Josep Salvador-Iborra’s research while affiliated with Polytechnic University of Valencia and other places

Emissions control is a key topic for internal combustion engine development. One of the most widespread technologies to reduce the formation of nitrogen oxides is the recirculation of exhaust gas to the engine intake. Besides, carbon dioxide emissions from internal combustion engines can be reduced by increasing engine efficiency. A relevant factor for engine efficiency is heat rejection. The interaction between heat transfer and exhaust gas recirculation is not fully understood. In this paper, an experimental study is presented which aims to shed light on the influence of high pressure exhaust gas recirculation on heat transfer. Three operating points were analyzed. Heat flux was calculated at several locations of the firedeck from temperature measurements. The results showed that the influence of exhaust gas recirculation on heat transfer was significant. Reductions of heat flux up to 18% were observed. The largest reduction was found in the area near the center of the firedeck. To contextualize the findings in the framework of emissions reduction, the trade-off between nitrogen oxides and carbon dioxide was assessed for all test points.

New combustion concepts are being investigated to develop cleaner engines. One of the most promising is partially premixed combustion. The mechanisms of this combustion mode and its impact on performance and emissions have been studied in the previous years. Nevertheless, little research has been done from the point of view of heat transfer. In particular, the influence of the injection strategy on heat transfer is of great interest in partially premixed combustion. This work presents a method to calculate convective heat transfer to the piston. The method uses a combination of gas velocity models and experimental velocity data measured with the PIV technique. This method was applied to achieve the goal of studying the effect of the number of injections on heat rejection. First, the influence of the injection strategy on gas motion was examined. To do that, an analysis of the velocity components relevant to gas-surface convection was conducted, as well as of the resulting heat transfer coefficient. Next, heat flux results were discussed. The single injection strategy showed the highest heat transfer, followed by triple injection and double injection. Important instantaneous variations of heat flux were observed at different locations of the piston bowl. All findings were associated with concurring conditions of high gas velocity, density and temperature.

One of the key strategies to reduce CO2 emissions is to improve the efficiency of engines in order to diminish fuel consumption. A way to increase engine efficiency is to reduce the heat losses. Internal heat transfer in engines depends on combustion chamber conditions. Swirl is an important parameter for combustion that also changes in-cylinder variables relevant to heat transfer. In this work, influence of swirl on combustion chamber heat fluxes was investigated employing wall temperature data and a 0-D thermal model. Local wall temperatures were measured at various locations of the cylinder liner and the cylinder head using thermocouples. A sweep of swirl ratios was carried out at different engine operating conditions. It was observed that the effect of swirl effect was highly dependent on location and was more important near the center of the firedeck. Results from the 0-D thermal model were evaluated by comparing measured and predicted wall temperatures. Using a convenient arrangement of thermocouples and the 0-D thermal model, it was possible to calculate heat flux from combustion chamber to cylinder walls. By analyzing heat flux through the firedeck, an increase in heat losses between 4 and 12% was observed for each unit that swirl number was increased. Results from the 0-D thermal model indicate that similar effects occur for other surfaces in the combustion chamber.