An Experimental Investigation on the Combustion Process of a Simulated Turbocharged Spark Ignition Natural Gas Engine Operated on Stoichiometric Mixture

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Hailin Li ◽  
Timothy Gatts ◽  
Shiyu Liu ◽  
Scott Wayne ◽  
Nigel Clark ◽  
...  
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Combustion Process ◽  
Propagation Speed ◽  
Spark Ignition ◽  
Boost Pressure ◽  
Stoichiometric Mixture ◽  
Process Data ◽  
Intake Pressure ◽  
Flame Propagation Speed

This research investigated the combustion process of an AVL Model LEF/Volvo 5312 single cylinder engine configured to simulate the operation of a heavy-duty spark ignition (SI) natural gas (NG) engine operated on stoichiometric mixture. The factors affecting the combustion process that were examined include intake pressure, spark timing (ST), and the addition of diluents including nitrogen (N2) and carbon dioxide (CO2) to the NG to simulate low British thermal unit (BTU) gases. The mixing of diluents with NG is able to slow down the flame propagation speed, suppress the onset of knock, and allow the engine to operate on higher boost pressure for higher power output. The addition of CO2 was more effective than N2 in suppressing the onset of knock and slowing down the flame propagation speed due to its high heat capacity. Boosting intake pressure significantly increased the heat release rate (HRR) evaluated on J/°CA basis which represents the rate of mass of fuel burning. However, its impact on the normalized HRR evaluated on %/°CA basis, representing the flame propagation rate, was relatively mild. Boosting the intake pressure from 1.0 to 1.8 bar without adding diluents increased the peak HRR to 1.96 times of that observed at 1.0 bar. The increase was due to the burning of more fuel (about 1.8 times), and the 12.9% increase in the normalized HRR. The latter was due to the shortened combustion duration from 23.6 to 18.2 °CA, a 22.9% reduction. The presence of 40% CO2 or N2 in their mixture with NG increased the peak cylinder pressure (PCP) limited brake mean effective pressure (BMEP) from 17.2 to about 20.2 bar. The combustion process of a turbocharged SI NG engine can be approximated by referring to the HRR measured under a naturally aspirated condition. This makes it convenient for researchers to numerically simulate the combustion process and the onset of knock of turbocharged SI NG engines using combustion process data measured under naturally aspirated conditions as a reference.

A Comparative Study of Methane Combustion Characteristics with Different Additions in an Optical SI Engine

2021 ◽  
Author(s):  
Lin Chen ◽  
Xiao Zhang ◽  
Ren Zhang ◽  
Wanhui Zhao
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Power Output ◽  
High Speed ◽  
Propagation Speed ◽  
Pressure Oscillation ◽  
Methane Combustion ◽  
Natural Gas Engines ◽  
Auto Ignition ◽  
Flame Propagation Speed

Abstract Natural gas is a promising fuel for IC engines with minimal modification, whereas its low power output and slow flame propagation speed remain a challenge for automobile manufacturers. To find a method of improving the natural gas engines, methane combustion with different additions was comparatively studied. High-speed direct photography and simultaneous pressure were performed to capture detailed combustion evolutions. First, the results of pure methane combustion confirm its good anti-knock property, and no pressure oscillation occurs even there is an end-gas auto-ignition, indicating that high compression ratio and high boosting are effective ways to improve the performance of natural gas engines. Second, adding heavy hydrocarbons can greatly improve engines' power output, but engine knock should be considered if low anti-knock fuel was used. Third, as a carbon-free and gaseous fuel, hydrogen addition can not only increase methane flame propagation speed but reduce cyclic variations. However, a proper fraction is needed under different load conditions. Last, oxygen-enriched combustion is an effective way to promote methane combustion. The heat release becomes faster and more concentrated, specifically, the flame propagation speed can be increased by more than 2 times under 27% oxygen concentration condition. The current study shall give insights into improving natural gas engines' performance.

