This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Conditioned NExT Analysis, A Technique for Estimation of Modal Damping Ratios of Operating Piston Engines
Technical Paper
1999-01-1751
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
A new approach of estimating the modal parameters of operating piston engines is presented. The developed approach represents a combination of concepts from currently existing analyses such as the natural excitation technique (NExT), conditioned input analysis (CIA), and conditioned source analysis (CSA), and is hence termed “conditioned NExT analysis (CNA)”. NExT analysis can be employed to estimate modal parameters of structures in their naturally excited states. However, the existence of strong combustion induced periodic forcing makes the application of NExT analysis to operating engines difficult, if not impossible. CIA and CSA, built on concepts of partial and virtual coherence respectively, can effectively condition operating engine vibration data so as to remove any periodic energy associated with the process of combustion. Such conditioned operating engine vibration measurements, when combined with NExT analysis, offer a potential technique for estimating modal parameters of operating engines.
The conditioned NExT methodology is initially demonstrated by computing the modal parameters of an analytically simulated frame structure subjected to a combination of random and known periodic forcing. Subsequently, the process is extended to a controlled experiment on a steel plate, designed to simulate an operating engine environment. Guided by the results of the controlled experiment, the developed technique is extended to estimate modal parameters of an operating piston engine. The results of analysis conducted on an engine under non-operating and operating conditions are compared. Results from this research indicate the potential of the developed approach to estimate operating engine modal damping ratios. Based on the findings of this research, suitable recommendations are advanced.
Recommended Content
Citation
Govindswamy, K. and Albright, M., "Conditioned NExT Analysis, A Technique for Estimation of Modal Damping Ratios of Operating Piston Engines," SAE Technical Paper 1999-01-1751, 1999, https://doi.org/10.4271/1999-01-1751.Also In
References
- Blough, J.R. DeClerck, J.P. “Application and Development of Some Signal Processing Procedures to Estimate Frequency Response Functions of a System During Operation,” Proceedings of the 14 th International Modal Analysis Conference 1996
- Bendat, J.S. Piersol, A.G. “Random Data: Analysis and Measurement Procedures,” Wiley-Interscience New York 1986
- Albright, M.F. “Conditioned Source Analysis, A Technique for Multiple Input System Identification with Application to Combustion Energy Separation in Piston Engines,” Society of Automotive Engineers Paper No. 951376 SAE Noise and Vibration Conference Traverse City, MI May 1995
- James, G.H. Crane, T.G. Lauffer, J.P. “The Natural Excitation Technique (NExT) for Modal Parameter Extraction from Operating Wind Turbines,” Sandia National Laboratories Albuquerque, NM 1993
- James, G.H. Carne, T.G. Veers, P.S. “Damping Measurements Using Operational Data,” Journal of Solar Energy Engineering August 1996 118 118/001 118/004
- James, G.H “Extraction of Modal Parameters from an Operating HAWT using the Natural Excitation Technique (NExT),” Proceedings of the ASME Wind Energy Symposium 1994 15 227 232