Development of a Stirling System Dynamic Model with Enhanced Thermodynamics

Power generation from renewable and sustainable sources is an important field of technology development owing to the increasing costs (both economically and environmentally) of fired generation. Most research associated with alternative forms of power generation have concentrated on relatively high efficiency systems, as this makes commercial realisation more readily achievable. A new research programme is taking a slightly different approach, where an inherently low efficiency power generation system based on low temperature differential Stirling engine technology is being considered.Here we describe the design of a low temperature differential Stirling engine for research into determining the commercial viability of utilising low enthalpy (or low grade) heat for electric power generation. While the design does not satisfy low cost economic requirements, through its ability to change important operational parameters such as compression ratio, piston phasing, and working gas movement dynamics, it is capable of identifying important features needed to optimise engine performance. The design utilises the Modified Beale Number and some preliminary software modelling, to satisfy the specifications of having a 500W output with a temperature differential of only 40 K.

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“…Sage TM is a parametric-based software tool, and is used by NASA for its Stirling machine development [8,9].…”

Section: B Design and Modellingmentioning

confidence: 99%

Low enthalpy heat stirling engine based electric power generation: A research design

Gaynor

Webb

Lloyd

2009

2009 International Conference on Clean Electrical Power

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“…heat loss from the ASC hot end through insulation material to the ambient Q loss_3 heat loss through conduction inside the ASC Q rej heat rejected from the cold end of the ASC Q total total heat generated from the GPHS Q work heat going to do the work R gas constant R 1 contact and conduction resistances between GPHS and housing wall R 2 contact and conduction resistances between GPHS and heat collector of the ASC R 3 contact and conduction resistances between the ASC hot end and housing wall R 4 conduction resistance between the cold end of the ASC and housing wall 4 …”

Section: Appendix-symbols Listmentioning

confidence: 99%

Advanced Stirling Radioisotope Generator (ASRG) Thermal Power Model in MATLAB

Wang

2011

9th Annual International Energy Conversion Engineering Conference

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This paper presents a one-dimensional steady-state mathematical thermal power model of the ASRG. It aims to provide a guideline of understanding how the ASRG works and what can change its performance. The thermal dynamics and energy balance of the generator is explained using the thermal circuit of the ASRG. The Stirling convertor performance map is used to represent the convertor. How the convertor performance map is coupled in the thermal circuit is explained. The ASRG performance characteristics under i) different sink temperatures and ii) over the years of mission (YOM) are predicted using the one-dimensional model. Two Stirling converter control strategies, i) fixing the hot-end of temperature of the convertor by adjusting piston amplitude and ii) fixing the piston amplitude, were tested in the model. Numerical results show that the first control strategy can result in a higher system efficiency than the second control strategy when the ambient gets warmer or the general-purpose heat source (GPHS) fuel load decays over the YOM. The ASRG performance data presented in this paper doesn't pertain to the ASRG flight unit. Some data of the ASRG engineering unit (EU) and flight unit that are available in public domain are used in this paper for the purpose of numerical studies. IntroductionThe advanced Stirling radioisotope generator (ASRG) (Refs. 1 to 3) is being developed for multimission applications to provide a high-efficiency power source alternative to radioisotope thermoelectric generators (RTGs). The ASRG efficiency could reach 28 to 32 percent, which results in reducing the required amount of radioisotope by roughly a factor of 4 compared to RTGs. Thus, because of the limited supply of Pu-238, utilization of the ASRG can extend radioisotope power available for future space science missions, such as deep-space missions, large planetary surface rovers, and systems in support of human exploration activities.An overview of the ASRG is shown in Figure 1. The ASRG consists of two advanced Stirling convertors (ASCs) enclosed in the housing; each has a general purpose heat source (GPHS) attached at the hot end to provide the heat. A gas management valve (GMV) and pressure relief device (PRD) are located at the top of the housing. The housing with attached fins radiates the heat to the environment. The GMV is used to maintain a near-atmosphere pressure of inert gas inside the housing during ground operations. This gas is permanently vented to vacuum by the PRD when the ambient becomes vacuum. The ASC control unit (ACU) is separate from the ASRG housing. It converts the AC signals from both ASC to 28 to 34 VDC for a typical spacecraft electrical bus. The controller is used to maintain synchronized displacer/piston movement of the two directionally opposed Stirling convertors to minimize induced disturbance to the spacecraft and its precision instrumentation.An ASC consists of a free-piston Stirling converter and an integral linear alternator that converts the piston reciprocating motion to electrical power...

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