Film cooling is an indispensable scheme in the design of highly-efficient cooling configurations to satisfy the thermal protection requirement of turbine hot section components.During the last few decades,vast efforts...Film cooling is an indispensable scheme in the design of highly-efficient cooling configurations to satisfy the thermal protection requirement of turbine hot section components.During the last few decades,vast efforts have been paid on the discrete-hole film cooling enhancement.In this paper,some of the recent literatures related to the passive strategies(such as shaped film cooling holes,upstream ramps,shallow trenches,mesh-fed slots)and the active strategies(such as the use of pulsation modulating device or plasma actuator)for film cooling enhancement are surveyed,with the aim at presenting an updated overview about the state of the art in advanced film cooling.In addition,some challenging issues are also outlined to motivate further investigations in such a broad topic.展开更多
This article presents the data about heat transfer coefficient ratios, film cooling effectiveness and heat loads for the injection through cylindrical holes, 3-in-1 holes and fanned holes in order to characterize the ...This article presents the data about heat transfer coefficient ratios, film cooling effectiveness and heat loads for the injection through cylindrical holes, 3-in-1 holes and fanned holes in order to characterize the film cooling performance downstream of a row of holes with 45° inclination and 3 hole spacing apart. The trip wire is placed upstream at a distance of 10 times diameter of the cooling hole from the hole center to keep mainstream fully turbulent. Both inlet and outlet of 3-in-1 holes have a 15° lateral expansion. The outlet of fanned holes has a lateral expansion. CO2 is applied for secondary injection to obtain a density ratio of 1.5. Momentum flux ratio varies from 1 to 4. The results indicate that the increased momentum flux ratio significantly increases heat transfer coefficient and slightly improve film cooling effectiveness for the injection through cylindrical holes. A weak dependence of heat transfer coefficient and film cooling effectiveness, respectively, on momentum flux ratio has been identified for the injection through 3-in-1 holes. The in- crease of the momentum flux ratio decreases heat transfer coefficient and significantly increases film cooling effectiveness for the injection through fanned holes. In terms of the film cooling performance, the fanned holes are the best while the cylindrical holes are the worst among the three hole shapes under study.展开更多
A numerical investigation and experimental validation is performed to address deeper insights into the combined effect of shaped holes and Sand-Dune-shaped upstream Ramp(SDR)on enhancing the film cooling effectiveness...A numerical investigation and experimental validation is performed to address deeper insights into the combined effect of shaped holes and Sand-Dune-shaped upstream Ramp(SDR)on enhancing the film cooling effectiveness,under a wide blowing ratio range(M=0.25–1.5).Three kinds of holes(Cylindrical Hole(CH),Fan-Shaped Hole(FSH),and Crater-Shaped Hole(CSH))are taken into consideration.The SDR shows an inherent affecting mechanism on the mutual interaction of jet-in-crossflow.It aggravates the lateral spreading of cooling jet and thus improves the film cooling uniformity significantly,regardless of film-hole shape and blowing ratio.When the blowing ratio is beyond 1.0,the combined effect of shaped holes and SDR on improving film cooling effectiveness behaves more significantly.It is suggested that FSH-SDR is a most favorable film cooling scheme.For FSH-SDR case,the spatially-averaged film cooling effectiveness is increased monotonously with the increase of blowing ratio,among the present bowing ratio range.展开更多
The film cooling effectiveness of two turbine blades at different turbulence intensities(0.62%and 16.00%)and mass flux ratios(2.91%,5.82%,8.73%and 11.63%)is studied by using the Pressure-Sensitive Paint(PSP)measuremen...The film cooling effectiveness of two turbine blades at different turbulence intensities(0.62%and 16.00%)and mass flux ratios(2.91%,5.82%,8.73%and 11.63%)is studied by using the Pressure-Sensitive Paint(PSP)measurement technique.There are a baseline and an improved turbine blade in current work,and their film cooling hole position distribution is the same.But the hole shape on suction surface and pressure surface is changed from cylindrical hole(baseline)to laid-back fan-shaped hole(improved blade).Both blades have 5 rows of cylindrical holes at the leading edge and 4 rows of cooling-holes on the suction surface and the pressure surface.The experimental results show that the film cooling effectiveness of the improved blade is much better than the baseline.The increase in turbulence intensity will reduce the cooling effectiveness on the surface of turbine blade,but the effect of turbulence intensity becomes weaker with an increase in the mass flux ratio.Compared with the multiple rows of cylindrical holes,the cooling effectiveness of shaped holes is more influenced by the turbulence intensity at low mass flux ratio.展开更多
Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes,the mass flow ratio,and the hole spacing on the film cooling effectiveness.The mainstream wa...Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes,the mass flow ratio,and the hole spacing on the film cooling effectiveness.The mainstream was obtained by the hydrogen-oxygen combustion,entering the experimental section at a Mach number of 2.0.The nitrogen with ambient temperature was injected into the experimental section at a sonic speed.The measured mainstream recovery temperature was approximately 910K.The mass flow ratio was regulated by varying the nitrogen injection pressure.The experimental results show that for the investigated cooling surface,the cooling effectiveness increases with the increase in the number of the injection holes with other parameters held constant.For a fixed cooling configuration,the cooling effectiveness increases with the increase in the mass flow ratio.Different from the subsonic film cooling,the optimal mass flow ratio is not observed.When the hole spacing is less than 4,no obvious difference is observed on the cooling effectiveness and lateral uniformity.With the mass flow ratio increasing further,this difference becomes much smaller.The shock wave also has an effect on the cooling effectiveness.Downstream the incident point of the shock wave,the cooling effectiveness is lower than that in the case without the shock wave.展开更多
Transcritical film cooling was investigated by numerical study in a methane cooled methane/oxygen rocket engine.The respective time-averaged Navier-Stokes equations have been solved for the compressible steady three-d...Transcritical film cooling was investigated by numerical study in a methane cooled methane/oxygen rocket engine.The respective time-averaged Navier-Stokes equations have been solved for the compressible steady three-dimensional(3-D) flow.The flow field computations were performed using the semi-implicit method for pressure linked equation(SIMPLE) algorithm on several blocks of nonuniform collocated grid.The calculation was conducted over a pressure range of 202 650.0 Pa to 1.2×107 Pa and a temperature range of 120.0 K to 3 568.0 K.Twenty-nine different cases were simulated to calculate the impact of different factors.The results show that mass flow rate,length,diameter,number and diffused or convergence of film jet channel,injection angle and jet array arrangements have great impact on transcritical film cooling effectiveness.Furthermore,shape of the jet holes and jet and crossflow turbulence also affect the wall temperature distribution.Two rows of film arranged in different axial angles and staggered arrangement were proposed as new liquid film arrangement.Different radial angles have impact on the film cooling effectiveness in two row-jets cooled cases.The case of in-line and staggered arrangement are almost the same in the region before the second row of jets,but a staggered arrangement has a higher film cooling effectiveness from the second row of jets.展开更多
Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detac...Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detached Eddy Simulation (SDES), Stress-Blended Eddy Simulation (SBES), and Zonal Large Eddy Simulation (ZLES), along with a no-model laminar simulation. Each is used to simulate an adiabatic flat plate film cooling experiment of a shaped hole at low Reynolds number. Adiabatic effectiveness is calculated for Blowing Ratio (BR) = 1.5 and Density Ratio (DR) = 1.5. The ZLES method and laminar simulation most accurately match experimental lateral-average adiabatic effectiveness along the streamwise direction from the trailing edge of the hole to 35 hole diameters downstream of the hole (X/D = 0 to X/D = 35), with RMS deviations of 5.1% and 4.2%, and maximum deviations of 8% and 11%, respectively. The accuracy of these models is attributed to the resolution of turbulent structures in not only the mixing region but in the upstream boundary layer as well, where the other methods utilize RANS and do not switch to LES.展开更多
Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immed...Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immediate region of injection but also downstream region. This paper numerically investigated the film cooling effectiveness on two types of hole geometries which are cut-shaped hole and antivortex hole. The 3D computational geometries are modeled with a single 30 deg angled hole on a flat surface. The different blowing ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5 and k-Epsilon turbulence model are used in this study. A two dimensional distribution of film cooling effectiveness in the downstream region of the cooling hole is performed. A comparison of spanwise averaged effectiveness is also performed in the field starts from center point of hole to X/D=-30.展开更多
An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. S...An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations（such as leading-inlet, leading-middle,leading-exit, trailing-inlet, trailing-middle and trailing-exit） and four blocking ratios（ranging from 0.1 to 0.4） are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness.展开更多
Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wa...Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wave impinging in three different regions and analyzed the effect of impinging region.The shock wave generators were located at x/s=5,25,45 with 4°,7°and 10°shock wave incidence.The mainstream Mach number was 3.2 and the coolant Mach number was 1.2 or 1.5.The numerical results illustrated that the shock wave impinged in the further upstream region led to a larger high-pressure region and a larger vortex in the boundary layer.Moreover,placing the shock wave generator upstream resulted in the lower mass fraction of coolant in the downstream region.The velocity in the upstream part of the cooling layer was lower than the midstream and downstream part,which resulted in the less ability to resist the shock wave impingement.Therefore,the upstream impingement deteriorated the cooling performance to a greater extent.The study also manifested that the stronger shock wave had a larger effect on supersonic film cooling.Increasing the coolant inlet Mach number can increase the blowing ratio and reduce the mixing,which was of benefit to improve cooling effect.展开更多
The mechanical properties of nickel-based single crystal thin-walled plate with close-packed film cooling holes were studied based on the equivalent solid material concept. The effective plastic parameters inversion m...The mechanical properties of nickel-based single crystal thin-walled plate with close-packed film cooling holes were studied based on the equivalent solid material concept. The effective plastic parameters inversion method based on crystallographic theory were proposed. A simplification method for close-packed film cooling hole plates with square and triangular penetration patterns was presented. A large number of finite element analysis results covering different ligament efficiencies and penetration patterns were provided to verify the feasibility of the plastic equivalent principle and simplification method. The results show that the stress–strain curve and resolved shear stresses of simplification models are in consistence with the plate models with close-packed film cooling holes. The equivalent errors of yield strength are all within the error band and the values of equivalent errors are all less than 10%. In addition, the equivalent errors of the positions where maximum resolved shear stress occurs are all less than 15°, indicating the accuracy of plastic equivalent model and simplification method.展开更多
Three-dimensional numerical computations are conducted to investigate the effects of the blowing ratio and corrugation geometry on the adiabatic film cooling effectiveness as well as the heat transfer coefficient over...Three-dimensional numerical computations are conducted to investigate the effects of the blowing ratio and corrugation geometry on the adiabatic film cooling effectiveness as well as the heat transfer coefficient over a transverse corrugated surface.It is noticeable that the adiabatic wall temperature on the wavy valley of the transverse corrugated surface is relatively lower than that on the wavy peak.Surface corrugation has a relatively obvious influence on the laterallyaveraged adiabatic film cooling effectiveness in the region where the effusion film layer is developed,but has little influence in the front region.Compared to a flat surface,the transverse corrugated surface produces a smaller adiabatic film cooling effectiveness and a higher heat transfer coefficient ratio.The effusion cooling difference between the flat and corrugated surfaces behaves more obviously under a small aspect ratio of the wavy corrugation.展开更多
The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle wi...The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle with Mach numbers of 7.3 and 8.1, and the total temperature is about 900 K. The injection Mach number is 3.2, and total temperature is 300 K. A constant voltage circuit is developed to supply the temperature detectors instead of the normally used constant current circuit. The schlieren photographs are presented additionally to visualize the flow and help analyze the pressure relationship between the cooling flow and the main flow. The dependence of the film-cooling effectiveness on flow parameters, i.e. the blow ratio, the convective Mach number, and the attack angle, is determined. A semi-empirical formula is tested by the present data, and is improved for a better correlation.展开更多
The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cool...The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling.The results indicate that without shock-wave impingement and with helium as the coolant,segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection,especially at larger coolant Mach numbers.However,with nitrogen as the coolant,the cooling effect of the segmented-injection system is very close to that of the single-injection system.Mixing at the impinging region is enhanced significantly when there is an incident shock wave.When the shock wave impinges between the two coolant inlets,segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock wave.The advantage of segmented injection is reduced when the impinging region is behind the second coolant inlet.The further downstream the impinging region,the smaller the associated advantage.展开更多
Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientati...Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.展开更多
