SOOT DEVELOPMENT IN AN OPTICAL DIRECT INJECTION SPARK IGNITION ENGINE FUELED WITH ISOOCTANE

Fangxi Xie,Miaomiao Zhang,Yongzhen Wang,Yan Su,Wei Hong,Peng Cheng 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.2

To better understand the formation and evolution processes of soot, the two-color laser induced incandescence diagnostic method was applied on a single cylinder optical direct injection spark ignition engine. Soot volume fraction was measured, and soot distribution was imaged as cyclic fuel quantity changes. The results show that 45.5 mg/cycle generates the most soot at the same measure plane. Pool fire dominates the formation of soot in the tested engine and generates more soot on the top surface of the piston near the injector. In-cylinder soot increases until 42°CA ATDC and then reduces due to oxidation. Pool fire continues through the expansion stroke till 52°CA ATDC, and then soot cloud gathers near the 10 mm plane. After 82°CA ATDC, in-cylinder soot basically in equilibrium, and residual soot moves follow the in-cylinder flow randomly and evenly distributes within the whole combustion chamber. With increasing cyclic fuel quantity, particles number concentration gradually increases and their distribution present dual-peak shape. In detail, 45.5 mg/cycle emits the most accumulation mode particles while 52 mg/cycle emits the most nucleation mode particles.

EXPERIMENTAL STUDY OF PARTICULATE EMISSION CHARACTERISTICS FROM A GASOLINE DIRECT INJECTION ENGINE DURING STARTING PROCESS

Yan Su,Fangxi Xie,Wei Hong,Xiaoping Li,Tingting Hu 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.2

The engine starting process presents high particulate emissions in exhaust. This study gives a systematic investigation on particulate emission characteristics, including particulate matter (PM) mass, soluble organic fraction (SOF) mass, C10-C26 n-Alkanes and particle-bound polycyclic aromatic hydrocarbons (PAHs), that have been emitted from a gasoline direct injection (GDI) engine measured by Gas chromatography–mass spectrometry during starting period. The results show that particulate emissions under the warm coolant start condition decline dramatically compared with the cold start condition. 90 % of particulate number (PN) emitted during the cold and warm start periods generally are nucleation-mode particles. Over 50 % PM mass and PAHs emissions are emitted in the first 0−13 s stage. SOF mass accounts more than 60 % in PM mass emissions, especially under the warm coolant start condition. Some C23-C26 n-Alkanes are detected under the cold start condition which demonstrates that partial particulate composition directly comes from lubricant. The concentration of the two ring PAHs is the lowest among PAHs while the four to six ring PAHs are higher under the cold start operation. The toxicity of PAHs which is evaluated by Benzo(a)pyrene equivalent toxicity (BEQ) value of the total PAHs emissions shows a decline of 66.83 % under the warm start condition.

EXPERIMENTAL INVESTIGATION OF IMPACTS OF INJECTION TIMING AND PRESSURE ON COMBUSTION AND PARTICULATE MATTER EMISSION IN A SPRAY-GUIDED GDI ENGINE

Miaomiao Zhang,Wei Hong,Fangxi Xie,Yan Su,Liwei Han,Bin Wu 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.3

A detailed investigation of the impact of injection timing and injection pressure on combustion and particles of a spray-guided GDI engine was conducted, under different engine operating conditions. The results indicated that, more proportion of large particles were emitted when increasing engine load, and the peak of accumulation mode particles moved toward smaller size when rising engine speed. With retarding the injection timing, the in-cylinder pressure and heat release rate rose first and then dropped at 2000 rpm, but they continuously rose at lower or higher speed conditions. The total particles concentration curves at all cases showed a trend of U-shape, and the corresponding timing of the lowest particles concentration advanced as the engine speed or load increased. The minimum value of emitted particles first rose and then fell when increasing load at 2000 rpm conditions, and it continuously rose when increasing speed at 40 Nm conditions. Generally, injection pressure did no sensitively affect combustion process except that it showed a relatively strong impact at low load conditions. However, particulate matter could be effectively inhibited by elevating fuel pressure from 5.5 to 11.5 MPa at all cases. In detail, the total particles concentration continuously fell at low speed and mid speed-high load cases, but it showed a rose trend when further increase fuel injection pressure at mid speed-low load and high-speed conditions.

PARTICULATE MATTER AND PARTICLE-BOUND PAHS EMISSIONS FROM GASOLINE DIRECT INJECTION (GDI) ENGINE WITH METHANOL-GASOLINE BLENDED FUEL DURING START

Wei Hong,Chao Yuan,Fangxi Xie,Yan Su,Jing Chen 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.4

