AU2013100080A4 - Submarine air handling system - Google Patents

Abstract

Abstract The present invention relates to a submarine air handling system. The system 5 includes a snort mast 12 for the submarine and a device 302 for inducing a flow of air through the snort mast 12 into an internal volume 200 of submarine when the snort mast 12 is in operation. The system further includes means 306 for maintaining the internal volume of the submarine at substantially atmospheric pressure. The invention allows for a greater pressure drop through the snort 10 mast 12 using a compressor 302 or the like to induce the air flow whilst still ensuring the internal volume of the submarine (i.e. where the crew is located) is maintained at substantially atmospheric pressure (i.e. substantially no pressure differential between atmosphere and the internal volume of the submarine). 3*12 31o 31L Fi-3vrc. 3

Description

P/00/009A Section 29 AUSTRALIA Patents Act 1990 INNOVATION PATENT SPECIFICATION Invention Title: SUBMARINE AIR HANDLING SYSTEM Applicant: PMB Defence Engineering Pty Ltd The invention is described in the following statement: 1 2 SUBMARINE AIR HANDLING SYSTEM Field of the Invention The present invention relates to an air handling system for a submarine. 5 Background of the Invention Conventional submarines run diesel engines to charge batteries that provide power to the submarine when the diesel engines are not in operation. When the diesel engines are in operation, they can be used to run propellers and/or, 10 run generators to charge the submarine's batteries. The diesel engines can only be run when they are fed with sufficient intake air from the interior of the submarine which acts as a plenum. When the submarine is submerged and remains close to the surface, the diesel engines 15 can be operated because a snorkel or snort mast is raised above the water surface to replenish air into the internal volume of the submarine. Air supply in the submarine is a critical issue. Supply, temperature, humidity and the pressure of the air in the submarine must be carefully controlled to suit 20 both the human crew, technical equipment and the diesel engines. The air pressure within the submarine is desirably maintained near atmospheric pressure whenever possible. However, a small under-pressure is normally held inside the submarine to enable draw of the required airflow through the snort mast. Air is pumped around the interior of the submarine to clear stale air. 25 There are many limitations that impact on snort mast design. Firstly, the snort mast must be sized to allow only a small pressure drop as air is inducted. This means that larger cross sectional masts are required. Large masts increase the submarine's wake making detection easier. Large masts are also heavy and 30 thus are slower to both raise and lower. They also require significant power to raise and lower.

3 The snort mast must be fitted with a valve at the top to prevent water flooding into the mast if it is over-washed by a wave or otherwise accidently submerged. It would be desirable for the mast to have a tracking system that drove it up and down automatically to maintain only a required length of mast above the moving 5 ocean surface. However, current large mast sizes increase the required power to operate such a tracking system which is highly undesirable. Another issue to be addressed in relation to the air handling system of a submarine is the need to properly control the humidity of the inducted air. In 10 tropical regions inducted air is highly saturated. The submarine's air conditioning system must remove the heat from the inducted air and must also de-humidify the air to a comfortable level within the submarine once air intake via the snort mast is stopped. 15 The submarine's air conditioning system must also address the significant heat load from the submarine's diesel engines, batteries and other equipment in use within the submarine and the crew. Although the diesel engines are cooled via a water cooling system, some of the heat load is inevitably transferred to the air conditioning system. The batteries heat during charging due to the resistance 20 and chemical effects, which adds further heat load to the air conditioning system after charging stops. Cooling loads are especially high when operating in tropical waters, where the effect of the salt water cooling systems are minimised. 25 The power level required to run the submarine's air conditioning system to reduce the require heat and humidity is very high. This power draw reduces the time that the submarine can remain submerged solely under battery power and thus reduces operational activities. 30 Various different air handling systems or environmental control systems have been developed to date for a wide range of applications. Systems for environmental control of the cabin of an aeroplane are disclosed in the art. For example, US patent 7,591,869 discloses an environmental control system for an 4 aircraft employed to regulate the temperature of the air entering the cabin of the aircraft. US patent 6,524,373 describes a method and apparatus for extracting water droplets from a water-laden airstream. US patent 6,735,953 discloses a turbo machine-driven environmental control system. However, the prior art has 5 failed to establish appropriate solutions for providing environmental control within a submarine that take into consideration the particular operational requirements of a submarine. The present invention seeks to address or at least alleviate some or all of the 10 above mentioned problems. The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known or part of the common general 15 knowledge as at the priority date of this application. Summary of the Invention According to a first aspect of the present invention there is provided a submarine air handling system, said system including a snort mast for the 20 submarine, a device for inducing a flow of air through the snort mast into an internal volume of submarine when the snort mast is in operation and means for maintaining the internal volume of the submarine at substantially atmospheric pressure. 25 The device for inducing a flow of air through the snort mast may be a fan, a compressor or any other suitable means for inducing a flow of air through the mast and into the submarine. The present invention allows for a greater pressure drop through the snort mast using a compressor or the like to induce the air flow whilst still ensuring the internal volume of the submarine (i.e. where 30 the crew is located) is maintained at substantially atmospheric pressure (i.e. substantially no pressure differential between atmosphere and the internal volume of the submarine).

