scholarly journals Prediction of Cyclic Variability and Knock-Limited Spark Advance (KLSA) in Spark-Ignition (SI) Engine

2018 ◽  
Author(s):  
Zongyu Yue ◽  
K. Dean Edwards ◽  
C. Scott Sluder ◽  
Sibendu Som
Keyword(s):  
Octane Number ◽  
Spark Ignition ◽  
Fuel Properties ◽  
Maximum Efficiency ◽  
Ignition Timing ◽  
Si Engine ◽  
Cfd Simulations ◽  
Chemical Kinetic Model ◽  
Cyclic Variability ◽  
Engine Knock

Engine knock remains one of the major barriers to further improve thermal efficiency of Spark Ignition (SI) engines. Knock can be suppressed by lowering the compression ratio, or retarding the spark ignition timing, however, at an expense of efficiency penalty. SI engine is usually operated at knock-limited spark advance (KLSA) to achieve possibly maximum efficiency with given engine hardware and fuel properties, such as Research Octane Number (RON), Motor Octane Number (MON), and heat of vaporization, etc. Co-optimization of engine design and fuel properties is promising to improve the engine efficiency and predictive CFD models can be used to facilitate this optimization process. However, difficulties exist in predicting KLSA in CFD simulations. First, cyclic variability of SI engine demands that multi-cycle results are required to capture the extreme conditions. Secondly, Mach Courant-Friedrichs-Lewy (CFL) number of 1 is desired to accurately predict the knock intensity (KI), resulting in unaffordable computational cost, especially for multi-cycle simulations. In this study, a new approach to numerically predict KLSA using large Mach CFL number of 50 is proposed. This approach is validated against experimental data for a boosted Direct Injection Spark Ignition (DISI) engine at multiple loads and spark timings. G-equation combustion model coupled with well-mixed chemical kinetic model are used to predict the turbulent flame propagation and end-gas auto-ignition, respectively. Simulations run for 10 consecutive engine cycles at each condition. The results show good agreement between model predictions and experiments in terms of cylinder pressure, combustion phasing and cyclic variation. Engine knock is predicted with early spark ignition timing, indicated by significant pressure wave oscillation and end-gas heat release. Maximum Amplitude of Pressure Oscillation (MAPO) analysis is performed to quantify the KI, and the slope change point in KI extrema is used to indicate the KLSA accurately. Using a smaller Mach CFL number of 5 also results in the same conclusions thus demonstrating that this approach is insensitive to the Mach CFL number. The use of large Mach CFL number allows us to achieve fast turn-around time for multi-cycle engine CFD simulations.

scholarly journals Prediction of Cyclic Variability and Knock-Limited Spark Advance in a Spark-Ignition Engine

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Zongyu Yue ◽  
K. Dean Edwards ◽  
C. Scott Sluders ◽  
Sibendu Som
Keyword(s):  
Computational Cost ◽  
Pressure Oscillation ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Maximum Efficiency ◽  
Si Engine ◽  
Cyclic Variability ◽  
Cycle Simulation ◽  
Oscillation Analysis ◽  
Engine Knock

Engine knock remains one of the major barriers to further improve the thermal efficiency of spark-ignition (SI) engines. SI engine is usually operated at knock-limited spark advance (KLSA) to achieve possibly maximum efficiency with given engine hardware and fuel properties. Co-optimization of fuels and engines is promising to improve engine efficiency, and predictive computational fluid dynamics (CFD) models can be used to facilitate this process. However, cyclic variability of SI engine demands that multicycle results are required to capture the extreme conditions. In addition, Mach Courant–Friedrichs–Lewy (CFL) number of 1 is desired to accurately predict the knock intensity (KI), resulting in unaffordable computational cost. In this study, a new approach to numerically predict KLSA using large Mach CFL of 50 with ten consecutive cycle simulation is proposed. This approach is validated against the experimental data for a boosted SI engine at multiple loads and spark timings with good agreements in terms of cylinder pressure, combustion phasing, and cyclic variation. Engine knock is predicted with early spark timing, indicated by significant pressure oscillation and end-gas heat release. Maximum amplitude of pressure oscillation analysis is performed to quantify the KI, and the slope change point in KI extrema is used to indicate the KLSA accurately. Using a smaller Mach CFL number of 5 also results in the same conclusions, thus demonstrating that this approach is insensitive to the Mach CFL number. The use of large Mach CFL number allows us to achieve fast turn-around time for multicycle engine CFD simulations.

