New Stirling Motor Design With Efficiency by Using Ceramic Components

Abstract

The Institute for Product Development and Mechanical Engineering Design (PKT) at the Hamburg University of Technology (TUHH) is developing a new generation of Stirling motors for small combined heat and power plants up to a range capacity of 5 kW mechanical power output. Main objective of the project is to increase the efficiency of the Stirling motor. Reducing friction, wear and heat conductivity are the key benefits for the application of ceramic components in high loaded tribological contacts; furthermore the principle of the Stirling motor requires a lubricant free gas circuit. The applied systematically design process, based on product functions and active principles allows a target-oriented development of concepts for all components and assemblies of the Stirling motor. No simple substitution of metallic into ceramic components has been taken place, but rather a “design for ceramic” has been applied to use advanced ceramic materials in an optimal manner. Before manufacturing a prototype of the Stirling motor, mechanical tests of the main tribological contacts are intended. For these tests the authors’ institute will use two existing test rigs, the NPT (non-proportional tension-torsion test) and the MPH (Mechanische Pru¨fung von Hydraulikflu¨ssigkeiten–Mechanical Testing of Hydraulic Fluids) to investigate strength, friction and wear of the ceramic components. Within this paper at first a brief overview of the Stirling motor principle and the functions of the key components will be given. Based on this and from the tribological point of view the main requirements of the motor parts will be derived. The description of the developed motor concept with ceramic as a high temperature material will be the main part of the paper, followed by the description of the intended rig tests to analyse strength, friction and wear behaviour of the chosen ceramic materials.