Particle Number Emissions of Gasoline, Compressed Natural Gas (CNG) and Liquefied Petroleum Gas (LPG) Fueled Vehicles at Different Ambient Temperatures

Abstract

Compressed natural gas (CNG) and liquefied petroleum gas (LPG) are included in the group of promoted transport fuel alternatives for traditional fossil fuels in Europe. Both CNG and LPG fueled vehicles are believed to have low particle number and mass emissions. Here, we studied the solid particle number (SPN) emissions >4 nm, >10 nm and >23 nm of bi-fuel vehicles applying CNG, LPG and gasoline fuels in laboratory at 23 °C and sub-zero (−7 °C) ambient temperature conditions. The SPN23 emissions in CNG or LPG operation modality at 23 °C were below the regulated SPN23 limit of diesel and gasoline direct injection vehicles 6×1011 1/km. Nevertheless, the limit was exceeded at sub-zero temperatures, when sub-23 nm particles were included, or when gasoline was used as a fuel. The key message of this study is that gas-fueled vehicles produced particles mainly <23 nm and the current methodology might not be appropriate. However, only in a few cases absolute SPN >10 nm emission levels exceeded 6×1011 1/km when >23 nm levels were below 6×1011 1/km. Setting a limit of 1×1011 1/km for >10 nm particles would also limit most of the >4 nm SPN levels below 6×1011 1/km.

Particle Number Emission for Periodic Technical Inspection in a Bus Rapid Transit System

“…The present results are in agreement with other studies that reported CNG vehicles as high suppressors of PN emission [26,27]. However, these results only included particles emitted in the range of 23-1000 nm.…”

“…However, these results only included particles emitted in the range of 23-1000 nm. Several recent studies have shown that CNG and liquified natural gas (LNG) vehicles have particularly high PN emissions in the sub-23 nm range [24,[27][28][29]. On-road tests of PN emission factors, with PNC measurements starting at a particle size of 2.5 to 5 nm, revealed that a CNG truck had higher emission than three diesel-fueled vehicles with DPF certified to the same emission standards [30].…”

“…The PN emission of CNG vehicles for particles larger than 10 nm was found to be low, but the sub-10 nm emission was shown to be significantly elevated, increasing up to 90 times when extending the lower detection limit to 2.5 nm. Lähde and Giechaskiel [27] measured the solid PN emission in two Euro 6d CNG and one liquified petroleum gas (LPG) light-duty vehicles, following the World harmonized Light vehicles Test Cycles (WLTC) on a chassis dynamometer, finding that the CNG operation had sub-23 nm PN emission between two and 10 times higher than >23 nm PN emission. Most of the excess emission was found in the particle range between 10 and 23 nm.…”

Measuring Emissions from a Demonstrator Heavy-Duty Diesel Vehicle under Real-World Conditions—Moving Forward to Euro VII

“…SPN 23 and SPN 10 emissions were calculated using the total CVS flow and the Particle Correction Reduction Factor (PCRF) (of 30 nm, 50 nm, and 100 nm) according to the Regulation [3]. SPN 10 was corrected for additional particle losses due to diffusion at the sampling point, as it was sampling from the secondary outlet of the instrument and not from the internal position as the 23 nm counter [12]. Specifically, for the sub-23 nm particles, SPN 10 -SPN 23 , we calculated 20% more losses than those considered in the PCRF and we corrected accordingly the results.…”

Waste-Derived Renewable Hydrogen and Methane: Towards a Potential Energy Transition Solution

“…By utilizing CNG to power fuel-cell electric vehicles (e.g., cars or trucks) or as a feedstock for synthetic aviation and marine fuels, the low-carbon economy can replace the need for fossil fuels such as fossil-based gasoline and diesel. Recently, interest in CNG-based vehicles has grown in the US and Indian markets because they are more affordable, less combustible and deliver more energy [76,77].…”