Bowl Geometry Research Articles

Strategies to improve ammonia combustion in a dual fuel marine engine by using CFD

Maritime transportation is currently responsible for delivering most of the world trade, and it still plays a major role in the global economy and pollutant emissions. Due to their heavy loads and long distances, full electrification is generally assumed as an unsuitable pathway, leaving combustion engines as the dominant technology in the marine sector. For a long time, these engines have benefited from the low costs of heavy oils produced from oil refining, but these fuels present a difficult combustion and are associated with significant pollutant emissions and greenhouse gases. Today, carbon-free fuels such as hydrogen and ammonia are gradually getting a foothold in the shipping market.In the present paper, an investigation on several strategies to improve the oxidation of ammonia is carried out for a dual fuel (DF) medium speed marine engine. A CFD analysis using ANSYS FORTE® code is performed on an improved and more realistic bowl geometry by varying the premixed fuel according to methods validated in previous studies and introducing adequate kinetic mechanisms from the literature. Results show that the sole use of ammonia to replace natural gas, as premixed fuel, leads to incomplete combustion; the increase of diesel fuel can only mitigate this condition, but it cannot be considered as viable solution. Therefore, several blends of ammonia/hydrogen are tested to examine combustion development and pollutant emissions. The addition of hydrogen above 10% to the premixed charge composition demonstrates to promote the oxidation of ammonia and to effectively reduce CO2 emissions of 84% without a dramatic increase in nitrogen oxides. On the contrary, hydrogen percentages lower than 10% feature a worsening of the combustion of the premixed charge. Finally, the use of a fuel containing nitrogen promote a slight formation of NOx emissions.

Experimental investigation of new combustion chamber geometry modification on engine performance, emission and cylinder liner microstructure for a diesel engine

Abstract Emission values have been limited and some levels (Tier, EPA, NRE-v/c standards, etc.) must be compatible with human health and the environment. One of the most effective ways to achieve these levels is effective piston bowl geometry. The aim in designing the new combustion chamber was to provide a multiaxial distribution of the fuel in the bowl. In the study, the new combustion chamber was compared with the standard combustion chamber. Both chambers were fitted to the engine and the performance analysis was tested at different operation conditions. Then, 100-hour tests carried out to evaluate the effect of the piston bowl geometry on the surface of the cylinder liner by analyzing its microstructure. From the obtained results, the new combustion chamber geometry reduced HC, CO and soot emissions while NO emissions slightly increased compared to the standard combustion chamber. It decreased brake specific fuel consumption values by 4%, 5.53%, 7.02%, 6.4%, 5.55% and 5.18% for 1700, 1800, 1900, 2000, 2100 and 2200 rpm, respectively. Torque values increased at all engine speeds. When the cylinder liners were evaluated as a result of long-term endurance, there were clearly fewer abrasive wear lines on the cylinder liners of NCC compared to SCC.

Investigation of lubrication and tribological behaviors in a diesel engine with the new designed flow-guided combustion chamber

Changes to the piston bowl geometry directly affect engine performance, exhaust emissions, combustion characteristics and air/fuel mixture formation. In this study, a new combustion chamber (NCC) geometry for a single cylinder direct injection diesel engine is presented, and experimentally compared with the standard combustion chamber (SCC) geometry. Each combustion chamber was fitted to the engine and performed long-term test for 100 h. The effect of combustion chamber bowl geometry on piston rings and lubricating oil was investigated. Firstly, soot was measured in the engine, and the NCC geometry reduced soot emission by approximately 12.32 % compared to the standard bowl geometry type at part load. With the NCC geometry, homogeneity fresh charge and flame propagation were achieved by providing wall-guided flow. The tribological effect of bowl geometry on the lubricating oil was investigated. In the oil analysis, Al,Ca,Co,Cr,Cu,Fe,Mg,Mn,Mo,Ni and Zn elements were higher in the SCC geometry than in the NCC geometry. Especially at the end of the 100th hour of operation, the presence of elements such as Fe and Al showed an increase in engine wears. The lubricating oil kinematic viscosity for SCC was 111.9 mm2/s at 40 °C and 127.9 mm2/s for NCC. In the new geometry, the flash point temperature of the lubricating oil was measured as 232 °C, while this value in the standard geometry was measured as 222 °C. This showed that the volatility and degree of contamination of the oil was lower with the new geometry. SEM/EDX analysis of the piston rings showed a significant difference between the first and second rings for the two geometries. The wear lines in the standard geometry were found to be deeper and more visible than in the new geometry.

