Theoretical and experimental study on sequentially turbocharged diesel engine performance.
An investigation on the sequential turbocharging of a Kelvin TFSC6 6-cylinder 4-
stroke marine diesel engine developing 320 kW at 1200 r/min is reported in this thesis.
The sequential turbocharging (ST) system, utilising turbochargers of unequal size,
resulted in significant improvement when compared with previously designed systems.
The engine test results show that the new sequential turbocharging system improves
the engine performance at both high speeds and low speeds except at or near to the
'transfer' speed. The engine low speed performance is obviously improved with the
fuel saving of up to 7 g/kwh for the 1st sequence. The engine high speed performance
is also improved for the 2nd sequence where both turbochargers are in operation.
There is some boost air leakage from the delivery pipe which is used for connecting the
peak unit to the intercooler inlet. This restricts the 2nd sequence gains. An optimised
sequence transfer control mode is also proposed in this research and validated by both
test and simulation results. Two control valves, one at the peak unit turbine inlet and
the other at the compressor outlet, are specifically designed for the ST system and both
of them worked very well during the engine test programme.
Both simulation models - "Filling& Emptying" and "Method of Characteristic" were
modified and used for the sequential turbocharging simulation. The modified program
of the "Filling& Emptying" model can be used to analyse and compare the effects of
different exhaust systems. It can also be applied to simulate and design a pulse
converter system for a sequential turbocharged diesel engine. The modification on the
"MOC" program makes it possible to simulate the exhaust pressure wave for the ST
system with different turbocharger arrangements (concentrated or separated). The
consideration of pressure losses in the 'three branch junction' boundary improves the
In addition, a comprehensive engine test data acquisition and control system has been
developed in this study. The advanced system with many new features can be used for
engine condition monitoring. diagnosis and other similar applications for engine
development and test. The efficiency and reliability of the system have been
corroborated by the engine test process. The real time data process, analysis and
display in various forms are available using the developed program with 'LabVIEW'.
The proposed self-adaptive auto-load setting with optimised parameters is validated as
an economic solution for engine load control with an early type of hydraulic