New methodology for in-cylinder pressure analysis in direct injection diesel engines—application to combustion noise

Abstract

The objective of this paper is to present a new methodology for the analysis of in-cylinder pressure in direct injection (DI) diesel engines. Indeed, for some applications, the traditional study of total pressure is shown to be insufficient and the proposed technique is intended to be an alternative and more efficient tool, since it may provide a better understanding of the physical mechanisms. The main idea is to decompose the in-cylinder pressure evolution according to three phenomena taking place during diesel engine operation: pseudo-motored, combustion and resonance excitation. In order to validate this new method, it is applied to combustion noise analysis. Actually, the combustion process in DI diesel engines may be considered as an important source of noise, and the traditional approach is mainly based on the interpretation of objective overall spectral levels of both in-cylinder pressure and radiated noise, obtained from Fourier analysis. However, this approach has been shown unable to describe all the relevant aspects of the problem, whereas the results obtained from the proposed decomposition technique exhibit a fair qualitative correlation between in-cylinder pressure and combustion noise issues. Further development of this approach could provide a useful tool for the development of optimal injection strategies fulfilling not only performance considerations but also sound quality requirements for combustion noise in DI diesel engines.

Impact of Fischer–Tropsch and biodiesel fuels on trade-offs between pollutant emissions and combustion noise in diesel engines

“…The assessment of combustion noise is based on the methodology proposed by Payri et al [27], in which in-cylinder pressure is decomposed into three sub-signals each one characterizing the relevant phenomena taking place during the operation of diesel engines: compressionexpansion (pseudo-motored signal), combustion, and combustion chamber resonance. The compression-expansion signal does not represent any tendency related to combustion and is used to provide a convenient reference.…”

“…In these engines, the self-ignition of premixed fuel causes a rapid pressure rise, producing the well known "knock", which excites the gas in the combustion chamber and consequently induces its oscillation [25,26]. The source of the combustion noise is related to pressure and mechanical forces, which are characterized by in-cylinder pressure, the system response is associated with the vibration of the block wall, and the radiated noise is the final effect of such a vibration [27,28].…”

Bayesian models for the determination of resonant frequencies in a DI diesel engine

“…Calculating the resonant frequency accurately in an engine combustion chamber enables the characterisation of resonant frequencies that are associated with the speed of sound, and hence temperature [3,4,5,6,7]. Therefore, accurate isolation of resonant frequencies and their decay, as a function of time, or crank-angle, will allow the bulk temperature of the gas in the combustion chamber to be determined at any point within the region of interest.…”

Estudio CFD de la resonancia en la cámara de combustión de Motores Diesel HDI

“…Está técnica de descomposición ha sido utilizada, aplicada y validada experimentalmente por Payri [129]. La idea principal consiste en separar la señal de presión en dos sub-señales, pseudo-arrastre y sobre-presión.…”

“…Esto, junto con la medida de ruido emitido a un metro del motor, permite correlar los efectos de las condiciones de funcionamiento del motor sobre el comportamiento termodinámico del gas y el ruido emitido [187,189]. Payri et al [129] proponen una metodología para la predicción de la calidad sonora del motor, a partir de parámetros provenientes de la señal de presión en el interior del cilindro como la derivada máxima de presión y la energía de resonancia. Estos estudios han demostrado la importancia de las condiciones de operación y carga del motor sobre la resonancia y la importancia deésta sobre la calidad acústica del motor.…”