September 30, 2006
MEMS-Based Turbine Chip for Portable Power
|One component of the micro gas-turbine. Source: MIT|
MIT researchers are developing a gas-turbine engine the size of a quarter. The MIT micro-electro-mechanical systems (MEMS)-based micro turbine is a 1 cm diameter by 3 mm thick silicon heat engine designed to produce 10-20 W of electric power.
The resulting device could run 10 times longer than a battery of the same weight, with the potential to power laptops, cell phones, radios and other electronic devices.
|Cross-sectional drawing of earlier version of the MEMS turbine.|
The microengine is made of six stacked and bonded silicon wafers. Each wafer is a single crystal with its atoms perfectly aligned, so it is extremely strong. To achieve the necessary components, the wafers are individually prepared using an advanced etching process to eat away selected material. When the wafers are piled up, the surfaces and the spaces in between produce the needed features and functions.
Inside a tiny combustion chamber, fuel and air quickly mix and burn. Turbine blades, made of low-defect, high-strength microfabricated materials, spin at 20,000 revolutions per second—100 times faster than those in jet engines. A mini-generator produces 10 watts of power. A little compressor raises the pressure of air in preparation for combustion. And cooling (always a challenge in hot microdevices) appears manageable by sending the compression air around the outside of the combustor.
The team is now attempting to integrate the different components into a single functioning device.
This research was funded by the U.S. Army Research Laboratory.
(A hat-tip to Garrett!)
Study: Synthetic Fuels from Nuclear Hydrogen and Captured CO2 Viable
A study published earlier this year by researchers at MIT’s Center for Advanced Nuclear Energy Systems (CANES) concluded that producing synthetic transportation fuels from nuclear hydrogen and captured carbon dioxide would be technically viable.
Based on a reference year 2025 case, the report found that 43.1% of the CO2 projected to be emitted from coal plants could serve to produce the 6.6 billion barrels of ethanol required to displace gasoline use in the US. For the production of that much ethanol, there would need to be between 700 and 900 GWth (gigawatts thermal) of nuclear power to produce the needed hydrogen and energy for the synthesis of the fuel.
|Nuclear power requirements for transportation hydrogen. Click to enlarge. Source: General Atomics|
Estimates for the amount of nuclear power required to generate sufficient hydrogen to fuel a hydrogen fleet vary based on the efficiency of the vehicle fleet. General Atomics earlier this year estimated a required range of between 1,000 to 2,000 GWth to produce hydrogen for half of the current US fleet.
The study also concludes that replacing the entire world’s projected consumption of gasoline with 16.87 billion barrels of ethanol in 2025 would required the capture of 29.5% of the total emitted CO2 and a nuclear power requirement of between 1,800 and 2,300 GWth.
These numbers show that there is a very wide market for using nuclear power to aid in the production of alternative fuels to aid in the transition to the hydrogen economy. The large fraction of emitted CO2 that need to be captured shows that a benefit of this process would be to significantly decrease the total greenhouse gas emissions. A total cycle analysis reveals that the total reduction in CO2 emissions will be slightly more than 12%...A second benefit would be to decrease a nation’s dependence on imported petroleum.
The study also explored the production of methanol as a substitute.
Tne study incorporated a review of the literature on the use of nuclear power to produce hydrogen, as well as a review of possible nuclear reactor concepts. The researchers also concluded that nuclear power could be utilized in the production of oil from sand and shale.
Several nuclear cycles have potential application for the production of hydrogen, including High Temperature Steam Electrolysis, the Sulfur Iodine Cycle and UT-3. The report focuses on the High Temperature Steam Electrolysis option.
A number of possible new nuclear reactor concepts show potential in producing hydrogen, although many have drawbacks, according to the study.
Ultimately the report focuses on the High-Temperature Gas Cooled Reactor (HTGR), which uses helium coolant, and a modified version of the Advanced Gas Reactor (AGR) using supercritical CO2 as the coolant (S-AGR).
