Noise of Diesel Engines Under Transient Conditions

Combustion noise radiation during the acceleration of a turbocharged diesel engine operating with biodiesel or n-butanol diesel fuel blends

“…The main mechanism behind the increase in combustion noise radiation during transients compared with the respective steady-state operation lies in the operating principles of a transient event. 4,17 In the first few cycles after acceleration, such as those demonstrated in Figures 7 and 10, the injected fuel quantity has already increased substantially, cooling the chargeair temperature; however, the cylinder wall temperature is still low (up to 100°C lower than the corresponding steady-state conditions 13 ), as the 100 1,000 10,000 thermal transient proceeds at a much slower rate owing to the (generally) high cylinder wall thermal inertia. Moreover, the rapid increase in the fuel injection pressure upon the onset of each instantaneous transient causes penetration of the liquid fuel jet within the combustion chamber to increase.…”

“…11 Combustion noise development during a transient event differs to a large extent from that in the respective steady-state operation; this was the result reached by the surprisingly few studies carried out so far. [12][13][14][15][16][17] The main finding made by Head and Wake 13 was that combustion noise is generally higher during acceleration, typically of the order of 4-7 dBA, compared with the respective steady-state conditions of a naturally aspirated engine. They argued that this increase was mainly due to the lower cylinder wall temperature during the first few cycles of the transient event, which lowered the evaporation rate and increased the ignition delay period.…”

Development of combustion instability and noise during starting of a truck turbocharged diesel engine

“…Combustion noise development during a transient event differs to a large extent from the respective steady-state operation; this was the result reached by the surprisingly few studies carried out so far (Watanabe et al, 1979;Head and Wake, 1980;Dhaenens et al, 2001, Shu andWei, 2007), mainly for naturally aspirated diesel engines. During steady-state operation, engine speed and fuelling remain practically constant; under transient conditions, however, the engine speed changes continuously, following the forced changes in fuelling.…”