Performance Improvement of Forced Draught Jet Ejector Using Constant Rate Momentum Change Method
S. Gurulingam1, A. Kalaisselvane2, N. Alagumurthy3
1S. Gurulingam, Research scholar, Department of Mechanical Engineering, Pondicherry Engineering College, India.
2A. Kalaisselvane, Assistant Professor, Department of Mechanical Engineering, Pondicherry Engineering College, India.
3N. Alagumurthy, Professor, Department of Mechanical Engineering, Pondicherry Engineering College, India.
Manuscript received on September 23, 2012. | Revised Manuscript received on October 17, 2012. | Manuscript published on October 30, 2012. | PP: 149-151 | Volume-2 Issue-1, October 2012.  | Retrieval Number: A0753102112/2012©BEIESP

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Abstract: A jet ejector uses a jet of primary fluid to induce a peripheral secondary flow often against back pressure. Expansion of primary jet produces a partial vacuum near the secondary flow inlet creating a rapid re-pressurization of the mixed fluids followed by a diffuser to increase the pressure at the exit. Using the geometrical design parameters obtained by solving the governing equations, a CFD analysis is made using the FLUENT software to evaluate the optimum entrainment ratio that could be achieved for a given set of operating conditions, where the entrainment ratio (ER) is the ratio of the mass flow rate of the secondary fluid (propelled stream) to the primary fluid (motive fluid). The three main internal process forming sources of ejector irreversibility are mixing, kinetic energy losses, and normal shock. The CRMC method produces a diffuser geometry that removes thermodynamic shock process with in the diffuser at the design point-operating conditions. In order to match the ER that is achievable theoretically, an effort is made to force charge the propelled stream using a blower so that the momentum difference between the motive and the propelled fluid is minimized. The decrease in momentum difference increases the ER and the pressure lift ratio (PDE/PS) compared to the values obtained using the conventional methods, where PDE is the exit pressure and PS is the secondary fluid pressure. It also reduces losses due to pure mixing and kinetic energy loss. Experimental results obtained using the forced draft system is found to match the results obtained from the FLUENT analysis.
Keywords: Ejector, Efficiency, Irreversibility, CRMC, Forced Draught.