Lubrication system for Air in the Helmet

These fluids generate hydrodynamic forces and aerodynamic that cancel each other out, creating a resistance to motion also known as drag.

The total resistance R that you experience the boat it consists of the sum of two components:

• Aerodynamic resistance, RA
• Hydrodynamic resistance RH.

This last turn it consists of the resistance by friction RF and the pressure RP, which your time is divided into resistance wave conditions RW and resistance pressure viscose RVP.

To try to study the Resistance to the Advancedeveloped two hypotheses for the calculation, as they develop a sufficiently accurate to obtain the factor of this resistance is really complex:

• Hypothesis of Froude
• Hypothesis Hughes

The development of these hypotheses is obtained by the following formula:

In this way, the formula for calculating the total resistance of a ship moving through the water is:

2. Experiments and Studies Precursors of the Lubrication Layer of Air

The first experiments of reduction of resistance to the advance with microbubbles were made by McCormick and Bhattacharyab, pioneers investigated as to reduce the viscous friction (Rvp) in a body of revolution completely submerged covered with bubbles of hydrogen generated by electrolysis.

Experiment teachers McCormick and Bhattacharyya (1973)

The experiment consisted of the immersion of a body of revolution in the interior of a towing tank at a given rate of speed. This body had a wrap of copper wire, which by means of the hydrolysis of the water, generates micro bubbles steadily.

The reported results showed that the amount of reduction of the friction depends on of the speed and rate of the production of bubbles of hydrogen. The injection of a laminar flow of bubbles surrounding a solid body submerged, reducing the resistance to the advance (reduction the viscous friction of a 30%).

Research Numerical of Madavan (1985)

In 1985, Madavan conducted a research numerical to study the interaction of microbubbles with the structures of the boundary layer in order to clarify the mechanism behind the reduction of the drag. In their study, it was found that the presence of the microbubbles alters the viscosity and density of effective local within the boundary layer.

In addition, we observed a strong dependence between the reduction of the friction and the concentration, by volume of the microbubbles within the sublayer buffer.

Experiment of Charles L. Merkle and Steven Deutsch (1989)

In 1989, Merkle and Deutsch succeeded in a reduction of the friction of the 80% by combining the effects of the polymers with the microbubbles. However, during testing, it was concluded the injection of microbubbles was found to be ineffective in conditions of low speed due to the buoyancy of the bubbles.

This experiment showed the relationship significant among the reduction of the friction and the concentration and the diameter of the microbubbles.

Patent Ramón García Ferreiro (1999)

In 1999, the professor of the School of marine and Machines Ramón García Ferreiro, presented a patent application for a publication called "Ship mattress pneumatic«.

Description of the patent:

The present invention relates to the injection or supply air from the atmosphere into a concavity beneath the keel of the vessel as shown in figure 1, which is sucked by (1) and is driven by a compressor (2) to the area of injection or feeding (3) creating a cushion tire (4) located in the keel, formed by an insulating layer of air that serves as a seat of the vessel in the water.

To learn more about the details of the patent click here

Experiment Moriguchi and Kato (2002)

In 2002, Moriguchi and Kato sought to determine the influence of the diameter of the microbubbles in the reduction of friction. However, their results suggest that there is no influence of the size of the bubble in the phenomenon. It is necessary to perform further experiments to validate this conclusion, since it contradicts other findings obtained in previous studies.

In the following experiment (Fig. 4), is available in a tunnel of recirculation of a part subjected to an injection of air through a plate-porous. Using a few meters laser, we measure the dispersion of microbubbles and analyzes the speed of the flow.

After the experiment, it was verified that, in measurements taken near the surface of the hull, the speed decreased. This discovery is important because it indicates that the profile of velocities becomes less abrupt, which in turn decreases the voltage of the viscosity, which is directly related to the shape of the velocity profile

Studies of Alberto Aliseda and Juan Carlos Lashera (2005)

In 2005, Aliseda and Lashera studied the transport of microbubbles in a turbulent boundary layer. Analyzed how the microbubbles interact with the structures in turbulent boundary layer and how they are distributed in the velocity field. They also examined how to microbubbles affect the effective viscosity of the boundary layer and how this can influence the reduction of the drag on surfaces submerged. The results of the study provided a deeper understanding of the dynamics of microbubbles in the turbulent boundary layer and its potential to reduce the friction on surfaces submerged.

As an example of one of the studies conducted by Aleberto Aliseda and Juan Carlos Lashera, we will explain the following experiment (Fig 5) to determine how to reduce the size of the bubbles to analyze their effect on the effective viscosity of the boundary layer.

