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The need to reduce greenhouse gas emissions by the automotive sector has demanded an increase in the efficiency of internal combustion engines as well as the use of renewable fuels, with ethanol being one of the most promising fuels. In SI PFI engines, the quality of the air-fuel mixture formed during the injection event is dependent on several factors, such as: physical-chemical properties of the fuel (density, viscosity, surface tension, latent heat of vaporization), interaction between fuel spray and gas flow / pipe walls / back surfaces the intake valves.

The quest for high efficient internal combustion engines has intensified in the last years due to, among other reasons, increasing fuel costs and the pressure to reduce environmental deterioration. One of the possible alternatives capable of providing the sought efficiency gains is the recovery of the energy wasted in the exhaust gases and turbo-compounding is one obvious option. Compression ignition engines are usually the target of turbo-compounding, however, the rising interest for alternative fuels could result in the use of turbo-compounding for spark ignition engines as well. Due to its different flame propagation mechanism, spark ignition engines may force operation at higher fuel-air ratios, eventually creating a quite distinctive operational behavior.

With the increase of thermal and mechanical loads, some spark ignition (SI) engines may present excessive wear on the piston top groove. The problem was studied first by numerical simulation. Several parameters were found to influence the groove wear. E.g., ring side face roughness and hardness. But the main influence found was the relative attitude between groove flank and ring side face. As the instantaneous attitude varies during the engine cycle, the problem was studied with a commercial ring dynamics computer program and considering thermal and mechanical deformations that occur in the piston during engine operation. The expected groove wear was estimated by the accumulated “wear load” during critical engine operation regimes. Experimental results of engines with groove wear solved by design optimization are shown.

This paper describes the development of a low friction power cell (piston, piston rings, connecting rod and bearings) for a spark-ignition 1.0 liter engine with the help of mathematical simulations. Using numerical modelling, small variations in friction power loss can be studied, which would be impossible by actual engine tests due to uncertainties in measurement process. Although it was not possible to experimentally quantify the individual component gains, the increase in engine brake power measured with the engine running with the original and modified power cells correlates very well with the simulated values.

Aiming at evaluating the effects of natural gas composition on engine operation, the Engine Group of IPT has completed a series of dynamometer tests in a Mercedes Benz M366G gas engine. Twenty-five gaseous fuel compositions, several specially prepared to extend the available CNG compositions, were engine tested. The tests were executed to evaluate performance, exhaust emissions and knock-limited spark timing. The experimental results were correlated with methane and Wobbe numbers calculated from the gas composition. The obtained data corroborate the relevance of these parameters to engine operation. For the tested engine, that uses an open loop fuel system, the data indicate the need to maintain the natural gas specifications in narrow limits if one wants to explore the natural gas low pollutant potential. This study has subsidized the elaboration of a Brazilian vehicular natural gas specification.

Today almost any engine research and development work, looking for an optimal design, performance improvement or emission reduction, demands the combustion monitoring. The simplest way to do so is by measuring the cylinder pressure, as function of piston movement or of time. This paper describes the development of a high-pressure data acquisition system that provides the basis to a flexible and powerful combustion analysis tool for engines. Similar equipment available in the market usually has embedded software, making it difficult to adapt to an unusual R&D scenario. Comparing the data gathered by the system with data collected by others means, it was possible to determine its accuracy.