The control of cooling power is very important to introduce desired properties. Usually, higher the cooling rate higher the quench hardness and distortion and the optimization of cooling power is the base for good hea...The control of cooling power is very important to introduce desired properties. Usually, higher the cooling rate higher the quench hardness and distortion and the optimization of cooling power is the base for good heat treatment. The change of cooling speed during quenching is one of the effective methods to balance hardness and distortion. Different form the general knowledge of the demerit of vapor blanket stage, oil with long vapor blanket stage is also one of effective methods to reduce distortion. The reduction of distortion with enough quench hardness seems to be possible by optimization of cooling condition by the help of computer simulation. The exhibition of higher core hardness than surface in through hardening steels experienced in the "Inverse quench hardening" was introduced by Prof. Tamura and Shimizu. This mechanism is well explained by Arimoto et al, by analysis of computer simulation. In this paper, plural steps cooling methods are compared, in relation with cooling curve and heat transfer coefficient that is necessary to simulate quench results and the possibility of advanced cooling technology is discussed.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
Numerical predictions of three-dimensional flow and heat transfer are performed for a two-pass square channel with 45° staggered ribs in non-orthogonally mode-rotation using the second moment closure model. At Re...Numerical predictions of three-dimensional flow and heat transfer are performed for a two-pass square channel with 45° staggered ribs in non-orthogonally mode-rotation using the second moment closure model. At Reynolds number of 25,000, the rotation numbers studied were 0,0.24, 0.35 and 1.00. The density ratios were 0.13, 0.23 and 0.50. The results show that at high buoyancy parameter and high rotation number with a low density ratio, the flow in the first passage is governed by the secondary flow induced by the rotation whereas the secondary flow induced by the skewed ribs was almost distorted. As a result the heat transfer rate is enhanced on both co-trailing and co-leading sides compared to low and medium rotation number. In contrast, for the second passage, the rotation slightly reduces the heat transfer rate on co-leading side at high rotation number with a low density ratio and degrades it significantly on both co-trailing and co-leading sides at high buoyancy parameter compared to the stationary, low and medium rotation numbers. The numerical results are in fair agreement with available experimental data in the bend region and the second passage, while in the first passage were overestimated at low and medium rotation numbers.展开更多
文摘The control of cooling power is very important to introduce desired properties. Usually, higher the cooling rate higher the quench hardness and distortion and the optimization of cooling power is the base for good heat treatment. The change of cooling speed during quenching is one of the effective methods to balance hardness and distortion. Different form the general knowledge of the demerit of vapor blanket stage, oil with long vapor blanket stage is also one of effective methods to reduce distortion. The reduction of distortion with enough quench hardness seems to be possible by optimization of cooling condition by the help of computer simulation. The exhibition of higher core hardness than surface in through hardening steels experienced in the "Inverse quench hardening" was introduced by Prof. Tamura and Shimizu. This mechanism is well explained by Arimoto et al, by analysis of computer simulation. In this paper, plural steps cooling methods are compared, in relation with cooling curve and heat transfer coefficient that is necessary to simulate quench results and the possibility of advanced cooling technology is discussed.
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.
文摘Numerical predictions of three-dimensional flow and heat transfer are performed for a two-pass square channel with 45° staggered ribs in non-orthogonally mode-rotation using the second moment closure model. At Reynolds number of 25,000, the rotation numbers studied were 0,0.24, 0.35 and 1.00. The density ratios were 0.13, 0.23 and 0.50. The results show that at high buoyancy parameter and high rotation number with a low density ratio, the flow in the first passage is governed by the secondary flow induced by the rotation whereas the secondary flow induced by the skewed ribs was almost distorted. As a result the heat transfer rate is enhanced on both co-trailing and co-leading sides compared to low and medium rotation number. In contrast, for the second passage, the rotation slightly reduces the heat transfer rate on co-leading side at high rotation number with a low density ratio and degrades it significantly on both co-trailing and co-leading sides at high buoyancy parameter compared to the stationary, low and medium rotation numbers. The numerical results are in fair agreement with available experimental data in the bend region and the second passage, while in the first passage were overestimated at low and medium rotation numbers.
