Ejectors (jet pumps, jet devices) are widely used in various branches of engineering. They are used, in particular, in fuel supply systems and in firing bench tests of liquid-propellant rocket engines. There are different types of ejectors, for example, liquid jet pumps and liquid-gas ejectors. It should be noted that the fluid capacity pumped out by the ejector can vary significantly during operation. Therefore, for rational operation it is necessary to choose the most suitable flow part of the ejector. Despite the simplicity of the design, many issues of the workflow of the ejector and increasing its efficiency currently remain unexplored. In this regard, experimental bench studies of the liquid-gas ejector performance were carried out when simulating bench tests of liquid-propellant rocket engines with various values of gas flow rates and operating pressures in front of the nozzle. The bench allowed testing the characteristics of various jet devices in a wide range of operating parameters when pumping liquid, gas, and gas-liquid mixture. Experiments have shown that the rational length of the ejector mixing chamber when pumping gas substantially depends on the operational parameters of its operation. With increasing pressure of the working flow, the mixing zone is shifted towards the exit of the ejector. In addition, with increasing pressure of the operating fluid, the efficiency of the ejector first increases and then, passing through a maximum, decreases. Therefore, the well-known proposition that the most optimal for a liquid-gas ejector is the mode in which the process of mixing flows ends directly in front of the diffuser should be added: the optimal mode also depends on the value of the operating pressure. Interesting results were obtained in the field of high gas content of pumped products. In the presence of a certain amount of liquid, the jet apparatus ejects a larger amount of gas than in the case of pumping out pure gas, and the pressure, created by the ejector, also increases. Consequently, experiments show that there is the possibility of creating a new method for ejecting gas by supplying a certain amount of liquid to the jet apparatus intake. The obtained results make it possible to select and apply the most suitable flow part of the ejector, including the length of its throat, for efficient operation. © 2020, Univelt Inc. All rights reserved.