Flow-Pattern Identification and Pressure-Drop Measurement in a Self-pressurized Flow of Nitrous Oxide

Abstract

This paper discusses the flow characteristics of nitrous oxide, which is widely used as a self-pressurizing oxidant in small rocket engines, especially focusing on a pressure drop model. In a feed line with a tank pressure of 2.5–5.0 MPa, a flow rate of 200–550 g/s, and a pipe inner diameter of 10 mm, the pipe pressure drop was measured using a differential pressure gauge, the void fraction was measured using a capacitance meter, and visualization was performed using a high-speed camera. From the image obtained with a high-speed camera, many fine bubbles of a diameter of about 100–200 µm were observed in our test cases, resulting in a flow classified as a bubble flow. It was clarified that Dukler’s formula can predict the pressure drop within the mean absolute error of 15%.