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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.

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.

For controlling oxides of nitrogen (NOx) and particular matter (PM) emissions from diesel engines, various fuel and combustion mode modification strategies are investigated in the past. Low temperature combustion (LTC) is an alternative combustion strategy that reduces NOx and PM emissions through premixed lean combustion. Dual fuel reactivity-controlled compression ignition (RCCI) is a promising LTC strategy with better control over the start and end of combustion because of reactivity and equivalence ratio stratification. However, the unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are significantly higher in RCCI, especially at part-load conditions. The present work intends to address this shortcoming by utilizing oxygenated alternative fuels. Considering the limited availability and higher cost, replacing conventional fuels completely with alternative fuels is not feasible.

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.

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.

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.

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.

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).

From the energy security and environment standpoint, the biodiesel fuels derived from vegetable oils or animal fats appear to be promising alternative to fossil diesel. Although the engine experiments prove their viability, the scientific data base for characterizing biodiesel combustion is limited. Detailed studies on the characterization of biodiesel fuels and their effects on fundamental engine processes like droplet evaporation and combustion are essential. The present study evaluates the useful thermo-physical properties and droplet evaporation characteristics of biodiesel fuels. The droplet evaporation measurements are carried out using suspended droplet experiments on five biodiesel fuels of Indian origin viz. jatropha, pongamia (karanja), neem, mahua and palm. The droplet evaporation rates of these fuels are related to properties such as binary diffusivity and molecular weight, which in turn depend on their fatty acid composition.

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.

The dynamic behavior of laminated composite box structure containing piezoelectric actuators and sensors for active vibration control is studied by finite element method. The smart laminated composite box structure is considered as assemblages of four walls made up of orthotropic plate modeled as cantilevered and also both ends clamped configuration with surface bonded piezoelectric (PZT) patches. The study uses commercial finite element package program ANSYS 8.1, in which SOLID46 elements are used for the metal part and SOLID5 elements are used for the piezoelectric part of the structure. The feedback control system used in the present study for the active vibration control is same as Karagulle et al. (2004). The influence of the size, number and placements of piezoelectric actuators on vibration control is discussed in detail. The present solution is found to be in good agreement with FEM and as well as ANSYS values from previous work.

The pressure gain characteristics of jet pipe servovalve is required as an input to the designer for improving performance of the servovalve. An attempt has been made to design the first stage jet pipe servovalve parameters to get maximum pressure recovery. The static recovery pressure in receiving holes is a function of jet pipe nozzle displacement relative to receiver plate. The recovery pressure depends on web thickness, jet pipe nozzle diameter, receivers hole diameter, nozzle offset and nozzle stand-of distance. A detailed static recovery pressure analysis of a two stage, four-way, closed ports electrohydraulic flow control valve considering the effect of web thickness, nozzle diameter, receiver hole diameter and offset parameters are presented in the paper. Also the effect of supply pressure on recovery pressure is presented.

Experimental investigations were carried out to assess the effect of using diethyl ether to improve performance & emissions of a DI diesel engine running on water-diesel emulsion. The water-diesel ratio was 0.4:1 (by weight) and diethyl ether percentages of 5, 10 & 15 by weight were tried. The optimum quantity of diethyl ether was chosen as 10% based on emissions. It was found that diethyl ether, when added to water-diesel emulsion can significantly lower NOx and smoke levels without adverse effect on brake thermal efficiency. High HC & CO levels which are problems with water-diesel emulsions, can be significantly lowered with the addition of diethyl ether particularly at high outputs. Ignition delay and maximum rate of pressure rise at full load are also reduced. Even at part load the addition of the diethyl ether can improve the performance as compared to neat water-diesel emulsion without any adverse effect on NOx emission.

The classical trade-off between NOx and soot emissions from conventional diesel engines has been a limiting factor in meeting ever stringent emission norms. The electronic control of fuel injection in diesel engines emerged as an important strategy for their simultaneous reduction. The high pressure multiple-injection in a common rail direct injection system has been promising in this regard. While, the effects of pilot injection or multiple pulses of CRDI injection schedule on simultaneous reduction of NOx and soot have been widely investigated and reported, the investigations concerning three and more injection pulses have been limited. In this paper, the ability of a predictive model, developed by the authors, in providing optimal multiple-injection schedule is demonstrated through parametric investigations. The effects of pilot and post fuel quantity and dwell between the injection pulses on NOx and soot emissions are discussed.

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.

In this paper, energy absorption behavior of Aluminum Alloy AA 7003 and high strength steel tubes is investigated for automotive crash application both experimentally and numerically. The compression test results are compared with the static analysis results obtained from LS-Dyna Software. Tube thickness is varied in the LS-Dyna Finite Element Simulation Software to understand its effect on energy absorption behavior. The peak loads and energy absorption between experimental results and Numeral simulation are found to be in good agreement. The specific energy absorption between high strength steel and Aluminum Alloy AA 7003 is compared.

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.

Internal combustion engines play a major role in biogas-based stationary power generation applications in rural areas, and serious progress on effective utilization of bio-resources by considering engine stability is not achieved yet. In the present study, combustion characteristics and cycle-to-cycle variations (CCVs) of a spark-ignition (SI) engine fueled with gasoline, biogas, and surrogate of bio-methane are analyzed. A single-cylinder, four-stroke SI engine (with a flexible gaseous fuel system) was operated at a couple of load points (8 Nm and 11.5 Nm) with a rotational speed of 1500 rpm. CCVs are analyzed using a statistical approach considering 1000 consecutive engine cycles for each operating condition. Results at 8 Nm showed relatively higher CCVs of indicated mean effective pressure (IMEP), peak in-cylinder pressure (Pmax), and flame initiation duration (FID) for biogas compared to methane.

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.

Unsaturated methyl esters in biodiesel make it susceptible to oxidation and fuel quality degradation upon long-term storage. It is almost impossible to use biodiesel for commercial applications immediately after production. The lead time between biodiesel production and usage is generally high, causing auto-oxidation and fuel quality degradation. Hence any onsite improvement in fuel quality should be tested with aged biodiesel. To avoid the food versus fuel debate, non-edible oil feedstocks are preferable for producing biodiesel. However, biodiesel from non-edible oil sources has more unsaturated methyl ester constituents. The traditional trade-off between oxides of nitrogen (NOx) and soot emissions in conventional diesel combustion is reduced to a more severe NOx problem with biodiesel. In the present study, NOx mitigation through fuel modifications is studied for oxidized biodiesel produced from a non-edible oil, Karanja.