The military-industrial scientific research system of the academic master.

Chapter 1459 Breaking through thermal congestion
In fact, after JF14 was built and put into use, the development of a newer generation of ultra-high-speed wind tunnel has been put on the agenda.

However, most of the funds and personnel of the Institute of Physics, even Jiang Zongli himself who was responsible for the construction of the wind tunnel, were "diverted to other uses" by Chang Haonan, so the subsequent development task code-named JF-NG could only be carried out under the leadership of Academician Hongru.

As the first generation of wind tunnel experts in China who studied under Mr. Guo Yonghuai, Academician Yu's ability and experience are naturally beyond doubt. But after all, he is an old man of the same generation as Du Yishan. No matter how much he wants to make use of his remaining energy, physiological laws dictate that his energy and ability to accept new things are not as good as those of the younger generation.

Moreover, JF14 has reached the performance limit of the detonation-driven shock wave wind tunnel, so the new wind tunnel cannot be a simple enlargement product. It also requires a more optimized ultra-high-speed flow field, higher-precision extreme environment measurement, and a higher-intensity drive method...

All of these require an overall improvement in China's technological strength to achieve, and are definitely not the work of the Institute of Physics or the Academy of Sciences alone.

In short, up to the end of 2009, the new wind tunnel is still in the design stage. Even though the superiors have promised to increase investment, engineering work cannot be completed overnight.

Therefore, at least for a considerable period of time, Chang Haonan still needs to design and test air-breathing hypersonic aircraft based on existing equipment.

Fortunately, the gap between JF14 and the target parameters is not large, and it is impossible for Chang Haonan to come up with a complete machine solution out of thin air.

Everything has to start from scratch...

……

The nights in Huairou Science City are never truly dark.

Even though it was already three o'clock in the morning, the JF14 wind tunnel laboratory was still brightly lit.

Chang Haonan stood in front of the main console, staring at the numbers jumping on the screen. Although the expression on his face was as calm as usual, his fingers unconsciously tapped the crystal glass of the watch on his wrist.

This is a manifestation of intense inner activity.

Behind him, more than twenty researchers were standing guard at their respective posts, and the air was filled with a tense expectation.

"Academician Chang, all systems have completed final inspection and can begin testing at any time."

Xing Muchun walked up to Chang Haonan and handed him an electronic report.

This rocket expert in his early forties has now completely completed his role transformation and become a backbone force in the field of hypersonic research.

Although there were obvious dark circles at the corners of his eyes, his eyes were unusually bright.

Chang Haonan took the report and quickly glanced through it:
"Is the fuel system pressure calibrated?"

"It was recalibrated three hours ago, and the error is within 30,000ths."

Chang Haonan nodded, put the report aside, then turned to the main console. He tapped his fingers on the keyboard rapidly, calling up a three-dimensional model of a typical ramjet engine, which slowly rotated on the screen.

"Lingxiao-1" dual-mode ramjet engine.

Of course, this is just an early concept.

The part that is about to be tested is only the multi-design point combustion chamber.

This is the only feasible solution mentioned earlier that can achieve efficient wide-area operation.

When the engine operates in scramjet mode, the maximum temperature inside the combustion chamber can reach 3500K or even higher. No aviation structural material can maintain its mechanical properties in such an environment.

Therefore, similar to the turbine structure of an aircraft engine, it also requires some additional heat dissipation techniques to ensure that the entire system maintains normal operation.

The difference is that the structure of a scramjet engine is much simpler than that of a turbine engine, which is certainly an advantage in most cases, but it also reduces the effective area of ​​film cooling, which is not enough to provide sufficient heat dissipation power.

Therefore, the surface of the scramjet combustion chamber is not covered with air film holes, but with tiny cooling channels, which are as complex and orderly as the capillaries in the human body.

"Everyone, let's finally confirm the testing process."

Chang Haonan's voice was not loud, but everyone in the laboratory stopped what they were doing and turned to him.

