Modern Internal Combustion Engines Research Articles

Development and Validation of a Novel Zero-Dimensional Heat Rejection Model for High-Efficiency Engines

In recent years, the trend towards the performance maximization of modern internal combustion engines has led to the creation of accurate simulation models to optimize the engine design and operating conditions. Temperature management is crucial to achieve the performance goals of an internal combustion engine without affecting the component’s reliability. Formula 1 mandates that only a limited number of experimental tests can be performed, which leads to the necessity of simulators capable of substituting empirical tests. Furthermore, the requirement of adapting the vehicle setup before each race weekend to maximize the performance on each circuit layout necessitates short computational time. To address this, the development of a zero-dimensional model of the thermal flows within an engine is presented in this paper. This model allows to precisely compute the dynamic variations of all the heat flows inside the combustion engine, excluding only the radiative ones and the engine components’ temperatures. The new simulation approach has been developed and validated on a Formula 1 engine and shown to be precise and fast. The results demonstrate the value of the proposed model with an average engine fluid temperature error of less than 1 °C for a computational cost comparable with on-board applications.

Combustion Characteristics of a Hydrogen-Fueled TJI Engine under Knocking Conditions

The use of a two-stage combustion system in a hydrogen-fueled engine is characteristic of modern internal combustion engines. The main problem with hydrogen combustion in such systems is knocking combustion. This paper contains the results of research under knock combustion conditions with a single-cylinder internal combustion engine equipped with a turbulent jet ignition system (TJI). A layout with a passive pre-chamber and a variable value of the excess air ratio range λ = 1.25–2.0 with a constant value of the center of combustion (CoC = 4 deg) after top dead center (TDC) was used. Two indicators of knock combustion were analyzed: maximum oscillation of pressure and the Mahle Knock Index. Analyses were also carried out taking into account the rate of heat release and the amount of heat released. As a result of the investigation, it was found that knock combustion occurs intensively at small values of the air excess ratio. Hydrogen knock combustion disappears for λ = 2.0 and greater. The pressure oscillation index was found to be more applicable, as its limiting value (>1 bar) allows easy diagnosis of knock combustion. The Mahle Knock Index is a quantity that allows interval analysis of the knock. The choice of classes and weighting coefficients requires an iterative operation, as they strictly depend on engine characteristics, load, and knock magnitude.

On the influence of different alcohol-type biofuels on performance and engine emissions of an SI engine

Greenhouse gas emissions (G.H.G.) from vehicles are the main source of pollution. In this transition period from fossil fuels to the use of synthetic fuels, the diversification of alternative fuels used to fuel internal combustion engines is seen as one of the best alternatives for reducing G.H.G. In Europe, conforming to the stringent emission reduction targets for 2030, as well as trying to fulfil the regulations of the new Euro VII standard will force engine manufacturers to adopt alternative fuel solutions with a low environmental impact. However, fossil fuels will continue to be used but alternative fuels will substantially decrease our dependence on petroleum-derived fuels. Modern simulation software tools make it easy to produce a fairly accurate analysis of how an internal combustion engine works without the need for prototyping. Packages such as Ricardo WAVE or AVL Boost, are relatively cheap and represent accessible tools for developing, designing, and testing modern internal combustion engines. AVL Boost is a widely used engine simulation tool a 1D (one-dimensional) simulation software that allows engineers and researchers to model, simulate, and optimize various internal combustion engines, including spark ignition (SI) engines, diesel engines, and hybrid powertrains. The software also offers a high degree of flexibility in terms of alternative fuel blends. This paper evaluates the influences of using alcohol-based biofuels on performance metrics and pollutant emissions, such as brake power, brake thermal efficiency, and emissions, such as CO, CO2, and NOx in a spark ignition engine. The effects of varying alcohol fractions in the gasoline-alcohol blends on engine performance and emissions are analysed and explained. In this study, several types of ethanol in gasoline blends were simulated (E25, E50, E85). The one-dimensional model of the tested engine was developed based on the design dimensions of the 1.2L TCe H5FT engine produced by Renault. In the context of maintaining constant engine power output, the findings from the simulation results indicate that the utilization of alcohol-based blends with a high volumetric percentage of alcohol (ranging from 70-90%) can result in a substantial increase in fuel consumption, particularly in the case of methanol blends. Consequently, this phenomenon is associated with an elevated emission of carbon dioxide (CO2). However, it should be noted that despite this drawback, there is evidence of an inclination towards reduced emissions of other pollutants due to the enhanced combustion processes facilitated by the higher ratio of oxygenated compounds and a lower peak temperature. Methanol, one of the two alcohols investigated in this study, is not recommended for usage in fuel blends for several reasons. Firstly, the consumption rate of methanol is higher compared to ethanol, which can result in increased fuel usage. Secondly, methanol poses health risks due to its toxicity at certain levels, posing potential hazards in handling and utilization. Moreover, high concentrations of methanol are not easily miscible with gasoline without the addition of co-solvents, further limiting its feasibility as a viable fuel component.