In this article, numerical investigation of the effects of different plasma actuation strengths on the film cooling flow characteristics has been conducted using large eddy simulation （LES）. For this numerical resea...In this article, numerical investigation of the effects of different plasma actuation strengths on the film cooling flow characteristics has been conducted using large eddy simulation （LES）. For this numerical research, the plasma actuator is placed downstream of the trailing edge of the film cooling hole and a phenomenological model is employed to provide the electric field generated by it, resulting in the body forces. Our results show that as the plasma actuation strength grows larger, under the downward effect of the plasma actuation, the jet trajectory near the cooling hole stays closer to the wall and the recirculation region observably reduces in size. Meanwhile, the momentum injection effect of the plasma actuation also actively alters the distributions of the velocity components downstream of the cooling hole. Consequently, the influence of the plasma actuation strength on the Reynolds stress downstream of the cooling hole is remarkable. Furthermore, the plasma actuation weakens the strength of the kidney shaped vortex and prevents the jet from lifting off the wall. Therefore, with the increase of the strength of the plasma actuation, the coolant core stays closer to the wall and tends to split into two distinct regions. So the centerline film cooling efficiency is enhanced, and it is increased by 55% at most when the plasma actuation strength is 10.展开更多
Hot wire measurements and flow visualization are presented for studying the turbulent flow field over a flat gas turbine film cooling blade with lateral expanded holes. Three mass flux ratios of jet to free stream, M ...Hot wire measurements and flow visualization are presented for studying the turbulent flow field over a flat gas turbine film cooling blade with lateral expanded holes. Three mass flux ratios of jet to free stream, M = 0.5, 0.89, 1.5, are tested. The streamwise velocity, the turbulent intensities and the Reynolds shear stress are measured. The effect of the lateral expanded holes on the improvement of the turbulent flow field for film cooling of gas turbines can be analyzed from the measured spatial di...展开更多
In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were con...In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport （SST） k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.展开更多
The gas turbine blades with diffusion film cooling holes are newlydeveloped blade struc- tures in the hydrogen combustion gas turbine,which has an extremely high inlet gas temperature (1700 deg. C). TheFluid Machinery...The gas turbine blades with diffusion film cooling holes are newlydeveloped blade struc- tures in the hydrogen combustion gas turbine,which has an extremely high inlet gas temperature (1700 deg. C). TheFluid Machinery Laboratory of Nagoya Institute o Technology conductedfirstly a new research o the turbulent flow field over the gasturbine blade with diffusion film cooling holes in Japan. Normal-typeand X-ray hot wires were applied in the measurement of the flowfield.展开更多
In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scatt...In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scattering （NPLS）, which has a high spatiotemporal resolution. Three experimental cases with different injection mass flux rates were carried out. Many typical flow structures were clearly shown, such as shock waves, expansion fans, shear layers, mixing layers, and turbulent boundary layers. The analysis of two NPLS images with an interval of 5 us revealed the temporal evolution characteristics of flow structures. With matched pressures, the laminar length of the mixing layer was longer than that in the case with a larger mass flux rate, but the full covered region was shorter. Structures like K-H （Kelvin-Helmholtz） vortices were clearly seen in both flows. Without injection, the flow was similar to the supersonic flow over a backward- facing step, and the structures were relatively simpler, and there was a longer laminar region. Large scale structures such as hairpin vortices were visualized. In addition, the results were compared in part with the schlieren images captured by others under similar conditions.展开更多
基金financial support for this project from the National Natural Science Foundation of China(Nos.U1508212 and 51706097)National Science and Technology Major Project,China(No.2017-III-00110037)。
文摘Film cooling is an indispensable scheme in the design of highly-efficient cooling configurations to satisfy the thermal protection requirement of turbine hot section components.During the last few decades,vast efforts have been paid on the discrete-hole film cooling enhancement.In this paper,some of the recent literatures related to the passive strategies(such as shaped film cooling holes,upstream ramps,shallow trenches,mesh-fed slots)and the active strategies(such as the use of pulsation modulating device or plasma actuator)for film cooling enhancement are surveyed,with the aim at presenting an updated overview about the state of the art in advanced film cooling.In addition,some challenging issues are also outlined to motivate further investigations in such a broad topic.
