21届国际航天飞机和高超声速系统与技术大会全面爆发
21st AIAA International Space Planes and Hypersonics Technologies Conference

多少年来，超燃冲压就像海市蜃楼，似乎触手可及，但又总是飘然而去。仅有的成功试验早先只有秒级的工作时间，现在延长到分钟级，还都是在屡败屡战之后。但2015年国防科大王振国教授获得冯如航空科技精英奖，他是超燃冲压专家W，颁奖仪式上却对他的成果只字不提，倒是符合中国对于军工科研守口如瓶的传统。

但于3月6日由美国航空航天学会（简称AIAA）、中国工程院主办、厦门大学承办召开的21届国际航天飞机和高超声速系统与技术大会上，中国大大方方地揭示了大量成功的试验和实物图片，并透露了中国已经成功地进行了超燃冲压的飞行试验。更加惊人的是，中国研制的涡轮-火箭-冲压组合循环发动机（简称TRRE）将在2017年底前开始飞行试验，如果成功，这是世界第一。其他国家（包括美国）慢说组合循环，连具有实用意义的可持续超燃冲压都没有做到。中国尽管没有透露超燃冲压可持续工作的时间，但要是达不到至少亚小时级，研发组合循环发动机是没有意义的。这一阶段的试验将持续到2020年，在2025-30年进行水平滑跑起飞-着陆的飞行试验，如果成功，更是里程碑级的成就。

厦门会议还揭示了其他来自中国的大量重大成果，尤其是大量成果都有实物试验验证，这意味着技术水平接近或者已经达到实用程度，而不是纯理论或者纯数字仿真的空谈。比如说，国防科大已经成功测试了660毫米直径的连续旋转爆轰发动机，这是脉冲爆轰发动机的进一步发展，同样利用超燃时压力波“自我闭锁”的机理，使得燃烧的温度和压力极大升高，而且产生连续推力，可能突破涡喷、涡扇的速度和热效率局限，成为下一代喷气发动机的基本技术。北航展示了紧凑型高效换热器技术，可以将进气温度迅速降低，不仅提高进气密度和进气道效率，还对热端部件的起冷却作用，可用于减轻防热设计带来的重量，或者进一步提高热工参数，试验已经取得“令人满意”的成功。

在材料方面，中国新研制的轻质热防护材料采用仿生的陶瓷表面结构，耐热能力提高近万倍。其他新型热防护技术包括泡沫碳、陶瓷覆层和夹层隔热、波纹夹层与隔热复合结构等。中国科研人员还研究出三维碳纤维编织技术，形成三维网格复材结构，避免了传统二维复材的界面分离问题。应该指出，这些技术在航空上也有巨大价值，三维编织碳纤维风扇叶片就是C919的LEAP发动机的关键技术之一。

在理论方面，中国在高超音速非稳态流动理论、复杂流动机制和数值仿真等方面取得突破，对物理耦合现象取得深入理解，发现了新的流动现象，建立了高升阻比高超音速飞行器的最优设计方法，建立了同时达到降低热通量和降低阻力的新方法。中国还摸清了碳氢燃料的熄火极限，这是使用碳氢燃料的超燃冲压工作范围的理论极限，对设计至关重要。中国在高超音速进气道设计中采用弯曲表面的压缩面。一般来说，人们对高超音速飞行中的空气热动力学的理解还很粗浅，所以已经飞行的高超音速飞行器大多是直线、平面结构，把复杂的三维问题简化成二维。弯曲表面的压缩面代表了更高层次的技术和自信。

中国还在大量兴建高超音速风洞。理论前沿只有得到实验验证，才能成为可靠的指导工具，对于已经突破传统理论应用范围的高超音速研究来说，更是如此。中国的高超音速风洞有科学院力学所的当前世界最大的JF12风洞、航空航天院即将完工但比JF12更大的FD21风洞、国防科大的M6低噪声风洞，当然少不了绵阳的可以模拟长达600毫秒的M4-7高超音速试验装置，JF12只能模拟100毫秒。这些风洞是蓬勃兴起的中国高超音速研究的底气。

在厦门会议上，中国方面一口气发表了所有347篇论文中的272篇。如果这只是主场现象的话，2016年在亚特兰大举行的第20届会议只有89篇论文。中国军工向来有很深的保密传统，官方对很多已经在光天化日之下的“天下保守得最差的秘密”还拒不承认，慢说深藏水下、不为人们所知的真正秘密了。考虑到高超音速的军用潜力，厦门会议上中国的大动作不同寻常。美国《航空周刊》称这是中国对整个西方的叫板（a shot fired across the bow of the West）。

