Spark Ignition Internal Combustion Engine Research Articles

Estimation of the mean effective pressure of a spark ignition internal combustion engine using a neural network, considering the wall-wetting dynamics

The management and development of internal combustion engines stand as critical pursuits within the automotive and related industries. Utilizing cylinder pressure as feedback, engine controllers rely on intricate systems to regulate performance. However, due to the inherent complexity and nonlinearity of engines, direct measurement of cylinder pressure through pressure sensors is costly and computationally demanding. Consequently, the need for accurate and detailed engine models becomes paramount. Neural networks offer a promising avenue for simulating internal combustion engines, combining speed and precision. By treating the engine as an enigmatic entity, neural networks can construct detailed models. This study aims to employ two types of neural networks—multilayer perceptron and radial basis functions—to train and build a model of an internal combustion engine. These networks will simulate and estimate the engine's mean suitable pressure, allowing for a comparison of their effectiveness. Prior to implementing the neural network architecture, an engine model was constructed in MATLAB to gather necessary training data. This preliminary step ensured a robust foundation for subsequent network design and implementation. In summary, this research focuses on leveraging neural networks to model internal combustion engines, utilizing both multilayer perceptron and radial basis functions to simulate engine behavior and estimate mean suitable pressure.

Machine learning models for the prediction of turbulent combustion speed for hydrogen-natural gas spark ignition engines

The work carried out in this paper focused on “Machine learning models for the prediction of turbulent combustion speed for hydrogen-natural gas spark ignition engines”. The aim of this work is to develop and verify the ability of machine learning models to solve the problem of estimating the turbulent flame speed for a spark-ignition internal combustion engine operating with a hydrogen-natural gas mixture, then evaluate the relevance of these models in relation to the usual approaches. The novelty of this work is the possibility of a direct calculation of turbulent combustion speed with a good precision, using only machine learning model. The obtained models are also compared to each other by considering in turn as a comparison criterion: the precision of the result, calculation time, and the ability to assimilate original data (which has not undergone preprocessing). An important particularity of this work is that the input variables of the machine learning models were chosen among the variables directly measurable experimentally, based on the opinion of experts in combustion in internal combustion engines and not on the usual approaches to dimensionality reduction on a dataset. The data used for this work was taken from a MINSEL 380, a 380-cc single-cylinder engine. The results show that all the machine learning models obtained are significantly faster than the usual approach and Random Forest (R2: R-squared = 0.9939 and RMSE: Root Mean Square Error = 0.4274) gives the best results. With a forecasting accuracy of over 90 %, both approaches can make reasonable predictions for most industrial applications such as designing engine monitoring and control systems, firefighting systems, simulation, and prototyping tools.

Computational Fluid Dynamics of Four Stroke In-Cylinder Charge Behavior at Distinct Valve Lift Opening Clearance in Spark Ignition Reciprocating Internal Combustion Renault Engine

In-cylinder flow dynamics in internal combustion Renault engine is complex, expensive and difficult to compute experimentally. The present study attempts to emulate the in-cylinder charge behaviour at distinct valve lift opening clearance in four stroke spark ignition internal combustion engine using computational fluid dynamics. Considering the complexity of the geometry and in-cylinder fluid motion, governing equations for unsteady, three dimensional, compressible turbulent flow were computed with continuity equations (conservation of mass), Navier-Stokes equations (conservation of momentum) and RNG k-ε turbulence model. Assumed to be an inline spark ignition (SI) operating on a four stroke cycle, the engine was modelled with SolidWorks 2019 version while the in-cylinder charge behaviour was simulated using ANSYS Fluent 14.5. Increase in cylinder temperature enhanced the thermal properties of air-fuel mixture during combustion. Increase in valve lift opening clearance led to more charge quantity being ingested through the intake valve opening into the cylinder, thereby causing increase in temperature of in-cylinder charge as well as significant improvement in the volumetric and mechanical efficiency of the cycle. It was also observed that the rate of heat retention in the cylinder may be optimum at lower valve lift which may be characterised by minor or zero loses, while significantly high cylinder charge temperature may be prone to reduction of the intake charge density. Based on Particle Image Velocimetry (PIV), in-cylinder velocity vectors, vorticity magnitudes and distributions of turbulence kinetic energy (TKE) increased with increasing valve lift opening clearance, thereby, improving combustion efficiency, increasing torque and power output for effective engine performance.

