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TECHNICAL PAPERS

Experimental Validation of the Addition Principle for Pulsating Flow in Close-Coupled Catalyst Manifolds

[+] Author and Article Information
Tim Persoons

Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300A, B-3001 Leuven, Belgiumtim.persoons@mech.kuleuven.be

Ad Hoefnagels

 BOSAL International, Advanced Engineering and Testing, Lummen, Belgium

Eric Van den Bulck

Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300A, B-3001 Leuven, Belgium

J. Fluids Eng 128(4), 656-670 (Feb 01, 2006) (15 pages) doi:10.1115/1.2201646 History: Received August 22, 2005; Revised February 01, 2006

Designing an exhaust manifold with close-coupled catalyst (CCC) relies heavily on time-consuming transient computional fluid dynamics. The current paper provides experimental validation of the addition principle for pulsating flow in CCC manifolds. The addition principle states that the time-averaged catalyst velocity distribution in pulsating flow equals a linear combination of velocity distributions obtained for steady flow through each of the exhaust runners. A charged motored engine flow rig provides cold pulsating flow in the exhaust manifold featuring blow down and displacement phases, typical of fired engine conditions. Oscillating hot-wire anemometry is used to measure the bidirectional velocity, with a maximum measurable negative velocity of 1ms. In part load and zero load conditions, instantaneous reverse flow occurs following the blow-down phase. The two-stage nature of the exhaust stroke combined with strong Helmholtz resonances results in strong fluctuations of the time-resolved mean catalyst velocity. The validity of the addition principle is quantified based on the shape and magnitude similarity between steady and pulsating flow distributions. Appropriate nondimensional groups are used to characterize the flow and quantify the similarity. Statistical significances are provided for the addition principle’s validity. The addition principle is valid when the nondimensional scavenging number S exceeds a critical value Scrit, corresponding to cases of low engine speed and/or high flow rate. This study suggests that the CCC manifold efficiency with respect to catalyst flow uniformity could be quantified using a single scalar parameter, i.e., Scrit. The results from the current study are discussed with respect to previously reported results. The combined results are in good agreement and provide a thorough statistically founded experimental validation of the addition principle, based on a broad applicability range.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 12

Stationary averaged distribution according to Eq. 14 (left) and time-averaged distribution on CME (right), for scavenging number S=0.779

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Figure 11

Stationary velocity distributions for flow through each runner (r=1 through 4 from top left to bottom right)

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Figure 10

Spectra of time-resolved mean velocity on CME (left) and isothermal (right) flow rig, for N=1200rpm and Q≅100m3∕h

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Figure 9

Time-resolved velocity in part (left) and zero (right) load conditions on CME flow rig

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Figure 8

Time-resolved velocity on CME (left) and isothermal (right) flow rig, for comparable engine speed and flow rate, corresponding to full load

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Figure 7

Influence of OHW frequency Rf on flow rate deviation (left) and time-resolved mean velocity (right)

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Figure 6

Nondimensional OHW calibration chart at varying oscillation frequency

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Figure 5

OHW probe velocity, phase-locked with engine crankshaft position

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Figure 4

OHW nomenclature

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Figure 3

OHW used to measure bidirectional velocity

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Figure 2

Comparison of exhaust runner velocity for CME and isothermal flow rig

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Figure 1

CME flow rig overview (left) and Manifold B (right)

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Figure 13

Stationary averaged distribution according to Eq. 14 (left) and time-averaged distribution on CME (right), for scavenging number S=0.300

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Figure 14

Stationary averaged distribution according to Eq. 14 (left) and time-averaged distribution on isothermal flow rig (right), for scavenging number S=0.754

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Figure 15

Stationary averaged distribution according to Eq. 14 (left) and time-averaged distribution on isothermal flow rig (right), for scavenging number S=2.249

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Figure 16

Correlations of similarity measures rS (left) and rM (right) versus scavenging number, using old definition of Tp (Eq. 11)

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Figure 17

Correlations of similarity measures rS (left) and rM (right) versus scavenging number, using new definition of Tp (Eq. 12)

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