This paper studies the four-engine liquid rocket flow field during the launching phase.Using threedimensional compressible Navier-Stokes equations and two-equation realizable k-epsilon turbulence model,an impact model...This paper studies the four-engine liquid rocket flow field during the launching phase.Using threedimensional compressible Navier-Stokes equations and two-equation realizable k-epsilon turbulence model,an impact model is established and flow fields of plume impinging on the two different shapes of flame deflectors,including wedge-shaped flame deflector and cone-shaped flame deflector,are calculated.The finite-rate chemical kinetics is used to track chemical reactions.The simulation results show that afterburning mainly occurs in the mixed layer.And the region of peak pressure occurs directly under the rocket nozzle,which is the result of the direct impact of exhaust plume.Compared with the wedgeshaped flame deflector,the cone-shaped flame deflector has great performance on guiding exhaust gas.The wedge-shaped and cone-shaped flame deflectors guide the supersonic exhaust plume away from the impingement point with two directions and circumferential direction,respectively.The maximum pressure and temperature on the wedge-shaped flame deflector surface are 37.2%and 9.9%higher than those for the cone-shaped flame deflector.The results provide engineering guidance and theoretical significance for design in flame deflector of the launch platforms.展开更多
The Boeing 747 and Airbus A380 passenger jets used to control long-distance traveling,a symbol of safety,distance,and status.However,advances in high-bypass turbofan engines,rising fuel prices,and growing environmenta...The Boeing 747 and Airbus A380 passenger jets used to control long-distance traveling,a symbol of safety,distance,and status.However,advances in high-bypass turbofan engines,rising fuel prices,and growing environmental pressures have made this configuration increasingly uneconomic.This project investigates three questions:why four-engine airliners have been discontinued,and what engine improvements have enabled twin-engine aircraft to replace them while still leaving essential challenges for the future.Drawing on technical textbooks,academic articles,industry reports,and historical case studies,the dissertation explains the working principles of turbofan engines,traces the development of quadjets,and compares the performance,fuel efficiency,maintenance demands,and regulatory constraints of four-and twoengine layouts.The analysis shows that modern twin-engine wide-bodies can match or exceed the range and payload of classic quadjets with much lower fuel burn and maintenance cost,especially after the relaxation of Extended-range Twin-engine Operational Performance Standards(ETOPS)rules and the shift towards pointtopoint networks.At the same time,gas-turbine technology is approaching limits in bypass ratio,temperature,and materials,while climate policy highlights unresolved CO₂and non-CO₂impacts.Future propulsion concepts such as open-rotor engines,hybrid-electric systems,and sustainable aviation fuels offer potential benefits but introduce new technical and economic trade-offs.展开更多
文摘This paper studies the four-engine liquid rocket flow field during the launching phase.Using threedimensional compressible Navier-Stokes equations and two-equation realizable k-epsilon turbulence model,an impact model is established and flow fields of plume impinging on the two different shapes of flame deflectors,including wedge-shaped flame deflector and cone-shaped flame deflector,are calculated.The finite-rate chemical kinetics is used to track chemical reactions.The simulation results show that afterburning mainly occurs in the mixed layer.And the region of peak pressure occurs directly under the rocket nozzle,which is the result of the direct impact of exhaust plume.Compared with the wedgeshaped flame deflector,the cone-shaped flame deflector has great performance on guiding exhaust gas.The wedge-shaped and cone-shaped flame deflectors guide the supersonic exhaust plume away from the impingement point with two directions and circumferential direction,respectively.The maximum pressure and temperature on the wedge-shaped flame deflector surface are 37.2%and 9.9%higher than those for the cone-shaped flame deflector.The results provide engineering guidance and theoretical significance for design in flame deflector of the launch platforms.
文摘The Boeing 747 and Airbus A380 passenger jets used to control long-distance traveling,a symbol of safety,distance,and status.However,advances in high-bypass turbofan engines,rising fuel prices,and growing environmental pressures have made this configuration increasingly uneconomic.This project investigates three questions:why four-engine airliners have been discontinued,and what engine improvements have enabled twin-engine aircraft to replace them while still leaving essential challenges for the future.Drawing on technical textbooks,academic articles,industry reports,and historical case studies,the dissertation explains the working principles of turbofan engines,traces the development of quadjets,and compares the performance,fuel efficiency,maintenance demands,and regulatory constraints of four-and twoengine layouts.The analysis shows that modern twin-engine wide-bodies can match or exceed the range and payload of classic quadjets with much lower fuel burn and maintenance cost,especially after the relaxation of Extended-range Twin-engine Operational Performance Standards(ETOPS)rules and the shift towards pointtopoint networks.At the same time,gas-turbine technology is approaching limits in bypass ratio,temperature,and materials,while climate policy highlights unresolved CO₂and non-CO₂impacts.Future propulsion concepts such as open-rotor engines,hybrid-electric systems,and sustainable aviation fuels offer potential benefits but introduce new technical and economic trade-offs.
