Importance

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Abstract

A diesel engine comprises a plurality of cylinders (2), an inlet duct (4), an exhaust duct (6), a turbocharger (8, 10) and a supercharger (14), the turbocharger being of variable output type and including a turbine (8) in the exhaust duct (6) and a supercharger (14) being of variable output type and situated in the inlet duct (4) between the compressor wheel (10) and the cylinders and being electrically driven or mechanically driven by the engine. The engine also includes a first sensor (25) arranged to produce a signal indicative of the speed of the engine, a second sensor (27) arranged to produce a signal indicative of the load to which the engine is subjected and a third sensor (26) arranged to produce a signal indicative of the pressure in the inlet duct (4) downstream of the supercharger (14). The sensors (25, 27, 26) are connected to a controller (29) which is also connected to the turbocharger and the supercharger and is arranged to vary their output independently. The controller (29) is programmed to determine the desired value of the pressure in the inlet duct (4) downstream of the supercharger (14) and to compare this with the actual value of the pressure and, in the event of there being a difference, to adjust the output of the supercharger and/or turbocharger until there is substantially no difference. The controller (29) is also programmed, if a higher pressure is required in the inlet duct (4), to preferentially increase the output of the turbocharger, subject to the pressure in the exhaust duct (6) not exceeding a predetermined value and, if a lower pressure is required in the inlet duct, preferentially to decrease the output of the supercharger.

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