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发帖数: 555 | 1 In a case of an old idea gaining new legs, Achates Power says it expects the
first commercial use of its unique two-stroke, opposed-piston design to
occur by 2020, following an initial in-vehicle demonstration in early 2018.
It’s based on a design that’s well over 100 years old.
Achates, aiming to power both heavy-duty trucking and passenger vehicles,
won’t say which will be the first to hit the streets using its technology,
but much of the company’s development work so far appears tilted toward
diesel truck engines.
Commercial trucking is the sweet spot of the market for Achates, chief
executive David Johnson, a former Navistar executive, told Trucks.com during
a recent tour of the company’s facilities in San Diego.
Truck operators are extremely fuel conscious and the Achates’ opposed-
piston, or OP, engine can deliver up to 30-percent better fuel economy than
existing internal combustion engines, he said. While the engine also
improves on emissions, Johnson does not consider that a major selling point.
The trucking industry does care about emissions, but is “laser-focused on
simultaneously increasing fuel economy” and reducing other costs, said
Michael Held, an automotive industry analyst at the global consulting firm
AlixPartners.
“Trucking companies will line up” to buy a new type of engine if the
manufacturer can successfully validate its savings and reliability and
durability claims, Held said.
Achates’ diesel design can achieve the 55 percent engine efficiency goal –
also called brake thermal efficiency, or BTE – of the five-year, $160-
milliion SuperTruck II development program without the use of expensive add-
on technologies, said Fabien Redon, Achates’ vice president for technology
development.
Unlike two-stroke engines of old, the Achates design eliminates the need to
mix oil or other lubricants with the fuel, delivering far cleaner emissions,
said Redon, a former Detroit Diesel and General Motors diesel development
engineer.
In heavy-duty diesel applications, Redon told Trucks.com, the Achates design
results in a 50 percent to 90 percent reduction in NOx emissions, a smog-
and ozone-causing product of fuel combustion.
And while most alternatives to conventional internal combustion engines are
more costly, dampening trucking operators’ enthusiasm, the Achates design
results in an engine that costs about 10 percent less than a conventional
model, said Redon.
The Achates engine is based on the Atkinson-cycle engine developed by James
Atkinson in 1882. He built three versions of the design that featured a
short compression stroke and a longer expansion stroke, which were meant to
provide efficiency at the expense of power density. The first application
was called the “differential engine” and used opposed-pistons.
The Achates OP design places two pistons in a single cylinder, each
connected to its own crankshaft. The design eliminates cylinder heads and
valve trains. Slashing the number of moving parts cuts costs and
significantly reduces heat losses and friction in the operating engine.
The engine is built using many of the same components and manufacturing
techniques as a conventional internal combustion engine. That means
mechanics don’t need significant retraining to work on it and manufacturers
won’t need to do as much re-tooling to build it, said Bill Van Amburg,
senior vice president and head of trucking programs for CalStart, a Pasadena
-based consortium devoted to developing and promoting clean transportation
technologies.
The Achates engine “can represent the replacement and future life of
internal combustion,” Van Amburg said.
Achates’ engines run from a small, twin-cylinder (four pistons) 1.8-liter
gasoline model suitable for passenger cars and small crossover SUVs to a 9.8
-liter, three-cylinder (six pistons) diesel Class 8 engine rated at 450
horsepower and 1,550 pound-feet of torque.
The engines can work with electric motors in hybrid cars and trucks, serve
as range extending generators for electric vehicles and be scaled larger or
smaller than current designs, Johnson said. They also can be configured to
work with various biofuels and natural gas, he said.
Achates opposed-piston engine cutaway
San Diego-based Achates, founded in 2004 by James Lemke, a physicist and
self-described serial entrepreneur, is working with a dozen clients in the
commercial and passenger vehicle segments. They represent about half of the
world’s production of vehicle engines, Johnson said.
The company isn’t a manufacturer, but a developer that provides engineering
and development services to its clients, customizing its engine design for
their needs.
While the identities of most Achates clients are confidential, the company
has announced a partnership with truck-engine builder Cummins Inc. on a
military combat vehicle engine program and is working with automotive parts,
components and services supplier Delphi Inc. and the Argonne National Lab
on development of a light-duty pickup truck engine.
The company is not yet making profits, but revenue from its engineering
services had doubled in the past few years to “about $20 million” for 2016
, Johnson said.
