Internal Combustion Engines (ICE) are very well developed and increasingly sophisticated. There is a pipeline of efficiency improving technologies that can still be used. Adapting high efficiency ICEs to hydrogen/natural gas mixtures (HCNG) or to hydrogen would result in very cost effective power plants for near to medium term. Such an ICE development would be part of a long term H2 roadmap. In an ICE HCNG allows more lean combustion and retarding of the spark timing.

Previous tests have shown that HCNG fuel (20 vol% H2) can reduce NOx emissions without affecting the performance and efficiency of a lean burn natural gas engine. Hydrogen from a renewable source can help reduce GHG emissions.

This program targets development and testing of a new calibration for MD/HD lean burn natural gas spark ignition engines with external mixture formation to operate on HCNG. The overall project goals are to develop HCNG powered vehicles that serve as a commercially viable bridge for utilizing hydrogen in the medium and heavy-duty markets as well as demonstrate emissions benefits and commercial viability of HCNG fuel in state of the art internal combustion engines.

A test methodology was developed with following objectives in mind: • Gain understanding of HCNG combustion. • Determine if NOx reductions could be achieved on modern engines operating near the lean air/fuel limit. • Understand current engine hardware limitations with HCNG. • Determine optimal hydrogen content. • Configure engine controls for operation on the chosen mixture.

The paper will present knowledge gained during engine combustion development and calibration, performance and emissions testing as well as experience with vehicle field trials. Future directions with the HCNG technology would also be discussed.