Automotive Stirling Engine Research Articles

Stirling engines: Advancements, applications, and environmental benefits

The increasing adoption of Stirling engines in contemporary industries is driven by their potential to address critical issues of energy efficiency and emissions reduction. Stirling engines offer higher energy efficiency, lower noise and emissions, and versatility in utilizing various heat sources, making them a promising solution for enhancing environmental preservation and energy diversity. This paper examines the growing adoption of Stirling engines in diverse industries, driven by the urgent need to address energy efficiency and emissions challenges. The paper outlines the core principles and advantages of Stirling engines, highlighting their potential to enhance energy efficiency, preserve the environment, and diversify energy sources. Furthermore, the paper underscores significant industrial and aviation applications of Stirling engines, particularly in vehicle propulsion, heat pumps, and electricity generation. Notably, the automotive Stirling engine excels in fuel efficiency and emissions reduction, offering a viable alternative to traditional internal combustion engines. Stirling engines also prove effective in heat pump systems, contributing to efficient building heating and cooling. In conclusion, despite challenges such as material requirements and heat loss, Stirling engines hold great promise as sustainable and eco-friendly thermal engines. As global concerns regarding energy and the environment intensify, Stirling engines offer a compelling pathway to improved energy efficiency, reduced emissions, and a more diversified energy landscape, driving innovation across sectors.

High pressure hydrogen effect on creep-rupture properties of superalloys

The automotive Stirling engine, being developed by the United States Department of Energy and NASA, uses highpressure hydrogen as the working fluid. The longterm effects of hydrogen at high temperature on the properties of alloys are relatively unknown. The most critical component in the engine is the heater head, which consists of the cylinders, tubings, and regenerator housing. Candidate alloys for these parts must meet the property requirements and be of low cost for automotive application. Wrought alloys for tubing and cast alloys for cylinders and regenerator housings were tested in air and 15 MPa hydrogen at 650° to 925 °C. This paper evaluates the results for wrought alloy 19-9DL and cast alloy CRM-6D. Six specimens were evaluated in creeprupture simultaneously at 15 MPa H2 under constant initial stress conditions, and creep extensions were monitored with transducers placed internally. Air and H2 data were analyzed using the Orowan-Sherby-Dorn relationship. In both 19-9DL and CRM-6D, H2 did not significantly affect the stress level of 3500- hour rupture life, and the design limits of 28 MPa at 870 °C for 19-9DL tube alloy and 119 MPa at 775 °C for CRM-6D cast housing alloys were met. However, H2 had a deleterious effect on ductility in both alloys, and alloy development is under way.

Advanced high temperature materials for the energy efficient automotive stirling engine

The Stirling Engine is under investigated jointly by the Department of Energy and NASA Lewis as an alternative to the internal combustion engine for automotive applications. The Stirling Engine is an external combustion engine that offers the advantage of high fuel economy, low emissions, low noise, and low vibrations compared to current internal combustion automotive engines. The most critical component from a materials viewpoint is the heater head consisting of the cylinders, heating tubes, and regenerator housing. Materials requirements for the heater head include compatibility with hydrogen, resistance to hydrogen permeation, high temperature oxidation/corrosion resistance and high temperature creep-rupture and fatigue properties. A continuing supporting materials research and technology program has identified the wrought alloys CG-27 and 12RN72 and the cast alloys XF-818 and NASAUT 4G-A1 as candidate replacements for the cobalt containing alloys used in current prototype engines. Based on the materials research program in support of the automotive Stirling engine it is concluded that manufacture of the engine is feasible from low cost iron-base alloys rather than the cobalt alloys rather than the cobalt alloys used in prototype engines. This paper will present results of research that led to this conclusion.