Transcript Document

CONTROLLABLE PITCH
PROPELLERS
BY K.V.V.UNNI
The SCHOTTEL Controllable Pitch Propeller –the
reliable
propulsion system for all ships with up to 30,000 kW
SCHOTTEL
Controllable
Pitch
Propeller Systems (SCP) are available
in various designs, including:
• X-type, i.e. hydraulic cylinder
mounted in the propeller hub• Z-type,
i.e. hydraulic cylinder mounted in the
propeller shaftOil is distributed either
via an Oil Distribution (OD) box
mounted in front of the gearbox (Gtype), or via the W-type OD box, which
ismounted in the shafting.
THEREFORE
DIFFERENT
COMBINATIONS
OF
HYDRAULIC CYLINDER ARRANGEMENT AND POSITION
OF OIL SUPPLY CAN BE IMPLEMENTED. THE MOST
COMMON IS THE X-TYPE HUB COMBINED WITH OIL
SUPPLY IN FRONT OF THE GEARBOX,THE SO-CALLED
“XG” CONFIGURATION.
OTHER SOLUTIONS ARE THE “ZG”VERSION, WITH
THE HYDRAULIC CYLINDER IN THE SHAFT AND THE
OD BOX IN FRONT OF THE GEARBOX, AND THE “XW”
VERSION, WITH THE CYLINDER IN THE HUB AND THE
OIL SUPPLY IN THE SHAFT.
THE “X” TYPE INCORPORATES A HYDRAULIC
CYLINDER WITH THE PISTON DIRECTLY CONNECTED
TO THE YOKE. HENCE THE DESIGN IS SIMPLE, WITH A
MINIMUM OF MOVING PARTS, AND ACHIEVES THE
HIGHEST RELIABILITY. TO OBTAIN OPTIMUM
STRENGTH THE HUB IS CAST IN ONE PIECE. THE
PROPELLER BLADES ARE MOUNTED ON LARGE-SIZED
BLADE CARRIERS TO MINIMIZE THE STRESSES IN THE
SYSTEM. THE YOKE MOVING INSIDE THE HUB IS
SUPPORTED BY SLIDING PIECES. CRANK PINS ON THE
YOKE OPERATE THE PROPELLER BLADE CARRIERS,
WHICH HAVE GROOVES GUIDING THE PINS. THE
PROPELLER BLADES ARE BOLTED TO THE CARRIERS.
THE HUB IS SEALED BY A WELL-PROVEN SYSTEM
CONSISTING OF A PRE-LOADED SEALING RING
BETWEEN THE HUB AND THE BLADE FOOT.
The hydraulic oil flows through an inner and
outer oil pipe, both mounted concentrically
inside the hollow-bored shaft. The movable
double oil pipe also functions as a feedback
system indicating the current pitch of the
propeller system. The Z-type hub with the
hydraulic cylinder within the propeller shaft
results in a considerably shorter propeller hub.
The shaft-integrated hydraulic cylinder moves
the yoke by means of a rod leading through the
hollow-bored shaftline. For all systems,
propeller blades and hubs are available made of
Cu-Ni-Al or even stainless steel
CONTROLLABLE PITCH PROPELLERS DESIGNED BY
SCHOTTEL OFFER THE FOLLOWING ADVANTAGES:•
BLOCKING VALVES FOR PITCH SETTING INSTALLED IN
THE CYLINDER SPACE OF THE HUB, EASILY ACCESSIBLE
WHEN DOCKED WITHOUT DISMANTLING OF THE HUB •
BLOCKING VALVES ALLOW OPERATION IN THE AHEAD
CONDITION WITH 100% ENGINE POWER WITHOUT
RESTRICTION • BLADES CAN BE DISMOUNTED IN A
NOZZLE WITHOUT PULLING THE SHAFT • THE BLADE
MOVING PIN IS PART OF THE CAST YOKE, WHICH
ACHIEVES A LARGER CONTROL STROKE NEAR THE END
POSITIONS OF THE BLADES, ALLOWING FINER PITCH
CONTROL. THIS ALSO RESULTS IN LOWER STRESSES IN
THE PIN. • OPTIMUM MATCHING OF MATERIAL BETWEEN
HUB AND BLADE CARRIERS • LARGER HUB IS CAST IN
ONE PIECE, GIVING A RIGID STRUCTURE
DESIGNING A CP PROPELLER BLADE IS A COMPLEX
PROCESS,REQUIRING AN EXTENSIVE RANGE OF EXPERT
KNOWLEDGE IN THE SPECIALIZED FIELDS OF FLUID
PHYSICS AND MECHANICAL ENGINEERING. IN ADDITION
TO HYDRODYNAMIC BLADE DESIGN, THE CALCULATION
OF HYDRODYNAMIC LOADS AND THEIR EFFECTS WHEN
THE BLADE PITCH IS CHANGED AND IN VARIOUS
OPERATING CONDITIONS ARE OF GREAT IMPORTANCE.
