Investigation of the supersonic steam injector operation mode

Highlights: • Steam-water experiment was performed using central water-jet type steam injector (SI). • SI's pumping capability as a passive jet-pump was confirmed. • SI's operation mode was assessed using jet stability criteria. - Abstract: Steam injector (SI) operates as passive jet pump and heat exchanger, which is activated only by the high-pressure steam and water. SI possess simple geometry and does not require any external power supplies nor rotating machinery for the operation. It is capable of discharging subcooled water at higher pressure than the inlet, and operable as a passive jet pump. In addition, direct contact condensation heat transfer between steam and water-jet provides superior heat exchanging characteristics, more than 1,000 times that of shell and tube heat exchangers. Due to these advantageous features, SI has a great potential to be applied as a passive safety system of nuclear power plants including existing light water reactors and next generation reactors. In the present study, SI experiments targeting for the operating range and the pumping performance were carried out at 0.02–0.81 MPa inlet steam pressure and 0.21–0.80 kg/s inlet water flow rate. The SI body was manufactured by stainless steel equipped with overflow port. The water injection nozzle was designed with shaft-driving mechanism to adjust the axial location of the water jet and steam inlet area. During the experiment, SI's pump performance and operation mode were investigated by changing the inlet conditions. Maximum attainable discharge pressure and operation state of the SI were recorded at each inlet condition. In this study, liquid jet break-up length was considered to assess the SI's operation mode. Clear boundaries to explain the SI's operational range were obtained using the jet stability analysis. The research results presented here provides significant aspect to properly design operable SI as the passive safety system.