Combustion of Biomass Particles in a Small Scaled CHP Unit

Increasing energy cost and reduction of fossil fuel resources have been resulted in increasing demand of renewable energy, such as micro biomass particles in small scale Stirling engines to generate combined heat and power. In such Stirling engines, biomass particles are burnt in external combustion chamber and then, the generated heat is transferred to the working fluid of the engine cycle. Therefore, combustion of fine particle plays basic role in operation and effectiveness of these Stirling engines. Simulation of combustion chambers of those engines using computational fluid dynamics, as a first step of engine design, can reveal more insight to optimization process. In this study, combustion chamber of 55 kW combined heat and power Stirling engine has been simulated and the effects of some parameter have been investigated. The numerical results show good agreement with experiments. Increasing secondary air mass flow rate yields hotter flue gas and higher Stirling engine efficiency. The smaller particles yield to more evaporation and combustion rate of particles which cause to increase outlet temperature. Increasing particle injection velocity causes to decrease burning rate of particle, because some particles leave out the combustor before evaporation and burning.