Towards carbon-free mobility: The feasibility of hydrogen and ammonia as zero carbon fuels in spark ignition light-duty vehicles

Global warming is a major environmental issue caused by the release of greenhouse gases, such as carbon dioxide into the atmosphere. Light-duty vehicles (LDVs) including passenger cars and light-duty trucks, are a significant contributor to greenhouse gas emissions. The transportation sector is responsible for approximately 23% of global CO2 emissions, with LDVs accounting for a substantial portion of these emissions. This paper aims to investigate the feasibility of zero-carbon fuels with focus on hydrogen and ammonia in spark ignition internal combustion engines for light-duty vehicles. With the increasing demand for sustainable and carbon-free mobility, alternative fuels such as hydrogen and ammonia are gaining attention as potential solutions. The properties and characteristics of these fuels and their potential for utilising them as a fuel in internal combustion engines are also reviewed. Current challenges and opportunities associated with the use of these fuels, including production, storage, and distribution, will be discussed. While there are still technical and infrastructural challenges that need to be addressed, hydrogen and ammonia have the potential to provide clean and efficient energy sources for light-duty vehicles. The development of these fuels, along with advancements in internal combustion engine technology, can help pave the way towards a carbon-free future for mobility.

Combustion and specific fuel consumption evaluation of a single-cylinder engine fueled with ethanol, gasoline, and a hydrogen-rich mixture

This study evaluates the effects of adding a hydrogen gaseous mixture (HGM) to primary fuel in a single cylinder research engine (SCRE). Storage and transportation of high-purity hydrogen limit the application of this gas. With the development of fuel reforming methods, using hydrogen-enriched mixtures in spark-ignited internal combustion engines is a convenient option to fossil fuels. Ethanol and gasoline were used as primary fuel by direct injection (DI), and gaseous mixture was added by fumigation system (FS). The experimental analysis was developed in Spark Ignition (SI) four-stroke engine 4 valves and 0.45 L of cubic capacity. For each operation condition and primary fuel, spark timing and amount of HGM were adjusted in order to keep air-fuel ratio stochiometric (λ = 1,00). However, the spark timing and the percentage of gas varied, aiming to evaluate the behavior of the air-fuel mixture. It was evaluated the specific fuel consumption and the evolution of the combustion process. The results showed that the addition of reformed gas promotes acceleration of the combustion process ethanol and gasoline. Results were expressive when using ethanol. A reduction in fuel-specific consumption - for this fuel - with combustion centralized, which did not occur when gasoline was employed.

STUDY OF THE INFLUENCE OF MISFIRES ON THE UNEVEN ROTATION OF THE CRANKSHAFT OF A GASOLINE ENGINE

Purpose. Investigate the effect of misfires on the unevenness of the torque on the crankshaft of gasoline internal combustion engine with spark ignition.
 Research methods. The results of the thermodynamic calculation of the operating cycle, the dynamic calculation of the engine parameters at the nominal operating mode of an well engine and an engine with misfiring in one cylinder are presented. The computer program Engine Calculation and Microsoft Office program package were used to perform the research. The object of the study is the MeMZ-245 four-stroke, four-cylinder gasoline engine. The subject of the study is the torque unevenness coefficient of the internal combustion engine μ.
 Results. The topical issue of investigating the impact of misfires on the indicators of unevenness of rotation of the crankshaft of a spark-ignition internal combustion engine has been solved. The torque unevenness coefficient μ = 6.164 for the MeMZ-245 4-stroke 4-cylinder engine when operating at the nominal mode was calculated. It was established that as a result of a malfunction (disabling one cylinder), the average effective torque of the engine decreases by 29.4%. The value of the torque unevenness coefficient of the faulty engine was calculated as μ = 12.165, which is twice the value for the well-worked engine. It was established that level of torque unevenness of MeMZ-245 4-cylinder in-line engine with misfiring approaches to single-cylinder engines.
 Scientific novelty. For the first time, it was theoretically proven that due to the lack of ignition in one of the cylinders of a 4-stroke 4-cylinder engine, the average effective torque of the engine decreases by 29.4% when operating at the nominal mode. The value of the torque unevenness coefficient μ of an engine with misfiring is twice the value for a well-worked engine, which is close to similar values of single-cylinder engines.
 Practical value. The method of calculating the torque unevenness coefficient of an internal combustion engine can be used in the design of new and modernization of existing internal combustion engines.