文摘This article presents the data about heat transfer coefficient ratios, film cooling effectiveness and heat loads for the injection through cylindrical holes, 3-in-1 holes and fanned holes in order to characterize the film cooling performance downstream of a row of holes with 45° inclination and 3 hole spacing apart. The trip wire is placed upstream at a distance of 10 times diameter of the cooling hole from the hole center to keep mainstream fully turbulent. Both inlet and outlet of 3-in-1 holes have a 15° lateral expansion. The outlet of fanned holes has a lateral expansion. CO2 is applied for secondary injection to obtain a density ratio of 1.5. Momentum flux ratio varies from 1 to 4. The results indicate that the increased momentum flux ratio significantly increases heat transfer coefficient and slightly improve film cooling effectiveness for the injection through cylindrical holes. A weak dependence of heat transfer coefficient and film cooling effectiveness, respectively, on momentum flux ratio has been identified for the injection through 3-in-1 holes. The in- crease of the momentum flux ratio decreases heat transfer coefficient and significantly increases film cooling effectiveness for the injection through fanned holes. In terms of the film cooling performance, the fanned holes are the best while the cylindrical holes are the worst among the three hole shapes under study.
基金financial support for this project from the National Natural Science Foundation of China(No.U1508212)National Science and Technology Major Projects(Nos.2017-Ⅲ-0011-0025 and 2017-Ⅲ0011-0037)。
文摘A numerical investigation and experimental validation is performed to address deeper insights into the combined effect of shaped holes and Sand-Dune-shaped upstream Ramp(SDR)on enhancing the film cooling effectiveness,under a wide blowing ratio range(M=0.25–1.5).Three kinds of holes(Cylindrical Hole(CH),Fan-Shaped Hole(FSH),and Crater-Shaped Hole(CSH))are taken into consideration.The SDR shows an inherent affecting mechanism on the mutual interaction of jet-in-crossflow.It aggravates the lateral spreading of cooling jet and thus improves the film cooling uniformity significantly,regardless of film-hole shape and blowing ratio.When the blowing ratio is beyond 1.0,the combined effect of shaped holes and SDR on improving film cooling effectiveness behaves more significantly.It is suggested that FSH-SDR is a most favorable film cooling scheme.For FSH-SDR case,the spatially-averaged film cooling effectiveness is increased monotonously with the increase of blowing ratio,among the present bowing ratio range.
基金supported by the National Natural Science Foundation of China(No.51936008)the Shaanxi Science Foundation for Distinguished Young Scholars(No.2021JC-11)+1 种基金the National Science and Technology Major Project(No.2017-III-0003-0027)Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(CX2021074)。
文摘The film cooling effectiveness of two turbine blades at different turbulence intensities(0.62%and 16.00%)and mass flux ratios(2.91%,5.82%,8.73%and 11.63%)is studied by using the Pressure-Sensitive Paint(PSP)measurement technique.There are a baseline and an improved turbine blade in current work,and their film cooling hole position distribution is the same.But the hole shape on suction surface and pressure surface is changed from cylindrical hole(baseline)to laid-back fan-shaped hole(improved blade).Both blades have 5 rows of cylindrical holes at the leading edge and 4 rows of cooling-holes on the suction surface and the pressure surface.The experimental results show that the film cooling effectiveness of the improved blade is much better than the baseline.The increase in turbulence intensity will reduce the cooling effectiveness on the surface of turbine blade,but the effect of turbulence intensity becomes weaker with an increase in the mass flux ratio.Compared with the multiple rows of cylindrical holes,the cooling effectiveness of shaped holes is more influenced by the turbulence intensity at low mass flux ratio.
