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4 Power Train Technologies for Reducing Load-Specific Fuel Consumption
Pages 51-90

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From page 51...
... participants in the multiagency, multicompany 21st Century Truck Partnership. The partnership's goals for engines are to achieve 50 percent thermal efficiency, while meeting 2010 DIESEL ENGINE TECHNOLOGIES emissions standards, by 2010 and to develop technologies Diesel engines use the high gas temperatures gener- to achieve 55 percent thermal efficiency by 2013 (NRC, ated by compression as the ignition source.
From page 52...
... A modconsumption by 1.1 to 3.6 percent.2 ulated two-stage system brings some of the benefits of each Almost all heavy-duty diesel engines sold in North of these two approaches. At low engine speeds it works as a America today use high-pressure loop EGR for control of two-stage system, delivering high-boost pressure despite the engine-out NOx levels.
From page 53...
... The benefits of electric turbocompound and an electric hybrid power train can be Most medium- and heavy-duty vehicle diesel engines additive. Energy and Environmenal Analyis7 has said that sold in the U.S.
From page 54...
... An example would be reaction occurs. In-cylinder technologies to control NOx forto develop heavy-duty diesel engines to run on 10W-30 oil mation in diesel engines are aimed at reducing the maximum instead of the current standard of 15W-40.
From page 55...
... According to information provided by Volvo,12 the fuel consumption of truck diesel engines is about 10 percent Thermal Insulation of Ports and Manifolds higher than for marine engines due to the size, weight, and Thermal insulation would reduce heat rejection to the engine coolant (from exhaust ports) or to the ambient air 12Tony Greszler, Volvo, private communication with Thomas Reinhart, (from manifolds)
From page 56...
... tential to improve fuel consumption by 6 percent, although this estimate is now several years old, and considerable improvement in fuel systems has already been made since Improved Work Extraction from Combustion Process 2002. Real-time combustion control with start of combus The compression ratio, expansion ratio, combustion tion sensors can also yield a fuel consumption reduction of 1 percent to 4 percent.14 chamber shape, injection spray pattern, injection pressure, injection timing, injection rate shaping, air/fuel mixing, peak cylinder pressure limit, air/fuel ratio, and EGR rate are all Engine Electronic Controller Calibration Management parameters that can be modified in an effort to reduce fuel consumption.
From page 57...
... Other Technologies GASOLINE ENGINE TECHNOLOGIES Other technologies for reducing the fuel consumption Gasoline engines operate with a premixed charge of fuel of diesel engines are discussed in the press almost every and air and use spark ignition to start the combustion process. day (e.g., Automotie News, Transport Topics, Diesel Fuel They are used in many Class 2b applications as well as Class News, DieselNet.com)
From page 58...
... The There is a fuel consumption penalty that comes with the process of throttling the intake airflow results in significant three-way catalyst used on gasoline engines. Because the pumping losses that are not present in diesel engines that air/fuel ratio must be maintained at stoichiometric all the operate using traditional diesel combustion.
From page 59...
... In the context used Compared to diesel engines, spark ignition engines are here it describes the degradation of energy during the combustion process generally simpler and less expensive, they have more effec- into a form that is less capable of being converted into work. Theoretically it is possible to convert all of the chemical energy contained within the fuel tive and lower cost exhaust emissions aftertreatment systems, completely into work.
From page 60...
... A variable compression ratio allows the engine to operate at Gasoline Direct Injection Engines different compression ratios for different loads in order to maximize the engine efficiency over the widest load range GDI engines refer to an embodiment in which the fuel possible. The combination of VVA and variable compres- injector is mounted so that the fuel is directly injected into the sion ratio keeps the engine operation closer to its maximum cylinder, as opposed to the more common port fuel injection,
From page 61...
... Based on esti- Turbocharging a gasoline engine is similar to turbochargmates from a light-duty study (NHTSA, 2009) , referenced ing a diesel engine in that it is motivated by the desire to by TIAX, a fuel consumption reduction with stoichiometric redirect energy that was leaving the engine in the exhaust direct injection engines relative to a port-injected engine gases back into the engine.