The reactor concepts selected for aiding production of oil from tar sands are the Advanced Candu Reactor (ACR-700), the Pebble Bed Modular Reactor (PBMR), and the Advanced Passive pressurized water reactor (AP600).
Separately, last week the Department of Energy announced that the Idaho National Laboratory (INL) will make awards valued at about $8 million to three companies to perform engineering studies and develop a pre-conceptual design to guide research on the Next Generation Nuclear Plant (NGNP).
The INL will issue a contract to Westinghouse Electric Company for the pre-conceptual design of the NGNP, and will later issue contracts to AREVA NP and General Atomics to perform complimentary engineering studies in the areas of technology and design tradeoffs, initial cost estimates and selected plant arrangements.
NGNP is a very high-temperature reactor concept capable of producing high temperature process heat suitable for the economical production of hydrogen, electricity and other energy sources. The NGNP research and development program is part of DOE’s Generation IV nuclear energy systems initiative aimed at developing next generation reactor technologies and is authorized by Congress in the Energy Policy Act of 2005.
“An Alternative to Gasoline: Synthetic Fuels from Nuclear Hydrogen and Captured CO2”; Middleton, B.D. and M.S. Kazimi; MIT-NES-TR-006, July 2006.
Nuclear Fission and Fusion (General Atomics)
September 29, 2006
From being a concept known mainly only by a close few even as recently as several years ago, plug-in hybrid electric vehicles (PHEV) are now being seen by an increasing number of transportation technologists and policy-makers as a near-term solution for reducing petroleum consumption and emissions of greenhouse gases.
The just-released Climate Change Technology Program Strategic Plan from the Department of Energy, for example, highlights plug-ins as one of the promising near-term solutions in the transportation sector. (Earlier post.)
The third day of this week’s California Air Resources Board ZEV Symposium was dedicated to PHEVs and the batteries that support them and all-electric vehicles (EVs).
This year marked the first year when I came to this conference and assumed that everyone already had fairly detailed technical knowledge of plug-in hybrid vehicles. It’s also the first year where I won’t spend the first third of a talk explaining what plug-ins are, and the next third why.—Dr. Mark Duvall, technology development manager for electric transportation & specialty vehicles, EPRI
There is a pressing need to do something new in the transportation industry specifically related to addressing our petroleum consumption...I feel that the PHEV is one of those potential options to help us address those issues...ideally one of the near-term solutions.—Tony Markel, senior engineer, NREL
The dramatic improvements in battery technology over the past few years are a major enabler and catalyst for this intensifying focus on PHEVs. Improvements in basic battery chemistry and manufacturing are not sufficient to unleash a flood of PHEVs on the market, however.
There are many ways to design a plug-in—and these have a direct effect on the size and type of battery applied in the vehicles. One of the challenges in the industry now is to determine the expectations of the different stakeholders, and then balance those objectives in such as a way as to give battery manufacturers a target to which they can work.
Charge-depleting vs. charge-sustaining modes. A plug-in battery operates in two modes: charge-depleting and charge-sustaining. Charge sustaining is the mode of operation for batteries in conventional hybrids. The state of charge may fluctuate, but on average it is maintained at a certain level while driving as it supports the engine. Discharge patterns consist of many, relatively shallow discharges.
In charge-depleting mode, the battery draws down its charge to power the vehicle. If the PHEV is operating in all-electric mode, the depletion will be fairly constant, except for bursts of regenerative charging from braking. If the PHEV is operating in blended mode, the state of charge may fluctuate but will, in general, decline until it reaches the point at which it switches over to charge-sustaining mode. Here the discharge patterns combine deep discharges with many more shallow discharges.
