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Piston is a very important part of the engine as the contribution to its efficiency and performance is huge. This study is to understand in detail, the effect of piston skirt design on the functioning of an engine. A small gasoline engine was taken up for study. A commercially available numerical code PISDYN was used to analyze the piston liner interface. The Finite Element (FE) models of piston and the liner were used to simulate Elasto-Hydrodynamic Lubrication (EHL) between skirt / liner and piston pin / pin hole. Friction of the numerical model was validated through a tear-down motoring of the engine. The secondary motion of the piston is studied. Understanding of how the profile and the ovality of the piston skirt affects the friction, wear and impact force at the piston liner interface is gathered. Asymmetrical skirt profile is proposed and its utility to reduce the thrust force on the liner and hence its friction and vibration of the engine is explained.

Engine designers today are faced with two paramount obstacles viz. rising demand for fuel efficient vehicles and stricter emission control norms. In this regard, the piston liner interface is a very important part of the engine, as it is the source of almost half of the frictional loss of an engine and defines the blowby, lubrication oil consumption and to some extent influences the hydrocarbon emission. A single cylinder 4-stroke 110cc gasoline engine is taken up for study. A commercially available numerical code is used to simulate the piston and ring dynamics of the engine. The analytical FMEP results are correlated with the experimental FMEP found out by conducting a tear down motoring test on the engine. The blowby of the simulation model is validated with experimentally measured value of the fired engine. The effect of bore clearance and design of the piston rings on friction, oil consumption and blowby is studied.

Piston is a critical component of the engine as it exposed to high inertial and thermal loads. With the advent of high performance engines, the requirement of the piston to perform in extreme conditions have become quintessential. Piston scuffing is a common engine problem where there is a significant material loss at the piston and the liner, which could drastically affect the performance and the longevity of the components. This detrimental phenomenon would occur if the piston is not properly designed taking into consideration the thermal and structural intricacies of the engine. A water-cooled gasoline engine which had significant wear pattern on its piston skirt and liner was considered for this study. The engine block was made of aluminum alloy with a cast iron sleeve acting as liner. The piston-liner system was simulated through a commercially available numerical code which could capture the piston's primary and secondary motion.

The Valve Train system is an integral part of any engine and the impact of its design is very crucial, particularly in high speed engines. Maintaining the required valve timing throught the engine operating speed and longer component life are the two important parameters which drive current valvetrain designs. An engine ValveTrain system designed for a valve lift of 7mm is to be modified for an increased valve lift of 8mm. A study was conducted to understand which design parameters are to be changed /modified to make this possible. For this study, the valvetrain of an air-cooled motorcycle engine is taken up. The valvetrain arrangement was an Over Head Camshaft (OHC) design with a Roller-Follower. A 1D commercially available numerical code was used to simulate the kinematics and dynamics of the system.

High fuel efficiency, low ownership/ maintenance cost and favorable driving climate are the major reasons for the increasing demand for low-power commuter motorcycles and scooters, particularly in developing countries like India, Brazil and China. Noise Vibration and Harshness (NVH) has now become a new subject for the battle between competing manufacturers in attracting customers. Valvetrain noise is quite significant in the engines of these cost gasoline vehicles as they don't incorporate a Hydraulic Lash Adjuster (HLA) to keep the manufacturing costs less. The aim of this study was to understand how the cam ramp velocity and height affects the noise generated by the engine and what effect they have on its performance.For this study, a small scooter gasoline engine with an Over Head Camshaft (OHC) and a rocker arrangement with a roller-follower was considered. A commercially available numerical code was used to simulate the kinematic and dynamic behaviour of the valvetrain system.