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Short-circuiting of the fuel air mixture during scavenging is the main reason for high fuel consumption and hydrocarbon (HC) emissions in two-stroke SI engines. Though direct injection of the fuel after the closure of ports has advantages, it is costly and complex. In this work, in a 2S-SI, single cylinder, automotive engine, LPG (liquefied Petroleum Gas) was injected through the boost port to reduce short-circuiting losses. A fuel injector was located on one of the boost ports and the air alone was fed through the other transfer and boost ports for scavenging. Experiments were done at 25% and 70% throttle openings with different injection timings and optimal spark timing at 3000 rpm. Boost port injection (BPI) of LPG reduced HC emissions at all conditions as compared to LPG-MI (Manifold Injection). Particularly significant reductions were seen at high throttle conditions and rich mixtures. HC reductions with BPI were 19% and 25% as compared to LPG-MI and gasoline-MI respectively.

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.

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.

This paper deals mainly with computer simulation of processes of Gasoline Direct Injection (GDI) associated with Extended Expansion Engine (EEE) concept applied to a four-stroke, single-cylinder SI engine. In the case of standard SI engines, part-load brake thermal efficiencies are low due to higher pumping losses. The pumping losses can be reduced by operating the engine always at full throttle as done in extended expansion engine. In extended expansion engine, higher Geometric Expansion Ratio (GER) compared to Effective Compression Ratio (ECR) is responsible for better performance at part loads. Usually, in this engine, by delaying inlet valve closure timing along with reduced clearance volume, extended expansion is achieved. Experimentally many researchers have proved that variable valve timing and variable compression ratio techniques adopted in SI engines, improves the part- load performance greatly.

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.

Oil with high free fatty acid (FFA) content may not be an appropriate contestant for biodiesel production due to poor process yield. The high FFA content (≻1%) will cause soap formation and the separation of products will be exceedingly difficult, and as a result, it has low yield of biodiesel product. In order to increase the process yield, pretreatment setup is required. This involves additional cost and will increase overall fuel price. Hence crude vegetable oils having high FFA can be blended with diesel for effectual employment in diesel engines. In this context, Jatropha Curcas L, non-edible tree-based oil with higher FFA content, can be considered as one of the prominent blending sources for diesel. The primary objective of the present work is to analyze the effect of FFA content of crude Jatropha Curcas L oil (CJO) on performance and emission characteristics of a direct injection (DI) diesel engine.

In this experimental work the effect of double injection of diesel in a biogas-diesel partially premixed charge compression ignition (BDPPCCI) engine was studied. Biogas was inducted along with air while diesel was injected through a common rail system using an open electronic control unit. Experiments were done at a fixed brake mean effective pressure of 2 bar and an intake charge temperature of 40°C. The effect of start of injection (SOI) of first and second injection pulses and also the biogas energy share (BGES) were evaluated. Experiments were also done in the BDPPCCI mode with diesel being injected in a single pulse and in the biogas-diesel dual fuel (BDDF) mode for comparison. The thermal efficiency in the BDPPCCI mode was better with double injection of diesel as compared to single pulse injection due to better combustion phasing. Improved charge homogeneity and reduced wall wetting of diesel lowered the smoke emission levels with split injection.

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.

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.

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.

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.

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 limitations related to the cost-effectiveness and technological feasibility of upgrading biogas to bio-methane for rural power generation applications have prompted researchers to explore alternative approaches for improving the quality of biogas fuel. This study focuses on evaluating the effect of hydrogen enrichment on combustion characteristics and cycle-to-cycle combustion variations in a single-cylinder spark ignition engine fueled with biogas (60% CH4 and 40% CO2). The engine was run at a constant operating load of 6 Nm, with a compression ratio of 10:1 and an engine speed of 1500 rpm. To establish a baseline for comparison, engine characteristics were initially assessed using pure methane fuel. Subsequently, the share of hydrogen in the biogas fuel mixture was incrementally increased on the volumetric basis from 0% to 30% and experiments were performed to study the effects of these variations on combustion behavior.

Currently, alternative fuels produced from waste resources are gaining much attention to replace depleting fossil fuels. The disposal of waste plastic poses severe environmental problems across the globe. The energy embodied in waste plastics can be converted into liquid fuel by pyrolysis. The present work explores the possibility of utilizing waste plastic oil (WPO) produced from municipal plastic wastes and waste cooking oil (WCO) biodiesel produced from used cooking oil in a dual fuel reactivity-controlled compression ignition (RCCI) mode. A single-cylinder light-duty diesel engine used for agricultural water pumping applications is modified to run in RCCI through suitable intake and fuel injection systems modifications. Alternative fuel blends, viz. WPO and WCO biodiesel with 20 vol. % in gasoline and diesel is used as a port and direct-injected fuels in RCCI. The premixed ratio and direct-injected fuel timings are optimized to achieve maximum thermal efficiency.

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.

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.

Gasoline direct injection (GDI) engines are now trending in automobile field because of good fuel economy and low exhaust emissions over their port fuel injection (PFI) counter parts. They operate with a lean stratified mixture in most of conditions. However, their performance is dependent on mixture stratification which in-turn depends on fuel injection pressure, timing and strategy. But, the main challenge to GDI engines is soot and particulate matter (PM) emissions. However, they can be reduced by employing multi-stage fuel injection strategy. Therefore, in the present work, an effort has been made to study the effect of fuel injection parameters on soot emissions of a GDI engine using the CFD analysis. In addition, the study is also extended to evaluate the performance, combustion and other emission characteristics of the engine. First the engine is modelled using the PRO-E software. The geometrical details of the engine are obtained from the literature.

Small gasoline four stroke engines used in motorcycle applications run mostly at part load conditions. Here fuel economy and good drivability are the major requirements. In this work, a single cylinder, four stroke, 2 valve gasoline motorcycle engine in which part load performance needs to be improved was taken for investigation. Various factors affecting part load performance were investigated and it was found that high exhaust gas dilution was the cause of high cycle by cycle variations in this engine. Commercial software was used in order to predict exhaust gas dilution levels. Based on the simulation, a set of parameters that lead to low exhaust gas dilution were arrived at. These were implemented and tested on the engine and part load performance characteristics such as combustion stability, brake specific fuel consumption and torque output were found to be improved.

Emulsification of biodiesel with water aids in reducing oxides of nitrogen (NOx) and smoke emissions simultaneously whilst improving the engine performance. However, widespread commercial applications of biodiesel-water emulsions require cost-effective surfactants that result in stable emulsions to avoid the corrosive effects of water at high temperatures prevailing in the engine combustion systems. The current investigation explored the effect of adding water to biodiesel at 6 and 12% by weight. A novel, cost-effective surfactant Polyglycerol Polyricinoleate (PGPR), was used to stabilize the emulsions. A magnetic stirrer with a heating facility was utilized to prepare biodiesel-water emulsions that were stable for over five months. The experiments were carried out on a light-duty diesel engine at a constant rated speed and varying load conditions. The results obtained with the emulsions were compared with neat biodiesel as the reference fuel.