All-electric operation vs. blended mode operation. One of the fundamental questions designers must address is the operating strategy for the PHEV and its battery. The two basic options are to run the vehicle as an all-electric vehicle from startup, and then kick over to the engine when the battery reaches its minimum state of charge (SOC) threshold. (At which point the battery switches to charge-sustaining mode.) The other option is to run in blended mode, a charge-depleting strategy in which the engine supplements the battery up to the minimum SOC.
|Cycle life vs. state of charge swing. Click to enlarge. Source: NREL|
The State of Charge (SOC) Window. Regardless of whether the PHEV is designed for all-electric or blended mode, an important parameter for the battery is the SOC Window. The SOC window defines the swing: the upper and lower parameters for the state of charge of the battery, which, in turn can help define the required total kWh capacity of the battery pack for a given application.
Battery cycle life is a strong function of SOC swing. Battery SOC swing is a strong function of driving habits.—Tony Markel
In the absence of large test fleets of PHEVs on the road, simulation has become a tool for helping engineers figure out the likely technical dynamics of the PHEV market. NREL has used real world driving data from St. Louis in its modelling, as described by Markel at the ZEV Symposium.
Among the early findings and insights:
Consumers are likely to experience higher fuel economy than the rated value in daily driving, although a lower all-electric range than rated (due to driving patterns). In other words, as Markel said, “People would be very pleased with these vehicles.”
A point related to the above: vehicles designed with all-electric range likely to operate in a blended mode to meet driver demands.
Fuel savings relative to conventional vehicles are almost entirely distance-dependent. Savings relative to conventional HEVs are distance dependent up to PHEV distance then constant.
PHEVs that saved the most fuel relative to an HEV travel about 25 miles with speeds under 60 mph and light accelerations. PHEVs that saved the least fuel relative to the HEV in the 20-30 mile range had periods of 60+ mph highway driving and the accelerations were significantly more aggressive. (See chart below.)
Reduction of petroleum consumption is not tied to an all-electric range.
PHEV benefit is strongly related to distance and aggressiveness of real-world usage.
|Real world PHEV simulations of acceleration versus velocity. Click to enlarge. Source: NREL|
The decision of whether to support an all-electric or a blended strategy has a direct impact on the battery and motor combination—an all-electric strategy requires a more powerful battery and motor.
The blended strategy, by allowing the engine to switch on to provide additional power, can use a less powerful battery and motor combination. NREL’s simulation work so far finds that both strategies save about the same amount of petroleum.
The blended operation scenario potentially is less expensive, and may be a little more efficient too. We’ll have to see.—Tony Markel
Still, it all comes down to the capabilities of the battery. A special DOE meting on PHEVs in May of this year concluded, not surprisingly, that the success of the technology will be directly related to how good the batteries are.
It is our personal experience that the batteries are very good. That advanced batteries continue to provide remarkable performance improvements across the board. We are cautiously optimistic about the future of batteries.
What we have here is a technology with tremendous potential to improve the sustainability of the transportation sector.
What we know is that there are very promising current durability test data. But simple data. Deep cycling data. What we don’s have as much knowledge on is how those cells will perform specifically under a PHEV duty cycle. We have a large body of knowledge of battery capabilities...but that knowledge is very focused on battery capabilities for pure electric vehicles. There is a need for specific test data on PHEV requirements—and we need to evaluate the latest and most advanced chemistries.—Mark Duvall
In terms of chemistries, lithium-ion increasingly appears to be the current chemistry of choice for PHEVs. Beneath that umbrella, however, there are a large number of options in terms of materials, electrolytes and specific chemistries, all of which must be tailored to meet the particular application requirements.
|Baseline characteristics of batteries|
|Source: Dr. Andrew Burke, UC Davis ITS|
|Sodium Metal Chloride
Very broadly, one main distinction is between energy batteries and power batteries. An energy battery, simply, is designed to optimize the energy density; a power battery is designed to optimize the power density.
Tien Duong, vehicles technologies team lead at the Department of Energy’s FreedomCAR and Vehicle Technologies Program Office, noted during the ZEV Symposium that conventional lithium-ion batteries for power-assist HEVs “are about ready for commercialization.”