The company has attracted more than $150 million in investment, said Johnson
, and has grown to about 100 employees. Achates’ main facility is a four-
building complex in a modest industrial park in San Diego and it recently
opened a small engineering and marketing office in Farmington Hills, Mich.
Achates light-duty development engines will be available for automakers.
Achates and the OPE. Achates Power has spent 13 years improving the opposed-
piston engine, a historically efficient engine originally developed in the
late 1800s. The Achates Power Opposed-Piston Engine features two pistons per
cylinder, working in opposite reciprocating action. The Opposed-Piston
Engine does not need cylinder heads, which are a major contributor to heat
losses in conventional engines. Ports in the cylinder walls replace the
complex poppet valves and friction-creating valve trains of conventional
engines.
http://bioage.typepad.com/.a/6a00d8341c4fbe53ef01b8d2524d8a970c-800wi
Opposed piston engines offer a number of fundamental engine efficiency
advantages compared to four-strokes:
Lower heat transfer. Heat transfer is proportional to the combustion chamber
surface area-to-volume ratio; the smaller the ratio, the better. One of the
main reasons larger displacement engines are more efficient than smaller
ones is the reduction in area-to-volume ratio.
Heattransfer
At equivalent displacement, the OP engine has more than a 30% lower area-to-
volume ratio. Looked at another way, the OP engine surface area-to-volume
ratio is equivalent to that of a 4-stroke engine of more than twice the
displacement. E.g., the area-to-volume ratio of a 6-liter OP engine is
equivalent to that of a 15-liter conventional diesel.
Leaner combustion. The opposed-piston two-strok (OP2S) engine has a
combustion event at every revolution in each cylinder. It features a larger
cylinder volume for a given fuel quantity, leading to leaner combustion at
the same boost level, which leads to a higher ratio of specific heat. A
higher ratio of specific heat leads to higher ideal engine efficiency.
Optimally phased and faster combustion at equivalent pressure rise rate. The
larger volume also enables shorter combustion duration while preserving the
maximum pressure rise rate. Shorter combustion and lower heat transfer
results in a more advanced combustion phasing.
Lower pumping work. Air pumping is decoupled from the engine cycle. The OP
engine ports are less restrictive than poppet valves.
Ope1
A very significant factor in meeting emissions requirements is the ability
to light off the aftertreatment system as soon as possible. Achates has
demonstrated the ability to achieve exceptionally high exhaust gas
temperatures at idle—much beyond what can be done with equivalent 4-stroke
engines. This enables the earlier light-off of the aftertreatment, therefore
resulting in lower emissions over the cycle.
The intake ports at one end of the cylinder and exhaust ports at the other
are opened by the piston motion and enable efficient uniflow air scavenging.
The two-stroke, compression ignition engine has been engineered to achieve
superior thermal efficiency by the virtue of its lower heat losses, higher
expansion ratio, lean combustion and reduced pumping losses.
Achates Power single cylinder with airflow
Illustration of the Achates cylinder, showing airflow through the ports—
intake at bottom, exhaust at top. The shape of the intake ports is critical,
has been the focus of much refinement, and will vary from application to
application. (The angles in the ports control the swirl, for example.) “
Those ports, those are essentially our cylinder head, cam timing and valve
profiles, all in one,” says Dave Johnson, CEO.
Achates Power is not a product development company, Johnson notes—it is a
technology development company. Achates is building the analytical models to
figure out how to design the ports for any given applications. Achates then
exercises the models for a specific customer’s application. Click to
enlarge.
Achates Power currently has engine programs under development with 12
leading engine manufacturers, including work with Cummins on the Advanced
Combat Engine for the US Army, an Opposed-Piston, Gasoline Compression
Ignition Engine for the US Department of Energy’s Advanced Research
Projects Agency-Energy (ARPA-E) in partnership with Argonne National
Laboratory and Delphi Automotive, and Fairbanks Morse. These customers have
a wide range of product specifications: from 50 hp to 5,000 hp power output,
for example, in different types of vehicles, using different fuels.
While we continue to work on our customer programs, and research and
development programs (like Gasoline Compression Ignition), we are excited to
showcase the fuel efficiency, low emissions and outstanding driving
characteristics of our Opposed-Piston Engines. There is no technical
solution to respond to the proposed 2025 CAFE regulation that is as cost-
effective, compatible with our existing vehicles and fuels, ready for
production and adaptable to future renewable fuels as our Opposed-Piston
Engines.