IN ORDER TO PROVIDE ADVANCED BLADE SHAPES AND
SATISFY EVER-HEIGHTENED REQUIREMENTS, USE IS
MADE OF STATE-OF-THEART CALCULATION METHODS,
REFINED CONTINUOUSLY BY MEANS OF RESEARCH
PROJECTS CARRIED OUT IN COOPERATION WITH
RESEARCH INSTITUTES.THE BLADE DESIGN IS INITIALLY
EXECUTED THROUGH THE USE OF CIRCULATION THEORY
VERIFICATION AND OPTIMIZATION TECHNIQUES
THE STRENGTH OF THE BLADE IS VERIFIED
THROUGH THE USE OF FEM (FINITE ELEMENT
METHOD), ACHIEVING THE OPTIMUM
COMBINATION OF MECHANICAL EXPEDIENCE
AND HYDRODYNAMIC EFFICIENCY.ALMOST
EVERY PROPELLER UNDERGOES EXTENSIVE
MODEL TESTS, WHERE IT MUST PROVE THAT
IT ACTUALLY POSSESSES THE REQUIRED
CHARACTERISTICS WITH REGARD TO
EFFICIENCY, CAVITATION AND PRESSURE
FLUCTUATIONS.
Here SCHOTTEL employs two tried-andtested methods developed at the HSVA in
Hamburg and the SVA in Potsdam, which are
currently the most powerful programs in
existence. Openwater diagrams, pressure
distribution, cavitation and pressure
fluctuation properties are calculated for all
relevant operating states in the vessel’s
wake.
In addition to close cooperation with
research institutes, SCHOTTEL also draws
on the invaluable years of experience of
leading experts in the field of propeller
design.
The strength of the blade is verified through the use
of FEM (Finite Element Method), achieving the optimum
combination of mechanical expedience and
hydrodynamic efficiency. Almost every propeller
undergoes extensive model tests, where it must
prove that it actually possesses the required
characteristics with regard to efficiency, cavitation
and pressure fluctuations.
In these tests the SCHOTTEL design regularly
competes head-to-head with technology from other
suppliers, and as the results show, SCHOTTEL
produces some of the best propeller designs on the
market.
The pump and motor unit forms an essential
part of the hydraulic system. This assembly
delivers the oil quantity needed for adjustment
of the propeller blades and produces the
pressure required for pitch control. Two
electrically driven pumps (1 active pump, 1
standby pump, each with 100% capacity) are
mounted on the cover of the hydraulic tank,
with the pumps running in the oil
The compact control block, incorporating all the indicators and the
individual instruments necessary for pitch control, is located on the
top of the tank. The piping between the pump and motor unit and
the oil supply unit is part of the shipyard’s scope of supply.
Lubrication oil is fed through the stern tube into the hub.
This system is not connected to the hydraulic system of the
controllable-pitch propeller unit. Optionally a two-pipe system can
be supplied, in which case the hydraulic oil is used to lubricate
The remote control system is designed to
provide automatic control of a SCHOTTEL
controllable pitch ropeller. The system is
based on a microprocessor-controlled
system architecture with 2-wire bus
communication between central unit, ECR
and bridge. An HMI (human-machine
interface) allows clear, user-friendly
control, set-up and maintenance of the
system.The system is type-tested to GL,LRS
and ABS (other classes on request) and
meets class requirements according to
AUT24 and UMS.Standard features
UMS.STANDARD FEATURES:
• CONTROL FROM ECR, BRIDGE AND WINGS
• COMBINATOR AND CONSTANT
SPEED MODE
• UP TO 3 ACCELERATION PROGRAMS
• LOAD CONTROL MANAGEMENT
• AUTOMATIC SLOW DOWN
• AUTOMATIC SHUT DOWN
• SELF MONITORING
• NON-FOLLOW-UP CONTROL FROM ECR AND BRIDGE
• PITCH MEASUREMENT SYSTEM
• M/E INTERFACE :THE SYSTEM IS POWERED WITH 24 V DC.
