Marine engine makers gear up for stiffer emissions standardsOct 1, 2013 11:04 AM
Photos courtesy Cummins Inc.
A Cummins QSK38 Tier 3 engine, with environmental mitigation taking place on the side.
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As marine engines that meet U.S. Environmental Protection Agency (EPA) Tier 3 emission requirements enter the market, manufacturers are preparing for Tier 4 standards on large marine diesels using technology comparable to that found on highway engines.
Depending on the size of the engine based on displacement per cylinder, Tier 3 requirements phase in through 2014. The EPA calls Tier 3 a “near-term” standard. According to manufacturer representatives, moving from Tier 2 to Tier 3 requirements is an incremental step compared to upcoming requirements for larger engines.
The EPA requires newly constructed vessels to use engines that meet the emission requirements in force at the time. Replacement engines are required to meet the standards also, with substitutions allowed if no comparable engine is commercially available.
A Cummins QSK19 Tier 3 engine, which became available less than a year ago.
John Deere Power Systems offers a range of Tier 3 compliant diesels, including this one, from 75 hp to 750 hp for genset use.
This MTU 8v4000m54 arrived on the market in mid-2013. Accompanying models in the product line are available in 8, 12 and 16 cylinders for offshore supply vessels, towboats and large yachts.
There are few visual cues that an engine meets the Tier 3 requirements because manufacturers have been able to meet the requirements with in-cylinder technology.
Most Tier 3 engines use high-pressure common-rail fuel injection, electronic controls and engine management with ultra-low-sulfur fuel to reduce particulate matter and nitrous oxide (NOx) emissions.
“The look and feel and transient responsiveness should be transparent,” said Michael Aufdermauer, chief engineer for commercial marine at Cummins Inc. “If you’re on a crew boat that has 50-liter engines at 1,800 hp, moving from Tier 2 to a Tier 3 you should not see any difference in the operation.”
The higher pressure of the common rail fuel injection allows the engine to atomize the fuel and air mixture better so more of the fuel burns in the cylinder, reducing particulate emissions, said Jeff Sherman, marine sales manager for MTU.
The goal was to reduce emissions in a way that’s transparent to marine operators while delivering power, maintenance and durability.
“The high-pressure common rail makes the engine a little more responsive from an operational standpoint and maybe less smoke of course, but there won’t hardly be any difference to the operator,” said Carl Micu, manager of original-equipment engine and drive train sales in North America and South America for John Deere Power Systems.
However, some engines may see a small decrease in fuel economy, in the 1 percent to 2 percent range.
“When you climb into higher tiers of emissions requirements, you have a fuel penalty because it takes more fuel to clean the engine when it’s running hotter,” Sherman said.
Other tweaks included changing valve timing and optimizing engine airflow. For example, John Deere boosted the power of its 4.5-liter engine to equal the previous 6.8-liter turbocharged version.
“We increased the power by going to more efficient charge air cooling, more efficient common rail injection, optimizing the turbocharger for the size and displacement,” Micu said.