DESIGN AND PARAMETRIC ANALYSIS ON AN INDUCED AIR COOLING EXHAUST SHELL
A compact 500-watt (W) portable multi-fuel rotary engine generator uses an enclosed cell to have the rotary engine unit, its auxiliary parts, and electrical wire harness packaged within it. The rotary engine exhaust gases temperature goes up to 700 C when they are emitted from exhaust port, then hot exhaust gases sweep muffler. An induced air-cooling tube is designed and coated over muffler surface to keep its temperature under a safe level. Therefore, those subsystems in the genset, which could be subjected to significant amount
of heat from the muffler surface, can be protected from structure failure. Parametric analysis of the inlet and outlet structures of the induced air-cooling muffler shell are mainly focused on and performed with the aid of the ANSYS workbench. In details, Response Surface Method (RSM) and Goal Driven Optimization (GDO) strategy in ANSYS suite was used to handle an array of sensitive design variables for a more efficient induced air cooling system. It is demonstrated that the inlet and outlet structures play an important role in the cooling
airflow rate. Optimization of their structures leads into an induced airflow rate increased from 0.224 CFM (cubic foot per minute) to 11.20 CFM. The heat transfer performances of the optimized air-cooling muffler shell are evaluated, focusing on the heat convection and radiation from exhaust gases to the induced cooling air. It is shown that high cooling efficiency is achieved by the optimized air-cooling tube at low, intermediate to high output power up to 500 W. The optimized air-cooling tube is then tested in a genset to check its
cooling performance. The test result shows muffler shell surface temperature is controlled in a safe range.