Duong said that the DOE’s main focus now is to support the development of novel materials for cathodes, anodes and electrolytes that promises greatly increased power and energy.
For PHEV batteries, I would not rule out NiMH, but I would say that lithium-ion batteries are technically feasible. There are no batteries specifically built for this application that I know of. I would think that there are strong synergies with the development of PHEV, HEV and EV [batteries]. One thing we don’t know is the impact of real world operations during charge-depleting mode.—Tien Duong
The new materials—as represented by A123Systems, but also by companies such as Altair Nanotechnologies, who was also present at the ZEV Symposium—offer designers more power or more energy depending upon the requirements.
A123Systems has a high volume battery product currently designed for power tools. (Hybrids are currently quite a small market for lithium-ion battery manufacturers, who have a much larger opportunity with laptops, cell phones and power tools. Power tools will outnumber hybrids by two or three times as measured by MWh, according to some analysis.)
A123Systems’s current product—the power tool cell—is somewhere in the middle of the range between power and energy. In other words, the A123Systems production cells put together by a PHEV conversion company such as Hybrids Plus in its Boulder PHEV demonstration aren’t really designed for PHEV operation. (Earlier post.)
Power is a function of the diffusion of the ions in the battery, notes Ric Fulop, one of the co-founders of A123Systems. The nature of the electrode materials and the electrolytes can all make a difference in terms of tilting the battery toward the power or the energy ends of the spectrum (or the area within the Ragone plot).
While that customization is possible from the battery manufacturers’ points of view, what they need are targets to hit: the specifications from the automakers.
And one of the best ways to achieve that—aside from the simulation work underway—is to get more trials out on the road that then feed back into shared project knowledge. Similar, for example, to what automakers and energy companies are doing for hydrogen in Europe. (Earlier post.)
So while the conversions of existing hybrids to plug-in operation might not represent the optimal in terms of battery technology or systems design, they do represent an extremely valuable potential source of real world data that needs to be fed back to battery makers and to automakers.
BMW Introduces Intelligent Alternator Control with Regenerative Braking; Reduces Fuel Consumption by About 4%
At the Paris Auto Show, BMW introduced a system it calls Intelligent Alternator Control (IAC) to generate electric power for a car’s on-board network exclusively in overrun and during braking—IAC thus also incorporates a system for regenerating brake energy.
The system is part of a larger BMW initiative to improve the overall efficiency of a vehicle by decreasing ancillary loads on the engine and recuperating more of the waste heat energy. (BMW is currently involved in one of several projects tackling the development of a thermoelectric waste heat recovery system targeted to deliver a 10% improvement in fuel economy. More on this below.)
Only about 25–30% of the energy contained in fuel is actually used for driving the vehicle. Most of the energy consumed is still converted into heat, although the fuel burnt also serves to generate electrical energy for the on-board network.
|Electric power requirements for mid-size and luxury cars. Source: DOE|
The on-board demand for power is also steadily increasing, even without factoring in traction support. Air conditioning, telecommunications, entertainment, as well as new components for enhanced safety and driving dynamics such as suspension management, Active Steering, engine management, and ABS all require electric power.
A mid-size car currently has an electric power requirement of about 3.5kW for all its systems. (See chart at right.) Hence, the generation of electricity for the car’s on-board network consumes an increasing share of the power generated by the engine.
With the IAC system, the alternator will operate primarily when the engine has no need for power—i.e., in overrun or during braking. The alternator remains passive while the car is under power, with needed electrical power provided by the battery.
The alternator becomes active when the engine switches to overrun or if the battery charge is insufficient.
For regenerative braking, a power converter fitted directly within the brake system converts the energy generated upon application of the brakes into electric power.
The battery is charged to only about 80% of its capacity whenever the engine is pulling the vehicle, always maintaining an adequate reserve for the consumption of energy at a standstill and for starting the vehicle. A higher charge level is generated only when the vehicle is in overrun or upon application of the brakes, that is in phases with a better energy balance.