A SEPARATE SUPPLY SHOULD BE PROVIDED FOR THE BACKUP SYSTEM.OPTIONS:
• ENGINE TELEGRAPH SYSTEMS AND ELECTRIC SHAFT
SYSTEM IN THE WHEELHOUSE AREA
• CLUTCH CONTROL SYSTEM
• INTERFACE FOR DP SYSTEMS
• INTERFACE FOR MANOEUVRING
6 Passenger/Container vessel ZI YU LAN,1 x SCP 1544 XG (15,000
kW)
Shipyard: Aker-MTW, Germany, Owner: Shanghai Shipping
Corporation,PR China
Diameter: it is the diameter of the circle swept across the
extreme tips of the propeller blades. Shaft speed (usually
engine rpm divided by the reduction gear ratio) and SHP
are the factors influencing the diameter. SHP (Shaft Horse
Power) is the power actually delivered from the engine to
the shaft thus to the propeller, about equal to the BHP
(Brake Horse Power, meaning the maximum engine horse
power as tested at the factory) minus about 3% of power
loss at the gearbox and 1.5% per bearing. Generally the
larger the diameter the greater the propeller efficiency
Pitch: it is the distance a propeller drives
forward for each complete revolution,
assuming it is moving trough a solid element,
just like a wood screw does.
For instance, if the propeller cover
100 millimeters per turn through a solid,
then its pitch is 100 millimeters.
There are three main propellers' families:
constant-pitch propellers
folding propellers and controllable-pitch propellers
Constant pitch propellers: this type of
propellers blades are welded to the hub, and
their pitch, as suggested by the name, is fixed.
Their structure is surely the stronger, because
they are manufactured from a single casting,
usually through CAM (Computer Aided
Manufacture) assisted machinery and they
have no moving parts.
Folding propellers: they have folding blades;
under sail the hydrodynamic pressure keeps
them closed, thus considerably reducing drag.
Their astern maneuverability is poor.
Controllable pitch propellers: in this type of
propellers, the user can modify the pitch,
while underway, by mean of a hydraulic
mechanism or a direct mechanical linkage.
Feathering propellers, in particular, are a
special controllable pitch propeller type,
ensuring low drag, because of their
characteristic blade design.
Controllable pitch propellers are very
practical because by modifying the pitch they
allow for thrust optimization under different
load conditions. Most modern sailboats are
fitted with this type of propeller. Lets
discover together how to use it.
FOR THE MAJORITY OF ENGINE AND PROPELLER
MANUFACTURERS THE IDEAL PROPELLER WILL CAUSE A LOSS
OF 5 TO 10% IN ENGINE MAXIMUM REVOLUTION PER
MINUTE; IF, FOR INSTANCE, THE ENGINE RATED MAXIMUM
RPM ARE 3600, THE LOSS WILL APPROXIMATELY BE 200
RPM, IN CALM SEA, WITH NO WIND, WITH NO OVERLOAD ON
BOARD AND WITH A CLEAN HULL BOTTOM, WHILE IT WILL BE
ABOUT 360 RPM IN ROUGH SEA, STRONG WIND ETC...
IF THE TOTAL ACTUAL LOSS IS BIGGER, THEN THE
PROPELLER IS "OVERLOADED" AND SO IS THE ENGINE,
WHILE IF THE PROPELLER IS TURNING TOO FAST IT IS
"UNDER-LOADED" AND IS NOT USING ALL THE ENGINE
POWER. ON THE OTHER HAND SOMEONE BELIEVES THAT
ONE SHOULD KEEP THE PITCH AS LONG AS POSSIBLE IN
ORDER TO ACHIEVE THE CRUSE SPEED AT LOWER AS
POSSIBLE RPM.
For example, lets suppose that a 6 knots cruise speed is
reached at 2800 rpm. Increasing the pitch (and of course
keeping the diameter constant) the same speed could be
registered at 2000 rpm. In this case, advantages are: lower
engine speed, less shaft vibration, less noise thus longer
engine life. The question is: which is the right choice?