Particulate Filters for Combustion Engines to Mitigate Global Warming. Estimating the Effects of a Highly Efficient but Underutilized Tool

AbstractParticulate filters are state-of-the-art and are used in internal combustion engines worldwide to eliminate carcinogenic nanoparticles. Health studies estimate that this prevents about one million premature deaths annually. What is less known and often neglected is their equally powerful effect on mitigating global warming. This is because these ultrafine particles form stable aerosols in the atmosphere, absorb sunlight, and heat the atmosphere due to their jet-black color. In addition, once deposited on the ground, they reduce albedo especially when deposited on ice or snow. They also thin clouds and reduce their reflectivity. In this paper, we estimate for the first time the cumulative effect of more than 300 million particulate filters currently installed globally on vehicles, showing that, while they reduce ~ 0.5 Mt of soot per year, their effect on slowing global warming is equivalent to reducing 1 Bt of CO2 per year or about one-third of the CO2 emissions of all European Union Member States combined. Despite its strong potential, this highly efficient, proven, and low-cost technology is not yet regarded as a priority in curbing global warming, even though it is possibly the easiest and quickest to implement. If used in retrofitting more diesel and petrol engines worldwide, it could triple the aforementioned effect. While modern internal combustion engines are on track to be replaced with zero-emission vehicles, it is also crucial, and we strongly suggest that, in the interim, all remaining internal fossil fuel combusting engines be fitted with particulate filters. Evidence is presented in this paper that the potential benefits of such retrofit on climate and human health will be impactful and lasting.

The Significance of Al-Jazari's Four-Bucket Water Lifting Machine in the History of Engineering and Science

The developments in the field of engineering have an eclectic structure. During ancient times, the works carried out at the School of Mechanical Engineering in Alexandria were transmitted to the Islamic world through translations at the House of Wisdom (Bayt al-Hikmah). Following this process, engineering studies became the focus of research in the Islamic world, both from theoretical and practical perspectives. Prominent researchers in this context include the Banu Musa brothers (9th century), Al-Farabi (875-950), Al-Hazini (1100s), and Al-Jazari (13th century). The renowned Turkish philosopher Al-Farabi conducted research on air and vacuum, expressing his views in the treatise "Risale li-Ebi Nasr al-Farabi fi’l-Hala" (On Vacuum). Al-Hazini's book "Mizanu’l Hikme" (The Balance of Wisdom) sheds light on the concept of balance, with Hazini turning the water balance into an extraordinary equilibrium device and creating a balance called "Mizânü'l-Câmî" (The Collector).The Banu Musa brothers presented valuable machine and mechanical system designs in their work "Kitab al-Hiyal" (The Book of Ingenious Devices). Al-Jazari, born in 1153 in Cizre, served as the chief engineer of the Artuklu palace for 32 years. During this time, he designed many mechanical and automation-based systems. Upon examining the designs in Al-Jazari's book "Kitab-ül Cami Beyn-el-İl ve'l-Amel el-Nâfi fi Sınaât el Hiyel," it becomes apparent that he elevated the designs made before him to a completely different level. Some of today's engineering designs can trace their origins to the drawings found in this book. In this study, the design features of Al-Jazari's 4-bucket water-lifting machine are examined, and its value in contemporary engineering is explored. Al-Jazari designed a mechanical timer to ensure the continuity of water flow in his design. This timer allowed each bucket to discharge water one after the other, maintaining a continuous flow of water. He achieved this through a shaft with quarter-toothed gears. This design can be considered the precursor to the eccentric and crankshafts found in modern internal combustion engines. The eccentric shaft controls the mechanical timing of valves in engines, while crankshafts ensure the continuous transmission of the force generated by four pistons in a four-stroke engine over a quarter of the cycle to the flywheel gear.