文摘Film cooling experiments with sonic injection were conducted to investigate the effects of the number of the injection holes,the mass flow ratio,and the hole spacing on the film cooling effectiveness.The mainstream was obtained by the hydrogen-oxygen combustion,entering the experimental section at a Mach number of 2.0.The nitrogen with ambient temperature was injected into the experimental section at a sonic speed.The measured mainstream recovery temperature was approximately 910K.The mass flow ratio was regulated by varying the nitrogen injection pressure.The experimental results show that for the investigated cooling surface,the cooling effectiveness increases with the increase in the number of the injection holes with other parameters held constant.For a fixed cooling configuration,the cooling effectiveness increases with the increase in the mass flow ratio.Different from the subsonic film cooling,the optimal mass flow ratio is not observed.When the hole spacing is less than 4,no obvious difference is observed on the cooling effectiveness and lateral uniformity.With the mass flow ratio increasing further,this difference becomes much smaller.The shock wave also has an effect on the cooling effectiveness.Downstream the incident point of the shock wave,the cooling effectiveness is lower than that in the case without the shock wave.
文摘Transcritical film cooling was investigated by numerical study in a methane cooled methane/oxygen rocket engine.The respective time-averaged Navier-Stokes equations have been solved for the compressible steady three-dimensional(3-D) flow.The flow field computations were performed using the semi-implicit method for pressure linked equation(SIMPLE) algorithm on several blocks of nonuniform collocated grid.The calculation was conducted over a pressure range of 202 650.0 Pa to 1.2×107 Pa and a temperature range of 120.0 K to 3 568.0 K.Twenty-nine different cases were simulated to calculate the impact of different factors.The results show that mass flow rate,length,diameter,number and diffused or convergence of film jet channel,injection angle and jet array arrangements have great impact on transcritical film cooling effectiveness.Furthermore,shape of the jet holes and jet and crossflow turbulence also affect the wall temperature distribution.Two rows of film arranged in different axial angles and staggered arrangement were proposed as new liquid film arrangement.Different radial angles have impact on the film cooling effectiveness in two row-jets cooled cases.The case of in-line and staggered arrangement are almost the same in the region before the second row of jets,but a staggered arrangement has a higher film cooling effectiveness from the second row of jets.
文摘Hybrid RANS-LES methods offer a means of reducing computational cost and setup time to simulate transitional flows. Several methods are evaluated in ANSYS CFX, including Scale-Adaptive Simulation (SAS), Shielded Detached Eddy Simulation (SDES), Stress-Blended Eddy Simulation (SBES), and Zonal Large Eddy Simulation (ZLES), along with a no-model laminar simulation. Each is used to simulate an adiabatic flat plate film cooling experiment of a shaped hole at low Reynolds number. Adiabatic effectiveness is calculated for Blowing Ratio (BR) = 1.5 and Density Ratio (DR) = 1.5. The ZLES method and laminar simulation most accurately match experimental lateral-average adiabatic effectiveness along the streamwise direction from the trailing edge of the hole to 35 hole diameters downstream of the hole (X/D = 0 to X/D = 35), with RMS deviations of 5.1% and 4.2%, and maximum deviations of 8% and 11%, respectively. The accuracy of these models is attributed to the resolution of turbulent structures in not only the mixing region but in the upstream boundary layer as well, where the other methods utilize RANS and do not switch to LES.
文摘Film cooling is introduction of a secondary fluid （coolant or injected fluid） at one or more discrete locations along a surface exposed to a high temperature environment to protect that surface not only in the immediate region of injection but also downstream region. This paper numerically investigated the film cooling effectiveness on two types of hole geometries which are cut-shaped hole and antivortex hole. The 3D computational geometries are modeled with a single 30 deg angled hole on a flat surface. The different blowing ratios of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5 and k-Epsilon turbulence model are used in this study. A two dimensional distribution of film cooling effectiveness in the downstream region of the cooling hole is performed. A comparison of spanwise averaged effectiveness is also performed in the field starts from center point of hole to X/D=-30.
基金the financial support for this project from the National Natural Science Foundation of China (Nos.51276090 and U1508212)
文摘An experimental study is made to investigate the film cooling performance of imperfect holes due to in-hole blockage over a flat plate. A specifically pyramid-shaped element is used to simulate the in-hole blockage. Six in-hole blockage orientations（such as leading-inlet, leading-middle,leading-exit, trailing-inlet, trailing-middle and trailing-exit） and four blocking ratios（ranging from 0.1 to 0.4） are taken into considerations. Based on the experimental results, the influences of in-hole blockage on the film cooling effectiveness and discharge coefficient under typical blowing ratios are analyzed. It is confirmed that the in-hole blockage results in a reduction of discharge coefficient related to the perfect film cooling holes, especially for the leading-exit and trailing-inlet orientations with a big blocking ratio. However, in the view of film cooling effectiveness, the in-hole blockage shows complicated affecting roles. In general, except for the leading-exit orientation, the in-hole blockages produce detrimental influence on the film cooling effectiveness.
