Effect of inlet angle on the mixing process of hydrogen-blended natural gas in venturi tube

Hydrogen is a clean energy source with great potential for development. However, high delivery costs hinder the development of hydrogen energy. Large-scale and high-efficiency transportation of hydrogen can be achieved through natural gas pipelines. However, it also brings the risk of high concentration of hydrogen aggregation. Therefore, it is necessary to study the mixing efficiency and mixing uniformity of natural gas and hydrogen. Venturi is an efficient gas mixing device. In this paper, the Venturi is modeled and simulated based on Fluent simulation software. The mixing characteristics were studied by changing the inlet angle of the branch tube. The results show that with the increase of inlet angle, the flow direction of methane and hydrogen gradually changes from co-flow to back-flow. This accelerates the friction and collision of the fluid, resulting in energy loss. At the same time, the pressure loss of the model increases. However, the mixing distance of hydrogen mole fraction is shortened from 9.5D to 8.7D. There are high speed zones and low speed zones in the straight tube section of the model, and the velocity stratification phenomenon appears. The research results provide a reference for the structural design and mixing characteristics of the hydrogen-mixed natural gas Venturi Tube.