Numerical Analysis to Investigate the Impact of Skirt Geometric Parameters on Secondary Piston Movement in a Single-cylinder Diesel Engine

Currently, modern internal combustion engines are receiving great attention due to their efficiency, particularly in response to the increasing limits imposed by environmental and emission legislation. Sound emissions of internal combustion engines are mainly caused by three sources of noise: combustion, mechanical and aerodynamic flow. The secondary motion of the piston plays a crucial role in the analysis of performance, noise, vibration and reliability of internal combustion engine (ICE). In the presented article, a mathematical simulation model has been developed by using of the GT-Suite software to study the rotational and lateral motion of the piston (called secondary motion) as well as the piston slap in ICE. This model takes into account the effect of variation in the major geometric parameters of the skirt design, such as the piston pin offset (P.P.O) and the length of the skirt. Furthermore, a combined model that accounts for the interplay between the secondary dynamics of the piston and the dynamic fluid lubrication has been developed. This model utilizes a mixed lubrication approach for the purpose of simulation. The results of this simulation have demonstrated that the variations in length of the skirt and the P.P.O have a considerable effect on piston secondary motion and tribological performances, and that the lateral motion of the piston is significantly influenced by the piston side force, which plays a crucial role in this behavior.

Advanced, Guided Procedure for the Calibration and Generalization of Neural Network-Based Models of Combustion and Knock Indexes

<div>In the last few years, the artificial neural networks have been widely used in the field of engine modeling. Some of the main reasons for this are, their compatibility with the real-time systems, higher accuracy, and flexibility if compared to other data-driven approaches. One of the main difficulties of using this approach is the calibration of the network itself. It is very difficult to find in the literature procedures that guide the user to completely define a network. Typically, the very last steps (like the choice of the number of neurons) must be selected by the user on the base of his sensitivity to the problem.</div> <div>This work proposes an automatic calibration procedure for the artificial neural networks, considering all the main hyper-parameters of the network such as the training algorithms, the activation functions, the number of the neurons, the number of epochs, and the number of hidden layers, for modeling various combustion indexes in a modern internal combustion engine. However, the proposed procedure can be applied to the training of any neural network-based model.</div> <div>The automatic calibration procedure outputs a configuration of the network, giving the optimal combination in terms of hyper-parameters. The decision of the optimal configuration of the neural network is based on a self-developed formula, which gives a rank of all the possible hyper-parameter combinations using some statistical parameters obtained comparing the simulated and the experimental values. In the end, the lowest rank is selected as the optimal one as it represents the combination having the lowest error. Following the definition of this rank, high accuracy on the results has been achieved in terms of the root mean square error index, for example, on the combustion phase model, the error is 0.139°CA under steady-state conditions. On the maximum in-cylinder pressure model, the error is 1.682 bar, while the knock model has an error of 0.457 bar for the same test that covers the whole engine operating field.</div>

Evaluation of the effectiveness of air heating of the icebreaker anti-icing device at the compressor inlet

