To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug co...To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug cone was proposed.The performance loss mechanism caused by the recirculation flow at the rocket base and the influence of the plug cone configuration on the thrust performance were studied.Results indicated that the recirculation flow at the rocket base extended through the entire combustor,which creates an extensive range of the"low-kineticenergy zone"at the center and leads to an engine thrust loss.The plug cone serving as a surface structure had a restrictive effect on the internal flow of the engine,making it smoothly transit at the position of the large separation zone.The model RBCC engine could achieve a maximum thrust augmentation of 37.6%with a long plug cone that was twice diameter of the inner isolator.However,a shorter plug cone that was half diameter of the inner isolator proved less effective at reducing the recirculation flow for a supersonic flow and induced an undesirable flow fraction that diminished the thrust performance.Furthermore,the effectiveness of the plug cone increased with the flight Mach number,indicating that it could further broaden the operating speed range of the scramjet mode.展开更多
In this work, we investigate the possibility of achieving nanojoule level pulse energy in an all-fiber Er-doped oscillator by using a graded index multimode fiber(GIMF) as the saturable absorber(SA). This GIMF-based S...In this work, we investigate the possibility of achieving nanojoule level pulse energy in an all-fiber Er-doped oscillator by using a graded index multimode fiber(GIMF) as the saturable absorber(SA). This GIMF-based SA demonstrates the desirable characteristics of high-power tolerance, large modulation depth of 29.6%, and small saturation fluence of7.19 × 10^-3μJ∕cm^2, which contribute to the high-energy soliton generation. In the experiments, the oscillator generates stable ultrafast pulse trains with high pulse energy/average output power up to 13.65 nJ/212.4 m W in the anomalous regime and 6.25 nJ/72.5 m W in the normal regime, which are among the highest energy/average output power values achieved by all-fiber Er lasers. The results obtained demonstrate that the GIMF-based SA can be used as an effective photonic device for high-energy wave-breaking free pulse generation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11925207 and 92252206)the Hunan Province Graduate Innovation Project,China(No.XJCX2023059)。
文摘To reduce the drag generated by the recirculation flow at the rocket base in a RocketBased Combined Cycle(RBCC)engine operating in the ramjet/scramjet mode,a novel annular rocket RBCC engine based on a central plug cone was proposed.The performance loss mechanism caused by the recirculation flow at the rocket base and the influence of the plug cone configuration on the thrust performance were studied.Results indicated that the recirculation flow at the rocket base extended through the entire combustor,which creates an extensive range of the"low-kineticenergy zone"at the center and leads to an engine thrust loss.The plug cone serving as a surface structure had a restrictive effect on the internal flow of the engine,making it smoothly transit at the position of the large separation zone.The model RBCC engine could achieve a maximum thrust augmentation of 37.6%with a long plug cone that was twice diameter of the inner isolator.However,a shorter plug cone that was half diameter of the inner isolator proved less effective at reducing the recirculation flow for a supersonic flow and induced an undesirable flow fraction that diminished the thrust performance.Furthermore,the effectiveness of the plug cone increased with the flight Mach number,indicating that it could further broaden the operating speed range of the scramjet mode.
基金National Natural Science Foundation of China(61805225)
文摘In this work, we investigate the possibility of achieving nanojoule level pulse energy in an all-fiber Er-doped oscillator by using a graded index multimode fiber(GIMF) as the saturable absorber(SA). This GIMF-based SA demonstrates the desirable characteristics of high-power tolerance, large modulation depth of 29.6%, and small saturation fluence of7.19 × 10^-3μJ∕cm^2, which contribute to the high-energy soliton generation. In the experiments, the oscillator generates stable ultrafast pulse trains with high pulse energy/average output power up to 13.65 nJ/212.4 m W in the anomalous regime and 6.25 nJ/72.5 m W in the normal regime, which are among the highest energy/average output power values achieved by all-fiber Er lasers. The results obtained demonstrate that the GIMF-based SA can be used as an effective photonic device for high-energy wave-breaking free pulse generation.
