Improving Fuel Economy in Diesel Locomotives

MOSCOW - Automobiles are far from the only modes of transportation for which people are seeking to improve fuel economy. Rail operators also want to raise fuel efficiency, both as a way of cutting costs and helping the environment. And as with on-highway vehicles, the lubes industry is aiding the cause, an industry insider said recently, partly by reducing oil viscosity.

Alexander Medzibovskiy, head of Moscow-based lubricant and lube additives maker Qualitet, said that use of low-viscosity oils to reduce energy losses to friction in diesel locomotives is one of the main steps that Russian Railways is taking to improve fuel economy.

Russian Railways is a state monopoly that controls the railway transportation in Russia.

Other factors for better fuel economy include improved diesel engine efficiency, idleness minimization, maximum possible loading of the wagons and using wagons of increased capacity, as well as improvement of fuel distribution and metering systems, he told RPIs International Lubricants conference held here in October.

The systems main source of power is the electricity grid, which contributes 44 percent of the total energy needed. The rest comes from boiler furnace and diesel fuels.

Diesel locomotives are technically known as diesel-electrics, and they came into widespread use during the mid-20th century. The diesel engines in diesel-electric locomotives are not the prime mover of the locomotive, but it provides the energy for the electric generator, which in turn powers the traction motors in the locomotive trucks that are turning the wheels that propel the unit forward.

Russian Railways demand in diesel fuel is 3 million tons per year. The expenses for motor oil make 0.08 to 0.1 percent of its fuel expenses, while the selection of oil ensures up to 5 percent [improvement in] fuel economy, Medzibovskiy said.

In 2006 Qualitet started to develop low-viscosity oils for four-stroke diesel locomotive engines.

The initial tests have shown that oil consumption is up to 1.9 percent of the fuel consumption, while 50 percent of the oil is burnt and should be replaced, while the oil drain interval is up to 60,000 kilometers. The aim was to achieve 100,000 kilometers of oil drain interval and an energy conserving oil formulation, Medzibovskiy said.

The company achieved this aim with development of two types of diesel locomotive engine oils. The longer drain interval was achieved with upgrade of detergent properties, anti-oxidation properties improvement and increase of thermal resistance, as well as increase of anti-wear properties, Medzibovskiy said.

Photo: a-plus image bank/Alamy

Russian Railways is set to perform comprehensive engine manufacturer and bench tests, as well as field and rheostatic bench tests to show that these oils achieve fuel economy and long drain intervals.

The tests showed that the low viscosity of oil can affect those areas of the engine that are subject to the hydrodynamic lubrication regime. Friction power losses depend only on the oil viscosity, and its dropping plays a positive role. This mode is acting in the crankshaft bearings between the piston rings and cylinder wall, at the main area piston stroke. These units especially are responsible for a significant share of mechanical losses, or over 70 percent, Medzibvskiy observed, adding that the lower the oil operating temperature in friction areas the greater the gain in efficiency.

Qualitet found that an engine oil that contributed even more to fuel economy improvement and that allowed an even longer drain interval was possible through an increase of thermal-oxidation stability, use of viscosity modifiers that are resistant to thermomechanical destruction and use of friction modifiers to decrease power losses and wear rate.

Its possible to develop an SAE 15W-40 fuel-economy engine oil that will ensure a 5 percent saving of fuel and [a recommended] oil drain interval of up to 200,000 kilometers or more, Medzibovskiy said.

For example, British diesel locomotive engines use SAE 15W-40 engine oil in diesel locomotives for more than 30 years, he said.