Heat and Mass Transfer

, Volume 31, Issue 5, pp 339–346 | Cite as

Transient combustion of a heating droplet in a gravitational environment

  • L. W. Huang
  • C. H. Chen
Originals

Abstract

The transient combustion characteristics of a droplet suddenly exposed to the envelope flames in an atmospheric environment are studied numerically. Combustion can be divided into a droplet heating-up and a constant-droplet-temperature burning. The naturally-convective flow is not knowna priori, but provided as part of the solution. During the heating-up stage, the temperature and evaporation rate of droplet increase sharply, and the square of diameter decreases slightly as time proceeds. In the following stage, the droplet temperature remains constant, the evaporation rate and droplet diameter decrease with time. The flowfield of natural convection is also presented to demonstrate its interaction with the flame and the transient process. Finally, the fuel accumulation phenomenon is identified and it results in an reduction of evaporation constant.

Keywords

Natural Convection Evaporation Rate Fuel Accumulation Transient Process Atmospheric Environment 

Instationäre Erwärmung eines sich erwärmenden Tröpfchens in einem Schwerkraftfeld

Zusammenfassung

Der instationäre Verbrennungsprozeß eines plötzlich einem Flammenfeld in atmosphärischer Umgebung ausgesetzten Tröpfchens wird numerisch untersucht. Die Verbrennung läßt sich in die zwei Phasen unterteilen: (1) Aufheizphase des Tröpfchens, (2) konstante Tröpfchentemperatur. Die natürliche Konvektionsströmung ist nicht von vorneherein bekannt, sie wird als Teil der Lösung bereitgestellt. Während der Aufheizphase steigen Temperatur und Verdampfungstrate des Tröpfchens stark an, während das Quadrat des Durchmessers langsam abnimmt. In der folgenden Phase verringern sich Verdampfungstrate und Tröpfchendurchmesser mit der Zeit. Das Strömungsfeld imfolge natürlicher Konvektion wird ebenfalls ermittelt, um seince Wechsel-wirkung mit der Flamme und dem Verbrennungsprozeß zu veranschaulichen. Schließlich läßt sich zeigen, daß in der Umgebung des Tröpfchens eine Anhäufung unverbrannten Brenngases erfolgt, was zu einer Abnahme der Verdampfungs-rate führt.

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • L. W. Huang
    • 1
  • C. H. Chen
    • 1
  1. 1.Department of Mechanical EngineeringNational Chiao Tung UniversityTaiwan 30050 Republic of China

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