From page 62...
... In these demonstrations, fuel consumption levels comparable, or is being evaluated, including a downsized, turbocharged, superior to, that of conventional diesel engines have been direct injection, high-EGR, VVA engine, which is fueled achieved. The fundamental concept is one of optimizing the with either gasoline or gasoline and diesel (dual fuel)
From page 63...
... This is made possible by the compression ignition cycle of the diesel. The DIESEL ENGINES VERSUS GASOLINE ENGINES higher expansion ratio that comes with a higher compression ratio allows the diesel to extract more of the combustion Diesel engines offer significant fuel savings over gasoline energy before the exhaust valve opens near the end of the engines, when measured on a fuel consumption (gallon per power stroke.
From page 64...
... Both gasoline and diesel engines incorporate exhaust When the higher cost of diesel engines is added to the emissions control systems for hydrocarbons HCs, CO, and far higher cost of diesel emissions control aftertreatment, NOx. Gasoline engines also control evaporative emissions there is a powerful market incentive to move toward gasoline and diesel engines control PM.
From page 65...
... The 13- and 18-speed transmissions have tem gearing to the specific application. This process entails smaller-ratio steps, which allows the driver to better match selecting a top gear and rear axle ratio that matches typical the engine rpm to road conditions.
From page 66...
... Long-haul cycles on level ates in converter mode, a significant percentage of the input ground require little shifting and thus offer little potential for power from the engine is lost as heat in the torque converter. improvement, while duty cycles involving hills, congestion, The AT will operate with an open converter (lockup clutch and urban driving have much more potential for fuel savings, disengaged)
From page 67...
... It is not yet clear if any of these alternative transmission types will reach Rear Axle Ratio volume production. CVTs tend to have lower mechanical efficiency than MTs or AMTs, but they make up for this by The selection of rear axle ratio is one of the most imporallowing an optimum match between engine speed and road tant decisions in specifying a truck.
From page 68...
... The selection of axle ratio is the most important factor in determining driveline-related fuel con HYBRID POWER TRAINS sumption. A ratio that matches proper engine speed at cruise is critical.
From page 69...
... • Better driability. An electric machine reacts faster to The task of achieving fuel savings using a hybrid ar a throttle input than an ICE; furthermore, torque from chitecture depends on the type of power train selected as the ICE and the electric drive train can be added up well as the component sizes and technology, the vehicle whenever needed in certain configurations.
From page 70...
... Note that the ultracapacitors, hydraulic accumulators, and advanced flywheels have the highest power density among present-day storage systems, but their energy density is limited significantly. Hybrid Vehicle Architecture A number of different system architectures are being FIGURE 4-7 Series hybrid electric vehicle.
From page 71...
... If applications -- that is, duty cycles that have high regenerative electric machines are used at each of the wheels, instead braking requirements but relatively low energy requirements, of a single electric machine, torque vectoring is possible, such as refuse trucks and house-to-house delivery vehicles. improving vehicle stability.
From page 72...
... the need for high torque requirements for electric machines, In a parallel HEV the electric machine can assist the engine during startup and acceleration. Because the electric machine and the engine are both coupled directly to the wheels, they can share the power during acceleration.
From page 73...
... 4-12.eps MDV Fig bitmap bitmap system uses the kinetic energy of deceleration and braking to produce electricity, which is stored in the energy storage leading to an electric machine that is both larger and heavier system. than the corresponding machine in the pre-transmission con The most common configuration, called an input split, figuration.
From page 74...
... Odyne develops and manufactures plug-in hybrid Note that the two electric machines and the planetary gear electric drive systems for medium- and heavy-duty trucks. behave as a continuously variable transmission (CVT)
From page 75...
... hybrid electric vehicle (PHEV) , and full performance bat Li-ion developments with iron, manganese, and nickel tery electric vehicle (FPBEV)
From page 76...