scholarly journals Torque and Power Characteristics of Single Piston LPG-Fueled Engines on Variations of Ignition Timing

2019 ◽  
Vol 2 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Bagiyo Condro Purnomo ◽  
Noto Widodo
Keyword(s):  
Engine Performance ◽  
Alternative Fuel ◽  
Spark Ignition ◽  
Liquefied Petroleum Gas ◽  
Ignition Timing ◽  
Si Engine ◽  
Optimum Performance ◽  
Power Characteristics

Liquefied Petroleum Gas (LPG) is an alternative fuel that has all key properties for the Spark Ignition (SI) engine. However, because of its properties, ignition timing on an LPG SI engine needs to be advanced from the reference angle to get the optimum performance. Therefore, this article presents the torque and power characteristics of a single piston LPG engine on variations of ignition timing. Evaluation of engine performance is carried out at the ignition timing of 15O, 17O, and 19O BTDC. The results showed the highest torque for LPG fuel was 10.64 Nm which was achieved at 3500 rpm with ignition timing of 19O BTDC, while the highest power for LPG fuel was 6.9 hp which was achieved at 5936 rpm with ignition timing of 19O BTDC.

Effects of multiple spark ignition on engine knock under different compression ratio and fuel octane number conditions

Fuel ◽  
2021 ◽  
pp. 122471
Author(s):  
Hao Shi ◽  
Qinglong Tang ◽  
Kalim Uddeen ◽  
Bengt Johansson ◽  
James Turner ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Octane Number ◽  
Spark Ignition ◽  
Engine Knock

Modeling Investigation of Different Methods to Suppress Engine Knock on a Small Spark Ignition Engine

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Jiankun Shao ◽  
Christopher J. Rutland
Keyword(s):  
Octane Number ◽  
Direct Injection ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Simulation Code ◽  
Engine Knock ◽  
Combustion Simulation ◽  
3D Engine ◽  
Gas Recirculation

Knock is the main obstacle toward increasing the compression ratio and using lower octane number fuels. In this paper, a small two-valve aircraft spark ignition engine, Rotax-914, was used as an example to investigate different methods to suppress engine knock. It is generally known that if the octane number is increased and the combustion period is shortened, the occurrence of knock will be suppressed. Thus, in this paper, different methods were introduced for two effects, increasing ignition delay time in end-gas and increasing flame speed. In the context, KIVA-3V code, as an advanced 3D engine combustion simulation code, was used for engine simulations and chemical kinetics investigations were also conducted using chemkin. The results illustrated gas addition, such as hydrogen and natural gas addition, can be used to increase knock resistance of the Rotax-914 engine in some operating conditions. Replacing the traditional port injection method by direct injection strategy was another way investigated in this paper to suppress engine knock. Some traditional methods, such as adding exhaust gas recirculation (EGR) and increasing swirl ratio, also worked for this small spark ignition engine.

