Scania is developing LNG and CNG engines and fuel systems for its truck range to meet demand for alternatively fuelled vehicles.
Scania’s launch of the OC13 gas engine marks the start of alternative fuel systems for the new truck generation. The OC13 is based on Scania’s well-proven 13-litre engine. The engine works according to the Otto principle with spark plugs and complete combustion.
There is a growing interest in operating vehicles on biogas or natural gas in countries such as Italy and France as a result of increased availability, improved infrastructure and good economic viability for hauliers. The sustainability aspects are also important – even natural gas provides a CO2 reduction of approximately 15 percent.
Scania’s gas engines are based on stoichiometric combustion, i.e. complete combustion of both fuel and oxygen. Similar to a petrol engine, the combustion is initiated by means of spark plugs. The pre-mixing of the fuel takes place upon entry into the cylinders.
“Throughout development, our aim has been to ensure the best possible driveability,” explains Folke Fritzson, Senior Engineer at Scania R&D and part of the team developing Scania’s gas engines. “The performance and characteristics should correspond to that of a modern diesel engine.”
The new 13-litre gas engine is always available with Scania Opticruise, Scania’s automated gearboxes. This means, of course, that gear changing and driving comfort are top-class for the driver, with fast, unhesitating gear selections.
Carefully thought-out tanks
The tanks are an important aspect of gas fuel operations. Both LNG tanks (for refrigerated, liquefied gas) and CNG tanks (for compressed gas) can be ordered directly from Scania. LNG always provides greater range, as a significantly larger amount of fuel is available.
“In combustion, there is no difference between LNG and CNG, but there are significant differences in the operational range,” says Fritzson. “With LNG, it’s up to 1,100 kilometres for a typical articulated vehicle on a flat road. CNG usually provides a range of up to 500 kilometres. The latter is more than sufficient for many customers, for example in regional transport with a return to the home base and refuelling every day. The mileage that can be achieved before refuelling is required also depends on the type of driving and usage, and how hilly the route is.”
In order to improve safety, Scania’s engineers have turned the tank valves backwards, away from the direction of travel. This is a seemingly simple but important detail that reduces the risk of the valves becoming damaged if hit by stones or gravel.
Longer maintenance intervals
Gas engines that operate according to the Otto cycle have shorter service intervals than diesel engines. However, Scania has achieved a significantly longer service interval, with the lifespan of the spark plugs currently setting the limit.
“We have defined the interval at 45,000 kilometres for both the spark-plug and oil changes with normal use,” says Fritzson. “This is a clear improvement over previous generation gas engines, with 30,000 kilometres as normal intervals. This reduces maintenance costs and increases availability.”
“Everything indicates that we are heading towards a breakthrough for gas engines, including heavier trucks for long-distance transport and construction-site vehicles,” says Henrik Eng, Product Director Urban, Scania Trucks. “Everyone can now benefit from good driveability and driver comfort. We also see that the rapidly growing gas infrastructure in several European countries spurs interest in using this alternative fuel.”
Scania is launching an alternative fuel initiative for the new generation of trucks, with the world premiere of a new 13-litre gas engine at the Ecomondo trade fair in Rimini, Italy.
Gas engines are generally quieter than diesel engines, and are therefore well suited for urban environments. Scania’s new Euro 6 gas engine meets the requirements of the PIEK noise limitation standard, which stipulates a noise level of no more than 72 dB(A) in areas with stringent noise limits.