With the number of charge cycles increasing thanks to these specific control functions, BMW combines Intelligent Alternator Control with AGM (absorbant glass mat) batteries able to handle a higher load than conventional lead/acid batteries.
BMW found that the on-demand generation of electrical energy helps to reduce fuel consumption in the EU homologation test by approximately 4%. The driver also has access to more engine power for acceleration and dynamic driving.
|BMW’s electric water pump.|
IAC is one effort to generate electrical energy in the car more efficiently, and use that energy for a wider range of purposes and functions. BMW is now using new electrical coolant pumps in its straight-six engines. The electrical pumps operating exactly—and only—when required, meaning that they develop their maximum output and performance only at high and very high speeds.
They remain passive immediately after the engine has been started, ensuring in this way that the engine is warmed up more quickly. This alone helps to reduce fuel consumption in the EU homologation test by approximately 2%.
|The waste heat recovery project envisions a heat exchanger in the exhaust line (middle of car) that then feeds a working fluid to the thermoelectric generator (TGM). Click to enlarge.|
Thermoelectric Waste Heat Recovery. BMW is a member of one of four teams engaged in a DOE-sponsored project on thermoelectric waste heat recovery. (Earlier post.) BMW’s team is lead by BSST, with Visteon, Marlow, Purdue, UC Santa Cruz, NREL, Teledyne and JPL also as contributors.
Another team is lead by GM and GE, with University of Michigan, University of South Florida, Oak Ridge National Laboratory, and RTI International as members.
The BMW team is using a 2006 BMW 530i as the target platform. The 3.0-liter engine is of the newest BMW generation, with characteristics representative of engines in the 2010 to 2015 timeframe.
The project, which began in 2005, has four phases. The teams are now in phase 2, in which they are building the subsystem elements, testing them independently, and then updating their system model.
Next year will see the integration and operation of the components as a system. Subsequent to that will be vehicle integration and testing at NREL.
Volvo Unveils C30; US-Bound in MY 2008 or Later
Volvo has unveiled its new C30, the smallest car in Volvo’s model range, at the Paris Auto Show. For the European market, Volvo will offer the C30 with a range of gasoline, flex-fuel and diesel engines that can deliver fuel consumption as low as 4.9 liters/100km (48 mpg US).
Volvo has announced that it will bring the car to the US market as well, although no earlier than the 2008 model year. The C30’s primary markets will be in Europe, with the largest markets being Italy, the UK, Germany and Spain. Volvo Cars estimates global sales of the C30 at 65,000 units annually. Pricing and volume expectations for the US-bound C30 have not yet been set.
The Volvo C30 can be fitted with four and five-cylinder gasoline and diesel engines, from 1.6 to 2.5 liters i displacement. All engines have four-valve technology and double overhead camshafts, which contribute to the quick response and good high-speed characteristics.
The most powerful gasoline engine (T5) is turbocharged, and has very high and even torque from low to high engine speeds (320 Nm from 1,500 to 4,800 rpm). For Sweden, Volvo is offering a 1.8-liter flex-fuel option.
|C30 Engine Options|
|T5 (2.5L)||In-line 5-cyl. turbo||162 (220)||320 (236)|
|2.4i||In-line 5||125 (170)||230 (170)|
|2.0||In-line 4||107 (145)||185 (137)|
|1.8||In-line 4||92 (125)||165 (122)|
|1.8 Flex-fuel||In-line 4||92 (125)||165 (122)|
|1.6||In-line 4||74 (100)||150 (111)|
|D5 (2.4L)||In-line 5-cyl. turbo||132 (180)||350 (258)|
|D5 (Belgium)||In-line 5 turbo||120 (163)||340 (251)|
|2.0D||In-line 4 turbo||100 (136)||320 (236)|
|1.6D||In-line 4 turbo||80 (109)||240 (177)|
All engines are transversely mounted in the engine bay, Turbo technology is used on the T5 engine and on all diesel engines to enhance performance.
