Although it has been explored for several decades, supersonic flight has never
been able to rise to the same level as other propulsion technologies. The main
reason lies in the technical difficulties it poses, and the physico-mechanical
problems it can generate, as in the case of the infamous Concorde. However, a
team of Chinese engineers recently announced the development of a new type of
supersonic engine, the Sodramjet, which overcomes the classic obstacles posed
by this type of engine. Although the first experimental tests were conclusive,
a long work still awaits the researchers before a potential commercialization.
Since the retirement of the Concorde, commercial supersonic flight has been
put on hold in Western countries. While innovation in faster engines
continued, some serious issues with high speed engines prevented their
development. Therefore, instead of pushing the speed limits, engineers
focused on increasing fuel efficiency, reducing the carbon footprint of
airliners, and increasing passenger capacity. However, a Chinese team has
never taken their eyes off supersonic flight, and recently they took a big
step forward.
According to the team, their new hypersonic jet engine can reach speeds of
up to Mach 16 - or 19,000 kilometers per hour - and was stable when tested
in a wind tunnel. Attach it to a plane and you can be anywhere in the world
in two hours, according to the authors. The results were published in the
Chinese Journal of Aeronautics.
The technical obstacles posed by the scramjet
The team says their engine, called Sodramjet, represents a significant
advance in hypersonic propulsion. “Research over more than 70 years on
hypersonic propulsion indicates that a revolutionary concept is really
needed for the development of hypersonic engines. The concept of the
Sodramjet engine may be a very promising choice and the work presented here
strongly supports this idea,” the authors write in the article
The Sodramjet builds on existing technology known as a ramjet, which has
been in development since Hungarian inventor Albert Fonó used a crude ramjet
to increase the range of artillery. While normal jet engines use a
compressor section of fan blades to compress intake air before sending it
for combustion, ramjets rely on the forward motion of the plane to provide a
compressed air flow and fast moving.
A breakthrough was then made on ramjets to produce a supersonic combustion
model (scramjet), which keeps air flowing through the engine at supersonic
speeds, unlike a ramjet which slows the air before combustion. But scramjets
suffer from fatal flaws. Supersonic air creates shock waves that can block
burning fuel.
Sodramjet: a supersonic engine with promising results
Instead, Zonglin Jiang and his colleagues at the Chinese Academy of Sciences
in Beijing turned to the work of engineer Richard Morrison in 1980. He
believed that the shock wave produced by the supersonic air could contain
enough energy to continuously re-ignite the motor and maintain speeds of
Mach 15 or more. Although his ideas never saw commercial application due to
a lack of funding and the choice to pursue other ideas, Jiang put the idea
into practice in the Sodramjet, and the results speak for themselves.
themselves.
The Sodramjet was stable at hypersonic speeds and burned its hydrogen more
efficiently as the speeds increased. The results prove that intrinsic shock
waves in a hypersonic engine can sustain internal combustion, in line with
Morrison's ideas nearly 40 years ago.
Although incredible, the Sodramjet engine is still a long way from being used
in a commercial airliner. In addition, there are still issues to be resolved
before the engine is fully functional. The shock waves that reignite
combustion can sustain the thrust, but in so doing, produce surges in the
engine that impact its stability. Additionally, speeds of this nature have
been described in wind tunnels using scramjets before, but have not been
verified on airplanes, so the engine will require much more testing before
commercial use.
Reference:
The criteria for hypersonic airbreathing propulsion and its experimental
verification
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