Antiknock Performance Research Articles

Effects of applying a Miller cycle with split injection on engine performance and knock resistance in a downsized gasoline engine

Downsizing a spark ignition (SI) engine with boost pressure is a proven way of increasing the thermal efficiency and reducing CO2 emissions. However, the occurrence of abnormal combustion problems such as knock and super knock could seriously damage the downsized SI engine and limit its efficiency improvement. In this study, the effects of the Miller cycle on anti-knock and engine power are experimentally investigated using a single-cylinder gasoline engine, the speed corresponded to 1600 rpm and air–fuel ratio corresponded to 1. The Miller cycle provides a good anti-knock performance because of its low in-cylinder temperature induced by the lower effective compression ratio, however, it has a poor dynamic output. To increase the intake charge of the Miller cycle, boost pressure was applied. The results showed a clear improvement in both the thermal efficiency and torque of the engine. Furthermore, the knock tendency of the engine was reduced. However, compared with the Miller cycle without boost pressure, the knock tendency with boost pressure was significantlyhigher. Therefore, to improve both engine power and knock resistance, this study combined split injection to the Miller cycle with boost pressure. The result indicates that the combined method can effectively decrease the knock tendency and increase the engine torque. The best secondary start of injection timing for the Miller cycle with boost pressure and split injection is 100 CAD BTDC. In conclusion, the Miller cycle with intake boost pressure and split injection has a considerable potential for achieving both a better knock resistance and higher engine power.

Influence of methane content on a LNG heavy-duty engine with high compression ratio

An experiment was conducted to investigate the effects of methane content in natural gas on combustion and performance of a liquefied natural gas (LNG) heavy-duty engine. Two kinds of LNG with different methane contents (i.e. 93% and 99%), in combination with three compression ratios (i.e. CR11.6, CR14 and CR16) and varied spark timings were tested and compared at various engine speeds. The results show that natural gas with 99% methane content has better actual antiknock performance than the one with 93% methane content, and subsequent better power performance and fuel economy. When compression ratio is increased from 11.6 to 14, natural gas with 99% methane content can maintain the maximum loads at all tested speeds, and achieve a maximum decrease of 6.4% in BSFC. On the contrary, the maximum load at high-speed is limited for natural gas with 93% methane content due to knocking combustion. Moreover, natural gas with 99% methane content has larger knock-limited spark advanced angle compared to the one with 93% methane content, so it achieves earlier ignition and then lower BSFC. In conclusion, higher methane content has better comprehensive performance than the lower one in natural gas engines with high compression ratio.

The Development of the Octane Number Tests and their Impact on Automotive Fuels and American Society

Modern automobiles and fuels were shaped heavily by the development of the octane number tests. These tests were developed between 1929 and 1932 to quantify a fuel’s anti-knock performance in spark-ignition engines. Since knock imposes limits on the maximum engine compression ratio, which correlates to engine performance, the anti-knock property of a fuel is a crucial design constraint. Prior to the development of the octane number tests, engines were designed to run at very low compression ratios to avoid knock, significantly limiting their performance. The octane number tests created standards that allowed for better engine development and advancements in fuel technology. Engines could now be designed to handle a specific octane number of fuel allowing for increased performance. The demand for better performing engines resulted in an increase in the average fuel octane number from 50 to 75 during this period, with the Great Depression and World War II setting the stage for this advancement. These advancements in fuel technology played a crucial role in the survival of the American automobile industry during the Great Depression, the Allied success in World War II, in addition to creating the ‘American obsession’ with powerful automobiles. This paper provides an overview of knock, a historical summary on the development of the octane number tests, the corresponding advancements in fuel technology, and the implications of these advancements on American society.

