0
Internal Combustion Engines

Effects of Charge Preheating Methods on the Combustion Phasing Limitations of an HCCI Engine With Negative Valve Overlap

[+] Author and Article Information
Laura Manofsky Olesky, Jiri Vavra, Dennis Assanis, Aristotelis Babajimopoulos

 University of Michigan, Ann Arbor, MI Czech Technical University in Prague, Prague, Czech Republic Stony Brook University, Stony Brook, NY

J. Eng. Gas Turbines Power 134(11), 112801 (Sep 21, 2012) (12 pages) doi:10.1115/1.4007319 History: Received May 16, 2012; Revised June 15, 2012; Published September 20, 2012; Online September 21, 2012

Homogeneous charge compression ignition (HCCI) has the potential to reduce both fuel consumption and NOx emissions compared to normal spark-ignited (SI) combustion. For a relatively low compression ratio engine, high unburned temperatures are needed to initiate HCCI combustion, which is achieved with large amounts of internal residual or by heating the intake charge. The amount of residual in the combustion chamber is controlled by a recompression valve strategy, which relies on negative valve overlap (NVO) to trap residual gases in the cylinder. A single-cylinder research engine with fully-flexible valve actuation is used to explore the limits of HCCI combustion phasing at a load of ∼3 bar gross indicated mean effective pressure (IMEPg ). This is done by performing two individual sweeps of (a) internal residual fraction (via NVO) and (b) intake air temperature to control combustion phasing. It is found that increasing both of these variables advances the phasing of HCCI combustion, which leads to increased NOx emissions and a higher ringing intensity. On the other hand, a reduction in these variables leads to greater emissions of CO and HC, as well as a decrease in combustion stability. A direct comparison of the two sweeps suggests that the points with elevated intake temperatures are more prone to ringing as combustion is advanced and less prone to instability and misfire as combustion is retarded. This behavior can be explained by compositional differences (air versus residual gas dilution) which lead to variations in burn rate and peak temperature. As a final study, two additional NVO sweeps are performed while holding intake temperature constant at 30 °C and 90 °C. Again, it is seen that for higher intake temperatures, combustion is more susceptible to ringing at advanced timings and more resistant to instability/misfire at retarded timings.

FIGURES IN THIS ARTICLE
<>
Copyright © 2012 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

FFVA engine schematic

Grahic Jump Location
Figure 2

Example of a recompression valve strategy with a high degree of NVO

Grahic Jump Location
Figure 3

Variation in (a) residual gas fraction and (b) cylinder temperature at IVC as NVO decreases and CA50 retards

Grahic Jump Location
Figure 4

Variation in equivalence ratio (φ and φ′) at a constant fueling rate as NVO decreases and CA50 retards

Grahic Jump Location
Figure 5

Variation in (a) cylinder pressure, (b) rate of heat release, and (c) cylinder temperature as NVO increases at a constant fueling rate and intake air temperature

Grahic Jump Location
Figure 6

Variation in (a) CA50 and cylinder temperature at IVC and (b) equivalence ratio (φ and φ′) as intake temperature is increased at a constant fueling rate

Grahic Jump Location
Figure 7

Variation in (a) cylinder pressure, (b) rate of heat release, and (c) cylinder temperature as intake temperature increases at a constant fueling rate and NVO

Grahic Jump Location
Figure 8

Variation in (a) CA50 and (b) cylinder temperature at IVC for sweeps of NVO and intake temperature

Grahic Jump Location
Figure 9

Comparing (a) fuel-to-charge equivalence ratio φ′, (b) residual gas fraction, (c) fuel-to-air equivalence ratio φ, and (d) in-cylinder molar fraction of O2 at IVC between the NVO and intake temperature sweeps

Grahic Jump Location
Figure 10

Comparing (a) IMEPg , (b) 10–90% mass fraction burn duration, (c) ringing intensity, and (d) COV of IMEP between the NVO and intake temperature sweeps

Grahic Jump Location
Figure 11

Comparing (a) maximum cylinder temperature, (b) combustion efficiency, (c) NOx emissions, (d) CO emissions, and (e) HC emissions between the NVO and intake temperature sweeps

Grahic Jump Location
Figure 12

Comparing (a) fuel–to-charge equivalence ratio φ′, (b) residual gas fraction, (c) fuel-to-air equivalence ratio φ, and (d) molar fraction of O2 at IVC for NVO sweeps at different intake temperatures (30 °C and 90 °C)

Grahic Jump Location
Figure 13

Comparing (a) IMEPg , (b) ringing intensity, and (c) COV of IMEP for NVO sweeps at different intake temperatures (30 °C and 90 °C)

Grahic Jump Location
Figure 14

Comparing (a) 10–90% mass fraction burn duration, (b) maximum cylinder temperature, and (c) NOx emissions for NVO sweeps at different intake temperatures (30 °C and 90 °C)

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In