Auto-ignition during instationary jet evolution of dimethyl ether (DME) in a high-pressure atmosphere

Journal Article · Thu Jan 15 00:00:00 EST 2009 · Combustion and Flame

DOI:https://doi.org/10.1016/J.COMBUSTFLAME.2008.07.015· OSTI ID:21227385

Fast, G; Kuhn, D; Class, A G ^[1]; Maas, U ^[2]

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1. Institut fuer Kern- und Energietechnik, Forschungszentrum Karlsruhe GmbH, Weberstrasse 5, D-76133 Karlsruhe (Germany)
2. Institut fuer Technische Thermodynamik, Universitat Karlsruhe (TH), Kaiserstrasse 12, D-76128 Karlsruhe (Germany)

The auto-ignition process during transient injection of gaseous dimethyl ether (DME) in a constant high-pressure atmosphere is studied experimentally by laser-optical methods and compared with numerical calculations. With different non-intrusive measurement techniques jet properties and auto-ignition are investigated at high temporal and spatial resolution. The open jet penetrates a constant pressure oxidative atmosphere of up to 4 MPa. During the transient evolution, the fuel jet entrains air at up to 720 K. The subsequent auto-ignition of the ignitable part of the jet occurs simultaneously over a wide spatial extension. The ignition delay times are not affected by variation of the nozzle exit velocity. Thus, the low-temperature oxidation is slow compared with the shorter time scales of mixing, so that chemical kinetics is dominating the process. The typical two-stage ignition is resolved optically with high-speed shadowgraphy at a sampling rate of 10 kHz. The 2D fields of jet velocity and transient mixture fraction are measured phase-coupled with Particle Image Velocimetry (PIV) and Tracer Laser Induced Fluorescence (LIF) during the time-frame of ignition. The instationary Probability Density Functions (PDF) of mixture fraction are described very well by Beta functions within the complete area of the open jet. Additional 1D flamelet simulations of the auto-ignition process are computed with a detailed reaction mechanism for DME [S. Fischer, F. Dryer, H. Curran, Int. J. Chem. Kinet. 32 (12) (2000) 713-740; H. Curran, S. Fischer, F. Dryer, Int. J. Chem. Kinet. 32 (12) (2000) 741-759]. Calculated ignition delay times are in very good agreement with the measured mean ignition delay times of 3 ms. Supplemental flamelet simulations address the influence of DME and air temperature, pressure and strain. Underneath a critical strain rate the air temperature is identified to be the most sensitive factor on ignition delay time. (author)

• OSTI ID: 21227385
• Journal Information: Combustion and Flame, Vol. 156, Issue 1; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
METHYL ETHER
PRESSURE RANGE MEGA PA 01-10
AIR
IGNITION
JETS
PROBABILITY DENSITY FUNCTIONS
COMBUSTION KINETICS
AUTOIGNITION
MIXTURES
TEMPERATURE DEPENDENCE
TIME DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
EVOLUTION
TRANSIENTS
VELOCITY
SIMULATION
STRAIN RATE
TIME DELAY
STRAINS
COMPUTERIZED SIMULATION