Anti-icing devices that provide increased ice penetration are widely used on modern icebreakers. The devices based on the pneumatic pressurization of the icebreaker hull with air pumped by a special compressor are most common. When operating at low temperatures, there is a danger of compressor failure due to icing of the compressor intake tract. To protect the receiving path, it is necessary to increase the temperature of the air entering the compressor to safe values. Possible heating methods are recirculation of compressed air in the compressor and its heating in a special heat exchanger. A diagram of an anti-icing system that allows you to implement both methods of air heating is presented in the paper; the principle of its operation is described. An urgent problem of selecting the most preferred method of air heating is considered in the paper. As an evaluation criterion, it is proposed to use the energy costs necessary to ensure air heating, cooling parameters of modern internal combustion engines with a high level of boost and advanced engines. To solve this problem, an algorithm that takes into account the features of the operation of the anti-icing device compressor, the requirements for the temperature of the receiving air, the properties of heat carriers is proposed. The calculation method is based on the classical equations of thermodynamics and heat transfer. The results of the calculations performed allow us to compare the energy costs for ensuring an increase in air temperature to the required values when using various methods of heat supply. The conclusions drawn on the basis of the calculations carried out allow us to conclude that the most rational way to warm up the intake air of the compressor of the anti-icing device is the joint use of recirculation and a heat exchanger. A promising direction for improving anti-icing devices is the optimization of the temperature modes of the compressor operation, rationalization of the supplied heat distribution, automation of the control for the temperature regime of the pneumatic boost. 

Data-driven enabling technologies in soft sensors of modern internal combustion engines: Perspectives

Data-driven enabling technologies in soft sensors of modern internal combustion engines: Perspectives

Legal Framework for Modern Internal Combustion Engine Drives

Legal Framework for Modern Internal Combustion Engine Drives

Hydrogen Application as a Fuel in Internal Combustion Engines

Hydrogen is the energy vector that will lead us toward a more sustainable future. It could be the fuel of both fuel cells and internal combustion engines. Internal combustion engines are today the only motors characterized by high reliability, duration and specific power, and low cost per power unit. The most immediate solution for the near future could be the application of hydrogen as a fuel in modern internal combustion engines. This solution has advantages and disadvantages: specific physical, chemical and operational properties of hydrogen require attention. Hydrogen is the only fuel that could potentially produce no carbon, carbon monoxide and carbon dioxide emissions. It also allows high engine efficiency and low nitrogen oxide emissions. Hydrogen has wide flammability limits and a high flame propagation rate, which provide a stable combustion process for lean and very lean mixtures. Near the stoichiometric air–fuel ratio, hydrogen-fueled engines exhibit abnormal combustions (backfire, pre-ignition, detonation), the suppression of which has proven to be quite challenging. Pre-ignition due to hot spots in or around the spark plug can be avoided by adopting a cooled or unconventional ignition system (such as corona discharge): the latter also ensures the ignition of highly diluted hydrogen–air mixtures. It is worth noting that to correctly reproduce the hydrogen ignition and combustion processes in an ICE with the risks related to abnormal combustion, 3D CFD simulations can be of great help. It is necessary to model the injection process correctly, and then the formation of the mixture, and therefore, the combustion process. It is very complex to model hydrogen gas injection due to the high velocity of the gas in such jets. Experimental tests on hydrogen gas injection are many but never conclusive. It is necessary to have a deep knowledge of the gas injection phenomenon to correctly design the right injector for a specific engine. Furthermore, correlations are needed in the CFD code to predict the laminar flame velocity of hydrogen–air mixtures and the autoignition time. In the literature, experimental data are scarce on air–hydrogen mixtures, particularly for engine-type conditions, because they are complicated by flame instability at pressures similar to those of an engine. The flame velocity exhibits a non-monotonous behavior with respect to the equivalence ratio, increases with a higher unburnt gas temperature and decreases at high pressures. This makes it difficult to develop the correlation required for robust and predictive CFD models. In this work, the authors briefly describe the research path and the main challenges listed above.

