Effect of piston shape design on the scavenging performance and mixture preparation in a two-stroke boosted uniflow scavenged direct injection gasoline engine

2020 ◽  
pp. 146808741990007 ◽  
Author(s):  
Xinyan Wang ◽  
Hua Zhao
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Shape Design ◽  
Injection Timing ◽  
Stoichiometric Mixture ◽  
Split Injection ◽  
Spark Plug ◽  
Direct Injection Gasoline Engine ◽  
Stroke Engine ◽  
Injection Strategies

Compared to a four-stroke engine, the two-stroke engine doubles firing frequency and has favourable power-to-weight or power-to-volume ratio as well as engine downsizing to improve the overall powertrain fuel economy. In order to overcome the shortcomings of the conventional cross-flow or loop scavenged two-stroke engines, a two-stroke boosted uniflow scavenged direct injection gasoline engine was designed and its performance was analysed. In this study, three-dimensional computational fluid dynamics simulations were performed to understand the impact of the piston shape design on the scavenging process, in-cylinder flow formation, turbulence level and subsequent fuel/air mixing process in the boosted uniflow scavenged direct injection gasoline engine. Both single injection and split injection strategies were investigated to study the interactions between piston designs and fuel injection strategies to achieve stoichiometric mixture around the spark plug. The results show that the optimised piston with the same opening timing for all scavenge ports could achieve much better scavenging performance than the baseline piston design. In particular, the shallow pistons, that is, Piston #1 and Piston #4, could produce stoichiometric mixture around the spark plug with relatively lower inhomogeneity and higher turbulence kinetic energy around top dead centre when implementing the split injection strategy with start of injection timing at 250/310 °CA.

Managing controlled auto-ignition combustion by injection on a direct-injection gasoline engine

2007 ◽  
Vol 221 (9) ◽  
pp. 1125-1137 ◽  
Author(s):  
Y Li ◽  
H Zhao ◽  
N Brouzos ◽  
B Leach
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Injection Timing ◽  
Split Injection ◽  
Gasoline Engines ◽  
Auto Ignition ◽  
Direct Injection Gasoline Engine ◽  
Early Closure ◽  
Exhaust Valves ◽  
Early Injection

Controlled auto-ignition (CAI) combustion in gasoline engines has great potential for reducing both NO x emissions and fuel consumption, but its application is still hindered by the lack of direct control of combustion phasing and by the limited CAI operation range. In this paper, the effect of injection timing and split injection on CAI combustion is presented in a single-cylinder direct-injection gasoline engine with an air-assisted injector. The CAI combustion was achieved by trapping some of the burned gases within the cylinder by using low-lift short-duration camshafts and early closure of the exhaust valves. During the experiments, the engine speed was varied from 1200 to 2400 r/min and the air-fuel ratio was altered from stoichiometric to the misfire limit. Both single and split injections were investigated at different injection timings and fuel quantities. The experimental results show that injection timing has an important effect on CAI combustion for single and split injections. Early injection produces faster and more stable combustion, less hydrocarbon and CO emissions, but very rapid heat release rates and higher NO x emissions. The CAI operation range could be extended significantly by early injection. Split injection gives even further extension of the CAI range in both stoichiometric and lean mixture operations. These results indicate that optimizing the injection timing and using split injection is an effective way to control and extend CAI operation in a direct-injection gasoline engine.

Two-Stroke Engine with Fuel Semi-Direct Injection Using FAI System

2011 ◽  
Vol 130-134 ◽  
pp. 796-799
Author(s):  
Ming Ming Wu ◽  
Yan Xiang Yang ◽  
Da Guang Xi ◽  
Ping Zhang ◽  
Zhong Guo Jin
Keyword(s):  
Gasoline Engine ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection System ◽  
Injection Timing ◽  
Fuel System ◽  
Power Performance ◽  
Fuel Injection Timing ◽  
Injection Quantity ◽  
Stroke Engine

This paper presents the feasibility of semi-direct injection on a 50cm3, two-stroke motorcycle gasoline engine, which is applied FAI semi-direct injection fuel system. The structure and fuel injection system is improved based on the original carburetor engine and the FAI injector is easily installed. The results of laboratory and drive test show that, compared with the original carburetor fuel system, through optimization calibration of fuel injection timing and injection quantity can improve power performance and fuel economy.

Effect of Conical Spray and Multi-Hole Spray on Gasoline Engine Mixture Formation and Combustion Performance Based on Different Injection Strategies

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Shengli Wei ◽  
Zhiqing Yu ◽  
Zhilei Song ◽  
Fan Yang ◽  
Chengcheng Wu
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Mixture Distribution ◽  
Gasoline Direct Injection ◽  
Injection Timing ◽  
Mixture Formation ◽  
Injection Strategy ◽  
Gdi Engine ◽  
The Difference ◽  
Injection Strategies

Abstract This article presents a numerical investigation carried out to determine the effects of second and third injection timing on combustion characteristics and mixture formation of a gasoline direct injection (GDI) engine by comparing conical spray against multihole spray. The results showed that at the engine 80% full load of 2000 r/min, the difference in mixture distribution between the two sprays was obvious with double and triple injection strategies. With the second injection timing from 140 deg CA delay to 170 deg CA, the in-cylinder pressure, the in-cylinder temperature, and the heat release rate of the conical spray increased by 20.8%, 9.8%, and 30.7% and that of the multihole spray decreased by 30.7%, 13.6%, and 37.8%. The delay of the injection time reduced the performance of the engine with the multihole spray, and the performance of the multihole spray was obviously in the simulation of the triple injection strategy. However, for the conical spray, the application of the triple injection strategy increased the temperature and the pressure compared with the double injection strategy.

