With the analysis on regulating system in 200 MW steam turbine, the necessity of appending the fast-opening function to the original system is set forth and a new type of fast-opening mechanism is devised. The mathema...With the analysis on regulating system in 200 MW steam turbine, the necessity of appending the fast-opening function to the original system is set forth and a new type of fast-opening mechanism is devised. The mathematical model of system is built up. With the use of AMESIM software, the displacement curve of the piston, the force curve of the cartridge valve spool, the pressure curve and the flux curve in the regulation process are obtained based on simulation. The performances of three fast-opening systems composed of cartridge valves with different diameters are compared. Based on the analysis on factors that affect the execution time of fast-opening, the dead zone of the fast-opening system is put forward. To overcome the defect, dif- ferent operation modes are adopted for different zones. The result shows that with the increase of the valve diameter, the regulating time in the dead zone significantly exceeds the fast-opening time in the whole journey. Accordingly, the optimization operation tactic in the dead zone and the qualification conditions are brought forward. The fast-opening system composed of 32 mm cartridge valves is taken as an example with use of the tactic. The simulation result shows that the maximum regulating time is shortened by 509 ms.展开更多
The rationale behind this research is the development of a zero-heM floating system using a conventional hydrokinetic water wheel as a model to examine and determine its performance in an open channel condition for en...The rationale behind this research is the development of a zero-heM floating system using a conventional hydrokinetic water wheel as a model to examine and determine its performance in an open channel condition for energy harvesting in Nigeria. The power is determined by flow of water in the stream which is responsible for rotating the blades. The research entails the water flow driven by a pump at 0.4 m/s and 0.6 m/s water velocities around a pool. The turbine is made to float under this free stream velocity. Feasibility study of its viability in Gari dam in Kano state of Nigeria was carried out and an average flow and discharge were determined during the dry season. Findings of this research were quite impressive and can be used to design a suitable floating zero-head turbine for energy harvesting in Nigerian rural areas where the head is low and energy is required not only for mechanization but also for lighting and irrigation purpose.展开更多
Parametric modeling of the impeller which drove a small wind device was built by knowledge fusion technology.NACA2410 airfoil blade was created by KF language.Using technology of UG/KF secondary development for the au...Parametric modeling of the impeller which drove a small wind device was built by knowledge fusion technology.NACA2410 airfoil blade was created by KF language.Using technology of UG/KF secondary development for the automatic modeling of wind turbine blade,the program can read in the airfoil data files automatically and the impeller model entity can be generated automatically.In order to modify the model,the aerodynamic characteristics of the impeller were analyzed for getting aerodynamic parameters by Fluent.The maximum force torch and best parameters of impeller were calculated.A physical prototype impeller was manufactured and the correctness of the design was verified,and the error of force torch between simulation and experimental results is about 10%.Parameterization design of the impeller model greatly improves the efficiency of modeling and flexibility of the CAD system.展开更多
In typical small engines, the cooling air for high pressure turbine （HPT） in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn rad...In typical small engines, the cooling air for high pressure turbine （HPT） in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot com- ponents. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are can＇ied out with axisymmetric and 3-D sector models for various inlet swirl ratio ,80 （0-0.6）, turbulent flow parameter 2-r （0.028-0,280） with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in re- ducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.展开更多
In a gas turbine engine combustor, highly swiding combustion is usually adopted to stabilize flame and reduce pollutant emissions. Swirl cup, as an air blast atomizer, is widely used to provide a uniform presentation ...In a gas turbine engine combustor, highly swiding combustion is usually adopted to stabilize flame and reduce pollutant emissions. Swirl cup, as an air blast atomizer, is widely used to provide a uniform presentation of fuel droplets to the combustor dome. This paper investigated the effect of secondary swirler on the flow field down- stream of the swirl cup using particle image velocimetry （PIV）. Three swirl cups＇ non-reacting flow field were studied： case A, B and C with secondary swirler vane angle 53°, 60° and 68° respectively. Detailed mean and transient velocities and vorticity in the center plane were obtained. From the PIV results, a sharp contrast flow field was obtained for case A to other two cases due to the lower secondary swirling intensity. The recirculation zone is collapsed in disorder for the case A. Ignition tests of the three cups were completed in a single cup com- bustor. In general, the ignition performance increases with the increasing of the secondary swirling intensity. For case A, the ignition performance is very unstable and has much randomness and there is no clear lean ignition boundary can be generated. This work can further understand the swirl behavior and ignition mechanism.展开更多
Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is...Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is discussed in this paper,including blowing momentum and circumferential locations of the microblowing hole of 0.5 mm in diameter on nose tip.A new kind of active control technique,named perturbation-combined active control technique,which combines the micro-grain and micro-blowing perturbation,was proposed on the basis of the above.This control technique can not only change the sign of side force of slender body arbitrarily through changing the vortices positions between yaw-left and yaw-right configuration,but also can make the magnitude of side force variable gradually even at bistable state of asymmetric vortex.Finally,the interferential mechanism of the perturbation-combined active control technique has also been concluded from this paper.The tests have been conducted at low speed wind tunnel with subcritical Reynolds number of 1.05×10~5 at angle of attack α=50° in Beihang University,Beijing,China.展开更多
基金Project (No. NCET-04-0545) supported by the "New Century Elitist Supporting Plan" Fund Project of Education Ministry of China
文摘With the analysis on regulating system in 200 MW steam turbine, the necessity of appending the fast-opening function to the original system is set forth and a new type of fast-opening mechanism is devised. The mathematical model of system is built up. With the use of AMESIM software, the displacement curve of the piston, the force curve of the cartridge valve spool, the pressure curve and the flux curve in the regulation process are obtained based on simulation. The performances of three fast-opening systems composed of cartridge valves with different diameters are compared. Based on the analysis on factors that affect the execution time of fast-opening, the dead zone of the fast-opening system is put forward. To overcome the defect, dif- ferent operation modes are adopted for different zones. The result shows that with the increase of the valve diameter, the regulating time in the dead zone significantly exceeds the fast-opening time in the whole journey. Accordingly, the optimization operation tactic in the dead zone and the qualification conditions are brought forward. The fast-opening system composed of 32 mm cartridge valves is taken as an example with use of the tactic. The simulation result shows that the maximum regulating time is shortened by 509 ms.