厦门会议还完整透露了中国的高超音速研究计划。国家自然科学基金会出资1.5亿人民币，在2007-16年之间组织了9年研究计划，涵盖全国的科研院所和高校，涉及高超音速的所有主要方面。计划分三阶段，前四年打基础，中间两年择优深入，最后三年成果集成，尤其是要有实物。整个计划有三个目标：1、健全研究体系，完善设计方法；2、取得关键技术突破；3、打造人才队伍。在厦门，不仅国家队的绵阳的国家空气动力研究与发展中心、北京的科学院力学研究所积极很活跃，航天科工集团第三研究院、三十一研究所、中航工业沈阳飞机设计研究所、中航商飞、燃气涡轮研究院、运载火箭技术研究院、国防科大、西工大、南航、北航、厦大等都有积极参加。《航空周刊》称之为协调有效、举国发力的高超音速科研计划，不仅具有惊人的深度、广度，而且在相对较短的时间里就取得了多到令人晕眩的重大成就（a cohesive, nationwide hypersonic research and technology program that not only shows astonishing depth and breadth, but has also produced a bewildering number of major accomplishments in a relatively short period）。一本正经的权威专业杂志这样堆砌惊叹词是很少有的事情。





　　3月6日，由美国航空航天学会、中国工程院主办，厦门大学承办的第21届国际航天飞机和高超声速系统与技术大会（International Spaceplane and Hypersonic Systems and Technologies Conference）在厦门大学科学艺术中心拉开帷幕。这是美国航空航天学会成立80多年来第一次在中国召开会议。校长朱崇实在开幕式上致辞。航空航天学院常务副院长尤延铖主持开幕式。
　　美国航空航天学会（AIAA）是国际标准组织（ISO）中太空系统和运营（TC 20-SC14）的书记处，是全球最大的致力于航空、航天、国防领域的科学和技术进步的专业性非政府、非赢利学会。AIAA还是世界上最大的航空航天出版机构，被公认为是航空航天文献的重要资源。此前，AIAA每年近30场系列国际会议大都在美国本土举办，还从未在中国举办过任何学术会议。
　　国际航天飞机和高超声速系统与技术大会是AIAA旗下全球最知名的航天飞机和高超声速技术交流大会，每18个月举行一次。近年来，随着我国高超声速技术的崛起，全球高超声速业界都将目光聚焦中国，厦门大学的高超声速研究也逐渐崭露头角。依托厦门大学国际化办学优势，厦门大学航空航天学院与国际高超声速业界有着紧密的交流与合作。此次会议第一次将AIAA的航天飞机和高超声速会议带到中国，对推动中美乃至全球航空航天领域尖端技术发展与交流都具有里程碑式的重要意义。
　　本次会议共吸引了来自美国、中国、英国、德国、俄罗斯、澳大利亚、日本、欧洲太空局等18个国家及国际组织的航空航天机构的知名学者和相关科研人员参加，参会人数为历年之最，其中外国专家学者百余人。作为主办方之一的中国工程院派出了尹泽勇等13名院士组成院士代表团与会。
　　开幕式上，国际高超声速技术委员会主任、美国Aerojet发动机公司的Adam Siebenhaar首先致欢迎词。他对各位嘉宾、专家学者的到来表示热烈欢迎，对本次会议的顺利召开表示衷心祝贺。
　　随后，中国工程院院士、副院长樊代明代表中国工程院致辞。他表示，空天已日益成为人类文明发展的重要领域和各国人民交往的重要纽带，而航天飞机和高超声速飞行器技术作为未来空天领域的战略制高点，受到世界航空航天强国的广泛重视和深入研究。他希望通过这个顶级会议平台，汇集来自全球知名航空航天机构专家学者、技术人员，传递最前沿科技进展和成果，促进技术的交流和智慧的碰撞，以交流促合作，以交流促发展。
　　朱崇实指出，航空航天是20世纪以来人类认识和改造自然进程最活跃、最有影响的科学技术领域之一，也是人类文明高度发展的一个重要标志。厦门大学是中国高等教育发展史上最早创办航空教育的高校之一，在航空航天事业飞速发展的今天，厦门大学的科学家们也和在座的科学家一道，致力于追求“飞得更快、更高、更安全”这一惠及人类与世界的共同目标。本次大会得以在厦门大学举办，是国际航空航天学界对中国航空航天科学发展的充分肯定。他衷心希望所有的与会代表们能够在为期4天的会议中有更多的交流、合作与收获。
　　开幕式之后，中国工程院院士、航发集团科技委主任、厦门大学航空航天学院院长尹泽勇就“面向下一代高超声速技术的航空航天教育与研究”议题作了大会特邀报告。尤延铖在会上做了“从本次大会论文看中国高超声速基础研究进展”的特邀报告。
　　除了特邀报告，会议议程由高超声速研究国家进展报告、国家重大项目进展报告、大会特邀论坛以及各专题的分组报告构成，围绕高超声速飞行器与飞行任务载荷、航天器在轨运行与任务、高超声速系统气动热与热防护、高超声速推进系统总体技术等9个专题开展学术交流。