Numerical analysis of various combustion chamber bowl geometries on combustion, performance, and emissions parameters in a diesel engine

In this paper, numerical analysis of a diesel engine with various combustion chamber bowl geometries was investigated. Numerical analyses of asymmetrical bowl forms were carried out using the Ansys Forte software. Analyses were done for three different piston bowl geometries in a single-cylinder, air-cooled diesel engine at 1500 rpm engine speed. Three different bowl geometries were created, the piston-1 model is a commercial one for used engine, in the piston-2 pedestal area is removed from the piston, and in the cylindrical model bowl geometry has more straight borders. The results of the numerical study were confirmed with the results of experiments which is carried out for the piston-1 model. Simulation results showed a good correlation with experimental results. According to the results of the numerical study, the highest in-cylinder temperature was determined as 1213 K for the piston-1 model. In the piston-1 model, the combustion efficiency was improved with the increase of the swirl by the increased combustion temperature. As a result of the analysis, the thermal and combustion efficiencies of the piston-1 model were higher than the other models. The maximum turbulence velocity was observed at -12 CA for three different piston bowl models as 4.1 m/s, 4.06 m/s, and 3.9 m/s for piston-1, piston-2, and cylindrical respectively.

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Computational Fluid Dynamics (CFD) Validation and Investigation the Effect of Piston Bowl Geometries Performance on Port Fuel Injection-Homogeneous Charge Compression Ignition (PFI-HCCI) Engines

Numerical Analysis of the Effects of Fuel Injection Duration and Spray Angle on the Combustion Process in a Compression Ignition Engine

The changes in injection strategies for diesel engines have a major impact on the performance and pollutant emission characteristics of diesel engines. If injection strategies like injection duration, injection timing, injection pressure and spray angle are properly adjusted, combustion can be improved. The engine performance will increase and emissions will decrease with the combustion improvement. In this work, the influences of injection duration and spray angle on the combustion characteristics of single cylinder, natural aspirated, electronically controlled injection, compression ignition engine were investigated. In the first stage of the work, experiments were executed on a single cylinder CI engine using a Cussons P8160 DC dynamometer. After the experiments, the piston bowl geometry of the engine was modeled and numerical simulation studies were achieved at 7 different injection durations and 7 different spray angles using Converge CFD software. As a result of this study, it was observed that there is a good match between experimental and simulation data of heat release rate (HRR) and in-cylinder pressure. In-cylinder pressure decreased with longer injection duration. The highest max. in-cylinder pressure was roughly 101.0 bar at 4°CA injection duration and the lowest max. in-cylinder pressure was roughly 82.0 bar at 10°CA injection duration. When the HRR data were analyzed, it was seen that as the injection duration increased, the amount of heat released by combustion decreased. When examining the results of the spray angle analysis, it was concluded that there were not very large differences in-cylinder pressure and HRR data, and there was a difference of 1.4 bar between the highest and lowest max. in-cylinder pressure values. In addition, the highest in-cylinder pressure of approximately 86.7 bar was obtained at a spray angle of 77°. It was observed that the CA50 value was obtained at angles closer to the top dead center by increasing the spray angle and decreasing the injection duration. Moreover, the longest combustion durations were realized at 60° spray angle and 10°CA injection duration.

Effect of modifying bowl geometry for IC engine fueled with diesel and Biofuels - Review

Bio-fuels are one of the most prominent, emerging, and promising fuels, which are aimed to replace diesel in the next decade. Though bio-fuels may not give the same performance as conventional diesel due to certain issues related to both technical and economic aspects, this fact leads to the need for alterations that are supposed to incorporate either changes in the shape of the combustion chamber or other critical factors that affect the performance of the engine. The shape of the top surface, which is known as the "bowl," in the piston plays a major role, and any slight modification in that shape leads to amplified effects on various combustion, emission, and performance parameters. This article shows the valid reason for accepting bio-fuels as fuel for CI engines by considering outcomes derived from experiments and numerical analysis with changes in the shape of the piston bowl. The results obtained are based on the attainment of various parameters, which leads to higher turbulence velocity distribution, better mixture fraction values, and lower soot formation distribution that can be obtained by modifying the shape of bowl. The pressure, temperature and heat release in the combustion chamber found to be changed due to the modification in bowl geometry.

