INTERACTION AND COMPATIBILITY BETWEEN PROPULSIVE PLANT AND ENGINE ROOM / DOUBLE BOTTOM STEELWORK

SOME CONSIDERATIONS ABOUT SHIP DESIGN Combination of optimised structure and increased installed power - this is possible due to computer power and extensive Finite Element calculations - high ship performance - better profitability in operating the ship - steel weight is optimised - cost of the ship is optimised Problem of compatibility between propulsive plant and hull is raised

UNDERSTANDING INTERACTION BETWEEN MACHINERY AND HULL How machinery and hull interact ? - reactions on bearings (static and dynamic interactions) - influence of operation conditions (loading conditions, r.p.m.) Compatibility between machinery and hull - bad compatibility damages, vibrations - good compatibility (static and dynamic) is absolutely necessary

GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Correct design of propulsive plant - proper position of bearings - good design of engine room and double bottom steelwork Optimum distribution of bearing reactions - for significant loading conditions - for normal operation conditions (rpm, temperature values of main engine and sea water, sea-swell) Alignment conditions - must be pre-calculated - all significant effects must be anticipated

SPECIFICITIES What happens if aft part is very flexible ? - large structural deformations in engine room between full load and ballast conditions - large structural deformations in engine room due to wave loads What happens in case of high output power ? - line shafting is very stiff (small length and big diameter) - mean values (quasi-static) and fluctuation values (dynamic) of propeller forces and moments are high (or very high)

SOME SPECIFICITIES OF BIG SHIPS (VLCC’s, Big Container Ships,…) Low rpm diesel engine - main engine and crankshaft stiffness are relevant parameters due to specific architecture of main engine Direct coupling between line shafting and crankshaft

ADDITIONAL IMPORTANT PARAMETERS Anti-friction material behaviour - white metal, Railko,... Oil film thickness / stiffness - depends of alignment conditions - depends of rpm (propeller forces and moments) Thermal effects - cold conditions (alignment operations) - hot conditions (ship operation conditions) Sea-swell effects

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Calculations - effects of all relevant parameters must be included in the calculations Measurements - access to specific parameters to be used as input data in the calculations - correlation with calculated values - validation of calculation models

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Recommendations for line shafting design

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Alignment conditions Rational alignment –infinite bearing stiffness Elastic alignment –elastic supports (bearing material, hull structure) –influence of oil film –influence of propeller forces and moments Pressure distribution on bearings Flexibility -anti friction -steel-work -bossing Line shafting model for elastic alignment calculations

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Elastic Alignment Influence of oil film –pressure distribution –reaction distribution –oil film thickness –oil film stiffness (used as input data for calculations of lateral vibrations of line shafting or for global vibration analysis) Variation of contact Squeezing of white metal Distribution of local reactions Maximum pressure on white metal Contact distribution between tail-shaft journal and white metal of aft bush of stern tube simple slope boring double slope boring

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Elastic Alignment Pressure distribution in aft bush as a function of alignment conditions alignment condition 2 alignment condition 1 alignment condition 3 Influence of propeller forces and moments on contact conditions between shaft and bearings Forces Moments

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Rational Alignment (basic)

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Rational Alignment (practical operations)

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Ship A Alignment conditions

Aft bush Forward bush

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience SHIP B Alignment conditions

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience SHIP C Alignment conditions Ballast hot Loaded hot Docking cold Launching cold

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience SHIP D Alignment conditions

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience SHIP D Alignment conditions

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Calculations - effects of all relevant parameters must be included in the calculations Measurements - access to specific parameters to be used as input data in the calculations - correlation with calculated values - validation of calculation models

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Calculations Methodology Finite Element Model n° 1 (Hull + main engine) - pre/post processing: I-DEAS - solver: MSC / NASTRAN - calculations of hull flexibility in way of bearings - calculations of relative deformations of engine room steelwork between ballast and full load conditions - calculations of steel work deformations on waves

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Finite Element Model Finite Element Model n°2 (line shafting and crankshaft)

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Methodology Finite Element Model n° 2 - calculations of line-shafting / crankshaft stiffness in way of bearings - calculation of shaft gravity loads

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Methodology Solving the global problem - specific Bureau Veritas Group in-house developed software - effects of all relevant parameters are included: propeller forces and moments hull deformations and flexibility main engine / crankshaft stiffness oil film effects anti-friction material behaviour clearances rpm, temperature...