A six-speed manual gearbox is used with the T5 and 2.0D engines and a five-speed Geartronic automatic gearbox is available with the five-cylinder gasoline and diesel engines. A particulate filter is available with all diesel engines.
Dynamic Stability and Traction Control (DTSC), is standard in most markets. Steering is electro-hydraulic (hydraulic for the 1.6-liter gasoline).
Toyota Introduces Eco Drive Indicator to Encourage Better Driving; Up to 4% Improvement in Fuel Economy
|Eco Drive Indicator. Click to enlarge.|
Beginning in October, Toyota Motor (TMC) will equip its new Japanese-market vehicle models using automatic transmissions with an Eco Drive Indicator, a feature intended to encourage environmentally considerate driving.
The indicator is designed to help reduce CO2 emissions through helping drivers increase their vehicles’ fuel efficiency through better operation.
Based on a comprehensive determination that takes into consideration such factors as accelerator use, engine and transmission efficiency and speed and rate of acceleration, the Eco Drive Indicator, located on the instrument panel, lights up when the vehicle is being operated in a fuel-efficient manner.
Toyota hopes this will raise driver awareness toward environmentally considerate driving and contribute to fuel economy.
Although results may vary depending on the level of traffic and conditions such as the frequency of starts from stop and of acceleration as well as distance driven, Toyota says that the Eco Drive Indicator can improve fuel efficiency by approximately 4%.
Toyota believes that sustainable mobility rests on three pillars: vehicles, the traffic environment and people. The Eco Drive Indicator represents one of TMC’s driver-awareness initiatives.
Energy and Auto Companies Outline Steps to Advance Hydrogen as a Transport Fuel in Europe
The energy companies Shell Hydrogen and Total France, along with automakers BMW, DaimlerChrysler, Ford Motor, GM, MAN Nutzfahrzeuge, and Volkswagen AG have issued a common position paper defining a joint approach to advance hydrogen as a fuel for road transport in Europe.
The companies have decided that a joint approach between energy companies and vehicle manufacturers is required to bridge the gap between the present individual demonstration activities and future commercially available hydrogen vehicles including the corresponding refueling infrastructure.
Each company is pursuing its own specific timelines, but the group has commonly identified key phases over the next decade, comprising continuous technology development and cost reduction, pre-commercial technology refinement and market preparation, with commercialization of hydrogen powered vehicles potentially starting around 2015.
A key priority is to concentrate efforts on a focused region for passenger cars, leveraging all resources in order to maximize learnings. Based on these requirements, the group sees these Lighthouse Projects initially rolling out in Berlin for cars and city buses, and in additional selected cities and regions for city buses.
All lessons learned will be shared across all regions, as will continuing education and outreach.
Taiwan Oil Firm Funding Coal-to-Liquids Study in Alaska
|The proposed Cook Inlet Coal-to-Liquids Project. Click to enlarge.|
The Alaska Commerce Journal reports that Chinese Petroleum Corp. (CPC) of Taiwan will kick in $1.5 million to co-fund a preliminary feasibility study for an 80,000-barrel-per-day coal-to-liquids fuels plant near the Beluga coal fields on the west side of Cook Inlet, in Southcentral Alaska.
CPC is working with the Alaska Industrial Development and Export Authority (AIDEA) and Alaska Natural Resources-to-Liquids, LLC (ANRTL), an Alaska Fischer-Tropsch firm.
The Beluga coal fields have an estimated 1 billion tons of coal resources. If built, the plant would have projected capital costs of $5 billion or more.
The Alaska project may involve Shell or Sasol as technology providers, according to Richard Peterson, president of ANRTL. Seventy-five percent of the projected product would be FT diesel fuel, 20 percent would be naphtha and 6 percent would be LPGs, or liquefied petroleum gases.