5 The inclusion of a device to draw and thus induce air flow into the submarine via the snort mast rather than relying on a pressure differential between atmosphere and an internal volume of the submarine provides significant advantages and represents a major divergence from prior art submarine 5 snorting arrangements. When such a device is used to draw or induct air through the snort mast, much higher air flow speeds can be achieved compared to prior art arrangements where air flow speed through the induction pipe is only about 10 m/s. Increased air flow speed allows a much smaller induction pipe to be used and such a reduction in size allows for a reduction in the overall snort 10 mast size (i.e. cross-sectional area). This allows the external dimensions of the snort mast to be reduced. It is envisaged that a snort mast size of up to 25% of current mast sizes would be achievable. Current masts are typically oval in shape and have a length dimension of about 700mm and a width dimension of about 350-400mm. 15 Reduced snort mast external dimension (i.e. cross-sectional area) reduces the amount of surface wake on the ocean and also reduced visibility in all electromagnetic spectra. The size and shape of prior art snort masts are a compromise between providing sufficient cross sectional area for air flow and 20 hydrodynamic shape to control wake and visibility, since the required size is at upper practical limits for installation within the fin of the submarine. Embodiments of the present invention allow each aspect to be considered separately and thereby allow induction pipe size and shape optimisation for performance and low visibility, as well as optimisation of the exterior of the snort 25 mast for low wake, low drag and low visibility. Preferably, the device for inducing the flow of air through the air tube of the snort mast includes a first compressor. 30 Air flow through the air tube is preferably in the range of 20 - 250 m/s and more preferably between 50 - 250 m/s, whilst maintaining normal atmospheric pressure inside the internal volume of the submarine. Air flow is preferably as fast as possible without inducing choked air flow or undesirable noise levels.

