With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the coal-fired plants are expected in order to reach the goals set in the Kyoto protocol.It can be achieved by ...With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the coal-fired plants are expected in order to reach the goals set in the Kyoto protocol.It can be achieved by a rise of the process parameters.Currently,live steam pressures and temperatures up to 300 bars and 923 K are planned as the next step.Closed circuit steam cooling of blades and vanes in modern steam turbines is a promising technology in order to establish elevated live steam temperatures in future steam turbine cycles.In this paper,a steam-cooled test vane in a cascade with external hot steam flow is analyzed numerically with the in-house code CHTflow.A parametric analysis aiming to improve the cooling effectiveness is carried out by varying the cooling mass flow ratio.The results from two investigated cases show that the steam cooling technique has a good application potential in the steam turbine.The internal part of the vane is cooled homogeneously in both cases.With the increased cooling mass flow rate,there is a significant improvement of cooling efficiency at the leading edge.The results show that the increased cooling mass flow ratio can enhance the cooling effectiveness at the leading edge.With respect to trailing edge,there is no observable improvement of cooling effectiveness with the increased cooling mass flow.This implies that due to the limited dimension at the trailing edge,the thermal stress cannot be decreased by increasing the cooling mass flow rate.Therefore,impingement-cooling configuration at the trailing edge might be a solution to overcome the critical thermal stress there.It is also observed that the performance of the cooling effective differs on pressure side and suction side.It implicates that the equilibrium of the cooling effectiveness on two sides are influenced by a coupled relationship between cooling mass flow ratio and hole geometry.In future work,optimizing the hole geometry and cooling steam supply conditions might be the solutions for an equivalent cooling effectiveness along whole profile.展开更多
The Double-Jet Film-Cooling （DJFC） technology is invented by the authors and comprises a significant enhancement of the adiabatic film-cooling effectiveness due to the formation of anti-kidney vortices. The DJFC tec...The Double-Jet Film-Cooling （DJFC） technology is invented by the authors and comprises a significant enhancement of the adiabatic film-cooling effectiveness due to the formation of anti-kidney vortices. The DJFC technology places a second ejection hole with compound angle in a double-hole arrangement downstream the first hole. The second hole creates a second jet with another dominating vortex rotating in opposite direction to the first one and then combines both jets to one jet. The basic applicability and function of the DJFC technology has been proven by the numerical studies and testing in a test rig. The comparison of the experimental results of the adiabatic film cooling effectiveness to the numerical results for the same blowing ratio （M=（pc）c/（pc）h） shows qualitatively similar distributions. However, the experimental results show enhanced mixing-out of the cooling air and, thus, the experimental values of the adiabatic film cooling effectiveness are lower compared to the numerical values.展开更多
With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the power plants are expected in order to reach the goals set in the Kyoto protocol.In comparison to convention...With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the power plants are expected in order to reach the goals set in the Kyoto protocol.In comparison to conventional systems,the hybrid-systems with the use of synergetic effects offer the possibility to provide a substantial contribution to spare our natural resources and protect our environment.Combined Cycle Power Plants belongs innately hybrid system in the centralized energy market.They can provide large amounts of power and have a quick start-up time.The MGT/FC hybrid system is quite promising in the decentralized energy market.It is widely used in stand-alone applications.Furthermore,the combination of fossil and renewable power plant technologies contains a large synergy potential to increase the efficiency of processes for power plants.New materials,innovative cooling technology,new combustion concepts and optimized production methods are needed to make the potential of these new technologies accessible for a quantum leap in the efficiency.For this it needs considerable research work and good coordinated research projects between the state,industry,research laboratories and universities.展开更多
This study is an advanced investigation for the cooling of high temperature turbine vanes and blades. The efficient heat exchanging near the surface of a blade may be achieved by forcing a cooling air flow emitting ou...This study is an advanced investigation for the cooling of high temperature turbine vanes and blades. The efficient heat exchanging near the surface of a blade may be achieved by forcing a cooling air flow emitting out of a thin layer of the porous metal which is pasted on the structural high strength metal. The contents include the consideration on the computational model of heat transfer through a layer of porous material, the concrete modeling and the analysis of the model, the numerical survey of key parameters for both the two-layer porous materials and the heat transfer fluid flow passing through the model channels. The results revealed that the constructed system is reasonable. Proposed an evaluation formula for the porous material heat transfer efficiency.展开更多
This paper presents preliminary measurements of a 2-stage axial turbine with shrouded rotor cavities. The research facility and measurement techniques are reported. The flow field at both inlet and outlet was measured...This paper presents preliminary measurements of a 2-stage axial turbine with shrouded rotor cavities. The research facility and measurement techniques are reported. The flow field at both inlet and outlet was measured using 5-hole probes as well as temperature probes. The measurement results indicate that the inlet flow field is periodical in the tangential direction due to the influence of the first-stator leading-edge. The horse-shoe vortexes cause substantial flow blockage and turbulence near the endwall. Unsteady measurements of the rotor radial tip clearance show that one of the second-rotor blades has a little bigger clearance than the others.展开更多
