No abstract

In the conditions of continuous operation of a car tests of its engine for compliance with the declared environmental class on specialized test benches seem to be quite costly and laborious. Given this circumstance, in this paper a simplified method for verifying the operability of converters is proposed including the assessment of the influence of certain operation modes and some operational factors on the amount of hydrocarbons and carbon monoxide emissions. Efficiency of the converter was estimated by comparing the experimental data on the emissions of these toxic components in the exhaust system before and after the converter. To test the efficiency of the converter, the cold start and warm-up modes of the engine were selected and investigated, as well as several modes close to those typical for testing the engine and car in urban areas according to the European Driving Cycle. As operational factors, typical malfunctions were investigated that often occur during the operation of an engine and significantly increase the amount of harmful emissions. A criterion is proposed for evaluating the performance of the converter and recommendations are given to increase the efficiency of the converter to meet the certain emission standards for cars with spark-ignition engines.

No abstract

Liquid cooling of cylinder and piston parts in highly boosted internal combustion engines is generally accompanied by local phase transition phenomena, such as surface nucleate boiling. The heat transfer coefficient of nucleate boiling is several times higher than that of single-phase convection. In order to efficiently exploit the thermal effect of nucleate boiling in cooling systems, simultaneously preventing emergency supercritical modes, a deeper understanding of boiling physics based on full-scale experiments is required. We conducted experimental investigation of heat transfer in a simulated cooling duct of a piston engine cylinder head, using a bespoke motor-free installation. We studied the effects of velocity, flow character and coolant type on the heat transfer, accounting for the presence of congestion regions. Over the course of the experiment, we simulated thermal conditions characteristic of different heat transfer types: single-phase convection, nucleate boiling, the onset of boiling crisis. We used the experimental data to plot the coolant heat flow density as a function of wall temperature for different measuring points situated inside the stream and the turbulent flow regions (congestion regions). We show that the mature nucleate boiling mode is the most favourable in terms of how uniform the temperature field within a part is. The experimental data obtained during the investigation may be used to verify mathematical simulations in the two-phase heat transfer theory, provided the data have been appropriately processed