Analysis of cycle-by-cycle variation in a direct injection gasoline engine using a laser-induced fluorescence technique

2003 ◽  
Vol 4 (2) ◽  
pp. 143-153 ◽  
Author(s):  
T Fujikawa ◽  
Y Nomura ◽  
Y Hattori ◽  
T Kobayashi ◽  
M Kanda
Keyword(s):  
Gasoline Engine ◽  
Direct Injection ◽  
Mixture Distribution ◽  
Fuel Mixture ◽  
Laser Induced Fluorescence ◽  
Injection Timing ◽  
Indicated Mean Effective Pressure ◽  
Cycle Variation ◽  
Spark Timing ◽  
Direct Injection Gasoline Engine

To analyse the cycle-by-cycle variation of combustion in a direct injection gasoline engine equipped with a fan-shape spray nozzle and operated with exhaust gas recirculation (EGR), the fuel mixture distribution was measured at a time of spark and during the combustion period by the laser-induced fluorescence (LIF) technique. It was found that in the case of advanced or retarded injection timing, the initial combustion period tends to extend and the indicated mean effective pressure (i.m.e.p.) becomes low when lean mixtures appear at the spark position and at the spark timing. This suggests that the cycle-by-cycle variation of combustion under these conditions is dominated by the fuel concentration at the spark position and spark timing. In contrast to this, for the best injection timing, which allows the lowest cycle-by-cycle variation, the i.m.e.p. fluctuation is affected not by the initial combustion period but by the main combustion period. The observation of LIF images revealed that the i.m.e.p. fluctuation at this condition is strongly correlated to the unburned mixture quantity at the side area of the piston cavity during the latter half of the combustion period. It was shown by a computational fluid dynamics (CFD) calculation that the combination of a uniform spray pattern and a compact cavity shape is effective to reduce the over-lean mixture region in the edge of the piston cavity, which is responsible for the cycle-by-cycle variation of combustion at the condition of best-tuned injection timing.

scholarly journals Analysis of mixture formation process in a two-stroke boosted uniflow scavenged direct injection gasoline engine

2017 ◽  
Vol 19 (9) ◽  
pp. 927-940 ◽  
Author(s):  
Xinyan Wang ◽  
Jun Ma ◽  
Hua Zhao
Keyword(s):  
Gasoline Engine ◽  
Single Injection ◽  
Direct Injection ◽  
Fuel Stratification ◽  
Mixture Preparation ◽  
Spark Plug ◽  
Start Of Injection ◽  
Flow Motion ◽  
Direct Injection Gasoline Engine ◽  
Cylinder Flow

The two-stroke engine has the great potential for aggressive engine downsizing and downspeeding because of its double firing frequency. For a given torque, it is characterized with a lower mean effective pressure and lower peak in-cylinder pressure than a four-stroke counterpart. In order to explore the potential of two-stroke cycle while avoiding the drawbacks of conventional ported two-stroke engines, a novel two-stroke boosted uniflow scavenged direct injection gasoline engine was proposed and designed. In order to achieve the stable lean-burn combustion in the boosted uniflow scavenged direct injection gasoline engine, the mixture preparation, especially the fuel stratification around the spark plug, should be accurately controlled. As the angled intake scavenge ports produce strong swirl flow motion and complex transfer between the swirl and tumble flows in the two-stroke boosted uniflow scavenged direct injection gasoline engine, the interaction between the in-cylinder flow motions and the direct injection and its impact on the charge preparation in the boosted uniflow scavenged direct injection gasoline engine are investigated in this study by three-dimensional computational fluid dynamics simulations. Both the single injection and split injections are applied and their impact on the mixture formation process is investigated. The start of injection timing and split injection ratio are adjusted accordingly to optimize the charge preparation for each injection strategy. The results show that the strong interaction between the fuel injection and in-cylinder flow motions dominates the mixture preparation in the boosted uniflow scavenged direct injection gasoline engine. Compared to the single injection, the split injection shows less impact on the large-scale flow motions. Good fuel stratification around the spark plug was obtained by the late start of injection timings at 300 °CA/320 °CA with an equal amount in each injection. However, when a higher tumble flow motion is produced by the eight scavenge ports’ design, a better fuel charge stratification can be achieved with the later single injection at start of injection of 320 °CA.

Effects of the injection timing on knock and combustion characteristics in dual-fuel dual-injection engines

2020 ◽  
Vol 234 (10-11) ◽  
pp. 2578-2591
Author(s):  
Jie Li ◽  
Changwen Liu ◽  
Rui Kang ◽  
Lei Zhou ◽  
Haiqiao Wei
Keyword(s):  
Gasoline Engine ◽  
Fuel Injection ◽  
Direct Injection ◽  
Engine Performance ◽  
Injection System ◽  
Dual Fuel ◽  
Injection Timing ◽  
Intensity Increase ◽  
Spark Plug ◽  
Spark Timing

To utilize ethanol fuel in spark ignition engines more efficiently and flexibly, a new ethanol/gasoline dual-direct injection concept in gasoline engine is proposed. Therefore, based on the dual-fuel dual-direct injection system, the effects of different injection timings and two injector positions on the characteristics of combustion were studied comprehensively, and the effects of different octane numbers and temperature stratifications on knock and combustion were explored. The results show that as for Position A (ethanol injecting toward spark plug), with the delay of injection timing, knock tendency and its intensity increase initially and then decrease due to the comprehensive effect of ethanol evaporation and fuel stratification; on the contrary, for Position B (ethanol injecting toward end-gas region), retarding the injection timing of ethanol can effectively reduce the knock propensity. As for the engine performance, a dual-direct injection performs best, especially the retarded injection timing of ethanol for Position A. It can be found that with the delay of the fuel injection timing, the torque first increases and then decreases. The brake-specific fuel consumption decreases initially and then increases at maximum brake torque spark timing.

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