Assessment of Fuel Economy Technologies for Light-Duty Vehicles (2011) / Chapter Skim
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5 Compression-Ignition Diesel Engines
5 Compression-Ignition Diesel Engines
Pages 61-83
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From page 61... ...
The CI diesel thermo Fuel economy technologies considered in the NRC's dynamic cycle efficiency advantage over the more common (2002) earlier report on fuel economy did not include SI gasoline engine stems from three major factors: the CI's diesel-powered CI engines because the costs and emission use of lean mixtures, its lack of throttling of the intake control systems to meet upcoming nitrogen oxides (NO x)
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From page 62... ...
• Reducing engine friction (e.g., reduced piston skirt At higher engine speeds, when the air flow rates have friction) , and increased and the smaller turbo does not have sufficient flow • Reducing accessory loads (e.g., electric water pump, capacity, air flow rates are sufficient to generate high intake reduced fuel pump loads by avoiding fuel recirculation, pressures when the exhaust flow is directed through the larger modulated oil pump)
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From page 63... ...
friction. Connecting rod, camshaft, and main bearing friction is hydrodynamic, thus coming primarily from lubricating oil Exhaust Emissions Control of CI Diesel Engines shear processes.
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From page 64... ...
As a result, the overall Technologies being developed to support this move in choice between investing in SI gasoline engine technologies combustion technology toward premixed low-temperature to reduce the SI gasoline fleet FC on the one hand and replac- combustion are cylinder-pressure-based closed-loop control; ing some SI gasoline engines with CI diesel engines on the piezo-actuated higher-pressure fuel injectors; two-stage other hand will rest on the total cost for emissions-compliant turbocharger systems; and combinations of high- and lowCI diesel engines and their remaining FC advantage after pressure EGR systems. emissions control measures are implemented.
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From page 65... ...
Hot inlet mixtures negate some of the potential of lowering NOx and Exhaust Aftertreatment Technologies PM formation through lower mixture temperatures. Therefore, high EGR levels require larger and more effective EGR HC/CO Control coolers.
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From page 66... ...
In addition, there is of the catalyst surface coating, reduces the NOx back to N2. a second fuel economy decrement caused by the additional Accordingly, application of an NSC to any engine that fuel required to regenerate the filter by oxidizing retained has a lean exhaust stream like diesel engines requires that particulates.
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From page 67... ...
SCR works by having exhaust aftertreatment system is illustrated in Figure 5.3. ammonia in the exhaust stream in front of a copper-zeolite or iron-zeolite SCR catalyst.
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From page 68... ...
might be lower sidered, the average reduction in CO2 emissions was about than those for SCR systems for those same engines, but NOx 23 percent and the corresponding average reduction in FC conversion efficiencies might not be high enough to meet the was 33 percent when the baseline 2007 model year SI power standards. Thus, the engine displacement above which an trains were replaced with CI power trains utilizing DCT6, OEM would choose SCR rather than the NSC is not simply EACC, HEA, and EPS.
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From page 69... ...
It should be noted that part of the volumetric FC benefit The 2007 model-year baseline vehicles were equipped of CI diesel engines stems from the differences in volumetric with 4- and 5-speed automatic transmissions. As noted energy content between gasoline and diesel fuels.
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From page 70... ...
market have concerns over the sealight-duty CI diesel passenger cars are widespread and about sonal and regional variability of diesel fuel as well as the half the new cars are powered by diesel engines, the diesel enforcement of fuel quality. fuel is specified by the EN590 standard.
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From page 71... ...
For smaller veof the DCT6 transmissions are estimated at 1 to 2 percent for hicles with manual transmissions and engine displacements downspeeding the engine by increasing the number of dis- less than 1.5 L, cost constraints are likely to reduce the extent crete speed ratios beyond six. The increased number of ratios of downsizing and the potential would be about 6 percent for allows keeping the average engine speed lower while still engine alone and 7 percent for vehicle due to elimination maintaining equal performance, which is why this approach of not only the gain from automatic transmission efficiency TABLE 5.2 Estimated Fuel Consumption Reduction Potential for Advanced-Level CI Power Trains Compared to BaseLevel CI Power Trains Item Average Reduction (%)
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From page 72... ...
paths. The first path is the introduction of the advanced-level Application of CI technology into the NA market to technologies listed in Table 5.2 into post-2009 vehicles that reduce fuel consumption involves two steps.
