Hydrodynamic Analysis of a Turbofoil®


    In our Hydrodynamic Analysis of a Turbofoil®, we investigate:


First Principles, Conservation of Energy

   For all spreadsheets on the Integrated Power Technology Corporation™ website, energy extraction as a function of velocity of motive fluids is analyzed based on Conservation of Energy principles, all derived from the definition of kinetic energy. The work done by a motive fluid through a turbine, Wm as a function of the mass of the fluid, m and the fluid velocity, v being:

Fundamental kinetic energy equation

   The power of the motive fluid through the turbine relates to the kinetic energy by replacing the mass variable, m in the above equation, with the Mass Flow Rate variable Mass Flow Rate - M dot (in kg/s):

Mass Flow Rate Dependent Power Equation

   Where one defines the Mass Flow Rate variable, Mass Flow Rate - M dot as a function of the motive fluid density, ρ, the area of the gate of the turbine, AT, and the fluid velocity v:

Mass Flow Rate Definition

   Given the above definition one may substitute the motive fluid density, ρ, the area of the gate of the turbine, AT, and the fluid velocity v for the Mass Flow Rate variable, Mass Flow Rate - M dot back into the Mass Flow Rate Dependent Power Equation. From here we can express the power extracted by the turbine as the change in power, ΔPT, from that which drives the Turbofoil® equipped vessel when its turbine gate is closed. The power extracted, ΔPT, manifests in a change in velocity of the Turbofoil® equipped vessel when its turbine gate opens, here expressed in terms of the difference between v0, the vessel velocity with the turbine gates closed, and the resultant v1, the vessel velocity with the turbine gates open:

Kinetic energy conversion equation

   Rearranging terms:

Kinetic energy conversion equation rearranging terms

   One finally arrives at an expression determining the final velocity, as analyzed in the Turbofoil® Hydrodynamic Analysis Spreadsheet:

Kinetic energy conversion equation solve for final Velocity

   The Turbofoil® Hydrodynamic Analysis Spreadsheet also makes use of a Froude Number, Hull Speed, and Speed:Length (kts/ft½) Ratio in evaluating a Turbofoil® operating around The Big Island, Hawaii. A Turbofoil® equipped vessel at the Big Island of Hawaii with its turbine gate opened is probably still planing if: the vessel velocity is greater than Hull Speed; Speed:Length greater than an empirical value ranging from 1.34 to 1.51; and the Turbofoil® Froude Number =~ l'Hydroptère Froude Number and Turbofoil Speed greater than 12kts, the purported speed at which l'Hydroptère, the worlds fastest hydrofoil catamaran, or "HydroCat", begins to plane. Note that the Hull Speed in cell B15 of the Turbofoil® Hydrodynamic Analysis Spreadsheet is still less than the Open Turbine Gate Operational Speed derived in cell B16 even when the empirical number in cell B15 is changed from 1.34 to 1.51.

   The Hawaii regime was chosen because its hindcast wind data indicates it has the least strong winds of the regimes proposed in Integrated Power Technology Corporation™'s Configuration Geographic database.

   The greater the Froude Number, the greater the "resistance" due to bow and stern wave interference. This method is a generally accepted estimation in lieu of complete CFD analysis determining drag coeficients, etc. The Froude Number is given as:

Froude Number

   Where LWL is the hull length at the waterline in meters, g is the acceleration due to gravity, 9.8m/s. Hull Speed is given as:

Hull Velocity Equation

   Hull Speed in knots and LWL is the hull length at the waterline in feet for this approximation.



Turbofoil® Lift-to-Drag, Sail Power, LCOE, IRR, Break-even analysis model

Preliminary Results from on-going Turbofoil® Design Optimization Trade Space Exploration

Download the workbook that generates this graph and many others...
   Estimates Based on: Vessel length: 38m; Vessel Beam (widest hull width): 10m; Turbofoil® Span = Turbine Intake (Gate) Length: 10m; Turbine Intake (Gate) Height = 45% of Foil Thickness; Foil depth: 1.25m; Aspect ratio (Foil span/chord): 8; ρ Seawater Density: 1024kg/m3; Dynamic Viscosity of Seawater μ: 0.00108 Pa-s; Turbofoil® Efficiency, 85% of (Betz limit=59.23%): 50%; Generator Electrical Efficiency: 92%; Compressor/fuel pump efficiency: 94%; Off-loading time: 1.5 hours; Solid State Ammonia Synthesis (SSAS) efficiency: 7.5kWh/kg(NH3); 3 Turbofoil®s per Vessel; Ammonia recent spot price: $700/Metric tonne; Capital Expenditure for Structure: $6000/tonne displacement, displacement estimated as a function of weight of electrical generators required to capture all energy at each given speed: (5x10lbs/hp); Capital Expenditure for Turbofoil® Turbine only: $10.00/kW; Capital Expenditure for Electrical Generators: $271,500.00 per MW; Capital Expenditure for SSAS: $300,000.00 per Metric Tonne per day; Capital Expenditure for Storage tanks: $20.00 per gallon NH3; Capital Expenditure for SCADA/GIS/VPP/UMV Control & Communication: $500,000.00; Annual interest: 10.00%; Financing Term 10 years; 12 Periods per year; Crew Cost: $60.00/hour; 168 Hours/Week in operation; Monthly Maintenance/Docking Cost: $20,000. THESE ESTIMATES REPRESENT "FORWARD-LOOKING" DATA, YOUR RESULTS MAY VARY. Protected by U.S. and International patents and Patents Pending.