Effect of Octane on Performance, Energy Consumption and Emissions of Two Euro 4 Passenger Cars

The combustion performance of gasoline engines has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance, while also helping refiners in the production of gasoline. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.The objective of this study was to investigate the effect of RON and MON on the power and acceleration performance of modern gasoline vehicles under full throttle acceleration conditions. Tests were carried out using two Euro 4 vehicles. Fuels covering RON levels from 95 to 103 and sensitivities (RON minus MON) of up to 15 were blended. Both pure hydrocarbon and blends containing ethanol or ETBE were included so that specific effects of oxygenates could be identified. The results confirmed the findings of other studies that MON is not a good predictor of vehicle performance and in fact high MON levels increase acceleration time under full throttle conditions. In addition to performance testing, emissions testing was also carried out. Carbon balance was used to calculate energy consumption during the acceleration tests and NEDC tests.

Antiknock Performance of Interlayered High-Damping-Rubber Blast Door under Thermobaric Shock Wave

The long duration and high impulse shock wave of thermobaric bomb threatens the security of underground structures. To obtain high resistance blast door against thermobaric shock wave, firstly, the dynamic mechanic property of high damping rubber was studied by split Hopkinson pressure bar (SHPB) equipment and the stress-strain relationship of high damping rubber under average strain rate of 5200/s was obtained. Secondly, the numerical model of interlayered high-damping-rubber blast door was established with ANSYS/LS-DYNA code based on test results, and the antiknock performance of interlayered high-damping-rubber blast door under thermobaric shock wave was analyzed by contrast with ordinary blast door. The results showed that the midspan displacement of the blast door decreased firstly and then increased with the increase of thickness of the high-damping-rubber interlayer, and the optimal thickness of the high-damping-rubber interlayer for energy consuming was 150 mm in the calculation condition of this paper. With the increase of the distance between the interlayer and the front surface of the door, the midspan displacement of the blast door decreased continually. The midspan maximum displacement of interlayered high-damping-rubber blast door decreased 74.5% in comparison to ordinary blast door. It showed that the high-damping-rubber structure can effectively improve the antiknock performance of blast door under thermobaric shock wave.

Removal of linear and monobranched alkane from aviation gasoline by 5A zeolite adsorption for octane number enhancement

AbstractDue to continued concern about effects of tetraethyl lead (TEL) emission on the environment and human health, the complete removal of TEL from aviation gasoline (avgas) is a desirable pursuit. In order to maintain high antiknock performance of avgas, an advanced adsorption method was developed using 5A zeolite to remove linear and monobranched alkane from avgas for octane number enhancement. An experimental study of single, binary, and quaternary adsorption of octane isomers on a fixed bed reactor was performed in this work. The effects of partial pressure, operating temperature, and initial mixture composition on breakthrough curves and sorption selectivity were thoroughly studied. At fixed partial pressure, normal octane was the strongest‐adsorbed component, followed by 2‐methylheptane, 2, 5‐dimethylhexane, and 2, 2, 4‐trimethylpentane. Adsorption capacity of all components increased with increased partial pressure and decreased with increased operating temperature. However, for all binary mixtures studied in this work, the sorption selectivity decreased as total pressure increased. At equimolar concentrations the normal and monobranched isomers were preferentially adsorbed, while when the volume percentages of the isomers were different, the adsorption of the isomer with the higher volume ratio was favoured. The quaternary breakthrough curves for octane isomers at 473 K with each component having partial pressure of 0.15 kPa also indicated the feasibility of simultaneous removal of normal and monobranched isomers from a multiple‐component mixture by this 5A zeolite.

Understanding fuel anti-knock performances in modern SI engines using fundamental HCCI experiments