The OP Engine confirms what the industry already knows; the technology
needed to exceed these standards and deliver fuel economy and cost savings
to customers is currently available, and works with existing infrastructure
and fuels. We have a development program underway to create the engine and
look forward to coming back to the North American International Auto Show in
2018 to show our progress and we’re even more excited to drive the vehicle
later that year.
—David Johnson, president and CEO, Achates Power
Light-duty diesel OP. Achates has been considering a light-duty version of
it engine for awhile, and, in early work, compared an earlier version of a 2
.7-liter, 3-cylinder implementation (similar to the one to be deployed in
the demo truck) to the Cummins ATLAS inline-4 diesel.
ATLAS (Advanced Technology Light Automotive Systems) is the result of a
collaboration between Nissan and Cummins reaching back to a US Department of
Energy project which began in 2010. ATLAS is targeting a Tier 2 Bin 2
emissions-compliant diesel for application in a light duty pickup, along
with a 40% fuel economy improvement over current gasoline V8 powered half-
ton pickups.
In March 2015, Cummins reported that ATLAS was capable of meeting 2025 CAFE
requirements for a half-ton pickup as well as beating Tier 2 Bin 2 emissions
standards. (Earlier post.)
Atlas
Using data from an SAE paper for ATLAS data (SAE 2013-01-0282), Achates
engineers calculated that their opposed piston engine would outperform ATLAS
interms of fuel economy and engine-out emissions.
Atlasfe
The Achates 2.7-liter engine to be deployed in the demo truck is a new clean
-sheet design incorporating all the latest learnings. Engine design will be
complete early this year, with first physical prototypes being manufactured
by the end of the year. Vehicle development will start early in 2018, with
initial demonstrations that year.
OPGCI. Gasoline compression ignition (GCI) uses high cylinder temperatures
and pressures to spontaneously combust gasoline fuel without requiring spark
plugs. Benefits are projected to include high-efficiency, low-emissions and
low-cost. The opposed piston engine is a promising platform for GCI:
Superior mixture preparation. 4-stroke engines (generally) use a single
injector, with spray aiming at the cylinder wall, leading to high
probability for fuel in crevice volumes. OP engines use diametrically
opposed dual injectors with the potential for the cancellation of spray
momentum. Additionally, there is simply a longer distance for fuel to reach
the crevice area.
In addition, the proprietary combustion system design (both pistons form the
combustion chamber) provides high mixing. Further, the split injector flow
enables superior small quantity control.
Better peak load management. A 4-stroke requires high BMEP to achieve
competitive power and torque density. A high compression ratio and high
charge mass causes high cylinder pressure.
The OP engine requires lower BMEP for maximum load. Its higher efficiency
requires less fuel. The larger cylinder volume tolerates faster heat release
rates for the same combustion noise.
Superior charge temperature and pumping management. The OP engine features
high internal EGR with lower pumping. Due to its large, fast opening ports,
there is low restriction. A high trapped temperature results in high exhaust
gas temperatures.
Achates is working with Delphi Automotive (which has been avidly pursuing
gasoline compression ignition for some time) and Argonne National Laboratory
on the ARPA-E-funded project to develop the OPGCI engine. (Earlier post.)
ARPA-E is providing initial funding of $9 million to this project over three
years; Achates Power, Argonne and Delphi expect to spend a total of $13
million on the program, including cost share. The $9-million award was “one
of the largest single ARPA-E awards ever made,” noted Chris Atkinson, the
ARPA-E program manager for the Achates project.
The goal of the 30-month Achates ARPA-E project is to deliver a three-
cylinder, 3.0-liter opposed-piston, gasoline compression ignition engine
applicable to large passenger vehicles, pick-up trucks, SUVs and minivans.
It could also be the first of a family of OPGCI engines spanning 1.0 to 4.0L
displacements, said Redon.
The smaller displacement derivative (1.0L) could be extremely interesting as
a range extender, while a two-cylinder derivative could serve nicely as a
direct drop-in for front-wheel drive applications, delivering around 180 hp
and 430 N·m from a swept volume of 1.8 liters.
