Therefore, acoustic metamaterial-inspired concepts are being investigated to improve the low frequency performance of engine liners.
As excitation frequencies of engines and propellers fluctuate with changing rpm and natural frequencies of ship and some local structures change with loading conditions, resonance at certain speeds often appears unavoidable.
The operating frequency of the engine was steady at 282 Hz.
In general, due to the faults, there are peaks in the spectrum at the harmonics of the operating frequency of the engine.
The frequency and depth of the modulation are related to the fundamental firing frequency, the firing frequency of the engine and exhaust manifold design.
By analyzing the FFT spectrum of the faults signals, it was observed that the peaks in the FFT spectrum are always at the harmonics of the operating frequency of the engine.
Variations in chordwise and spanwise position of the wing-mounted engines will change the frequency of the engine-pitch mode, and further affect the low-damping flutter characteristics mentioned above, to which much attention should be paid in engineering application.
Further the injection characteristics, such as the effect of injection pressure on injection delay and the effect of engine frequency on injection delay, are analyzed.
The sheer weight and frequency of army trucks, fire engines, street-sweeping vehicles, and, finally, heavy good vehicles moving the sludge scraped up from peoples' yards and gardens in the aftermath of the influx, caused the corner wall of their old house partially to collapse.
Long crack fatigue tests have been performed at room and elevated temperature typical of the gudgeon pin boss (200 °C) using a test frequency of 15 Hz (a typical engine frequency at engine idle condition).
