Another company developing fuel-efficient, opposed-piston engine

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Earlier this year, we wrote about the OPOC engine from EcoMotors. Since then, we've discovered another opposed-piston engine, from Achates Power in San Diego.

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Achates Power building 2.7L opposed-piston light-duty engine; exceeding CAFE 2025, Tier 3 targets at lower cost

Green Car Congress  /  January 13, 2017

Stemming from a major project partially funded with a $9-million grant from the Advanced Research Projects Agency - Energy (ARPA-E) to develop an opposed-piston two-stroke gasoline compression ignition engine (OPGCI) (earlier post), Achates Power announced it is developing a 2.7-liter, 3-cylinder (i.e., six-piston) light-duty version of its opposed piston engine (OPE) in both diesel- and gasoline-fueled versions. Achates will demonstrate the engine in 2018 in a driveable light-duty truck.

The 2.7-liter compression-ignition OPE will will be 30-50% more fuel efficient than comparable diesel and gasoline direct injection engines, reduce emissions and cost less than alternative technologies under development for meeting 2025 CAFE fuel economy and Tier 3 emission targets.

The 30-50% improvement metric encompasses both gasoline and diesel variants of the OP engine. An OPGCI engine versus a four-stroke spark ignition engine will be on the higher end of that scale (50%), while the OP engine running on diesel versus a four-stroke compression ignition (diesel) will be on the lower end of the scale (30%).

The new Achates Power 2.7-liter OPE will deliver nominal power of 270 hp and max torque of 650 N·m (479 lb-ft); the vehicle will achieve 37 mpg—12% above the 33 mpg fully phased-in CAFE 2025 requirement for a full-size, light-duty pick-up truck (65-70 sq. feet). (That works out to an estimated window-sticker label rating of 28 mpg combined.)

Further, Achates is planning to meet the 0.03 g/mile NMOG + NO_x Tier 3 fleet average target (the old Tier 2 Bin 2 level). Achates has done several studies with leading aftertreatment manufacturers for a diesel application; results suggested the Achates OP engine could reduce the diesel engine aftertreatment cost by 30%.

With the OPGCI engine, Achates also expects a significant cost reduction of the aftertreatment because the engine-out NO_x and soot are much lower than with diesel.  The current best guess is close to gasoline SI aftertreatment system cost, said Fabien Redon, Vice President, Technology Development.

We are capable of achieving very low engine-out NO_x and do it with a lower penalty in BSFC.  Our NO_x/BSFC trade-off is not as steep, so in general we favor lower NO_x regulations because it makes our engine even more competitive.

—Fabien Redon

The light-duty engine is a “basic” Achates opposed piston 2-stroke engine, said Redon—i.e., it does not make use of more advanced technology elements under consideration for lowering the fuel consumption of combustion engines.

The beauty of that is that it basically allows us to exceed the 2025 CAFE regulation without adding any cost to the vehicle. This is taking the existing powertrain out, putting in the OP engine, and it exceeds the CAFE regulation.

—Fabien Redon

The corollary to that is that the addition of more fuel efficiency technologies would further reduce the fuel consumption performance of the OP engines. In other words, there still is upside potential, even after besting the 2025 CAFE target.

The OP engine would be less expensive than a current production light duty diesel, such as in the Ram, but slightly more expensive than a gasoline engine, said Redon. However, the OP solution does not require the additional fuel efficiency technology projected to meet CAFE targets, thereby making it a more cost-effective solution.

The EPA’s draft Technical Assessment Report released in 2016 forecast cost increases to integrate fuel saving technology. Using this information and a related National Academy of Sciences report, Achates Power determined that including the Opposed-Piston Engine in the roadmap to achieve CAFE will be at least $1,000 less expensive.

The Opposed-Piston Engine uses fewer parts, including the eliminating the cylinder head(s) and related components, eliminating the valvetrain and related components, and a reduction in the aftertreatment system size and cost, among other things.

A comparison between the 2.7L OP Engine and a comparable V6 with supercharger shows a part reduction of more than 60% (110 primary components for the Achates Power inline 3-cylinder engine vs. 325 primary components for the V6), enabling an approximate 10% cost reduction.

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.

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. 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.

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 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.)

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.