6 The first compressor is preferably connected to a first heat exchanger so that the air flows from the first compressor and through the first heat exchanger, before passing through a first expander. The expanded air is then directed into 5 the internal volume of the submarine. The air handling system thus acts as an air conditioning system for the submarine. Air from within the internal volume of the submarine can be passed through a second or auxiliary compressor and then through the first expander before 10 being returned to the internal volume of the submarine. When a diesel engine of the submarine is in operation it may draw air from the internal volume of the submarine via a further compressor. That air passes through the diesel engine and the resultant exhaust gas is exhausted to an 15 exhaust system. In accordance with one embodiment of the invention, the exhaust gas from the diesel engines is used to drive a turbo which in turn drives the second compressor. This exhaust gas would usually be directed through a water cooled 20 muffler system in order to reduce the temperature of the exhaust before it exits the pressure hull. The use of an exhaust driven turbo has the effect of reducing the exhaust temperature, thus reducing the load on the mufflers and utilising energy which previously may have been removed from the system as waste heat. 25 In accordance with another embodiment of the invention, the first expander is connected to the first compressor so that work produced by the first expander provides drive to the first compressor. Alternatively, the first expander and first compressor are powered by an electrical source independent of the diesel 30 engines of the submarine. In accordance with one embodiment of the invention, the second or auxiliary compressor is preferably driven by an auxiliary turbine powered by exhaust 7 gases from the diesel engine. The auxiliary compressor may provide power to drive the first compressor. A second heat exchanger may be used to cool the air from the auxiliary compressor to ensure that the air produced is in the order of 1-2 0 C and that no ice is formed in the compressor. 5 Description of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 10 Figure 1 is a schematic partial cut away view of a submarine fitted with an air handling system according to an embodiment of the invention; Figure 2 is an enlarged view of part of the air handling system of the port engine shown in Figure 1; 15 Figure 3 is a simplified operational diagram for the air handling system shown in Figures 1 and 2; Figure 4 is a simplified operational diagram for an air handling system in 20 accordance with a second embodiment of the invention; Figure 5 is a simplified operational diagram for an air handling system in accordance with a further embodiment of the invention; and 25 Figure 6 is a simplified operational diagram for an air handling system in accordance with a further embodiment of the invention. Detailed Description of the Preferred Embodiments Figure 1 schematically illustrates part of a submarine fitted with an air handling 30 system according to an embodiment of the invention. In a very simple form, the system includes a snort mast arrangement 10 that provides induction air from above the ocean's surface for delivery to the internal volume 200 of the submarine. The induction air is drawn through the snort mast arrangement 10 8 where it enters an air conditioning system 300 (see Figures 2 and 3) before delivery to the internal volume 200 of the submarine. The submarine's diesel engines 400 can then draw the treated air from the internal volume 200. 5 As best illustrated in Figure 3, the air conditioning system for each engine 400 of the submarine includes a first or intake compressor 302, a heat exchanger 304, a first turbine 306 and a second or auxiliary compressor 308. The snort mast arrangement 10 includes a snort mast 12, a tank 14 and a 10 delivery pipe 16 for each diesel engine 400. Each delivery pipe 16 connects the free volume of the tank 14 to the intake compressor 302 of the associated engine 400. Intake compressor 302, heat exchanger 304, auxiliary compressor 308 are replicated for each diesel engine 400. 15 Tank 14 is located within the submarine and provides a storage space for water inadvertently taken through the snort mast 12. The tank 14 operating pressure is preferably well below atmospheric pressure (e.g. around 0.8 bar) and thus enables much higher air velocity within the mast 12 than otherwise possible. This results in the sea to surface penetration part of the mast being less than 20 25% of the size of prior art masts. The tank 14 may include internal baffles and the delivery pipe 16 preferably connects to the tank via a valve so as to prevent water being inadvertently drawn into the delivery pipe 16. 25 The intake compressor 302 for each engine 400 acts as a fan to draw air through the snort mast arrangement 10 and into the tank 14. The direction of flow of the air and exhaust gases in the system is shown by the arrows in Figure 2. 30 The drawn air is compressed and heated as it travels down the snort mast 12 and then as it travels through the intake compressor 302. The drawn air is 9 compressed to approximately 5 bar and heated to approximately 250*C after passing through the intake compressor 302. The heated compressed air is then moved through the intake heat exchanger 5 304. Intake heat exchanger 304 extracts heat from the air flow to reduce its temperature. The cooled air is then passed through the intake turbine 306 to expand the air, causing it to be further cooled and also dehumidified. The cooled and dehumidified air then flows into the internal volume 200 of the submarine via cool air outlet 200A. 10 The heat exchanger 304 reduces the air temperature to around 1000C or to a point such that when the air later exits the intake turbine 306 it has a temperature greater than about 0*C. 15 Air from the internal volume 200 of the submarine can be drawn via air inlet 200B into the auxiliary compressor 308 where it is again compressed and heated before passing back through the heat exchanger 304. That air then passes through the intake turbine 306 to again expand the air causing it to be cooled and dehumidified before re-entry into the internal volume 200. This 20 arrangement enables continued cooling and dehumidification of the air being pumped around the internal volume 200 of the submarine When the diesel engine 400 of the submarine is in operation, it draws air via inlet 200C via an engine induction compressor 310. That air passes through 25 the diesel engines 400 and is exhausted outside 500 of the submarine as part of the total exhaust gases via a compressor 312 and a turbine 314 and then outlet mast 500A. The intake turbine 306 is connected to the intake compressor 302 so that work 30 produced by the intake turbine 306 can be used to drive the intake compressor 302. It is envisaged that up to about 70% of the power needed to drive the compressor 302 can be provided by the intake turbine 306. An additional source of power needs to be provided to fully power the intake compressor 302.

