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Heat Transfer Advantage of Opposed-Piston Engines

To maximize the efficiency of an engine, one must minimize losses. Heat transfer to the cylinder and piston walls is a large source of heat loss in engines. Cooling systems keep these engine components from overheating, but all that heat being carried away by the cooling system is lost energy.
 
Many factors contribute to the heat transfer—and energy loss—of an engine, but a major one is the ratio of the surface area of the combustion chamber to the volume of the combustion chamber during combustion. The higher the ratio, the greater the heat loss as there is more surface area to absorb the heat from combustion. Continue reading

Just Back from the MTZ Heavy-Duty Engines Conference

ATZ Live—part of the publishing group behind MTZ and other technical magazines—organized a conference in Nuremberg, Germany last week with a focus on heavy-duty, on- and off-highway engines. I had the chance to attend this conference and also delivered a talk introducing our latest, exciting results.
 
The conference is an annual event and this year was the seventh time engineers from the heavy-duty engine industry got together. Over the years, the conference moved to the locations of the heavy-duty engine manufacturers. This year it was held in Nuremberg, which is the home of MAN. Continue reading

Greetings from Beijing

This week, I attended CALSTART’s U.S.-China Clean Truck and Bus Summit in Beijing. The event brought together representatives from key agencies of both countries with the goal of increasing U.S. exports of clean transportation technology for trucks and buses.
 
While at the conference, I participated in a panel titled “Spotlight on U.S. Industry Leaders”, along with Shiyi Zhou of Eaton and Ning Lei of Navistar. And, over the course of the three-day event, I made the following observations: Continue reading

In What Way Is a Hamburger Like a Truck?

California has been leading the effort for ever-lower vehicle emissions standards for decades, largely due to smog problems in the Los Angeles basin. A unique confluence of factors makes L.A. particularly susceptible to smog. The eastern edge of the basin is ridged by the Transverse mountain ranges, which often cause temperature inversion layers that trap exhaust. Combine that with a dense population, a heavy reliance on automobiles, and a large port and you have a recipe for smog. And since L.A. gets essentially no rain from May to October, there is nothing to provide relief.
 
As a southern California resident, I am glad that the significantly reduced emissions from cars and trucks—driven by standards from the California Air Resources Board (CARB) and the U.S. Environmental Protection Agency (EPA)—has literally cleared the air. Continue reading

A More Efficient Engine for Military Vehicles

Wednesday marks the start of GVSETS, a three-day event focused on the latest technologies for military ground vehicles. Introducing breakthrough innovations designed to aid and protect our troops, this year’s symposium features a presentation from Achates Power. The topic: how can the Achates Power opposed-piston engine improve the operational efficiency of military vehicles?
 
While opposed-piston engines have been used in aviation and combat vehicle applications and continue to be used in maritime applications, there are several factors that distinguish the Achates Power engine from previous opposed-piston engines. Continue reading

Evaluating and Enhancing Engine Durability

Meeting emissions standards, improving fuel efficiency and lowering manufacturing costs is critical to the success of any new engine design. So too is durability. In the commercial vehicle market, for example, truck owners expect their vehicles to log one million miles or more. As a result, engine developers are investing significant resources in durability analyses—before ever putting their engines into a vehicle.
 
At Achates Power, we use advanced modeling and simulation tools to evaluate and enhance the durability of our engine. Continue reading

Using Technology to Optimize Fuel Injection

Creating an efficient, durable fuel injection system is no simple task—especially for our opposed-piston, two-stroke diesel engine. The reason: our injection geometry is completely different. Unlike conventional engines, which inject through the cylinder head towards the piston, the Achates Power engine lacks a cylinder head so injection comes from the side, between the pistons and into the swirl.
 
In designing the optimal fuel injection system—for our engine or any other—there’s a lot to consider, including the number of injectors, the number of holes per injector, the size and orientation of the holes, the number of injection events, and the timing and sizing of those events. Continue reading

Why a Two-Stroke Engine?

What comes to mind when you think of a two-stroke engine: a moped, scooter or chain saw? Or, maybe it’s the sight or smell of blue smoke. The Achates Power opposed-piston, two-stroke (OP2S) engine bears no resemblance to these traditional two-strokes. For one, in our engine, the fuel and oil don’t mix, so there’s no smoke from burning oil. And, since the fuel is directly injected into the combustion chamber, our engine doesn’t suffer from high hydrocarbon emissions like its two-stroke counterparts. But, these aren’t the only reasons opposed-piston, two-stroke engines are garnering interest. The two-stroke engine has potential thermodynamic, package and economic benefits that are hard to ignore. Continue reading

Is the Number of Cylinders Important to Engine Efficiency?

When it comes to the performance and efficiency of an opposed-piston, two-stroke engine, does the number of cylinders make a difference? If you guessed “yes”, you’re right.
 
Based on extensive analysis, Achates Power has determined that its three-cylinder, opposed-piston engine is the optimal design from a gas-exchange perspective, especially when compared to a two- or four-cylinder design. The reason: the gas exchange duration in a two-stroke engine is about 120 degrees crank angle. Continue reading

The “Drivers” Behind Diesel’s Growing Popularity

For some Americans, the thought of a diesel engine conjures up images of noisy, lumbering tractor-trailors belching clouds of black smoke. While that may have been an accurate depiction 20 years ago, it’s not anymore. Today’s diesels are clean, quiet, powerful and efficient. In fact, they’re cleaner and more efficient than gasoline engines, causing consumers to take notice. Last year, U.S. sales of diesel-powered passenger vehicles increased 27%. This while overall sales were up just 10%, hybrid market share declined, and electric vehicle revenue fell short of projections. Continue reading