An Experimental Investigation of Early Flame Development in an Optical Spark Ignition Engine Fueled With Natural Gas

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Cosmin E. Dumitrescu ◽  
Vishnu Padmanaban ◽  
Jinlong Liu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Combustion Engine ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Piston Bowl ◽  
Pressure Trace ◽  
Flame Development ◽  
Flame Region

Improved internal combustion engine simulations of natural gas (NG) combustion under conventional and advanced combustion strategies have the potential to increase the use of NG in the transportation sector in the U.S. This study focused on the physics of turbulent flame propagation. The experiments were performed in a single-cylinder heavy-duty compression-ignition (CI) optical engine with a bowl-in piston that was converted to spark ignition (SI) NG operation. The size and growth rate of the early flame from the start of combustion (SOC) until the flame filled the camera field-of-view were correlated to combustion parameters determined from in-cylinder pressure data, under low-speed, lean-mixture, and medium-load conditions. Individual cycles showed evidence of turbulent flame wrinkling, but the cycle-averaged flame edge propagated almost circular in the two-dimensional (2D) images recorded from below. More, the flame-speed data suggested different flame propagation inside a bowl-in piston geometry compared to a typical SI engine chamber. For example, while the flame front propagated very fast inside the piston bowl, the corresponding mass fraction burn was small, which suggested a thick flame region. In addition, combustion images showed flame activity after the end of combustion (EOC) inferred from the pressure trace. All these findings support the need for further investigations of flame propagation under conditions representative of CI engine geometries, such as those in this study.

An Experimental Investigation of Early Flame Development in an Optical SI Engine Fueled With Natural Gas

2017 ◽  
Author(s):  
Cosmin E. Dumitrescu ◽  
Vishnu Padmanaban ◽  
Jinlong Liu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Turbulent Flame ◽  
The United States ◽  
Si Engine ◽  
Ic Engine ◽  
Piston Bowl ◽  
Pressure Trace ◽  
Flame Development ◽  
Flame Region

Improved internal combustion (IC) engine simulations of natural gas (NG) combustion under conventional and advanced combustion strategies have the potential to increase the use of NG in the transportation sector in the United States. This study focused on the physics of turbulent flame propagation. The experiments were performed in a single-cylinder heavy-duty compression-ignition (CI) optical engine with a bowl-in piston that was converted to spark ignition (SI) NG operation. The size and growth rate of the early flame from the start of combustion until the flame filled the camera field-of-view were correlated to combustion parameters determined from in-cylinder pressure data, under low-speed, lean-mixture, and medium-load conditions. Individual cycles showed evidence of turbulent flame wrinkling, but the cycle-averaged flame edge propagated almost circular in the 2D images recorded from below. More, the flame-speed data suggested a different flame propagation inside a bowl-in piston geometry compared to a typical SI engine chamber. For example, while the flame front propagated very fast inside the piston bowl, the corresponding mass fraction burn was small, which suggested a thick flame region. In addition, combustion images showed flame activity after the end of combustion inferred from the pressure trace. All these findings support the need for further investigations of flame propagation under conditions representative of CI engine geometries, such as those in this study.

Optical analysis of flame inception and propagation in a lean-burn natural-gas spark-ignition engine with a bowl-in-piston geometry

2019 ◽  
Vol 21 (9) ◽  
pp. 1584-1596 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin Emil Dumitrescu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Diesel Engines ◽  
Pressure Rise ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Expansion Velocity ◽  
Cylinder Pressure ◽  
Lean Burn ◽  
Piston Bowl

Heavy-duty diesel engines can convert to lean-burn natural-gas spark-ignition operation through the addition of a gas injector in the intake manifold and of a spark plug in place of the diesel injector to initiate and control combustion. However, the combustion phenomena in such converted engines usually consist of two distinct stages: a fast-burning stage inside the piston bowl followed by a slow-burning stage inside the squish area. This study used flame luminosity data and in-cylinder pressure measurements to analyze flame propagation inside a bowl-in-piston geometry. The experimental results showed a low coefficient of variation and standard deviation of peak cylinder pressure, moderate rate of pressure rise, and no knocking for the lean-burn (equivalence ratio 0.66), low-speed (900 r/min), and medium-load (6.6 bar IMEP) operating condition. Flame inception had a strong effect on the flame expansion velocity, which increased fast once the flame kernel established, but it reduced near the bowl edge and the entrance of the narrow squish region. However, the burn inside the bowl was very fast. In addition, the long duration of burn inside the squish indicated a much lower flame propagation speed for the outside-the-bowl combustion, which contributed to a long decreasing tail in the apparent heat release rate. Furthermore, cycles with fast flame inception and fast burn inside the bowl had a similar end of combustion with cycles with delayed flame inception and then a retarded burn inside the bowl, which indicated that the combustion inside the squish region determined the combustion duration. Overall, the results suggested that the spark event, the flame development inside the piston bowl, and the start of the second combustion stage affected the phasing and duration of the two combustion stages, which (subsequently) can affect engine efficiency and emissions of diesel engines converted to a lean-burn natural-gas spark-ignition operation.

