Effects of LIF Tracers on Combustion in a DI HCCI Engine 2008-01-2407
Many experimental efforts to track fuel-air-residual mixture preparation in internal combustion engines have employed laser induced fluorescence (LIF) of tracers. Acetone and 3-pentanone are often chosen as tracers because of their relatively strong LIF signal, weak quenching, and reasonable match to thermo-chemical properties of common fuels such as iso-octane. However, the addition of these tracers to fuel-air mixtures could affect combustion behavior. In this work, we assess these effects to better understand limitations of tracer-based engine measurements.
The effects of tracer seeding on combustion phasing, duration, and variation are studied in an HCCI engine using a recompression strategy to accommodate single- and multi-stage-ignition fuels. Using direct-injected (DI) fuels iso-octane and n-heptane, comparisons are made of combustion performance with and without seeding of the intake air (air seeding, as opposed to the more common fuel seeding, is a variation of LIF used to measure residual-gas concentration). Chemical and premixing effects of tracer addition are distinguished by substituting equivalent amounts of fuel for the tracer. Chemical kinetic simulations of iso-octane and n-heptane oxidation help explain the experimentally determined trends.
Results show that the phasing of iso-octane combustion can be significantly impacted by premixing effects because of the sensitivity of ignition to charge temperature. For n-heptane, the chemical effects of tracer addition are shown to be more pronounced because of impact on low-temperature heat release. Acetone retards the combustion for both single- and two-stage-ignition fuels, whereas 3-pentanone advances iso-octane combustion while retarding n-heptane. Overall, we found that the impact of tracer addition is modest for the chosen operating conditions since varying the intake temperature can easily compensate for it.
Citation: Fitzgerald, R., Steeper, R., and Snyder, J., "Effects of LIF Tracers on Combustion in a DI HCCI Engine," SAE Int. J. Fuels Lubr. 1(1):1491-1502, 2009, https://doi.org/10.4271/2008-01-2407. Download Citation
Author(s):
Russell P. Fitzgerald, Richard R. Steeper, Jordan A. Snyder
Affiliated:
Sandia National Laboratories, Stanford University
Pages: 12
Event:
Powertrains, Fuels and Lubricants Meeting
ISSN:
1946-3952
e-ISSN:
1946-3960
Also in:
SAE International Journal of Fuels and Lubricants-V117-4EJ, SAE International Journal of Fuels and Lubricants-V117-4
Related Topics:
HCCI engines
Combustion and combustion processes
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