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Ammonia is one of the most promising zero carbon fuels for meeting carbon neutrality targets and zero carbon emissions. Ammonia has gained a lot of research interest recently as a hydrogen energy carrier, and direct use of ammonia as a fuel in engines will aid the transformation toward sustainable energy future. In this work, the effect of ammonia shares on combustion and performance characteristics of methane-fueled SI engine is evaluated by increasing the ammonia share by small fractions (0 to 30% by volume) in the fuel mixture (CH4/NH3 blend). Experiments were performed at constant engine load of 8 Nm (BMEP of 1.52 bar), while maintaining constant engine speed (1500 rpm), stoichiometric operation (λ = 1), and optimum spark advance for MBT conditions.

The present research explores the application of biodiesel fuel in a stationary agricultural engine operated under the Homogenous charge compression ignition (HCCI) mode. To achieve HCCI combustion, a fuel vaporizer and a high-pressure port fuel injection system are employed to facilitate rapid evaporation of the biodiesel fuel. The low volatility of biodiesel is one of the significant shortcomings, which makes it inevitable to use a fuel vaporizer at 380oC. Consequently, the charge temperature is high enough to promote advanced auto-ignition. Further, the high reactivity of biodiesel favors early auto-ignition of the charge. Besides, biodiesel exhibits a faster burn rate due to its oxygenated nature. The combined effect of advanced auto-ignition and faster burn rate resulted in a steep rise in the in-cylinder pressures, leading to abnormal combustion above 20% load. Diluting the charge reduces reactivity and intake oxygen concentration, facilitating load extension.

Mass-production single-cylinder engines are generally not turbocharged due to pulsated exhaust flow. Hence, about one-third of the fuel chemical energy is wasted in the engine exhaust. To extract the exhaust energy and boost the single-cylinder engines, a novel supercharging with a turbo-compounding strategy is proposed in the present work, wherein an impulse turbine extracts energy from the pulsated exhaust gas flow. Employing an impulse turbine for a vehicular application, especially on a single-cylinder engine, has never been commercially attempted. Hence, the design of the impulse turbine assumes higher importance. A nozzle, designed as a stator part of the impulse turbine and placed at the exhaust port to accelerate the flow velocity, was included as part of the layout in the present work. The layout was analyzed using the commercial software AVL BOOST. Different nozzle exit diameters were considered to analyze their effect on the exhaust back pressure and engine performance.

Single-cylinder engines in mass production are generally not turbocharged due to the pulsated and intermittent exhaust gas flow into the turbocharger and the phase lag between the intake and exhaust stroke. The present work proposes a novel approach of decoupling the turbine and the compressor and coupling them separately to the engine to address these limitations. An impulse turbine is chosen for this application to extract energy during the pulsated exhaust flow. Commercially available AVL BOOST software was used to estimate the overall engine performance improvement of the proposed novel approach compared to the base naturally aspirated (NA) engine. Two different impulse turbine layouts were analyzed, one without an exhaust plenum and the second layout having an exhaust plenum before the power turbine. The merits and limitations of both layouts are compared in the present study.

Supercharging a single-cylinder diesel engine has proved to be a viable methodology to reduce engine-out emissions and increase full-load torque and power. The increased air availability of the supercharger (SC) system helps to inject more fuel quantity that can improve the engine's full-load brake mean effective pressure (BMEP) without elevating soot emissions. However, the increased inlet temperature of the boosted air and the availability of excess oxygen can pose significant challenges to contain oxides of nitrogen (NOx) emissions. Hence, it is important to investigate the potential NOx reduction options in supercharged diesel engines. In the present work, the potential of low-pressure exhaust gas recirculation (LP EGR) was evaluated in a single-cylinder supercharged diesel engine for its benefits in NOx emission reduction and impact on other criteria emissions and brake specific fuel consumption (BSFC).

Despite the advantages of turbocharging in improved engine performance and reduced exhaust emissions, commercial single-cylinder engines used for automotive applications remain naturally aspirated (NA) and are not generally turbocharged. This is due to the shortcomings with pulsated and intermittent exhaust gas flow into the turbine and the phase lag between the intake and exhaust stroke. In the present study, experimental investigations are initially carried out with a suitable turbocharger closely coupled to a single-cylinder diesel engine. Results indicated that the engine power dropped significantly by 40% for the turbocharged engine compared to the NA version even though the air mass flow rate was increased by at least 1.5 times with turbocharging. A novel approach of decoupling the turbine and the compressor and coupling them separately to the engine is proposed to address these limitations.

In-cylinder emission control methods for simultaneous reduction of oxides of nitrogen (NOx) and particulate matter (PM) are gaining attention due to stringent emission targets and the higher cost of after-treatment systems. In addition, there is a renewed interest in using carbon-neutral biodiesel due to global warming concerns with fossil diesel. The bi-directional NOx-PM trade-off is reduced to a unidirectional higher NOx emission problem with biodiesel. The effect of water injection with biodiesel with low water quantities is relatively unexplored and is attempted in this investigation to mitigate higher NOx emissions. The water concentrations are maintained at 3, 6, and 9% relative to fuel mass by varying the pulse width of a low-pressure port fuel injector. Considering the corrosive effects of water at higher concentrations, they are maintained below 10% in the present work.

