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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.

Gasoline direct-injection (GDI) engines have evolved as a solution to meet the current demands of the automotive industry. Benefits of a GDI engine include good fuel economy, good transient response, and low cold start emissions. However, they suffer from problems, like combustion instability, misfire, and impingement of fuel on in-cylinder surfaces. Therefore, to highlight the influence of fuel injection timing on in-cylinder flow, turbulence, mixture distribution and wall impingement, a computational study is conducted on a small-bore GDI engine. Results showed that air motion inside the engine cylinder is influenced by direct-injection of fuel, with considerable variation in turbulent kinetic energy at the time of injection. Due to charge cooling effect, mixture density and trapped mass were increased by about 10.8% and 9.5%, respectively.

Use of water diesel emulsions in diesel engines has resulted in drastic reductions in NOx and smoke levels, while the thermal efficiency is also improved. The objective of this work is to evaluate the effects of using water diesel emulsion as the pilot fuel in a dual fuel engine with LPG as the primary fuel. Tests were conducted on a single cylinder constant speed DI diesel engine. An emulsion with a water to diesel ratio of 0.4:1 was used. Performance, HC, CO, NOx, smoke emissions and combustion parameters were obtained and compared with the case where pure diesel was used as the pilot fuel. At high loads, the brake thermal efficiency with the emulsion as the pilot fuel was better than that with diesel. NOx levels were drastically reduced. The already low smoke levels were reduced further with the emulsion. There was an adverse effect on HC and CO emissions. The maximum rate of pressure rise and peak pressure were also higher with the emulsion.

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.

Hybrid drive trains have to be cost effective for implementation in small two-wheelers especially scooters which constitute the majority of the market in several Asian countries. Integrating an electric motor with the conventional IC Engine drivetrain while retaining the CVT (Continuously Variable Transmission) is a cost-effective proposition. Such a development will need accounting for the behaviour of the engine, electrical drive and the belt driven CVT. A map-based engine model and a physics-based CVT model were developed in Simulink and validated with experimental data on the WMTC drive-cycle. A steady state map-based emission model and a motor model were also used. Simulations were performed on two parallel hybrid layouts namely P2 wherein the electric motor was placed before the CVT and P3 where the motor was placed in the final drive after the CVT while retaining the base 110 cc scooter powertrain.

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.

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.

Adopting a low compression ratio (LCR) is a viable approach to meet the stringent emission regulations since it can simultaneously reduce the oxides of nitrogen (NOx) and particulate matter (PM) emissions. However, significant shortcomings with the LCR approach include higher unburned hydrocarbon (HC) and carbon monoxide (CO) emissions and fuel economy penalties. Further, poor combustion stability of LCR engines at cold ambient and part load conditions may worsen the transient emission characteristics, which are least explored in the literature. In the present work, the effects of implementing the low compression ratio (LCR) approach in a mass-production light-duty vehicle powered by a single-cylinder diesel engine are investigated with a major focus on transient emission characteristics.

Almost one-third of the fuel energy is wasted into the atmosphere via exhaust gas from an internal combustion engine. Despite several advancements in waste heat recovery technology, single-cylinder engines in the market that are currently in production remain naturally aspirated without any waste heat recovery techniques. Turbocharging is one of the best waste heat recovery techniques. However, a standard turbocharger cannot be employed in the single-cylinder engine due to technical challenges such as pulsated flow conditions at the exhaust, phase lag in the intake and exhaust valve opening. Of late, the emphasis on reducing exhaust emissions has been a primary focus for any internal combustion engine manufacturer, with the onset of stricter emission norms. Thus, the engine designer must prioritize emission reduction without compromising engine performance.