 

 

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Achates showcases 2.7L, 3-cylinder opposed piston gasoline compression ignition engine in F-150; estimated 37 mpg combined

Green Car Congress  /  January 18, 2018

At the North American International Auto Show (NAIAS), Achates Power and new development parter Aramco Services (earlier post) showcased a Ford F-150 fitted with a 3-cylinder, 2.7-liter Opposed-Piston Gasoline Compression Ignition (OPGCI) engine. (Earlier post.)

Fabien Redon, Vice President, Technology Development at Achates, said they estimate that the OPGCI pickup will achieve 37 mpg (6.35 l/100 km) on the combined cycle—nearly five MPG better than the proposed CAFE 2025 requirements for a vehicle of a similar size. The OP engine produces 270 hp and 480 lb-ft (651 N·m). This performance is achieved without vehicle modifications and is projected to cost $1,000 less per vehicle than widely accepted technology roadmaps currently being considered by OEMs, Achates said.

The Achates Power Opposed-Piston (OP) Engine is engineered to achieve superior thermal efficiency by virtue of its lower heat losses, improved combustion, and reduced pumping losses.

The OP Engine eliminates the cylinder head for an improved surface-area-to-volume ratio of the combustion chamber for reduced heat transfer and rejection. In addition, conventional engine valvetrain and related components are eliminated, and due to the architecture the OP Engine offers a reduction in the aftertreatment system size and cost. A comparison between the 2.7L OP Engine and a comparable V6 with supercharger shows a part reduction of more than 60%, enabling an approximate 10% cost reduction.

To fit the OP engine—with its fundamentally different shape—into the F-150 engine bay, Achates packaged its engine in a V-shape (approx. 30˚), with the cylinder bank angled on one side and the air handling and auxiliary units packaged on the other, Redon said. The pictures and video below illustrate the major components.

We chose to demonstrate our ultra-clean, ultra-efficient OP Engine in a full-size light-duty pickup truck because of the significant need and opportunity for improvement in this segment. These trucks are driven more miles, sold in higher volume, consume more fuel and emit more CO₂ than other light duty vehicles. Using our OP GCI engines in light duty trucks would reduce CO₂ and fuel usage in the same way as completely eliminating half of all cars sold each year. Using our OP GCI engines in future light trucks has the same fuel savings and CO₂ reduction as completely eliminating more than half of the cars sold each year.

An Opposed-Piston Engine is 30-50 percent more fuel efficient than comparable diesel and gasoline engines, it is a no-excuses way to meet future efficiency and emissions standards. The technology and infrastructure to meet these future standards exists and will be available for consumers in the near future.

—David Johnson, president and CEO, Achates Power

Achates Power is showing the light duty demonstration pick up truck in the Aramco display as part of a joint development agreement, which formalizes the cooperative relationship between the companies. Achates Power and Aramco have agreed to work together on a series of projects to develop and demonstrate highly efficient and clean OP engines. The first project to be announced is the in-vehicle demonstration of the 2.7L OP Engine.

For its part, Aramco Services has been investigating gasoline compression ignition engine technology for a number of years, and came to the conclusion that it would be mutually beneficial to work with Achates, with that company’s decade-plus worth of expertise and intellectual property in the field, said David Cleary, Research Center Leader at Aramco Services Company.

Achates has been developing diesel-fueled (compression ignition) opposed piston engines since its founding in 2004. The company has demonstrated substantial fuel efficiency savings in diesel applications with a high indicated thermal efficiency of 53%. (Earlier post.)

The OP GCI engine—an effort to combine the benefits of compression ignition with a readily available fuel source (gasoline) in the highly efficient opposed-piston architecture—was designed and developed by Achates Power with a $9-million award from the Department of Energy’s ARPA-E in 2015, along with partners Delphi and Argonne National Laboratory. Testing of the OPGCI engine was conducted at Argonne, and Achates Power facilities in San Diego.

Development and testing of the new 2.7L engine will continue at Achates Power facilities, and at Aramco Services research center in metro-Detroit, for both diesel- and gasoline-fueled versions. (Earlier post.) Based on current testing, the engine is anticipated to be fully integrated into the vehicle and drivable in late 2018.