Study on the frictional properties of the top ring-liner conjunction for different-viscosity lubricant

In modern internal combustion engines, the lubricant viscosity affects greatly the friction power loss. To obtain maximum fuel economy of the engines, the lubricants with different viscosities are considered to evaluate the friction properties of the compression ring-cylinder liner conjunction in the engines in this study. To conduct the evaluation, an improved mixed lubrication model is developed with considerations of the cylinder liner deformation, the lubricant thermal effect & transportation, and the change of lubrication condition from full flooded to starve. On this basis, the influence of different viscosity lubricants on the minimum oil film thickness, friction, power loss, FMEP, and wear load are investigated. The numerical result indicates that the low viscosity lubricant is more beneficial to facilitate the change of lubrication condition from starve to fully flooded. Furthermore, the low viscosity lubricant will result in large wear load on the compression ring surface while reducing the friction power loss.

Improvement of exhaust emissions in a diesel engine with the addition of an oxygenated additive to diesel-biodiesel blends

Emissions control in internal combustion engines is the big challenge faced by engine manufacturers. Modern internal combustion engines exploit various systems to reduce exhaust emissions. However, the existing emission control systems will fall short of meeting stringent future emission regulations. This study attempts to reduce the exhaust emissions of a diesel engine fuelled with diesel-biodiesel blends by utilising ethyl acetate as a renewable oxygenated fuel additive. In this context, initially, ethyl acetate is mixed with biodiesel-diesel blends by 5% and 10% volume to obtain test fuels. Then, their fuel properties are measured by applying test methods proposed in the standards. Subsequently, engine experiments are conducted on a single-cylinder four-stroke diesel engine operated on distinct test conditions. The findings indicate that the inclusion of ethyl acetate in the diesel-biodiesel blends improves the fuel quality and markedly decreases emissions. A substantial reduction is achieved in NOX, soot, and CO emissions up to 50%, 70%, and 71%, respectively, with a slight increase in fuel consumption in the case of adding ethyl acetate. More importantly, the addition of ethyl acetate enhances the NOX-smoke trade-off and NOX-BSFC trade-off characteristic of a diesel engine without loss of thermal efficiency. From this research, it can be inferred that ethyl acetate can potentially reduce exhaust emissions of the existing diesel engines fuelled with diesel-biodiesel blends.

On the question of secondary use of exhaust exergy in power units of vehicles and tractors

BACKGROUND: Efficiency of modern internal combustion engines is no more than 40%, while the significant part of exergy, released during fuel combustion, dissipates in the environment through exhaust, coolant liquid and heated details. Meanwhile, the urgent problem of operating a tractor in low ambient temperature conditions is sustaining of optimal thermal condition for the sake of decreasing of losses, increasing of combustion efficiency and, as a consequence, increasing of operating efficiency.
 AIMS: Efficiency assessment of use of the complex system of utilization of thermomechanical exergy of diesel engine exhaust. Justification of type and number of stages of exhaust exergy utilization for diesel engines of vehicles and tractors for a wide range of ambient temperatures and loading conditions.
 METHODS: To accomplish given aims, theoretical and experimental studies were carried out in order to assess exhaust exergy potential in dependence on engine loading conditions and ambient temperature. Comparative studies of the D-440 and the SMD-62 engines were carried out, making it possible to assess the influence of exhaust system design features on amount of exergy losses.
 RESULTS: Exhaust performance losses of the SMD-62 engine with the TKR-11N-1 turbocharger at nominal mode were 0.8. Meanwhile, maximal exhaust performance losses at idle mode are 0.92. Authors suggested the special method of analysis of certain exhaust exergy components, which allows analyzing possible ways of its secondary use. The obtained equations determine quantitative and qualitative ratios between exhaust exergy components in comparison to maximal exhaust exergy potential to be utilized.
 CONCLUSIONS: Based on experimental data analysis and its statistical processing, it follows that middle powered engines have limited resources of waste heat. Theoretically, it should be enough for ensuring the turbocharger operation and sustaining of thermal condition in a gearbox and a cooling system in winter.

