Transcript Ultra-High Efficiency Engines Powered by Alcohol

Cleaner, More Efficient Methanol Engines
For Sustainable Transportation*
Leslie Bromberg** and Daniel Cohn#
**MIT Plasma Science and Fusion Center and Sloan Automotive
Laboratory
#MIT Energy Initiative
Methanol Engine Advancement for Sustainable Transportation
Reykjavik, Iceland
February 23-24, 2016
* Supported by the Arthur Samberg Energy Innovation Fund, by US Department of Energy, and
by Fuel Freedom Foundation
ENGINES THAT OPTIMIZE ADVANTAGES OF METHANOL
• Sustainable lower cost
– Fuel savings from higher efficiency engines enabled by
special properties of methanol
– Lower cost engines as alternative to diesel engines for
clean heavy duty trucks
• Potential for reduced greenhouse gas
emissions
• Reduced urban air pollution (large reduction
relative to present diesel engines in China)
Increased Efficiency Using Methanol
1. Limited availability of methanol:
– Octane-on-demand for engines that are mainly
powered by gasoline
– can provide around 30% greater efficiency than
naturally aspirated gasoline engine
• comparable to diesel!!
2. Engines entirely powered by methanol
– can provide up to 50% greater efficiency than a
naturally aspirated gasoline engine
Octane-On-Demand Using Methanol
Dual Fuel
On-board Separation
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Separate tanks of regular
gasoline and high octane fuel
High octane fuel acquired by
refueling the second tank
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Gasoline
tank - PFI
A separate tank of a high octane
fuel
High octane fuel acquired by a
membrane separation system
Separation process requires
additional power/ takes time
M100
tank-DI
Direct injection increases effective octane of methanol
Octane On-Demand Using Methanol
• Small amount of methanol introduced into the cylinder increases the
efficiency of a much larger amount of gasoline by preventing knock at high
load
– higher compression ratio and downsizing
– 1 gallon of methanol replaces 4 gallons of gasoline
• Methanol supplied by
– separate tank, externally filled
– by onboard separation of methanol/gasoline blends
• On-demand octane boosting can increase efficiency by around 30%
relative to aspirated gasoline engines; this efficiency gain is comparable to
that of a diesel engine
• Greenhouse gas can be reduced both by the increase in efficiency gain and
by the use of renewable methanol
Downsizing vs. Compression ratio
• ECOTEC LNF 2 liter GM engine
– Direct injection
– Turbocharged
• Variable fuels
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Ethanol blends
PRF
Toluene
Methanol
Hydrous alcohol
Variable octane fuel through
onboard fuel blending (OOD:
Octane-On-Demand)
– On-board fuel separation (OBS)
Y. Jo, L. Bromberg, J.B. Heywood , Optimal Use of Ethanol in Dual Fuel Applications: Effects of Engine
Downsizing, Spark Retard, and Compression Ratio on Fuel Economy, SAE paper 2016-10-0786. Supported by
US Department of Energy.
Engine Octane Requirement
US HWFET
1.2 liter
engine in a
Camry
Efficiency vs Compression ratio
T.G. Leone, J.E. Anderson,R.S. Davis, et al., The Effect of Compression Ratio, Fuel Octane Rating, and Ethanol Content on
Spark-Ignition Engine Efficiency, Environ. Sci. Technol. 2015, 49, 10778−10789; DOI: 10.1021/acs.est.5b01420
Compression ratio vs downsizing
Average engine brake efficiency vs. engine displaced volume for a Camry
running on UDDS cycle. Spark timings were kept at conventional fuel MBT
timing.
Downsizing impact on Fuel Efficiency
for Various Driving Cycles
The average brake efficiency vs. engine displaced volume for three standard U.S.
driving cycles run with a Camry. Rc = 11.5:1, MBT timing.
Impact of Spark Retard on Fuel Efficiency
Average engine brake efficiency vs. engine displaced volume for UDDS (blue) and US06 (red)
cycles run with a Camry. Dashed-lines represent the case with up to 5 CAD retard allowed, and
dotted-lines represent the case with up to 10 CAD retard allowed. Rc = 11.5:1.
Methanol eliminates knock limit
Ultimate possibilities?
• Compression ratio
• Impact of increasing
compression ratio
decreases above ~ 11.5
– Peak pressure continues
to increase
• Downsizing
• Efficiency improvement
up to about 300 cm3
per cylinder (?)
