TECHNICAL FIELD
The present invention relates to marine diesel engines, and particularly to a marine diesel engine equipped with a plurality of turbochargers for pressurizing supplied air by means of exhaust gas.
BACKGROUND ART
Merchant ships sometimes sail in a sailing mode at a
speed lower than a normal service speed to reduce the fuel
consumption of the main engine or to adjust the sailing
schedule. In such cases, the ship needs to sail with a main
engine load lower than a normal sailing load, although it is
difficult to achieve the optimum turbocharger efficiency over
a wide range of main engine loads if a single normal
turbocharger is installed. Accordingly, if a plurality of
turbochargers are installed and the number of those in
operation is controlled, the optimum turbocharger efficiency
can be achieved over a wide range of main engine loads so that
the fuel consumption can be reduced as compared with the case
of a single normal turbocharger, thus contributing to an
improvement in the sailing profitability of merchant ships and
a reduction in the environmental load. A known example of such
a marine diesel engine equipped with a plurality of
turbochargers is the one disclosed in Patent Citation 1.
Patent Citation 1: Japanese Unexamined Patent
Application, Publication No. SHO-60-166716
DISCLOSURE OF INVENTION
The marine diesel engine disclosed in Patent Citation 1 above, however, has a problem in that, when a valve b is opened upon starting of a No. 2 turbocharger 2, backflow occurs from a blower 1B of a No. 1 turbocharger 1
(specifically, a scavenging chamber 3) to a blower 2B of the No. 2 turbocharger 2, thus impairing smooth rotation
(starting) of the No. 2 turbocharger 2 and causing surging in
the No. 2 turbocharger 2.
An object of the present invention, which has been made
in light of the above circumstances, is to provide a marine
diesel engine, equipped with a plurality of turbochargers,
that can prevent backflow from a compressor part of a
turbocharger that operates constantly to a compressor part of
a turbocharger to be started or stopped when the turbochargers
are switched from single operation to parallel operation or
from parallel operation to single operation, to smoothly start
or stop the turbocharger to be started or stopped, thus
preventing surging in the turbocharger to be started or
stopped.
To solve the above problem, the present invention employs
the following solutions.
A marine diesel engine according to the present invention
is equipped with an engine body; at least one main exhaust gas
turbine turbocharger that includes a turbine part driven by
means of exhaust gas guided from the engine body and a
compressor part driven by the turbine part to pump outside air
into the engine body and that operates constantly during
operation of the engine body; and at least one auxiliary
exhaust gas turbine turbocharger that includes a turbine part
driven by means of exhaust gas guided from the engine body and
a compressor part driven by the turbine part to pump outside
air into the engine body and that is at a standstill or
operates in parallel with the main exhaust gas turbine
turbocharger during operation of the engine body. The marine
diesel engine includes an exhaust pipe via which an exhaust
manifold mounted on the engine body communicates with the
turbine part of the auxiliary exhaust gas turbine
turbocharger; a turbine inlet valve connected somewhere in the
exhaust pipe; a supply pipe via which the compressor part of
the auxiliary exhaust gas turbine turbocharger communicates
with a supply manifold mounted on the engine body; a check
valve that is connected somewhere in the supply pipe and that
becomes open when the outlet pressure of the compressor part
of the auxiliary exhaust gas turbine turbocharger reaches or
exceeds the pressure of the supply manifold; an air vent pipe
having one end thereof connected somewhere in the supply pipe
between the compressor part of the auxiliary exhaust gas
turbine turbocharger and the check valve; and an air vent
valve connected somewhere in the air vent pipe.