Piston geometry and stroke optimization for high efficiency propane spark ignition engines

Propane has unique properties and offers interesting characteristics for high-efficiency spark ignition engines. Its high volatility reduces or completely eliminates fuel-wall wetting and facilitates fuel air mixing. Furthermore, propane has a research octane number of 112 and a high octane sensitivity of 15. Finally, its laminar flame speed is on the same order as that of conventional gasoline, and it exhibits high dilution tolerance. Modern spark ignition internal combustion engines rely on fast combustion rates and high dilution to achieve high brake thermal efficiencies. To accomplish this, high stroke-to-bore ratios and high geometric compression ratios have been used in new engine designs. Therefore, propane’s relatively high laminar flame speeds, high knock resistance, and dilution tolerance make it an excellent candidate fuel for modern spark ignition engines. The objective of this work is to co-optimize the piston geometry and the engine stroke to maximize the efficiency of a spark-ignition engine fueled with propane. 3D computational fluid dynamics (CFD) simulations employing the extended coherent flamelet model were used to study the parametric effects of piston shape and stroke length. A piston geometry based on high performing pistons was parameterized using four controlling parameters. The piston geometry and engine stroke design space was explored using deterministic and quasi-random sampling techniques. A Gaussian process regression model was built using the simulation data to explain the results observed.

The Effects of Syngas Composition on Engine Thermal Balance in a Biomass Powered CHP Unit: A 3D CFD Study

Syngas from biomass gasification represents an interesting alternative to traditional fuels in spark-ignition (SI) internal combustion engines (ICEs). The presence of inert species in the syngas (H2O, CO2, N2) reduces the amount of primary energy that can be exploited through combustion, but it can also have an insulating effect on the cylinder walls, increasing the average combustion temperature and reducing heat losses. A predictive numerical approach is here proposed to derive hints related to the possible optimization of the syngas-engine coupling and to balance at the best the opposite effects taking place during the energy conversion process. A three-dimensional (3D) computational fluid dynamics (CFD) model is developed, based on a detailed kinetic mechanism of combustion, to reproduce the combustion cycle of a cogenerative engine fueled by syngas deriving from the gasification of different feedstocks. Numerical results are validated with respect to experimental measurements made under real operation. Main findings reveal how heat transfer mainly occurs through the chamber and piston walls up to 50° after top dead center (ATDC), with the presence of inert gases (mostly N2) which decrease the syngas lower calorific value but have a beneficial insulating effect along the liner walls. However, the overall conversion efficiency of the biomass-to-ICE chain is mostly favored by high-quality syngas from biomasses with low-ashes content.

Numerical investigation on gaseous fuel injection strategies on combustion characteristics and NO emission performance in a pure hydrogen engine

