Search Results

Idle Control of Internal Combustion Engines (ICEs) is an important mode of Engine Management Systems (EMS) due to its effects on Fuel Consumption (FC) and pollutions produced in urban traffics. In this paper an optimal controller is used to control the idle speed with respect to minimization of FC in transient situations. In order to design an optimal controller a state space representation of engine in demanded. Subspace identification method is used to derive a proper state space model of engine around idle speed state. The required input/output data is generated using a mean value model. A finite time optimal controller is designed with the aim of minimizing both fuel consumption and speed fluctuations. The influence of finite time value on gross fuel consumption is then studied under various weighting factors. It is shown that the fuel consumption is sensitive to the controlling time duration for finite time LQR.

In this paper a state space representation of a turbocharged diesel engine is provided based on off-line least square method. Internal combustion engines show high nonlinear behavior due to complicated combustion phenomena and air flow dynamics inside the engine. In development phase of modern control methods like LQR controller, an accurate state space model with meaningful and measurable states is required. Identification is the method of deriving a mathematical model for dynamic systems based on input-output data. In this paper a mean value model of a turbocharged diesel engine is employed to generate demanded input-output data for identification purposes. This nonlinear mean value model predicts engine speed as a function mass of fuel injected per cycle, injection timing (ξ), ambient pressure and temperature and external loads. In the next step the simulation data is used to develop a state space model around idle mode operation state.

As it is well known one of the most harmful emissions in SI engines is NOx and there are several ways to minimize NOx emission. Internal exhaust gas recirculation (IGR) is an effective way to control and minimize NOx concentration in exhaust gas. In this paper, a method for minimizing NOx emission by use of IGR and variable valve timing (VVT) is introduced. In this method, formation of NOx is controlled by mass fraction of residual gas (RG) and mass fraction of RG is controlled by variable timing of exhaust valves opening and closing so not only the timing of exhaust valves changes but also the lift profile of exhaust valves is variable. In this paper, first a thermodynamic model of a SI engine was developed and validated by experimental data. The model was a reliable tool for predicting engine performance and emission characteristics. The effect of variable exhaust valve timing on RG mass fraction, NOx formation and brake specific fuel consumption was investigated.

The use of hydrogen as an engine fuel has great potential for reducing exhaust emissions with the exception of a small amount of carbon containing emissions originating from the lubricating oil, NOx is the only pollutant emitted. In this paper by using a turbulent flame speed method, a quasi-dimensional thermodynamic model of an SI engine fueled with hydrogen is developed. In this work, simulation results are validated by experimental data. Then the effect of spark advance, A/F ratio and valve timing on emission and performance characteristics of the modeled engine has been investigated. Hence, remarkable effects in emission and performance characteristics observed. And the behavior of the modeled engine against the above parameters has been investigated and the reason of that is discussed.

Alternative fuels are of great interest since they can be refined from renewable feedstocks, and their emission levels can be lower than those of conventional fueled engines. Despite the fact that alternative fuels are not currently widely used in vehicular applications, using these kinds of fuels is definitely inevitable in the future. In this paper, a computer code is developed in Matlab environment and then its results are validated with experimental data. This simulated engine model could be used as an appropriate mean to investigate the performance and emission of a given SI engine fueled by alternative fuels including hydrogen, propane, methane, ethanol and methanol. Also, the superior of alternative fuels is shown by comparing the performance and emissions of alternative fueled engines to those in conventional fueled engines.

One of the most vital factors in combustion control is Air-to-Fuel Ratio (AFR) control and estimation. Various parameters such as intake air mass flow rate, fuel injection quantity and (Exhaust Gas Recirculation) EGR flow rate are affecting the AFR magnitude. In this study a detailed mathematical, nonlinear and control oriented model of dynamic processes of turbocharged diesel engines is presented for the purpose of AFR control. It is an attempt to describe the two main subsystems of compression ignition engines called intake manifold and fuel injection systems. The intake model itself consists of compressor, intercooler, intake manifold, EGR circuit, valve section and cylinder subsystems. This model has been developed for study of the air intake system in a turbocharged diesel engine, using physical equations. Experimental data has also been used to adjust the model.