Abstract
The nozzles of moist-mix shotcrete are the key parts of forming a steady jet flow field and ensuring the uniform mixing of water and other ingredients. In this paper, for optimizing the nozzle of moist-mix shotcrete, both the internal and external field of a variety of spray nozzles were simulated and analyzed by adopting orthogonal test method with Fluent simulation software combined. Then the phase volume fraction and single-phase velocity of the outlet section of flow field inside the nozzles and cloud pictures including single-phase velocity and volume of different sections lengthways in the external flow field of nozzle were obtained. The results demonstrated that the change of different factors and different levels of the same factor affected the shotcreting performance of spray nozzle, but the effect degree is different. Additionally, compared with the traditional nozzle, the rationality of new-type nozzle structure was verified, which provided a basis for the improvement and optimization of the nozzle structure in the future.
Highlights
Compared with its counterparts which are dry-mix and wet-mix, the moist-mix shotcrete equipment is able to avoid problems like large dust volume, high rebound rates, low efficiency of dry-mix shotcrete equipment, and capable of preventing serious pulse, segregation and blockage in wet-mix shotcrete equipment [1,2,3]
Research on nozzle structure is various, but most of them are adoptable. They can be divided into two categories: one is the utilization of computer technology and simulation software to obtain that shotcreting performance are related to the outlet size, channel length and the shape of nozzle [4, 5] and the outlet uniformity of concrete stream of different nozzle structure affects shotcreting effects [6]; the other is, on the basis of experiment and theories, to adopt principles of physics and advanced equipment, which includes high speed cameras and imaging measurement systems, to indicate that shotcreting performance linked with transition length, angle of internal channel and the symmetry of nozzle [7,8,9] and that in the premise of the laws of physics in the spray particle kinematics, predicting the impact velocity of materials while they are leaving nozzles is realized [10]
The velocity distribution of concrete has an effect on efficiency and spray uniformity, so the outlet velocity of concrete is vital to shotcreting performance of moist-mix shotcrete
Summary
Compared with its counterparts which are dry-mix and wet-mix, the moist-mix shotcrete equipment is able to avoid problems like large dust volume, high rebound rates, low efficiency of dry-mix shotcrete equipment, and capable of preventing serious pulse, segregation and blockage in wet-mix shotcrete equipment [1,2,3]. It improves the spraying operation stability with low costs and simple operation. The optimal level combination of structure parameters of nozzle and the flow mixing rule in nozzle were obtained
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