With the proposal of “dual-carbon” goals and increasingly stringent emission regulations, hydrogen as a zero-carbon alternative fuel has great potential in engine applications. In the appliance of pure hydrogen engines, direct injection plus lean burn technology can effectively improve engine performance and reduce emissions. Therefore, this work establishes a three-dimensional (3D) simulation model of the pure hydrogen spark-ignition internal combustion engine (ICE) coupled with chemical reaction kinetics. Then, the applicability of different commonly used hydrogen simplified mechanisms to characterize the combustion process based on experimental data is evaluated, and the feasibility of the transient calculation model is verified. Then, the engine combustion and emission performance are compared by adopting hydrogen port injection (HPI) and hydrogen direct injection (HDI) strategies. Meanwhile, the effects of hydrogen injection timing (HIT) on flow, combustion and nitric oxide (NO) emission processes under direct injection plus lean burn mode are analyzed. The results show that: 1. For mixture distribution at ignition timing (IT), the hydrogen should be distributed near the spark plug and avoid its concentration being too rich since the richer mixture will lead to intense combustion and rapid heat release. 2. When using HDI mode, the engine combustion performance and power performance are better than that of the HPI mode. Delaying HIT, the power performance improves under HDI modes, while both the indicated thermal efficiency (ITE) and indicated mean effective pressure (IMEP) reached the maximum at Case6-HDI-100 with the values are 40.52 % and 0.498 MPa, respectively. 3. Considering the engine combustion, power and emission performance, Case6-HDI-100 (HIT at 100 °CA BTDC) is the preferred scheme. Its ITE and IMEP are 8.49 % and 37.33 % higher than that of Case1-HPI (HPI mode scheme) and 6.50 % and 14.95 % higher than that of Case4-HDI-220 (the lowest scheme under HDI mode), respectively, while nitrogen oxide (NOx) emissions meet the European Stage V non-road emission standards. This study provides some reference values for the combustion design of pure hydrogen ICEs.

Proposal and validation of a numerical framework for 3D-CFD in-cylinder simulations of hydrogen spark-ignition internal combustion engines

In the light of the recent standards proposed by the European Union in terms of CO2 emissions for the internal combustion engines, the attention is increasingly focused on e-fuels, among which the renewable-produced hydrogen. The present paper proposes a numerical methodology for 3D-CFD in-cylinder simulations of hydrogen-fuelled internal combustion engines. The proposed framework includes in-house developed models for ignition, knock and heat transfer and it is based on the G-equation combustion model. The predictive capabilities of the methodology are validated against experimental data on a single-cylinder naturally-aspirated diesel engine converted for spark-ignited hydrogen operation. Specifically, H2 is direct injected thanks to two injectors installed on the cylinder head. Moreover, a spark plug is added and the compression ratio is lowered. The investigated conditions cover different revving speeds (from 1500 rpm to 3000 rpm) and equivalence ratios (0.4, 0.6 and 0.8). The satisfying agreement between numerical results and experimental counterparts paves the way to future studies (e.g. on emission modelling) and engine optimization.

An Integrated Engine Control Unit for a Spark Ignited Internal Combustion Engine

A stepping valve system has been proposed before and proved to be feasible. The stepping valve move perpendicular to the piston, thereby avoiding piston-valve collisions associated with interference engines. In this study, the proposed Stepping Valve Control Unit, SVCU, was integrated with the conventional Engine Control Unit, ECU, of a simple SI engine. The resulting Integrated Engine Control Unit, IECU, as it is called, simplified the design of the ECU. The integration involved combining the basic fuel injector and sparking controls with the SVCU. The camshaft and crankshaft sensors were replaced by a Piston Direction Sensor, PDS. The PDS is an optical sensor, which works in conjunction with a gray coded trigger wheel to relay information to the IECU. The IECU was simulated using Quartus II design software. The hardware implementation of the IECU was done using EPM7128SL FPGA contained within the UP1 Altera Development Board. The behavior of the IECU was expected.