THE METHOD OF THERMAL ENERGY RECOVERY OF EXHAUST GASES OF INTERNAL COMBUSTION ENGINE

In modern internal combustion engines, the part of the fuel energy that is consumed for useful energy is on average 35 percent. Up to 30 percent is spent during the combustion of fuel, which is removed with the exhaust gases of the engine. There are many ways to increase the efficiency of an internal combustion engine, one of which is a way to increase the efficiency by recuperating heat losses, implying the use of a device for converting thermal energy into electrical energy, operating on the Seebeck effect. (Research purpose) The research purpose is developing an experimental installation for the recovery of thermal energy from exhaust gases of an internal combustion engine into electrical energy and deducing the regularities of the thermoelectric generator in the power supply system in automotive equipment. (Materials and methods) Applied methods of numerical analysis and computer modeling using computer programs ANSYS Thermal Steady State and Solidworks FlowSimulation. A laboratory stand operating from the D-65 engine was used as a power plant (Results and discussion) The dependencies of the generated voltage and current of the thermoelectric generator on the temperature of the exhaust gases and coolant of the internal combustion engine were obtained. The maximum generated power of the developed thermoelectric generator was 54.5 watts. The maximum current of the thermoelectric generator during operation of the experimental installation was 3.7 amperes with an output voltage of 22 volts. (Conclusions) The use of the developed thermoelectric generator for the recovery of the energy of the exhaust gases of the internal combustion engine makes it possible to increase the use of the heat released during the combustion of fuel and provides an additional source of electrical energy.

ANALYSIS OF IN-CYLINDER FLOW FIELDS USING PROPER ORTHOGONAL DECOMPOSITION-BASED QUADRUPLE DECOMPOSITION

In order to meet increasingly stringent emission norms coupled with a heightened requirement of performance, there has been an unabated effort toward improvement in the combustion process of modern internal combustion engines. One of the major impediments of enhanced combustion in spark-ignited port fueled engines are combustion variations. These variations are especially dominant at low-load, low-speed operations. Cycle-to-cycle variation (CCV) in in-cylinder flow fields is one of the major contributors of such combustion variations. Therefore, in this work, CCV of in-cylinder flow fields of an optical port fuel injection engine was analyzed at part load (50% throttle opening) and low speed (1200 rpm) with the help of proper orthogonal decomposition. Flow fields were subsequently decomposed into four components, namely, mean, coherent, transition, and turbulent parts. CCV of flow fields was studied using several metrics based on kinetic energy and the relevance index. It was found that the share of mean energy is a better metric for CCV quantification based on kinetic energy. Interestingly, it was observed that the mean part, though consistent in its flow structure for various cycles, has a lot of variation in kinetic energy at early compression stroke. Also, a weak mean flow coupled with a strong coherent flow structure opposing the mean flow produces the largest deviation in a flow field from its corresponding ensemble-averaged field. Furthermore, even though the coherent and transition parts are comprised of comparable energy, it was the coherent part that showed large variations in kinetic energy. Hence, the mean and coherent parts are mainly responsible for CCV in flow fields.

Experimental investigation on the vibrational and fluid dynamics behaviour of a turbocharger compressor in the transition to surge operation

High-speed dynamic centrifugal compressors are widely used both in the modern internal combustion engine design and in advanced pressurized cycles and innovative plant layouts as fuel cell systems. Surge strongly limits the stable operating region of centrifugal compressors in low mass flow rate conditions especially during fast transients. Therefore, it is of great importance to investigate transient system dynamic response of compressor surge evolution and early detection of incipient compressor surge. A specific experimental investigation on compressor surge was carried out at the University of Genoa turbocharger test facility and results are presented and analysed in this paper. The activity consists of steady state and transient measurements used to characterize and identify compressor behaviour in correspondence of surge inception conditions. The frequency and time frequency data analysis have been applied on inflow pressure, anemometric and vibrational signals to identify their contents and so to be able to classify compressor operation as stable or unstable. Synchronous averages performed in the time domain have been identified as a suitable algorithmic tool to detect incipient surge conditions. Anemometric signal analysis allowed to identify intermitting phenomena in deep surge conditions may be related to the rise of a rotation stall condition. The obtained results provide original diagnostic and predictive methods to be integrated in a monitoring system capable of preventing surge and extending compressor operating range, performance and reliability to allow the integration with the other plant components.