Ope2
Potential light-duty OP engine family. Source: Achates Power. Click to
enlarge.
Resources
Redon, F., Sharma, A., and Headley, J. (2015) “Multi-Cylinder Opposed
Piston Transient and Exhaust Temperature Management Test Results,” SAE
Technical Paper 2015-01-1251 doi: 10.4271/2015-01-1251 | z***7
发帖数: 555 | 2 https://youtu.be/3P1JrTe24AY
It would be a mistake to count out the internal-combustion engine as
yesterday's technology, soon to expire in a puff of exhaust gas.
Electrification is coming, but meanwhile engineers have offered more
innovation for the venerable gas engine in the last three years than they
did in the previous 20. The result is 40 mpg on the highway, from four-
cylinder power plants with the same performance as older V-6s or even V-8s.
Achates Power typifies the new thinking. Its target is a chronic polluter:
the two-stroke oil burner normally seen in scooters, weed whackers, lawn-
mowers and old Saabs. The East German Trabant used a two-stroke engine,
which could usually be seen trailing a cloud of black smoke. It was rated by
Time as one of the 50 worst cars ever made.
Achates, an engine developer based in San Diego, claims its opposed-piston,
compression-ignition two-stroke diesel can power a 40-mpg (highway) economy
car like the Ford Fiesta with a 50 percent or more improvement. Yes, 60 mpg
is possible, the company says, while also meeting the tough smog/greenhouse
gas emissions regulations that automakers soon will face.
According to CEO Dave Johnson, the Achates innovations include two cylinders
in one combustion chamber and eliminates both the valve train and cylinder
head, "giving us tremendous efficiency advantages." It also uses less raw
material and fewer components, but a completely conventional manufacturing
process, which Johnson says will dramatically lower automakers power plant
costs. Diesels also have an inherent fuel economy advantage.
Johnson told me all this, but Achates doesn't actually have a car to show
the press, proving its claims. I'm impressed that the company's fuel lab
boasts "laser Doppler anemometry and laser-induced fluorescence," but I have
no idea what it means. The privately held firm hasn't signed on any high-
volume automakers, though it boasts a string of Ph.D. engineers and backing
from big names such as Sequoia Capital, RockPort Capital, Madrone Capital,
InterWest Partners and Triangle Peak. Its founder is Dr. James Lemke, who
initially drew investment from the late John Walton, son of Walmart's Sam.
Before I proclaim this engine the greatest thing since sliced bread, I'd
like to see it much further down the road. I'd want to see independent fuel
economy and emissions validation. I'd want to see noise, vibration and
harshness studies. I have unpleasant memories of the Trabant. Frankly, I've
had other meetings with "breakthrough" engine companies whose tech never
amounted to anything. One of the biggest hurdles for companies like Achates
is to get major automakers - which have huge power plant R&D staffs, after
all - to want to license their innovations. Unless Achates wants to start
building cars itself, that's its only option.
Battery companies are in the same basic situation. Unless they're vertically
integrated like China's major carmaker/battery producer BYD, they can't go
it alone. Some battery makers, with A123 as a prime example, have grabbed
the brass ring of auto partners, only to run into cash-flow problems waiting
for those partners (including Fisker and GM) to ramp up into large orders.
The two-stroke concept remains intriguing to auto companies, despite some
setbacks. "I probably spent $50 million of GM's money proving two-strokes
don't work in automobiles," GM veteran Don Runkle told Popular Mechanics.
But Runkle changed his mind, the magazine reported, when he encountered
another opposed-piston design from EcoMotors' Peter Hofbauer that sounds
very similar to the approach taken by Achates. EcoMotors raised $32 million
from prominent investors including Bill Gates and Khosla Ventures. Grail,
Pinnacle and Transonic are other companies working on two strokes. EcoMotors
claims 100 mpg is possible in a five-passenger car.
Anyway, I applaud what Achates is doing, but wouldn't yet predict that
tomorrow's cars will have 60-mpg opposed-piston, compression-ignition two-
stroke diesels under their hoods. The fact that so many key investors are
putting money into two-strokes is certainly encouraging, though.
Here's a techie video that explains more:
Read more at: https://phys.org/news/2012-09-amazing-mpg.html#jCp
Read more at: https://phys.org/news/2012-09-amazing-mpg.html#jCp
https://youtu.be/3P1JrTe24AY |
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