Study on SI Engine Operation Stability at Lean Condition—The Effect of a Small Amount of Hydrogen Addition

The lean-burn mode is a solution that reduces the fuel consumption of spark-ignition internal combustion engines and keeps the low exhaust emission, but the stability of the lean-burn combustion process, especially at low loads, needs to be addressed. Enhancing gasoline with hybrid hydrogen oxygen (HHO) gas—a mixture of hydrogen and oxygen gases—is proposed to improve combustion of the lean-gasoline mixture. A three-cylinder, spark-ignition, naturally aspirated, MPI engine with HHO gas produced with an alkaline water electrolyzer and introduced as a gasoline enhancement was tested. The amount of hydrogen added to the lean-gasoline mixture (λ = 1.4) was in the range from 0.15 to 1.5%, and the results were compared to the stoichiometric (λ = 1) and pure lean mode (λ = 1.4) gasoline operation. The other authors’ results show that a minimum 3% of the mass fraction of hydrogen is necessary to affect the gasoline combustion process. This paper proved that even a small hydrogen enhancement of gasoline in the amount of 0.3% of the mass fraction improves the combustion stability.

CFD-based methodology for the characterization of the combustion process of a passive pre-chamber gasoline engine

Pre-chamber (PC) ignition systems, enabling Turbulent Jet Ignition (TJI) combustion, represent a promising technology to extend the lean limit of Spark Ignition Internal Combustion Engines. Indeed, the higher ignition energy provided by the turbulent jets contributes to the limitation of combustion duration and variability even in diluted conditions. However, a detailed analysis of the combustion process is needed to maximize the performance of the system. More specifically, the interaction between the chemical and the turbulent scales are key factors in assessing the probabilities of main chamber (MC) ignition, determining the ignition pattern, and characterizing the combustion process. For this reason, the development of reliable numerical models is a crucial factor to pave the way toward a deeper understanding of details concerning TJI combustion. In the present work, a 3D-CFD numerical model was validated against experimental data at 4000 rpm, in stoichiometric and lean (i.e., λ = 1.2) conditions in a single-cylinder gasoline engine equipped with a passive pre-chamber. In both operations, the evolution of the turbulent combustion regimes over the whole combustion process was investigated, highlighting analogies and differences between the selected operative conditions. Additionally, a methodology to characterize the MC ignition and combustion process, able to describe the different phases of the interaction between PC and MC, and assess the thermal, turbulent, and chemical effects of the turbulent jets is presented.

Improving the Efficiency of Spark-Ignition Internal Combustion Engine Using a Novel Electromagnetic Actuator and Adapting Increased Compression

This paper presents an empirical study of a spark-ignition internal combustion engine with modifications made to increase its effectiveness. The modification was implemented bi-directionally in terms of changes to the compression ratio and changes to the engine’s valve train. The compression ratio was increased by 2.3 units by design and a hybrid intake valve opening control was used in the engine’s valve train. The hybrid control involved autonomous control of one of the inlet valves with a dedicated electromagnetic actuator. The designed electromagnetic actuator was mounted downstream of the single-cylinder engine’s intake system’s modified camshaft to control the effective compression pressure build-up. Field calculations were carried out for the electromagnetic actuator’s design variants and its current characteristics were determined. The multivariate calculations were carried out in order to find the quasi-optimal geometry of the actuator. The width and height of magnetic field coils and the dimensions of the stator poles were changed, while maintaining the same external dimensions of the actuator to enable its mounting in the cylinder head system. In the next step, the prototype of the actuator was made and placed on the combustion engine in order to conduct the experimental investigations. The work was aimed at improving the internal combustion engine’s efficiency at the low load range, as this is load range in which it has low efficiency despite it being the most often used during normal vehicle operation. The original measurement stand was prepared, and many tests were carried out in order to investigate the influence of the electromagnetic valve on the combustion engine characteristic. This improved the internal combustion engine’s efficiency at its low-load range by up to 25%. Both calculation and measurement results are presented in form of graphs.

