NASA Glenn has made significant use of two Stirling machine codes, in recent years, for prediction of Stirling engine performance and for engine design studies. These are HFAST and GLIMPS/GLOP. Predictions of HFAST and GLIMPS were compared with experimental data from two engines in (Geng and Tew, 1992). The abstract from this report is as follows:

"Predictions from GLIMPS and HFAST design codes are compared with experimental data for the RE-1000 and SPRE free-piston Stirling engines. Engine performance and available power loss predictions are compared. Differences exist between GLIMPS and HFAST loss predictions. Both codes require engine-specific calibration to bring predictions and experimental data into agreement."

In the early years of the Automotive Stirling Engine Development Project a Stirling engine performance code was written at NASA Glenn and used in monitoring contractor analysis efforts and in studying the impact of changes in Stirling engine design, operating conditions, working fluid, etc. (Tew, Jefferies, and Miao, 1978 and Tew, 1983). This code was a one-dimensional fluid-flow, explicit finite-difference code written for use on mainframe computers; it fell into disuse when the much more user-friendly and time efficient desk-top computer based codes, HFAST and GLIMPS, became available.

HFAST

Mechanical Technology, Inc (MTI) began work on HFAST in the 1970's during the early phases of the Automotive Stirling Engine Development Project. MTI's early automotive engines were designed almost entirely by their subcontractor, United Stirling of Sweden, with their Philips Laboratories' derived code (Philips Laboratories of the Netherlands); design of MTI's later Stirling automotive engines was based primarily on use of the HFAST code, with supporting calculations by United Stirling.

Evolution of HFAST continuted at MTI during development of the free-piston Stirling space power engines: the 12.5 kWe/cylinder Space Power Demonstrator Engine (SPDE) and Component Test Power Convertor (CTPC). During approximately the last 5 years of this effort, from about 1988-1993, a separate Harmonic Code Contract with MTI supported upgrades to the HFAST code and permitted NASA to gain unlimited rights to use and distribution of the HFAST code, as it existed at the end of the contract.

A description of the HFAST code, taken from (Geng and Tew, 1992) is as follows: "HFAST is a constrained mode simulation that assumes the variables are harmonic functions of time. The solution is found by solving a system of nonlinear, algebraic equations which are created by substituting harmonic functions in the governing differential equations. HFAST is a one-dimensional model comprised of a variable number of components relating to the working space of a Stirling-cycle machine. Each component is divided into a number of control-volumes. The user specifies the number of components and control volumes used in the model." HFAST includes an optimization routine that permits its use in engine design optimization. HFAST was described by the principal investigator of the Harmonic Code Contract, Dr. Shyan Huang of MTI, in (Huang, 1992).

HFAST is written in Microsoft FORTRAN. For engine performance calculations it requires several seconds on an IBM 286 type desk-top computer that has 1 MB of RAM. For engine design optimization, which could require several hundred performance calculations, a 386 or 486 type desk top computer would be more convenient.

At this time, the HFAST code is not available for distribution outside the U. S. and the source code is not available for distribution (the code is, however, written in a very general format and can simulate a wide variety of different geometries with the available object code).

GLIMPS/GLOP

GLIMPS/GLOP is a commercial code available from Gedeon Associates of Athens, Ohio. GLIMPS is used for engine performance predictions; it's input format is somewhat more user-friendly than that of HFAST (Input variables are described in English, instead of the FORTRAN style variable names used for HFAST input). GLOP contains the optimization routines which permit GLIMPS/GLOP to be used for engine design optimization. GLIMPS/GLOP have also been used for performance prediction and design of cooling machines by private industry.

GLIMPS/GLOP was developed by David Gedeon of Gedeon Associates. David was the primary analyst at Sunpower, Inc. in Athens, OH before going into business for himself. A description of GLIMPS taken from (Geng and Tew, 1993) is: "GLIMPS is a constrained mode simulation that uses a globally implicit technique to solve a system of algebraic equations simultaneously. The algebraic equations are finite difference representations of the governing differential equations. GLIMPS is a one-dimensional model comprised of up to 7 components relating to the working space of a Stirling cycle machine. Each component is divided into a number of computational-cells. The computational domain is broken into discrete time nodes as well. The user specifies the number of computational-cells and time nodes used in the model."

Gedeon described an early version of his code in (Gedeon, 1986). A much more complete and up-to-date description of the code is the user manual (Gedeon, 1992), available for purchase from Gedeon Associates. Gedeon is working on a successor to GLIMPS/GLOP which he has called the SAGE code.

GLIMPS/GLOP is written in Microsoft PASCAL. Performance calculations made with GLIMPS at NASA on an IBM 286 computer required approximately two minutes (this is a function of the number of spatial nodes and time steps chosen).

For information regarding the price and availability of GLIMPS/GLOP or SAGE contact:

References

1. Gedeon, D., 1986, "A Globally-Implicit Stirling Cycle Simulation", Proceedings of the 21st Intersociety Energy Conversion Engineering Conference, Vol. 1, pp. 550-554.
2. Gedeon, D., 1992, "GLIMPS version 4.0 User's Manual", Gedeon Associates, 16922 South Canaan Road, Athens, OH 45701
3. Geng, Steven M. and Tew, Roy C., 1992, "Comparison of GLIMPS and HFAST Stirling Engine Code Predictions With Experimental Data", NASA TM 105549 (Also in Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, 1992)
4. Huang, S. C., 1992, "HFAST: A Harmonic Analysis Program for Stirling Cycles", 27th Intersociety Energy Conversion Engineering Conference
5. Tew, Roy C., Jr., 1983, "Computer Program for Stirling Engine Performance Calculations", NASA TM-82960
6. Tew, Roy; Jefferies, Kent; and Miao, David, 1978, "A Stirling Engine Computer Model for Performance Calculations", NASA TM-78884

Last updated: Thursday, May 23, 1995

[ Home ] [ Up ] [ Power ] [ Concentrators ] [ Sec Concentrators ] [ Thermal ] [ Projects ] [ Capabilities ] [ Publications ] [ Personnel ] [ Site Map ]
[Power & On-Board Propulsion Technology Division]
[NASA Privacy Policy ]  [NASA Disclaimer]  [NASA Accessibility]

Curator: Wayne A. Wong
  NASA Official Responsible For Content:  Richard K. Shaltens
* an asterisk indicates an external link
Last Updated: 07/31/2002