Sharif Digital Repository

Most of the vehicle pollutants during emission tests are raised from catalyst inefficiency during cold start. Catalysts usually convert harmful emissions only when their temperature reaches around 250 °C to 350 °C. In this research, the vortex tube is implemented to recover the waste heat energy of exhaust gas during the cold start to improve catalyst heating. The experiments are conducted on the turbocharged direct-injection gasoline engine to extract the boundary conditions of numerical simulations. Numerical simulations are performed to evaluate the effects of different hot exhaust mass fractions on the flow regime and waste heat recovery. The results reveal that the level of turbulence... 

This paper proposes a novel method for detection and isolation of wastegate (WG) faults in a turbocharged (TC) gasoline engine. This paper starts with a fault effect analysis on the WG faults, including WG stuck open and stuck closed, which is an early step in a detection strategy design. Then, a second-order sliding-mode observer (SOSMO) is proposed to capture the exhaust manifold dynamics. The observer uses experimentally validated engine models to estimate the WG position and a virtual force. The virtual force represents the external disturbances that disrupt the WG operation and enables the proposed SOSMO to estimate the WG position robust to the faults. Using this force, a detection and... 

This paper presents a novel model-based algorithm which is able to detect and isolate major faults assigned to the gas exchange path of a gasoline engine both in the intake and exhaust sides. The diagnostics system is developed for detection and isolation of these faults: air leakage fault between the compressor and the air throttle, exhaust manifold pressure sensor fault, wastegate stuck-closed fault and wastegate stuck-open fault. Sliding mode observers (SMOs) are the core detection algorithms utilized in this work. A first order SMO is designed to estimate the turbocharger rotational dynamics. The wastegate displacement dynamics coupled to the exhaust manifold pressure dynamics is... 

This article presents a failure analysis on a gasoline engine cylinder head made of aluminum alloy, which has been used in passenger cars. During an endurance test, a crack initiated from the interior wall of a hole in the center of the cylinder head and then propagated through the thickness of the cylinder head. The metallurgical examinations are conducted in the crack origin zone. The results show that there are many casting pores due to poor quality of casting in the failed cylinder head which has certainly played a crucial role in initiating the crack. Finite element analysis of the cylinder head is performed to identify the stress components. Modeling of a bolt for the hole shows that... 

Turbocharging of gasoline engines has been improved less than diesel engines due to some difficulties, especially knock phenomena. They require wider air flow range and faster response too. A computer code is developed to simulate turbocharged gasoline engine behavior. A three zone combustion model is employed. Different performance curves at speed and equivalence ratio ranges are prepared. By this code naturally aspirated and turbocharged behavior are compared. A turbocharged aftercooled engine has been studied in various cases to complete the investigation. Some aftercooler effects are described experimentally. Modeling and experimental results are compared providing valuable achievements.... 

Estimation of relevant turbocharger variables is crucial for proper operation and monitoring of turbocharged (TC) engines, which are important in improving fuel economy of vehicles. This paper presents mean-value models developed for estimating gas flow over the turbine and the wastegate (WG), the wastegate position, and the compressor speed in a TC gasoline engine. The turbine is modeled by an isentropic nozzle with a constant area and an effective pressure ratio calculated from the turbine upstream and downstream pressures. Another physically sensible model is developed for estimating either the WG flow or position. Provided the WG position is available, the WG flow is estimated using the... 

Fault monitoring in internal-combustion engines is crucial for keeping the vehicle performance within the acceptable standards of emission levels and drivers' demands. This paper analyses how a vehicle's performance and engine variables are affected by a leakage fault in the exhaust manifold. The threshold leakage that causes the vehicle to exceed the emission standards is determined for a class M1 vehicle tested on a chassis dynamometer over the New European Driving Cycle. It is shown that, when a leakage of 6 mm diameter on the exhaust manifold is introduced, the vehicle emissions exceed those specified in the European 2013 on-board diagnostics standard. In addition, the effects of the... 

This paper presents a control oriented model for predicting turbine major variables in a turbocharged spark ignition engine. The turbine is simulated as a two-nozzle chamber where the pressure ratio over the two nozzles is not the same. A convex nonlinear estimation algorithm is formulated to determine the relation between these pressure ratios. The new model is experimentally validated with transient and steady state data collected from a 1.7 liter gasoline engine. The results show the new model can predict the turbine mass flow with an average error of 1.4%. In addition, the application of the turbine model is illustrated for the design of a nonlinear observer to estimate the turbocharger...