In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and co...In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements.The numerical results in agreement with the available experiments show large-scale instabilities.The disk local Nusselt numbers show mainly radial rising distributions for the heated disks with radial rising temperature profiles.In the present work,at the Reynolds number of 20 000,the disk local Nusselt numbers are the correlations of the local Grashof number to the power of 1.89-2.6,and the value of the power is increased as the rotational Reynolds number goes up.At the rotational Reynolds number of 800 000,the local Nusselt numbers are the correlations of the local Grashof number to the power of 0.68-2.6,and the value of the power is decreased as Reynolds number goes up.The area-averaged disk Nusselt number is the correlation of the Reynolds number to the power of 0.479 and the rotational Grashof number to the power of 0.12.展开更多
The goal of Collaborative Research Centre(SFB) 561 "thermally highly loaded,porous and cooled multi-layer systems for combined cycle power plants" is to expand the current technological and scientific knowle...The goal of Collaborative Research Centre(SFB) 561 "thermally highly loaded,porous and cooled multi-layer systems for combined cycle power plants" is to expand the current technological and scientific knowledge on power plants in order to achieve total efficiencies of 65% in a combined cycle power plant in the year 2025.Therefore,the aero-thermomechanical,structural-mechanical,materials' scientific and production fundamentals for the development of steam and gas turbine components that are able to withstand highest thermal loads are being worked out within this SFB.This means for the gas turbine that combustion chamber outlet temperatures of 1520℃ at 1.7MPa are to be attained.In order to control these high temperatures,it is not only required to develop new materials' solutions,including thermal barrier coatings,but also to apply improved cooling techniques,as for example effusion cooling.This novel cooling concept is to be realised through open-porous structures.These structures can consist of drilled open-porous multi-layer systems or open-porous metallic foams.The development of graded multi-layer systems is also extremely important,as the grading will enable the use of coolant in dependence of the requirements.The live steam parameters in the high pressure turbine are expected to be increased up to approximately 700℃ with pressure of 30MPa.These elevated steam parameters can be encountered with Ni-base alloys,but this is a costly alternative,associated with many manufacturing difficulties.Therefore,the SFB proposes cooling the highly loaded turbines instead,as this would necessitate the application of far less Ni-base alloys.To protect the thermally highly loaded casing,a sandwich material consisting of two thin face sheets with a core of a woven wire mesh is used to cover the walls of the steam turbine casing.The current state of the research shows that by utilising innovative cooling technologies a total efficiency of 65% can be reached without exceeding the maximum allowable material temperature,thereby prolonging the life-span.展开更多
文摘With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the coal-fired plants are expected in order to reach the goals set in the Kyoto protocol.It can be achieved by a rise of the process parameters.Currently,live steam pressures and temperatures up to 300 bars and 923 K are planned as the next step.Closed circuit steam cooling of blades and vanes in modern steam turbines is a promising technology in order to establish elevated live steam temperatures in future steam turbine cycles.In this paper,a steam-cooled test vane in a cascade with external hot steam flow is analyzed numerically with the in-house code CHTflow.A parametric analysis aiming to improve the cooling effectiveness is carried out by varying the cooling mass flow ratio.The results from two investigated cases show that the steam cooling technique has a good application potential in the steam turbine.The internal part of the vane is cooled homogeneously in both cases.With the increased cooling mass flow rate,there is a significant improvement of cooling efficiency at the leading edge.The results show that the increased cooling mass flow ratio can enhance the cooling effectiveness at the leading edge.With respect to trailing edge,there is no observable improvement of cooling effectiveness with the increased cooling mass flow.This implies that due to the limited dimension at the trailing edge,the thermal stress cannot be decreased by increasing the cooling mass flow rate.Therefore,impingement-cooling configuration at the trailing edge might be a solution to overcome the critical thermal stress there.It is also observed that the performance of the cooling effective differs on pressure side and suction side.It implicates that the equilibrium of the cooling effectiveness on two sides are influenced by a coupled relationship between cooling mass flow ratio and hole geometry.In future work,optimizing the hole geometry and cooling steam supply conditions might be the solutions for an equivalent cooling effectiveness along whole profile.
文摘The Double-Jet Film-Cooling （DJFC） technology is invented by the authors and comprises a significant enhancement of the adiabatic film-cooling effectiveness due to the formation of anti-kidney vortices. The DJFC technology places a second ejection hole with compound angle in a double-hole arrangement downstream the first hole. The second hole creates a second jet with another dominating vortex rotating in opposite direction to the first one and then combines both jets to one jet. The basic applicability and function of the DJFC technology has been proven by the numerical studies and testing in a test rig. The comparison of the experimental results of the adiabatic film cooling effectiveness to the numerical results for the same blowing ratio （M=（pc）c/（pc）h） shows qualitatively similar distributions. However, the experimental results show enhanced mixing-out of the cooling air and, thus, the experimental values of the adiabatic film cooling effectiveness are lower compared to the numerical values.