基金supported by the the National Science and Technology Major Project of China(No.2017-III-0003-0027)the Science Fund for Creative Research Groups of the NSFC(No.51621062)Tsinghua University-Zhang Jiagang Joint Institute for Hydrogen Energy and Lithium-Ion Battery Technology。
文摘Shock waves can significantly affect the film cooling for supersonic flow and shock waves may have different influence when impinging in different regions.The present study numerically compared the results of shock wave impinging in three different regions and analyzed the effect of impinging region.The shock wave generators were located at x/s=5,25,45 with 4°,7°and 10°shock wave incidence.The mainstream Mach number was 3.2 and the coolant Mach number was 1.2 or 1.5.The numerical results illustrated that the shock wave impinged in the further upstream region led to a larger high-pressure region and a larger vortex in the boundary layer.Moreover,placing the shock wave generator upstream resulted in the lower mass fraction of coolant in the downstream region.The velocity in the upstream part of the cooling layer was lower than the midstream and downstream part,which resulted in the less ability to resist the shock wave impingement.Therefore,the upstream impingement deteriorated the cooling performance to a greater extent.The study also manifested that the stronger shock wave had a larger effect on supersonic film cooling.Increasing the coolant inlet Mach number can increase the blowing ratio and reduce the mixing,which was of benefit to improve cooling effect.
基金support provided by the National Natural Science Foundation of China(Nos.51875461 and 51875462)the Fundamental Research Funds for the Central Universities(No.3102017gx06002)
文摘The mechanical properties of nickel-based single crystal thin-walled plate with close-packed film cooling holes were studied based on the equivalent solid material concept. The effective plastic parameters inversion method based on crystallographic theory were proposed. A simplification method for close-packed film cooling hole plates with square and triangular penetration patterns was presented. A large number of finite element analysis results covering different ligament efficiencies and penetration patterns were provided to verify the feasibility of the plastic equivalent principle and simplification method. The results show that the stress–strain curve and resolved shear stresses of simplification models are in consistence with the plate models with close-packed film cooling holes. The equivalent errors of yield strength are all within the error band and the values of equivalent errors are all less than 10%. In addition, the equivalent errors of the positions where maximum resolved shear stress occurs are all less than 15°, indicating the accuracy of plastic equivalent model and simplification method.
文摘Three-dimensional numerical computations are conducted to investigate the effects of the blowing ratio and corrugation geometry on the adiabatic film cooling effectiveness as well as the heat transfer coefficient over a transverse corrugated surface.It is noticeable that the adiabatic wall temperature on the wavy valley of the transverse corrugated surface is relatively lower than that on the wavy peak.Surface corrugation has a relatively obvious influence on the laterallyaveraged adiabatic film cooling effectiveness in the region where the effusion film layer is developed,but has little influence in the front region.Compared to a flat surface,the transverse corrugated surface produces a smaller adiabatic film cooling effectiveness and a higher heat transfer coefficient ratio.The effusion cooling difference between the flat and corrugated surfaces behaves more obviously under a small aspect ratio of the wavy corrugation.
基金Project supported by the National Natural Science Foundation of China(Grant No.11172326)the Scientific Research Program of National University of Defense Technology,China(Grant No.0100010112001)
文摘The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle with Mach numbers of 7.3 and 8.1, and the total temperature is about 900 K. The injection Mach number is 3.2, and total temperature is 300 K. A constant voltage circuit is developed to supply the temperature detectors instead of the normally used constant current circuit. The schlieren photographs are presented additionally to visualize the flow and help analyze the pressure relationship between the cooling flow and the main flow. The dependence of the film-cooling effectiveness on flow parameters, i.e. the blow ratio, the convective Mach number, and the attack angle, is determined. A semi-empirical formula is tested by the present data, and is improved for a better correlation.