"We will start from the subsonic ramjet mode, with an operating Mach number of 1.5, and gradually increase it to 5.0 before switching to the scramjet mode. Ideally, the ultimate goal is to reach a Mach number of 12.5, focusing on the changes in temperature distribution in the combustion chamber and the evolution of the shock wave system structure..."

His eyes swept across every face in the room:
“This is an extreme test for both the wind tunnel and the combustion chamber, and I don’t want any ‘surprises’, so safety procedures must be strictly followed and any anomalies must be reported immediately.”

A low murmur of "I understand" echoed in the laboratory.

Chang Haonan took a deep breath and turned to the main console: "Start the JF14 wind tunnel and prepare the test sequence."

Following his instructions, the entire laboratory seemed to be injected with life and began to move.

The hum of computer fans, the vibration of the cooling system starting up, and the electronic sound of equipment self-testing are intertwined. The huge wind tunnel begins to preheat, and the hydrogen-oxygen mixture gradually accumulates energy in the detonation tube.

"The wind tunnel has reached initial status!"

"Fuel system ready!"

“The data acquisition system is operating normally!”

"..."

Reports came one after another. Chang Haonan looked at the various parameters gradually rising on the main screen and felt a familiar excitement flowing through his veins.

After all, the previous "Xuanniao" was an improvement on the technology already available in the previous life, but the "Lingxiao" hypersonic propulsion system in front of us was a completely new start.

Today, they will verify the performance of the most critical multi-design point combustion chamber under simulated real working conditions.

"Begin the countdown, T-30 seconds."

Chang Haonan took a deep breath and gave an order in a deep voice at the command desk.

Xing Muchun stood in front of the temperature monitoring station, his finger hovering above the emergency stop button. His screen displayed the real-time readings of hundreds of temperature sensors arranged on the surface of the combustion chamber, all of which were currently showing room temperature.

"T-10 seconds...9...8..."

The air in the laboratory seemed to freeze, and Chang Haonan could even hear his own heartbeat between each reading.

“…3…2…1, ignite!”

There was an almost imperceptible vibration, and the curve representing thrust on the main screen suddenly jumped up.

The fuel nozzle in the combustion chamber simultaneously sprays atomized JP8 fuel, which is mixed with oxygen in the compressed air and ignited by the ignition system. The sub-combustion ramjet mode starts smoothly without any suspense.

"Mach 1.5 is stable and the combustion chamber pressure is normal."

The operator reported.

Setting Mach 1.5 as the starting speed was a well-thought-out decision.

A heavy tactical aircraft like the J-11 can reach this speed at high altitude with bombs carried by its belly, thus eliminating the length and weight of a booster rocket.

As for bombers or surface ships, they are not very sensitive to length.

As for the future reusable serious aircraft, they can be started completely autonomously through ordinary aircraft engines.

The temperature distribution diagram on the screen was as expected. A high-temperature area began to appear at the rear of the combustion chamber. The color gradually changed from blue to yellow, and finally formed a small red area near the tail nozzle. The temperature there was already over 2500K.

The key to the design of a multi-design-point combustion chamber is to move the thermal congestion position at low Mach numbers as far back as possible to leave enough space for subsequent operating conditions corresponding to higher Mach numbers.

"The shock wave system structure has been initially formed, and the consistency with CFD simulation is 88.7%."

an engineer reported excitedly.

This number may seem insignificant, but for a field that humans know very little about, it is already a level that we could not even dream of in the past.

Chang Haonan nodded slightly, but did not relax his vigilance:
"Prepare for the second test, increase the Mach number, and gradually increase it to 3.0 as planned."

The ultra-high-speed wind tunnel can actually maintain airflow for no more than 1 second, so the simulation working time cannot exceed half a minute.

Therefore, it is not possible to complete the entire process in the same test as in the actual flight.

Perhaps this is one of the reasons why our American counterparts across the ocean choose to use actual measurements instead of wind tunnels...

(End of this chapter)