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California ARB awards $7M for ultra-low NOx heavy-duty diesel truck demo project with Achates opposed-piston engines

Green Car Congress  /  March 7, 2018

The California Air Resource Board (CARB) is awarding $7 million to CALSTART to develop a Class 8 truck that will achieve a 90% reduction in NO_x along with a 15-20% fuel efficiency improvement.

The project will build and install diesel-fueled two-stroke compression-ignition Achates Power Opposed-Piston Engines into Class 8 demonstration trucks that will be road-road ready in 2019 and operate in fleet service in California in 2020.

California’s ultra-low NO_x emissions standard is 0.02 grams per brake horsepower-hour (g/bhp/hr). This program will demonstrate the first diesel engine to comply with the state standard. In addition, the engine will emit 10% less CO₂ than the 2027 federal greenhouse gas requirement.

The project is part of CARB’s Low Carbon Transportation and Fuels Investments and Air Quality Improvement Program. CALSTART will serve as the project grantee and administrator.

The project team, led by CALSTART, includes a heavy-duty truck manufacturer as well as Achates Power and leading suppliers in the powertrain and emissions industry. California’s South Coast Air Quality Management District, the San Joaquin Valley Air Pollution Control District and the Sacramento Metropolitan Air Quality Management District also are investing in the project.

Achates Power, founded in 2004, currently has a number of development projects underway spanning a variety of applications of its opposed-piston engine architecture, from light-to-heavy duty.

At the 2018 North American International Auto Show (NAIAS) in January, Achates Power and new development parter Aramco Services (earlier post) showcased a Ford F-150 fitted with a 3-cylinder, 2.7-liter Opposed-Piston Gasoline Compression Ignition (OPGCI) engine. (Earlier post.)

In 2017, engineers from Achates presented a paper (2017-01-0638) at the SAE World Congress (WCX 17) describing the development of a 55% brake thermal efficiency (BTE) commercial heavy-duty opposed-piston engine without the use of a waste heat recovery system or turbocompounding.

The two-stroke OP engine described therein employed currently available engine components, such as supercharger, turbocharger and after-treatment and featured a uniquely designed piston bowl shape to enhance mixing with a swirl-to-tumble conversion as the piston bowls approach minimum volume. This design improved fuel-air mixing and hence resulted in low soot values, increased indicated thermal efficiency (ITE)—due to better combustion phasing because of faster mixing controlled combustion—and lower NO_x because of improved area-to-volume ratio and lower fueling requirement per cycle.

An optimized system included a high trapped compression ratio piston bowl, ports designed to provide best scavenging performance, thermal barrier coating on piston bowls and dual injector with an optimized spray pattern layout.

The Achates engine model destined for the Class 8 demonstration is related to the 9.8-liter unit, but with modifications, said David Johnson, Achates CEO. For one, it’s a bit bigger: 10.6 liters.

We’re aiming at the heart of the Class 8 market. The engine will deliver 450 hp and all the necessary torque, along with the ultra-low NO_x.

—Dave Johnson

With the reduction in steady-state engine-out NO_x from the engine, meeting the ultra-low NO_x specification is really a problem of cold starts, Johnson said; i.e., warming up the aftertreatment catalyst quickly.

Achates determined in earlier work that it could run in a “catalyst light-off mode”, creating the heat required to bring the aftertreatment fully online while running the engine in a relatively clean condition. (Earlier post.)

With low engine-out NO_x and high enthalpy going to the aftertreatment system, we believe that we are able to reduce the aftertreatment warmup from 600 seconds to less than 300 seconds. That will enable us to meet ultra-low NO_x tailpipe standards. We also deliver a significant fuel economy improvement.

—Dave Johnson

Achates engineers will be presenting a new paper at World Congress this year describing more about this approach, and presenting test data.

Funding for the grant comes from California Climate Investments, a statewide program that puts billions of Cap-and-Trade dollars to work reducing greenhouse gas emissions, strengthening the economy and improving public health and the environment—particularly in disadvantaged communities.

The Cap-and-Trade Program also creates a financial incentive for industries to invest in clean technologies and develop innovative ways to reduce pollution. California Climate Investments projects include affordable housing, renewable energy, public transportation, zero-emission vehicles, environmental restoration, more sustainable agriculture, recycling and much more. At least 35% of these investments are made in disadvantaged and low-income communities.

