the first-level fan area was instantly covered by a glaring red warning box - the first-level fan blades were undergoing violent asynchronous vibrations. In the physical observation window, one could even vaguely see that at the huge air intake, those locked fan blades were shaking at a dangerous amplitude!

"Mode selector valve throat! Flow pattern has deviated significantly!" Almost simultaneously, the operator monitoring the diverter ring valve spoke in a hurried voice, "The airflow entering valve port C is severely congested, and the pressure pulsation index has increased dramatically! Rotating stall has occurred in the second duct... Rotating stall has occurred in the second duct, and it's spreading to the core engine!"

"Presurge!"

This cold conclusion flashed through Qin Xiaoming's mind in an instant.

Without any hesitation, he almost shouted the order:

"Emergency intervention! Close the mode selector valve! Restore turbofan operation mode immediately! Lower the simulated altitude to 10000 meters! Reduce the Mach number to 0.8!"

"Close the mode selector valve! Restore turbofan mode!"

The situation was urgent, and the operator responded to the command while pulling the lever back as quickly as possible.

A series of instructions were quickly repeated and executed.

The only sounds in the control room were the rapid commands, the alarm beeps of the instruments, and the heart-wrenching sound of the engine from the test bench, which was gradually struggling from a sharp roar to a low roar.

On the screen, the opening indicator bar of the mode selection valve dropped rapidly, and finally disappeared completely after the fan started to accelerate again and the blade angle was adjusted back to turbofan mode.

The pressure pulsation and stall signals of the second outer duct also subsided quickly.

Soon, all the key parameters on the screen stabilized back into the green safety range.

The "flight state" simulated by the SB503 high-altitude platform also smoothly transitioned to the subsonic cruising altitude, and the reassuring steady roar once again became the main theme, as if the thrilling dozen seconds just now were just a dream.

Qin Xiaoming slowly loosened his clenched fists, exhaled lightly, and suppressed his emotions:

"Record all abnormal data points and interventions. End this test sequence. Ramp down the engine, shut it down, and cool it down according to procedures."

He paused, his gaze sweeping across the engineers in the control room, each with a different expression, before finally settling on Song Fu, the head of the data analysis team.

"Team Leader Song, prioritize extracting and analyzing the test data, especially all sensor data, high-speed camera recordings, and aerodynamic parameters for the mode selector valve opening range from 72% to 100%. Once you have the preliminary results, bring everyone to my office for a meeting."

"Understood, President Qin!" Song Fu responded immediately, nodded seriously, turned around and began to arrange the work.

……

More than an hour later, in Qin Xiaoming's office.

As a temporary office, the furnishings in the room are quite simple. Apart from the office desks, chairs and reception sofas, the most eye-catching thing is the technical data cabinet that occupies one wall and the interface connected to the multimedia equipment on the wall at the entrance.

There was a knock on the door.

"Enter."

Song Fu pushed the door open and walked in, followed by three core engineers from his team, each holding a laptop or a thick folder.

Several people have taken off their heavy protective clothing and changed into dark blue regular work clothes.

However, when Song Fu's eyes swept across the reception sofa, a hint of surprise flashed across his face.

The person sitting there is the chief designer of the WS-25 dual-cycle engine, Academician Liu Yongquan.

His iconic bald head stood out in the afternoon light. His burly figure leaned relaxedly on the sofa, holding a steaming glass in his hand.

"Academician Liu!" Song Fu and the engineers behind him greeted him hurriedly.

"Well, thank you for your hard work." Liu Yongquan nodded and put down the teacup

At this moment, Song Fu also noticed the steam rising from the mouth of the cup and realized that the other party seemed to have just arrived not long ago.

His eyes lingered between Qin Xiaoming and Liu Yong for a few seconds before he finally spoke tentatively, "Just now..."

"Xiao Ming gave me a rough outline of the test results." Liu Yongquan interrupted him and said, "Just tell me your preliminary analysis and conclusions."

Somewhat surprisingly, although he already knew the result of the test failure, there was not much anxiety on his face.

There is a hint of "test" in his expression.

"Okay, Academician Liu."

After hearing this, Song Fu walked to the wall at the door and skillfully connected his laptop to the multimedia interface. The large screen on the wall lit up.

He answered while operating:

"Similar to the problems encountered in previous attempts to switch turbojet modes, when the mode selector valve was close to fully open, severe flow separation and blockage occurred in the second outer duct, inducing rotating stall, which in turn threatened the stability of the core engine."

He quickly switched the screen to a set of preliminary processed, dynamic flow state simulation cloud images.

The cloud map clearly shows the airflow velocity, pressure and streamline distribution on different sections of the engine during mode switching.