Evaluation of the combustion-induced noise and vibration using coherence and wavelet coherence estimates in a diesel engine

Abstract

The understanding of noise generation and source identification is vital in noise control. This research was conducted to experimentally evaluate combustion-induced noise and vibration using coherence and wavelet coherence estimates. A single-cylinder direct-injection diesel engine was chosen for experimental investigation. The independent variables for conducting experiments were injection timing with five levels of 22, 27, 32 (normal), 37, and 42 crank angles before the top dead center, and also the engine torque load with four levels of 55%, 70%, 85%, and 100% of the rated value. The signals of cylinder pressure, liner acceleration, and radiated sound pressure of the test engine were measured and recorded. Then, coherency and wavelet coherency experiments were carried out between cylinder pressure and liner acceleration, cylinder pressure and sound pressure, and liner acceleration and sound pressure signals in MATLAB software. The results indicated that increasing load would increase wavelet coherency between cylinder pressure and liner acceleration signals at frequencies higher than 1 kHz. The coherent regions between cylinder pressure and sound pressure signals were mainly at frequencies higher than 1 kHz while advancing the fuel injection timing had shifted the coherency toward lower frequencies. In general, with advancing injection timing, the coherent regions between liner acceleration and sound pressure signals have appeared at broader time ranges, especially at frequencies between 100 and 500 Hz. Comparing the results of the wavelet coherency and coherency tests, we concluded that wavelet coherency is a more accurate and descriptive tool in evaluating the combustion-induced noise and vibration.

Analytical and numerical modeling, sensitivity analysis, and multi-objective optimization of the acoustic performance of the herschel-quincke tube

“…Computational Aeroacoustics analysis (CAA) has been implemented in the ANSYS 19.3 Fluent software environment. As we know, the dominant frequencies in an IC engine noise spectrum, are the harmonics of the firing frequency [22]. So, the optimized geometry configuration or the efficient solution among the Pareto set was chosen to be the solution with rank 9 in Table 6; because it maximized the TL in the lowest frequency and reduced the BP simultaneously.…”

“…According to Table 1, in this research, the desired frequency range for the geometry optimization of the HQ tube was 20-2000 Hz. This is mainly because the frequency response of IC engine noise has its most energy in this range [22]. Also, for the tube length, the range was chosen to be between 0.01 and 0.5 m. Other parameter ranges in Table 1 were calculated using their representing equation.…”

Study on the influence of various factors on block vibration

“…3,4 The piston secondary motion led to the collision between the piston and cylinder liner, and the slap energy transferred through the engine block structural path. 5 Block vibration induced by piston slap can be used to estimate the status of the piston-cylinder pair.…”

Design and Performance Analysis of an Ultrasonic System for Health Monitoring of Concrete Structure

“…The working performance of the amplifier circuit and the filter circuit in the receiving module is evaluated by the amplification and filtering curve of the actual test data. Under the same conditions, 40 ultrasonic waveform data transmitted in the air are continuously collected, then the Pearson correlation coefficient, RMSE, and amplitude-squared coherence [ 19 , 20 ] are calculated to evaluate the continuous working stability of the ultrasonic detection system designed in this paper. The experimental results and their performance analysis prove that the designed system can work stably and reliably.…”