两张北京动力机械研究所做的图，设计指标达到了6马赫且最高目标能达到10马赫

结构图，冲压部分和火箭部分共用燃烧室/进气道，注意这玩意有个涡轮泵



China Reveals Key Test Progress On Hypersonic Combined-Cycle Engine

Chinese engineers say ambitious turbo-aided rocket and scramjet are on track for 2025 flight tests
Apr 10, 2017 Guy Norris | Aviation Week & Space Technology


Hyper Hybrid

Chinese engineers will test a prototype combined-cycle hypersonic engine later this year that they hope will pave the way for the first demonstration flight of a full-scale propulsion system by 2025. If successful, the engine could be the first of its type in the world to power a hypersonic vehicle or the first stage of a two-stage-to-orbit spaceplane.

Combined-cycle systems have long been studied as a potential means to access to space and long-range hypersonic vehicles because they use both air-breathing and rocket engines to enable aircraft-like operations from a standing start to cover a wide range of speeds and altitudes. Such systems also take advantage of using atmospheric oxygen for fuel.

Various turbine, rocket and ramjet combinations have been studied in the West for decades, but it seems that a new Chinese-developed variation on this theme—the turbo-aided rocket-augmented ram/scramjet engine (TRRE)—appears to be closest to becoming the first practical combined-cycle propulsion system. Developers at the Beijing Power Machinery Research Institute say the engine will have sufficient capability to power horizontal-takeoff-and-landing hypersonic “near-space reconnaissance-and-strike” vehicles, two-stage-to-orbit and even the single-stage-to-orbit vehicles.

New Hypersonic Power Option
Turbo-aided rocket-augmented ram/scramjet combined cycle (TRRE) set for free jet testing this year

Concept combines three main propulsion systems—turbine, rockets, ram/scramjets—in just two main ducts

Capable of operations from zero to Mach 6+, with targeted top speed in Mach 10 range

Targeted at near space reconnaissance and strike platform vehicles, two-stage and single-stage-to-orbit vehicles

Although similar to several earlier combined-cycle concepts, including the Trijet proposed by Aerojet Rocketdyne in 2008, the TRRE incorporates the three main propulsion systems in just two main ducts. The TRRE consists of a turbine, liquid oxygen/kerosene-liquid-fueled rockets and a kerosene-fueled ram/scramjet combined with a common inlet and exhaust and is designed to operate from a standing start to Mach 6+. The turbine, which operates from take-off to Mach 2, is housed in an upper low-speed duct, while the ramjet and rockets are located in the lower high-speed duct. Two rockets are mounted in the duct; an aft-mounted rocket for transonic acceleration and mode transition, and a main rocket mounted farther forward in the duct for flame stabilization during acceleration through to scramjet transition at Mach 6.

Updating test progress on the TRRE at the AIAA/China Academy of Engineering International Space Planes and Hypersonic Systems conference in Xiamen, Wei Baoxi of the Beijing Power Machinery Research Institute says simulations and experiments over the past two years have “validated its comprehensive advantages for acceleration, cruise, mobility and other aspects. The results show that the TRRE engine can reconcile the demands of high thrust at lower Mach numbers and high specific impulse at a Mach number of 6.0.”

For a typical cycle, the TRRE would operate in the turbine mode for takeoff with both ejector rockets in the high-speed duct, or channel, augmenting thrust to overcome transonic drag. Around Mach 2, the low-speed duct is closed and the engine transitions to using the ramjet and rocket/ramjets in the high-speed duct. From Mach 3 to Mach 6, the engine operates in ram mode and rocket ram mode using both the high-speed inlet and the forward-mounted ejector rocket in tandem. The engine enters scramjet mode with the activation of the rocket/ramjet compound combustion chamber at Mach 6.