Carbon dioxide produced by the process would be captured and sequestered in the Cook inlet oil fields for enhanced oil recovery (EOR). Preliminary results from a US Department of Energy study indicate that a carbon dioxide, enhanced-oil-recovery project in Cook Inlet could result in an additional 300 million to 400 million barrels of oil from five producing fields.
Current oil production from the Cook inlet is 15,000 to 16,000 barrels per day. A CO2 EOR project could double the production and extend the lives of the mature fields by 20 to 25 years, according to the study.
September 28, 2006
More Details on the Lexus 600h L Hybrid Powertrain
|LS 600h L.|
At the Paris Auto Show, Lexus provided more details on the powertrain and performance of its luxury hybrid flagship, the LS 600h L, introduced earlier this year at the New York International Auto Show. (Earlier post.)
The Lexus Hybrid Drive in the LS 600h L combines a new 5.0-liter gasoline direct-injection V8 with large, high-output electric motors and a newly-designed battery pack to deliver more than 330 kW (442 hp) of total system power. Fuel consumption is rated at less than 9.5 liters/100km (more than 25 mpg US), and CO2 emissions are less than 220 g/km.
As with the Lexus RX and GS hybrid models, the LS 600h’s “600” suffix refers not to the cubic capacity of the engine but to a power output comparable to that of a 6.0-liter V-12 normally-aspirated engine.
Engine. The longitudinally-mounted 5.0-liter V8 gasoline engine is derived from the 4.6-liter powerplant in the LS 460. To reduce the overall weight of the engine, the cylinder block is die-cast from a lightweight, high-strength aluminium alloy. The block structure and rib reinforcement design have been finalized through the incorporation of cylinder combustion pressure data to minimize both vibration and noise. The engine head cover is also constructed in a lightweight magnesium alloy.
The new V8 features a D-4s (direct injection 4-stroke superior version) stoichiometric direct injection system, the world’s only automotive injection system to adopt two injectors per cylinder—one injector installed in the combustion chamber and a second mounted in the intake port.
The D-4s system’s port injectors employ 2 holes to inject fuel at a maximum pressure of 4 bar, while the in-cylinder injectors feature twin, 0.52 x 0. 3 mm rectangular slits producing a double fan injection pattern to effect the most homogeneous possible air/fuel mix.
Under cold start conditions, D-4s employs port injection during intake and direct injection during compression, producing a lean air/fuel mixture of 15-16:1. By concentrating the richer mixture around the spark plug it is possible to raise the combustion temperature, contributing to a quicker warm up of the Lexus thin-wall catalysts.
At idle, the engine runs on direct injection alone, due to its higher efficiency. In addition, and unique to the LS 600h and GS 450h, the electronic management maintains engine revolutions at an ideal speed to improve warm-up.
When the engine is running under a low- to medium-load at lower speeds, both direct and port injection systems are used during the intake stroke. This creates an homogeneous, 4.5: stoichiometric air/fuel ratio to stabilize combustion, improve fuel efficiency and reduce emissions.
When the engine is running under heavy loads, the direct injection system alone is employed. This achieves an intake cooling effect by injecting fuel directly into the combustion chamber, which improves the efficiency of each charge. It also allows for a higher engine compression ratio of 11.8:1, reducing pre-ignition tendencies and improving engine output and performance. Once again, a 12-15:1 stoichiometric air/fuel ratio is effected during the intake stroke.
D-4s substantially reduces combustion fluctuations in comparison to any conventional, direct or port injection system. D-4s realizes optimum engine efficiency throughout the power band and improving torque by 7.5% across the rev range, while minimizing fuel consumption and emissions.
The engine is also equipped with Lexus’ Dual VVT-i. This optimized, low-pressure loss, variable intake and exhaust valve timing system incorporates VVT-iE, the world’s first electric motor-driven intake camshaft, which operates across the full engine revolution and temperature spectrum.
Hydraulic VVT cannot operate below 1,000 rpm or during engine warmup. However, the Electric Motor Driven VVT system will operate across the full engine revolution and temperature spectrum, with a cam response speed of 50 degrees per second towards the lag phase and 50 degrees per second towards the advance phase.
