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Technical Paper

Numerical Analysis of Cooling Process of an Torch Ignition System

The internal combustion engines require an efficient cooling system, the high temperatures generates at the time of combustion, reaching 2500 K peak burned gas. The materials used in the construction of the cylinder must operate within a maximum value, as well as the fluid film of lubricant oil. A bad dimensioned cooling system can lead to serious consequences such as loss of engine performance and/or efficiency, pre-ignition and increased exhaust emissions and may even lead to the destruction of the engine. In the torch ignition system overheating of the pre-chamber is even more critical and may lead to significant losses. Thus the torch ignition system requires an efficient cooling to prevent deterioration of the pre-chamber and consequently the engine caused by overheating. The solution proposed to resolve this inconvenience is the use of the cooling gallery in the cylinder head, for cooling the pre-chamber that is selected.
Technical Paper

Modeling of a Torch Ignition System Using One-Dimensional Model of Computational Simulation

An torch ignition system with homogeneous charge is numerically analyzed using a one-dimensional computational model. The new ignition system is implemented in a four-cylinder engine, spark ignition, 1600 cm3, 16 valves. Parameters such as mass burn fraction profile and pressure vs crank angle are compared with experimental data obtained with the torch ignition system operating homogeneous charge with stoichiometric mixture. The computational model uses information such as the pre-chamber pressure as a function of crack angle, intake and exhaust pressure, volumetric efficiency, maps of injection and ignition, valve discharge and valve intake coefficient, lifting valve, laminar flame speed, among others parameters.
Technical Paper

Longitudinal Performance of a BAJA SAE Vehicle

Driven by the necessity to reduce costs and improve products quality the automotive industry replaced the design method known as "trial and error" by those grounded on mathematical and physical theory. In this context, a longitudinal performance test was made by BAJA SAE UFMG team, in order to acquire vehicular performance data that will be used to validate computer models. The methodology consists of sensors and data acquisition system research, validation, fixation and installation in the vehicle, test and process of acquired data. From these steps, correlated data were acquired from magnitudes such as angular velocity in transmission shafts, global longitudinal acceleration and velocity, travel of break and throttle pedals and pressure inside of master cylinder. These results developed the knowledge about vehicular dynamic allowing the improvement of futures prototypes.
Technical Paper

Dynamic Analysis of Spark Ignition Engines

To attend the new tendencies of the automotive market, new technologies must be used throughout the engine conception. One way of improving the project is to use computational numerical simulation, predicting engine behavior in a wide range of situations. This paper presents a methodology to estimate the engine characteristic parameters necessary to numerical simulation. Morse test was used to determine friction power, mean effective pressure friction and friction torque, considering the engine behavior during cylinder ignition cut-off. In this test all the results were compatible with manufacturer data, which validates the methodology. To define the moment of inertia, it's also proposed a fuel cut methodology, associated with the Morse test, because the torque values measured by dynamometer after the fuel cut did not correspond to the real value. Thus, plausible values of engine moment of inertia, very close to values obtained by software, were obtained.
Technical Paper

Direct Injection Diesel Engine Cylinder Pressure Modelling via NARMA Identification Technique

Future engine control systems need suitable and accurate models for combustion. For this purpose, this paper presents a practical application of nonlinear autoregressive moving average polynomial models with exogenous inputs (NARMAX) technique to model pressure dynamics inside the cylinder of a direct injection compression ignition engine. Two models have been investigated taking two different sets of input variables. The first model only includes basic injection settings available from the electronic control unit. The second model uses the instantaneous crankshaft revolution speed as a main model input. Model parameter identification and validation are performed with experimental data obtained from a test engine equipped with a piezoelectric pressure sensor and with data computed from a thermodynamic-based engine cycle simulation code.
Technical Paper

Combustion influence of a pre-chamber ignition system in a SI commercial engine

Environmental policies and fuel costs have driven the development of new technologies for internal combustion engines. In this sense, the use of mixtures with small portions of fuel allows lower fuel consumption and pollutants emissions, emerging as a promising strategy. Despite the advantages, lean burn requires a larger energy source to provide satisfactory flame propagation speed and consequently a stable combustion. The use of pre-chamber ignition systems (PCIS) has been used in SI engines to assist the start of combustion of lean mixtures, in which a supplementary fuel system can stratify the amount of either liquid or gaseous fuels supplied to the pre-chamber. In this context, this paper aims to evaluate combustion characteristics of a commercial engine with the use of stratified PCIS operating with impoverished mixtures of ethanol-air in main-chamber and hydrogen assistance in pre-chamber.
Technical Paper

Characterization of a Multi-Cylinder Torch Ignition System Operating with Homogenous Charge and Lean Mixture

The present work aims to analyze a torch ignition system running on lean homogeneous charge, adapted to an Otto cycle multi-cylinder engine. The main objective is to maximize engine efficiency by means of redesigning the ignition system adapting a pre-chamber to the main combustion chamber. This new ignition system allows reducing its IMEP covariance for leaner mixture operation due to the increase of ignition energy availability during the kernel formation. The engine used in this research is a commercial sixteen valve, four cylinders in line with cubic capacity of 1600 cm3. The performance date of baseline engine operating stoichiometrically were used as a reference for the comparison with torch ignition engine output running from stoichiometric mixture to its leaner operational limit. The brake mean effective pressure was maintained constant in all test configurations in order to make possible to compare engines thermal efficiency.
Technical Paper

Analysis of Back Pressure Variation on Macroscopics Characteristics of Ethanol E100 Spray

The growing demand for more efficient and less polluting engines has lead the scientific community to further develop the road map engine technologies, including direct fuel injection. Direct injection research demands the investigation of spray formation and its characteristics. The present work performs the characterization of the macroscopic parameters of ethanol sprays (E100) produced with a fuel gauge pressure of 80 bar and gauge back pressures of 0, 5 and 10 bar. The sprays analysis was performed using high speed filming by means of Shadowgraph technique. Computational routines of matrix analysis were applied to measure the spray cone angles, penetration and penetration rate. The spray visualization demanded an experimental apparatus composed of a pressurized cylinder with nitrogen, a fuel tank as pressure vessel, an injection driver equipped with a peak and hold module controlled by a MoteC M84, a Phantom V7.3 high speed camera and LEDs for illumination.