The Effect of the DiTertiary Butyl Peroxide DTBP additive on HCCI Combustion of Fuel Blends of Ethan

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The Effect of the Di-Tertiary Butyl Peroxide
(DTBP) additive on HCCI Combustion of Fuel Blends
of Ethanol and Diethyl Ether
J. Hunter Mack Bruce A. Buchholz Daniel L.
Flowers Robert W. Dibble
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
2
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
3
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
4
A number of motivations were behind this set of
experiments.

• A longer combustion events leads to more power
• Different autoignition properties between
  components of dual-fuel blends have been observed
  to change the heat release profile of the
  combustion cycle
• Carbon 14 isotope tracing can be used to track
  the combustion of fuel blend components since
  Ethanol (EtOH) derived from natural sources (i.e.
  grain, grapes) is C14 modern
• DTBP has been observed to advance the combustion
  timing in HCCI engines

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
5
Hypothesis An elongated two-stage combustion
event lowers the peak pressure and the pressure
rise rate in an HCCI engine
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
7
Objectives

• Investigate different fuel blends and observe
  changes in
• Heat Release Duration
• Required Intake Temperature
• Completeness of Combustion

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
8
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Homogeneous Charge Compression Ignition (HCCI)
challenges the Diesel

• Premixed and Lean (PHIlt0.4 ) Low
  Nitric Oxides (NOx)
• High Compression Ratio High
  Efficiency
• Autoignition Event Difficult to Control (no spark
  plugs or diesel fuel injectors to control
  combustion timing)
• Rapid Combustion Event
  Dangerous for Engine
• (dP/dT gt 10 bar/CAD)
• High Peak Cylinder Pressure

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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All living things are naturally labeled with low
levels of Carbon-14 produced in the atmosphere

• Renewable fuels (grain ethanol, biodiesel,
  biogas) are universally labeled (C14 distributed
  evenly throughout the molecules).
• Fossil fuels are essentially C-14 free since the
  carbon has been dead and isolated for more than
  60,000 years (gt 10 half-lives).

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
11
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
12
The three fuel components have drastically
different properties
_at_ 298 K
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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A Caterpillar 3401 Engine was used in the
experiments
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
14
Atomic Mass Spectrometry (AMS) at Lawrence
Livermore National Laboratory (LLNL) easily
counts individual C14 atoms in engine exhaust
samples
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
15
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Single-zone model used in HCCI engine simulations

• Combustion chamber treated as a uniform reactor
  (Well-Mixed Reactor WMR) with uniform
  temperature, pressure, and composition
  throughout These change in time due to
  compression by the piston (slider crank formula)
• Chemical mechanism 112 species / 484 reactions
• Dimethyl Ether (DME) mechanism augmented with
  DEE reactions
• 3. Heat transfer and trapped residuals available
  in the model

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
17
Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
18
The addition of DTBP to 25DEE-in-EtOH fuel
blends significantly affects the dependence
between intake temperature and CA50
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
19
The parameter zeta (?) is a measure of how much
carbon in the exhaust CO2 comes from the EtOH
(normalized to fuel)
? 1 All EtOH burns to CO2 ? 0 No EtOH
burns to CO2
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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The addition of DTBP to DEE/EtOH blends causes
more EtOH to burn to completion
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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CA50 advances more at a constant intake
temperature for blends of DTBP/DEE/EtOH than for
blends of DTBP/EtOH or DEE/EtOH
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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CA50 for 1 DTBP in 25DEE/EtOH and 3 DTBP in
EtOH blends are essentially equal
SAE International Fuels Lubricants Meeting
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CO emissions tenaciously high(oxidation catalyst
likely)
SAE International Fuels Lubricants Meeting
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NOx emissions remarkably low(Major feature of
HCCI)
SAE International Fuels Lubricants Meeting
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CO2 emissions as expected
SAE International Fuels Lubricants Meeting
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There is a weak correlation between CA50 and Heat
Release duration
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Modeling results showing advancement in
combustion timing with the addition of DTBP to
25DEE/EtOH fuel blends
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Numerical modeling results showing the
advancement of combustion timing for fuel blends
of DTBP in both EtOH and 25DEE/EtOH
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
29
The addition of DTBP to 25DEE/EtOH causes the DEE
to burn earlier in the cycle, especially at later
combustion timings
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
30
The addition of DTBP to 25DEE/EtOH causes the DEE
to burn earlier in the cycle, especially at later
combustion timings
Experiments
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Outline

• Motivation
• Objectives
• Introduction/Background
• Experimental Procedure
• Numerical Modeling
• Results
• Conclusions

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
32
Conclusions

• The addition of DTBP did not elongate the
  combustion event, as defined by duration of heat
  release
• Addition of DTBP to fuel blends decreased the
  required intake temperature for a given CA50
• However, the addition of DTBP to fuel blends of
  DEE and EtOH did not make later combustion
  timings easier to obtain

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
33
Conclusions (contd)

• DTBP addition to mixtures of DEE and EtOH had a
  greater effect on combustion timing than when
  DTBP was added to EtOH alone
• The addition of DTBP to fuel mixtures enabled
  complete combustion of EtOH

SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
34
Conclusions (contd)

• 6. Numerical modeling suggests that the
  decomposition of DTBP and subsequent formation of
  acetone is exothermic and raises the mixture
  temperature slightly as the decomposition occurs

Suggests Thermal Effect more important than
possible Kinetic Effect
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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Questions?
SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005
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SAE International Fuels Lubricants Meeting
Rio De Janeiro, Brazil May 11-13, 2005