Liquid natural gas (LNG) propulsion is a technology that plays less of a role in the current debate about diesel engines and electric motors—unfairly so. Scania has an LNG truck in its portfolio that achieves the same efficiency ratio as a classic diesel engine. How is that possible?
“The truck runs on methane gas,” explains Zoran Stojanovic, Product Manager for Gas Trucks at Scania. There is liquid methane gas, called LNG, in the tank waiting to be burned. It liquefies at minus 162°C. Its purpose is to be capable of storing five times as much energy in the same tank volume, which means you can drive five times as far.
The LNG Truck by Scania is fitted with two gas tanks, which enable a driving range of about 1,000 kilometers. “There are also tanks for a longer chassis—this one is a tractor-trailer where space is quite limited,” says Stojanovic. “We have larger tanks for the longer chassis that extend the range to up to 1,500 kilometers.”
In the past, Otto engines were not considered serious competition for the torque-heavy diesel engines. Scania shows that the opposite is the case. “It’s our philosophy that a gas engine has to provide the same torque as a diesel engine.” Scania proves its point with the LNG truck.
Clean, quiet, and efficient
Scania trucks with LNG propulsion emit up to 20 percent less CO₂ and 95 percent less nitrogen oxide (NOx) than diesel-powered engines of the current Euro 6 emission legislation. Moreover, the LNG-powered trucks release almost no particulate matter (-95 percent) due to the low-soot combustion process. This means there is no need for an expensive exhaust treatment system. The combustion noise is also reduced by about 50 percent (-3 dB) in comparison with a diesel truck.
The same torque as a diesel
“During the development process, we’re extremely conscious of creating the same torque and torque structure for our current and future engines that you would find in a diesel engine,” says Stojanovic. The advantage is that the power train remains unchanged and everything moves like a diesel engine.
The challenge in development lies mainly in finding the proper compatible tanks—aside from designing the engine, of course. Another challenge is how to mount the tanks on the chassis. The result is quite impressive: we officially meet Euro 6 norms without having an emissions after-treatment system. We only have a passive three-way catalytic converter.
“Liquid gas as engine fuel is nothing new. It’s been around for thirty years. The gas has been widely established in shipping and locomotives,” explains Stojanovic. “Technology has progressed so far that it can now be used in small and compact engines as well. Just like in our trucks.” And there is one thing Stojanovic is sure about: “These engines have a lot more potential.”