Abstract
This work aims to study a Stirling engine (SE) used to recover the heat content of the exhaust gas from an internal combustion engine. The attention has been focused on the heat transfer between the exhaust gas and the working gas inside the heater. Experimental tests have been performed on a two-cylinder gamma-type Stirling engine coupled to a compression ignition engine using a thermally insulated pipe and a cap. A mechanical power of 0.275 kW at 900 rpm SE rotational speed was obtained with a SE efficiency of 11.7%. To investigate how the exhaust gas-heater interaction affects SE efficiency, a 3D model was developed by the authors. The cap-heater system was studied as a shell-and-tubes heat exchanger. Experimental values of temperature and velocity have been set as boundary conditions for the cap, while for the heater, pressure and velocity have been predicted using a 1D adiabatic model adjusted for SE geometry. The results showed that temperature distribution is not uniform in both cylinders, involving that the working pistons do not work in the same way. Therefore, to improve SE efficiency, a proper configuration of SE-CI engine coupling should be designed.
Highlights
The lively debate on environmental sustainability and reduction of fossil fuel consumption has enhanced the search for new energy production methods
A mechanical power of 0.275 kW at 900 rpm Stirling engine (SE) rotational speed was obtained with a SE efficiency of 11.7%
The attention has been focused on waste heat recovery (WHR), that consists in converting the heat lost by thermal processes into additional mechanical work, especially for technologies in which a great quantity and quality of waste heat is available
Summary
The lively debate on environmental sustainability and reduction of fossil fuel consumption has enhanced the search for new energy production methods. The attention has been focused on waste heat recovery (WHR), that consists in converting the heat lost by thermal processes into additional mechanical work, especially for technologies in which a great quantity and quality of waste heat is available In this respect, WHR has a great potential for internal combustion engines (ICE) because the exhaust gas contains about 30% - 35% of total energy from fuel combustion [1]. An iterative analysis was carried out to modify heater and cooler geometry for the purpose of a uniform temperature distribution Most of these studies are theoretically focused on the SE, above all for larger engines, for which is difficult to arrange an experimental layout. No considerations about the interaction between heater and exhaust gas, that could be an interesting point of view when SE is coupled to an ICE, can be achieved
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