    The above graph illustrates results from an Interactive Boundary Layer analysis determining parameters such as Drag, Lift-to-Drag Ratio, Propulsive Power, Turbine Output Power, Sail Thrust Required, Levelized Cost of Energy (LCOE), 10 year Return-on-Investment (ROI), and Investment Rate of Return (IRR), amongst many others, thus creating a model from which to run Monte Carlo simulations and perform Trade Space Exploration to enable optimization of design and operational trade-offs. Integrated Power Technology Corporation™ has initiated this Lift-to-Drag model to further a Trade Space Exploration analysis for optimal Turbofoil® design, and the above graph is just one of many the workbook can generate. The model has 32 input and 88 output variables. Variables output from the model include Power Ratio, ep, and Hydrodynamic Performance Rating, HPR, to compare candidate Turbofoil® designs to other existing hydrofoil supported vessels of similar displacement and performance as described below.



Hydrodynamic Analysis of a Turbofoil® in Comparison to Existing Hydrofoil Catamarans


   The Hydrodynamic Performance Rating workbook assembles hydrofoil performance data, and using Professor Gunter Hoppe's suggested equations, (2) (for Power Ratio, ep, cells I19,20,22,23 in the HydroPerfRating spreadsheet tab; "the lower the better") and (7) (for Hydrodynamic Performance Rating, HPR, cells K19,20,22,23 in the HydroPerfRating spreadsheet tab; "the higher the better") from his paper Performance Evaluation of High Speed Surface Craft with Reference to the Hysucat Development. Here we compare two different Turbofoil® regimes, Hawaii and Chile to the other existing hydrofoils:

    In the Hydrodynamic Performance Rating workbook, the Hawaii_Froude and Chile_Froude spreadsheet tabs use the power numbers from the original First Principles, Conservation of Energy analysis spreadsheet tabs, Hawaii_Turbo and Chile_Turbo, respectively, based on Turbofoil® Configuration Geographic Data, Hawaii and Chile sourced from AWStruewind and 10 year NASA hindcast wind data.

    The Hawaii_Froude and Chile_Froude spreadsheet tabs give the Turbofoil® v1 speed (cell B16 in both sheets) after the turbine gates open, a change from the gate-closed speed v0 (Hawaii_Turbo tab and Chile_Turbo tab, cell B7 in both tabs), due to the power extracted by the turbine as the change in power, ΔPT as described in the Hawaii_Froude tab and Chile_Froude tab, (cell B29 in both tabs).

    Thus the Hydrodynamic Performance Rating workbook allows one to iteratively make estimates on the remaining Prime Mover power (cells G19,20,22,23 in the HydroPerfRating spreadsheet tab), needed to keep the vessel at the v1 speed after the Turbofoil® turbine gates open to extract the ΔPT, ultimately an estimation of the Prime Mover Power based on estimates guided by conservative Power Ratio, ep, (cells I15,16,18, 19; higher means more conservative) and Hydrodynamic Performance Rating, HPR (cells K15,16,18,29; lower means more conservative) in comparison to the other hydrofoils.

    For the Turbofoil® regime in Hawaii, the Prime Mover (High Altitude Sail) power needs to be 4MW, (cell G19,20 in the HydroPerfRating spreadsheet tab), plus 4.8MW, (cell B29 in the Hawaii_Froude spreadsheet tab) or a total of about 9MW.

    For the Turbofoil® regime in Chile, the Prime Mover (High Altitude Sail) power needs to be 10MW, (cell G22,23 in the HydroPerfRating spreadsheet tab), plus 10.8MW, (cell B29 in the Chile_Froude spreadsheet tab) or a total of about 21MW.



Other Existing Vessels Comparable in Concept to a Turbofoil®


   Several other Seaworthy vessels in operation today share similar concepts with a Turbofoil®, either in the form of a hydrofoil sailboat, a large vessel pulled by High Altitude Sails, or a vessel powered solely by Renewable Energy, three examples of which are documented here whose specifications are referenced elsewhere such as the Turbofoil® Hydrodynamic Analysis Spreadsheet.

L'Hydroptère

   L'Hydroptère, the worlds fastest hydrofoil catamaran sailboat, or "HydroCat" holds the record for over 57 knots in a short burst of time. A 60ft trimaran which, on reaching a speed of about 12 knots, is designed to lift all its hulls out of the water simultaneously to reduce drag; it planes along 5m above the surface on two hydrofoils that extend at an angle down into the water from the outer stabilisers. Five tons of titanium and carbon fiber materials comprise the vessel's superstructure, and can reach speeds of 50 knots over the water in winds of 25 to 30 knots.