The contribution of intermediate-temperature heat release to octane sensitivity

Carbon footprint reduction can be achieved by increasing the efficiency of combustion engines. For spark-ignition (SI) internal combustion engines (ICE), fuel octane sensitivity (OS)—defined as the difference between a fuel’s research octane number (RON) and motor octane number (MON)—can help identify ideal fuels for avoiding unwanted knocking conditions. Moreover, it will help to extend the range of operating conditions that can be used in next-generation high-efficiency engines. Presently, there is a controversy over whether high or low OS fuels are beneficial for increased efficiency of next-generation engines depending on application and technology, e.g. high OS fuels are advantageous for down-sized and turbocharged spark-ignition (SI) engines, whereas low OS fuels are superior in novel systems such as pre-chamber engines. This work aims to improve the understanding of the impact of OS on the combustion performance of engines by analyzing the contribution of intermediate-temperature heat release (ITHR) to OS. The heat release of several mixtures of toluene, iso-octane, and n-heptane with similar RON but varying OS were studied under homogeneous charge compression ignition (HCCI) conditions in a cooperative fuel research (CFR) engine. This method gives insight into the heat release of the auto-igniting fuel without the obfuscation of the spark-ignited flame. At RON conditions, ITHR was a marker of OS. Furthermore, a new parameter called ITHR sensitivity was defined as the difference between the ITHR measured at RON conditions and the ITHR measured at MON conditions. ITHR sensitivity decreased with increasing octane sensitivity. This shows that non-sensitive fuels experience a greater change in the amount of ITHR as compared to sensitive fuels when changing from MON conditions to RON conditions. Thus, for engines requiring high OS fuels, it is recommended that components with high ITHR sensitivity are used and vice-versa for engines requiring low OS fuels.

A Comparison of Well-to-Wheels Energy Use and Emissions of Hydrogen Fuel Cell, Electric, LNG, and Diesel-Powered Logistics Vehicles in China

Global energy and environmental issues are becoming increasingly serious, and the promotion of clean energy and green transportation has become a common goal for all countries. In the logistics industry, traditional fuels such as diesel and natural gas can no longer meet the requirements of energy and climate change. Hydrogen fuel cell logistics vehicles are expected to become the mainstream vehicles for future logistics because of their “zero carbon” advantages. The GREET model is computer simulation software developed by the Argonne National Laboratory in the USA. It is extensively utilized in research pertaining to the energy and environmental impact of vehicles. This research study examines four types of logistics vehicles: hydrogen fuel cell vehicles (FCVs), electric vehicles, LNG-fueled vehicles, and diesel-fueled vehicles. Diesel-fueled logistics vehicles are currently the most abundant type of vehicle in the logistics sector. LNG-fueled logistics vehicles are considered as a short-term alternative to diesel logistics vehicles, while electric logistics vehicles are among the most popular types of new-energy vehicles currently. We analyze and compare their well-to-wheels (WTW) energy consumption and emissions with the help of GREET software and conduct lifecycle assessments (LCAs) of the four types of vehicles to analyze their energy and environmental benefits. When comparing the energy consumption of the four vehicle types, electric logistics vehicles (EVs) have the lowest energy consumption, with slightly lower energy consumption than FCVs. When comparing the nine airborne pollutant emissions of the four vehicle types, the emissions of the FCVs are significantly lower than those of spark-ignition internal combustion engine logistics vehicles (SI ICEVs), compression-ignition direct-injection internal combustion engine logistics vehicles (CIDI ICEVs), and EVs. This study fills a research gap regarding the energy consumption and environmental impact of logistics vehicles in China.

Experimental study on Miller cycle hydrogen-enriched ammonia engine by rich-burn strategy

In order to achieve climate goals as soon as possible, it is necessary to reshape the energy mix to replace fossil energy with carbon–neutral fuels as soon as possible. Ammonia is a good medium for energy storage, has a large industrial scale and a well-developed infrastructure. To address the problems of NOx emission and low exhaust energy of ammonia-hydrogen engines, this study proposes a rich burn strategy. Firstly, a commercial spark ignition (SI) internal combustion engine (ICE) was modified to achieve a dual fuel supply of ammonia and hydrogen. The engine was run at a steady state of 1500 rpm with the intake manifold absolute pressure (MAP) maintained at 60 kPa, and the ammonia and hydrogen supplies were adjusted to achieve different mixing ratios and excess air ratios. The experimental results showed that the rich burn strategy could significantly reduce the NOx emission and increase the exhaust temperature of the ammonia-hydrogen engine when the excess air coefficient was below 0.8. The rich burn strategy can appropriately increase the engine power output, but it has some influence on the brake thermal efficiency (BTE).

