Summary Placing a flow tube on the wellhead to suction flame during a well control operation is key to creating a safe environment near the wellhead. Aiming at the problem that the internal flame of the flow tube can easily leak during the rescue of a high-pressure gas well, we propose in this paper to use the self-excited negative pressure effect to improve the capacity to suction flame. Based on the coupling method of the Reynolds averaged Navier-Stokes equation and mixed combustion model, a gas well combustion model is established. The accuracy of the model is verified by proportional scaling experiment. Furthermore, the sensitivity analysis of key structural parameters of self-excited negative pressure flow tube is carried out, and the structure of the flow tube optimized. The result shows that the optimized flow tube has a suction flow about twice that of the horn flow tube, and the suction scope is increased by 61.5%, which greatly improves the flame suction capacity. The research work can provide guidance for structural design and optimization under self-excited negative pressure effect.

Negative pressure wards are significant in preventing the spread of infectious pathogens which play a crucial role in fighting against COVID-19. Owing to the negative pressure, contaminated air with pathogens is not able to flow from the wards to non-contaminated zones while fresh filtered air will be transported to the ward via the ventilation system. As airflow controlled by ventilation systems affects the motion of pathogens, for example, infectious aerosol particles, the ability of a negative pressure ward to reduce the risk of infection highly relies on an effective ventilation system. In this investigation, impacts of airflow patterns under various human postures and ventilation processes aerosols diffusion are analyzed via the computational fluid dynamics (CFD) simulation. According to the results, among three airflow patterns, the highest contaminant removal efficiency is 57% at 200 s with the top supply and bottom return mode; besides, in three postures, in the case that the patient is in a standing position, the contaminant removal efficiency is the highest. Furthermore, it is found that the best airflow scheme is a slit tuyere in the ward, with a top supply and side return mode and a sitting position for the patient. This study may provide a reference for the design of airflow in negative pressure isolation wards, control of contaminants, and prevention of viral infections, so as to ensure a good working and recovery environment for medical staff and patients.