Tier 4 Locomotive Achieves Stringent Emission Standards

Over the last decade, the U.S. government has enacted a number of rules designed to reduce smog and air pollution in cities and towns. For locomotive makers, like GE, that means addressing two main culprits: nitrogen oxide (NOx) and particulate matter (PM) like tiny chemical, metal, soil and dust particles.

Tier 4 emission standards will kick in for locomotives on January 1, 2015. Every new engine produced must slash particulates by 70% and NOx by 76% from the current Tier 3 regulations, and thanks to technology developed at GE Global Research, GE has built the world’s first locomotive that tackles the problem head-on, in an ingenious way.

Since 2005, GE has invested $600 million in the development of a Tier 4 locomotive that eliminates the need for any NOx and PM exhaust “after-treatment,” the catchall industry term for filters, converters and similar technology.

One of the easiest ways to adhere to the new Tier 4 standards would have involved adding a large filter and a 4,000-pound catalytic converter, as heavy as a passenger car, on top of the engine. The converter uses many gallons of urea, a chemical compound first discovered in urine, to break up NOx in diesel exhaust into nitrogen and water.

But the solution has a big downside. The converter hampers access to the engine and adds extra maintenance. Railroads would also have to invest an estimated $1.5 billion in urea distribution infrastructure.

GE researchers came up with a better way—one that solved the problem inside the engine and cut out the need for urea, converters and PM filters altogether.

Engineers from GE Transportation and GE Global Research spent several years in the lab, building and experimenting with a new engine design. The team at GE Global Research built a single cylinder engine for testing, gathered detailed measurements of the exhaust and plugged the information into custom software models designed to simulate a full-scale engine.

Engineers found that it was crucial to keep the temperature inside the cylinder at an optimal level to reduce NOx and PM. They devised an ingenious system that pipes in some of the hot exhaust gas to keep the engine at the desired temperature.

Today, GE’s new Tier 4 Evolution Series Advance Power 4, ecomagination certified locomotive, is the only engine that meets the EPA’s Tier 4 requirements without any after-treatment technology. With no need for a filter or a converter, it’s truly a game changer in the industry.