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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.

The diesel power train (engine and transmission) is the most significant mass contributor in a three- wheeled vehicle. High idling vibrations from the engine get transmitted to the structure and the body panels through the engine mounts. Isolation of these vibrations by proper design of rubber mounts is the most effective engineering approach to improve ride quality of vehicle. In the present study, a mathematical model of the powertrain and mount system is developed; with the engine and transmission being assumed to behave as a rigid body (6 degrees-of-freedom) and the compliance comes from the mounts. As a first step, the modes and natural frequencies are obtained. Following this the response to unbalanced inertial forces for an excitation frequency range of 20-60 Hz (1200-3600 rpm) has been obtained. The model is validated by comparing its results with results of previous published research work.

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.

For more than a decade there is a progressive demand for fuel efficient and high specific power output engines. Optimization of engine cooling and thermal management is one of the important activities in engine design and development. In the present paper an effort has been made to simulate the heat transfer modes of cylinder block and head for a present 4-stroke air-cooled motorcycle engine. Two and three-dimensional decoupled and conjugate heat transfer analysis has been done with commercially available computational fluid dynamics (CFD) codes. Experimental results are also presented. A complete simulation model has been developed and CFD techniques have been applied to design and optimize air cooling surfaces of cylinder head and block, for an air cooled motorcycle engine. The two dimensional analysis is an easy and fast method to predict fin surface temperature, heat transfer co-efficient and flow velocity.

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.

Engine modelling aims at studying the combustion related phenomenon occurring in Internal Combustion (IC) engines. In this regard, a low dimensional mathematical model using first principles has been developed to study Spark Ignited (SI) engines. The resulting equations are Ordinary Differential Equations (ODE) (for volume, pressure, torque, speed and work done) and Partial Differential Equations (PDEs) for temperature and species conservation equations (fuel, CO, CO2, NO). This model utilizes simplified reaction kinetics for the oxidation of fuel in the combustion chamber. A two-step mechanism for the combustion of fuel and the classical Zeldovich Mechanism are used to predict the amount of NO formed during combustion. The model is solved in FORTRAN using LSODE subroutine (for stiff equations) with lumped parameters for thermal properties and diffusion, and invoking the ideal gas assumption.

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.

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.

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.

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.

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.

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 presence of unsaturated methyl esters in biodiesel makes it susceptible to oxidation and fuel quality degradation upon long-term storage. In the present work, the effects of oxidation of Karanja biodiesel upon long-term storage on the combustion and emission characteristics of a heavy-duty truck diesel engine are studied. The Karanja biodiesel is stored for one year in a 200 litres steel barrel at room conditions to mimic commercial storage conditions. The results obtained show that compared to diesel, the start of injection of fresh and aged biodiesels are advanced by ~2-degree crank angle, and the ignition delay time is reduced. Aged biodiesel showed a slightly smaller ignition delay compares to fresh biodiesel. The fuel injection and combustion characteristics of fresh and aged biodiesels were similar at all the load conditions. Both fresh and aged biodiesels produced higher oxides of nitrogen (NOx) and lower smoke emissions compared to diesel.

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.

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).

This paper deals with experimental study of in-cylinder tumble flows in a single-cylinder, four-stroke, two-valve internal combustion engine using a pentroof-offset-bowl piston under non-reacting conditions with four intake manifold orientations at an engine speed of 1000 rev/min., during suction and compression strokes using particle image velocimetry. Two-dimensional in-cylinder tumble flow measurements and analysis are carried out in combustion space on a vertical plane passing through cylinder axis. Ensemble average velocity vectors are used to analyze the tumble flows. Tumble ratio (TR) and average turbulent kinetic energy (TKE) are evaluated and used to characterize the tumble flows. From analysis of results, it is found that at end of compression stroke, 90° intake manifold orientation shows an improvement in TR and TKE compared other intake manifold orientations considered.

Today, gasoline direct injection (GDI) engine is one of the best strategies to meet the requirement of low pollutant emissions and fuel consumption. Generally, the GDI engine operates in stratified mixture mode at part-load conditions and homogeneous mixture mode at full-load conditions. But, at part-loads, soot emissions are found to be high because of improper air-fuel mixing. To overcome the above issue, a homogenous-stratified mixture (a combination of the overall homogeneous lean mixture with a combustible mixture at the location of the spark plug) is found to be better to reduce soot emissions compared to a stratified mixture mode. It will also help reduce fuel consumption. In this study, the analysis has been done to evaluate the effect of homogeneous-stratified mixture combustion on the performance and emission characteristics of a spray-guided GDI engine under various conditions 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.

In this work a novel mixture injection system has been developed and tested on a two stroke scooter engine. This system admits finely atomized gasoline directly into the combustion chamber. It employs many components that were individually developed, fabricated, tested and then coupled together. A small compressor driven by the engine sends pressurized air at the correct crank angle through a timing valve. This is connected to a mechanical injector through a high pressure pipe. Fuel is metered into the high pressure pipe using a standard low pressure injector. The developed mixture injection system resulted in considerable improvements in thermal efficiency and reduction in HC emissions over the manifold injection method at all engine outputs. A considerable reduction in short circuiting losses was seen. The highest brake thermal efficiency achieved was 25.5% as against 23% with the manifold injection system.

In the present work, the possibility of engine knock detection is investigated based on in-cycle speed data, which is readily available to the ECU. Experiments were conducted at 3000 rpm with wide-open throttle condition in a single-cylinder, air-cooled, port-fuel-injection spark-ignition engine at different levels of knocking. It was found that amplitude of speed oscillations increased with the knock intensity for considered window with the size of 100 crank angle degree, starting from the top dead center of compression. The proposed knock indicators based on in-cycle speed oscillations were found to be able to identify the knock-limited spark timings at different operating conditions. Results showed that the amplitude of speed oscillations, derived from in-cycle speed data with resolution of six crank angle degree, could also be used to quantify the knock. The knock frequency based on speed oscillations also showed a sharp increase at the onset of knock.