Numerical study of piston bowl geometries on PFI-HCCI engine performance

Homogeneous charge compression ignition (HCCI) is an advanced combustion strategy proposed to provide higher efficiency and lower emissions than conventional compression ignition. However, there are still tough challenges in the successful operation of HCCI engines. Among these challenges, homogeneous mixture preparation and combustion phase control plays a vital role in determining the efficiency and emissions. Piston bowl geometry significantly enhances the process by improving the flow, turbulence, and mixing for the combustion. The study utilised experimental and numerical simulation methods to analyse HCCI combustion in port fuel injection (PFI) mode and evaluate the effect of piston geometries on engine performance. For this purpose, the different pistons bowl geometries (Baseline model, SQC, and CCC) with the same volume, compression, and equivalence ratio were numerically tested in a four-stroke, single-cylinder, YANMAR diesel engine. The numerical simulation results provide adequate assurance to proceed with the study with different piston geometries design. Compared to SQC and CCC, the Baseline model produced significantly higher cylinder pressure, temperature, and heat release rate. Different piston shape designs influenced the formation of air-fuel mixing, thereby affecting the time and location of onset combustion. The present investigation offered the significant role of piston geometry for the control mechanism of PFI-HCCI combustion, that is a vital part in demonstrating HCCI combustion.

Effect of Split and Re-Entrant Type Piston Bowl Geometry and Preheated Calophyllum Inophyllum Methyl Ester on the Conventional CI Engine Performance

Effect of Split and Re-Entrant Type Piston Bowl Geometry and Preheated Calophyllum Inophyllum Methyl Ester on the Conventional CI Engine Performance

Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations

Catalyst-heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, where retardability is constrained mainly by emissions due to inactivity of the oxidation catalyst at these conditions. Comprehensive understanding of formation mechanism of pollutant emissions is needed to optimize engine performance and minimize tailpipe harmful emissions. In this study, a computational fluid dynamics model of a medium-duty compression-ignition engine is developed and validated against with catalyst-heating operation experimental data using large eddy simulations. The engine is fueled with a full boiling-range diesel fuel and uses an optimized five-injections strategy that consists of two pilots, one main, and two post injections. Results show that, significant amounts of unburned hydrocarbons (UHCs) and oxygenated UHCs (OUHC) are formed by the pilot injections, which may persist until exhaust valve opening. UHCs accumulate mainly in the outer-upper part of the cylinder guided by the piston lip, in the inner-bowl due to the bowl geometry, near the injector nozzle by the fuel from the end-phase of injection, and in the space between spray plumes transported by the swirl motion. The main injection exhibits a short ignition delay and rapidly consumes most of UHC and OUHC, except for the central part of the chamber near the injector nozzle. The 1st post injection counteracts the expansion effect on temperature, plays a key role in increasing the exhaust enthalpy and reducing the harmful emissions by promoting combustion associated with the 2nd post injection. The fuel delivered by the 2nd post injection penetrates through the flame of the 1st post injection, creating cool flame clouds beyond the flame that eventually transition to a diffusion flame. Finally, a unique phenomenological model is proposed to better visualize the interactions of post injections.

