Improvement of the Combustion Completeness of Hydrogen Jet Flames within a Mesoscale Tube under Zero Gravity

Microjet hydrogen flames can be directly used as micro heat sources or applied in propulsion systems. In our previous study, under zero gravity and without an active air supply, the combustion completeness of jet within a mesoscale tube with inner diameter 5 mm was very low. this we were dedicated to improving efficiency by using convergent nozzle (tilt angle around 68°) instead straight one, exit 0.8 0.4 mm. The numerical results demonstrate that maximum case d= only 15%; however, peak value for d = 36%. This happened because mm, fuel velocity four times case. Hence, negative pressure combustor decreased much lower level compared which led enhancement entrainment ratio. However, highest still below 36%; therefore, slightly larger even smaller will necessary further improvements efficiency.