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 work aims at simulating the possible conditions for dust entry into the CVT housing for a complete scooter and the study of different design proposals to minimize the dust entry without compromising the cooling requirement of CVT. In the first stage a full vehicle Computational Fluid Dynamics (CFD) model is solved for external steady state flow. In the second stage dust particles are incorporated in the flow domain and dust entry is analyzed. They are tracked through a frozen steady-state flow field. Particle tracking method was used to simulate the movement of the dust particle. Based on the dust entry pattern design modifications were done to reduce the dust entry. The CVT housing along with the intake system is solved to check the cooling requirements of the CVT transmission system. Moving reference Frame (MRF) method is used to generate the flow through the CVT cooling system.
There is more than 50% reduction achieved in number dust particles entering in to the CVT housing without compromising the cooling requirement. A numerical methodology has been devised to solve a de-coupled numerical steady state and transient solutions for analyzing the dust ingress in scooter CVT cooling system.