For this experiment it is necessary to inject a large amount of bubbles with a diameter average Sauter d32 ≈200 µmbecause that's the only way you can obtain a volume fraction is sufficiently significant for the study. Installing a injector aluminum with a cavity longitudinal mechanized along its leading edge.

The cavity is closed with a plate-porous through which supplied compressed air from the side of the hydrofoil.

To reduce even more the size of the bubbletarget microchorros of ethanol to the plate porous along the edge of attack the hydrofoil boat, so that the contact angle of the bubble increases, which facilitates the detachment of the plate.

3.Methods of Lubrication for Air

Lubrication for air to reduce the resistance of the hull, it works on the principle that we mentioned in the first point of the article, that the resistance due to friction of the surface is proportional to the hull of the vessel (wet surface of the hull). To carry out the reduction of this friction with lubrication by air, we have 3 methods:

• Method 1. Layer or Air Mattress (ALS)
• Method 2. Air chambers (ACS)
• Method 3. Paint Hydrophobic

3.1 Method of Layer or Air Mattress (ALS)

To generate a layer of lubrication for air effectively, we must inject the air at a constant speed to form a layer of bubbles, which reduces the drag and resistance between the boat and the sea water.

However, the effectiveness of this system depends on the following main factors:

• Size of the bubble.
• Location ejectors bubble/air
• Configuration of the injector.
• The distribution of air bubbles on the surface of the helmet it is an important parameter for reducing the resistance acting on the hull.

The layer of air is formed by injecting microbubbles with a diameter less than 1 mm, but larger than a micrometer. In this technique, small amounts of microbubbles in the turbulent boundary layer that it develops in the area of the wet surface. However, its application is limited to the ships large, as oilbecause they are very large, background and movement slow.

In the forward section of the hull you are generating multiple layers of small bubbles that must be routed properly to flow below the boat and to decrease the drag.

To be able to generate and maintain the layer of air bubbles, it requires some auxiliary systems and modifications (Fig 7.1.), as well as a source of air pressure, whose energy is included within the calculation of reduction of the drag (reducing the friction to forward) in around 20% of although proprietary systems such as the DK Group claim between 5% and 10%.

We have, (taking as an example the figure 7.2.) of two pairs of distribution boxes: one on the port side and the other on the starboard side are connected symmetrically to a sub-supply line. The boxes are equipped with protection against corrosion (anode) of zinc).

The system ALS can be applied in the design stage and built into a new ship, as well as to be installed on the ship already operating. The introduction of ALS in a vessel in operation is a complicated process and requires in-depth analyses, calculations, measurements and, more frequently, computer simulations.

There are several companies that specialize in the design and installation of ALS, and each company has called this system under the name of mark, for example:

• Mitsubishi Co. – Lubrication system Air Mitsubishi (MALS)
• R&D Engineering – System of Tube Air Induction with Wings (WAIP)
• Samsung Heavy Industries – System SAVER (SAVER Air)
• Silverstream – System Silverstream
• Foreship – Lubrication system Air Foreship (Foreship ALS)

To get an idea of the effectiveness of this system, we put a real-world example of study.

The ship oil tanker chemical tanker MT Amalienborg after you install a system ASL Silverstream, we recorded many operating parameters when ALS was on and off, among others:

• Parameters of operation of the propulsion system and speed of the vessel (in water,and GPS),
• Energy consumption by the air blowers
• RPM main motor
• Power of the spindle (torque)
• Consumption of fuel for the main engines.
• Weather conditions (conditions hydro-meteorological).

In the following chart we can see the comparison between the ALS system active and off(fig. 8)

This graph shows the impact of operation of the ALS system (Silverstream) installed on the vessel MT Amalienborg taking parameters on the changes of propulsion power (output shaft) and the speed of the ship.

The course of the parameters presented in this diagram shows that, by maintaining a steady speed of the main engine, the activation of the ALS system causes a decrease in the demand for propulsion power and does not significantly affect the speed of the shipalso the bottom part of the diagram shows the consumption of energy by the blowers ALS.

3.2 Method of Air Chambers (ACS)

The Method of Air Chambersin English Air Cavity System (ACS)consists in the implementation of one or more pockets of air throughout the ship which are filled with a constant flow of air. This process will reduce the surface submerged, what is known as "wet surface", and, therefore, will decrease the drag. It is called this technique "lubrication of chambers of air cavity". It is recommended that the use of this technique in the boats that they have a broad flat surface in his helmet, allowing the installation of large air chambers.