The effects of coolant’s temperature on emissions of particulate matters (PM) and particle-bound polycyclic aromatic hydrocarbons (PAHs) from a gasoline direct injection (GDI) engine were studied during the start process using gasoline (M0) and gasoline mixed with methanol in 15 % volume (M15). The engine worked at a certain idle speed automatically under different coolant’s temperature conditions after successful start. The experimental data was recorded from 0 to 40 seconds during the start. Results indicated that, there are significant differences in PM and particle-bound PAHs emissions between cold and warm start conditions. Particulate size distribution was measured with the Engine Exhaust Particle Sizer (EEPS) 3090. Compared with M0 fuel, the PM emission of M15 fuel decreased significantly, especially nucleation-mode particulate emission. The mass emission of PM was measured using the Gravimetric method. A same variation trend in PM mass emissions can be inferred for both fuels, i.e. it decreases while the coolant’s temperature increases. Compared with M0 fuel, the PM mass with M15 fuel reduces by 80 % at 20 oC coolant’s temperature. Agilent 7000B GC-QQQ was used to provide both qualitative and quantitative analysis on PAHs. The application of M15 fuel reduces the concentrations of most PAH species compared with M0 fuel, except those with smaller aromatic rings. In addition, Benzo(a)pyrene equivalent toxicity (BEQ) is calculated to evaluate the toxicity of PAHs emissions. The toxicity decreases when the GDI engine starts with higher coolant’s temperature or with M15 fuel.

VALVE MOTION CHARACTERISTICS AND APPLICATION ON ENGINE BASED ON A NEW VARIABLE VALVE ACTUATION SYSTEM

You Zhou,Weihong Zhou,Fangxi Xie,Yu Liu,Xiaoping Li,Xun Gong 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.1

A new mechanical-hydraulic variable valve actuation (VVA) system was developed and a thin-wall orifice velocity control system were analyzed. Meanwhile, influence of speed, needle valve overflow area, oil temperature and oil supply pressure on valve motion characteristics were explored, as well as the VVA system have been applied on a single-cylinder engine preliminary. By the VVA system, valve lifts can be adjusted from maximum of 8.7 mm to fully closing. Valve seating velocity decreased with orifice diameter reducing. Seating velocity can be maintained below 0.5 m/s with 0.8 mm diameter of thin-wall orifice and 3 mm check valve moving distance. Besides that, velocity control system also can help improve the coefficient of cyclic variation of maximum valve lift. Except for the needle valve closing state, valve lift decreased with oil temperature increasing and operating speed reducing under the same needle valve state. Oil supply pressure hardly had no influence on valve lifts, but delayed valve opening timing with pressure decreasing. Thin-wall orifice seating velocity control system was not sensitive to variable oil temperature and supply pressure. Compared with conventional engine, adjusting intake valve by VVA system under un-throttle internal EGR strategy, can improve BSFC and NOX emissions significantly about 13.8 % and 19.8 % on 6 bar IMEP.

EFFECT OF METHANOL ADDITION ON COMBUSTION AND EMISSIONS CHARACTERISTICS ON A TURBOCHARGED GDI ENGINE

Hong Chen,Jiakun Du,Yuhuai Li,Wenfeng Zhan,Jian Wu,Fangxi Xie,Guangquan Wu 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5

To enrich the knowledge and understanding of the application effect of methanol fuel in the current engine, the influence of methanol-gasoline blended fuel containing 10 %, 20 % and 30 % methanol addition (M10, M20 and M30) on the engine performance, combustion and emissions were studied on a turbocharged and direct injection engine with original control system and control parameters. The results showed that at the conditions with low speed, the peak heat release rate and cylinder pressure were decreased by the use of blended fuel while it shown an increased peak combustion pressure and heat release rate at high speed. Meanwhile, the combustion center of blended fuel was obviously different from gasoline and its optimal value, and the combustion variation was increased at low load. The fuel consumption lifted continuously with the increase of methanol addition ratio, and the equivalent fuel consumption of M10 and M20 also was higher than that of pure gasoline. For NOx emissions, although it has been improved continuously for M10, M20 and M30 under the higher engine load, the higher emissions were obtained for M10 and M20 at lower load. In addition, compared with gasoline fuel, the whole particle distribution curve and number concentration was significantly deteriorated with methanol addition.

POTENTIALS OF AIR-EGR DILUTION FOR IMPROVING PERFORMANCE OF A HIGH COMPRESSION RATIO SPARK-IGNITION ENGINE FUELED WITH METHANOL

Lai Kaichang,Chen Hong,Du Jiakun,Zhan Wenfeng,Li Yuhuai,Xie Fangxi 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.4

The effects of air and exhaust gas recirculation (EGR) dilution of a spark ignition engine fueled with methanol under different loads were studied by experiment in this paper. Such as ignition delay, combustion center (CA50), IMEP, break thermal efficiency (BTE) and other parameters were investigated to assess the combustion performance. And discussed in depth the balance between NOx emissions and economic performance represented by brake specific fuel consumption (BSFC). The results showed that combustion progress such as ignition delay, combustion duration and CA50 were more sensitive on the changes of EGR, introducing EGR under the same dilution rate prolonged combustion process. Air-EGR dilution showed the best improvement of IMEP and break thermal efficiency, except the optimal area, increasing EGR rate will decreased IMEP and BTE. Air-EGR dilution strategy showed the best improvement on BSFC than air dilution than EGR dilution. Under light load and high load, when the lowest BSFC was obtained, NOx emissions were less than 0.5 g/kWh with air-EGR dilution strategy.