Turbofan engine is very important for civil aviation.The fan as a crucial component,its internal flow mechanisms is more complex and the loss mechanisms analysis is more difficult with the demand for greener,more effi...Turbofan engine is very important for civil aviation.The fan as a crucial component,its internal flow mechanisms is more complex and the loss mechanisms analysis is more difficult with the demand for greener,more efficient aircraft engines.In this paper,taking Rotor67,a high-load fan rotor,as the research object.Using the physical characteristics of the fluid in the computational fluid dynamics(CFD)results,the losses are divided into five loss regions:shock loss,boundary layer loss,tip clearance leakage loss,corner separation loss and wake loss.Each region is defined by the flow physics in the CFD results combined with geometrical locations.Three operating conditions of design point,near stall point and choke point are taken into account,and the loss of each loss zone is quantified by using the entropy rate analysis theory,which provides a basis for the loss analysis of transonic fan and blade optimization.展开更多
Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We e...Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We examine the impact of the spectral loss and propose robust comb generation with a loss of even 300 dB/cm.Cavity nonlinear dynamics show that a phase change associated with spectral losses can facilitate phase matching and Kerr comb generation. Given this unique capability, we propose a novel architecture of on-chip spectroscopy systems.展开更多
To control the transition process in a laminar separation bubble(LSB)over an ultra-high load compressor blade at a Re of 1.5×10^(5),the effects of wall heat transfer were considered and numerically investigated b...To control the transition process in a laminar separation bubble(LSB)over an ultra-high load compressor blade at a Re of 1.5×10^(5),the effects of wall heat transfer were considered and numerically investigated by large eddy simulations(LES).Compared with the adiabatic wall condition,the local kinematic viscosity of airflow was reduced by wall cooling;thus the effects of turbulent dissipation on the growth of fluctuations were weakened.As such,the transition occurred much earlier,and the size of LSB became smaller.On the cooled surface,the spanwise vortices deformed much more rapidly and the size of hairpin vortex structures was decreased.Furthermore,the rolling-up of 3D hairpin vortices and the ejection and sweeping process very close to the blade surface was weakened.Correspondingly,the aerodynamic losses of the compressor blade were reduced by 18.2%and 38.4%for the two cooled wall conditions.The results demonstrated the feasibility of wall cooling in controlling the transition within an LSB and reducing the aerodynamic loss of an ultra-highly loaded compressor blade.展开更多
基金National Natural Science Foundation of China(52176035,51776018)。
文摘Turbofan engine is very important for civil aviation.The fan as a crucial component,its internal flow mechanisms is more complex and the loss mechanisms analysis is more difficult with the demand for greener,more efficient aircraft engines.In this paper,taking Rotor67,a high-load fan rotor,as the research object.Using the physical characteristics of the fluid in the computational fluid dynamics(CFD)results,the losses are divided into five loss regions:shock loss,boundary layer loss,tip clearance leakage loss,corner separation loss and wake loss.Each region is defined by the flow physics in the CFD results combined with geometrical locations.Three operating conditions of design point,near stall point and choke point are taken into account,and the loss of each loss zone is quantified by using the entropy rate analysis theory,which provides a basis for the loss analysis of transonic fan and blade optimization.
基金National Basic Research Program of China(973)(2014CB340104/3,61775164,61335005,61377076,61575142,61431009)Advanced Integrated Optoelectronics Facility at the Tianjin University
文摘Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be detrimental. We examine the impact of the spectral loss and propose robust comb generation with a loss of even 300 dB/cm.Cavity nonlinear dynamics show that a phase change associated with spectral losses can facilitate phase matching and Kerr comb generation. Given this unique capability, we propose a novel architecture of on-chip spectroscopy systems.
基金the financial support of the Science Center for Gas Turbine Project(2022-B-Ⅱ-008)Open project of the State Key Laboratory of Aerodynamics(SKLA-20190105)。
文摘To control the transition process in a laminar separation bubble(LSB)over an ultra-high load compressor blade at a Re of 1.5×10^(5),the effects of wall heat transfer were considered and numerically investigated by large eddy simulations(LES).Compared with the adiabatic wall condition,the local kinematic viscosity of airflow was reduced by wall cooling;thus the effects of turbulent dissipation on the growth of fluctuations were weakened.As such,the transition occurred much earlier,and the size of LSB became smaller.On the cooled surface,the spanwise vortices deformed much more rapidly and the size of hairpin vortex structures was decreased.Furthermore,the rolling-up of 3D hairpin vortices and the ejection and sweeping process very close to the blade surface was weakened.Correspondingly,the aerodynamic losses of the compressor blade were reduced by 18.2%and 38.4%for the two cooled wall conditions.The results demonstrated the feasibility of wall cooling in controlling the transition within an LSB and reducing the aerodynamic loss of an ultra-highly loaded compressor blade.