Modern spark-ignition (SI) engine technologies have considerably changed in-cylinder conditions under which fuel autoignition and engine knock take place. In this paper, fundamental HCCI engine experiments are proposed as a means for characterizing the impact of these technologies on the knock propensity of different fuels. In particular, the impacts of turbocharging, direct injection (DI), and downspeeding on operation with ethanol and gasoline are investigated to demonstrate this approach. Results reported earlier for ethanol and gasoline on HCCI combustion are revisited with the new perspective of how their autoignition characteristics fit into the anti-knock requirement in modern SI engines. For example, the weak sensitivity to pressure boost demonstrated by ethanol in HCCI autoignition can be used to explain the strong knock resistance of ethanol fuels for turbocharged SI engines. Further, ethanol's high sensitivity to charge temperature makes charge cooling, which can be produced by fuel vaporization via direct injection or by piston expansion via spark-timing retard, very effective for inhibiting knock. On the other hand, gasoline autoignition shows a higher sensitivity to pressure, so only very low pressure boost can be applied before knock occurs. Gasoline also demonstrates low temperature sensitivity, so it is unable to make as effective use of the charge cooling produced by fuel vaporization or spark retard. These arguments comprehensively explain literature results on ethanol's substantially better anti-knock performance over gasoline in modern turbocharged DISI engines. Fundamental HCCI experiments such as these can thus be used as a diagnostic and predictive tool for knock-limited SI engine performance for various fuels. Examples are presented where HCCI experiments are used to identify biofuel compounds with good potential for modern SI-engine applications.

Size distribution, chemical composition and oxidation reactivity of particulate matter from gasoline direct injection (GDI) engine fueled with ethanol-gasoline fuel

Ethanol-gasoline blended fuels have been widely applied in markets recently, as ethanol reduces life-cycle greenhouse gas emissions and improves anti-knock performance. However, its effects on particulate matter (PM) emissions from gasoline direct injection (GDI) engine still need further investigation. In this study, the effects of ethanol-gasoline blended fuels on particle size distributions, number concentrations, chemical composition and soot oxidation activity of GDI engine were investigated. It was found that ethanol-gasoline blended fuels increased the particle number concentration in low-load operating conditions. In higher load conditions, the ethanol-gasoline was effective for reducing the particle number concentration, indicating that the chemical benefits of ethanol become dominant, which could reduce soot precursors such as large n-alkanes and aromatics in gasoline. The volatile organic mass fraction in ethanol-gasoline particulates matter was higher than that in gasoline particulate matter because ethanol reduced the amount of soot precursors during combustion and thereby reduced the elemental carbon proportions in PM. Ethanol addition also increased the proportion of small particles, which confirmed the effects of ethanol on organic composition. Ethanol-gasoline reduced the concentrations of most PAH species, except those with small aromatic rings, e.g., naphthalene. Soot from ethanol-gasoline has lower activation energy of oxidation than that from gasoline. The results in this study indicate that ethanol-gasoline has positive effects on PM emissions control, as the soot oxidation activity is improved and the particle number concentrations are reduced at moderate and high engine loads.

Dual-Fuel Spark Ignition (DFSI) combustion fuelled with different alcohols and gasoline for fuel efficiency

Abstract This paper investigates an experimental study of Alcohols–gasoline Dual-Fuel Spark Ignition (DFSI) Combustion for knock suppression and high fuel efficiency using a gasoline engine with high compression ratio. Alcohols–gasoline DFSI is organized using a port-fuel-injection (PFI) of high oxygenated, high latent heat and high octane number fuel to suppress knock and a direct injection (DI) of high energy density and high volatility fuel to extend high load. Systematical comparison about the effect of stoichiometric M–G (PFI-Methanol and DI-Gasoline), E–G (PFI-Ethanol and DI-Gasoline), E85W15–G (PFI-15% water and 85% ethanol and DI-Gasoline) and G–G (PFI-Gasoline and DI-Gasoline) DFSI on engine knock suppression was conducted. For each test, the percentage of PFI-Alcohol was varied from 0% to 100%. The effects of these combustion modes on knock-limit extension, fuel economy, and combustion characteristics were investigated. Alcohols–gasoline DFSI is a potential approach of using alternative alcohol fuels in practical gasoline engines with significant improvement in engine efficiency and knock suppression. M–G DFSI exhibits better anti-knock performance and achieves higher fuel efficiency than other combustion modes.