10 The auxiliary compressor 308 may be used to provide that additional source of power for the intake compressor 302. Alternatively, the additional source of power could, for example, be provided by mechanical drive from the diesel engines 400 or an electric motor. 5 As shown in Figure 3, the auxiliary compressor 308 is driven by an auxiliary turbine 314 that draws energy from the exhaust gases leaving the engine 400. A controller (not shown) will be included to ensure that the air temperatures 10 within the system do not go below 00C to thereby prevent ice formation in the system piping and components. Control mechanisms will also be included to control both the temperature and pressure of the air within the internal volume 200 of the submarine. 15 Traditionally, the operating pressure of the internal volume of the submarine is about 0.96 bar-abs (i.e. slightly below atmospheric pressure). However, in accordance with embodiments of the present invention, the operating pressure of the internal volume of the submarine would be 1.0 bar-abs (i.e. at atmospheric pressure). 20 Although not depicted in Figure 1, an air tank or valve may need to be provided at the exit of the induction compressor 310 to prevent the system from being stiff and to avoid operating the compressor outside of its standard operating range (i.e. system needs to allow for some fluctuations in pressure). 25 The submarine's weight compensating tank may act as tank 14. This would be advantageous because snort masts typically already drain water to the weight compensating tank and the weight compensation tank will have sufficient available volume. Furthermore, the weight compensating tank is designed for 30 pressure and will be able to easily handle the associated pressure fluctuations (e.g. ± 0.25 bar). All snort air could be run through the weight compensating tank.

11 The induction air can be drawn through the snort mast arrangement 10 under action of the intake compressor 302 at very high speeds. High air flow speeds through the snort mast 12 can be achieved even with a cross-sectional air flow area much smaller than conventional snort masts. 5 Figure 4 depicts an air handling system for a submarine in accordance with a second embodiment of the invention. In accordance with the previously described embodiment (see Figure 3), cooled and dehumidified air exited the intake turbine 306 via the cool air outlet 200A into the internal volume 200 of the 10 submarine. Air is delivered at about 1-20C. As an alternative, and as depicted in Figure 4, air exiting the intake turbine 306 is fed to an intermediate chiller 600 and then through a second intake turbine 610 before flowing into the internal volume of the submarine via cool air outlet 200A. 15 Intermediate chiller 600 could be linked to the submarine's deionised water system. This in turn would be used to cool the batteries in the battery compartment, which during charging can reach upwards of 40 0 C. When the temperature of the battery is reduced during charging, the charge acceptance of the battery goes up. Charge acceptance is the capacity at which a cell can be 20 charged to before it reaches its 'gassing point'. The gassing point is the point at which the electrochemical reaction begins to start producing hydrogen, this reduces the efficiency of the charge and also introduces an explosive gas to the submarine, which is undesirable. For this reason standard operating procedures state that the batteries will not be charged past their gassing point during an 25 operation. Cooling of the batteries improves the 'charge acceptance' of the battery before it reaches 'gassing point'. Also, the batteries typically take up 7-15% of the submarine displacement, reducing the temperature of the batteries has a long 30 term cooling effect on the boat. Figure 5 depicts an air handling system for a submarine in accordance with a further embodiment of the invention. This embodiment allows the system to 12 work in cooler environments. This is particularly important for European operational submarines, where water temperatures are significantly cooler. This makes the air conditioning cooling component of the system less necessary. In accordance with this embodiment the energy produced would be used to 5 preferably cool the water system in the submarine and less for cooling the general environment. Figure 6 depicts an air handling system for a submarine in accordance with a further embodiment of the invention. The Figure 6 embodiment is similar to the 10 right hand side of the air handling system shown in Figure 3. As shown in Figure 6, air flow is induced down the snort mast 12 and into the tank 14 by the intake compressor 302. The intake air is compressed as it passes through the compressor 302 and is then passed through a sea water 15 cooled heat exchanger 304. The cooled air is then passed through expander 306 causing it to be further cooled, dehumidified and taken to about atmospheric pressure. The expanded air is then delivered to the internal volume 200 of the submarine. 20 Unlike the previously described embodiments, the compressor 302 and expander 306 are preferably fully electrically driven by another source (not illustrated) rather than being powered off a diesel engine of the submarine. It will of course be appreciated that the previously described embodiments may be modified so that the compressor 302 and expander 306 of such 25 embodiments are similarly electrically driven independently of the diesel engines. Embodiments of the present invention are developed from the novel inventive concept that induction air into the submarine via the snort mast should be 30 induced into the submarine, rather than relying on the pressure differential between the interior volume and atmosphere. That pressure differential is created by the diesel engines when in operation drawing air from the interior of the submarine. In contrast, drawing air via a fan (compressor) through the snort mast enables the air to be drawn at high speeds. Such embodiments also 13 facilitate a reduction in the cross-sectional area of the snort mast, decreasing the wake formed by the snort mast when it is raised. The described embodiment is advantageous because "snorting" would become 5 a cool and dry event rather than a warm and moist event. The cold air produced by the system would enable the submarine to be run significantly cooler during snorting. Cool air will be drawn into the boat and the engines will be able to also breath such cooled air. 10 The hotel load of the submarine will be reduced and the hotel load from the chillers at the completion of snorting will also be reduced. This has the added advantage of reducing the time required to 'snorkel' and charge the batteries, reducing the detectability of the submarine. 15 Although the described embodiment integrates the air handling system with the diesel engines of the submarine, this need not be the case. It is envisaged that the air handling system could be installed without such integration (e.g. electrically driven) and that such a system would still provide acceptable performance. Alternatively, supplemental electric drive may be provided to 20 ensure control of the internal pressure to atmospheric pressure even when the diesel engines are running at part power or not running at all. It should be appreciated that the air conditioning system is preferably configured to enable ventilation of the submarine by drawing in air through the snort mast even when the engines are not in operation. 25 It is envisaged that multiple air handling systems would be provided on each submarine. More than one system per diesel engine may be required, all using a common snort mast and tank. Multiple systems allow the air volume handled to be relatively easily controlled over the full range of number of diesel engines 30 running, at different power levels and with allowance for redundancy. The embodiments have been described by way of example only and modifications within the spirit and scope of the invention are envisaged.