In addition, a method for operating a marine diesel
engine according to the present invention is a method for
operating a marine diesel engine equipped with an engine body;
at least one main exhaust gas turbine turbocharger that
includes a turbine part driven by means of exhaust gas guided
from the engine body and a compressor part driven by the
turbine part to pump outside air into the engine body and that
operates constantly during operation of the engine body; and
at least one auxiliary exhaust gas turbine turbocharger that
includes a turbine part driven by means of exhaust gas guided
from the engine body and a compressor part driven by the
turbine part to pump outside air into the engine body and that
is at a standstill or operates in parallel with the main
exhaust gas turbine turbocharger during operation of the
engine body. The marine diesel engine includes an exhaust pipe
via which an exhaust manifold mounted on the engine body
communicates with the turbine part of the auxiliary exhaust
gas turbine turbocharger; a turbine inlet valve connected
somewhere in the exhaust pipe; a supply pipe via which the
compressor part of the auxiliary exhaust gas turbine
turbocharger communicates with a supply manifold mounted on
the engine body; a check valve that is connected somewhere in
the supply pipe and that becomes open when the outlet pressure
of the compressor part of the auxiliary exhaust gas turbine turbocharger reaches or exceeds the pressure of the supply manifold; an air vent pipe having one end thereof connected somewhere in the supply pipe between the compressor part of the auxiliary exhaust gas turbine turbocharger and the check valve; and an air vent valve connected somewhere in the air vent pipe. The method includes opening the air vent valve in advance, then opening the turbine inlet valve, and gradually closing the air vent valve when starting the auxiliary exhaust gas turbine turbocharger; and gradually opening the air vent valve and then gradually closing the turbine inlet valve when stopping the auxiliary exhaust gas turbine turbocharger.
In the marine diesel engine according to the present invention or the method for operating the marine diesel engine according to the present invention, the check valve disposed in the supply pipe becomes open (fully open) when, for example, the auxiliary exhaust gas turbine turbocharger is started and the outlet pressure of the compressor part of the auxiliary exhaust gas turbine turbocharger reaches or exceeds the pressure of the supply manifold.
This prevents backflow from the supply manifold to the
compressor part of the auxiliary exhaust gas turbine
turbocharger upon starting of the auxiliary exhaust gas
turbine turbocharger to allow the auxiliary exhaust gas
turbine turbocharger to be smoothly rotated (started), thus
preventing surging in the auxiliary exhaust gas turbine turbocharger.
On the other hand, in the marine diesel engine according to the present invention or the method for operating the marine diesel engine according to the present invention, the check valve disposed in the supply pipe becomes closed (fully closed) when, for example, the air vent valve is opened and the outlet pressure of the compressor part of the auxiliary exhaust gas turbine turbocharger falls below the pressure of the supply manifold.
This prevents backflow from the supply manifold to the compressor part of the auxiliary exhaust gas turbine turbocharger upon stopping of the auxiliary exhaust gas turbine turbocharger to allow the auxiliary exhaust gas turbine turbocharger to be smoothly rotated (stopped), thus preventing surging in the auxiliary exhaust gas turbine turbocharger.
The marine diesel engine according to the present
invention provides the advantage of preventing backflow from
the compressor part of the turbocharger that operates
constantly to the compressor part of the turbocharger to be
started or stopped when the turbochargers are switched from
single operation to parallel operation or from parallel
operation to single operation, to smoothly start or stop the
turbocharger to be started or stopped, thus preventing surging
in the turbocharger to be started or stopped.
BRIEF DESCRIPTION OF DRAWINGS
[FIG. 1] Fig. 1 is a schematic configuration diagram of a marine diesel engine according to an embodiment of the present invention.
[FIG. 2] Fig. 2 is a graph for illustrating the operation and advantages of the marine diesel engine according to the present invention.
[FIG. 3] Fig. 3 is a graph for illustrating the operation and advantages of the marine diesel engine according to the present invention.
Best Mode for Carrying Out the Invention
An embodiment of a marine diesel engine according to the present invention will be described below with reference to Figs. 1 to 3.
Fig. 1 is a schematic configuration diagram of the marine diesel engine according to this embodiment, and Figs. 2 and 3 are graphs for illustrating the operation and advantages of the marine diesel engine according to the present invention.
As shown in Fig. 1, a marine diesel engine 1 according to
this embodiment is equipped with a diesel engine body (for
example, a low-speed two-cycle diesel engine) 2, a first
exhaust gas turbine turbocharger (main exhaust gas turbine
turbocharger) 3, and a second exhaust gas turbine turbocharger
(auxiliary exhaust gas turbine turbocharger) 4.
