Novel, multiple-stage ignitions in the spontaneous combustion of acetaldehyde
| Autor: | John Griffiths, S. M. Hasko, P. g. Lignola, Peter Gray |
|---|---|
| Rok vydání: | 1981 |
| Předmět: |
Range (particle radiation)
Meteorology General Chemical Engineering Formaldehyde General Physics and Astronomy Energy Engineering and Power Technology General Chemistry Cool flame Residence time (fluid dynamics) law.invention Ignition system Stress (mechanics) chemistry.chemical_compound Fuel Technology chemistry law Chemical physics Methanol Physics::Chemical Physics Spontaneous combustion |
| Zdroj: | Combustion and Flame. 43:175-186 |
| ISSN: | 0010-2180 |
| DOI: | 10.1016/0010-2180(81)90015-8 |
| Popis: | This paper describes novel modes of spontaneous, multiple-stage ignitions. The emphasis is on the identification and location of modes of behavior when CH 3 CHO+O 2 reacts in well-stirred conditions at pressures in the range 0–25 kN m −2 and temperatures in the range 450–650K at a residence time of 3 s. The modes that can be distinguished are either steady or oscillatory. In the oscillatory regime either (i) repetitive ignitions, (ii) repetitive cool flames, or (iii) new forms of multiple-stage, hybrid ignitions occur. In (iii), the repetitive cycles include one or more cool flames, reproducibly up to five, accompanying each ignition. Although temperature changes and light intensities are often sufficient to distinguish cool flames from ignition instabilities, here we stress also continuous chemical analysis by mass spectrometry, from which categoric distinctions are made. In cool flames, temperature rises do not exceed ≈200K, molecular intermediates (such as formaldehyde, methanol, hydrogen peroxide, etc.) build up, and oxidation is never complete: no more than half the fuel is consumed at each pulse. In ignition, temperature changes exceed 200K, molecular intermediates are destroyed, the sole products are carbon oxides and water, and reaction is complete. In hybrid oscillations, cool flame excursions are distinguished from ignition excursions especially by the form of the concentration time profiles for the molecular intermediates. Ignition pulses in the flow system occur in two stages: the first is a cool flame, and a hot ignition follows before this flame declines. There are important comparisons of this and the more complex, multiple-stage phenomena to be made with the spontaneous ignition that occurs in engines. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|