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is calculated by Dent’s formula, whose input is spray penetration
experimentally linked with engine out emission. In order to verify
the concept of converted injection pressure, two different engines
are analysed in this study. At first, a natural aspirated engine with
a common rail injection system with a maximum of 1,600 bar is
applied for building soot and NOx estimation models. In this engine
test, a wide range of emission data is obtained under the various
conditions of excess air ratio and pressure difference between
injection and in-cylinder gas. The result shows good relationship
between converted injection pressure and measured soot. Using
this relationship, a soot estimation model can be built and proposed.
In terms of NOx, it has a good relationship with injection
duration. An NOx estimation model has also been built based on
injection duration. Next, a turbo charged engine with maximum
2,000 bar injection common rail system is applied for evaluating
this soot and NOx estimation model. It is found that relative
changes of measured emissions follow estimated results. But there
is a gap in their absolute value because of different combustion
chamber shape and direction of nozzle hole axis. Thus, it is found
that proposed soot and NOx estimation model is only effective
for their relative change against increase in injection pressure. At
last, a trend of the optimal nozzle dimensions accompanied with
increase in injection pressure is calculated by using soot and NOx
estimation models. The result shows that a higher injection pressure
requires a larger number of nozzle holes and a smaller nozzle
hole diameter.
Development trend and optimised matching of fuel
injection system of diesel engine
Zongying Gao, Jiangsu University, China
Bifeng Yin, Jiangsu University, China
Shengji Liu, Jiangsu University, China
Jianming Zhu, FAW Wuxi Fuel Injection Equipment Research Institute, China
Yusheng Ju, FAW Wuxi Fuel Injection Equipment Research Institute, China
Yong Hang, FAW Wuxi Fuel Injection Equipment Research Institute, China
In the foreseeable future – though the dominating source of power
– diesel engines are required to meet the increasingly stringent
regulations of energy conservation and ultra-low emission. As
the heart of diesel engines, the fuel-injection system is the core of
various advanced combustion and emission control technologies
of differently typed engines. As a consequence, the fuel-injection
system tends to be with higher injection pressure and be flexible
as well as controllable, and of which the electronic control high
pressure common rail is considered to be the most potential fuel
system. The common rail fuel injection system marked FCRS has
been developed by The Wuxi Fuel Injection Equipment Institute,
which belongs to The China FAW Group Corporation, and can
provide a injection pressure of 180 MPa and achieve stable injection
more than three times. It has already been applied to heavyduty
diesel engines for vehicles and large-sized non-road diesel
engines as well. The optimal match between the fuel injection
system and the entire engine is the key in the developing process
of diesel engines, which depends on the specifying and collaborative
optimising and matching the properties in the aspects of time
and space in order to obtain an effective and reasonable combustion
process. Time matching needs to ensure that the fuel injection
quantity meet the torque demand for different operating conditions
of the diesel engine. In addition, the injection timing needs
to be precise, stable and adjustable with the load and the speed,
and the fuel injection duration must be appropriate. The injection
pressure and injection rate should be high enough so that full use
of the injection energy to boost the forming and combustion of
the gas mixture can be made. The combination property can be
improved for the emission of NOx and PM can be controlled by
multi-injection and shape control of injection law whose character
is quick after slow. Space matching of fuel system means the match
between the spray and the space of the combustion chamber, and
mixture of fuel and air can realise uniform mixing and complete
combustion through a optimisation design of point of fall of statical
fuel injection line on the wall of the combustion chamber. As
for two-valve DI diesel engines, limited by the structure and the
bulk of the combustion chamber, the influence of space matching
on the combustion process is more obvious. Based on a serial
CFD calculation and high-speed photography inside the chamber,
put forward the design standard for statical fuel injection line distributed
in the axial direction with equal proportion and in the
circumferential direction with equal air-fuel ratio, which can trace
back to the idea that get a better mixture of fuel and air and make
sure a equal air-fuel ratio, lack of neither oxygen nor fuel, in any
place of the chamber.
Monday May 13th / 13:30 – 15:00
Tribology 1
Room D
The benefit of using Group II base oils in mediumspeed
engines
Laura Gregory, Infineum, UK
Group II base oils are a category of base oils defined by the
American Petroleum Institute as having a sulphur content less
than 300 ppm, a saturates content greater than 90% and a viscosity
index of between 80 and 120. Group II base oils have been
used in automotive lubricants for many years. This was driven
by the need to improve performance of the lubricant to meet
the demands of new engine technologies. As a consequence, the
supply of Group II base oil has been increasing and the capacity
of Group I base oil is forecast to decrease. So far, these trends
in base oil capacity have left the lubricants for medium-speed
marine engines unaffected; such lubricants have historically always
used Group I base oils as the diluent for the additive system.
With an increasing availability of Group II base oils, there
is now a drive to utilise them for medium-speed marine engine
applications. The current economic climate is a strong motivator
for the shipowner/operator to scrutinise their operation and
identify where further cost savings can be made. Hence there is a
desire for reduced oil consumption and increased power output.
Combine this with increasingly poor heavy fuel oil quality, to
which medium-speed engines are sensitive, and it becomes clear
that the demands on the lubricant are increasing. This paper discusses
whether the use of Group II base oil can go some way
to meeting those demands, by providing improved oxidation
resistance, viscosity control and lower volatility. An upgrade of
these performance features would extend the time before condemning
limits for the oil are reached. The capability of these
base oils in comparison to Group I is examined in bench and
laboratory engine testing. The deployment of a Group II based
lubricant in the field, and what benefits have been observed, is
discussed.
Cylinder liner and piston ring lubrication issues in
relation to increase stroke/bore ratio
Shinichi Miyake, Mitsui Engineering and Shipbuilding Co, Ltd, Japan
Kazuo Harada, Mitsui Engineering and Shipbuilding Co, Ltd, Japan
Mikio Kotake, Mitsui Engineering and Shipbuilding Co, Ltd, Japan
Christian Lotz Felder, MAN Diesel & Turbo SE, Denmark
Jesper Weis Fogh, MAN Diesel & Turbo SE, Denmark
May 2013 | Schiff&Hafen | Ship&Offshore SPECIAL 9