A screw propeller (not shown) is directly or indirectly
attached to a crankshaft (not shown) constituting the diesel
engine body (hereinafter referred to as "engine body") 2 with
a propeller shaft (not shown) therebetween. In addition, the
engine body 2 has cylinder parts 5 composed of cylinder liners
(not shown), cylinder covers (not shown), etc., and pistons
(not shown) coupled to the crankshaft are disposed in the
respective cylinder parts 5. In addition, exhaust ports (not
shown) of the respective cylinder parts 5 are connected to an
exhaust manifold 6, and the exhaust manifold 6 is in turn
connected to the inlet side of a turbine part 3a of the first
exhaust gas turbine turbocharger (hereinafter referred to as
"turbocharger A") 3 via a first exhaust pipe L1 and to the
inlet side of a turbine part 4a of the second exhaust gas
turbine turbocharger (hereinafter referred to as "turbocharger
B") 4 via a second exhaust pipe L2. On the other hand, supply
ports (not shown) of the respective cylinder parts 5 are
connected to a supply manifold 7, and the supply manifold 7 is
in turn connected to a compressor part 3b of the turbocharger
A 3 via a first supply pipe L3 and to a compressor part 4b of
the turbocharger B 4 via a second supply pipe L4.
The turbocharger A 3 is constituted mainly by the turbine
part 3a, which is driven by means of exhaust gas (combustion
gas) guided from the engine body 2 through the first exhaust pipe LI; the compressor part 3b, which is driven by the turbine part 3a to pump outside air into the engine body 2; and a casing (not shown) disposed between the turbine part 3a and the compressor part 3b so as to support them.
In addition, a rotating shaft 3c is inserted into the casing with one end protruding to the turbine part 3a side and the other end protruding to the compressor part 3b side. One end of the rotating shaft 3c is attached to a turbine disk
(not shown) of a turbine rotor (not shown) constituting the turbine part 3a, whereas the other end of the rotating shaft 3c is attached to a hub (not shown) of a compressor impeller
(not shown) constituting the compressor part 3b.
The turbocharger B 4 is constituted mainly by the turbine
part 4a, which is driven by means of exhaust gas (combustion
gas) guided from the engine body 2 through the second exhaust
pipe L2; the compressor part 4b, which is driven by the
turbine part 4a to pump outside air into the engine body 2;
and a casing (not shown) disposed between the turbine part 4a
and the compressor part 4b so as to support them.
In addition, a rotating shaft 4c is inserted into the
casing with one end protruding to the turbine part 4a side and
the other end protruding to the compressor part 4b side. One
end of the rotating shaft 4c is attached to a turbine disk
(not shown) of a turbine rotor (not shown) constituting the
turbine part 4a, whereas the other end of the rotating shaft 4c is attached to a hub (not shown) of a compressor impeller (not shown) constituting the compressor part 4b.
The exhaust gas passing through the turbine parts 3a and 4a is guided through exhaust pipes L5 and L6 connected to the outlet sides of the turbine parts 3a and 4a, respectively, to a funnel (not shown) and is then discharged outside the ship.
Mufflers (not shown) are disposed in supply pipes L7 and L8 connected to the inlet sides of the compressor parts 3b and 4b, respectively, so that the outside air passing through the mufflers is guided into the compressor parts 3b and 4b. In addition, air coolers (intercoolers) 8 and 9, surge tanks (not shown), etc. are connected somewhere in the supply pipes L3 and L4 connected to the outlet sides of the compressor parts 3b and 4b so that the outside air passing through the compressor parts 3b and 4b is supplied to the supply manifold 7 of the engine body 2 through the air coolers 8 and 9, the surge tanks, etc.
