Effects of compression ratio and hydrogen addition on lean combustion characteristics and emission formation in a Compressed Natural Gas fuelled spark ignition engine

Bhasker, J.; Porpatham, E.

doi:10.1016/j.fuel.2017.07.024

Cited by 108 publications

(36 citation statements)

References 34 publications

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“…Reyes et al 14 noticed the low slope of the heat release rate toward the end of combustion (EOC) when investigating cycle-to-cycle variations in such an engine setup. Bhasker and Porpatham 15 showed a heat release rate with a long tail, which was not representative of conventional SI engines. Recent three-dimensional (3D) computational fluid dynamics (CFD) simulations suggested that this different heat release rate was caused by the two-stage combustion mentioned before.…”

Section: Introductionmentioning

confidence: 89%

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

Liu

Dumitrescu

2019

International Journal of Engine Research

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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.

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Section: Introductionmentioning

confidence: 89%

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

Liu

Dumitrescu

2019

International Journal of Engine Research

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“…A study on the use of CNG in SI engines is found in [15]. This single-cylinder engine was modified to operate with poor air/fuel mixtures and tested at constant speed of 1500 rpm, in the condition of fully open throttle and with different compression ratios, whose optimized value was 12.5: 1.…”

Section: Introductionmentioning

confidence: 99%

Predictive thermodynamic model of the performance of a stationary spark-ignition engine running on natural gas

Gutiérrez

Monteiro

Vaz

2020

J Braz. Soc. Mech. Sci. Eng.

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In order to reduce the emissions of polluting gases and contribute to the efficient use of energy, natural gas has gained relevance due to its cleaner burning when compared to gasoline and diesel oil. In this work, a zero-dimensional thermodynamic model was developed to predict the performance, for the entire operating conditions, of a 11.7-L, six-cylinder, turbocharged spark-ignition engine used as genset and running on natural gas. This zero-dimensional model covers the closed period of the engine operating cycle. Firstly, this engine was tested in seven (7) different operating conditions to obtain the mass fraction burned and the pressure curves inside the cylinder. The combustion process was modeled using the simple Wiebe function, whose parameters were obtained from the seven (7) curves of the mass fraction burned through the Levenberg-Marquardt optimization method. Correlations were developed to estimate the Wiebe function parameters, as a function of pressure and temperature in the intake manifold, cylinder wall temperature, power and fuel consumption, for the entire operating range. The combustion efficiencies were estimated from the seven (7) experimental pressure curves with the aforementioned optimization technique. Results showed that the differences between the Wiebe function parameters obtained with the developed correlation, for the whole engine operating range, were less than 3% when compared with the Wiebe function parameters estimated for each of the seven (7) operating conditions tested. Results also showed that the thermodynamic model can be used to simulate the engine's performance, leading to errors less than 5% when compared with the measured maximum pressure and indicated mean pressure. In addition, it was found that the delay and duration of the combustion are smaller than those usually found in spark-ignition engines and that the energy release is deficient, resulting in high specific fuel consumption. This issue can be addressed by installing an equivalence ratio control system, especially in loads above 50%, thus ensuring greater control of emissions and increasing energy efficiency.

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“…4,5 As a consequence of all kinds of advantages of CNG, increasing number of works about natural gas conversions on gasoline and diesel engines have been performed during last decades. 6 When CNG as an alternative fuel will be used in an engine, which is originally designed for gasoline or diesel, it becomes a need to know and determine engine performance and emissions for CNG usage and CNG addition. Engine characteristics for CNG differ depending on engine’s specific design.…”

Section: Introductionmentioning

confidence: 99%

“…17 High ignition energy, low quenching distance, and relatively lower flame speed properties are disadvantages of CNG for lean combustion. 6 At lean burn condition, the emission formations reduce and the flame propagation speed increases in the overall combustion duration. 18,19…”

Section: Introductionmentioning

confidence: 99%

Effects of equivalence ratio and CNG addition on engine performance and emissions in a dual sequential ignition engine

