There is currently a widespread concern about the actual nitrogen oxides (NOx) and particulate matter (PM) emissions of gasoline direct injection (GDI) vehicles, which have dynamically penetrated into the US passenger vehicles market and are expected to eventually replace the less efficient port fuel injection (PFI) vehicles. Although GDI engines are knows to significantly improve fuel economy and lower greenhouse gas emissions (GHG) when compared to PFI engines, they produce higher PM emissions due to the direct spray of gasoline into the combustion chamber. This leads to locally rich, diffusion-governed liquid fuel combustion that creates more PM formation. Gasoline particulate filters (GPFs) are introduced as an effective strategy to reduce the tailpipe PM mass and the number of ultrafine particles under a range of driving conditions and at the same time meet California’s PM mass emission standards.
The difference between conditions of the type approval dyno test cycles defined by the vehicle emission regulations and the real driving can contribute to the differences between expected and actual pollution levels, average cycles are designed more than 20 years ago which cannot give full picture and necessarily accurate estimate of typical power demands on the vehicle’s engine. Furthermore, it is disclosed that some verified the engines and vehicles are meeting current stricter regulations on FTP75 and US06 dyno tests but emitted more PM and NOx pollutions out of limits, Volkswagen (VW) Scandal is a typical lesson for demand of real world driving emission test. This has led to the introduction of in-use vehicle emission monitoring and regulations by means of portable emissions measurement systems (PEMS). With recent developments in the US and the European Union (EU), PEMS is becoming an important regulatory device. Both the Environmental Protection Agency (EPA) and the California Air Resource Board (CARB) have begun testing the ability of PEMS to accurately measure real driving emissions.
The objective of this study is to examine the PM mass, PM soot, particle number (PN), and gaseous emissions of a current technology GDI vehicle during on-road testing with and without a catalyzed GPF. Testing was performed on three routes with different topological characteristics, representing urban, rural, highway and mountain driving conditions. The vehicle was tested in triplicated in downtown Los Angeles, Mt. Baldy, and in San Diego. The results of this work will be discussed in the context of the impact of GPF and driving patterns on tailpipe PM, PN, gaseous emissions and fuel economy.
The results showed statistic significant filtration rate up to 99% for PMsoot emissions by employing catalyst GPF instead of traditional TWC catalyst, relatively great reduction for total PM, PN and a trend of effective reduction for gaseous emissions were observed by analyzing the data, no measureable impact was found for fuel economy. With all these beneficial performances we can summarize the conclusion that GPF can be a reliable strategy for GDI vehicle emission control.