Effect of Fuel Injection Timing During Negative Valve Overlap Period on a GDI-HCCI Engine

2018 ◽  
Author(s):  
Sok Ratnak ◽  
Jin Kusaka ◽  
Yasuhiro Daisho ◽  
Kei Yoshimura ◽  
Kenjiro Nakama
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Single Pulse ◽  
Injection Timing ◽  
Pulse Injection ◽  
Hcci Combustion ◽  
Fuel Injection Timing ◽  
Intake Stroke ◽  
Negative Valve Overlap ◽  
Valve Overlap

Gasoline Direct Injection Homogeneous Charge Compression (GDI-HCCI) combustion is achieved by closing early the exhaust valves for trapping hot residual gases combined with direct fuel injection. The combustion is chemically controlled by multi-point auto-ignition which its main combustion phase can be controlled by direct injection timing of fuel. This work investigates the effect of single pulse injection timing on a supercharged GDI-HCCI combustion engine by using a four-stroke single cylinder engine with a side-mounted direct fuel injector. Injection of primary reference fuel PRF90 under the near-stoichiometric-boosted condition is studied. The fuel is injected during negative valve overlap (NVO) or recompression period for fuel reformation under low oxygen concentration and the injection is retarded to intake stroke for the homogeneous mixture. It is found that the early fuel injection in NVO period advances the combustion phasing compared with the retarded injection in the intake stroke. Noticeable slower combustion rate from intake stroke fuel injection is obtained compared with the NVO injection due to charge cooling effect. Zero-dimensional combustion simulations with multiple chemical reaction mechanisms are simulated to provide chemical understanding from the effect of fuel injection timing on intermediate species generations. The species such as C2H4, C3H6, CH4, and H2 are found to be formed during the NVO injection period from the calculations. The effects of single pulse injection timings on combustion characteristics such pressure rise rate, combustion stability, and emissions are also discussed in this study.

Experimental and Numerical Analysis on the Influence of Direct Fuel Injection Into O2-Depleted Environment of a GDI-HCCI Engine

2020 ◽  
Author(s):  
Ratnak Sok ◽  
Jin Kusaka
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Injection Pressure ◽  
Single Pulse ◽  
Gasoline Direct Injection ◽  
Injection Timing ◽  
Rich Mixture ◽  
Intake Stroke ◽  
Shift Reaction ◽  
Direct Fuel Injection

Abstract Injected gasoline into the O2-depleted environment in the recompression stroke can be converted into light hydrocarbons due to thermal cracking, partial oxidation, and water-gas shift reaction. These reformate species influence the combustion phenomena of gasoline direct injection homogeneous charge compression ignition (GDI-HCCI) engines. In this work, a production-based single-cylinder research engine was boosted to reach IMEPn = 0.55 MPa in which its indicated efficiency peaks at 40–41%. Experimentally, the main combustion phases are advanced under single-pulse direct fuel injection into the negative valve overlap (NVO) compared with that of the intake stroke. NVO peak in-cylinder pressures are lower than that of motoring, which emphasizes that endothermic reaction occurs during the interval. Low O2 concentration could play a role in this evaporative charge cooling effect. This phenomenon limits the oxidation reaction, and the thermal effect is not pronounced. For understanding the recompression reaction phenomena, 0D simulation with three different chemical reaction mechanisms is studied to clarify that influences of direct injection timing in NVO on combustion advancements are kinetically limited by reforming. The 0D results show the same increasing tendencies of classical reformed species of rich-mixture such as C3H6, C2H4, CH4, CO, and H2 as functions of injection timings. By combining these reformed species into the main fuel-air mixture, predicted ignition delays are shortened. The effects of the reformed species on the main combustion are confirmed by 3D-CFD calculation, and the results show that OH radical generation is advanced under NVO fuel injection compared with that of intake stroke conditions thus earlier heat release and cylinder pressure are noticeable. Also, parametric studies on injection pressure and double-pulse injections on engine combustion are performed experimentally.

Effect of Fuel Injection Timing Relative to Ignition Timing on the Natural-Gas Direct-Injection Combustion

2001 ◽  
Author(s):  
Zuohua Huang ◽  
Seiichi Shiga ◽  
Takamasa Ueda ◽  
Nobuhisa Jingu ◽  
Hisao Nakamura ◽  
...  
Keyword(s):  
Heat Release ◽  
Late Stage ◽  
Equivalence Ratio ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection Timing ◽  
Ignition Timing ◽  
Fuel Injection Timing ◽  
Initial Stage ◽  
Wide Range

Abstract Effect of fuel injection timing relative to ignition timing on natural gas direct-injection combustion was studied by using a rapid compression machine. The ignition timing was fixed at 80 ms from the compression start. When the injection timing was relatively earlier (injection start at 60 ms), the heat release pattern showed slower burn in the initial stage and faster burn in the late stage, which is similar to that of flame propagation of a premixed gas. In contrast to this, when the injection timing was relatively later (injection start at 75 ms), the heat release rate showed faster burn in the initial stage and slower burn in the late stage, which is similar to that of diesel combustion. The shortest duration was realized at the injection end timing of 80 ms (the same timing as the ignition timing) over the wide range of equivalence ratio. The degree of charge stratification and the intensity of turbulence generated by the fuel jet is considered to cause these behaviors. Earlier injection leads to longer duration of the initial combustion, whereas the later injection does longer duration of the late combustion. Earlier injection showed relatively lower CO emission while later injection produces relatively lower NOx emission. It was suggested that earlier injection leads to lower mixture stratification combustion and later injection leads to higher mixture stratification combustion. Combustion efficiency maintained high value over the wide range of equivalence ratio.