   Here are basic specifications for the l’Hydroptère:

Length 18 meters
Beam 24.5 meters
Height of Lateral Foils 6.5 meters
Weight at Takeoff with 5 crew 6.5 tons
Weight in Flight with Wind Ballast 7 tons
Main Sail Area 165 square meters
Sailplan Fore-and-Aft Rigged

BBC SKYSAILS or "Beluga Skysails"

   The ship is 132m long with a deadweight 9,821t, a beam of 15.8m, a draft of 7.73m, an air draft of 37.50m to keel (29.77m +7.73m draft) and a cruising operational speed of 15.5kt.

   The Beluga SkySails has been equipped with a 160m² sail similar to a paragliding sail. The area of the kite can be increased to 320m² if required for even more pulling power.

   The MAK 8M32 diesel engine from Caterpillar has an output of 3,840kW with a volcano clutch, a transmission and a high-screw four-blade variable pitch propeller (Wärtsilä GMCP 800). There is one Wärtsilä electric bowthruster of 500kVA and the rudder is a free-hanging balance type from Rolls Royce.

   There is a shaft generator (Stamford HCM 534 F2) of 813kVA, two diesel generators (Scania DI 12-62M) of 335kW, and one diesel emergency generator of 85kW (Stamford UCM 224 G SISU 420 DSRG). There are tanks for 3,540m³ of ballast water, 73.1m³ of fresh water and 621.7m³ of heavy fuel oil.

   On route, the efficiency of the SkySails system was tested for up to eight hours a day were applicable in winds of up to force five (17–21 knots). The system was hailed as a success, with calculated savings of up to 2.5t of fuel/$1,000 a day. With larger sails of up to 600m², fuel savings of between 10% and 35% are possible. The Beluga SkySails will have a new 320m² sail installed as a continuation of its pilot testing.

   Depending on the prevailing wind conditions, the latest SkySails product generation has a maximal propulsion power of more than 2 MW (approx. 2,700 hp; equivalent ship engine).

   The worldwide patented SkySails System generates tractive force using large, dynamically flying towing kites, which in terms of physics is the most effective form of utilizing wind energy. With a good wind the SkySails SKS C 320 can produce a pulling force in the towing rope of more than 320 kilonewton (kN), a force greater than the thrust of both engines on an Airbus A321. The 32 meter width of the towing kite is just about as broad as the total wingspan of the A321.

   SkySails towing kites for ships operate at altitudes between 100 and 500 m where stronger and more stable winds prevail. By means of dynamic flight maneuvers, e.g. "Figure 8's", SkySails easily generate five to 25 times more power per square meter sail area than conventional sails. The propulsion system requires a towing rope that is light weight and incredibly strong, since the weight of the rope reduces the power generated by the kite. Dyneema® ropes withstand the high tractive forces of more than 32 tonnes, generated in air speeds of up to 180 kilometres per hour(50m/s). Dyneema® is by far the world’s strongest fibre, it is 15 times stronger than steel, light weight and extremely resistant to corrosive chemicals, abrasion and friction. Gleistein Ropes developed the Dyneema® towing ropes to meet the specific needs of SkySails kites.


TÛRANOR PlanetSolar

   The first large vessel to circumnavigate the globe powered only by solar energy.

Specification Data
Length (with flaps) 31 m (35 m)
Beam (with flaps) 15 m (23m)
Height above waterline 6.10m
Draft 1.55m
Deadweight est. 85,000 kg
Crew planned for circumnavigation 4 persons
Working hours for completion 68,000
Cruising Speed 7.5 kts (14 km/h)
Max. Speed 14 kts (26 km/h)
Solar Generator  
Surface Area 537 m²
Power (STC) 93.5 kW peak
Efficiency 18.8%
Battery  
Chemistry Lithium Ion
Battery Voltage 388V
Capacity 2910 Ah (485Ah / cell)
Total Cells 648
Weight per cell 13kg
Total Weight Battery with chassis about 11 tons
Efficiency > 95%
Motor (2 Motors each side)
Type Permanent Magnet Synchronous Motor
Nominal Power 2 x 10kW @ 1000 rpm (only 1 Motor each side)
Maximal power 2 x 60kW @ 1600 rpm (2 Motors each side)
Transmission Ratio 1:10
Efficiency @ nominal load 92%
Propeller and Steering System Principle Vector Prop, Rudderless Steering System Pitch Control for optimization efficiency
Propeller 5 blades
Diameter 2 meters
Nominal Speed /Maximal Speed 100 rpm / 160 rpm
Materials used Carbon Fibre 20.6 tons Sandwich Core 11.5 tons Epoxy Resin + Hardener 23 tons
Construction Cost EUR 15 Million
Maintenance (docking incl.) Antifouling and Germanische Lloyd certification renewal: about EUR 120,000

© 2013 Integrated Power Technology Corporation™ All Rights Reserved.