Tesis doctoral de Luca Monelletta
Despite their important advantages in terms of fuel consumption in comparison with gasoline engines, for a long time the characteristic impulsive combustion noise has been one of the main causes why customers are reluctant to buy cars equipped with diesel engines. This is the main reason for the efforts devoted by car manufacturers to mitigate diesel engine noise while improving performance and driveability. In spite of all technical improvements, vehicles equipped with high speed direct injection (hsdi) engines still offer a comfort level inferior to gasoline engine vehicles. noise represents one of the most important aspects in the definition of comfort, and especially combustion noise plays an essential role in the acoustic of a vehicle as, in the case of di engines, it represents one of the most important noise sources. Thus, the great potential of diesel engines for environment preservation — due to their lower co2 emissions — could be missed. This situation worsens with the current design trends (engine downsizing) and the emerging new diesel combustion concepts (homogeneous charge compression ignition-hcci, premixed charge compression ignition-pcci, etc.) Conceived to further reduce nox and particulate matter to comply with forthcoming legislation, which are intrinsically noisy. therefore, combustion noise must be considered as an additional essential factor in engine development, together with performance, emissions and driveability. Thus, suitable evaluation procedures that can be integrated into the global engine development process in a timely and cost-effective manner are imperative, both for noise level and sound quality. In this thesis, a procedure, based on the consideration of suitable indicators extracted from in-cylinder pressure, is proposed and validated. Such indicators are obtained from an innovative procedure to decompose in-cylinder pressure signal, so that features associated with combustion and with resonance excitation may be properly identified. Indicators obtained were correlated with a mark characteristic of the quality as well as with the overall noise level. In the first case, a direct physical explanation of subjective issues is not forthcoming but significant correlations were obtained and it was possible to obtain guidelines for the design of engines with a higher sound quality. In the second case, a prediction of the radiated noise level more accurate than that obtained from the classical block attenuation approach was achieved, while combustion process features related with the resulting noise level can be identified and thus corrective actions could be proposed. in a complex issue, such as the noise radiated by a diesel engine for a wide range of operation conditions, the classical analysis techniques are mainly useful for the evaluation of final products but not in early stages of engine development. The novelty of the approach proposed in this thesis lies in the fact that the signature of the in-cylinder noise source is determined and characterized by reliable combustion indicators that are well correlated with both the sound pressure level and the subjective judgements for the whole operation range of interest. Since in-cylinder pressure traces are available at early stages of engine development, the proposed procedure becomes an attractive tool, that allows the integration of noise issues into the global development process, avoiding the need to resort to long and expensive noise tests.
Datos académicos de la tesis doctoral «Contribution to the study of combustion noise of automotive diesel engines«
- Título de la tesis: Contribution to the study of combustion noise of automotive diesel engines
- Autor: Luca Monelletta
- Universidad: Politécnica de Valencia
- Fecha de lectura de la tesis: 02/07/2010
Dirección y tribunal
- Director de la tesis
- Jaime Alberto Broatch Jacobi
- Tribunal
- Presidente del tribunal: Francisco Payri gonzález
- jordi Romeu garbí (vocal)
- octavio Armas vergel (vocal)
- Juan Jesús Garcia bonito (vocal)