Engine Breathing - Steady Speed Volumetric Efficiency and Its Validity Under Transient Engine Operation

1999-01-0212

03/01/1999

Event
International Congress & Exposition
Authors Abstract
Content
This paper questions whether the application of steady speed volumetric efficiency data to transient SI engine operation under WOT is a valid one. A state-of-the-art computer simulation model is used to compare steady speed volumetric efficiency with instantaneous values. A baseline engine model is first correlated with measured volumetric efficiency data to establish confidence in the engine model's predictions. A derivative of the baseline model, complete with variable geometry inlet manifold, is then subjected to a transient excursion simulating typical, in-service, maximum rates of engine speed change. Instantaneous volumetric efficiency, calculated over discrete engine cycles forming the sequence, is then compared with its steady speed counterpart at the corresponding speed. It is shown that the engine volumetric efficiency responds almost quasi-steadily under transient operation thus justifying the assumption of correlation between steady speed and transient data. The computer model is used to demonstrate the underlying gas dynamic phenomena graphically.
The paper provides a good example of the application of computer simulation techniques in providing answers to real engineering questions. In particular, the value of an in-depth analysis of fundamental physical phenomena characterising engine mass flow is demonstrated.
Meta TagsDetails
DOI
https://doi.org/10.4271/1999-01-0212
Pages
17
Citation
Smith, L., Fickenscher, T., and Osborne, R., "Engine Breathing - Steady Speed Volumetric Efficiency and Its Validity Under Transient Engine Operation," SAE Technical Paper 1999-01-0212, 1999, https://doi.org/10.4271/1999-01-0212.
Additional Details
Publisher
Published
Mar 1, 1999
Product Code
1999-01-0212
Content Type
Technical Paper
Language
English