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The Torque from an engine is a very critical parameter which controls the drivability of the vehicle, better torque availability at Partially Open Throttle (POT) condition improves drivability at city driving condition and better torque at Wide Open Throttle (WOT) condition improves cruising at highway driving condition, conventionally engine produces better torque at one particular operating condition leaving poor drivability at others. The Torque characteristics of an engine depends upon the volumetric efficiency of the engine. The volumetric efficiency of a naturally aspirated engine can be improved by tuning the intake manifold. With an overall improvement in volumetric efficiency throughout the engine operating conditions better torque curve can be achieved, which facilitates improved drivability.

In scooters, the Continuously Variable Transmission (CVT) is used to transmit the power from the engine to the wheels. The CVT transmission consists of a two pulleys connected to each other through a belt. The change in the transmission ratio is achieved due to the change in the pulley diameters. A centrifugal clutch is attached to the rear pulley to transmit the power to wheels once the engaging engine speed is reached. The heat is generated due to the belt slippage and the engagement of the centrifugal clutch. Excessive heating may damage the belt, clutch and deteriorate its performance. The cooling of the belt, pulleys and the clutch is thus important for its safe operation. The cooling is achieved by the centrifugal cooling fan which forces the air over the belt, pulley and clutch. A clear understanding of the cooling system is important in designing the air flow path for clutch cooling of CVT housing.

The Continuous Variable Transmission (CVT) in scooters is used to transmit the power from the engine to the wheels. The CVT transmission consists of a drive pulley and a driven pulley connected to each other through a belt. The centrifugal clutch is attached to the rear pulley which transmits the power to the wheel. The engagement and disengagement of the clutch generates heat and friction heat is generated between the belt and pulley, thereby requiring continuous external cooling for its safe operation. A centrifugal fan is employed for cooling of the CVT belt. Since the cooling fan takes air from atmosphere, there is always a possibility of dust from the atmosphere entering the system, which might cause wear of pulley and belt, thereby decreasing the performance of the transmission system. The objective of the work is to analyze the dust ingress pattern in to CVT housing.

The demand of Torque from an engine is highly variable, good torque at lower engine speeds improve drivability at city driving condition and good torque at higher engine speeds improves cruising at highway driving, conventionally engine produces better torque at one particular speed leaving poor drivability at others. The Torque characteristics of an engine depends upon the volumetric efficiency of the engine, volumetric efficiency of a naturally aspirated engine can be improved by tuning the intake manifold. For improving volumetric efficiency, several technologies were developed, among that Dual Intake Manifold system is one where the flow of charge is channelized between longer and shorter flow path depending on the engine operating speed. Application of conventional Dual Intake Manifold system is limited due to increased cost, complexity in assembly and need for an external power source for actuation.

Scooters are popular for the legroom available in the front and closed storage space beneath the seat. Engine is located at rear part of the vehicle beneath the storage space and is cooled by forcing the air by a centrifugal fan over the engine surface. Heat is rejected from the engine by the forced cooling and radiation to the surroundings. Storage space gets heated as result of excessive heat rejection from engine. To protect the material of storage space and the items stored in that, it is necessary to avoid heating of the storage space. The work aims to conduct the storage space heating analysis in a scooter. The objective is to propose the design modifications to reduce the storage space heating. The effect of convection and radiation in heating of the storage space is studied.

The basic requirement of a vehicle cooling system is to ensure that the components of the engine are adequately cooled under vehicle operating conditions. Engine life and effectiveness can be improved with effective cooling. In designing process, simulation plays a vital role. A clear understanding of the coolant flow and pressure developed within the cooling system is important in designing the coolant circuit. The efficiency of the cooling system depends on the flow delivered by the impeller. The work aims at the study of performance characteristics of a backward curved impeller in a two wheeler cooling system. The objective is to compare the operating points such as pressure drop, flow delivered and power consumed from mapped Computational Fluid Dynamics (CFD) simulation and closed loop CFD simulation. Moving Reference Frame (MRF) model was used to simulate the rotary motion of the impeller.

The effective cooling of a two wheeler scooter engine depends on the efficient performance of the cooling fans. In scooters, centrifugal fan with axial air inflow and radial outflow with either backward curved or forward curved blades are used. The air flow enters the unit axially and then spreads out turning to 90 degrees into radially outward direction before meeting the engine. The work aims at the study of performance characteristics of the forward and backward curved fans when put in to engine cowling and to compare the power consumed and flow delivered by the fans. The objective is to compare and reduce the power consumed by the cooling fans and to increase the air flow velocity across the engine surfaces. A Conjugate Heat Transfer analysis has been done to study the effect of forward and backward cooling fans on flow delivered, power consumed and engine surface temperature. RANS K-Epsilon two equation turbulence model was used to solve the 3-D numerical model.

Engine life and effectiveness can be improved with effective cooling. In designing and optimization process, simulation plays a vital role. The cooling mechanism of the air cooled engine is mostly dependent on the fin design of the cylinder head and block. The heat is conducted through the engine parts and convected to air through the surfaces of the fins. Insufficient removal of heat from engine will lead to high thermal stresses and lower engine efficiency. To simulate the cooling mechanism of the naturally aspirated engines, Three Dimensional CFD analyses with the SC/Tetra code is done. This gives a good scope in analyzing the existing fin design and proposes the optimized design. The boundary conditions required for carrying the CFD analysis such as the heat transfer co-efficient, cylinder temperature, has been generated by carrying One Dimensional engine cycle simulation.

Extensive research is being carried out to improve the volumetric efficiency of the engine by improving port flow. Port flow characteristics plays vital role in determining the overall performance of SI engine. Higher volumetric efficiency demands the flow capacity of the ports. Steady-state flow bench testing and CFD steady flow simulation analyses are widely used promising tools in the process of port development for flow optimization. CFD port flow simulation adds cost effectiveness to the port modification process. With help of port flow information obtained from the flow bench testing, the engine power curve and system dynamics can be roughly estimated. However actual engine running is transient in behavior, i.e. the pressure difference varies widely during the whole cycle whereas the port flow testing on flow bench is steady state in nature. In the flow bench testing, the effects such as cyclic acceleration and deceleration of fuel-air column are not accounted.