Application of Computational Fluid Dynamics (CFD) in Teaching Internal Combustion Engines

The future of automobile internal combustion (IC) engine facing twin challenges due to emission norms and improving engine performance. Hence it is very important to identify some technique to reduce the emission level and also to improve the engine performance. Catalytic coating is one of the most suitable techniques for reduction of pollution level and increase the engine efficiency. In this paper, the investigations carried out in the single cylinder catalytic coated four stroke spark ignition (SI) engine is discussed in detail. The engine combustion chamber and piston crown were coated by copper (catalyst). The performance of catalytic coated engine various parameters such as torque, brake power at different engine speed conditions measured by using two wheeler chassis dynamometer. In this investigation the comparative study also were carried out for copper coated engine with conventional (Un-coated) SI engine and the results showed that copper coated engine has significant reduction of the carbon monoxide (CO), Hydrocarbon (HC), and Carbon dioxide (CO2) level compare to conventional engine (uncoated) emission levels.The future of automobile internal combustion (IC) engine facing twin challenges due to emission norms and improving engine performance. Hence it is very important to identify some technique to reduce the emission level and also to improve the engine performance. Catalytic coating is one of the most suitable techniques for reduction of pollution level and increase the engine efficiency. In this paper, the investigations carried out in the single cylinder catalytic coated four stroke spark ignition (SI) engine is discussed in detail. The engine combustion chamber and piston crown were coated by copper (catalyst). The performance of catalytic coated engine various parameters such as torque, brake power at different engine speed conditions measured by using two wheeler chassis dynamometer. In this investigation the comparative study also were carried out for copper coated engine with conventional (Un-coated) SI engine and the results showed that copper coated engine has significant reduction of the carbon mon...

Most of us are not familiar with the concept that an internal combustion (IC) engine is working on a four-stroke six-event principle. The six events are suction, compression, combustion, expansion, blow-down and exhaust. However, the expansion and blow-down happen in the power stroke and they can be clubbed together. Therefore, we can say that an engine, whether diesel or gasoline, is working on four-stroke five-event principle. The purpose of this chapter is to make the reader to familiarize with the complexities involved in the working of a four-stroke engine. The five events which are completed in four strokes are: suction, compression, combustion, expansion and exhaust. Application of computational fluid dynamics (CFD) principles for each process mentioned above is a challenging job. The difficulty in understanding the working of an IC engine is due to the fact that we cannot see what is happening inside the cylinder piston arrangement. All that is described in textbooks is based on our knowledge gained over a period of time by conducting experiments. There is no doubt in saying that “seeing is believing”. As it is next to impossible to have a complete experimental flow visualization, nowadays CFD comes in handy to have theoretical flow visualization. Well-developed software is available for the simulation in 3D geometries. In this chapter, we explain step-by-step the details required for the CFD simulation of various processes in an IC engine. Extensive results obtained over a period of 20 years of research by the application of CFD in analysing the flow in engines are comprehensively presented and discussed. CFD can be very well applied for analysing any particular process. It can also be used for the modification of the existing engine design or can also be employed for a new design of an engine. It is hoped that readers may be benefitted in understanding the application of CFD for fluid flow analysis and engine design by reading this chapter. Therefore, the main aim of this chapter is to make the reader appreciate how exactly CFD can be applied for design of an engine. As it is application oriented, we are not going deep into the equations, modelling, etc. A number of case studies are presented and discussed.

