Experiment on Adiabatic Film Cooling Effectiveness in Front Zone of Effusion Cooling Configuration

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.

Numerical Investigation on Flow and Cooling Characteristics of a Micro-Ribbed Vane Endwall

The secondary flow originated from the inherent pressure gradient inside the vane cascade has a strong impact on the endwall cooling performance as the crossflow sweeps the upstream coolant jet towards the suction side,resulting in intensifying thermal load near the pressure side endwall.Hence a novel ribbed-endwall is introduced to suppress passage crossflow.The effects of the mass flow ratio and the rib layout were examined using numerical simulations by solving the three-dimensional Reynolds-averaged Navier-Stokes(RANS)equations with the shear stress transport(SST)k-ωturbulence model.The results indicate that the ribs effectively prevent the coolant migrating from the pressure side to the suction side,helping the coolant jet to spread along the lateral orientation.Therefore,the endwall adiabatic film cooling effectiveness is substantially improved.The maximum cooling effectiveness is achieved for the case with three-ribs when the height of the rib equals one hole diameter among all cases.The area-averaged adiabatic cooling effectiveness is enhanced by 31.6%relative to the flat endwall when the mass flow ratio of coolant to mainstream equals to 0.52%.More importantly,the ribbed-endwall obtains a relatively lower level of aerodynamic loss owing to the reduced lateral migration inside the vane cascade.

Improvement on shaped-hole film cooling effectiveness by integrating upstream sand-dune-shaped ramps

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.

Numerical investigation on adiabatic film cooling effectiveness and heat transfer coefficient for effusion cooling over a transverse corrugated surface

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.

Experimental investigation of the full coverage film cooling effectiveness of a turbine blade with shaped holes

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.

Numerical study of effusion cooling on an adiabatic flat plate

The present study aims to investigate the effectiveness of effusion film cooling on an adiabatic flat plate.Cylindrical holes of 301 inclination are used for supplying cold air to the hot primary flow.A non-dimensional parameter called the film cooling effectiveness is calculated for studying the influence of the velocity ratio for a continuous array of cooling holes.A new approach by splitting the full coverage of film holes into two zones of cooling rows is presented in this paper.The computational results from the investigation show that there exists strong relationship between velocity ratio and adiabatic film cooling effectiveness.The simulations of two zones indicate that a careful analysis of the distribution of cooling holes can significantly reduce the demand for the supply of cold air.

Mass production of magnetocaloric LaFeMnSiB alloys with hydrogenation

LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）Hxalloys were prepared by hydrogenation.Samples were annealed at 1343Kfor30-90 hto form the NaZn13 phase.La-rich andα-Fe secondary phases were also detected.Saturated hydrogenation at 553 Kand 0.15 MPa of H_2 pressure for 5hwas employed to improve the Curie temperature of the alloys to 279 K.The maximum magnetic entropy change,relative cooling power,and adiabatic temperature change of LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x annealed at 1343 Kfor 90hafter hydrogen absorption are 6.38J/（kg·K）（magnetic changesμ0ΔH =1.65T）,100.1J/kg（μ0ΔH =1.65T）,and 2.2 K（μ0ΔH =1.48T）,respectively.Although the maximum magnetic entropy change of the LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys is lower than those of similar alloys with high purity raw materials,the relative cooling power is nearly the same.The effect of impurities of the raw materials used was also discussed.It is assumed that the impurity of 0.2wt.% Al is responsible for the reduced entropy change of the resulted alloys.The LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys prepared by this method could be a low cost alternative material for room temperature magnetic cooling applications.