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Research Papers: Flows in Complex Systems

Supersonic Jet Impingement on a Cylinder and Characterization of the Resulting Deflected Jets

[+] Author and Article Information
Ameya Pophali

Department of Chemical Engineering and
Applied Chemistry,
University of Toronto,
200 College Street,
Toronto, ON M5S 3E5, Canada
e-mail: ameya.pophali@aecom.com

Markus Bussmann

Department of Mechanical and
Industrial Engineering,
University of Toronto,
5 King's College Road,
Toronto, ON M5S 3G8, Canada
e-mail: bussmann@mie.utoronto.ca

Honghi Tran

Department of Chemical Engineering and
Applied Chemistry,
University of Toronto,
200 College Street,
Toronto, ON M5S 3E5, Canada
e-mail: honghi.tran@utoronto.ca

1Present address: Mining and Metals, AECOM, 85 rue Sainte-Catherine Ouest, Montreal, QC H2X 3P4, Canada.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received December 19, 2012; final manuscript received July 6, 2014; published online September 4, 2014. Editor: Malcolm J. Andrews.

J. Fluids Eng 136(11), 111103 (Sep 04, 2014) (11 pages) Paper No: FE-12-1643; doi: 10.1115/1.4027993 History: Received December 19, 2012; Revised July 06, 2014

The interaction between a mildly underexpanded supersonic jet and a single cylinder was studied experimentally at laboratory scale by using the schlieren technique coupled with high-speed photography and pitot pressure measurements. This study was motivated by the need to optimize sootblowing operation in kraft recovery boilers. The effects of the transverse distance between the jet and cylinder centerlines (eccentricity), nozzle–cylinder distance, and cylinder size on jet–cylinder interaction were determined. Results show that upon impingement on a cylinder, a supersonic jet deflects at an angle and creates a weaker supersonic jet that we refer to as a “secondary” jet. The angle and strength of the deflected or secondary jet depend on the eccentricity between the primary jet and cylinder centerlines. When a jet impinges on a cylinder of diameter comparable to that of the jet or smaller, secondary jets form not only when the cylinder is placed close to the nozzle (in the stronger portion of the jet) but also when the cylinder is placed far away (in the jet's weaker portion; up to 20–24 nozzle exit diameters in the present study). Changing the eccentricity slightly results in a significant change in the secondary jet characteristics. For a cylinder much larger than the jet, secondary jets do not form at zero eccentricity (head-on impingement); the eccentricity at which they begin to form increases with the cylinder size. A study of the secondary jets shows that they spread out much more than the primary jet and are sheet- or fan-like with an oblong, oval cross section. The centerline pitot pressure of the secondary jets remains as high as the primary jet for a considerable distance from the tube only during weak interaction between the primary jet and the cylinder (i.e., during strongly eccentric/off-centerd impingement). As the interaction between the primary jet and the cylinder intensifies at lower eccentricities, the maximum centerline pitot pressure of the secondary jet decreases, and the pitot pressure decreases more quickly with distance from the tube.

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References

Figures

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Fig. 1

A sootblower removing deposits from a platen of tubes

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Fig. 2

Parameters governing the flow field of a jet impinging on a cylinder

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Fig. 3

Experimental apparatus

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Fig. 4

Jet impinging on a cylinder at different eccentricities (x = 6.8de)

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Fig. 5

Formation of secondary jets

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Fig. 6

Secondary jet angle versus eccentricity (x = 6.8de)

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Fig. 7

Effect of nozzle–cylinder distance on jet–cylinder interaction for three cylinder sizes (eccentricity = 0)

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Fig. 8

Centerline pitot pressure profile of a laboratory free supersonic jet (po—nozzle supply pressure; ppit—jet pitot pressure)

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Fig. 9

Secondary jet at 0.75R eccentricity for a 1.27 cm OD cylinder (de/D = 0.58) at x = 6.8de: (a) in the plane of the primary jet (cylinder horizontal in front of the nozzle) and (b) in the plane of the secondary jet (cylinder vertical in front of the nozzle; primary jet out of plane by 34 deg, the corresponding secondary jet angle at 0.75R eccentricity)

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Fig. 10

Secondary jets at different eccentricities: de/D = 0.58 and x = 6.8de

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Fig. 11

Centerline pitot pressure of secondary jets at different eccentricities: de/D = 0.58 and x = 6.8de; the primary jet centerline pitot pressure is shown for comparison

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