The TRRE combined-cycle system integrates a high-speed turbine, rockets and ramjets in an “over-under” two-duct configuration. Credit: Beijing Power Machinery Research Institute


“The main advantage of the TRRE is that it can solve the problems of an RBCC at low thrust and low speed by using the turbine engine for takeoff and landing as well as low-speed flight,” says Baoxi. “The second advantage is that with the rocket engine it solves the problem of the TBCC transition thrust ‘pinch,’ and it can also achieve a high specific thrust from Mach 3 to Mach 10. If integrated well, it will provide smooth mode transition and solve the thrust gap between the turbine and ramjet as well as provide a wide range of thrust capability between subsonic, supersonic and hypersonic conditions. It will also be good for acceleration and maneuvering. The configuration will also enhance the stability of engine operation under extreme conditions using the combustion and steady flame effect of the rocket gas jet. Using these, we can expand the boundaries of stable operation,” he adds.

Numerical test results of the TRRE prototype show it can “operate in the full flight envelope of Mach 0-6+ and have demonstrated the integrated high- and low-speed channels work cooperatively,” says Baoxi. “They also show reliable power-mode transition and the feasibility of the rocket/ramjet working in cooperation in the high-speed channel over an extremely wide speed range between Mach 1.5 and 7.” 

In 2016, developers completed inlet and nozzle wind-tunnel experiments as well as direct-connect test rig evaluations of power-mode transitions at Mach 1.8. Testing in the direct-connect rig was also performed to assess steady state performance between Mach 2 and 6. “The results verified the design methods of the TRRE inlet, nozzle and combustor. And the thrust performance obtained by the power mode transition experiments show the engine can achieve a reliable shift from the turbine mode to the rocket-ramjet mode,” says Baoxi. “When the scale effect is taken into account, thrust at the power mode shift state can reach around 16,000 lb. [8 tons] for an engine with the capture area of 1 m2, which basically meets the requirement of the vehicle design,” he adds.

One of the biggest milestones for the program will occur later this year, when developers plan to conduct free jet tests of the engine for the first time. The work will evaluate the TRRE through power-mode transitions and steady state operation at Mach 2-6 and forms the heart of the first development phase, which is focused on proving core technologies and overall operations. During this phase, which runs through 2020, Baoxi says: “We plan to adopt a small turbine for the prototype to verify the working principle.”

Baoxi indicates that the turbine for the ground prototype will be an off-the-shelf, low-bypass engine which is capable of around Mach 0.8. However, he adds that the engine will be adapted through unspecified means to represent conditions at Mach 1.8, which is the lowest mode transition speed already tested in the direct connect rig. “So it can be used to validate our operating principle,” he notes.

For the follow-on flying demonstrator, Baoxi says the turbine will likely be based on the WS-15, a super-cruising turbofan under development by Xian Aero Engine Corp. for later production versions of the twin-engine Chengdu J-20 stealth fighter. However, even though the initial batch of J-20s entered service early this year with the People’s Liberation Air Force, they are believed to be powered by an interim variant of the Russian-made Saturn AL-31 rather than the WS-15. An official quoted on the website China Military Online on March 13 commented that although WS-15 development is proceeding well, overall progress for production readiness has been hampered by quality co**ol issues with relatively recently developed areas of advanced engine technology for China, specifically single-crystal superalloy turbine blades and powder metallurgy superalloy turbine disks.

Credit: Beijing Power Machinery Research Institute


It is unclear if the targeted thrust of the WS-15 (believed to be more than 40,000 lb. when installed in the J-20) is suited to the transition Mach numbers aimed at for the flying demonstrator planned for the second development phase in the 2020-25 time frame. “Before 2025, an in-service mature turbine engine will be adopted to form the engineering program and support completion of the small horizontal-takeoff-and-landing free-flight test vehicle,” says Baoxi, who confirms the aircraft will conduct the tests from a runway rather than being air-dropped from a carrier aircraft. 

Phase three, running from 2025-30, will focus on development and integration of an advanced high-speed turbine engine into the TRRE. Program success will also hinge on parallel breakthroughs in “the operation of the scramjet at higher Mach numbers, particularly in technology areas such as the adjustable combustion chamber ramjet suitable for a wide range of work,” says Baoxi. In addition, development of a high-efficiency precooling system will be required. Preliminary work to support this is underway at various sites in China. Once combined with these enhancements, he adds, “the operating range of the TRRE engine can be further expanded.”