The aim of this study is the optimization of an air cooling circuit for a small internal combustion engine. The first analyses were about the performance of the cooling circuit of mass-produced engines. The performance has been assessed with a thermal and fluid dynamic analysis using ANSYS CFX, while the thermal boundary conditions have been separately assessed with a particular computing method. The main output data are:
• the air capacity according to the engine regime
• the pressure spring derived from the fan
• the thermal field of the cylinder/head group
• the torque/power absorbed by the cooling fan
According to the obtained results, the goals described below have been defined to obtain a new cooling circuit for a new engine:
• evaluation of the correct flow distribution between different parts involved in the engine cooling process
• minimization of fluid dynamic losses in the circuit, and consequently of the energy demand necessary to guarantee the air flow for the cooling system
• minimization of the power absorbed by the fan with respect to the air capacity
• assessment of the maximal capacity supplied by the fan with respect to encumbrance and engine regime, by acting on the blading and fixing a minimal level for the mechanical yield
The strategy to achieve these aims can be summarize in these points:
• redesign of the thermal group and the cooling cap of first attempt
• computing and designing a new fan, relying on the theory of blowing centrifuges
• assessment of the ANSYS CFX outputs (see above) for the new configuration
• circuit optimization obtained by modifying the diffuser-volute, the passages around the thermal group and the air outlets
• fan optimization obtained by modifying the design and the air inlet
The results of the study are as follows:
• enhancement of the circuit characteristic capacity/prevalence
• enhancement of the fan performance, to understand the ratio between the energy transferred to the fluid and the mechanical energy absorbed by the drive shaft
• enhancement of the flow distribution among different areas of interest
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