In the marine diesel engine 1 according to this embodiment, a turbine inlet valve 10 is connected somewhere in the second exhaust pipe L2, a check valve 11 is connected somewhere in the second supply pipe L4 (specifically, the portion of the second supply pipe L4 between the compressor part 4b and the air cooler 9), and an end of an air vent pipe
L9 is connected somewhere in the portion of the second supply
pipe L4 upstream of the check valve 11 (specifically, the portion of the second supply pipe L4 between the compressor part 4b and the check valve 11). The other end of the air vent pipe L9 is connected somewhere in the exhaust pipe L6 or the funnel so that the outside air passing through the air vent pipe L9 is discharged outside the ship together with the exhaust gas. In addition, an air vent valve 12 is connected somewhere in the air vent pipe L9.
The turbine inlet valve 10 and the air vent valve 12 are manually or automatically opened or closed when the single operation mode of the turbocharger A 3 is switched to the parallel operation mode of the turbocharger A 3 and the turbocharger B 4 by starting the turbocharger B 4, or when the parallel operation mode of the turbocharger A 3 and the turbocharger B 4 is switched to the single operation mode of the turbocharger A 3 by stopping the turbocharger B 4.
Specifically, as shown in Fig. 2, when the single
operation mode of the turbocharger A 3 is switched to the
parallel operation mode of the turbocharger A 3 and the
turbocharger B 4 by starting the turbocharger B 4, the turbine
inlet valve 10 is opened (fully opened), and the air vent
valve 12, which had been previously opened, is gradually
closed. As the air vent valve 12 is gradually closed, the
compressor outlet pressures of the turbocharger A 3 and the
turbocharger B 4 rise gradually, and the compressor outlet
pressures of the turbocharger A 3 and the turbocharger B 4 eventually reach a predetermined pressure.
The check valve 11 becomes open (fully open) when the compressor outlet pressure of the turbocharger B 4 reaches or exceeds the pressure of the supply manifold 7 or substantially equals the pressure of the supply manifold 7.
On the other hand, as shown in Fig. 3, when the parallel operation mode of the turbocharger A 3 and the turbocharger B 4 is switched to the single operation mode of the turbocharger A 3 by stopping the turbocharger B 4, the air vent valve 12 is gradually opened (fully opened) until the pressure of the supply manifold 7 exceeds the compressor outlet pressure of the turbocharger B 4 (the outlet pressure of the compressor part 4b), and then the turbine inlet valve 10 is closed. As the turbine inlet valve 10 is closed, the compressor outlet pressure of the turbocharger B 4 decreases gradually to 0 (zero), and the turbocharger B 4 stops.
The check valve 11 becomes closed (fully closed) when the compressor outlet pressure of the turbocharger B 4 falls below the pressure of the supply manifold 7 or becomes a predetermined pressure lower than the pressure of the supply manifold 7.
In the marine diesel engine 1 according to this
embodiment, the check valve 11 disposed in the second supply
pipe L4 becomes open (fully open) when the turbocharger B 4 is
started and the compressor outlet pressure of the turbocharger B 4 (the outlet pressure of the compressor part 4b) reaches or exceeds the pressure of the supply manifold 7 or substantially equals the pressure of the supply manifold 7. That is, upon starting of the turbocharger B 4, the check valve 11 disposed in the second supply pipe L4 becomes open when the pressure difference between the compressor outlet pressure of the turbocharger B 4 and the pressure of the supply manifold 7 disappears or becomes negligible.
This prevents, or significantly reduces, backflow from the supply manifold 7 to the compressor part 4b upon starting of the turbocharger B 4 to allow the turbocharger B 4 (rotating shaft 4c) to be smoothly rotated (started), thus preventing surging in the turbocharger B 4.
In the marine diesel engine 1 according to this
embodiment, on the other hand, the check valve 11 disposed in
the second supply pipe L4 becomes closed (fully closed) when
the air vent valve 12 is opened and the compressor outlet
pressure of the turbocharger B 4 (the outlet pressure of the
compressor part 4b) falls below the pressure of the supply
manifold 7 or becomes a predetermined pressure lower than the
pressure of the supply manifold 7. That is, upon stopping of
the turbocharger B 4, the check valve 11 disposed in the
second supply pipe L4 becomes closed when the pressure
difference between the compressor outlet pressure of the
turbocharger B 4 and the pressure of the supply manifold 7 exceeds a predetermined pressure.