基金co-supported by the National Key R&D Program of China (No. 2018YFB1900500)the National S&T Major Project of China (No. J2019-Ⅲ-0019-0063)
文摘The present study proposes a segmented cooling-stream injection structure based on a certain coolant mass flow rate,and numerically investigates the effect of segmented cooling-stream injection on supersonic film cooling.The results indicate that without shock-wave impingement and with helium as the coolant,segmented cooling-stream injection can reduce the mixing between the mainstream and the cooling stream to produce better cooling performance than single injection,especially at larger coolant Mach numbers.However,with nitrogen as the coolant,the cooling effect of the segmented-injection system is very close to that of the single-injection system.Mixing at the impinging region is enhanced significantly when there is an incident shock wave.When the shock wave impinges between the two coolant inlets,segmented cooling-stream injection improves film cooling effectiveness in the midstream and downstream regions more than single injection because only part of the cooling stream undergoes the enhanced mixing effect of the shock wave.The advantage of segmented injection is reduced when the impinging region is behind the second coolant inlet.The further downstream the impinging region,the smaller the associated advantage.
基金Supported by the National Natural Science Foundation of China(51276090)
文摘Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.
文摘In this article, numerical investigation of the effects of different plasma actuation strengths on the film cooling flow characteristics has been conducted using large eddy simulation （LES）. For this numerical research, the plasma actuator is placed downstream of the trailing edge of the film cooling hole and a phenomenological model is employed to provide the electric field generated by it, resulting in the body forces. Our results show that as the plasma actuation strength grows larger, under the downward effect of the plasma actuation, the jet trajectory near the cooling hole stays closer to the wall and the recirculation region observably reduces in size. Meanwhile, the momentum injection effect of the plasma actuation also actively alters the distributions of the velocity components downstream of the cooling hole. Consequently, the influence of the plasma actuation strength on the Reynolds stress downstream of the cooling hole is remarkable. Furthermore, the plasma actuation weakens the strength of the kidney shaped vortex and prevents the jet from lifting off the wall. Therefore, with the increase of the strength of the plasma actuation, the coolant core stays closer to the wall and tends to split into two distinct regions. So the centerline film cooling efficiency is enhanced, and it is increased by 55% at most when the plasma actuation strength is 10.
文摘Hot wire measurements and flow visualization are presented for studying the turbulent flow field over a flat gas turbine film cooling blade with lateral expanded holes. Three mass flux ratios of jet to free stream, M = 0.5, 0.89, 1.5, are tested. The streamwise velocity, the turbulent intensities and the Reynolds shear stress are measured. The effect of the lateral expanded holes on the improvement of the turbulent flow field for film cooling of gas turbines can be analyzed from the measured spatial di...
文摘In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport （SST） k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.
文摘The gas turbine blades with diffusion film cooling holes are newlydeveloped blade struc- tures in the hydrogen combustion gas turbine,which has an extremely high inlet gas temperature (1700 deg. C). TheFluid Machinery Laboratory of Nagoya Institute o Technology conductedfirstly a new research o the turbulent flow field over the gasturbine blade with diffusion film cooling holes in Japan. Normal-typeand X-ray hot wires were applied in the measurement of the flowfield.
基金Project supported by the National Basic Research Program of China (Grant No. 2009 CB724100)the National Natural Science Foundation of China (Grant No. 11172326)
文摘In a Mach 3.8 wind tunnel, both instantaneous and time-averaged flow structures of different scales around a blunt double-cone with or without supersonic film cooling were visualized via nano-tracer planar laser scattering （NPLS）, which has a high spatiotemporal resolution. Three experimental cases with different injection mass flux rates were carried out. Many typical flow structures were clearly shown, such as shock waves, expansion fans, shear layers, mixing layers, and turbulent boundary layers. The analysis of two NPLS images with an interval of 5 us revealed the temporal evolution characteristics of flow structures. With matched pressures, the laminar length of the mixing layer was longer than that in the case with a larger mass flux rate, but the full covered region was shorter. Structures like K-H （Kelvin-Helmholtz） vortices were clearly seen in both flows. Without injection, the flow was similar to the supersonic flow over a backward- facing step, and the structures were relatively simpler, and there was a longer laminar region. Large scale structures such as hairpin vortices were visualized. In addition, the results were compared in part with the schlieren images captured by others under similar conditions.
