Construction of a working model of a low-temperature external heat engine capable of electric power generation

Abstract

This work focuses on low-power autonomous power plants that use low-grade heat sources to convert thermal energy into mechanical and electrical energy. The task addressed relates to the insufficient efficiency of existing technical solutions for autonomous power supply to remote consumers using low-grade heat sources with temperatures ranging from 40 to 90°C. A 3D computer model of the engine and a design diagram of a utility model have been developed; an experimental prototype with the capability to generate electrical energy was fabricated. The operating cycle was mathematically modeled; rational design parameters were determined; experimental studies were conducted. It was found that increasing the displacer diameter relative to the working piston contributes to an increase in the indicator diagram area, mechanical power, as well as energy conversion efficiency. The most optimal ratio of the displacer and working piston diameters is 10:1, enabling stable engine operation at a heater temperature of 80–90°C. A distinctive design feature is the use of an enlarged displacer, magnetic synchronization of the piston and displacer without the use of a rod, and a graphite piston operating under a dry friction mode. The proposed technical solutions reduced mechanical losses, improved sealing, and enabled stable operation of the experimental prototype. Practical applications of the results include the design of autonomous low-power cogeneration power plants for powering remote sites and utilizing low-grade heat from industrial processes and solar thermal collectors