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Opposed-Piston Diesels Enter Limited Production

Tom Berg, Heavy Duty Trucking (HDT)  /  November 9, 2018

A pair of heavy-duty opposed-piston engines will be produced for an emissions-reduction project in California, officials with the program announced Nov. 8 at a press event in San Diego.

The two 10.6-liter 450-hp engines designed by Achates Power will run in Peterbilt tractors in regular service to prove the low-emissions performance that they’ve demonstrated in laboratory simulations, officials said. They will be operated within the state by the transportation arms of Tyson Foods and Walmart, and will be running by late 2019.

Achates’ heavy-duty engine met the ultra-low nitrogen oxide standard of 0.02 gram per brake-horsepower-hour, which is 90% less than the current federal limit, said David Johnson, the firm’s president and CEO. That’s also up to 15-20% below the greenhouse gas requirement for carbon dioxide. 

The 0.02 grams per brake horsepower-hour (g/bhp-hr) Ultra-Low NOx standard target has been achieved in natural gas engines but not yet in a production diesel engine, according to a company announcement.

The project team has started building the engines that will run in the Peterbilt demonstration vehicles.

Achates is a development company whose engineers have been working to perfect the opposed-piston, or OP, concept since 2004. It expects to license designs to existing engine manufacturers but will assemble the in-service test engines at its San Diego facility.

The demonstration project is funded by the California Air Resources Board (CARB) and several air-quality districts, and managed by CalStart, a Pasadena-based non-profit organization that encourages use of sustainable transportation methods.

The Achates OP engine also achieves superior fuel efficiency by virtue of its lower heat losses, improved combustion and reduced pumping losses, Johnson said. An OP engine has two pistons per cylinder, facing each other, and a central combustion chamber. Explosive fuel burn pushes the pistons apart and their connecting rods twist separate crankshafts at each end of the cylinder. Through pulleys and gears, the crankshafts transfer their power to a single output shaft.

It is a two-stroke design with no intake or exhaust valves; fuel-air mix and exhaust enter and leave the combustion chamber through ports in the cylinders.

Achates Power is leading a project team with personnel from Aramco Services, BASF, Corning, Dana, Delphi, Eaton, Faurecia, Federal Mogul, Honeywell, Litens and Federal Mogul, along with the Southwest Research Institute.

Peterbilt will integrate and deploy the new engine in two of its Model 579 Class 8 road tractors for the project.

“This project challenges conventional wisdom in the industry: that ultra-low NOx cannot be combined with ultra-high efficiency in a diesel engine,” said Bill Van Amburg, CalStart’s executive vice president. “This impressive team is showing that you can significantly improve air quality while also making progress on climate change. We can and must do both.

“Success in this project will support widespread commercial adoption of the ultra-low NOx standard in Class 7 and 8 trucks, which will support CARB’s – and the world’s – air quality and environmental goals.”

Said Johnson, “Achates Power is committed to bringing the opposed-piston engine to market to provide a practical solution for ultra-clean, ultra-efficient and cost-effective transportation. Our project with CalStart for CARB shows the need in the market for solutions that will meet the goals we all desire, without forcing solutions on the industry.”

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Achates Names New President and CEO

Heavy Duty Trucking (HDT)  /  January 3, 2018

Achates Power has appointed David Crompton as president and CEO, joining the company after 28 years with Cummins where he served as president of both the engine business and power systems business.

Crompton has experience in the powertrain industry covering pick-up trucks, commercial vehicles, military and off-road industries. He replaces David Johnson in the role who will remain an adviser to Achates.

The appointment comes at a critical time for Achates Power, as the company plans to implement an opposed-piston engine and the company and investors have committed additional funding to speed up the design’s implementation into the marketplace.

"Achates Power can make a positive impact on the future of transportation and industrial power by providing a superior option to deliver high efficiency and low emissions across current and future markets,” said John Wall, chairman of the board for Achates Power. “The Board and Investors have full confidence in the work that the Achates Power team is doing and the ability for Dave Crompton to help bring to market an ultra-clean, ultra-efficient, low-cost internal combustion engine."

In 2018, Achates demonstrated a 2.7-liter Light-Duty Demonstration Vehicle and continued to develop its opposed piston gasoline compression ignition engine, and received funding from the California Air Resources Board (CARB) for a heavy-duty opposed engine demonstration program.