Unlike the previous system, the system ACS can only be implemented in the design phase for ships of new construction, as the cavities are part of the line shape of the hull, there are systems or tanks to be installed.

The cavities of the bottom of the hull are designed to reduce the wetted surface area of the ship and reduce the resistance to the advance.

The improvement in the reduction against the drag, i.e. the resistance to the advance by friction, is located in a efficiency of 5-15% (taking as a sample the data on the ship of study (ACS Demostrator)

3.3 Method of Paints, Water Repellents

The paintings water repellent or hydrophobic, in reality they are not a method of lubrication of air directbut if reacts directly with the boundary layer between the hull and the water around the boat.

The objective this method is to prevent the formation of the boundary layer. This could be used as an additional feature to the methods mentioned above.

Despite being an effective method of reducing the resistance to the advance, is a method of a high cost and a durability very small (Effectiveness approximately 1 month).

Another effective method to reduce the resistance to the advancement in the field of paintings it is the antifouling, but ruled out entirely in the industrial field by their low durability and high cost.

5. Prototipos Instalados en Buques

The prototypes listed below share similarities in the principles of operation.

These systems have been designed to improve energy efficiency and reduce the environmental impact of the maritime industry, through the reduction of fuel consumption and emissions of greenhouse gases. Although each of these systems has a design and operation-specific, all share the goal of reducing the hydrodynamic resistance of the vessel's hull and improve the efficiency in the consumption of fuel.

5.1 Mitsubishi Air Lubrication System (MALS)

In 2010, it was installed two transporters modules with the Lubrication System of Air-Own Mitsubishi (MALS), becoming the first application in the world of a lubrication system of air using air blowers in vessels of ocean navigation. MALS has demonstrated ato 13% reduction in CO2 emissions.

5.2 DK Group Air Cavity Chambers

The system DK Group Air Cavity Chambers is a fuel saving system for ships that uses air chambers to reduce the friction and the hydrodynamic drag of the hull of the ship. The system is based on the principle that the creation of a chamber of air below the hull of the ship reduces the resistance of the water and, therefore, fuel consumption.

The air chambers are created by the installation plate on the bottom of the hull of the ship. These plates have small perforations that allow water to flow through, which creates a layer of air below the hull. This layer of air reduces the friction and the drag of the water, which allows the vessel to move with greater ease and efficiency.

The system DK Group Air Cavity Chambers has been shown to be effective in the reduction of fuel consumption and emissions of greenhouse gases in the vessels. In addition, the system is relatively easy to install in existing vessels and does not require significant changes in the design of the hull. This makes it attractive to shipping companies that seek to improve the efficiency of their operations and reduce their environmental impact.

As we discussed in the section 3.2, the prototype of this type of systems is carried out on the vessel ACS Demostrator. The developer, DK Group ensures a reduction of fuel consumption by between 5%-10%

5.3 System Silverstream

The system Silverstream is a propulsion system of compressed air designed to reduce fuel consumption and emissions of greenhouse gases on merchant ships. The system uses an air compressor to capture and compress the air of the ocean while the ship moves. Then, this compressed air is used to reduce the hydrodynamic resistance faces the hull of the ship and improve its efficiency in the consumption of fuel.

The system works by the creation of air bubbles in the vessel's hull, which reduces friction between the water and the hull. This allows the ship to move more easily through the water and reduce the energy required to move it. The system also you can significantly reduce the emissions of carbon dioxide (CO2) and oxides of nitrogen (NOx) produced by the engines of the ship.

In addition, the system Silverstream does not require significant changes in the design of the hull of the ship, which makes it easy to install in existing vessels. Also has shown that the system is cost-effective in terms of fuel savings and emissions reduction, what makes it attractive to shipping companies that are looking to improve their operational efficiency and reduce their environmental impact.

5.4 System of Tube Air Induction with Wings (WAIP)

The system WAIP works by installation of a series of tubes of induction of air in the hull of the ship. These tubes are equipped with a wing design it captures the moving air as the ship moves through the water. The air caught turns to the internal combustion engines of the ship, which allows the engines burn a mixture richer fuel and air, thus improving the efficiency of fuel and reducing emissions of greenhouse gases.

The system WAIP has been shown to be effective in the reduction of fuel consumption and emissions of greenhouse gases in the vessel. In addition, the system is relatively easy to install on existing vessels and does not require significant changes in the design of the hull. It is also compatible with a variety of fuel types, which makes it suitable for use in a wide range of vessels.

