THE JOURNAL OF ENGINE RESEARCH
Year:2009 | Volume:5 | Issue:15|Papers Count:7

Homogeneous Charge Compression Ignition (HCCI) engine is considered as a new combustion technology based on auto-ignition with higher thermal efficiency and lower emissions compared with the classic engines. In the present research, a theoretical model is provided to study the combustion regimes of HCCI engines fueled with natural gas using detailed chemical kinetics. Simulation results show that the auto-ignition process can be described using specific definitions of HCCI engines. Also the effects of combustion control parameters on the combustion initiation and in-cylinder pressure have been studied. The model is able to predict conditions for a stable controlled combustion applicable for a wide range of operating conditions. The P-q curves obtained from the model is compared with the data published in the literature and the comparison showed a reasonable compatibility in prediction of combustion initiation.

In this article, the fuel consumption and the exhaust emissions have been simulated in dual fuel (Gasoline and CNG) Samand vehicle by means of backward facing simulation. The engine performance and the catalysis convertor curves have been achieved and they have been applied for simulation of the fuel consumption and the exhaust emissions when the engine is burning either gasoline or CNG. Finally, the simulation results and chassis dynamometer test results under NEDC driving cycle are compared. This comparison indicates a good match between the simulation and the test results and it shows that this model has sufficient accuracy to use in designing and sizing of hybrid electric vehicles (HEV) that they are based on the national vehicle.

There are several methods for determining the knock intensity using cylinder pressure data, evaluation and development of these methods by analyzing test bench datasets is the basic issue of this study. At first, the methods for knock intensity determination are investigated and optimal methods are introduced by comparing test results in the fixed conditions. After determining the knock intensity by an appropriate method, threshold values must be determined for identifying knock borderline. Several methods for determining threshold values in individual cycles or statistical parameters of multiple cycles are introduced.Two methods for determining knock intensity can be compared by assuming one of them as the reference method, the way for comparison and selection of optimal parameters for second method are represented. Note that important parameters for analyzing of transducers' data, such as digital filtering and Fast Fourier Transformation (FFT), are introduced. FFT determines the main oscillation frequencies and digital filtering omits undesired frequencies.Investigations of the test results show that knock is occurred in special frequencies because of acoustic vibration modes, some methods for determining of these frequencies are introduced. It should be mentioned that the main oscillation frequency due to knock is about 8 kHz. Exact determination of these frequencies is important for investigation of filtering and optimal transducer location.

In this study, effects on a spark ignition engine of pure compressed natural gas (CNG) and mixtures of CNG and Hydrogen (Hythane) have been experimentally considered. In this study, three types of fuel including pure CNG, Hythane with 15% hydrogen and hythane with 30% hydrogen in volume are used. Tests were performed in both of full load and part load conditions. Full load tests contain engine speeds from1500 rpm up to 60000 rpm with step of 500 rpm. Part load tests were performed in engine speed of 2000 rpm and 3000 rpm. In each test, spark timing was set to reach the maximum indicated mean effective pressure. The results showed that volumetric efficiency, power and torque decreased with increase of Hydrogen fraction at full loads but thermal efficiency increased. increase of Hydrogen fraction in Hythane mixture cause Co and HC decrease but NOx increases.

In this paper, an innovative power split device is introduced and a control strategy for a hybrid transmission using the device is developed. This transmission provides a mechanical connection between engine, two motors/generators and the rotational shaft which transmits drive force to the wheels. The controller receives battery state of charge (SOC), vehicle speed and power requested at wheels, and coordinates all components in such a way to optimize the entire system efficiency. A fuzzy logic controller is designed to sustain SOC in high regions and shift engine operating points to higher efficiency regions. A numerical optimization algorithm is used to control the engine speed in order to optimize the entire system, rather than optimizing only the engine. Matlab-Simulink and Advisor software are used for vehicle modeling, simulation and implementation of the controllers. Simulation results demonstrate remarkable improvements in fuel economy relative to simulation with default controller of Advisor.

Multi-layer steel (MLS) cylinder head gaskets (CHG) are widely used to seal the engine cylinder head. Therefore, the interaction between the engine cylinder head, cylinder block and the cylinder head gasket is very important from technical point of view. To avoid the escaping gas from the engine affecting the overall performance of the engine during operation, both the pre-stressing force of the bolts as well as the gasket design are critical factors in enhancing the efficiency of the sealing of the gasket.In this paper the finite element method (FEM) is used to investigate the interaction between the cylinder head and the cylinder block. Furthermore the distribution of the contact pressure on the gasket and the cylinder head and the cylinder block stresses at different condition, such as cold assembly, hot assembly, cold start, firing, engine cooling down to 20o(c) and -25°(c) are calculated. The validation is performed using Fuji paper test and thermal survey test. The results revealed that the sealing pressure on the gasket strongly depends on the pre-stressing force of the bolts. However, the location of minimum contact pressure on the gasket is changed by considering the thermal loading.

Exhaust Gas Recirculation (EGR) method has already shown its benefits on controlling NOx emissions in internal combustion engines. By using EGR, power reduction and increase of other pollutants may be appeared; therefore use of this method needs an accurate regulation system limiting EGR cylinder-to-cylinder misdistribution. On the other hand, emission law limitations make engine manufacturers to recycle back blowby gases into the cylinders. As the same reasons, mentioned above, homogeneous distribution of blowby gases shows better performance and more emission reduction. Geometrical parameters and injection location of EGR/blowby have substantial effects on homogenous cylinder-to-cylinder distribution of EGR/blowby gases. Therefore a numerical simulation of air flow with another species gas (for example CO2 injection inside intake manifold as EGR/blowby simulation gas) is needed to evaluate the misdistribution quantitatively. Although this method is practicable, it is time consuming because of various injection locations and long solution duration. In this study a new method based on particle tracking is proposed which decreases the time and effort needed to find appropriate injection locations. Furthermore, with the new method double injection analysis is available.