Flow velocity in the fuel/oxidizer injectors and combustion chamber during combustion oscillations in a model of a rocket engine. (Courtesy: Hiroshi Gotoda)
Researchers in Japan have identified a feedback loop that drives damaging combustion oscillations in rocket engines. They found that thermoacoustic power sources created as the oxidizer and fuel flow into the engine’s combustion chamber lead to highly synchronized fluctuations in fuel flow, pressure and heat.
Combustion engines power much of our transport technology and are also used in turbines for power generation. But these engines can develop high-frequency oscillations, which cause structural damage, shortening the life span of combustors and potentially making them unsafe.
“Thermoacoustic combustion oscillations, which are a self-sustaining instability, arise from the strong mutual coupling among hydrodynamics, acoustic waves and heat release rate fluctuations inside a combustor,” Hiroshi Gotoda, a mechanical engineer at Tokyo University of Science, tells Physics World. He notes that they are classified according to combustion chamber pressure fluctuations, depending on the range of dominant frequencies in the chamber, as low- (50 Hz), intermediate- (50–1000 Hz) and high-frequency (above 1000 Hz) oscillations.
Gotoda adds that these combustion oscillations hinder the development of combustors for rocket and aircraft engines, and land-based gas-turbine power ...