For past decades, substantial developments have been accomplished in internal combustion (IC) engine technology, but there still remain some possible improvements. The combustion in an IC engine is a highly intricate phenomenon, thus, numerous factors correlated with different forms of loss decides the efficiency of an engine. In spark-ignition (SI) engines, the combustion duration is considered important because it plays a key role in determining the combustion phasing for best possible energy conversion. The geometry of engine components may directly change the burning rate of air-fuel mixture, therefore, it should also be considered as significant as other aspects like exhaust gas recirculation (EGR) rate or boosting in investigation of the engine performance. This is the reason the development engineers are putting their effort to design an engine with optimized flow motion. Tweaking the flow dynamics via design modification or use of auxiliary device influences the turbulence level inside the combustion chamber, thus, the burning rate as well. Intake port orientation, masking, and piston shape are one of the typical design parameters manipulated for such purpose, and profound understanding on the effect of these design parameters on burning rate is encouraged in order to assist the optimization process. The design optimization process should be based on a fundamental understanding of how the design parameters affect the flow motion and combustion characteristics. This study aims for a simpler and faster method to investigate the consequences of design modifications. As a base model, a physics-based quasi-dimensional (QD) engine model is developed for simulation of SI combustion phenomenon. It is modeled to consider the change in flow motion and turbulence properties via simplified modeling. The advantages of such QD model is that it requires much less computational resource compared to 3D CFD model, and allows a greater degree of freedom within the simulation process which facilitates parametric studies. A zero-dimensional (0D) turbulence submodel is used to describe energy cascade mechanism, and turbulence intensity is calculated reflecting the effect cause by design modification. According to the sensitivities drawn from parametric study, the results of each effect on burning rate and other engine performance properties are compared individually and collectively. A qualitative analysis suggests how sensitive each effect are at given operating conditions. The result infers that the flow concentration by port design modification boosts the burning rate, but it is advantageous in terms of fuel economy to enhance the breathing ability by valve masking. The product of this comparative study assists an intuitive understanding on how the design modification would affect the engine operations, and it is encouraged to develop the model further via validation with experiment data to provide more reliable output. It is believed that it can be utilized as a good reference in engine design process.

<div class="htmlview paragraph">The process of autoignition in an internal combustion engine cylinder produces large amplitude high frequency gas pressure waves accompanied by significant increases in gas temperature and velocity, and as a consequence large convective heat fluxes to piston and cylinder surfaces. Extended exposure of these surfaces to autoignition, results in their damage through thermal fatigue, particularly in regions where small clearances between the piston and cylinder or cylinder head, lie in the path of the oscillatory gas pressure waves.</div> <div class="htmlview paragraph">The ability to predict spatial and temporal' variations in cylinder gas pressure, temperature and velocity during autoignition and hence obtain reasonable estimates of surface heat flux, makes it possible to assess levels of surface fatigue at critical zones of the piston and cylinder head, and hence improve their tolerance to autoignition.</div> <div class="htmlview paragraph">In this paper Computational Fluid Dynamics (CFD) has been used to study conditions of severe autoignition in a spark ignition engine, particularly in regions where piston to cylinder or cylinder head clearances are small. It is shown that very high pressures are generated in regions of small clearance as supersonic pressure waves are decelerated as they enter these spaces.</div>

In the last couple of decades, blending of oxygenated additives with gasoline has been advocated to reduce dependence on fossil fuels and to reduce hazardous health effects of gaseous emissions and particulate matter (PM) emitted by internal combustion (IC) engines in the transport sector worldwide. The primary objective of this research was to carry out a comparative analysis of exhaust PM emitted by gasohol (gasoline blended with 10% ethanol, v/v)-fulled spark ignition (SI) engine with that of baseline gasoline-fuelled SI engine. To assess the PM toxicity, physical, chemical and biological characterizations of PM were carried out using the state-of-the-art instruments and techniques. Measurements of regulated and unregulated gaseous species were also carried out at part/full loads. The results showed that the gasohol-fuelled engine emitted relatively lower concentrations of unregulated gaseous species such as sulfur dioxide (SO2), isocyanic acid (HNCO), etc. Physical characterization of exhaust particles revealed that the gasohol-fuelled engine emitted a significantly lower number of particles compared to the gasoline-fuelled engine. The presence of harmful polycyclic aromatic hydrocarbons (PAHs) and higher trace metal concentrations in PM emitted from the gasoline-fuelled engine was another important finding of this study. Biological characterizations showed that PM emitted from the gasohol-fuelled engine were less cytotoxic and had lower reactive oxygen species (ROS) generation potential. Mutagenicity of PM emitted from the gasohol-fuelled engine was also lower compared to that from the gasoline-fuelled engine. Overall, this study demonstrated that utilization of gasohol in SI engines led to the reduction in emissions, and lowering of PM toxicity, in addition to partial replacement of fossil fuels with renewable fuels.

