Hydrogen concentration distribution of hydrogen-blended natural gas in the pressure regulator valve pipeline

Hydrogen delivery through existing natural gas pipeline infrastructure offers a sustainable and cost-effective approach for large-scale distribution while maintaining operational efficiency. In such systems, the high-pressure regulator valves are critical to control the hydrogen flow. However, because of the physical differences between hydrogen and natural gas, hydrogen aggregation can occur during blended natural gas transport. This study employs computational fluid dynamics to investigate how valve opening, hydrogen blending ratio, inlet velocity, temperature, and pressure influence hydrogen concentration distribution within the valve. The results demonstrate that smaller valve openings lead to steeper hydrogen concentration gradients along the pipeline, with the gradient at a 5% valve opening reaching four times that observed at 20%. While increased inlet velocity mitigates these gradients, high flow rates introduce uneven hydrogen distributions near the valve. Higher hydrogen blending ratios and operating pressures further exacerbate concentration non-uniformity. These findings offer critical insights for enhancing safety and performance in hydrogen-blended natural gas delivery systems.