Analysis on Emission Characteristics of Fine Particle Number from Natural Gas Engines Using Different Fuels

A natural gas engine meeting the China VI emission standards was selected, and World Harmonized Transient Cycle (WHTC) tests under both cold and hot conditions were conducted using four types of fuels: low-calorific-value natural gas, high-calorific-value natural gas, liquefied petroleum gas, and commercially available natural gas. Simultaneous measurements were taken of particle number emissions with diameters above 10 nm (PN10) and above 23 nm (PN23) both before and after the three-way catalyst (TWC). The results show that PN10 under the cold WHTC cycle is 2.3 to 3.9 times, 2.0 to 3.0 times under the hot WHTC cycle and 2.1 to 3.1 times for the cold-hot weighting results compared with PN23 for this natural gas engine fueled with the four types of fuels. Compared with the hot WHTC, the raw PN10 emissions under the cold WHTC were 130% to 650% higher, and the tailpipe PN10 emissions were 228.6% to 837.5% higher. Fuels with multi-carbon components are more conducive to the formation of PN10 under hot conditions. The TWC has a limited effect on particulate number removal. Especially under cold conditions, it may even lead to an increase in PN emissions.