文摘The rationale behind this research is the development of a zero-heM floating system using a conventional hydrokinetic water wheel as a model to examine and determine its performance in an open channel condition for energy harvesting in Nigeria. The power is determined by flow of water in the stream which is responsible for rotating the blades. The research entails the water flow driven by a pump at 0.4 m/s and 0.6 m/s water velocities around a pool. The turbine is made to float under this free stream velocity. Feasibility study of its viability in Gari dam in Kano state of Nigeria was carried out and an average flow and discharge were determined during the dry season. Findings of this research were quite impressive and can be used to design a suitable floating zero-head turbine for energy harvesting in Nigerian rural areas where the head is low and energy is required not only for mechanization but also for lighting and irrigation purpose.
基金Project(gjd-09041)supported by the Natural Science Foundation of Shanghai Municipal Education Commission,China
文摘Parametric modeling of the impeller which drove a small wind device was built by knowledge fusion technology.NACA2410 airfoil blade was created by KF language.Using technology of UG/KF secondary development for the automatic modeling of wind turbine blade,the program can read in the airfoil data files automatically and the impeller model entity can be generated automatically.In order to modify the model,the aerodynamic characteristics of the impeller were analyzed for getting aerodynamic parameters by Fluent.The maximum force torch and best parameters of impeller were calculated.A physical prototype impeller was manufactured and the correctness of the design was verified,and the error of force torch between simulation and experimental results is about 10%.Parameterization design of the impeller model greatly improves the efficiency of modeling and flexibility of the CAD system.
基金supported by the National Natural Science Foundation of China(Grant No.51306177)
文摘In typical small engines, the cooling air for high pressure turbine （HPT） in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot com- ponents. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are can＇ied out with axisymmetric and 3-D sector models for various inlet swirl ratio ,80 （0-0.6）, turbulent flow parameter 2-r （0.028-0,280） with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in re- ducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.
文摘In a gas turbine engine combustor, highly swiding combustion is usually adopted to stabilize flame and reduce pollutant emissions. Swirl cup, as an air blast atomizer, is widely used to provide a uniform presentation of fuel droplets to the combustor dome. This paper investigated the effect of secondary swirler on the flow field down- stream of the swirl cup using particle image velocimetry （PIV）. Three swirl cups＇ non-reacting flow field were studied： case A, B and C with secondary swirler vane angle 53°, 60° and 68° respectively. Detailed mean and transient velocities and vorticity in the center plane were obtained. From the PIV results, a sharp contrast flow field was obtained for case A to other two cases due to the lower secondary swirling intensity. The recirculation zone is collapsed in disorder for the case A. Ignition tests of the three cups were completed in a single cup com- bustor. In general, the ignition performance increases with the increasing of the secondary swirling intensity. For case A, the ignition performance is very unstable and has much randomness and there is no clear lean ignition boundary can be generated. This work can further understand the swirl behavior and ignition mechanism.
基金supported by the National Natural Science Foundation of China (Grant No. 10872019)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20101102110015),NCET-06-0176
文摘Based on the determinability of asymmetric vortices flow over slender body under changeless round grain at high angle of attack,the effect of microblowing set in special position on the behaviors of asymmetric flow is discussed in this paper,including blowing momentum and circumferential locations of the microblowing hole of 0.5 mm in diameter on nose tip.A new kind of active control technique,named perturbation-combined active control technique,which combines the micro-grain and micro-blowing perturbation,was proposed on the basis of the above.This control technique can not only change the sign of side force of slender body arbitrarily through changing the vortices positions between yaw-left and yaw-right configuration,but also can make the magnitude of side force variable gradually even at bistable state of asymmetric vortex.Finally,the interferential mechanism of the perturbation-combined active control technique has also been concluded from this paper.The tests have been conducted at low speed wind tunnel with subcritical Reynolds number of 1.05×10~5 at angle of attack α=50° in Beihang University,Beijing,China.
