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Fuel Processing Technology - · PDF fileAlthough gasoline direct injection (GDI) engines with the TWC have the advantages of increased engine power and lower fuel con- sumption than

Aug 13, 2019

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  • Mobile source air toxic emissions from direct injection spark ignition gasoline and LPG passenger car under various in-use vehicle driving modes in Korea

    Cha-Lee Myung a, Ahyun Ko a, Yunsung Lim b, Sunmoon Kim b, Jongtae Lee b, Kwanhee Choi a, Simsoo Park a,⁎ a School of Mechanical Engineering, Korea University, 1, 5-Ga, Anam-dong, Sungbuk-gu, Seoul 136-701, Republic of Korea b Transportation Pollution Research Center, National Institute of Environmental Research, Gyeongseo-dong, Seo-gu, Incheon 404-704, Republic of Korea

    a b s t r a c ta r t i c l e i n f o

    Article history: Received 10 January 2013 Received in revised form 22 October 2013 Accepted 24 October 2013 Available online 16 November 2013

    Keywords: Mobile source air toxic emissions LPG-direct injection In-use vehicle driving mode Particulate emissions Carbonyl compounds Polycyclic aromatic hydrocarbons

    Mobile source air toxic (MSAT) emissions from a direct injection spark ignition (DISI) passenger vehicle fueled with gasoline and liquid phase liquefied petroleum gas (LPG) were compared using a chassis dynamometer under several in-use vehicle driving conditions. For operation of a dedicated LPG-DI engine, low-pressure fuel systems were specially installed and various engine control parameters were recalibrated considering different chemical properties of LPG. A series of the National Institute of Environmental Research (NIER) modes for deter- mining the emission factors of in-use vehicles in Korea were chosen to quantify not only the regulated emissions with particles but also the unregulated emissions of carbonyls, BTEX, and PAHs from a DISI light-duty vehicle (LDV) with gasoline and LPG. The regulated and particle emissions of LPG-DI vehicles showed strong reduction, and the proportions of sub-23 nmparticleswere 32–35% in gasoline and 50–65% in LPG. The results revealed that the levels of theMSAT emissions from aDISI enginewere closely related to the driving patterns and the fuel prop- erties. A substantial reduction of regulated emissions, particulates, BTEX, and particle-bound PAH emissions was achieved from a LPG-DI vehicle in real driving conditions. Carbonyl compounds acetaldehyde and acrolein showed significant increment from a LPG-DI vehicle.

    © 2013 Elsevier B.V. All rights reserved.

    1. Introduction

    The implementation of the carbon dioxide (CO2) regulations and fuel economy (FE) standards has encouraged the deployment of energy efficient power-trains, greenhouse gas reducing alternative fuels, and vehicle electrification technologies in the transportation sector [1–6]. Advanced vehicle emission after-treatment technologies, meeting more stringent future emission regulations, will also play an important role in abating the harmful emissions aroundmetropolitan areas and in significantly improving urban air quality. However, steady growth in the number of vehicles on the road for the past few decades has been associated with a considerable increase in vehicle-related mo- bile source air toxic (MSAT) emissions that significantly adversely af- fect human health [7–12].

    Depending on fuel types and driving conditions, vehicles on the road emit various regulated and unregulated toxic components such as hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOx), aerosol particulates, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs) [13–19]. Nowadays, the use of a three-way catalyst (TWC) with conventional port fuel

    injection (PFI) gasoline and liquefied petroleum gas (LPG) engines can effectively reduce the engine-out gaseous emissions and can clear the strict emission standards that are determined by the established vehicle certification modes [20–26].

    The Ministry of Environment (MOE) in Korea has periodically monitored the emission inventories of the various fueled vehicles to improve the urban air quality and enforce future emission regula- tions. To construct the relative emission factors for each fueled vehicle, the National Institute of Environmental Research (NIER) modes that fully covered the driving patterns of vehicles nationwide were used. From the analysis of the air quality in metropolitan areas with real- world driving modes, the introduction of public transportation fuels for LPG passenger vehicles and compressed natural gas (CNG) buses have led to a significant reduction in PM, NOx, and VOCs compared to conventional liquid fuels worldwide [27–31].

