Sound quality assessment of Diesel combustion noise using in-cylinder pressure components

Abstract

The combustion process in direct injection (DI) Diesel engines is an important source of noise, and it is thus the main reason why end-users could be reluctant to drive vehicles powered with this type of engine. This means that the great potential of Diesel engines for environment preservation—due to their lower consumption and the subsequent reduction of CO2 emissions—may be lost. Moreover, the advanced combustion concepts—e.g. the HCCI (homogeneous charge compression ignition)—developed to comply with forthcoming emissions legislation, while maintaining the efficiency of current engines, are expected to be noisier because they are characterized by a higher amount of premixed combustion. For this reason many efforts have been dedicated by car manufacturers in recent years to reduce the overall level and improve the sound quality of engine noise. Evaluation procedures are required, both for noise levels and sound quality, that may be integrated in the global engine development process in a timely and cost-effective manner. In previous published work, the authors proposed a novel method for the assessment of engine noise level. A similar procedure is applied in this paper to demonstrate the suitability of combustion indicators for the evaluation of engine noise quality. These indicators, which are representative of the peak velocity of fuel burning and the resonance in the combustion chamber, are well correlated with the combustion noise mark obtained from jury testing. Quite good accuracy in the prediction of the engine noise quality has been obtained with the definition of a two-component regression, which also permits the identification of the combustion process features related to the resulting noise quality, so that corrective actions may be proposed.

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

“…This decomposition technique was previously applied to the analysis of cause-effect relations between the source (caused by combustion) and both the objective and subjective aspects of noise [23,24]. In this investigation, the procedure proposed by Payri et al, was used to predict the sound quality of the combustion noise, which is quantified by a mark as would be given by a jury during a listening test as is described in [23]. According to this procedure, the mark is highly correlated with two combustion indicators.…”

“…Despite these efforts, current designs are still too noisy, specially during transient operation [21] and new combustion concepts such as the PCCI [22]. While the control of the overall noise is imperative to fulfill the current legislation, sound quality and comfort are essential for the customer purchasing decision [23,24]. The external sound field of diesel engines comprises the contribution of both combustion and mechanical noise.…”

“…With this purpose, different biodiesel blends and a synthetic fuel were tested in a lightduty direct injection (DI) diesel engine at different operating conditions. A procedure based on the decomposition of the in-cylinder pressure signal was used in order to evaluate the subjective aspect of combustion noise [23].…”

Sensitivity of combustion noise and NOx and soot emissions to pilot injection in PCCI Diesel engines

“…For this purpose, a light-duty Diesel engine was adapted to operate under the PCCI combustion concept, taking into account the operating conditions in which this concept becomes more suitable for reducing NO x and soot. A novel methodology based on the decomposition of the in-cylinder pressure signal was used to assess subjective and objective aspects of combustion noise [14,15].…”

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

“…Por una parte, Payri [128] relaciona dos indicadores provenientes de la señal de presión en el cilindro (I 1 e I 2 ) con el ruido subjetivo evaluado por un jurado de expertos, mediante una Nota (ver ecuación 2.4.1.2). Esta Nota se obtiene del análisis de ruido del motor, medido previamente con un torso binaural ubicado a 1 m del bloque del motor.…”