文摘With the increasing demand for electricity,an efficiency improvement and thereby reduced CO2 emissions of the power plants are expected in order to reach the goals set in the Kyoto protocol.In comparison to conventional systems,the hybrid-systems with the use of synergetic effects offer the possibility to provide a substantial contribution to spare our natural resources and protect our environment.Combined Cycle Power Plants belongs innately hybrid system in the centralized energy market.They can provide large amounts of power and have a quick start-up time.The MGT/FC hybrid system is quite promising in the decentralized energy market.It is widely used in stand-alone applications.Furthermore,the combination of fossil and renewable power plant technologies contains a large synergy potential to increase the efficiency of processes for power plants.New materials,innovative cooling technology,new combustion concepts and optimized production methods are needed to make the potential of these new technologies accessible for a quantum leap in the efficiency.For this it needs considerable research work and good coordinated research projects between the state,industry,research laboratories and universities.
文摘This study is an advanced investigation for the cooling of high temperature turbine vanes and blades. The efficient heat exchanging near the surface of a blade may be achieved by forcing a cooling air flow emitting out of a thin layer of the porous metal which is pasted on the structural high strength metal. The contents include the consideration on the computational model of heat transfer through a layer of porous material, the concrete modeling and the analysis of the model, the numerical survey of key parameters for both the two-layer porous materials and the heat transfer fluid flow passing through the model channels. The results revealed that the constructed system is reasonable. Proposed an evaluation formula for the porous material heat transfer efficiency.
文摘This paper presents preliminary measurements of a 2-stage axial turbine with shrouded rotor cavities. The research facility and measurement techniques are reported. The flow field at both inlet and outlet was measured using 5-hole probes as well as temperature probes. The measurement results indicate that the inlet flow field is periodical in the tangential direction due to the influence of the first-stator leading-edge. The horse-shoe vortexes cause substantial flow blockage and turbulence near the endwall. Unsteady measurements of the rotor radial tip clearance show that one of the second-rotor blades has a little bigger clearance than the others.
文摘In order to get a better knowledge of the heat transfer in compressor cavities of aero-engines,the simplified rotating cavity with two-plane discs,a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements.The numerical results in agreement with the available experiments show large-scale instabilities.The disk local Nusselt numbers show mainly radial rising distributions for the heated disks with radial rising temperature profiles.In the present work,at the Reynolds number of 20 000,the disk local Nusselt numbers are the correlations of the local Grashof number to the power of 1.89-2.6,and the value of the power is increased as the rotational Reynolds number goes up.At the rotational Reynolds number of 800 000,the local Nusselt numbers are the correlations of the local Grashof number to the power of 0.68-2.6,and the value of the power is decreased as Reynolds number goes up.The area-averaged disk Nusselt number is the correlation of the Reynolds number to the power of 0.479 and the rotational Grashof number to the power of 0.12.
文摘The goal of Collaborative Research Centre(SFB) 561 "thermally highly loaded,porous and cooled multi-layer systems for combined cycle power plants" is to expand the current technological and scientific knowledge on power plants in order to achieve total efficiencies of 65% in a combined cycle power plant in the year 2025.Therefore,the aero-thermomechanical,structural-mechanical,materials' scientific and production fundamentals for the development of steam and gas turbine components that are able to withstand highest thermal loads are being worked out within this SFB.This means for the gas turbine that combustion chamber outlet temperatures of 1520℃ at 1.7MPa are to be attained.In order to control these high temperatures,it is not only required to develop new materials' solutions,including thermal barrier coatings,but also to apply improved cooling techniques,as for example effusion cooling.This novel cooling concept is to be realised through open-porous structures.These structures can consist of drilled open-porous multi-layer systems or open-porous metallic foams.The development of graded multi-layer systems is also extremely important,as the grading will enable the use of coolant in dependence of the requirements.The live steam parameters in the high pressure turbine are expected to be increased up to approximately 700℃ with pressure of 30MPa.These elevated steam parameters can be encountered with Ni-base alloys,but this is a costly alternative,associated with many manufacturing difficulties.Therefore,the SFB proposes cooling the highly loaded turbines instead,as this would necessitate the application of far less Ni-base alloys.To protect the thermally highly loaded casing,a sandwich material consisting of two thin face sheets with a core of a woven wire mesh is used to cover the walls of the steam turbine casing.The current state of the research shows that by utilising innovative cooling technologies a total efficiency of 65% can be reached without exceeding the maximum allowable material temperature,thereby prolonging the life-span.