Combustion Characteristics of Spark Ignition Engine Fuelled by LPG

2001 ◽  
Author(s):  
M. S. Shehata
Keyword(s):  
Engine Speed ◽  
Cooling Water ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Maximum Efficiency ◽  
Cylinder Pressure ◽  
Gas Temperature ◽  
Ignition Timing ◽  
Increase With Increase ◽  
Crank Angle

Abstract Experimental studies have been carried out for investigating engine performance parameters, cylinder pressure, emissions and engine thermal balance of spark ignition engine (S.I.E.) using either gasoline or Liquefied Petroleum Gases (LPG) as a fuel at maximum brake torque (MBT) ignition timing. MBT ignition timing for LPG is found to be 2 to 10 degrees crank angle more advance than for gasoline. Maximum cylinder pressure locations for gasoline and LPG are shifted towards top dead center (TDC) with increase engine speed. At low engine speed, maximum cylinder pressure for gasoline fuel is higher than for LPG fuel. At high engine speeds maximum cylinder pressure for LPG is nearly the same as for gasoline. Maximum pressure for ignition timing 35 crank angle (CA) before top dead center (BTDC) is greater than for 45 and 25 CA respectively. Engine produces more brake power with gasoline than with LPG. Engine brake thermal efficiency (ηbth) and volumetric efficiency (ηv) with LPG is less than for gasoline. When S.I.E converted from gasoline to LPG the loss in maximum power is nearly 14% and the loss in maximum efficiency is nearly 8%. UHC and CO concentrations for LPG are nearly one-tenth of that produced by gasoline at the same ignition timing and the same engine speed. For low engine speed exhaust and oil temperatures for gasoline and LPG increase with increase engine speed but for high engine speed exhaust and oil temperature decreases with increase engine speed. For gasoline and LPG cooling water temperature decreases with increase engine speed. Lubricating oil and cooling water temperatures for gasoline and LPG increase with increase ignition timing BTDC but exhaust gas temperature decreases with increase ignition timing. LPG has higher exhausted gas temperature than gasoline but gasoline has higher oil temperature than LPG. At different ignition timing exhaust loss for LPG is greater than for gasoline but cooling water loss for gasoline is greater than for LPG.

Numerical Simulations of a Hydrogen-Enriched Methane Fueled Spark Ignition Engine

2004 ◽  
Author(s):  
V. Matham ◽  
K. Majmudar ◽  
K. Aung
Keyword(s):  
Numerical Simulations ◽  
Alternative Fuels ◽  
Engine Speed ◽  
Current Model ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Ignition Timing ◽  
Si Engine ◽  
Gaseous Fuels ◽  
Si Engines

The use of alternative fuels such as natural gas (methane) in spark-ignition (SI) engines is beneficial to the environment as it reduces emissions of pollutants such as NOx from these engines with slight penalty on the performance. This paper investigated the use of methane and hydrogen/methane mixtures in an SI engine by numerical simulations. The numerical simulations were based on the models of finite heat release, cylinder heat transfer, pumping losses, and friction losses. Simulations were carried out to evaluate the effects of compression ratio, equivalence ratio, ignition timing, and engine speed on the performance of the SI engine. The results showed that the current model could satisfactorily predict the performance of an SI engine fueled by gaseous fuels.

scholarly journals Numerical Investigation of a Central Fuel Property Hypothesis Under Boosted Spark-Ignition Conditions

2019 ◽  
Author(s):  
Pinaki Pal ◽  
Krishna Kalvakala ◽  
Yunchao Wu ◽  
Matthew McNenly ◽  
Simon Lapointe ◽  
...  
Keyword(s):  
Octane Number ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Operating Conditions ◽  
Fuel Properties ◽  
Laminar Flame Speed ◽  
Fuel Blend ◽  
Fuel Property