Due to cam phase shifts when the engine stops, it is difficult to halt the cam at the optimum position for engine re-start using the electric motor alone. For that Lexus engineers have developed a mechanism employing frictional resistance and speed reduction gearing to hold the cam phase in the ideal position for engine start-up.
The new V8 further features a semi-dual exhaust manifold that reduces interference in the flow of exhaust gases, further improving output and combustion efficiency.
Motor and Electronics. The LS 600h Lexus Hybrid Drive employs a three-phase, permanent magnet AC synchronous motor, operating on a 650-Volt current, delivering more than 60 kW.
A change in the magnet distribution enhances operating quietness. Coiling the magnetic alternate, and hence holding the magnetic force, results in a smoother, more stable motor rotation.
The hybrid drive also consists of a generator; a high-performance NiMH battery; a power split device which combines and reallocates power from the engine, electric motor and generator according to operational requirements; and a Power Control Unit (PCU) to govern the high speed interaction of the system components.
All-wheel drive and transmission. The LS 600h features a new, mechanical, all-wheel drive system and a newly developed, dual-stage, electronically controlled continuously variable transmission.
The all-wheel drive transmission relies on a 3-differential configuration and a propeller shaft, coupled directly to the hybrid transmission.A permanently engaged mechanical transfer system distributes drive power with a ratio of 40% to the front wheels and 60% to the rear.
A center limited-slip differential optimizes grip, traction and vehicle handling on all-road conditions. Traction and grip characteristics are further enhanced by the vehicle’s advanced stability control system, Vehicle Dynamics Integrated Management.
As in the GS 450h, the Lexus Hybrid Drive’s electric motor, generator, power split planetary gear mechanism and motor-speed reduction gearing are all housed in one lightweight, highly compact transmission casing.
The combined installation of these components within a single compact casing is fundamental to the successful installation of Lexus’ hybrid drive system in a longitudinal, front-engine sedan platform.
The Lexus Hybrid Drive ECU selectively controls the rpm of the engine and electric motor, and the E-CVT (Electric Continuously Variable Transmission) simulates a continuous variation of the transmission’s current ratio. Similar to that of the GS 450h, the two-stage motor speed reduction gearing generates maximum low-gear torque for significantly enhanced acceleration, as well as extended high-gear performance for high speed cruising with improved fuel efficiency.
Chrysler Introduces 2.0-Liter Turbodiesel Concept at Paris Show
|The Dodge Avenger concept car.|
Chrysler took the wraps off its Dodge Avenger concept car at the Paris Auto Show this week. The Avenger uses a 2.0-liter turbo diesel engine and offers a lower rear diffuser to reduce vehicle drag and improve fuel efficiency.
If the D-segment (mid-size) vehicle goes into production, the Dodge Avenger will be sold in markets outside North America.
Avenger brings Dodge brand American muscle car heritage into the global mid-size car segment. It does for the global D-segment what Caliber has done in the global C-segment—it offers a unique alternative to the competition.—Trevor Creed, Senior Vice President–Design, Chrysler Group
On the D-Segment production side, Chrysler introduced the new Chrysler Sebring with a choice of four engines in Europe. (Earlier post.) Standard is a 2.0-liter gasoline World Engine with dual Variable Valve Timing (VVT), and available are a 2.4-liter gasoline World Engine with dual VVT and a 2.0-liter turbo diesel engine. Available at a later stage in Europe will be an enhanced 2.7-liter V-6 gasoline engine.
The diesel engine will deliver an estimated 140 horsepower (103 kW) and 236 lb-ft (320 Nm) of torque.
The new Chrysler Sebring is the first Chrysler Group D-segment production vehicle to offer a diesel powertrain—and right-hand-drive availability. The new Sebring is available outside North America in two models, Sebring Touring and Sebring Limited, and will begin to arrive to international dealerships in the first half of 2007.