Hydrogen blended with natural gas is one of the best ways for large-scale hydrogen transportation; however, pipeline steels exploited for transferring natural gas have the risk of hydrogen embrittlement. Therefore, the hydrogen damage mechanism and resistance property of different steel pipelines should be carefully examined to select suitable materials for the task mentioned above. The common X42, X52, X70, and AISI 1020 are taken into account as research objects. Their mechanical properties and hydrogen absorption properties in a hydrogen environment are investigated to explore further factors affecting the hydrogen embrittlement of material. Dynamic slow strain rate tensile test results show that these materials exhibit varying hydrogen embrittlement sensitivity in a hydrogen environment. AISI 1020 has the highest hydrogen embrittlement susceptibility, then X70, and X42 presents the lowest one. Generally, hydrogen embrittlement behaviours are strengthened by increasing the current density. As the current density grows, the fracture mode of pipeline steels transforms from the ductile fracture to the quasi-cleavage fracture and finally turns into the cleavage fracture. The hydrogen embrittlement fracture of the tensile specimen results from the action of the HEDE and HELP in various zones. TDS test results indicates that the content of C and Mn significantly influence on the hydrogen solubility in metal materials.
The three-dimensional numerical simulation method is coupled with erosion and particle rebound models based on the results of high-temperature erosion tests to systematically study the gas-solid two-phase flow characteristics of a flue gas turbine for the first time. The aerodynamic loss characteristics of the flue gas-steam mixtures and particle erosion mechanism in the flue gas turbine cascade under design and non-design conditions are investigated. The results indicate that the mixing loss of cooling steam and gas, secondary flow loss, and separation loss significantly affect the entropy increment of the rotor cascade. The isentropic efficiency of the flue gas turbine under the design condition is 78.74%. The radial inflow of wheel cooling steam from the axial clearance has a radial impact and mixing effect on the mainstream flue gas, enhancing the generation and development of the secondary flow vortex in the rotor cascade. When the dimensionless cooling steam flow rate is reduced from 1 to 0.6, the isentropic efficiency of the flue gas turbine increases by approximately 0.9%. By contrast, when the dimensionless cooling steam flow rate increases from 1 to 2, the isentropic efficiency decreases by 0.42%. The erosion rate of the leading and trailing edges of the rotor is higher than those at other streamwise locations. The erosion of the rotor leading edge and the blade-tip trailing edge is caused by the high-speed impact of particles above 10?m, while the erosion of the rotor root is caused by the grinding of 1-5-?m particles carried by the secondary flow.
Aviation and ground compressors are susceptible to the erosion of hard particles in the sandy environment, leading to lower performance and shorter service life of the equipment. Although many studies have been performed on this topic, current literature mainly focused on the steady ideal operating conditions of compressors. In this paper, particle motion behavior and erosion characteristics in the blade passage of a 3.5-stage axial compressor under actual service environment are investigated with the RANS numerical simulation method systematically. By comparing the particle trajectories, erosion rate density and other indicators, effect of particle diameter, particle mass concentration, compressor speed and inlet conditions on erosion characteristics are explored in detail. Results show that the value of erosion rate density on the blade pressure side is overall higher than the suction side. The erosion area and intensity of the rotors are generally more serious than stators, especially on the first rotor blade. With variation in particle size, particle diameter of 100 μm becomes the turning point to change the erosion trend of the blades. Moreover, the overall erosion rates increase linearly with increasing mass concentration of inhaled particles. However, its impact on the erosion position and morphology are not obvious. When the compressor speed increases from 6050 rpm to 6650 rpm, the eroded mass of R1 increases by 10.7%, and the casing erosion rate increases about 11 times. Compared with the winter condition, the overall erosion rate in summer increases by 62%. The results of this paper will provide a technology basis for the prediction on particle erosion behavior and formulation of operation and maintenance programs for aero engines and ground gas turbines under the actual service environment.
To more accurately understand and predict the deposition behavior of catalyst particles in the flue gas turbine cascade, test and numerical combined study is performed in this paper. Based on the systematic analysis of the deposition process and physical mechanism of the catalyst particles, the traditional DRW model, critical velocity particle deposition model and removal model were corrected with the user defined function custom function and validated with the actual deposition morphology. On this basis, the effects of the particle Stokes number and flue gas parameters on the particle deposition characteristics of the flue gas turbine cascade were detailed investigated. The results show that the revised DRW model, critical velocity and removal model can more accurately predict the deposition location and deposition rate of particles in the turbine cascade. With the increase in the Stokes number of particles, the average particle impact rate on the blade surface gradually increased, while the average deposition rate showed a trend of first increasing and then decreasing. The average deposition rate of particles in the rotor blade surface is roughly twice as high as that in the stator surface. With the increase of the flue gas expansion ratio, the deposition rate of particles less than 3 μm gradually increases, while the deposition rate of particles greater than 3 μm tends to decrease. In addition, the change in the flue gas expansion ratio has no obvious effect on the particle deposition distribution in different size ranges.
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