Yontar

Doğu

2019

International Journal of Engine Research

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Compared to widening usage of CNG in commercial gasoline engines, insufficient but increasing number of studies have appeared in the open literature during last decades, while engine characteristics need to be quantified in exact numbers for each specific fuel and engine. CNG usage in spark-ignition engine offers many advantages such as high specific power outputs, knock resistance, and low CO2 emission. Engine performance and emissions are strong functions of equivalence ratio. This study focuses on determination of the effects of equivalence ratio on engine performance and emissions for a unique commercial engine for three fuels of gasoline, CNG, and gasoline–CNG mixture (90%–10%: G9C1). For this aim, the tests and the three-dimensional in-cylinder combustion computational fluid dynamics analyses were employed in quantification of engine characteristics at wide open throttle position. Equivalence ratios were defined between 0.7 and 1.4. The engine’s maximum torque speed of 2800 r/min was examined. The tested commercial engine is an intelligent dual sequential ignition engine which has unique features such as diagonally positioned two spark-plugs, dual sequential ignition with variable timing and asymmetrical combustion chamber. This gasoline engine was equipped with an independent CNG port-injection system and a specific engine control unit for CNG. In addition, the engine test system has a concomitant dual fuel delivery system that supplies gas fuel into intake airline while liquid gasoline is injected behind the intake valve. Other than testing the engine, the three-dimensional in-cylinder combustion computational fluid dynamics analyses were performed in Star-CD/es-ice software for the three fuels. The CFD model was built by using renormalization group equations, k–ε turbulence model, and G-equation combustion model. Computational fluid dynamics analyses were run for the compression ratio of 10.8:1, equivalence ratio of 1.1, and engine’s maximum torque speed of 2800 r/min. Test results show that brake torque for all fuels increases rapidly from the lean blend to the rich blend. The brake-specific fuel consumption for all fuels decreases from Φ = 0.7 through the stoichiometric region and then slightly increases up to Φ = 1.4. The volumetric efficiencies for three fuels have similar decreasing trend with respect to equivalence ratio. Overall, CNG addition decreases the performance values of torque, brake-specific fuel consumption, volumetric efficiency, brake thermal efficiency, while it decreases emissions of CO2, CO, HC, except NOx. Engine model results show that the maximum in-cylinder pressure is 72 bar at 722 crank angle degree (CAD), 68 bar at 730 CAD, and 60 bar at 735 CAD for gasoline, CNG, and G9C1, respectively. The cumulative heat release for gasoline is 9.09% higher than G9C1, while G9C1 is 15.71% higher than CNG. The CO2 mass fraction for gasoline is about 22.58% lower than G9C1, while it is 40.32% higher than CNG. The maximum mass fraction value of CO is 0.21, 0.17, and 0.08 for gasoline, CNG, and G9C1, respectively. The CO for G9C1 is overall 60.04% lower than CNG and 67.45% lower than gasoline. At maximum point, HC for G9C1 is 31.43% and 71.43% higher than gasoline and CNG, respectively. CNG has the highest level of NOx formation. Maximum NOx mass fractions are 0.0098, 0.0070, and 0.0043 for CNG, G9C1, and gasoline, respectively. After the ignition, the flame development is completed at 1.07, 1.18, and 1.28 ms for gasoline, G9C1, and CNG, respectively. Flame velocities are 28.52, 30.93, and 34.11 m/s for CNG, G9C1, and gasoline, respectively, at 2800 r/min and Φ = 1.1. When the time between ignition moment and top dead center moment is considered, the increment rate of flame center temperature is 904.19, 884.10, and 861.77 K/s for CNG, gasoline, and G9C1, respectively. The highest temperature increment rate occurs for CNG.

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Effects of compression ratio and hydrogen addition on lean combustion characteristics and emission formation in a Compressed Natural Gas fuelled spark ignition engine

Cited by 108 publications

References 34 publications

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

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

Predictive thermodynamic model of the performance of a stationary spark-ignition engine running on natural gas

Effects of equivalence ratio and CNG addition on engine performance and emissions in a dual sequential ignition engine

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