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This paper provides an analysis of the effect of a flight altitude on knock occurrence in reciprocating SI turbocharged engines. It presents results of the computational study aimed at investigating reasons leading to knock occurrence and methods of alleviating the knock tendency of small aircraft engines. Turbochargers are frequently used to improve the performance of aviation platforms at high altitudes. Although a turbocharger provides the benefits of increased power, improved BSFC and a downsized engine, it can result in engine knock because of increasing the intake air temperature, due to a rise in the compression ratios as the air density drops. Aerial platforms experience environmental conditions that can change drastically in a matter of a few minutes. Therefore, it is important to be aware of the combined effects of altitude, initial ground temperature, humidity, flight velocity and fuel octane numbers on the emergence of knock following takeoff.

This study considers one of the challenges that arise during conversion of gasoline SI engines to ‘heavy fuel’ feeding - worsening engine performance because of intensive fuel film formation on inner surfaces of the intake manifold. A main goal of this study was investigation of an interaction process of a single fuel drop and a fuel jet with the impingement surface. Ultrasonic (US) oscillation of the latter was applied to prevent fuel film formation. Diesel fuel was chosen for our experiments because it causes more problems of mixture formation in SI engines. In the series of experiments with a single drop, effects of the drop size, ultrasound performance and a type of the impingement surface on the drop behavior were studied using a high-speed photography. In experiments with a fuel jet the phenomena of fuel film formation and size distribution of the impinging and reflected droplets were studied using a high-speed photography and PDPA/LDV technique.

In this paper we describe conversion of the gen-set gasoline-fed carburetor single-cylinder SI engine to the direct-injection version operating with the gaseous hydrogen-rich methanol reforming products, and present the first experimental results. It was found that engine feeding by methanol steam reforming products has a great potential of pollutant emissions mitigation as compared with gasoline. NOx concentrations in the exhaust gas were reduced by a factor of 7 as a result of the lean combustion and lowering in-cylinder temperatures. Particle mass emissions were mitigated to zero-impact levels. Harmful emissions of the target pollutants THC, CO and the GHG gas CO2 were reduced by a factor of 6, 25 and 1.5, respectively.