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.

scholarly journals Numerical investigation into the effect of direct fuel injection on thermal stratification in HCCI engine

2017 ◽  
Vol 169 (2) ◽  
pp. 137-140
Author(s):  
Michał GĘCA ◽  
Jacek HUNICZ ◽  
Piotr JAWORSKI
Keyword(s):  
Combustion Chamber ◽  
Thermal Stratification ◽  
Fuel Injection ◽  
Injection Timing ◽  
Ignition Timing ◽  
Hcci Engine ◽  
Auto Ignition ◽  
Negative Valve Overlap ◽  
Valve Overlap ◽  
Direct Fuel Injection

Despite the fact that HCCI engines are distinguished by mixture homogeneity, some degree of stratification always appears inside a combustion chamber. It is especially applied to residual effect engines utilizing negative valve overlap. Mixture stratification is a result of the imperfect mixing of fresh air with trapped residuals. Direct fuel injection introduces stratification as well, due to fuel vaporization. As a consequence, the temperature within the combustion chamber is uneven. Thermal stratification affects auto-ignition timing and combustion evolution in a high extent. The purpose of this study was to evaluate a degree of thermal stratification in HCCI engine utilizing negative valve overlap. Investigations were performed using three-dimensional CFD model of the combustion system, made by using AVL FIRE software. Simulations were realized for various timings of fuel injection into the cylinder. It was found that fuel injection timing had a significant effect on the thermal stratification and resulting auto-ignition timing.

Characteristics of Lean and Stoichiometric Combustion of Compressed Natural Gas in a Direct Injection Engine

2011 ◽  
Vol 110-116 ◽  
pp. 357-369 ◽  
Author(s):  
Raja Shahzad ◽  
P. Naveenchandran ◽  
A. Rashid ◽  
Amir Aziz
Keyword(s):  
Fuel Injection ◽  
Direct Injection ◽  
Engine Performance ◽  
Initial Mixture ◽  
Combustion Characteristics ◽  
Injection Timing ◽  
Direct Injection Engine ◽  
Fuel Injection Timing ◽  
Initial Stage ◽  
Air Mixing

This paper discusses the combustion characteristics of CNG under lean and stochiometric conditions in a direct injection engine. The experiments were carried out on a dedicated CNG-Direct Injection engine with 14:1 compression ratio. Combustion characteristics of CNG have been investigated on various injection timings. Injection timing of the fuel injection timing had significant effects on the engine performance, combustion and emissions. The effects became more significant when injection timing was retarded. Injection timing was set after the closing of intake valve and experiments are conducted at 0% and 50% load conditions. Lean stratified operation experiences faster combustion compared to that of stochiometric. In lean stratified operation, there were fast burn rates at the initial stage and slower burning at the later stage. Whereas in stochiometric conditions there is a slightly slower burn at the initial stage and a moderately faster burn at the later stage. The faster initial combustion in lean stratified operation might be due to rapid burn of the initial mixture due to higher turbulence, while a slower burn in the later stage due to diffusion. In contrary to that in stochiometric operations the initial burn is slightly slower, due to moderately strong turbulence and a faster burn due to moderately proceeding mixture. Thus the main effect of fuel injection timing can be explained by the fuel air mixing and the turbulence produced.

Experimental and Simulation Study of Fuel Injection Timing, Pressure and EGR for Lower Exhaust Emissions From Diesel HCCI Combustion

2009 ◽  
Author(s):  
S. Juttu ◽  
S. S. Thipse ◽  
N. V. Marathe ◽  
M. K. Gajendra Babu
Keyword(s):  
Simulation Study ◽  
Fuel Injection ◽  
Injection Pressure ◽  
Exhaust Emissions ◽  
Injection Timing ◽  
Nox Emissions ◽  
Hcci Combustion ◽  
Fuel Injection Timing ◽  
Start Of Injection ◽  
Wide Range

The objective of this work is to study the effect of different control parameters viz. EGR, fuel injection pressure and start of injection timing on exhaust emissions from diesel fueled HCCI combustion concept. A 4-cylinder LCV engine has been selected for experiments and FIRE 3D CFD software was used for simulation study. The basic idea of the simulation study is to find the suitable EGR ratio to run the engine on HCCI combustion mode so as to avoid any damage to the engine during testing. From simulation study, it was observed that the minimum EGR required for running the engine at 5.6 bar BMEP @ 2500 rpm in HCCI mode is approximately 45%. The trends of simulation results viz. soot and NOx emissions are closely following the experiments. The experiments were conducted at different loads at 2500 rpm and EGR varied from 0% to 60%. With increased EGR ratio, soot bump was observed at 50%, 75% and 100%. The BTE dropped to 24.5% from 33.5%. The effect of fuel injection pressures (750bar, 1000bar and 1500bar) were studied to improve the BTE and to control soot bump over a wide range injection timings EGR ratio. Detailed experiments were conducted at 2.8 bar BMEP @ 2500 rpm to study simultaneous reduction of NOx, SOOT, UHC and CO emissions from diesel HCCI combustion. At injection pressure (1500 bar), advanced fuel injection timing and high EGR ratio, the soot CO and THC emissions were reduced significantly without penalty on NOx emissions. The BTE was improved from 24.5% to 31% against 33.5% of convention diesel combustion.

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