Spark-Ignition Engine Knock Control and Threshold Value Determination

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.

Download Full-text

Analysis of Spark Ignition Engine Knock Signals using Fourier and Discrete Wavelet Transform

10.4271/2009-36-0312 ◽

2009 ◽

Cited By ~ 5

Author(s):

Rodrigo Ceccatto Gerardin ◽

Belisá rio Nina Huallpa ◽

Marco Aurélio Faleiros Alves ◽

José Roberto de França Arruda

Keyword(s):

Wavelet Transform ◽

Discrete Wavelet Transform ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Discrete Wavelet ◽

Engine Knock

Download Full-text

Lubricant Reactivity Effects on Gasoline Spark Ignition Engine Knock

SAE International Journal of Fuels and Lubricants ◽

10.4271/2012-01-1140 ◽

2012 ◽

Vol 5 (2) ◽

pp. 760-771 ◽

Cited By ~ 30

Author(s):

Manfred Amann ◽

Terrence Alger

Keyword(s):

Spark Ignition ◽

Spark Ignition Engine ◽

Engine Knock

Download Full-text

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

Journal of Energy Resources Technology ◽

10.1115/1.4043393 ◽

2019 ◽

Vol 141 (10) ◽

Cited By ~ 4

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.

Download Full-text