Achieving stable combustion without misfire and knocking is challenging in premixed charge compression ignition (PCCI) especially in small bore, air cooled diesel engines owing to lower power output and inefficient cooling system. In the present study, a single cylinder, air cooled diesel engine used for agricultural water pumping applications is modified to run in PCCI mode by replacing an existing mechanical fuel injection system with a flexible common rail direct injection system. An advanced start of fuel injection (SOI) and exhaust gas recirculation (EGR) are required to achieve PCCI in the test engine. Parametric investigations on SOI, EGR and fuel injection pressure are carried out to identify optimum parameters for achieving maximum brake thermal efficiency. An SOI sweep of 12 to 50 deg. CA bTDC is done and for each SOI, EGR is varied from 0 to 50% to identify maximum efficiency points. It was found that EGR helps in extending the load range from 20 to 40% of rated load.

Simultaneous reduction of oxides of nitrogen (NOx) and smoke emissions from diesel engines has always been a challenging task. In this research work, a relative comparison of diesel-water emulsion and water vapor induction methods has been made to examine NOx and smoke emissions reduction potential of a light-duty diesel engine. The water concentration was maintained at 6% of the total fuel in the emulsion and 6% of the total incoming air mass in the fumigation method. A stable diesel-water emulsion is prepared using commercially available surfactants, Span 80 and Tween 80 at 10% concentration. The stability of the emulsion was examined by visual inspection. The droplet size was quantified using dynamic light scattering technique and the emulsion was deemed stable for approximately 105 days on storage at room temperature. To generate water vapor in the intake manifold, 20 ultrasonic atomizers are utilized.

The distribution of fuel-air mixture inside the engine cylinder strongly influences the combustion process. Planar laser-induced fluorescence (PLIF) is commonly used for fuel distribution measurement, however, it is mostly reported on moderate- to large-sized engines. In the present work, PLIF is applied to measure the fuel distribution inside the cylinder of a small, four-stroke, port-fuel-injection (PFI), spark-ignition engine with displacement volume of 110 cm3. Iso-octane was used as the base fuel, and 3-pentanone (15% by volume) was added as a fluorescent tracer in the base fuel. The effect of equivalence ratio, considering ϕ = 1.2, 1.0, and 0.8, on in-cylinder fuel distribution was studied with low throttle opening of 25% at 1200 rpm. PLIF images were recorded at different crank angle degrees during both intake and compression strokes over a swirl measurement plane located at the TDC position.

Preparation of air-fuel mixture and its stratification, plays the key role to determine the combustion and emission characteristics in a gasoline direct injection (GDI) engine working in stratified conditions. The mixture stratification is mainly influenced by the in-cylinder flow structure, which mainly relies upon engine geometry i.e. cylinder head, intake port configuration, piston profile etc. Hence in the present analysis, authors have attempted to comprehend the effect of cylinder head geometry on the mixture stratification, combustion and emission characteristics of a GDI engine. The computational fluid dynamics (CFD) analysis is carried out on a single-cylinder, naturally-aspirated four-stroke GDI engine having a pentroof shaped cylinder head. The analysis is carried out at four pentroof angles (PA) viz., 80 (base case), 140, 200 and 250 with the axis of the cylinder.

Nowadays, due to stringent emission regulations, it is imperative to incorporate modeling efforts with experiments. This paper presents the development of a phenomenological model to investigate the effects of various in-cylinder strategies on combustion and emission characteristics of a common-rail direct-injection (CRDI) diesel engine. Experiments were conducted on a single-cylinder, supercharged engine with displacement volume of 0.55 l at different operating conditions with various combinations of injection pressure, number of injections involving single injection and multiple injections with two injection pulses, and EGR. Data obtained from experiments was also used for model validation. The model incorporated detailed phenomenological aspects of spray growth, air entrainment, droplet evaporation, wall impingement, ignition delay, premixed and mixing-controlled combustion rates, and emissions of nitrogen oxides (NOx) and diesel soot.

Mixture distribution in the combustion chamber of gasoline direct injection (GDI) engines significantly affects combustion, performance and emission characteristics. The mixture distribution in the engine cylinder, in turn, depends on many parameters viz., fuel injector hole diameter and orientation, fuel injection pressure, the start of fuel injection, in-cylinder fluid dynamics etc. In these engines, the mixture distribution is broadly classified as homogeneous and stratified. However, with currently available engine parameters, it is difficult to objectively classify the type of mixture distribution. In this study, an attempt is made to objectively classify the mixture distribution in GDI engines using a parameter called the “stratification index”. The analysis is carried out on a four-stroke wall-guided GDI engine using computational fluid dynamics (CFD).