Numerical investigation on selecting appropriate piston bowl geometry and compression ratio for gasoline-fuelled homogeneous charge compression ignited light-duty diesel engine

The gasoline-fuelled homogeneous charge compression ignition (HCCI) combustion is a promising approach to mitigate the significant limitations of the traditional compression-ignition combustion for light-duty engine applications. In the present work, the required autoignition quality of gasoline was achieved by blending 2-ethylhexyl nitrate (EHN) with gasoline to ensure combustion stability at the achieved engine loads. A reduced chemical reaction mechanism consisting of 185 species and 219 reactions was developed in the present study for EHN-gasoline-fuelled-HCCI combustion. The mechanism was validated by conducting multi-dimensional computational fluid dynamics (CFD) simulations of HCCI combustion in a modified light-duty diesel engine. A detailed numerical study was done using the validated CFD model to select the suitable piston bowl geometry and geometric compression ratio for better engine performance and lower regulated emissions. Eleven different piston bowl geometries were explored, which also included piston bowl designs popular in traditional compression-ignition (toroid) and spark-ignition (flat) engines. The results indicated that the flat-shaped piston bowl exhibited a 17% improvement in the gross indicated thermal efficiency and a 16% and 40% reduction in UHC and CO emissions while maintaining very low NOx and smoke levels compared to the baseline hemisphere-shaped piston bowl. The engine performance remained the same for the flat-shaped piston bowl geometry even for a 17% increased compression ratio with the added benefit that the reduced EHN concentration (by 48 vol.%) was needed to achieve the same combustion phasing. Thus, the present numerical work proposes a promising approach to improve the overall performance of gasoline-fuelled HCCI combustion by piston bowl design and compression ratio optimization.

Design Optimization of an Ethanol Heavy-Duty Engine Using Design of Experiments and Bayesian Optimization

Abstract Diesel-fueled engines still hold a large market share in the medium and heavy-duty transportation sector. However, the increase in fossil fuel prices and the strict emission regulations are leading engine manufacturers to seek cleaner alternatives without a compromise in performance. Alcohol-based fuels, such as ethanol, offer a promising alternative to diesel fuel in meeting regulatory demands. Ethanol provides cleaner combustion and lower levels of soot due to its chemical properties, in particular its lower level of carbon content. In addition, the stoichiometric operating conditions of alcohol fueled engines enable the mitigation of NOx emissions in aftertreatment stage. With the promise of retrofitting diesel engines to run on ethanol to reduce emissions, the thermal efficiency of these engines remains the primary optimization target. In order to find the optimal ethanol-fueled engine design that maximizes the thermal efficiency, a large design space needs to be investigated using engineering tools. In this study, previous research by the authors on optimizing the design of a single-cylinder ethanol-fueled engine was extended to explore the design space for a heavy-duty multicylinder engine configuration. A heavy-duty engine setup with multiple operating conditions at different engine speeds and loads was considered. A design optimization analysis was performed to identify the potential designs that maximize the indicated thermal efficiency in an ethanol-fueled compression ignition engine. First, a computational fluid dynamics (CFD) model of the engine was validated using experimental data for four drive cycle points. Using a design of experiments (DoE) approach and a parameterized piston bowl geometry, the model was then exercised to explore the relationship among geometric features of the piston bowl and spray targeting angle and indicated thermal efficiency across all tested operating conditions. After evaluating 165 candidate designs, a piston bowl geometry was identified that yielded an increase between 1.3% and 2.2% points in indicated thermal efficiency for all tested conditions, while satisfying the operational design constraints for peak pressure and maximum pressure rise rate. The increased performance was attributed to enhance mixing that led to the formation of a more homogeneous distribution of in-cylinder temperature and equivalence ratio, higher combustion temperatures, and shorter combustion duration. Finally, a Bayesian optimization (BOpt) analysis was employed to find the optimal piston bowl geometry with a fixed spray injector angle for one of the operating conditions. Using BOpt, a piston candidate was identified that resulted in a 1.9% point increase in thermal efficiency from the baseline design, yet only required 65% of the design samples investigated using the DoE approach.

A Synergic Application of High-Oxygenated E-Fuels and New Bowl Designs for Low Soot Emissions: An Optical Analysis

