Greenhouse Gas Reduction from EnviroKool Piston in Lean Burn Natural Gas and Diesel Dual Fuel Heavy Duty Engine

Heavy-duty (HD) internal combustion engines (ICE) have achieved quite high brake thermal efficiencies (BTE) in recent years. However, worldwide GHG regulations have increased the pace towards zero CO₂ emissions. This, in conjunction with the ICE reaching near theoretical efficiencies means there is a fundamental lower limit to the GHG emissions from a conventional diesel engine. A large factor in achieving lower GHG emissions for a given BTE is the fuel, in particular its hydrogen to carbon ratio. Substituting a fuel like diesel with compressed natural gas (CNG) can provide up to 25% lower GHG at the same BTE with a sufficiently high substitution rate. However, any CNG slip through the combustion system is penalized heavily due to its large global warming potential compared to CO₂. Therefore, new technologies are needed to reduce combustion losses in CNG-diesel dual fuel engines. In this paper, Tenneco’s EnviroKool® piston technology is evaluated as a mechanism to increase combustion chamber temperatures and to reduce combustion losses in a lean burn CNG-diesel dual fuel engine. The EnviroKool piston has a unique cooling gallery design which allows the piston surface temperature to increase by an estimated 100 °C relative to a standard steel piston. A fumigated CNG and diesel direct injected 13 L engine was used which operates with reactivity-controlled compression ignition (RCCI) at low to mid loads, and a pilot dual fuel strategy at mid to high loads. The EnviroKool piston provided a 3.6% reduction in GHG over the European Stationary Cycle (ESC) by both reducing combustion losses and allowing for a higher CNG substitution rate. The final engine demonstration including the EnviroKool pistons reached as low as 379 g/hp-hr brake specific GHG over the ESC.