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Methodology Output / deliverables - reactions on bearings - line shafting deformations - oil film stiffness to be used as input data in vibration calculations

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Vibration behaviour assessment Analysis of excitations Propeller –propeller forces and moments –hull surface forces Main engine –free forces and moments –lateral moments

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Vibration behaviour assessment Calculation of natural frequencies and mode forms Calculation of response in forced vibrations for determination of vibration level (values of excitations - forces, moments, pressures - are needed)

Displacement, Velocity, Acceleration Adverse comments probable Adverse comments not probable REVOLUTION (rpm) OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Calculations Vibration behaviour assessment

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Our experience Calculations - effects of all relevant parameters must be included in the calculations Measurements - access to specific parameters to be used as input data in the calculations - correlation with calculated values - validation of calculation models

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Measuring sets Sensor SENSORS Recorder Amplifier conditionner Analyser On Site or Laboratory Spot investigations Full investigations

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Measurements Equipment installation on propulsive plant Location of Measuring Points (Propulsive plant) T M5 M6 Mf1 Mf2 Mf3 Mf4 M1 M7 M2 M3 M4 Non Contact transducer D1 D2 D3 D4 Cylinder position Girdercyl. 3/4 J1 J8...to...

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Measurements Equipment installation on ship structure TV LV VV LV TV Location of Measuring Points (Accelerometers) S3 S4 S5 S1 S6 S7 S8 S2 M6 M1 M2 M5 M3 M4

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Measurements Structural deformations Transducer support Influence of quasi static phenomena on actual position of supports: loading conditions sea swell mean thrust Measuring points Reference line piano wire

Experiments OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Experiments OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Experiments OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

N 0 =4 N 0 =6 N 0 =7 2 nd VV 3 nd VV 4 nd VV N 0 =8 RPM Water Falls details OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Experiments OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Measurements Shaft motions Vertical Motion Transverse Motion

OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Measurements Main Engine Crankshaft Orbits M/E crankshaft bearing

Experiments OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Experiments Excitation tests generally during outfitting works Harmonic exciter Hammering tests Natural frequencies, mode shapes Coupling effects Local resonance (proposition of reinforcements) OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL

Torsion meter Torque bridge Measurements of torsion Vibrations at free end directly on the shaft Critical RPM Stresses in the shaft OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Torsion vibrations of shaft and engine

Torque bridge Measurements of Output on shaft directly on the shaft (strain gages) together with torsion measurements OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Power and Torque Measurements

Gage bridge for bending measurements Measurements of bending moments on the shaft line by stress gages Static alignment dynamic alignment Influence of external parameters OBTAINING GOOD COMPATIBILITY BETWEEN MACHINERY AND HULL Shaft Bending Moments Measurements

CONCLUSION Good interaction between propulsive plant and hull is essential - to avoid anti friction material damages - to build vibration-free propulsion plants and ships Target : Optimum distribution of bearing reactions for any operating condition - scientific detailed analysis including all relevant parameters (if possible at early design stage) - experiments will be helpful for ships in service

CONCLUSION Potential consequences of bad interaction between propulsive plant and hull - may be disastrous - are out of proportion in comparison to the costs of the studies Types of assistance - review of documents - calculations and/or experiments Numerous references - for different types of ships - for ships classed in various Classification Societies

INTERACTION AND COMPATIBILITY BETWEEN PROPULSIVE PLANT AND ENGINE ROOM / DOUBLE BOTTOM STEELWORK