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From page 73... ...
Third, fuel prices must increase technologies summarized in Table 5.2 is their introduc - from late 2009 levels but without significant negative price tion simultaneously with new CI power trains in the period differential between gasoline and diesel in order to provide 2014-2020. These advanced-level versions will be required potential customers with sufficient incentive to offset the for market competitiveness for these new vehicles since additional prices that must be charged for CI engines.
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From page 74... ...
Martec reviewed the 2008) from which the fuel consumption reduction values resultant cost tables with both the OEMs and the suppliers to in Table 5.1 were determined had base-level technology reach consensus.
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From page 75... ...
This choice the downsized 1.6-L engine were not reduced from the 2.0-L could be changed depending on success in meeting LEV III sizes since the 1.6-L engine must produce the same power TABLE 5.4 Committee's Estimates of Incremental Cost of CI Diesel Engine over a Baseline SI Gasoline Engine for Replac ing SI 2.4-L MPFI DOHC Four-Valve Engines in Midsize Sedans (e.g., Malibu, Accord) with Base-Level 2.0-L I4 CI Engines Estimated Cost vs.
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From page 76... ...
226 HP/LP EGR system to suppress NOx at light and heavy loads; includes hot side and cold side electronic rotary diesel EGR valves plus EGR cooler and all plumbing Emissions control system including the following functionality: DOC, CDPF, selective catalytic reduction (SCR) , urea 964 dosing system ($363)
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From page 77... ...
. Therefore, for the purpose of this particulate filters are silicon carbide (Si-C)
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From page 78... ...
. The fuel pump for the Martec cost estimates were based on November 2007 com gasoline system is actually replaced by the low-pressure modity prices for the precious metals used in the exhaust supply pump for the CI fuel system, which is very similar aftertreatment system washcoats.
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From page 79... ...
Again, no informacylinder-pressure sensing system is beneficial for minimiz- tion was provided about volume, PGM loading, or PGM cost ing engine fuel consumption and emissions when different basis for the EEA estimate. The present study assumed $52 fuels of widely different cetane ratings are encountered in the for the monolith and housing and $139 for the PGM wash
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From page 80... ...
sponding value for the V6 CI engine from the present study was $3,174. A significant portion of the $559 difference Summary of Total SI to CI Power Train Replacement Cost between the NHTSA estimates and those of the present work Estimates is due to the inclusion in the Martec, and presumably also in the NHTSA, estimates of two-stage turbocharger systems The total estimated costs to replace 2007 model-year SI that for the present study correspond to advanced-level en- power trains with base-level and advanced-level CI power gine technology, as described in the section "Engine Sizing trains for the example midsize sedan and midsize SUV Methodology." As noted above, the costs from the present vehicles indicated in Tables 5.4 and 5.5 are summarized in work that were used in Table 5.7 were those for the base- Table 5.9.
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From page 81... ...
Finding 5.2: Replacing 2007 model year MPFI SI gaso- Finding 5.3: The characteristics of CI diesel engines that enline power trains with base-level CI diesel engines with able their low fuel consumption apply over the entire vehicle advanced dual-clutch (automated manual) transmissions operating range from city driving to highway driving, hill
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From page 82... ...
2008/2009. Diesel and hybrid cost analysis: EEA versus range (e.g., hybrid power trains reduce fuel consumption Martec, presentation made to NRC Committee, February 25, 2008, primarily in city cycle/city driving)
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From page 83... ...
83 COMPRESSION-IGNITION DIESEL ENGINES ANNEX Table 5.A.1 shows the data used in Figure 5.4 for the percentage reduction of fuel consumption in 2009 European vehicle platforms offered with both SI gasoline engines and CI diesel engines in configurations that provide virtually equal performance (i.e., 0 to 100 km/h acceleration times within 5 percent between SI and CI)
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