A. Amini, M. Mirzaei, R. Khoshbakhti Saray,
Volume 3, Issue 4 (12-2013)
Abstract
In spark ignition (SI) engines, the accurate control of air fuel ratio (AFR) in the stoichiometric value is
required to reduce emission and fuel consumption. The wide operating range, the inherent nonlinearities
and the modeling uncertainties of the engine system are the main difficulties arising in the design of AFR
controller. In this paper, an optimization-based nonlinear control law is analytically developed for the
injected fuel mass flow using the prediction of air fuel ratio response from a mean value engine model. The
controller accuracy is more increased without chattering by appending the integral feedback technique to
the design method. The simulation studies are carried out by applying severe changes in the throttle body
angle to evaluate the performance of the proposed controller with and without integral feedback. The
results show that the proposed controller is more effective than the conventional sliding mode controller in
regulating the AFR without chattering.
Adel Basiri, Ebrahim Amini,
Volume 12, Issue 1 (3-2022)
Abstract
The objective of the present paper is to assess the capability of several classical damage models in prediction of service lifetime of engine components subjected to Thermo-mechanical Fatigue (TMF) loading. The focus of the present study is based on efficient and robust predictive tools which are suitable in industrial development process, thus the classical fatigue damage models are selected to perform such a tsk. In the classical framework, three strain-based models including Manson-Coffin, Smith-Watson-Topper and Ostergren models and one plastic strain energy-based model are examined. Besides, some correction factors are added to the Manson-Coffin, Ostergren and plastic strain energy models regarding the mean stress and temperature effects. The statistical analysis of the models is carried out utilizing the Low-cycle fatigue and Thermo-mechanical Fatigue tests on standard specimens of A356 aluminum alloy. The analysis indicated that modified Ostergren model is the most reliable model in fatigue lifetime description of the A356 alloy among the others. The studied engine component is a passenger-car diesel engine cylinder head made of A356 aluminum alloy. The temperature, stress and strain distribution fields of the component are considered as the given boundary conditions from our previous work as they are not in the scope of the present investigation. The selected damage models based on the best accuracy identified during statistical analysis are introduced into the ABAQUS software. The modified Ostergren model presented the most accurate and realistic results based on empirical observations of fatigue crack area in diesel engine cylinder heads studied in the literature.