Synthetic fuels significantly reduce pollutant emissions and the carbon footprint of ICE applications. Among these fuels, oxymethylene dimethyl ethers (OMEX) are an excellent candidate to entirely or partially replace conventional fuels in compression ignition (CI) engines due to their attractive properties. The very low soot particle formation tendency allows the decoupling of the soot-NOX trade-off in CI engines. In addition, innovative piston geometries have the potential to reduce soot formation inside the cylinder in the late combustion stage. This work aims to analyze the potential of combining OMEX with an innovative piston geometry to reduce soot formation inside the cylinder. In this way, several blends of OMEX-Diesel were tested using a radial-lips bowl geometry and a conventional reentrant bowl. Tests were conducted in an optically accessible engine under simulated EGR conditions, reducing the in-cylinder oxygen content. For this purpose, 2-colour pyrometry and high-speed excited state hydroxyl chemiluminescence techniques were applied to trace the in-cylinder soot formation and oxidation processes. The results confirm that increasing OMEX in Diesel improves the in-cylinder soot reduction under low oxygen conditions for both piston geometries. Moreover, using radial lips bowl geometry significantly improves the soot reduction, from 17% using neat Diesel to 70% less at the highest OMEX quantity studied in this paper.

Analysis of an innovative combustion chamber with the wall guided fuel injection in a small diesel engine

This paper has included the effects of different bowl geometries which has the wall guided fuel injection. Bowl geometries, which affect in-cylinder air flows, have a great influence on the change of mixture formation. Also, the region where the fuel hits in the bowl affects all engine parameters. In this presented numeric study, the standard combustion chamber geometry of a single-cylinder, air-cooled, and direct-injection diesel engine is compared with the designed new combustion chamber. Four different rotation angles (0°, 7.5°, 10°, and 15°) were determined for the new combustion chamber geometry and compared with the standard geometry. The three-dimensionally modeled bowl geometries in 3D Computational Fluid Dynamics simulation were examined in terms of in-cylinder pressure and temperature, instantaneous and cumulative heat release rate, exhaust emissions (NO, soot, CO, and CO2), temperature/spray, and equivalence ratio/spray at different CA’s. The effects of the different rotation angles of the designed new bowl geometry on both the air movement and the region where the fuel hits were investigated for the engine parameters. When the results obtained are examined, maximum in-cylinder pressures for standard combustion chamber, new combustion chamber 1, new combustion chamber 2, new combustion chamber 3, and new combustion chamber 4 geometries were obtained 79.5, 75.2, 78, 78.1, and 78 bar respectively, and the maximum in-cylinder temperatures were found 1766, 1742, 1805, 1817, and 1818 K, respectively. According to the results obtained from the numerical analysis, CO, CO2, and soot emissions decreased while NO emissions increased in the new combustion chamber, compared to the standard combustion chamber. Examined the spray distributions in bowl, it was seen that the fuel sprays distributed more homogeneously and flame propagates which is spread throughout the chamber in the new combustion chamber type, which improved the mixture formation. The wall guided fuel flow in the novel designed chamber geometries beneficial to turbulence kinetic energy, spray distribution, emissions.

Co-optimization of operating parameters, fuel composition, and piston bowl geometry of gasoline compression ignition (GCI) engine at high loads

Focusing on the gasoline compression ignition (GCI) combustion mode, the operating parameters, fuel composition, and piston bowl geometry were collaboratively optimized at high loads to improve engine performance. A meliorative genetic algorithm coupled with a three-dimensional computational fluid dynamics (CFD) program was adopted as the optimization tool. The optimal GCI combustion strategy is summarized based on the optimization results, and the key parameters affecting engine performance at high loads are further analyzed. The results show that the employment of the open-type piston bowl, high-reactivity fuel, and late start of injection (SOI) is desirable for GCI engines at high loads. Under this strategy, fuel burns in multiple stages, which can reduce the heat release rate and advance the combustion phase. The width of the piston bowl is the geometric parameter with the most notable impact on GCI combustion. Due to the weaker turbulent kinetic energy and the smaller surface area, the larger piston bowl width is conducive to diminishing the heat transfer losses of the engine and promoting the oxidation of unburned hydrocarbon (HC) emissions. Relative to the optimal case, the strategy with the open-type piston bowl, high-reactivity fuel, and early SOI can reduce fuel consumption but results in a higher in-cylinder pressure rise rate and increased ringing intensity (RI). On the contrary, the re-entrant type piston bowl, low-reactivity fuel, and late SOI can significantly reduce the pressure rise rate and RI while deteriorating thermal efficiency.