Abstract In the present work, a central fuel property hypothesis (CFPH), which states that fuel properties are sufficient to provide an indication of a fuel’s performance irrespective of its chemical composition, was numerically investigated. In particular, the objective of the study was to determine whether Research Octane Number (RON) and Motor Octane Number (MON), as fuel properties, are sufficient to describe a fuel’s knock-limited performance under boosted spark-ignition (SI) conditions within the framework of CFPH. To this end, four TPRF-bioblendstock surrogates having different compositions but matched RON (= 98) and MON (= 90), were first generated using a non-linear regression model based on artificial neural network (ANN). Three unconventional bioblendstocks were included in the analysis: Di-isobutylene (DIB), Isobutanol and Anisole. Skeletal reaction mechanisms were generated for the TPRF-DIB, TPRF-isobutanol and TPRF-anisole blends from a detailed kinetic mechanism. Thereafter, numerical simulations were performed for the fuel surrogates using the skeletal mechanisms and a virtual cooperative fuel research (CFR) engine model, under a representative boosted operating condition. In the computational fluid dynamics (CFD) model, the G-equation approach was employed to track the turbulent flame front and the well-stirred reactor model combined with multi-zone binning strategy was used to capture auto-ignition in the end-gas. In addition, laminar flame speed was tabulated for each blend as a function of pressure, temperature and equivalence ratio a priori, and the lookup tables were used to prescribe laminar flame speed as an input to the G-equation model. Parametric spark timing sweeps were performed for each fuel blend to determine the corresponding knock-limited spark advance (KLSA) and 50% burn point (CA50) at the respective KLSA timing. It was observed that despite same RON, MON and engine operating conditions, the TPRF-Anisole blend exhibited markedly different knock-limited performance from the other three blends. This deviation from the octane index (OI) expectation was shown to be caused by differences in laminar flame speed (LFS). However, it was found that relatively large fuel-specific differences in LFS (> 20%) would have to be present to cause any appreciable deviation from the OI framework. Otherwise, RON and MON would still be robust enough to predict a fuel’s knock-limited performance.

scholarly journals Numerical Investigation of a Central Fuel Property Hypothesis Under Boosted Spark-Ignition Conditions

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Pinaki Pal ◽  
Krishna Kalvakala ◽  
Yunchao Wu ◽  
Matthew McNenly ◽  
Simon Lapointe ◽  
...  
Keyword(s):  
Octane Number ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Spark Ignition ◽  
Flame Speed ◽  
Operating Conditions ◽  
Fuel Properties ◽  
Laminar Flame Speed ◽  
Fuel Blend ◽  
Fuel Property

Abstract In the present work, a central fuel property hypothesis (CFPH), which states that fuel properties are sufficient to provide an indication of a fuel’s performance irrespective of its chemical composition, was numerically investigated. In particular, the objective of the study was to determine whether Research Octane Number (RON) and Motor Octane Number (MON), as fuel properties, are sufficient to describe a fuel’s knock-limited performance under boosted spark-ignition (SI) conditions within the framework of CFPH. To this end, four TPRF-bioblendstock surrogates having different compositions but matched RON (=98) and MON (=90), were first generated using a non-linear regression model based on artificial neural network (ANN). Three unconventional bioblendstocks were included in the analysis: di-isobutylene (DIB), isobutanol, and Anisole. Skeletal reaction mechanisms were generated for the TPRF-DIB, TPRF-isobutanol, and TPRF-anisole blends from a detailed kinetic mechanism. Thereafter, numerical simulations were performed for the fuel surrogates using the skeletal mechanisms and a virtual cooperative fuel research (CFR) engine model, under a representative boosted operating condition. In the computational fluid dynamics (CFD) model, the G-equation approach was employed to track the turbulent flame front and the well-stirred reactor model combined with the multi-zone binning strategy was used to capture auto-ignition in the end-gas. In addition, laminar flame speed (LFS) was tabulated for each blend as a function of pressure, temperature, and equivalence ratio a priori, and the lookup tables were used to prescribe laminar flame speed as an input to the G-equation model. Parametric spark timing sweeps were performed for each fuel blend to determine the corresponding knock-limited spark advance (KLSA) and 50% burn point (CA50) at the respective KLSA timing. It was observed that despite same RON, MON, and engine operating conditions, the TPRF-anisole blend exhibited markedly different knock-limited performance from the other three blends. This deviation from the octane index (OI) expectation was shown to be caused by differences in laminar flame speed. However, it was found that relatively large fuel-specific differences in LFS (>20%) would have to be present to cause any appreciable deviation from the OI framework. Otherwise, RON and MON would still be robust enough to predict a fuel’s knock-limited performance.

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