Comparative study on alcohols–gasoline and gasoline–alcohols dual-fuel spark ignition (DFSI) combustion for high load extension and high fuel efficiency

This paper presents an experimental study of the alcohols–gasoline and gasoline–alcohols dual-fuel spark ignition (DFSI) combustion for knock suppression and higher engine efficiency using a gasoline engine with high compression ratio. Alcohols–gasoline DFSI is organized using a port fuel injection (PFI) of high oxygenated, high latent heat of vaporization, and high octane alcohol fuel to suppress knock and a direct injection (DI) of high energy density and high volatility fuel to extend engine load, while gasoline–alcohols DFSI is organized by gasoline PFI and alcohol DI. Three different alcohols were studied, including methanol, ethanol, and hydro-ethanol. The engine was naturally aspirated and operated at stoichiometric condition. In each test, the percentage of alcohol injection was varied from 0 to 100%. The effects of these two combustion modes on knock-limit extension, fuel economy, and combustion characteristics were investigated. Both alcohols–gasoline DFSI and gasoline–alcohols DFSI are promising approaches of using alternative alcohol fuels in practical gasoline engines with significant improvement in engine efficiency and knock suppression. Gasoline–alcohols DFSI exhibits better anti-knock performance and achieves higher fuel efficiency than alcohols–gasoline DFSI.

Structure Design and Antiknock Performance Analysis of New Mine Refuge Chamber

In order to solve the potential safety problem due to the explosion of coal mine caused the severe deformation of the front door not being opened normally and the emergency escape hatch was designed unreasonably, three types of structure model with emergency escape hatch being set in transition compartment as entrance and different locations of life supporting compartment as exit, which can avoid the potential safety problem above mentioned. Numerical simulation of antiknock impact performance of the three refuge cabins were calculated and analyzed by using the finite element software of LS-DYNA.The results indicated that the antiknock performance of structures could reach specifications, which could provide a new idea for the development of mine refuge chamber cabin.

Numerical simulation of failure modes of concrete gravity dams subjected to underwater explosion

The failure modes of concrete gravity dams under blast loading are the key problems to evaluate the antiknock safety of the dam. Dynamic failure process of structures under blast loading is much more complicated than that under other loadings such as static and earthquake loadings. Many researchers have conducted comprehensive experimental and numerical investigations of civil structures’ response to blast loading. However, corresponding studies of concrete gravity dams are limited. This paper performs numerical simulation of antiknock performance and failure modes of concrete gravity dams under blast loading. Firstly, the pressure and impulse produced by underwater explosion are calculated. The numerical results are verified by comparing with analytical expressions in different scaled distances. By analyzing the effects of mesh size, some interesting conclusions regarding the mesh size for actual events are obtained. Subsequently, the possible failure modes of concrete gravity dams subjected to underwater explosion are discussed. Strain rate effect of concrete materials is also taken into consideration in establishing the fully coupled model of the gravity dam. The dynamic response of the dam subjected to underwater explosion is performed for different dam heights, varying from 30 to 142m. The influence of the dam height, standoff distance and the upstream water level on the antiknock performance of the dam is also investigated.

Design and Antiknock Impact Performance Analysis of New Mine Refuge Chamber Cabin of Waterproof and Antitoxic

The emergency escape hatches of refuge cabin are usually installed in both sides of the life supporting compartment, which might cause the toxic gases or water enter into life supporting compartment when the gas explosion and water inrush accident occur. A new type of refuge cabin structure that can effectively resist the toxic gases and water entering the life supporting compartment is developed in this paper. Numerical simulation of antiknock impact performance of the new refuge cabin was calculated and analyzed by using the finite element software of LS-DYNA.The stress and strain distributions and maximum antiknock performance were obtained. Refuge chamber cabin has been optimized to reduce cost. The antiknock impact performance of optimized mine refuge chamber cabin can reach 1.4MPa which is greater than the 0.6MPa of standard value and the cost can be reduced approximate 19% than the original model.

