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Effects of catalytic walls on hydrogen/air combustion inside a micro-tube

Paper ID Volume ID Publish Year Pages File Format Full-Text
43428 45969 2007 9 PDF Available
Title
Effects of catalytic walls on hydrogen/air combustion inside a micro-tube
Abstract

Numerical simulations with detailed heterogeneous and homogeneous chemistries of hydrogen/air mixture reactions inside a catalytic micro-tube were performed. The characteristics of heterogeneous and homogeneous interaction are delineated in terms of flow velocity, tube diameter and wall thermal conductivity. With the catalytic wall, the homogeneous combustion is obviously weakened. The heterogeneous reactions will consume part of the fuel near the entrance and will make the homogeneous combustion region shift downstream. The micro-tube can be divided into two regions. The upstream region is dominated by the heterogeneous reaction and the downstream region is dominated by the homogeneous combustion. With increasing inlet velocity, the region dominated by heterogeneous reactions expanded downstream and finally occupied the whole tube. Decreasing the tube diameter enhanced the heterogeneous reactions. However, the increased heat released at the wall will be beneficial for homogeneous combustion. The maximum allowed inlet velocity for homogeneous combustion first increased and then decreased to almost zero at 0.2 mm tube. This means that homogeneous combustion can not be sustained inside such a small catalytic micro-tube. Finally, three different wall materials are simulated. Higher wall temperature gradient for lower wall thermal conductivity will promote the homogeneous combustion shift upstream and will have a wider temperature distribution. Since the homogeneous combustion is ignited and sustained by the heat from the heterogeneous reaction, the effect of wall thermal conductivity is not as obvious as it is in the micro-tube without catalyst walls.

Graphical abstractNumerical simulation with detailed heterogeneous and homogeneous chemistries of hydrogen/air mixture reaction inside a catalytic micro-tube is performed. The characteristics of heterogeneous and homogeneous interaction are delineated in terms of flow velocity, tube diameter and wall thermal conductivity. The existence of heterogeneous reaction has two competing effects on homogeneous combustion. Three characteristic reaction types can be schematically depicted in terms of tube diameter and flow velocity in Fig. 1. Moreover, since the homogeneous combustion is ignited and sustained by the heat from heterogeneous reaction, the effect of wall thermal conductivity is not as obvious as that in the micro-tube without catalyst walls.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Numerical simulation; Hydrogen; Catalyst; Micro-tube
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Effects of catalytic walls on hydrogen/air combustion inside a micro-tube
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 332, Issue 1, 1 November 2007, Pages 89–97
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us