Effectiveness of Butanol and Deposit Control Additive in Fuel to Reduce Deposits of Gasoline Direct Injection Engine Injectors

Modern internal combustion engines are designed to meet new emission standards and reduce fuel consumption. The wide application of direct fuel injection is associated with the problem of injector contamination. It leads to a deterioration of the engine’s environmental performance. The paper aims to evaluate the effect of applying gasoline–butanol blends and appropriate additives on the formation of injector deposits. The research involved testing the engine on a dynamometer, evaluating the injector tips visually at 1000× magnification, and registering the fuel spray using high-speed imaging techniques with a laser and halogen lighting source. The effect of engine operating with the reference fuel was to coke the injector tip with a linear pattern. It increased the linear injection time to keep the engine’s operating point constant over the 48 h test. The application of 20% (v/v) butanol reduced deposit formation. The best scavenging results were obtained by extending the engine operating time by the next 24 h and using a cleaning procedure. The procedure included a cleaning additive in addition to butanol. Among the cases analyzed, a combination of butanol and DCA (Deposit Control Additive) was the best method for injector patency restoration.

A negative emission internal combustion engine vehicle?

Modern internal combustion engine vehicles carry extensive exhaust aftertreatment systems that have the potential to reduce their tailpipe pollutant emissions to near-zero, or even within the zero levels of measurement equipment in real-world conditions. It has been reported, therefore, that such vehicles have the potential to have tailpipe pollutant levels lower than the air intake of the vehicle – that they are cleaning the ambient air. This study investigates this hypothesis using a range of internal combustion engines and real-world emissions data alongside pollutant (in this case nitrogen dioxide and particulate matter) data from around the world and the accuracy of the instrumentation typically used to measure tailpipe emissions. The results show that it is unlikely that a modern internal combustion engine vehicle will clean ambient air, even at extreme pollution levels, although it is possible. However, where a vehicle inlet is in the plume of a dirtier vehicle or the pollution measured is among the highest values recorded globally, the pollution reduction can be substantial.

Modeling the non-Arrhenius ignition behavior of 2‐butanol: A detailed theoretical and experimental study

2-butanol is a promising alternative to fossil fuels for which production pathways are already established and which was proven to be suitable for usage within modern internal combustion engines. It is a potential octane booster for gasoline fuels, can be used in diesel engines to reduce soot production, and is applicable as a stand-alone fuel. In the present study, the previously not discussed non-Arrhenius ignition behavior of 2-butanol was revealed by recalculating and adjusting the thermodynamic properties of the fuel and its most important radicals. All relevant fuel consumption reaction rate coefficients were replaced by a consistent set of analogies without any further modifications of the rate parameters. The existing spectrum of validation targets for 2-butanol was extended by new high-pressure Rapid Compression Machine (RCM) experiments for end-of-compression pressures of peoc = 20, 30, 40, and 50 bar with high resolution of temperature to highlight the non-Arrhenius ignition behavior and to study the model performance in more detail. The kinetic model proposed in the present study can reproduce the observed non-Arrhenius behavior within the RCM regime. Kinetic analysis demonstrated that simulated Ignition Delay Times (IDTs) are very sensitive to the equilibria of the R. + O2 reactions for all 2-hydroxybutyl radicals. With the newly determined thermodynamic properties, the equilibria of the R. + O2 reactions are moved towards lower temperatures, enabling low-temperature chain branching. The shift of the equilibrium from the RO.2 side to R. + O2 within the temperature regime covered by the RCM experiments could be identified as the main reason for the observed non-Arrhenius behavior.