Air-fuel ratio control is a challenging control problem for port fuel injected and throttle body fuel injected spark ignition (SI) engines, since the dynamics of air manifold and fuel injection of the SI engines are highly nonlinear and often with unmodeled uncertainties and disturbance. This paper presents nonlinear control approaches for multi-input multi-output engine models, by developing adaptive control and learning control design methods. Theoretical proofs are established which ensure proposed controllers are able to give asymptotical tracking performance. Adaptive control and learning control approaches are capable of dealing with both constant uncertainty and time-varying periodic uncertainty. Simulation results illustrate the efficacy of the proposed controllers.

Objectives: Performance and emissions of internal combustion (spark ignition) engine generator is investigated using the representative biogas composition from an anaerobic co-digestion mixture of various agricultural biomass wastes present in Mindanao, Philippines such as rice hull, coconut shell, cow manure as feedstock. Methods: The gases from the representative biogas composition are then fed to the 30kW engine generator and investigated the power generated, and its exhaust emissions. Findings: Results indicated that the variation of energy generated can be related to the electrical power produced from the engine unit to power the electrical appliances used at the same flow rate and pressure. At 1.4 kW electrical load and heating value of the purified biogas as 50 MJ kg-1, the consumption of biogas was observed to be the same. The engine also showed comparable efficiency ranging from 6.26% to 7.00% at 1.4 kW load. Further, the CO2 emission is observed to be 5.40% and amount of other emission pollutants are extremely few (nearly zero) using the representative biogas fuel in the engine. Thus, biogas fuel can be used directly as fuel in the spark ignition engine. Application: The biogas fuel can be used to other engines, but it requires some minor engine modifications in order to correct the compression ratio, spark ignition timing due to the slower flame speed of biogas fuel. Keywords: Biofuels, Biogas, Biomass, Engine Emissions, Engine Performance

During the last years, the sales of vehicles equipped with Spark-Ignition (SI) engines have increased, to the detriment of those powered by Compression-Ignition (CI) engines. However, SI engines provide lower efficiency than CI engines, due to the low compression ratio and stoichiometric mixture operation. A way to increase the efficiency of SI engines is lean combustion, as it allows to increase the specific heats ratio (γ) and reduces pumping losses at part loads. Nevertheless, the operation with extremely lean mixtures deals with ignition issues, promoting Cycle-to-Cycle Variability (CCV) and increasing the probability of misfire. The prechamber ignition concept, also known as Turbulent Jet Ignition (TJI), is a promising solution for enabling the implementation of lean combustion, without its drawback in SI engines. Such a concept can be implemented according to two approaches: In active TJI, there is an additional fuel supply system inside the prechamber, while in passive TJI there isn’t. Therefore, the main advantage of passive TJI is its simplicity, as the prechamber can be installed into a conventional spark plug body, with obvious benefits in terms of packaging and costs. In this work, the benefits of passive TJI on combustion and performance are assessed by simulation analyses. Particularly, a 1-D engine model was developed to simulate the TJI combustion and was validated versus experimental data. Afterward, a 0-D method was applied to assess the impact of the relative air-fuel ratio on CCV. The analysis was carried out in a high speed and load operating condition, namely 4500 rpm and 13 bar of IMEP, under both stoichiometric and lean mixture. Experimental and numerical results demonstrate the effectiveness of the passive TJI concept in promoting faster and more stable combustion also in lean-burn conditions.