THE "HIGH PITCH AND LOW RPM" SOLUTION , ALTHOUGH
APPEARING INTERESTING, IS NOT THE CORRECT ONE. THE
ENGINE IS ACTUALLY RUNNING SLOWLY, BUT IT IS
OVERLOADED THUS LASTING SHORTER, MUCH SHORTER
THAN AN ENGINE RUNNING FASTER BUT WITH LESS "JOB" TO
DO
. This is due to the higher stress concentration on the engine
pistons, crankshaft and bearings, which can lead to some
serious damage such as engine seizing. Having an
"overloaded" engine and propeller is just like someone
driving on a steep mountain road on the fifth gear instead
of the third: the engine is overheated, the speed does not
increase and fuel consumption is higher. On the other hand
the "5 to 10% loss on top rpm" rule will surely not overload
the engine, while it will generate noise and the
transmission gear will be in danger. The propeller will turn
faster, thus increasing shaft and bearings vibrations The
ideal solution is an average of the two and can be obtained
with practical tests
The first thing to do is to find in the owner's manual at
which rpm the engine reaches its maximum power (BHP).
Lets perfectly working injection system. This means, for
instance, that an engine which has lost say, for example,
that the maximum power is obtained at 3600 rpm.
Then we have to check which is the actual rpm reached
by the engine, accelerating in neutral. If a 3700/3750 rpm
are achieved, everything is fine, if not you have to adjust
your revolution counter to that value (in fact, and
normally, an engine should increase, in neutral, 3 to 4%
its maximum rated rpm, because, usually, the
manufacturer takes into account the loss due to the
reduction gear). All this is applicable to all well
maintained engines, and in particular to those with clean
fuel filters and compression will not achieve its top rated
rpm. Once the revolution counter has been verified, we
can start the trial which will allow us to know if and at
what rpm our engine is overloaded.
THE SEA STATE MUST BE CALM, AND NO SAIL SHOULD BE
UP. KEEPING A CONSTANT ROUTE, WE HAVE TO INCREASE
ENGINE SPEED WITH A 200 RPM STEP. WE WILL PLOT, FOR
EACH RPM RANGE, THE BOAT'S SPEED, OBSERVED AT THE
LOG (GPS COULD BE TOO INACCURATE FOR THIS PURPOSE).
SPEED SHOULD INCREASE CONSTANTLY FOR EACH RPM
RANGE. MEANTIME, WE SHOULD CHECK EXHAUST WATER
AND FUMES COLOR, WHICH MUST NOT CHANGE. IF SPEED
DOES NOT INCREASE CONSTANTLY OR DOES NOT INCREASE
AT ALL, THEN THE ENGINE IS OVERLOADED (BE SURE THAT
YOU HAVE NOT REACHED THE HULL SPEED); EXHAUST
FUMES QUANTITY AND WATER COLOR WILL PROOF THE
OVERLOADED ENGINE CONDITION
IN FACT, INCREASING ENGINE LOAD,QUANTITY,
DENSITY AND COLOR OF BOTH EXHAUST FUMES
AND WATER WILL BECOME DARKER AND DARKER,
TILL THEY RICH A BLACK COLOR, MEANING
PITCH IS TOO LONG. IN THIS SITUATION,
INCREASING RPM WILL NOT INCREASE SPEED,
SOME OF THE FUEL WILL NOT BE BURNED AND
FUEL CONSUMPTION WILL INCREASE WITHOUT
BENEFITS THE SAME TEST SHOULD BE CARRIED
OUT WITH ROUGH SEA AND WIND AND THE
RESULTS PLOTTED; THESE WILL INDICATE IF
YOUR PROPELLER'S PITCH IS CORRECT OR IF
IT SHOULD BE INCREASED OR DECREASED
THEN LETS CHECK AGAIN THE ENGINÈS
OWNER MANUAL, WHERE WE WILL FIND
THE MAXIMUM HORSEPOWER OUTPUT
AND THE HP/RPM RATIO. LETS, NOW, FIND
THE BEST HP/RPM RATIO. WE WILL ASSUME
OUR ENGINE WILL DELIVER THE
MAXIMUM HORSEPOWER OUTPUT AT 3600
RPM, AND THAT A 2 HP POWER INCREASE
IS ATTAINED FOR EVERY 500 RPM TILL 2800
RPM, THEN 1.5 HP TILL 3200 RPM AND THEN
1 HP TILL 3600 RPM. THE BEST HP/RPM
RATIO IS AT 2800 RPM
We know that cruise engine speed is 20% less
than its maximum speed (3600 rpm): the closest
we go to this value the better is our propeller pitch.
