摘要 :
Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE's E~3 turbi...
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Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE's E~3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15C_x to 0.45C_x, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90° , the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR)=1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR=1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.
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摘要 :
Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE's E~3 turbi...
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Based on the infrared temperature measurement technology, in this paper, the effect of the purge flow from the upstream slot on the film cooling performance of the annular cascade endwall was studied experimentally. GE's E~3 turbine first stage stator blades is selected as the experimental reference blade type in this experiment. In the current experiment, effects of different slot locations, slot ejection angles and slot profiles on the endwall film cooling effectiveness were taken into account. Under the influence of endwall secondary flow, the film cooling is mainly concentrated on the front part of the channel and close to the suction side of the blade, while there is almost no cooling effect close to the pressure side of the blade in the channel. With the increase of the distance between the blade leading edge and the slot, the endwall film cooling performance is reduced. While the distance increasing from 0.15C_x to 0.45C_x, and the peak endwall film cooling effectiveness is reduced by 78%, 68% and 58% respectively when the mass flow ratio (MFR) is 1.0%, 1.5%, and 2.0%. As the slot ejection angle is reduced, the endwall film cooling performance can be effectively improved. When the slot ejection angle increased from 45° to 90° , the peak endwall film cooling effectiveness decreases by 17%, 15%, and 13% respectively at the mass flow ratio (MFR)=1.0%,1.5% and 2.0%. And the convergent slot can effectively improve the endwall cooling film formed by slot jet compared to the reference slot. When the mass flow ratio are MFR=1.0%, 1.5%, and 2.0%, the peak endwall film cooling effectiveness at the convergent slot is increased by 50%, 20%, and 15% comparing to the reference slot.
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摘要 :
The behavior of flow transition in a rectangular microchannel was numerically investigated. In the simulation, three flow models were adopted, namely, a γ-Re_(θt) transition model, a laminar model and a shear stress transport (S...
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The behavior of flow transition in a rectangular microchannel was numerically investigated. In the simulation, three flow models were adopted, namely, a γ-Re_(θt) transition model, a laminar model and a shear stress transport (SST) model. The simulation was conducted using ANSYS CFX, and the results were compared with experimental data, then the effect of length-to-diameter ratio (L/D) on the critical Reynolds number was studied. Results indicate that the laminar model and the γ-Re_(θt) transition model produce similar pressure drops when the mass flow rate is smaller. When the mass flow rate increases, values predicted by the γ-Re_(θt) transition model matches best with the experimental data. The laminar model and the SST model are incapable of predicting transition, while the γ-Re_(θt) transition model forecasts the critical Reynolds number well and the predicted values match well with the experimental data. In the present study, the transition is accurately simulated and the flow mechanism is revealed. The results also show that local turbulent regions appear at the rear of the microchannel before the Reynolds number reaches the critical value and the turbulent regions expand with the increase of the Reynolds number. For microchannels with L/D≥100, the transition from laminar to turbulent regime occurs for a Reynolds number in the range 2000-2500, and the length-to-diameter ratio has no significant effect on the critical Reynolds number.
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摘要 :
The behavior of flow transition in a rectangular microchannel was numerically investigated. In the simulation, three flow models were adopted, namely, a γ-Re_(θt) transition model, a laminar model and a shear stress transport (S...
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The behavior of flow transition in a rectangular microchannel was numerically investigated. In the simulation, three flow models were adopted, namely, a γ-Re_(θt) transition model, a laminar model and a shear stress transport (SST) model. The simulation was conducted using ANSYS CFX, and the results were compared with experimental data, then the effect of length-to-diameter ratio (L/D) on the critical Reynolds number was studied. Results indicate that the laminar model and the γ-Re_(θt) transition model produce similar pressure drops when the mass flow rate is smaller. When the mass flow rate increases, values predicted by the γ-Re_(θt) transition model matches best with the experimental data. The laminar model and the SST model are incapable of predicting transition, while the γ-Re_(θt) transition model forecasts the critical Reynolds number well and the predicted values match well with the experimental data. In the present study, the transition is accurately simulated and the flow mechanism is revealed. The results also show that local turbulent regions appear at the rear of the microchannel before the Reynolds number reaches the critical value and the turbulent regions expand with the increase of the Reynolds number. For microchannels with L/D≥100, the transition from laminar to turbulent regime occurs for a Reynolds number in the range 2000-2500, and the length-to-diameter ratio has no significant effect on the critical Reynolds number.
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Emergency flight path planning process was established for the failure of total loss of thrust of both the commercial transport aircraft and the general aviation to improve the flight safety. The process of the path planning combi...
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Emergency flight path planning process was established for the failure of total loss of thrust of both the commercial transport aircraft and the general aviation to improve the flight safety. The process of the path planning combined the landing site search and the post failure trajectory generation together. The dynamic pressure schedule was substitute for the rigid geometric preset as the restriction to ensure the smooth speed variation.Based on the variation time scales separation, the propagation logic without iteration was established for longitudinal states and commands. The top ranked landing site was selected from the approximate footprint with the radius determined by current flight states, according to the safe condition.Furthermore, a three step lateral trajectory generation algorithm can generate final trajectory and commands by linear interpolation. The trajectory can be rapidly generated for the selected landing site with satisfactory accuracy due to the incorporation of the coupling effects in flight dynamics, and the guidance commands can be tracked by basic guidance control law.
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摘要 :
Emergency flight path planning process was established for the failure of total loss of thrust of both the commercial transport aircraft and the general aviation to improve the flight safety. The process of the path planning combi...
