An Experimental Study of the Mixing by an Acoustically Pulsed Axisymmetrical Air-Jet

Vermeulen, P. J.; Yu, Wai Keung

doi:10.1115/85-gt-49

Cited by 6 publications

(11 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such a result agrees with the numerical results of Jackson et al (1993), who found that flame ignition is always enhanced at high frequencies. It also matches the results of Vermeulen and Yu (1987), who found the strength of the induced vortices approximately increases with frequency. Besides, Vermeulen et al (1992) found that the entrainment coefficient changes faster with pulsation strength at higher frequencies, because the toroidal vortex spacing is less at the greater frequencies.…”

Section: Effect Of Strouhal Numbersupporting

confidence: 90%

“…A Nikon digital camera was utilized to record the flame images of 2560 Â 1920 pixels at shutter speeds between 8 and 1=4000 for qualitative comparison. The corresponding parameters of acoustics are Sr ¼ fD f =U f , according to Vermeulen and Yu (1987), and pulsation strength U e =U j ¼ C Â W 0:5 =½U j ðm o j Þ 0:5 , as given by Vermeulen et al (1992a). The linearity between the pulsation strength, U e =U j , and the power number, W 0:5 =½U j ðm o j Þ 0:5 , is given in the correlations by Vermeulen et al (1992a).…”

Section: Combustion Enhancement Of Flares By Excitation 1633mentioning

confidence: 99%

“…Consequently, the interaction between the acoustically driven turbulence (Hill and Greene, 1977;Kibens, 1980) and the aerodynamically controlled turbulence in the burner wake zone (Lewis et al, 1988) is investigated. In this sense, acoustics influences both mixing and flame stability by the vortex shedding from the nozzle (Vermeulen and Yu, 1987;Vermeulen et al, 1995). The burner geometry influences the flame behavior by enlarging the size of the recirculation zone as found for elliptical nozzles (Gollahalli and Pardiwalla, 2002) with higher rates of entrainment (Ho and Gutmark, 1987).…”

Section: Introductionmentioning

confidence: 96%

“…The enhancement is fulfilled by developing a train of toroidal vortices and controlling their frequency with respect to the flow timescales for maximum entraining effects (Vermeulen and Ramesh, 1998;Vermeulen et al, 1995), where the total centerline turbulence level becomes the highest (Hussain and Husain, 1989) and the largest scales in the jet are formed (Kibens, 1980). Vermeulen et al (Vermeulen and Ramesh, 1997;Vermeulen and Yu, 1987;Vermeulen et al, 1982Vermeulen et al, , 1990Vermeulen et al, , 1992aVermeulen et al, , 1992bVermeulen et al, , 1993Vermeulen et al, , 1995 used acoustical excitation to improve jet entrainment and temperature pattern for applications in gas-turbine secondary-zone mixing with dilution air.…”

Section: Introductionmentioning

confidence: 97%

See 3 more Smart Citations

Combustion Enhancement of a Gas Flare Using Acoustical Excitation

Behery

Mohamad

Kamal

2005

Combustion Science and Technology

View full text Add to dashboard Cite

The effect of acoustical excitation on flame stability, trajectory, exhaust emissions, and gas temperatures from a gas flare stack in a crossflow was experimentally investigated. Circular, elliptical, and cup nozzle configurations were examined and compared with a sinusoidal wave excitation. It was found that increasing the pulsation amplitude enhances the combusting efficiency up to the quenching limit. Increasing the Strouhal number enhances the mixing with an optimum value at 0.25. With acoustical excitation, there was a reduction in the CO, unburned hydrocarbon (UHC), and NO x concentrations. It was found that the elliptical burner exhibits the widest stability range with respect to the pulsation strength, with the highest average CO concentration. The cup nozzle produced the least amounts of CO and UHC. Both nozzles revealed higher flame temperatures than those of the circular nozzle. There was an increase in flame temperatures with excitation, with the subsequent widening and reduction in flame length.

show abstract

Section: Effect Of Strouhal Numbersupporting

confidence: 90%

Section: Combustion Enhancement Of Flares By Excitation 1633mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Combustion Enhancement of a Gas Flare Using Acoustical Excitation

Behery

Mohamad

Kamal

2005

Combustion Science and Technology

View full text Add to dashboard Cite

show abstract

“…The kinetic energy of the primary jet flow is then, Kinetic Energy=l1/2 pjAj(Uj +Ue sin(0)) 3 The average kinetic energy is obtained by integrating the sine wave over a cycle and dividing by 2x which give~s Average Kinetic Energy=1/2 pjAj (uj 3+1 .5Uj~e 2).…”

Section: Recommendationsmentioning

confidence: 99%

Air Ejector Pumping Enhancement Through Pulsing Primary Flow

Vermeulen

Ramesh

Meng

et al. 2004

2nd AIAA Flow Control Conference

View full text Add to dashboard Cite

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...

show abstract