Search Results

Aerodynamics is of vital importance in the development of a high-performance super-sports motorcycle. It directly links with the product’s performance in terms of top speed, handling dynamics and user experience. The objective of this work is to achieve the best-in-class aerodynamic performance of a motorcycle using a comprehensive method, involving wind tunnel testing and CFD (computational fluid dynamics) modelling. Focus of the study is to understand the impact of aerodynamic forces on the ride comfort and handling (safety), in case of high-speed operation. In this work, a comprehensive CFD model is developed to assess the aerodynamic performance of a motorcycle. The model is validated with wind tunnel measurements – both for integral parameters, namely, coefficient-of-drag (????) and coefficient-of-pitching moment (????) and for a discrete parameter, which is coefficient-of-pressure (????), measured at 30 different locations on the motorcycle fairing.

At part load conditions, effective utilization of fuel is critical for drivability of an IC engine driven automobile, with minimum emissions and fuel consumption. It becomes cardinal to study the mixture preparation in engines to understand the injection strategy that helps in achieving the prime objectives of lower emission and reliable operation. To add to the complexity of the problem being studied, the injection phenomenon is rapid, turbulent, multi-phase, two-way coupled (where the continuous phase affects the droplets and vice versa) and involves turbulence length scales and time scales, few orders of magnitude lower compared to the characteristic length in the turbulence integral scale. A methodology is developed in Star-CD and ES-ICE to simulate the mixture preparation in Port Fuel Injection (PFI) engines.

Thermal management is of vital importance in the development of a scooter type motorcycle (two-wheeler). Traditionally the thermal management development of a two-wheeler is done through experimental methods, or using sub-system level CFD models. In current work, a comprehensive, complete vehicle, three-dimensional CFD model has been developed to assess thermal performance of the scooter and its sub-systems. The model can predict thermal performance in different operating conditions, such as, wide open throttle, idling and key-off. A typical thermal interaction in engine happens through metal contact conduction, air cooling and oil flow path in the engine. The model can capture the sub system interaction, such as, an interaction between the cooling system and engine cabin. Modeling oil is computationally expensive, as it involves complex physics modeling such as multiphase flow.

One of the major reason for lower efficiency and higher unburned hydrocarbon and carbon monoxide emission for two stroke engine is short circuit losses during the scavenging process. An attempt has been made in this study to understand and improve this phenomenon. A three dimensional transient CFD model is developed for a loop scavenged, Schnullar type, 70 cc two stroke engine. Three major processes, namely, blow down (expansion); scavenging and compression have been modelled. The model is validated with PIV measurement done in motoring mode. Model is also validated with experimental data for trapping efficiency with Watson method and for in-cylinder pressure during expansion, blow down and intake events. A good correlation is observed between experimental and simulation results. CFD model is used to quantify various parameters, such as, delivery ratio, trapping efficiency, scavenging efficiency, and amount of fresh mass short circuit at different load and speed points.

The concept of fuel-air mixture stratification is evaluated for a single cylinder, 200-cc CNG-fuelled SI engine with port gas injection (PGI). A detailed study based on three-dimensional computational fluid dynamics (CFD) modeling has been reported. Fuel-air stratification was observed in case of PGI compared to premixed fuel-air mixture formed by a conventional gas carburetor system. Overall stratification of more than 15% was observed for PGI between the rich and lean zones in the combustion chamber compared to less than 1% in case of premixed gas carburetor. It was observed that the gas injection location, direction, timing, duration and injection pressure have a significant effect on stratification pattern.

We present the results from the 3-D numerical simulations on the optimization of the fan-cooling system in a two-wheeler 4-stroke single cylinder engine. Objective was to optimize the flow rate and distribution of flow over the engine surfaces to keep the maximum temperature of engine oil and engine surfaces well within the lubrication and material limit respectively at the expense of minimum increase in fan power. This work aimed at reducing the engine oil temperature by 20°C. Combined flow and heat transfer analysis (Conjugate analysis) was conducted with the engine head and block modeled as solid medium and fan cooling system modeled as fluid medium. Reynolds-Averaged-Navier-Stokes turbulence (RANS) equations along with energy equation were solved to get the flow field and temperature distributions inside the cooling system and on the engine surfaces respectively. Moving Reference Frame approach was used for simulating the rotation of fan.

Competitive environment of scooter market demands for new improved products with minimum development time. Computer simulations are very useful in reducing the development time through virtual prototyping and testing the system on computers rather than making the hardware prototypes and testing on road. Particularly, lumped parameter modeling provides reasonably accurate results for predicting vehicle performance characteristics in short span of time. This is very useful when various system level targets have to be achieved and when trade-offs have to be made to obtain optimal results. In this work, a system-level powertrain model has been developed for small variomatic scooters with a mechanically actuated Continuously Variable Transmission (CVT). The modeling and simulation technology developed in this work can aid in designing a scooter CVT system to provide the desired performance characteristics.

Progressive demand being placed on more efficient and quite engines require engine subsystem to be optimized without compromising their performance. Cooling system is one of the important engine sub system to be optimized to achieve better performance with reduced noise levels and with minimum power consumption. In the present paper an effort is made to optimize a fan-driven air-cooling system for a small 4-stroke scooter engine. Complete three-dimensional analysis has been done with commercially available computational fluid dynamics (CFD) codes. Analytical results are validated with the experimental results. A good correlation has been observed between analytical and experimental results. The work is done in two phases. In the first phase, complete flow and heat transfer analysis of the present system has been done. Flow analysis revealed flow blockage, significance of leakage through various parts of the cowling, and separation of the flow inside the vane passages of the fan.

A 1-D Thermodynamic analytical model is developed using commercially available code, to study the gas-exchange process in a 125cc, single cylinder 4-stroke engine. Model is validated against the experimental results by comparing the pressure traces inside the cylinder, intake and exhaust pipe. Detailed parametric study has been conducted using the analytical model to optimise the valve timing, elements of intake and exhaust manifold. Design of experiment (DOE) technique is used to find the effect of individual parameter and optimum combination is obtained for the desired performance level. The results from analytical predictions are in good agreement with the experimental results for the optimised combination.