Reconstruction of the flow structure in a matrix channel based on two-component LDA data

The work is aimed at creating a technique for reconstructing the three-dimensional structure of turbulent flows using data of a two-component laser-Doppler anemometer at the example of a flow in flat coplanar channels. Data of paired measurements by a two-component LDA at two different angles relative to the measurement point are used to obtain information about the three-dimensional structure of the flow. Further, all three components of the velocity vector were calculated using transformations. The developed method is used to measure the velocity field in a coplanar channel.

Experimental Study of a Rotary Heat Exchanger with a Metal Mesh Matrix

This paper describes the experimental study of a metal mesh matrix of a rotary heat exchanger model including calculation of its regeneration ratio. Temperature oscillograms showing the temperature in tne matrix channel are shown Also the pressure loss value is found for channels of the matrix. The pressure loss value for the case of having a matrix formed by flat metal plates was also calculated in order to compare the calculated values with the ones obtained experimentally for the mesh matrix.

Experimental study of the three-dimensional flow structure in matrix channels

The article presents an experimental study of the turbulent flow in matrix channels. Using the modern optical contactless laser Doppler anemometer (LDA) method, an idea of the turbulent three-dimensional flow inside the cells of matrix channels is developed. The results of the study of the matrix channel show that the so-called vortex matrix effect is not formed. The most important factor that causes a high degree of heat transfer from the walls is the intense spiral motion between the matrix cells. The measurements also show that the effects associated with the lateral boundaries of the channel play a significant role. Based on the assumption of the decisive role of the spiral flow between the cells of the matrix channel, a formula for the integral pressure loss is proposed.

Microstructure Evolution and Stress Rupture Properties of DD6 Single Crystal Superalloy after Overheating

The second generation single crystal superalloy DD6 after standard heat treatment was respectively overheated at 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1320°C for 1h and air cooled. The effect of overheating on the microstructure and stress rupture properties at 980°C/250MPa of the alloy was investigated. The results showed that the size of γ′ phase was slightly increased overheating at 1100°C, 1150°C and 1200°C. The size of γ′ phase had a big increase and its size distribution was very uneven after overheating at 1250°C. The small part of γ′ phase has serrated γ′/γ phase surface as a result of un-completely solution and the irregular small γ′ phase was in the majority when overheated at 1300°C. While all the irregular small γ′ phase precipitated again after completely solution when overheated at 1320°C. There was no fine second γ′ phase in the γ matrix channel of the alloy after standard heat treatment and overheating at 1320°C. But the fine second γ′ phase precipitated in the γ matrix channel after overheating at every temperature of 1100 °C~1300°C. No obvious change of the stress rupture life was found after overheating at 1100°C, 1150°C, 1200°C and 1250°C. The stress rupture life considerably reduced after overheating at 1300°C, whereas slightly reduced after overheating at 1320°C. The appearance of the raft had almost no change after overheating at 1100°C. With increasing of overheating temperature from 1100°C to 1250°C, the length of raft became shorter and the width thickening. The γ phase formed the wavy raft after overheating at 1300°C and 1320°C and the thickness of latter was larger than that of the former. Finally, the relationship between the microstructural evolution and stress rupture properties of the alloy after overheating was discussed.

Influences of W and Al on the Microstructure and Stress-Rupture Property of Re-Free Ni-Based Single Crystal Superalloys

The influence of W and Al on the solidus and liquidus temperatures, microstructure and stress-rupture property at 980 °C/250 MPa was investigated in three Re-free experimental Ni-based single crystal superalloys. The results indicated that the solidus temperature increased for 14.0 °C and 9.8 °C by adding 0.84 wt.% W only and adding 0.45 wt.% Al and 0.44 wt.% W to the base alloy, respectively. The γ′ morphology changed from nearly cuboidal in the base alloy to cuboidal by adding 0.45 wt.% Al and 0.44 wt.% W. The volume fraction of γ′ precipitates increased, while the γ channel width decreased after adding Al and W. The additions of Al and W improved the stress-rupture life at 980 °C/250 MPa because of higher γ′ volume fraction, narrower γ matrix channel and more complete rafting structure.