Knock Characteristics and Their Control with Hydrogen Injection Using a Rapid Compression/Expansion Machine

Kee, Sung-Sub; Shioji, Masahiro; Mohammadi, Ali; Nishi, Muneyuki; Inoue, Yohei

doi:10.4271/2007-01-1829

Cited by 4 publications

(7 citation statements)

References 13 publications

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“…Because end-gas auto-ignition is the first stage of knocking, whose subsequent development determines the knocking occurrence and intensity, in general, it can be concluded that knocking in SI engines is induced by auto-ignition occurring in the end gas [3,4], which has been extensively and comprehensively investigated. Many excellent studies have contributed to exploring the method of inhibiting such knocking, and several potential means have been discovered, including changing the flame propagation speed [5], increasing the in-cylinder turbulence [6,7], split injection strategies [8], octane number [9,10], and EGR (Exhaust Gas Recirculation) strategies [11]. For instance, Yang et al [12] found a higher tumble rate can lead to the increase of flame speed through by facilitating the interaction between the fuel spray and air flow and the heat-mass transfer between the unburnt and burnt zone.…”

Section: Of 23mentioning

confidence: 99%

“…In fact, there are disagreeing opinions among researchers regarding whether an increase in the flame speed is capable of inhibiting knocking. Kee et al [5] developed a rapid compression/expansion device to explore the essential phenomenon of knocking. Their results indicate that increasing the laminar flame speed inhibits the knocking because a fast propagation decreases the time required for low-temperature reactions in the end gas.…”

Section: Of 23mentioning

confidence: 99%

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Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

et al. 2020

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Knocking is a destructive and abnormal combustion phenomenon that hinders modern spark ignition (SI) engine technologies. However, the in-depth mechanism of a single-factor influence on knocking has not been well studied. Thus, the major aim of the present study is to study the effects of flame propagation velocity and turbulence intensity on end-gas auto-ignition through a large eddy simulation (LES) and a decoupling methodology in a downsized gasoline engine. The mechanisms of end-gas auto-ignition as well as strong pressure oscillation are qualitatively analyzed. It is observed that both flame propagation velocity and turbulence have a non-monotonic effect on knocking intensity. The competitive relationship between flame propagation velocity and ignition delay of the end gas is the primary reason responding to this phenomenon. A higher flame speed leads to an increase in the heat release rate in the cylinder, and consequently, quicker increases in the temperature and pressure of the unburned end-gas mixture are obtained, leading to end-gas auto-ignition. Further, the coupling of a pressure wave and an auto-ignition flame front results in super-knocking with a maximum peak of pressure of 31 MPa. Although the turbulence indirectly influences the end-gas auto-ignition by affecting the flame propagation velocity, it can accelerate the dissipation of radicals and heat in the end gas, which significantly influences knocking intensity. Moreover, it is found that the effect of turbulence is more pronounced than that of flame propagation velocity in inhibiting knocking. It can be concluded that the intensity of the pressure oscillation depends on the unburned mixture mass as well as the local thermodynamic state induced by flame propagation and turbulence, with mutual interactions. The present work is expected to provide valuable perspective for inhibiting super-knocking of an SI gasoline engine.

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Section: Of 23mentioning

confidence: 99%

Section: Of 23mentioning

confidence: 99%

Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

et al. 2020

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“…RCMs [2][3][4][5][6][7][8][9][10][11][12][13][14] and rapid compression and expansion machines (RCEMs) [15][16][17][18][19] can be classified on the basis of whether they can perform an expansion stroke. The distinguishing characteristic of RCM from RCEM is that when the piston of the RCM moves to the top dead center (TDC), the piston gets locked (including driving gas pressure locking or mechanical locking) without an expansion process, such that a constant volume combustion chamber is formed.…”

Section: Introductionmentioning

confidence: 99%

“…As regards to the different driving methods, RCM uses potential energy drive, motor drive [8,15], and pneumatic drive types [6,7]. For enhanced effect and convenience, an increasing number of RCMs use the pneumatic drive type.…”

Section: Introductionmentioning

confidence: 99%

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Performance Characterization and Auto-Ignition Performance of a Rapid Compression Machine

et al. 2014

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Abstract:A rapid compression machine (RCM) test bench is developed in this study. The performance characterization and auto-ignition performance tests are conducted at an initial temperature of 293 K, a compression ratio of 9.5 to 16.5, a compressed temperature of 650 K to 850 K, a driving gas pressure range of 0.25 MPa to 0.7 MPa, an initial pressure of 0.04 MPa to 0.09 MPa, and a nitrogen dilution ratio of 35% to 65%. A new type of hydraulic piston is used to address the problem in which the hydraulic buffer adversely affects the rapid compression process. Auto-ignition performance tests of the RCM are then performed using a DME-O2-N2 mixture. The two-stage ignition delay and negative temperature coefficient (NTC) behavior of the mixture are observed. The effects of driving gas pressure, compression ratio, initial pressure, and nitrogen dilution ratio on the two-stage ignition delay are investigated. Results show that both the first-stage and overall ignition delays tend to increase with increasing driving gas pressure. The driving gas pressure within a certain range does not significantly influence the compressed pressure. With increasing compression ratio, the first-stage ignition delay is shortened, whereas the second-stage ignition delay is extended. With increasing initial pressure, both the first-stage and second-stage ignition delays are shortened. The second-stage ignition delay is shortened to a greater extent than that of the first-stage. With increasing nitrogen dilution ratio, the first-stage ignition delay is shortened, whereas the second-stage is extended. Thus, overall ignition delay presents different trends under various compression ratios and compressed pressure conditions. OPEN ACCESSEnergies 2014, 7 6084

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Influence of injection strategies on knock resistance and combustion characteristics in a DISI engine

Wei

Shao

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part D:

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The combustion of a direct injection spark ignition engine is significantly affected by the fuel injection strategy due to the impact this strategy has on the gas-mixture formation and the turbulence flow. However, comprehensive assessments on both knock and engine performances for different injection strategies are generally lacking. Therefore, the main objective of the present study is to provide an experimental evidence of how a single injection strategy and a split injection strategy compare in terms of both knock tendency and engine performances like thermal efficiency, torque and combustion stability. Starting from the optimization of a single injection strategy, a split injection strategy is then evaluated. Under the present operating conditions, an optimum secondary injection timing of 100 CAD BTDC is found to have significant improvements on both the knock resistance and the overall engine performances. It should be noted that the present results indicate that the relationship between double injection and anti-knock performance is not monotonous. In addition, the double injection shows superior potential in improving fuel economy and power performance in contrast with the single injection thanks to a more stable combustion when a late injection timing is applied.

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Knock Characteristics and Their Control with Hydrogen Injection Using a Rapid Compression/Expansion Machine

Cited by 4 publications

References 13 publications

Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

Effects of Flame Propagation Velocity and Turbulence Intensity on End-Gas Auto-Ignition in a Spark Ignition Gasoline Engine

Performance Characterization and Auto-Ignition Performance of a Rapid Compression Machine

Influence of injection strategies on knock resistance and combustion characteristics in a DISI engine

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