5.5 Sistema SAVER (SAVER Air)

The System SAVER (SAVER Air) is a fuel saving system for ships using a device called SAVER to reduce the resistance of the water on the hull of the ship. The device SAVER is composed of a series of parallel plate that is placed in the bottom of the hull of the ship, creating a space of air between them and the hull.

The system works by creating a space of air below the hull of the vessel it reduces the hydrodynamic resistance. This allows the vessel to move more easily through the water and reduce the energy required to move it.

The system SAVER is relatively easy to install in existing vessels and does not require significant changes in the design of the hull.

5.6 Air Max Air Cushion System (Stena Bulk)

The Air Max Air Cushion System is a system of air cushion developed by the shipping company Stena Bulk to improve fuel efficiency and reduce the hydrodynamic resistance of the vessels. This system uses a cushion of air that is pumped below the hull of the ship, which allows the vessel to float on a layer of air in place of water, by reducing the friction between the water and the hull of the ship.

The Air Max Air Cushion System is composed of a number of air chambers installed below the vessel's hull. These air chambers are inflated using a pump system of air, creating an air cushion that lifts the vessel above the water and reduces the friction between the hull of the ship and the water.

6. Design of a System of Lubrication for Air

The design of a system of lubrication for air is a complex process that involves the selection of the appropriate components to ensure a safe operation and efficient. Below are described the main components and considerations that should be taken into account in the design of a system of lubrication for air.

1. Group of compressors and electric motor (M. E) of 15HP.
2. Filter aspirated air.
3. Ventilation of the room.
4. Refrigerators and hair dryers.
5. Non-return valve.
6. Accumulator air, main tank.
7. Safety valve. Pressure limiter.
8. Trap manual.
9. Pressure switch. When you reach the deposit up to the maximum pressure, it sends a stop signal to the motor.
10. Pressure gauge of the deposit.
11. Pressure gauge system.
12. Filter.
13. Regulator.
14. Lubricator/Degreaser.
15. Pipes fixed rigid.
16. Piping removable rigid PVC.
17. Piping system main power supply.

• Effect of buoyancy on the dynamics of a turbulent boundary layer laden with microbubbles. Aurotres: A. Aliseida and J. c. Lasheras. Article in Journal of Fluid Mechanics · July 2006
• Air Lubrication [Scheepvaart In Transport College] [Hogeschool Voor de Zeevaart].
• Estudo Experimental of a turbulent boundary layer with microbubbles. Memories of the XVI International Congress of the Annual SOMIM. Nuevo León. Mexico
• Study of the lubrication mattress air in the hull of a ship. Author: Pau Capella Coast. [GFR - Faculty of Nautical studies of Barcelona. Universitat Politècnica de Catalunya].
• Study methods of prediction of resistance to the advance. Author: Ignacio Fabregas Claramunt. [GFR - Faculty of Nautical studies of Barcelona. Universitat Politècnica de Catalunya].
• Systems of reduction of the resistance progress in navigation using a layer of air between the hull and the water. Author: Alejandro J. Medina Guerrero [GFR - Faculty of Nautical studies of Barcelona. Universitat Politècnica de Catalunya].
• International Conference on Ship Drag Reduction (SMOOTH-Ships). Istanbul Technical University.
• Assessment of the Propulsion System Operation of the Ships. Equipped with the Air Lubrication System. Author: Mariusz Giernalczyk and Piotr Kaminski.
• DK Group Improving efficiency by retrofitting of an existing vessel with ACS air lubrication system.
• CFD investigation of ALS
• technique on frictional drag reduction of bulk carrier. Siemens Digital Industries Software.
• Research Progress of Air Lubrication Drag Reduction Technology for Ships. Author: Hai'an, Haozhe Bread and Po Yang. College of Aerospace and Civil Engineering, Harbin Engineering University. China
• Drag reduction by microbubble injection in a channel flow. Mexican journal of Physics 54 (1) 8-14 February 2008.
• Glossary of Terms [Lubrication Equipment Division. Draco].
• (News) It receives a ship that produces bubbles of air in the helmet to reduce emissions [www.argenports.com.ar.
• Microbubble Drag Reduction in Liquid Turbulent Boundary Layers. American Society of Mechanical Engineers
• (Video) MALS (Mitsubishi Air Lubrication System) – green ship technology for energy saving by air carpet.

Author

: Roberto García Soutullo