Ethanol blending in petrol: A techno - commercial overview

Due to fast depletion of fossil fuels, there is a need to explore ways to circumvent or to reduce their use. Largely populated countries like India need to be more concerned about this. In the last decade, India started blending ethyl alcohol (ethanol, EtOH) in petrol (gasoline). Presently Indian petrol suppliers blend about 10 % EtOH by volume, which is expected to rise to 20 % by 2024. Like any engineering solution, ethanol blending is accompanied by own merits and demerits. This review aims at assessing the effect of ethanol blending in spark ignition internal combustion engines based on technical and commercial aspects. Effect of EtOH blending on the engine performance and emission has been discussed in detail. Various parameters related to fuel quality like the concentration of EtOH present and the amount of water present - which affect the performance - are also discussed. EtOH blending affects the emission and compatibility issues might arise which is discussed. Routes of production of EtOH may change the techno - commercial aspects of any process. This aspect is discussed along with the amount of EtOH blended, since this may help in shaping up the future policy decisions. Contradictions and gaps are highlighted to provide a direction for future studies. Indian and global scenario is also discussed to a considerable detail.

Effect of Aniline Derivatives on Auto Ignition of Hydrocarbon Fuels: Mechanistic Insight of Antiknock Activity

In view of rising concerns over global warming it is very important to reduce greenhouse gas emissions and accelerate decarbonization. Worldwide transportation sector has a massive contribution in producing greenhouse gases over periods. So, depletion of GHG emission is of utmost importance. Petroleum refining industries continuously made efforts to control CHG emissions by formulating high octane gasoline fuels which increase vehicle efficiency and enhance fuel economy for spark ignition internal combustion engines. High Octane gasoline fuels helps in reducing knocking of the SI Engine cars and eventually intensify vehicle efficiency and fuel economy. Over the period of time several potential chemical octane boosters were developed to improve the octane number of the standard gasoline fuel. Aromatic Amine derivatives are well known octane boosters. This present review work summaries the available data regarding the mechanistic interpretation of antiknock action of aromatic amines by controlling the auto ignition process of hydrocarbon fuels. Key Words: Fuel Economy, Engine Efficiency, Octane Booster, Resonance, Autoignition, Research Octane Number

Ignition behaviors of primary reference fuels in a rapid compression machine under vortex-existing/minimized conditions

Knock is one of the main obstacles to improving the thermal efficiency of spark-ignition internal combustion engines. Although knock has been widely studied and accepted as a result of end-gas auto-ignition, the fundamentals regarding auto-ignition behaviors are still not fully revealed. In this study, the ignition behaviors of primary reference fuels were investigated in an optical rapid compression machine equipped with a quartz combustion chamber allowing for visualizing the combustion process from the lateral view. By combining both the lateral view and the top view photography, ignition behaviors under vortex-existing conditions with a creviced piston and vortex-minimized conditions with a flat piston were comprehensively analyzed to reveal the impact of the vortex on the ignition behaviors of PRF fuels. The influence of fuel reactivity was also investigated. The results showed that mild ignition was prevalent under large Da* numbers. The occurrence of mild ignition was closely related to the ignition delay time of the mixture, and the critical ignition delay time was not fixed but decreased with increasing initial temperature. The propensity of mild ignition could be boosted under vortex-existing conditions due to the increasing hotspot formation probability. Vortices were demonstrated to be capable of mitigating knock intensity via 1) the buffer effect of surrounding burned regions on the shock waves generated from surrounded unburnt pockets; 2) a larger burned mass fraction at the instant of the final ignition under vortex-existing conditions. The results also showed that strong ignition was more likely to occur under vortex-minimized conditions. Besides, higher fuel reactivity also could increase the probability of strong ignition occurrence. Compared with the creviced piston, the use of the flat piston could shift the ignition regime towards regions with higher Ret and lower Dat in the Dat-Ret diagram, where the strong ignition is less pronounced.