Claims (24)

1. A submarine air handling system, said system including a snort mast for the submarine, a device for inducing a flow of air through the snort mast into an 5 internal volume of submarine when the snort mast is in operation and means for maintaining the internal volume of the submarine at substantially atmospheric pressure.

2. A submarine air handling system according to claim 1 arranged to 10 provide cooled and/or dehumidified air to the internal volume of the submarine and/or to ventilate the internal volume of the submarine.

3. A submarine air handling system according to claim 2 wherein the device for inducing a flow of air through the snort mast is a fan, a compressor or any 15 other suitable means for inducing a flow of air through the mast and into the submarine.

4. A submarine air handling system according to any one of claims 1 to 3 wherein the flow of air through the snort mast has a speed in the range of 20 20 250 m/s, preferably 50 - 250 m/s.

5. A submarine air handling system according to any one of claims 1 to 4 wherein the fan for inducing the flow of air through the snort mast includes a first compressor. 25

6. A submarine air handling system according to claim 5 wherein the first compressor is connected to a first heat exchanger so that the inducted air flow is passed from the first compressor and through the first heat exchanger. 30

7. A submarine air handling system according to claim 6 further including an expander, said expander arranged so that air from the first heat exchanger is passed into the expander and is cooled and/or dehumidified before being directed into the internal volume of the submarine. 15

8. A submarine air handling system according to claim 7 wherein air from within the internal volume of the submarine is circulated through a second compressor and then through the expander before being returned to the internal 5 volume.

9. A submarine air handling system according to any one of claims 5 to 8 further including a further compressor, said further compressor arranged to draw air from the internal volume to an engine of the submarine. 10

10. A submarine air handling system according to claim 9 wherein air that passes through the engine is exhausted to an exhaust system.

11. A submarine air handling system according to claim 10 wherein the 15 exhaust system is arranged to exhaust the exhaust gases from the engine out of the submarine.

12. A submarine air handling system according claim 7 or claim 8 wherein the expander is connected to the first compressor so that work produced by the 20 expander provides drive to the first compressor.

13. A submarine air handling system according to claim 8 wherein the second expander is arranged to provide drive to the compressor. 25

14. A submarine air handling system according to 8 wherein the second compressor is powered by a turbine driven by exhaust gases from an engine of the submarine.

15. A submarine air handling system according to any one of the preceding 30 claims further including a tank for receiving air drawn through the snort mast. 16

16. A submarine air handling system according to any one of the preceding claims including one of said devices for inducing a flow of air through the snort mast per engine of the submarine. 5

17. A submarine air handling system according to claim 16 wherein each of said devices draws air from the tank.

18. A submarine air handling system according to claim 7 wherein air exiting the expander is passed through a chiller. 10

19. A submarine air handling system according to claim 18 wherein the chiller provides cooling to a system used to cool batteries of the submarine.

20. A submarine air handling system according to claim 19 wherein the 15 cooling system is arranged to cool deionised water used in said batteries.

21. A submarine air handling system according to any one of the preceding claims wherein the internal volume of the submarine is at atmospheric pressure. 20

22. A submarine air handling system according to claim 7 wherein the first expander and compressor are electrically driven.

23. A submarine fitted with an air handling system according to any one of the preceding claims. 25

24. A submarine air handling system substantially as herein before described with reference to the accompanying drawings.