Design And Performance Test Of A Coanda Gas Ejector

A Coanda gas ejector has been widely used in many areas, such as, mine ventilation, chemical industry, food industry, automobile industry and so on Therefore, there is an important practical significance for improving the performance of the Coanda gas ejector. Entrainment coefficient is a main indicator which represents ejector's performance. How to reasonably design Coanda gas structure parameters, improve ejector entrainment air flow and entrainment coefficient are major problems to be solved in industrial practice.At present, the study about Coanda gas ejector are mainly focused on inner flow field, such as the analysis on Mach number, pressure and velocity on primary flow airflow cross section of the inlet and secondary airflow cross section of the inlet and mixed airflow cross section of the outlet.Besides, there is less study showed the effect on ejectors of annular gap width and the primary flow pressure and so on. The study of Coanda gas ejector design and performance testing will help the development of Coanda gas ejector in industry. In addition, the entrainment air volume of existing Coanda gas ejectors actually lower than the theoretical calculated value. Thus, it has great practical significance to build model and numerical simulate by application of CFD software, by analyzing the trends of entrainment coefficient under different parameters and pressure conditions to decide optimal structural parameters of Coanda gas ejectors.This paper introduces the working principle of Coanda gas ejector, domestic and foreign research present situation and existing problems. From the view of the industrial application, based on the existing theory, applying the method of numerical simulation and experiment to research. On the numerical simulation hand, the application of AN SYS ICEM CFD software and fluent software for simulation and analysis of different structure parameters about the influence of the ejector performance. Pointing at the throat diameter of less than 100 mm of Coanda gas ejector, on the base of the results of numerical simulation, designing the structure size. On the experimental test hand, machining the test prototype and measuring the related parameters. Besides, experimental data are compared with the numerical simulation results.Firstly, in view of the structure parameters that influence of the Coanda gas ejector performance, such as, annular gap width (e), ejector throat diameter (d), and so on. Establishing different grid models, changing the primary flow compressed air pressure and carrying out numerical simulations. Obtaining annular gap width (e), ejector throat diameter (d) as well as the primary flow of air pressure (P) how to influence the primary and induced mass flow, volume flow and entrainment coefficient.Secondly, according to the numerical simulation results, determining the reasonable structure size, designing and processing the Coanda gas ejector primary type and improved type.Thirdly, in order to test the performance of the Coanda ejector primary type and improved type, this paper used an Pitot tube as an main experimental apparatus, and had done two experiments respectively by log-linear measurement method and the method of under different primary flow compressed air pressure, ejector induced flow inlet cross section of any measuring point velocity and cross section average velocity ratio is a constant value. By the experiments, obtaining the primary and induced mass flow, volume flow and entrainment coefficient under the condition of different primary flow pressure, and analyzing the test results.Finally, according to the structure size of the primary type and the improved type of the Coanda ejector, and the experimental conditions. There are two grid models were established and were calculated respectively by numerical simulation. Besides, the numerical simulation results and the experimental data were compared and validated.