Effect of piston bowl geometry and spray angle on engine performance and emissions in HCCI engine using multi‐stage injection strategy

AbstractThe homogeneous charge compression ignition (HCCI) and combustion chamber geometry play significant roles in improving the potential of compression ignition engines and their environmental sustainability. However, a major hindrance to the progress of HCCI technology has been the notable decline in brake thermal efficiency and emit high levels of hydrocarbon (HC) and carbon monoxide (CO) which is mainly due to the low temperatures during combustion and low post oxidation of these components. Combustion chambers like hemispherical combustion chamber (TCC) and toroidal combustion chamber (TCC) are known to provide better combustion characteristics due to their increased surface‐to‐volume ratio. Moreover, injection timing and spray position have shown a significant effect on the controlling onset of combustion and emission in HCCI engine. Therefore, the primary objective of this numerical study is to enhance the engine characteristics in HCCI mode using an HCC and TCC piston bowl geometry coupled with multistage injection and compare the results with flat piston bowl geometry. The results show that the toroidal shape piston geometry provides 3%–5% higher brake thermal efficiency compared to the conventional piston geometry. Additionally, the energy balance analysis revealed that the combination of modified piston geometry and multi stage injection improved the combustion process by reducing the energy losses due to incomplete combustion and heat transfer to the engine walls. These findings suggest that the proposed injection strategy combined with modified piston geometry has the potential to enhance the performance of HCCI engines and reduce their environmental impact.

A numerical study of piston bowl geometry and diesel injection timing in a heavy-duty diesel/syngas RCCI engine

The current numerical study aims to examine the single and combined effects of various piston bowl geometries, diesel main Start of Injection (SOI) timing, and syngas energy ratio on the combustion characteristics, specific emissions (g/kW·h), energy distribution, and exergy of a heavy-duty off-road Reactivity-Controlled Compression Ignition (RCCI) diesel engine. The examined geometries include the stock chamber (baseline combustion chamber), wide-shallow chamber, dual-swirl chamber, stepped-lip chamber. The main SOI timing was varied from −20 to −5 Crank Angle (CA) After Top Dead Center (ATDC) with 5 CA steps. Also, syngas energy ratio including 0% Conventional Diesel Combustion (CDC) mode, 20%, 40%, and 60% of total fuel energy per cycle. To accomplish this goal, the SAGE combustion model coupled with a reduced chemical kinetic mechanism consists of 360 reactions, and 72 species was applied to conduct this investigation. The numerical findings showed that the use of the wide-shallow chamber extended the engine operable range under diesel-syngas combustion operating conditions. In comparison to the baseline CDC case, the application of the dual-swirl chamber under CDC conditions, and main SOI timing of −15 CA ATDC led to reduction of Carbon Monoxide ([Formula: see text]), Hydro-Carbon ([Formula: see text]), Particle Matter ([Formula: see text]), Carbon Dioxide ([Formula: see text]), Indicated Specific Energy Consumption (ISEC), Gross Indicated Efficiency (GIE), and exergy efficiency but with a Nitrogen Oxides ([Formula: see text]) penalty rate. In general, an increase in the bore to bowl diameter ratio caused a shorter ignition delay period and combustion duration. The utilization of the stepped-lip chamber at both CDC and diesel-syngas combustion operating modes resulted in a shorter ignition delay period, but a longer combustion duration. Nonetheless, the stepped-lip combustion chamber reduced the diffusive flame temperature. Also, it is noteworthy that the utilization of the stock chamber along with the main SOI timing at −5 CA ATDC under diesel-syngas 60% combustion mode is a suitable technique to pass EURO-VI [Formula: see text] and [Formula: see text] emissions regulations.

Characterisation of emission-performance paradigm of a reactivity-controlled compression ignition engine using artificial intelligent based multi-objective response surface methodology model fuelled with ternary fuel

Petroleum reserves all over the world have been severe to the point of depletion in the previous several decades. Modern transportation and industry employ diesel-fuelled engines because of their higher thermal efficiency. This study investigates the reactivity-controlled compression ignition engine characteristics utilising n-octanol and Moringa oleifera oil blended with diesel. Tests are carried out at maximum load with different bowl geometries to examine the influence of operating parameters, namely injection pressure (500–1000 bar) and static injection timing (23–27°bTDC). Box–Behnken Forecasting input variables like injection pressure and timing with different piston bowls is done using the response surface approach. Maximum brake thermal efficiency and brake power are achieved with this ideal model, and the emission of unburned HC and NO x is decreased. The effects of several variables, including piston bowls, fuel injection timing (FIT) and fuel injection pressure, are examined for an reactivity-controlled compression ignition engine running on Moringa oleifera oil/1-octanol fuel using an L27 orthogonal array. Various models were created and verified using experiment findings as the basis.

