The Use of Vibration Parameters in the Research of Misfire Events in CI Engines in the Point of View of the OBD System Appliance in Diesel Locomotives

The methods of internal combustion engines diagnostic are based on utilizing the operational or accompanying processes. First of them are processes inherent in the engine operation such as the combustion of fuel, energy and heat conversion or even friction. Such methods include the gauging of: the cylinder pressure, torque and engine speed, pressure and temperature in the fuel delivery system, pressure and temperature in the inlet and exhaust manifolds, parameters strictly related to the effectiveness of energy conversion - fuel to mechanical (fuel consumption). Accompanying processes are processes that are secondary results of the operational processes (vibrations, noise, luminous effects, tribological, thermal and electrical processes). The assessment of the engine condition and its internal processes (combustion, fuel delivery and mixture formation) allows determining of the basic functional properties of the engine based on the operational parameters. The parameters resultant from such a diagnosis provide general information on the engine condition. The application of the accompanying parameters gives more detailed information on the diagnosed component, the course of combustion or misfire. The application of vibroacoustic processes (vibration, noise) in the internal combustion engine diagnostics has its merits, judging from a large information capacity of the vibroacoustic signal, rapid data transfer and high fidelity in reflecting the processes that occur during engine operation. Additionally, there is no interference in the design and operation of the engine. The occurrence of misfires during engine operation is an unwanted phenomenon. Lack of ignition results in a loss of all the chemical energy contained in the fuel dose, which leads to a decrease in overall engine effectiveness and increase in hydrocarbon and particulate matter emissions. Additionally, misfires decrease catalyst efficiency in converting toxic compounds, shorten its life and, in extreme cases, are a reason for its damage. Because of the consequences of the misfires in internal combustion engines it is of utmost importance that misfires are clearly detected and their frequency determined. The present OBD (On-Board Diagnostics) systems of passenger cars allow to detect misfire events on the basis of the assessment of the crankshaft velocity changes. Although this method has some advantages, it has also disadvantages which limit its application and decrease reliability of the detection. That is why it has appeared to be necessary to discover a new method of the misfire detection which will be reliable and possible to put into OBD strategy for different engines applications. The paper concerns the assessment possibilities of using the chosen parameters of a vibration signal to detect misfire events in an internal combustion engine. The new method of the misfire detection which is based on the assessment of some vibration signal characteristics has been made and proved to be reliable and precise for the on-board diagnostic of the compression-ignition engine. The following methodological assumptions and stages of measurements and the vibration signals analysis have been presented. The measurements results and a concept of further research to use the vibration methods into on-board diagnostic of the misfire events have been described as well.