    Although gasoline direct injection (GDI) engines with the TWC have the advantages of increased engine power and lower fuel con- sumption than PFI engines, the fuel wetting phenomena and heteroge- neous mixture formations during the transient operating conditions produce significant amounts of particulates compared to diesel particu- late filter (DPF)-equipped diesel engines. In particular, to meet the pro- posed particulate mass (PM) and nano-particle number (PN) emission regulations for GDI vehicles, comprehensive approaches have been un- dertaken on the engine control strategy, combustion chamber design,

    Fuel Processing Technology 119 (2014) 19–31

    ⁎ Corresponding author. Tel.: +82 2 3290 3368; fax: +82 2 926 9290. E-mail address: [email protected] (S. Park).

    0378-3820/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fuproc.2013.10.013

    Contents lists available at ScienceDirect

    Fuel Processing Technology

    j ourna l homepage: www.e lsev ie r .com/ locate / fuproc

    http://crossmark.crossref.org/dialog/?doi=10.1016/j.fuproc.2013.10.013&domain=pdf http://dx.doi.org/10.1016/j.fuproc.2013.10.013 mailto:[email protected] http://dx.doi.org/10.1016/j.fuproc.2013.10.013 http://www.sciencedirect.com/science/journal/03783820

  • high-pressure injection system, and gasoline particulate filter (GPF) in extreme cases [32–40]. In addition, many studies have reported that unregulated toxic exhaust emissions of VOCs are caused by par- tial oxidation during the combustion process or by evaporation of automotive fuels. The levels of MSATs are closely related with the fuel compositions and engine operating conditions in a spark- ignition engine [15–18,41–50].

    Currently, LPG cars with PFI fuel supply systems (liquid phase or gas phase) occupy about 13.4% (2.4 million) of the total number of in-use vehicles in Korea. As the LPG was injected in the intake port locations, the volumetric efficiency was reduced owing to the discharging the intake air by fast vaporization compared to gaso- line PFI engines [26,51–56]. When the liquid phase LPG fuel is di- rectly injected into the cylinders, more stable combustion and less particulate emissions as well as unregulated harmful emis- sions can be achieved through the homogeneous mixture forma- tion in the combustion process than in the GDI engine. Moreover, previous studies have shown that the engine performance of LPG- DI systems is comparable to that of the GDI engine owing to the higher heating value of the liquid phase LPG [25,57–61]. In partic- ular, several challenging obstacles need to be overcome to develop the dedicated LPG-DI engine, fuel supply system, and engine con- trol strategy considering the chemical and physical LPG fuel properties [24,25,42,51,58,59,62–64].

    The goal of our study is to evaluate the MSAT emission character- istics from a state-of-the-art GDI and a dedicated LPG-DI passenger vehicle. The vehicle driving conditions were selected as a series of the NIER modes that reflect real-world running patterns of vehicles in Korea. To study the relative emission factors on the gasoline- and LPG-fueled vehicle, besides the regulated gaseous and size- resolved PM emissions, unregulated emission components that are

    considered harmful species of substantially impact on human health were analyzed.

    2. Experimental apparatus

    2.1. Description of test vehicle and fuels

    A year 2010 model 2.4 L GDI vehicle with a common-rail system and side-mounted high-pressure injectors with a maximum injec- tion pressure of 150 bar was tested. A two-brick UCC combined with dual air gap exhaust manifold can meet the ultra-low emission vehicle (ULEV) emission standards. The fuel supply systems and var- ious engine control parameters of the base GDI engineweremodified for evaluating the exhaust emissions of the LPG-DI engine consider- ing the physical properties of the LPG fuel [25,34,40,51,58,59,62].

    Fig. 1 shows a schematic diagram of the 2.4 L DI engine and fuel supply system for gasoline and LPG fuels. The returnless-type low- pressure fuel supply system and high pressure pump for gasoline was converted into a return-type system for the LPG fuel. Compared to a direct current (DC) pump of 4.5 bar for the base GDI engine, a brushless direct current (BLDC) pump with a low-pressure regulator of 7.0 bar was installed for the LPG operation to improve the build- up time of the high pressure fuel in the common-rail and to eliminate the vapor-lock characteristics in the LPG fuel supply line. The gaso- line injection parameters of the injection pulse width and injection timing, which influence the engine performance during the start and aggressive transient operating conditions, were finely recalibrated for the dedicated LPG-DI transient vehicle operation [25,58,59,62]. When the vehicle was running with the LPG fuel, the function of a purge control solenoid valve (PCSV) installed between

    Fig. 1. Schematic diagram of the 2.4 L DI engine and fuel supply system for gasoline and LPG fuels.

    20 C.-L. Myung et al. / Fuel Processing Technology 119 (2014) 19–31

  • the intake manifold and the canister in the GDI vehicle was deactivated because of the closed-loop LPG fuel system.

    The LPG compositions,

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