A. Paykani, R. Khoshbakhti Saray, A. M. Mohammadi Kousha, M. T. Shervani Tabar,
Volume 1, Issue 2 (6-2011)
Abstract
In this study, a numerical simulation using the CFD software, FLUENT, has been conducted to examine the effect of various shapes of the venturi component sections in order to find the optimum venturi specifications to increase the EGR rate with minimum pressure loss at the part load operation range. The CFD results reveal that the venturi should be precisely optimized to introduce the required amount of EGR to the engine manifold. Then, the optimum venturi was manufactured, and it was installed on the engine intake system. By using the optimum Venturi EGR system instead of original system the 26% increase in EGR flow rate to the engine manifold is observed. In the second part of the paper, an experimental investigation was carried out on a “Lister 8-1” dual fuel (diesel – natural gas) engine to examine the simultaneous effect of inlet air pre-heating and EGR on performance and emission characteristics of a dual fuel engine. The use of EGR at high levels seems to be unable to improve the engine performance at part loads, however, it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency, resulting in reduced levels of both UHC and NOx emissions. CO and HC emissions were reduced by 24% and 31%, respectively. The NOx emissions were decreased by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.
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.