scholarly journals Effect of Spark Advance on a Gas Run Automotive Spark Ignition Engine

2010 ◽  
pp. 42-49 ◽  
Author(s):  
Md Ehsan
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Chemical Engineering ◽  
Engine Performance ◽  
Spark Ignition ◽  
Constant Load ◽  
Combustion Characteristics ◽  
Spark Ignition Engine ◽  
Optimum Performance ◽  
Automotive Engine

Petrol engines can run on natural gas, with little modification. The combustion characteristics of naturalgas is different from that of petrol, which eventually affects the engine performance. The performance of atypical automotive engine was studied running on natural gas, firstly at a constant speed for various loadsand then at a constant load for a range of speeds and results were compared with performance using petrol.Variation of the spark advance, consisting of centrifugal and vacuum advance mechanisms, wasinvestigated. Results showed some reduction in power and slight fall of efficiency and higher exhausttemperature, for natural gas. The air-fuel ratio for optimum performance was higher for gas than for petrol.This variation in spark requirement is mainly due to the slower speed of flame propagation for natural gas.For both the cases, the best power spark advance for natural gas was found to have higher values thanpetrol. This issue needs to be addressed during retrofitting petrol engines for running on natural gas.Journal of Chemical Engineering Vol.ChE 24 2006 42-49

Observation of Flame Propagation in a Heavy-Duty Natural-Gas Lean Burn Spark-Ignition Engine

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Low Cost ◽  
Turbulent Flame ◽  
Propagation Speed ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Heavy Duty ◽  
Lean Burn ◽  
Local Flow

Abstract Natural gas (NG) is an alternative combustible fuel for the transportation sectors due to its clean combustion, small carbon footprint, and, with recent breakthroughs in drilling technologies, increased availability and low cost. Currently, NG is better suited for spark-ignited (SI), as a gasoline replacement in conventional SI engines or as a diesel replacement in diesel engines converted to SI operation. However, the knowledge on the fundamentals of NG flame propagation at conditions representative of modern engines (e.g., at higher compression ratios and/or lean mixtures) is limited. Flame propagation inside an engine can be achieved by replacing the original piston with a see-through one. This study visualized flame activities inside the combustion chamber of an optically-accessible heavy-duty diesel engine retrofitted to NG SI operation to increase the understanding of combustion processes inside such converted engines. Recordings of flame luminosity throughout the combustion period at lean-burn operating conditions indicated that the fully-developed turbulent flame formed from several smaller-scale kernels. These small kernels varied with shapes and locations due to different flow motion around the spark location (including the effect of spark electrodes on the local flow separation), different local temperature, or different energy released in these regions. In addition, the turbulent flame was heavily wrinkled during propagation, despite it was grown from a relatively-circular kernel. Moreover, the intake swirl accelerated the flame propagation process while rotating the turbulent flame during its development. Furthermore, the flame propagation speed reduced dramatically when entering the squish region, while the direction from which the flame first touched the bowl edge changed with individual cycles. The results can help the CFD community to better develop RANS and/or LES simulations of such engines under lean-burn operating conditions.

311 Turbulent flame propagation in a Spark Ignition Engine

2000 ◽  
Vol 005.1 (0) ◽  
pp. 101-102
Author(s):  
Sadami YOSHIYAMA ◽  
Eiji TOMITA ◽  
Zhong ZHANG ◽  
Mitsuo NISHIDA
Keyword(s):  
Flame Propagation ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Spark Ignition Engine

A semi-empirical laminar-to-turbulent flame transition model coupled with G equation for early flame kernel development and combustion in spark-ignition engines

2019 ◽  
pp. 146808741986474 ◽  
Author(s):  
Seunghwan Keum ◽  
Guangfei Zhu ◽  
Ronald Grover ◽  
Wei Zeng ◽  
Christopher Rutland ◽  
...  
Keyword(s):  
Turbulent Flame ◽  
Transition Process ◽  
Spark Ignition ◽  
Transition Function ◽  
Spark Ignition Engine ◽  
Navier Stokes ◽  
Flame Kernel ◽  
Eddy Simulation ◽  
Flame Development ◽  
Semi Empirical

It has been reported that early combustion in a spark-ignition engine determines the subsequent combustion. Also, the early combustion has a very strong correlation with cycle-to-cycle variability, which limits engine operating range. As such, accurate modeling of the early flame development is very important in accurate simulation of spark-ignition engine combustion. During the early flame development, the flame kernel, initiated by spark, grows initially at laminar flame speed. As the kernel grows, the flame surface wrinkles due to surface instability and interacts with the flow turbulence as the flame transitions from laminar to turbulent flame. In this study, a semi-empirical model is proposed to simulate the laminar-to-turbulent flame transition process during early spark-ignition combustion. A hyperbolic tangent function was used to emulate the laminar-to-turbulent flame speed transition process. The proposed transition function was evaluated during early flame kernel development for both Reynolds-averaged Navier–Stokes and large eddy simulation models against combustion analysis data from high-speed optical particle image velocimetry. Difference in Reynolds-averaged Navier–Stokes and large eddy simulation transition function was analyzed and discussed.

Sign in / Sign up

Export Citation Format

Share Document