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The following article describes the low frequency vibration analysis of aircraft piston engine Rotax 912 ULS. The results are based on the vibration signal made by the engine in the frequency range up to 400 Hz measured on the engine block in three axes. The aim of the research was to determine the method of detecting the misfire of individual cylinders based on the power spectrum of the selected frequencies analysis. Frequencies resulting from the periodicity of engine operation related to the frequency of the work cycle, rotational speed and ignition frequency were considered for the analysis. The tests were carried out in one point of operation. The highest levels of changes were recorded in the Y axis - the axis of piston movement. It was shown that the vibration level changes after switching off one of the cylinders.

The ignition method significantly affects the combustion process in piston aircraft engines. This paper presents the results of bench tests of two variants of the radial piston aircraft engine: equipped with a standard magneto system and an electronic dual ignition system. The engine was tested in steady states for operating points defined by rotational speed and load. Their values corresponded to a load ranging from 50% of nominal power to take-off power. The ignition advance angle was constant for the engine equipped with ignition magnetos, while for the second engine variant it was determined by the developed algorithm introduced to the electronic ignition system control unit. The analysis of the combustion process was based on pressure measurements in one cylinder.

The paper presents the results of experiments on the effects of supply pressure and supply voltage on the pulse gas injector opening time. Two characteristics have been investigated into: the opening lag time and the time of opening. The injector's opening lag was defined as the time between the occurrence of a control signal and the moment of the valve's starting to move. The injector's time of opening was defined as the time of the valve element's movement from the closed to the fully open position. The analysis covered 6 injector types differing in the design of the valve element and the coil. The injectors types were representative of designs most popular in the market: piston and plate injectors calibrated by means of the piston stroke or the outlet diameter. The experiments were conducted in a bespoke test bed, and compressed air was used in lieu of gas fuel.

The paper describes a hybrid air-fuel mixture control system that uses neural network and the direct adaptive algorithm. The A/F ratio stabilization to the stoichiometric value is required to obtain maximum efficiency of the three-way catalytic converter operation. The issues of the algorithm synthesis of the adaptive control of the fuel injection have been formulated. This was supplemented by the presentation of the state-of-the-art in the adaptive control theory as applied to non-stationary random object identification. The control algorithms of the fuel injection have been reviewed and classified. The fuel injection algorithms in the SI engine have been described and differentiated in terms of the used engine model and regulator structure. The algorithms comprise elements of the object modeling as well as adaptive coefficients for the control quality of the air-fuel ratio in the steady and non-steady conditions.