A NUMERICAL STUDY ON STEAM EJECTOR OPTIMUM PERFORMANCE | ||||
| The International Conference on Applied Mechanics and Mechanical Engineering | ||||
| Article 37, Volume 18, 18th International Conference on Applied Mechanics and Mechanical Engineering., April 2018, Page 1-17 PDF (372.04 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/amme.2018.34976 | ||||
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| Authors | ||||
| T. A. Ghonim1; M. S. Farag1; A. S. Hegazy2 | ||||
| 1Lecture, Dept. of Mech. Power Engineering, Faculty of Engineering, Menoufia University, Shebin El-Kom, Egypt. | ||||
| 2Professor, Dept. of Mech. Power Engineering, Faculty of Engineering, Menoufia University, Shebin El-Kom, Egypt. | ||||
| Abstract | ||||
| ABSTRACT The present paper introduces a numerical study on the optimum performance of steam ejector at constant pressure ratio. Both the suction and motive fluids are assumed to be dry steam. As a result of the low pressure created at the exit of the supersonic motive steam nozzle, a suction steam is entrained to be mixed with the motive steam where both flows continue flowing towards the ejector exit. Mass ratio of suction to motive flows is a vital parameter to enhance the ejector performance. The objective of the present study is to maximize the steam ejector efficiency by optimizing the ejector mass ratio. The effect of three different geometrical parameters on ejector mass ratio and its efficiency is investigated at constant operating conditions. These parameters are the ejector convergent section angle, the length of the constant area mixing chamber and the ejector divergent section angle. The theoretical model is formulated based on single phase (superheated steam), twodimensional and compressible flow using the finite volume solver, FLUENT 6.3. In addition, steady, axisymmetric horizontal ejector is considered. The realizable k −e model is used to model turbulence in the present simulation. The proposed numerical model is validated with the available experiments in literature. The results showed that the ejector wall static pressure distributions were greatly affected by the three investigated geometrical parameters. Furthermore, at constant operating conditions (motive, suction and back pressures) separation in the ejector divergent section started to take place at 10o at b =4.8o. In order to avoid separation, the ejector divergent section angle must be selected carefully together with the operating conditions. The ejector mass ratio and efficiency increased with increasing the previously stated three geometrical parameters to gain there upper limit values, subsequent to that, the efficiency and mass ratio decreased with increasing these geometrical parameters. Moreover, it is finally concluded that there are certain optimum ejector convergent, divergent angles and the length of the constant area mixing chamber in order to optimize the ejector mass ratio and consequently its efficiency at given constant operating condition. | ||||
| Keywords | ||||
| Steam Ejector; Mass Ratio; Ejector Efficiency; CFD; Geometrical parameters | ||||
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