Effects of flame propagation speed on knocking and knock-limited combustion in a downsized spark ignition engine

Fuel ◽  
2021 ◽  
Vol 293 ◽  
pp. 120407
Author(s):  
Xumin Zhao ◽  
Zan Zhu ◽  
Zunqing Zheng ◽  
Zongyu Yue ◽  
Hu Wang ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Propagation Speed ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Flame Propagation Speed

Twin-Peak Heat Release Phenomenon Inside a Heavy-Duty Diesel Engine Retrofitted to Natural-Gas Spark Ignition

2019 ◽  
Author(s):  
Jinlong Liu ◽  
Cosmin E. Dumitrescu ◽  
Christopher Ulishney
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Heat Release ◽  
Energy Release ◽  
Flame Propagation ◽  
Combustion Process ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Heavy Duty ◽  
Double Peak

Abstract Existing compression ignition engines can be modified to spark ignition configuration to increase the use of natural gas in the heavy-duty transportation sector. A better understanding of the premixed natural gas combustion inside the original diesel chamber (i.e., flat-head-and-bowl-in-piston) will help improve the conversion process and therefore accelerate the diesel engine conversion. Previous studies indicated that the burning process in such engines is a two-stage combustion with a fast burning inside the bowl and a slower burning inside the squish. This paper used experimental and numerical results to investigate the combustion process at a more advanced spark timing representative of ultra-lean medium-load operation, which placed most of the combustion inside the compression stroke. At such operating conditions, the high turbulence intensity inside the squish region accelerated the flame propagation inside the squish region to the point that the burn inside the bowl separated less from that inside the squish region. However, several individual cycles produced a double-peak energy-release with the peak locations closer to the only one heat release peak seen in the average cycle. Moreover, RANS CFD simulations indicated that the time at which the flame entered the squish region was near the peak location of the energy-release process for the conditions investigated here. As a result, the data suggests that the double-peak seen in the apparent heat release rate was the result of the cycle-by-cycle variation in the flame propagation.

Experimental Setup of Combustion Visualization Inside a Heavy-Duty Diesel Engine Converted to Natural-Gas Spark-Ignition Operation

2019 ◽  
Author(s):  
Vishnu Padmanaban ◽  
Jinlong Liu ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Diesel Engine ◽  
Natural Gas ◽  
Flame Propagation ◽  
Combustion Process ◽  
Spark Ignition ◽  
Experimental Setup ◽  
Engine Operation ◽  
Spark Plug ◽  
Efficient Combustion ◽  
Heavy Duty Diesel

Abstract The conversion of existing diesel engines to natural-gas (NG) spark-ignition (SI) operation would reduce U.S. dependence on oil imports and curtail greenhouse gas emissions. As the literature shows that the combustion process in such converted engines is different compared to that in conventional SI engines, understanding the effects of the diesel geometry and fuel effects on the in-cylinder flame propagation is important for optimizing engine operation. This paper describes the experimental setup that allowed the visualization of combustion phenomena inside a single-cylinder diesel engine converted to single-fuel NG spark-ignition operation through the addition of a spark plug and a low-pressure gas injector. The synchronization between the piston position and image acquisition was done using over-the-counter electronic components. While the setup could not visualize flame propagation inside the squish region, the combustion images, together with the pressure-based analysis, help understand the characteristics of lean NG flame propagation inside a diesel geometry, which is an important for designing a highly-efficient combustion process.

Flame Propagation Speed of CO2Diluted Hydrogen-Enriched Natural Gas and Air Mixtures

2009 ◽  
Vol 23 (10) ◽  
pp. 4957-4965 ◽  
Author(s):  
Min Ji ◽  
Haiyan Miao ◽  
Qi Jiao ◽  
Qian Huang ◽  
Zuohua Huang
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Propagation Speed ◽  
Flame Propagation Speed

Ignition Dynamics in an Annular Combustor With Gyratory Flow Motion

2018 ◽  
Author(s):  
Chenran Ye ◽  
Gaofeng Wang ◽  
Yuanqi Fang ◽  
Chengbiao Ma ◽  
Liang Zhong ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Velocity Component ◽  
Thermal Power ◽  
Propagation Speed ◽  
Circumferential Velocity ◽  
Bulk Velocity ◽  
Ignition Process ◽  
Flow Motion ◽  
Annular Combustor ◽  
Flame Propagation Speed

In concepts of integrated design of combustor and turbine, an annular combustor model is developed and featured with multiple oblique-injecting swirling injectors to introduce gyratory flow motion in the combustion chamber. The ignition process is experimentally investigated to study the effects of introducing circumferential velocity component Uc to the light-round sequence. Experiments are carried out with premixed propane/air mixture in ambient conditions. The light-round sequence is recorded by a high-speed camera, which provides detailed flame azimuthal positions during the sequence and gives access to the light-round time τ and the circumferential flame propagation speed Sc. The results have also been compared with that obtained from a straight-injecting annular combustor. The effects of bulk velocity Ub, thermal power P and equivalence ratio Φ are also explored. Due to the gyratory flow motion induced by oblique injection, the flame fronts only propagate along the direction of circumferential flow. Both of the circumferential flame propagation speed increase with increasing bulk velocity in two injection types. It seems mainly to depend on bulk velocity, regardless of Φ, in oblique-injecting combustor when compared with the straight one. It indicates that the circumferential velocity component would play a dominant role in light-round sequence when it is sufficient higher than the displacement flame speed.