This prevents, or significantly reduces, backflow from the supply manifold 7 to the compressor part 4b upon stopping of the turbocharger B 4 to allow the turbocharger B 4 (rotating shaft 4c) to be smoothly rotated (stopped), thus preventing surging in the turbocharger B 4.
Whereas the marine diesel engine equipped with one turbocharger A 3 and one turbocharger B 4 has been described in the above embodiment, the present invention is not limited thereto, but can also be applied to a marine diesel engine equipped with two or more turbochargers A 3 and/or two or more turbochargers B 4.

WE CLAIM:
1. A marine diesel engine equipped with:
an engine body;
at least one main exhaust gas turbine turbocharger that includes a turbine part driven by means of exhaust gas guided from the engine body and a compressor part driven by the turbine part to pump outside air into the engine body and that operates constantly during operation of the engine body; and
at least one auxiliary exhaust gas turbine turbocharger that includes a turbine part driven by means of exhaust gas guided from the engine body and a compressor part driven by the turbine part to pump outside air into the engine body and that is at a standstill or operates in parallel with the main exhaust gas turbine turbocharger during operation of the engine body;
the marine diesel engine comprising:
an exhaust pipe via which an exhaust manifold mounted on the engine body communicates with the turbine part of the auxiliary exhaust gas turbine turbocharger;
a turbine inlet valve connected somewhere in the exhaust pipe;
a supply pipe via which the compressor part of the
auxiliary exhaust gas turbine turbocharger communicates with a
supply manifold mounted on the engine body;
a check valve that is connected somewhere in the supply
pipe and that becomes open when the outlet pressure of the compressor part of the auxiliary exhaust gas turbine turbocharger reaches or exceeds the pressure of the supply-manifold;
an air vent pipe having one end thereof connected somewhere in the supply pipe between the compressor part of the auxiliary exhaust gas turbine turbocharger and the check valve; and
an air vent valve connected somewhere in the air vent pipe.
2. A method for operating a marine diesel engine equipped with:
an engine body;
at least one main exhaust gas turbine turbocharger that includes a turbine part driven by means of exhaust gas guided from the engine body and a compressor part driven by the turbine part to pump outside air into the engine body and that operates constantly during operation of the engine body; and
at least one auxiliary exhaust gas turbine turbocharger
that includes a turbine part driven by means of exhaust gas
guided from the engine body and a compressor part driven by
the turbine part to pump outside air into the engine body and
that is at a standstill or operates in parallel with the main
exhaust gas turbine turbocharger during operation of the
engine body;
wherein the marine diesel engine includes:
an exhaust pipe via which an exhaust manifold mounted on the engine body communicates with the turbine part of the auxiliary exhaust gas turbine turbocharger;
a turbine inlet valve connected somewhere in the exhaust pipe;
a supply pipe via which the compressor part of the auxiliary exhaust gas turbine turbocharger communicates with a supply manifold mounted on the engine body;
a check valve that is connected somewhere in the supply pipe and that becomes open when the outlet pressure of the compressor part of the auxiliary exhaust gas turbine turbocharger reaches or exceeds the pressure of the supply manifold;
an air vent pipe having one end thereof connected somewhere in the supply pipe between the compressor part of the auxiliary exhaust gas turbine turbocharger and the check valve; and
an air vent valve connected somewhere in the air vent pipe;
the method comprising:
opening the air vent valve in advance, then opening the
turbine inlet valve, and gradually closing the air vent valve
when starting the auxiliary exhaust gas turbine turbocharger;
and
gradually opening the air vent valve and then closing the turbine inlet valve when stopping the auxiliary exhaust gas turbine turbocharger.
3. A marine diesel engine substantially as herein described with reference to and as illustrated by the accompanying figures.
4. A method for operating a marine diesel engine substantially as herein described with reference to and as illustrated by the accompanying figures.