Mixing and flame structures inferred from OH-PLIF for conventional and low-temperature diesel engine combustion
- General Motors Research and Development, Warren, MI 48090 (United States)
- Sandia National Laboratories, Livermore, CA 94551 (United States)
- Department of Mechanical Engineering, University of Wisconsin, Madison, WI 53706 (United States)
The structure of first- and second-stage combustion is investigated in a heavy-duty, single-cylinder optical engine using chemiluminescence imaging, Mie-scatter imaging of liquid-fuel, and OH planar laser-induced fluorescence (OH-PLIF) along with calculations of fluorescence quenching. Three different diesel combustion modes are studied: conventional non-diluted high-temperature combustion (HTC) with either (1) short or (2) long ignition delay, and (3) highly diluted low-temperature combustion (LTC) with early fuel injection. For the short ignition delay HTC condition, the OH fluorescence images show that second-stage combustion occurs mainly on the fuel jet periphery in a thickness of about 1 mm. For the long ignition delay HTC condition, the second-stage combustion zone on the jet periphery is thicker (5-6 mm). For the early-injection LTC condition, the second-stage combustion is even thicker (20-25 mm) and occurs only in the down-stream regions of the jet. The relationship between OH concentration and OH-PLIF intensity over a range of equivalence ratios is estimated from quenching calculations using collider species concentrations predicted by chemical kinetics simulations of combustion. The calculations show that both OH concentration and OH-PLIF intensity peak near stoichiometric mixtures and fall by an order of magnitude or more for equivalence ratios less than 0.2-0.4 and greater than 1.4-1.6. Using the OH fluorescence quenching predictions together with OH-PLIF images, quantitative boundaries for mixing are established for the three engine combustion modes. (author)
- OSTI ID:
- 21227394
- Journal Information:
- Combustion and Flame, Vol. 156, Issue 10; Other Information: Elsevier Ltd. All rights reserved; ISSN 0010-2180
- Country of Publication:
- United States
- Language:
- English
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