Optical and Numerical Investigations of Flame Propagation in a Heavy Duty Spark Ignited Natural Gas Engine

2021 ◽  
Author(s):  
Jinlong Liu ◽  
Christopher Ulishney ◽  
Cosmin E. Dumitrescu
Keyword(s):  
Natural Gas ◽  
Flame Propagation ◽  
Turbulence Intensity ◽  
Laminar Flame ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Flame Speed ◽  
Laminar Flame Speed ◽  
Heavy Duty ◽  
Piston Chamber

Abstract Increasing the natural gas (NG) use in heavy-duty engines is beneficial for reducing greenhouse-gas emissions from power generation and transportation. However, converting compression ignition (CI) engines to NG spark ignition operation can increase methane emissions without expensive aftertreatment, thereby defeating the purpose of utilizing a low carbon fuel. The widely accepted explanation for the low combustion efficiency in such retrofitted engines is the lower laminar flame speed of natural gas. In addition, diesel engine’s larger bowl size compared to the traditional gasoline engines increases the flame travel length inside the chamber and extends the combustion duration. However, optical measurements performed in this study suggested that a fast-propagating flame was developed inside the cylinder even at extremely lean operation. This was supported by a three-dimensional numerical simulation, which indicated that the squish region of the bowl-in-piston chamber generated a high turbulence intensity inside the bowl. However, the flame propagation experienced a sudden 2.25x reduction in speed when transiting from the bowl to the squish region. Such a phenomenon was caused by the large decrease in the turbulence intensity inside the squish region during the combustion process. Moreover, the squish volume trapped an important fuel fraction, and it is this fraction that experienced a slow and inefficient burning process during the expansion stroke. This resulted in increased methane emissions and reduced combustion efficiency. Overall, it was the specifics of the combustion process inside a bowl-in-piston chamber not the methane’s slow laminar flame speed that contributed to the low methane combustion efficiency for the retrofitted engine. The results suggest that optimizing the chamber shape is paramount to boost engine efficiency and decrease its emissions.

scholarly journals Investigation of Pressure Rise and Flame Acceleration Characteristics in a Single Channel of Wave Rotor Combustor with Spoilers

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jianzhong Li ◽  
Kaichen Zhang ◽  
Wei Li ◽  
Li Yuan
Keyword(s):  
Flame Propagation ◽  
Single Channel ◽  
Pressure Rise ◽  
Propagation Speed ◽  
Blockage Ratio ◽  
Wave Rotor ◽  
Flame Acceleration ◽  
Channel Wave ◽  
Experimental Rig ◽  
Flame Propagation Speed

A simplified single channel wave rotor combustor (WRC) experimental rig was established, in which the spoilers with different blockage ratios (BR) could be conveniently installed and disassembled. The spoilers were firstly used for WRC to improve the pressure rise. The effects of different blockage ratios on the pressure rise and flame acceleration characteristics in a single channel of the WRC were investigated. The addition of spoilers could remarkably improve the pressure rise and flame propagation speed in a single channel of the WRC. While the blockage ratio of the spoiler increases, both pressure rise and mean flame propagation speed are improved. When the spoilers with a blockage ratio of 38.91% are used, the peak pressure increases by 200% compared to that of WRC without the spoilers. When the spoilers of different blockage ratios (23.35%, 31.13%, and 38.91%) are used, it is found that the flame propagation speed is significantly improved with the increasing of the blockage ratio. Specifically, the maximum flame propagation speed reaches 55 m/s, and the maximum mean flame propagation speed is 36.95 m/s. Furthermore, combustion becomes more intense, and the flame is brighter around the spoiler.

Effect of additional diluents on flame propagation speed and markstein length in outwardly propagating premixed methane/ethylene–air flames

2018 ◽  
Vol 32 (11) ◽  
pp. 5501-5509 ◽  
Author(s):  
Hee June Kim ◽  
Kyuho Van ◽  
Kee Man Lee ◽  
Dae Keun Lee ◽  
Young Tae Guahk ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Propagation Speed ◽  
Markstein Length ◽  
Flame Propagation Speed
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