This paper examines emissions of reactive nitrogen compounds in the exhaust gas flux of vehicles featuring spark ignition (SI) engines. A range of technical, legal and environmental aspects are considered. A discussion of the fundamentals of the phenomenona of emission of these compounds is presented, together with a brief summary of the negative environmental impacts of these gases. Selected data obtained during chassis dynamometer testing at BOSMAL are presented, together with certain important observations presented in the technical literature. The reader is directed to recent publications of note for further information on emissions to the less well known reactive nitrogen compounds, namely NH3 and N2O. The orders of magnitude of the various reactive nitrogen compounds found in the exhaust gas emitted from SI engines are briefly considered and commented upon. Data are presented on the impact of different fuel types used in SI engines and the reader is directed to various publications on that subject. Finally, important research directions (both current and future) are identified.

A Scalable Infrastructure for Online Performance Analysis on CFD Application

Illustrative overview of CNG engine performance, emissions behavior, and operation challenges. The graphic highlights key trends identified in the systematic review, including typical 10–20% power and torque losses; reductions in CO, HC, PM, and CO 2 emissions; methane-slip escalation with mileage; and the dual effect of cleaner combustion but accelerated lubricant oxidation. The figure synthesizes evidence from 22 studies to show how engine architecture, retrofit quality, and accumulated mileage shape real-world CNG outcomes • Provides the first systematic, strata-based synthesis of CNG performance, emissions, and durability in aged and retrofitted SI and CI engines. • Demonstrates that performance and emissions outcomes under CNG are governed by engine design, retrofit quality, calibration strategy, and accumulated degradation rather than fuel properties alone. • Shows that retrofitted SI fleet engines commonly experience power loss and methane slip, while optimized dedicated SI engines achieve higher efficiency through compression ratio and combustion phasing control. • Identifies dual-fuel CI engines as offering strong particulate reduction but requiring careful pilot-injection and EGR management to avoid CO and HC drawbacks at low load. • Highlights durability and lubrication trade-offs under CNG, with reduced soot contamination but increased thermo-oxidative oil stress, emphasizing the need for robust maintenance and calibration practices. Compressed natural gas (CNG) offers significant emissions advantages over gasoline and diesel, yet most literature focuses on new or laboratory-optimized engines rather than the aged, retrofitted vehicles common in developing countries. With addition of other studies, the review followed PRISMA 2020 guidelines and a prospectively registered protocol (OSF) − https://osf.io/c8u7f/ . Searches across Scopus, IEEE Xplore, and Google Scholar identified 816 records, of which 26 studies met inclusion criteria. CNG consistently lowered CO, HC, PM, and CO 2 emissions, but retrofitted SI engines experienced 10–20% losses in power and torque due to methane’s low volumetric energy density and age-related declines in efficiency. High-mileage fleets showed methane-slip increases, catalyst deterioration, and lubricant oxidation, whereas optimized or dedicated CNG engines demonstrated improved thermal efficiency and fuel economy. Retrofit quality and calibration accuracy proved decisive in determining real-world outcomes. The findings highlight that CNG’s environmental and efficiency benefits are achievable but depend on proper engine design, maintenance, and regulatory support, especially in regions dominated by older vehicle fleets. This review provides the first systematic synthesis focused on aged, high-mileage, and retrofitted spark ignition (SI) and compression ignition (CI) engines operating on CNG, integrating evidence on performance, emissions, combustion behavior, methane slip, lubricant degradation, and catalyst aging. By comparing retrofitted and dedicated CNG engines against real-world aged engine across diverse regions, it reveals how engine architecture, retrofit quality, and accumulated mileage shape CNG outcomes and identifies the operational challenges and research priorities needed for durable, efficient, and low-emission operation.