For instance, if our engine has its maximum
efficiency at 2800 rpm and its maximum full ahead
rpm are respectively 3500 in calm sea and 3300 in
rough sea, than our pitch is correct (3500 rpm
minus 20% equals to 2800 rpm). This is true if our
test result confirm that the engine has not been
overloaded in the 0 to 2800 rpm range, otherwise
the pitch has to be reduced
Design System
Propellers are designed with the most suitable method
satisfy the needs of each ship operation.
The methods include applying conventional planning
methods based on systematic model-testing of the series
of propellers, utilizing various databases, and analyzing
the propeller's efficiency and characteristics computed by
propeller theoretical calculation. In particular, the
Propeller Characteristic Analysis Method, employing Nonlinear Lifting Surface Theory supported by the Vortex
Lattice Method (VLM), estimates propeller characteristics
with pure logic based on the difference of blade profile
and blade section, and the variation of working condition
Thus, we immediately can obtain the effect of propeller
characteristic, and its performance according to different
environments.All the information thus gained is applied
to our designing work to pursue efficiency
Analytical System
Using various analytical software programs including
the Finite Element Method, Kamome Propellers
undergo strength analysis if need be, to establish the
efficiency, characteristics, and strength at the most
suitable states.We also use three-dimensional CAD to
examine the best form of section and in establishing
numerical data of the section and utilize the
collected information for development of product
with precise quality.
Manufacturing System
KAMOME'S CAM (BLADE
PROCESSING SYSTEM) IS
INTEGRATED WITH A CAD SYSTEM.
TWO INSTALLATIONS OF
SIMULTANEOUS FIVE-AXES NC
BLADE MILLING MACHINE THAT
PROCESS CPP AND FPP
RESPECTIVELY TO THE MOST
SUITABLE STATE CAN PROVIDE
ACCURATE PROCESSING. NOT
LIMITING THE PROCESSING, THE
PROPELLER'S OPTIMUM FORM
DECISION CAN BE VERY
FLEXIBLE.ALL MANUUFACTURING
DATA IS STORED IN OUR DATABASE,
AND BECOME AVAILABLE AT THE
TIME OF REPRODUCTION
SYSTEM OPERATION
IN CASE OF FAILURE IN THE
OPERATION OF THE
SYSTEMPNEUMATICALLY FROM
THE CO2 ROOM GO TO THE CO2
ROOM
1.
REMOVE SAFETY PIN
FROM PRESSURE/MANUAL
ACTUATOR ON RELEVANT
CYLINDER VALVES
2.
OPEN RELEVANT MAIN
VALVE BY HAND
PULL DOWN THE LEVER ON
E
GO TO THE MASTER CONTROL CABINATE
LOCATED AT CO2 ROOM OR FIRE CONTROL
STATION
1.
KEY BOX
1) BREAK GLASS
2) TAKE THE KEY
2.
OPEN THIS DOOR
3.
ENSURE ALL PERSONNEL HAVE
EVACUATED THE PROTECTED SPACE
4.
CLOSE DOORS AND HATCHES
5.
OPEN ONE CYLINDER VALVE
6.
OPEN VALVE No1 & No2
7.
SYSTEM WILL RELEASE CO2 AFTER A
TIME DELAY OF 30 SECS IF NOT FOLLOW
EMERGENCY OPERATION ON INSTRUCTION
CHART
PRESSURE/MANUAL ACTUATORS BY HAND
AFTER DISCHARGE
1.
ALLOW ENOUGH TIME FOR
THE CO2 GAS TO EXTINGUISH THE
FIRE
2.
DO NOT REOPEN THE
SPACE UNTILL ALL REASONABLE
PRECAUTIONS HAVE BEEN TAKEN
TO ASCERTAIN THE FIRE IS OUT
3.
WHEN THE FIRE IS OUT,
VENTILATE THE SPACE
THOROUGHLY
PERSONS RE-ENTERING THE
SPACE MUST WEAR COMPRESSED
AIR BREATHING APPARATUS
UNTIL THE ATMOSPHERE HAS
BEEN CHECKED AND FOUND TO
NOW SYSTEM IS OPERATED
CONTAIN 21% OXYGEN CONTENT