Today, GDI engines are becoming very popular because of better fuel economy and low exhaust emissions. The gain in fuel economy in these engines is realized only in the stratified mode of operation. In wall-guided GDI engines, the mixture stratification is realized by properly shaping the combustion chamber. However, the level of mixture stratification varies significantly with engine operating conditions. In this study, an attempt has been made to understand the effect of engine operating parameters viz., compression ratio, engine speed and inlet air pressure on the level of mixture stratification in a four-stroke wall-guided GDI engine using CFD analysis. Three compression ratios of 10.5, 11.5 and 12.5, three engine speeds of 2000, 3000 and 4000 rev/min., and three inlet air pressures of 1, 1.2 and 1.4 bar are considered for the analysis. The CONVERGE software is used to perform the CFD analysis. Simulation is done for one full cycle of the engine.

This paper deals with a numerical investigation on swirl generation by a helical intake port and its effects on in-cylinder flow characteristics with axisymmetric piston bowls in a small four-valve direct injection diesel engine. The novelty of this study is in determining the appropriate design and orientation of the helical port to generate high swirl. A commercial CFD software STAR-CD is used to perform the detailed three dimensional simulations. Preliminary studies were carried out at steady state conditions with the helical port which demonstrated a good swirl potential and the CFD predictions were found to have reasonably good agreement with the experimental data taken from literature. For transient cold flow simulations, the STAR-CD code was validated with Laser Doppler Velocimetry (LDV) experimental velocity components’ measurements available in literature.

Owing to a high power-to-weight ratio, mini internal combustion engine is used in propelling an unmanned air vehicle. In comparison to the performance characteristics, the investigations on the combustion aspects of mini engines are scanty. This investigation concerns study of the combustion process of a mini engine and its variability. For this purpose, the experimental cylinder pressure histories were obtained on a laboratory set-up of a 7.45 cm3 capacity mini engine. The analyses of experimental data at different throttle settings reveal that there existed a varied range of rich and lean misfiring limits around a reference equivalence ratio that corresponds to the respective maximum indicated mean effective pressure. At the limiting equivalence ratios, cylinder pressure measurements showed a high degree of cycle-to-cycle variations. In some cases, a slow combustion or misfiring event preceded a rapid combustion.

Air motion inside the engine cylinder plays a predominant role on combustion and emission processes. An attempt has been made in this investigation to simulate the in-cylinder air motion in a DI diesel engine with four different piston configurations such as dome piston, bowl on dome and pentroof piston and pentroof offset bowl piston. For computational analysis, the commercial general purpose code STAR-CD Es-ice has been used, which works on the method of finite volume. To validate the simulation, qualitative and quantitative comparisons have been done with the PIV results available in the literature. From this study, the best possible piston configuration has been arrived at.

Nowadays, Direct Injection Spark Ignition (DISI) engines are very popular because of their lower fuel consumption and exhaust emissions due to lean stratified mixture operation at most of load conditions. In these engines, achieving mixture stratification plays an important role on performance and emission characteristics of the engine. Also, mixture stratification is mainly dependent on in-cylinder flows and air-fuel interaction, which in turn largely dependent on valve configurations. Therefore, understanding them is very much essential in order to improve the engine performance. In this study, a CFD analysis has been carried out on two- and four-valve four-stroke engines to analyze in-cylinder flows and air-fuel interaction at different conditions. The engines specifications considered here are taken from the literature for which experimental data is available. ‘STAR-CD’ software has been used for the CFD analysis. For meshing, polyhedral trimmed cells have been adopted.

Direct injection diesel engines are used in both light duty and heavy duty vehicles because of higher thermal efficiency compared to SI engines. However, due to only short time available for fuel-air mixing, combustion process depends on proper mixing. As a result, DI Diesel engine emits more NOx and soot into the atmosphere. Therefore, to achieve better combustion with less emission and also to accelerate the fuel-air mixing to improve the combustion, appropriate design of combustion chamber is crucial. Hence, in this work a study has been carried out using CFD to evaluate the effect of combustion chamber configuration on Diesel combustion with two different piston bowls. The two different piston configurations considered in this study are centre bowl on flat piston and pentroof offset bowl piston.

This paper deals with in-cylinder flow field analysis in a motored two-stroke engine by CFD technique using STAR-CD. The main aim of this study is to find out the best turbulence model which predicts the fluid flow field inside the cylinder of a two-stroke engine. In this study, a single-cylinder, two-stroke engine which is very commonly used for two-wheeler application in India is considered. Entire analysis is done at an engine speed of 1500 rev/min. under motoring conditions. Here, three commonly used turbulence models viz. standard k-ε, Chen k-ε and RNG k-ε are considered. In addition, experiments were also conducted on the above engine at the motoring conditions to measure velocity vectors of in-cylinder flow fields using particle image velocimetry (PIV). The results of PIV were also used for validating the CFD predictions.