... merits compared to batteries. They can be charged and discharged ery quickly, they have a longer life, and their Hybrid Electric Vehicles performance does not degrade appreciably with use.
From page 77...
... No Yes Yes Electric launch Yes Yes -- 12 mph Yes Refuse Haulers Applications Class 3-7 Refuse; Small delivery, Hybrid type: Parallel hybrid electric with and without delivery; refuse delivery soon shuttle ePTO. soon Fleet tests have demonstrated fuel consumption benefits SOURCE: TIAX (2009)
From page 78...
... Hybrid type: Parallel and dual-mode hybrid electric. A line-haul duty cycle limits the amount of energy that can The fuel consumption benefit for a Class 2b dual-mode be recovered from regenerative braking.
From page 79...
... The fuel savings also tend to HHDDT High Speed be lower with added mass, and this can be seen by the lower percentage benefit for the 100 percent load compared to the 50 percent load case. Figure 4-19 shows the fraction of the total braking energy that is recovered at the wheel -- meaning not including the driveline and electric machine losses involved in the chan- HHDDT Transient neling of that energy into the battery.
From page 80...
... In every other bar the hybrids are compared determining the following: type of hybrid technology to be with the conventional vehicle, hence the values are greater. used, level of hybridization and sizing of components, and When the breaks are removed from the highway cycle, power management strategy.
From page 81...
... . MDV Fig 4-21.eps bitmap FIGURE 4-22 Fuel consumption reduction due to stop removal, with respect to conventional vehicles without stops, and with respect to conventional vehicles with stops (50 percent load on theMDV Fig 4-22.eps right)
From page 82...
... . MDV Fig 4-23.eps bitmap FIGURE 4-24 Fuel savings of hybrid trucks with respect to conventional trucks as a function of maximum grade for various hill periods; MDV Fig 4-24.eps (left)
From page 83...
... Eaton Power Management in Hybrid Vehicles Corporation, in collaboration with the EPA, has developed a series hydraulic hybrid power system that combines a high- Power management is key in obtaining maximum perforefficiency diesel engine and a unique hydraulic propulsion mance and fuel savings from a hybrid vehicle. The objective system to replace the conventional drive train and transmis- of a power management algorithm in a hybrid vehicle is to sion (Eaton, 2009)
From page 84...
... The problem can be formulated as sequential decision making under un certainty in which an intelligent system (e.g., hybrid-electric TABLE 4-12 Fuel Economy and Exhaust Emissions vehicle, power train system) learns how to select control of Hybrid Electric Transit Bus with Various Control actions so as to reduce fuel consumption over time for any Strategies, Taipei City Bus Cycle different driving cycle (Malikopoulos, 2009)
From page 85...
... Table 4-14 compares the predicted fuel consumption of a conventional vehicle against a hybrid power management optimized using dynamic programming and rule-based algorithms. Crosscutting Issues and Future Outlook for Hybrids During the committee's discussions with manufacturers and suppliers, a number of overarching themes emerged with FIGURE 4-25 Dynamic programming process and rule extraction MDV Fig 4-25.eps respect to hybrid technology discussed.
From page 86...
... load-specific fuel consumption of diesel engines were identi • By narrowing the design window, hybrid systems fied. Some technologies are being used in 2010 by nearly all enable the engine to be optimized to deliver peak manufacturers (common rail fuel injection and selective cata fuel economy within a narrow operating band.
From page 87...
... Diesel engines can provide fuel consumption Finding 4-8. A wide range of hybrid electric and hydraulic advantages, compared to gasoline engines, of 6 to 24 percent depending on application, duty cycle, and baseline gasoline architectures have been demonstrated.
From page 88...
... SAE Paper 2009-01-1383. Pre High-Power Battery for Hybrid Electric Vehicles.
From page 89...
... 2009. Optimal use of E85 in a turbo of power management in an hybrid electric vehicle using dynamic pro- charged direct injection engine.


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