Additive manufacturing new piston design and injection strategies for highly efficient and ultra-low emissions combustion in view of 2030 targets

Internal combustion engines have been the most effective solution as the main mover for mobility. Despite the recent European regulations targeting zero tailpipe CO2 emissions for new passenger cars and light vans from 2035 onwards, the upcoming emission regulations still require further technology and fuel developments in the transport sectors. In recent years, studies on internal combustion engines have been increasingly shifting from performance and refinement through advanced fuel injection and air charging technologies to ultra-low emissions and efficiency. Particular attention has also been paid to carbon–neutral fuels. The problem merits further investigation since all are key factors for the powertrain competitiveness in the electrified automotive future, as the pollutants and the CO2 emissions will soon approach the Euro 7 regulation and the Fit to 55 standards, respectively. To this aim, the combustion system design is a crucial part of the internal combustion engine development in the view of exploiting renewable fuel characteristics. This study seeks to assess the effectiveness of a steel piston, realized through a specific design for additive manufacturing technologies, enabling an innovative bowl geometry. It features a highly re-entrant sharp-step and radial lips bowl profile enabling spray separation and radial mixing zone concept. A single-cylinder compression ignition engine has been employed to demonstrate the effectiveness of the innovative bowl shape to meet the challenging future ultra-low emission targets. The results confirm the additive manufacturing technology as a possible solution for innovative highly-stressed steel piston designs. The new bowl shape design, combined with optimised spray targeting and injection strategies, allows outstanding soot reductions, up to 80%, and ultra-low NOx emission levels compared to the conventional combustion system. Gains in fuel economy are also observed. Further emissions advantages are expected with renewable fuel applications.

Combustion Chamber Optimization for Dual-Fuel Biogas–Diesel Co-Combustion in Compression Ignition Engines

Micro-cogeneration with locally produced biogas from waste is a proven technique for supporting the decarbonization process. However, the strongly variable composition of biogas can make its use in internal combustion engines quite challenging. Dual-fuel engines offer advantages over conventional SI and diesel engines, but there are still issues to be addressed, such as the low-load thermodynamic efficiency and nitrogen oxide emissions. In particular, it is highly desirable to reduce NOx directly in the combustion chamber in order to avoid expensive after-treatment systems. This study analyzed the influence of the combustion system, especially the piston bowl geometry and the injector nozzle, on the performance and emissions of a dual-fuel diesel–biogas engine designed for micro-cogeneration (maximum electric power: 50 kW). In detail, four different cylindrical piston bowls characterized by radii of 23, 28, 33 and 38 mm were compared with a conventional omega-shaped diesel bowl. Moreover, the influence of the injector tip position and the jet tilt angle was analyzed over ranges of 2–10 mm and 30–120°, respectively. The goal of the optimization was to find a configuration that was able to reduce the amount of NOx while maintaining high values of brake thermal efficiency at all the engine operating conditions. For this purpose, a 3D-CFD investigation was carried out by means of a customized version of the KIVA-3V code at both full load (BMEP = 8 bar, 3000 rpm, maximum brake power) and partial load (BMEP = 4 bar, 3000 rpm). The novelty of the study consisted of the parametric approach to the problem and the high number of investigated parameters. The results indicated that the standard design of the piston bowl yielded a near-optimal trade-off at full load between the thermodynamic efficiency and pollutant emissions; however, at a lower load, significant advantages could be found by designing a deeper cylindrical bowl with a smaller radius. In particular, a new bowl characterized by a radius of 23 mm was equivalent to the standard one at BMEP = 8 bar, but it yielded a NOx-specific reduction of 38% at BMEP = 4 bar with the same value of BTE.