<div class="section abstract"><div class="htmlview paragraph">The abatement of carbon dioxide and pollutant emissions on motorbike spark-ignition (SI) engines is a challenging task, considering the small size, the low cost and the high power-to-weight ratio required by the market for such powertrain. In this context, the passive pre-chamber (PPC) technology is an attractive solution. The combustion duration can be reduced by igniting the air-fuel mixture inside a small volume connected to the cylinder, unfolding the way to high engine efficiencies without penalization of the peak performance. Moreover, no injectors are needed inside the PPC, guaranteeing a cheap and fast retrofitting of the existing fleet. In this work, a 3D computational fluid dynamics (CFD) investigation is carried out over an experimental configuration of motorbike SI engine, operated at fixed operating conditions with both traditional and PPC configurations. The employed CFD methodology is based on a unique flamelet-based combustion model, regardless the selected ignition strategy. First, 3D gas exchange simulations were performed to achieve realistic conditions for the power-cycle analysis. A specific care was given to the analysis of the PPC scavenging process, which is crucial for a reliable estimation of the exhaust gases stratification near the ignition position. Then, the combustion process was simulated with both ignition strategies, clarifying in particular the dependency of the hot-gases ejection process from the flow field inside the PPC. Finally, a numerical-experimental comparison was carried out in terms of pressure and heat release trends, demonstrating the reliability of the employed CFD methodology in the design of high-performance SI engines.</div></div>

In this study, the effect of acetylene induction on the performance, emissions, and combustion characteristics of a petrol-acetylene-fuelled spark-ignition engine at 1400 rpm was experimentally investigated. Initially, the optimum flow rate of acetylene was found by analysing the performance and emissions for different flow rates of acetylene i.e. 50, 100, 150, and 200 LPH. It was observed that at 100 LPH flow rate the performance was the best and major emissions were either low or comparable to other cases. After finalising the optimum acetylene flow rate the combustion studies were carried out at this flow rate only. Pressure vs. crank angle plots indicate normal combustion with acetylene with slight abnormality at high loads. When compared with gasoline the peak pressures at different loads were found slightly higher resulting in improved combustion. Thus, it can be concluded that acetylene can be a good gasoline substitute. Abbreviations: aTDC: after top dead centre; BSEC: brake specific energy consumption; bTDC: before top dead centre; BTE: brake thermal efficiency; CI: compress ignition; CNG: compress natural gas; CO: carbon monoxide; CO2: carbon dioxide; CR: compression ratio; DAD: data acquisition device; EGT: exhaust gas temperature (°C); HC: hydrocarbon; IC: internal combustion; LPG: liquefied petroleum gas; LPH: litres per hour; NO x : oxides of nitrogen; rpm: revolution per minute; SI: spark ignition; TDC: top dead centre; VCR: variable compression ratio; WC: water column

This paper gives a discussion on the Computational Fluid Dynamics (CFD) applications in offshore engineering. Accurate hydrodynamic quantities are essential for engineering design. Offshore structures are generally subject to high Reynolds number flows. These high Reynolds number flow conditions (Re > 106 ) are difficult and expensive to achieve in an experimental setup. Therefore, it is attractive to use CFD to provide the essential hydrodynamic quantities for practical design. Verification and validation studies are important for determining the validity of the CFD prediction. A procedure of performing CFD simulation is shown. Different types of turbulence modelling are discussed. Three examples of high Reynolds number CFD simulations, covering flow around offshore structural components and waves past partially-submerged horizontal cylinders, are shown and discussed.

<div class="section abstract"><div class="htmlview paragraph">Abnormal combustion referred to as Low Speed Pre-Ignition (LSPI) may restrict low speed torque improvements in turbocharged Direct Injection (DI) - Spark Ignition (SI) Engines. Recent investigations have reported that the auto-ignition of an engine oil droplet from the piston crevice in the combustion chamber may cause unexpected and random LSPI. This study shows that engine oil formulations have significant effects on LSPI. We found that the spontaneous ignition temperature of engine oil, as determined using High-Pressure Differential Scanning Calorimetry (HP-DSC) correlates with LSPI frequency in a prototype turbocharged DI-SI engine. Based on these findings, we believe that the oxidation reaction of the oil is very important factor to the LSPI. Our test data, using a prototype engine, shows both preventative and contributory effects of base oil and metal-based engine oil additives.</div></div>