Air Ejector Pumping Enhancement Through Pulsing Primary Flow

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information CANADA. SPONSORING I MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSORIMONITOR'S ACRONYM(S)Air 14. ABSTRACT Improving the performance of an ejector is a flow control problem. Passive methods such as changing the geometry of the mixing tube showed that, for a simple mixing tube geometry of a concentric cone-tube combination, the diameter of the tube had to be at least 4 times the diameter of the primary nozzle. Thus for a 5.13 mm dia. primary jet, a 22.7 mm dia. tube was 27% better than a 17.41 mm dia. tube. A standard Venturi mixing tube with 17.41 mm dia. throat was 100% better. Also the shape of the entrance cone had only a little effect and could be substituted by other shapes. A tube without an entrance shape was found to be still reasonably efficient.Both experiments and Computer Fluid Dynamics(CFD) analysis show that pulsing the primary jet flow, an active method of flow control, improved ejector performance. The physics of this improvement has been discussed. Pumping effectiveness of the ejector was found to be proportional to the square of the pulsation strength. The details of the many pulsators tested are discussed. The majority of the improvement appears to be due to the initial toroidal vortex, the pulsation produces. The improvement was strongest at 127-131 Hz, less than half the fundamental frequency of 746 Hz of the system. The pumping effectiveness increased by up to 4.5 times that for a steady jet. Different types of pulse shapes tested indicate that a sinusoidal pulse superimposed on a steady flow is very efficient. For pulses which have only positive pulse velocities, a narrow pulse was more efficient. The data also showed that a strong synthetic jet actuator gave ejector performance as good as a pulsed jet with primary flow. SUBJECT TERMS SECURITY CLASSIFICATION OF:17 The objective of the proposed work is to conduct research into using acoustically driven or pulsed ejectors capable of pumping increased secondary flows in ejector assemblies. Previous research has demonstrated that increased entrainment is possible in pulsed ejector designs, and the current research project will further investigate the mechanisms for this augmentation. Approach:An existing test rig will be used to conduct research establishing the geometry, pulsing frequencies, and amplitudes for optimum ejector efficiency. Complementary computational studies will be performed to further investigate the mechanisms by which additional entrainment is achieved in these configurations. Progress:Year: 2004 Month: The p...

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 1: Single-Phase Ejectors

“…The concept was applied for cases of MED-TVC desalination systems (multi-effect desalination system with thermal vapor compression) [38,39]. Another concept proposed by Vermeulen [40] is pulsed ejection. A pulsed primary flow is injected with a variable frequency and amplitude.…”

“…Some ejector geometries of interest proposed in the literature and introduced above are listed in Table 1, below. Another concept proposed by Vermeulen [40] is pulsed ejection. A pulsed primary flow is injected with a variable frequency and amplitude.…”

Design Enhancement of Eductor for Active Vapor Transport and Condensation during Two-Phase Single-Species Flow

“…The use of a lobbed nozzle improved the entrainment ratio but harmed compression ratios [5]. The use of sinusoidal pulsed jets for enhancing mixing was found to be comparatively efficient [6].…”