Large turbochargers for marine diesel engine application have as a rule been driven by the axial-flow turbine with fixed pitch nozzles, with consequent disadvantage, especially in constant pressure turbocharging, of being poor in part-load performance and in acceleration in the low-load range.
Developed by Mitsubishi Heavy Industries, Ltd. this time to remedy this disadvantage is a MET-SR-VG turbocharger, which is driven by the radial-flow turbine with variable-pitch, or variable-geometry (VG), nozzles.
The radial-flow turbine employed is of new design specifically devised for the SR-VG turbocharger application and thus can cover the same output -range as the conventional large-size axial-flow turbine.
A MET33SR-VG turbocharger, prototype machine of the SR-VG design manufactured in 1986, was tested for matching with an actual diesel engine on shore and then put through a series of various kinds of test aboard a seagoing ship, with highly successfully results as expected. Also, in 1987, a MET66SR-VG machine, the first production unit and then the largest to be manufactured, was completed for installation on an 8UEC75LSII, which itself was also the first production engine of Mitsubishi UEC75LSII design built for VLCC application. Commissioned in service in April 1988, the 66SR-VG machine has since been in successful operation.
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