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Emergency flight path planning process was established for the failure of total loss of thrust of both the commercial transport aircraft and the general aviation to improve the flight safety. The process of the path planning combined the landing site search and the post failure trajectory generation together. The dynamic pressure schedule was substitute for the rigid geometric preset as the restriction to ensure the smooth speed variation.Based on the variation time scales separation, the propagation logic without iteration was established for longitudinal states and commands. The top ranked landing site was selected from the approximate footprint with the radius determined by current flight states, according to the safe condition.Furthermore, a three step lateral trajectory generation algorithm can generate final trajectory and commands by linear interpolation. The trajectory can be rapidly generated for the selected landing site with satisfactory accuracy due to the incorporation of the coupling effects in flight dynamics, and the guidance commands can be tracked by basic guidance control law.
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Existing cross-modal retrieval methods are mainly constrained to the bimodal case. When applied to the multi-modal case, we need to train O(K~2) (K: number of modalities) separate models, which is inefficient and unable to exploit...
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Existing cross-modal retrieval methods are mainly constrained to the bimodal case. When applied to the multi-modal case, we need to train O(K~2) (K: number of modalities) separate models, which is inefficient and unable to exploit common information among multiple modalities. Though some studies focused on learning a common space of multiple modalities for retrieval, they assumed data to be i.i.d. and failed to learn the underlying semantic structure which could be important for retrieval. To tackle this issue, we propose an extensive Adversarial Graph Attention Network for Multi-modal Cross-modal Retrieval (AGAT). AGAT synthesizes a self-attention network (SAT), a graph attention network (GAT) and a multi-modal generative adversarial network (MGAN). The SAT generates high-level embeddings for data items from different modalities, with self-attention capturing feature-level correlations in each modality. The GAT then uses attention to aggregate embeddings of matched items from different modalities to build a common embedding space. The MGAN aims to "cluster" matched embeddings of different modalities in the common space by forcing them to be similar to the aggregation. Finally, we train the common space so that it captures the semantic structure by constraining within-class/between-class distances. Experiments on three datasets show the effectiveness of AGAT.
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In gas turbine engines, with the existence of the intense forced convection and significant buoyancy effects, temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly. In ...
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In gas turbine engines, with the existence of the intense forced convection and significant buoyancy effects, temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly. In this paper, numerical simulations were performed to analyze these influences for a free disk, with the laminar and turbulent flow respectively. The influences of temperature distribution on the heat transfer were observed by using incompressible cooling air, and temperature profiles of nth order monomial and polynomial were assumed on the disk. The analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number; for an arbitrary polynomial profile, the local Nusselt number can be deduced from results of monomial profiles. To study the effects of temperature level on heat transfer singly, monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were compared. And both for two flow states, the following conclusions could be drawn: The relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference, and almost independent of the monomial's coefficient C, exponent n and the rotating Reynolds Number. Subsequently, a correction method for heat transfer of the free disk is presented and verified computationally, with which the local Nusselt number, obtained with a uniform and low temperature profile, can be revised by arbitrary distribution and high temperature magnitude.
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摘要 :
In gas turbine engines, with the existence of the intense forced convection and significant buoyancy effects, temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly. In ...
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In gas turbine engines, with the existence of the intense forced convection and significant buoyancy effects, temperature distribution and level on turbine or compressor disks affect the heat transfer characteristics strongly. In this paper, numerical simulations were performed to analyze these influences for a free disk, with the laminar and turbulent flow respectively. The influences of temperature distribution on the heat transfer were observed by using incompressible cooling air, and temperature profiles of nth order monomial and polynomial were assumed on the disk. The analysis revealed that the heat transfer for two flow states on the free disk is determined by the exponent n of the monomial profile when specifying the rotating Reynolds number; for an arbitrary polynomial profile, the local Nusselt number can be deduced from results of monomial profiles. To study the effects of temperature level on heat transfer singly, monomial profiles were used and the local Nusselt number of compressible and incompressible cooling air were compared. And both for two flow states, the following conclusions could be drawn: The relative difference of local Nusselt number is mainly controlled by nondimensional local temperature difference, and almost independent of the monomial's coefficient C, exponent n and the rotating Reynolds Number. Subsequently, a correction method for heat transfer of the free disk is presented and verified computationally, with which the local Nusselt number, obtained with a uniform and low temperature profile, can be revised by arbitrary distribution and high temperature magnitude.
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To address the issue of large network computing parameters for spatial-temporal features of actions in multi-view video sequences, this paper proposes a Spatial-Temporal Hypergraph Neural Network based on Attention Mechanism (STHG...
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To address the issue of large network computing parameters for spatial-temporal features of actions in multi-view video sequences, this paper proposes a Spatial-Temporal Hypergraph Neural Network based on Attention Mechanism (STHGNN-AM). This method consists of a Temporal Attention Mechanism based on Trainable Threshold (TAM-TT) and a Multi-scale Spatial-Temporal Residual Module (MS-STRM), achieving multi-view data action recognition. Specifically, TAM-TT is constructed by using a learnable threshold to extract key frames of actions from different view video frames input to the module. MS-STRM is employed to further improve the model performance, and high-order semantic features of actions are learned in a hypergraph neural network. The MS-STRM extracts features using a multi-scale approach, modeling long-term and short-term semantic information to capture the temporal information changes between different frames. Comparative experiments on the NTU RGB+D and imitating traffic police gestures datasets evince the superior performance and heightened recognition accuracy exhibited by the proposed methodology, effectively enhancing the cognitive ability of machine-human body language interaction.
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