The Implosion Performance Analysis of the Tube Truss Roof Based on Measured Defects

In order to analyze the mechanical properties of the steel truss roof burst in the case of defective within, the use of non-linear display dynamic finite element analysis software ANSYS / LS-DYNA to study the different effects of different random defect structure. The measured defect data is obtained by a construction tube truss roof structure .To accord to the random sampling method, defects randomly distributed and the parametric statistical information is to establish. Defect structure antiknock performance is derived, considering the tube truss structure roofing layer, and unconsidering the two simulation models for pipe truss structure roofing layer, and taking into account the rod defects affect the dynamic characteristics of tube truss structure to explosivesposition, explosives equivalent parameters by analyzing and comparing the different parameters of the explosion of the power of the tube truss structure response. Roof layer, the location of the explosion, explosives equivalent with tube truss structure antiknock performance relationship and the weak position of the structure is determined to ensure that the building security to provide a theoretical basis . The results show that the tube truss structure system when the explosion shock wave loads, its dynamic response is a very complex process, the role of the explosion shock wave loading, pipe truss the plastic development process and the structure of the internal location of the explosion, explosivesweight, defects, and consider whether the the roofing layer has relationship.

Antiknock performance of multicomponent oxygen compound mixtures

Antiknock performance of multicomponent oxygen compound mixtures

Improvement of active site accessibility of resin catalysts by polymer/carrier composites: development and characterisation of monolithic catalytic chromatographic reactors

Synthetic resins are one of the most used catalysts in the production of additives for gasoline fuelled cars. Ethers like MTBE (methyl- t-butylether), TAME ( t-amylmethylether) or ETBE (ethyl- t-butylether) are now widely used to enhance the anti-knock performance of the fuels. Now more than 14,000,000 t per year of the above-mentioned ethers are produced world-wide. On the other hand there is much less use of catalytic ion exchange resins in the production of fine chemicals. Reasons might be selectivity aspects, the availability of resins in a shape which is well suited for technical reactors and a lack of knowledge with respect to the accessibility and stability of the active sites. In this study the preparation and characterisation of polymer/carrier composite components for catalytic applications is described. Monolithic rods for chemical reactions with simultaneous separation were prepared by a precipitation polymerisation process and investigated. The distribution of the cross-linker concentration across the particle radius is calculated based on co-polymerisation parameters and discussed. The active sites are sulfonic acid groups. The distribution of the active sites was measured by scanning electron microscopy. For the cyclisation reaction of 1,4-butanediol to tetrahydrofuran and water the application of rods as a monolithic chemical reactor was demonstrated.

Interpretation of the anti-knock performance ofhydrocarbons in gasoline engines in terms of their combustion characteristics

The information on the combustion characteristics of hydrocarbons, preciously reported, leads to aletter insight into the anti-knock performance of hydrocarbons in gasoline engines. The results show that the overall extent of reaction taking place before ignition relates very closely to the knock-limited performance of the fuel. The effects of the addition of tetracthyl lead and hydrocarbon components whose value in terms of blending octane number is not predictable from the intrinsic octane number, can be readily interpreted from their effects on the extent of pre-flame reactions. Furthermore, the performance changes brought about by alterations in engine speed or operating temperature are shown to be governed by the changes in the resistance to ignition (as judged by the ignition temperature by relationship and also by the influence of mixture strength on this) and with the changes occurring in the extent of pre-flame reaction.

The Significance of Laboratory Octane Numbers in Relation to Road Anti-knock Performance

Fuel composition plays a prominent part in deciding the compression ratio to be adopted for an engine, since composition directly affects the knocking tendencies of motor fuels, and knock in turn imposes a limitation on engine performance. The engine conditions which affect knock are discussed and the fact that all fuels do not react equally to these conditions is dealt with in some detail. Laboratory and road knock rating methods are described, and results of tests on a number of fuels and cars, both in Great Britain and in the United States of America are used to demonstrate a relationship between laboratory and road antiknock ratings. It is shown that the road anti-knock performance of fuels is directly affected by their “sensitivity”, to a greater or lesser degree depending on engine “severity”. Severe engines are at a disadvantage in not being able to make full use of the high Research Method Ratings of sensitive fuels, and the factors in engine design and operation which cause high severity are discussed. It is emphasized how necessary it is to produce designs of engines of lower “severity”.