• ~ 1 liter engine, 3
cylinders, may be
practical limit
Future vehicles:
Super Efficient Dedicated Methanol Engines
Efficiency gain relative to
conventional gasoline engine
50%Exhaust heat recovery
by methanol reforming
40%-
low load dilute operation
30%-
Diesel Engine
Additional turbocharging and
downsizing( high strength block)
20%Gasoline Turbo
DI Engine
Turbocharged, downsized engine
10%High compression ratio
Removal of knock limit
(higher octane)
Less
Throttling
Exhaust heat
recovery
Rankine cycles enabled by alcohols
Turbine recovery
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•
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Conventional Organic Coolant Rankine
cycle potential limited by temperature,
disposal of waste heat
For gasoline or other liquid hydrocarbons,
potential energy recovery by using fuel
very limited
For alcohols, potential for energy
recovery increased by reforming alcohol
into hydrogen rich gas
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–
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Use fuel as Rankine cycle coolant
Low temperature , endothermic reformation
Methanol and hydrous ethanol can
recover > 80% of the exhaust heat
Removes also some heat from the cooling
water, easing the radiator design
Can use turbine or energy recovery
Reformer-Enhanced Methanol Engines
Reformer + lean burn engine
Car – Light truck
Short haul truck
Alcohol Rankine Cycle
Long haul truck
50% more efficient than
PFI gasoline engine
20% more efficient than
diesel engine
20-25% more efficient than
diesel engine
$1500-$2500 extra vehicle
cost
$8000 lower cost than
diesel vehicle
Relative to diesel vehicle:
lower vehicle cost if
recovered energy used in
engine; $10K additional
cost if turbine is used
$300- $500/yr fuel cost
savings
$800-$1200/yr fuel cost
savings
$6000/yr fuel cost savings
Preliminary Illustrative incremental vehicle cost and fuel cost savings
Fuel cost savings due to efficiency gain only. Assumed alcohol cost is $2.2/gge, same as gasoline
NON-dedicated Alcohol engines
Flexible-Fuel Engine (Gasoline Operation
with Alcohol Boost From Second Tank)
Summary
• Octane-on-demand can be very effective way for small amount of
methanol to increase efficiency of gasoline engines
– Comparable to diesel!!!
• Super efficient engines powered entirely or nearly entirely by
methanol could potentially provide the cost savings needed for
large scale use of an alternative liquid fuel
– efficiency could approach that of a fuel cell
– Lower cost of ownership would be due to increased efficiency of operation, as
well as less expensive power plant
– not because of less expensive fuels
• These engines could be operated in a flexible fuel mode where they
are powered with gasoline and a small amount of alcohol, but with
reduced efficiency gain
– No exhaust energy recovery
Extra Slides
US Methanol/E85/gasoline prices
Use of methanol as Entire or Main
Fuel in Present Fleet
• What can be achieved in present vehicles or
slightly modified present vehicles?
Leslie Bromberg and Daniel R. Cohn
August 11, 2015, work funded by Fuel Freedom Foundation
Renewable Methanol
• CO2 and renewable electricity
• Biomass sources
Natural gas
Reformer
Synthesis gas
BIOMASS
Catalyst
methanol
DME
diesel
ethanol gasoline
• Methanol is lowest cost and lowest greenhouse gas fuel
from methane
• Methanol is lowest cost and lowest greenhouse gas fuel
that is thermochemically produced from biomass
Compression ratio vs Downsizing
Average engine brake efficiency vs. engine displaced volume for a Camry
running on US06 cycle. Spark timings were kept at conventional fuel MBT
timing.
Alcohol Rankine cycles
Engine recovery
• 20-25% fuel efficiency
increase (at load)
• Energy recovery through
turbine or injection into
engine
– Turbogenerators ~ 1$/W
– Cost for engine recovery
minimal, but less efficient
Preliminary design of onboard design
for reformer
Characteristics of a stoichiometric engine at a few specified points in the ESC
(European heavy duty engine Stationary Cycle) and potential for energy recovery for a
class 7-8 truck (heavy duty truck)
Heat Exchanger Technology
• Reformer enabled by new compact heat exchanger
• Use of metallic foams for improved heat transfer to
gas
– Microchannel approach developes boundary layers (due to
laminar flow) that limit heat transfer
• Break microchannels to prevent boundary layers
• Continuing to break microchannels, end up with open cell porous
geometry
– Open cell porous metals commercially available
Cryogenic heat exchanger
current lead for superconducting applications
Methanol steam reforming
1:1.3 MeOH/H2O molar:
Fig. 4. Methanol conversion by impregnation method in MSR over
catalytic CuZn foam calcined at different temperatures.
H. Chen, H. Yu, Y. Tang et al., Assessment and
optimization of the mass-transfer limitation in a
metal foam methanol microreformer, Applied
Catalysis A: General 337 (2008) 155–162
Fig. 6. Methanol conversion in MR over catalytic CuZn foam by
impregnation method with different fractions of Al2O3 binder.