Topology Optimization of Components for Large Diesel Engines CONTACT INFORMATION Henrik Bisgaard Clausen MAN Diesel A/S DK-2450 Copenhagen SV Tel.: +45 3385 2928 e-mail:
[email protected]
ABSTRACT MAN Diesel is the designer of large diesel engines used for propulsion of ships and stationary power plants. On engines of this size, even a small reduction of the weight of a main component will influence the production cost favourably, and in this presentation, this is exemplified with the cylinder frame and the crosshead shoes. The cylinder frame connects the cylinder liner on top of the engine with the lower structure, and it is furthermore the supporting structure for the scavenge air receiver and the turbochargers. Consequently, the cylinder frame is subject to numerous loads, must have suitable interfaces for neighbouring components and must be airtight. Furthermore, constraints related to casting apply. Traditional empirical design evolution combined with verification by direct calculations and measurements has until now provided sound designs. However, to create a more efficient structure to transfer the forces from the cylinder to the lower structure, topology optimization is applied. A design based on the optimization for an 80 cm bore engine is some 2 tonnes per cylinder or 15% lighter than the original design.
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Topology Optimization of Components for Large Diesel Engines Presented by Henrik Bisgaard Clausen, Ph.D. New Design Department, Research & Development MAN Diesel A/S EHTC, October 2007, BERLIN
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MAN Group Globally active supplier of vehicles, engines and machinery Approx. €13 billion in sales, nearly 50,000 employees in 120 countries Four leading business areas Commercial Vehicles Trucks Engines
Buses Services
Diesel Engines 2-stroke 4-stroke CP-propellers Turbochargers Services
Turbomachinery Compressors Reactors
3334857.2007.04.16
(GMC/PDP)
Industrial Services Contracting Logistics Service platform
Turbines Services
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MAN Diesel Group Locations in Europe Employees worldwide: 6,400 Great Britain
Denmark
MAN Diesel Ltd. Service
Frederikshavn
Copenhagen
MAN Diesel A/S Service, two- and four-stroke engines, propellers
Holeby Stockport Rostock Hamburg
Colchester
Villepinte/Paris
France MAN Diesel SA Service, four-stroke engines
Augsburg Saint-Nazaire
Czech Republic
Velká Bìteš
PBS Turbo s.r.o. Turbocharger
Jouet
Germany Status: 12/05
MAN Diesel SE Service, four-stroke engines, turbocharger
3334870.2007.04.16
(GMC/PDP)
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Market Shares Worldwide Marine Diesel Engines Low-speed diesel engines
Medium-speed diesel engines
for ships ordered in 2006 (Jan.-Sept.)
Orders June 2005 to May 2006
Diesel Engines
34%
87%
77%
9%
66%
4%
MAN Diesel Wärtsila Mitsubishi
MAN Diesel Competitors (Wärtsila, Cat/MaK)
Source:: Lloyd`s Register – Fairplay Ltd.
Source: Diesel and Gas Turbine, Prop. and aux. engines > 0.5 MW
3334951.2007.06.13
(GK/MM)
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The Product Large Two-Stroke Diesel Engines
10K98MC-C and 6S35MC on testbed
2005.10.04
(JLH/2411)
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The Product Two-stroke Crosshead Turbo charged Low speed, 61-167 RPM Large bore from 35 cm to 108 cm Stroke up to 3.45 m Up to 14 cylinders Engines range from 5.900 to 132.000 BHP Up to 2800 tonnes Continuous demand for cost reduction Reliability is crucial
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Component Details The Cylinder Frame
Transfers gas forces from cylinder liner above to engine frame below
Interfaces cylinder liner engine main frame stuffing box scavenge air receiver air cooler turbo charger cam shaft/actuators
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Original Design 80 cm bore engines:
2.16 m heigh 1.33 m wide 2.03 m deep 13.8 t grey cast iron Features thick top plate and thin walls
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Stress Evaluation of Cylinder Frame Standard stress evaluation Gas forces acting in cylinders Cylinders
Transverse forces on guide planes
Reactions forces in main bearings A model of the complete engine is
Guide planes
needed
Main bearings
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Modelling
Non-design elements
Superelement
Design elements Complete element model
Retained elements © MAN Diesel A/S
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Problem Definition Produce a design that Minimizes weight and thus production cost
Observing the following constraints Fatigue strength of cast iron Each cylinder frame possesses two-plane symmetry Final design be valid at any cylinder position Subjected to multiple loads steps (one revolution)
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Optimisation iterations
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Final Topology Design
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Stresses
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Postprocessing & Interpretation Principle derived from optimisation: transfers loads directly from cylinder liner to triangular guide brackets below
Structure needed in central parts rather than at top plate
Furthermore: Must be air tight Must be producible Must be easy to inspect after production
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New Design and Fatigue Evaluation
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Potential Weight Reduction
15% weight reduction
Original
New
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Another Optimisation Study Parameters Controlling the Result Crosshead guide shoes
Mass: 83 kg
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Modelling
Non-design elements
One-plane symmetry
Load distribution determined by elastohydrodynamic calculations of lubricated surfaces
Varying manufacturing constraints
Design elements
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Elasto-hydrodynamical Pressures in a Single Step
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Pressures on Guide Planes
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Constraint: Split Casting
Mass: 74 kg © MAN Diesel A/S
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Stresses and Final Design
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Constraint: Single Direction Casting
Mass: 97 kg © MAN Diesel A/S
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Constraint: Minimum Dimension
Mass: 106 kg © MAN Diesel A/S
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Stresses and Final Design
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Conclusions Better design can be achieved by topology optimization: Reveals necessary structure for better load carrying capacity Symmetry constraints provide design control Manufacturing constraints provide tools for feasible designs Design is optimized to sustain multiple loading scenarios This is achieved in a smoothly operating environment, OptiStruct
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