Comparison of dual and single spark ignition in operation of a large piston aircraft engine

The paper presents the results of the experimental research on the combustion process inside the cylinder of a large piston radial aircraft engine with dual or single spark plug ignition. The tests were carried out on the ASz-62IR-16X radial engine equipped with a double, electronically controlled ignition system with two spark plugs in each cylinder. The constant engine speed tests allowed for comparing the combustion processes with ignition carried out by both spark plugs, the rear plug only, and the front plug only. The analyses were based on the recorded pressure signal from one of the engine cylinders. It has been shown that the type of ignition significantly affects the combustion process and its non-repeatability. The obtained results indicate the leading role of the rear spark plug in initiating the combustion process. When the ignition is carried out with the rear spark plug, the induction period is identical to that for dual ignition, but the combustion process is much less intensive. Ignition carried out with the front spark plug only has a longer induction period but a similar intensity of combustion as with dual ignition. Deactivating one of the plugs also improves the non-repeatability of the combustion process.

H∞ Robust Control of a Large-Piston MEMS Micromirror for Compact Fourier Transform Spectrometer Systems

Incorporating linear-scanning MEMS micromirrors into Fourier transform spectral acquisition systems can greatly reduce the size of the spectrometer equipment, making portable Fourier transform spectrometers (FTS) possible. How to minimize the tilting of the MEMS mirror plate during its large linear scan is a major problem in this application. In this work, an FTS system has been constructed based on a biaxial MEMS micromirror with a large piston displacement of 180 μm, and a biaxial H∞ robust controller is designed. Compared with open-loop control and PID closed-loop control, H∞ robust control has good stability and robustness. The experimental results show that the stable scanning displacement reaches 110.9 μm under the H∞ robust control, and the tilting angle of the MEMS mirror plate in that full scanning range falls within ±0.0014°. Without control, the FTS system cannot generate meaningful spectra. In contrast, the FTS yields a clean spectrum with an FWHM spectral linewidth of 96 cm-1 under the H∞ robust control. Moreover, the FTS system can maintain good stability and robustness under various driving conditions.