Emission Factors for a Taxi Fleet Operating on Liquefied Petroleum Gas (LPG) as a Function of Speed and Road Slope

Abstract

Real-driving emissions of NO x , CO, and THC, as well as fuel consumption (FC) were studied from 18 liquefied petroleum gas (LPG) fueled taxis operating in a metropolitan road network. Euro 2 to Euro 5 technology vehicles were measured with the use of portable emission measurement systems (PEMS). Statistical processing was implemented to derive mean emission levels for the different technologies. The taxis were measured from 6 months to 2.5 years after their catalysts and lambda sensors were replaced. The emission levels of Euro 4 taxis after catalyst replacement appear higher compared to pre-replacement levels, while pre-Euro 4 taxis emission levels were moderately reduced by the catalyst replacement. Overall, Euro 5 LPG taxis exhibit the lowest emissions, even below the respective regulated limits. The NH 3 and N 2 O pollutant levels of a Euro 5 LPG taxi measured in the lab were found at about half its NO x emissions. Different integration methods of PEMS data were investigated toward the development of emission factors, including both time-based and distance-based approaches at different resolutions. Distance-based integration in sections of 500 m was considered suitable, as this provides a large dataset for statistical confidence and sufficient resolution for link-based modeling. Based on this, FC and emission factors of NO x , CO, and THC as a function of speed and road slope are presented, separately for vehicles considered as normal and high emitters. Volatile organic compounds speciation of Euro 5 taxis showed that methane and butane are the most abundant hydrocarbon species in the exhaust.

Comparison of exhaust emission from Euro 3 and Euro 6 motor vehicles fueled with petrol and LPG based on real driving conditions

“…LPG is acquired as a naturally occurring product of the natural gas extraction process or as an automatic result of the oil refining production process. LPG meets all four key objectives set by the EU in its guidelines for trans-European energy networks [7]. LPG is petroleum derived colourless gas, consists of propane or butane or from mixtures of both.…”

Are average speed emission functions scale-free?

“…Among other issues, the resolution for establishing emission laws is quite challenging. (Papadopoulos et al, 2018) described how the resolution affects emission factors. This study also confirms that the extensive use of PEMS data can enhance the inherent bias of emission functions.…”

“…In (Papadopoulos et al, 2018), the authors describe how the resolution affects EF derived from PEMS data and finally propose to establish EF on the basis of a 500m resolution. It also highlights that the extensive use of PEMS data may lead to heterogeneous methodologies for developing EF.…”

Fuel Consumption Monitoring through COPERT Model—A Case Study for Urban Sustainability

“…Fuel energy consumption from vehicles is mainly influenced by the vehicle engine. Fuel consumption can be calculated from different factors such as vehicle engine, engine cycle condition as well as vehicle parameters [9]. Fuel consumption can be estimated from the actual experiments and inspecting the independent effective variables [10,11].…”