Fuel Simulation Within The Royal Australian Navy

Transcription

1 Fuel Simulation Within The Royal Australian Navy Mr Warren Reid; Dr Jim Taylor and Dr Jim Brown Defence Science and Technology Organisation, Maritime Platforms Division Abstract. The Royal Australian Navy (RAN) currently expends in excess of A$120 million per year on fuel supply, storage and usage issues. Most of the fuel is F76 or a long life version of commercial marine diesel, which must be specifically ordered from commercial suppliers, usually with long lead times to delivery. The Defence Science and Technology Organisation (DSTO) is currently examining efficiency and sustainment aspects of fuel supplies to the RAN Naval Fuel Installations (NFIs) at various locations around Australia. This paper describes a fuel model that has been developed to simulate the sustainment of naval fuel supplies in terms of its timely distribution, cost and quantities. The model, known as the THIRSTY (Time History of Replenishment and SusTainabilitY) fuel model, has been developed so that costings for particular fuel usage scenarios can be assessed in advance of fuel ordering to enable more accurate and efficient fuel distribution and quantity data to be provided to the commercial supplier - with appropriate cost savings. The model will also help determine the operational holding levels within NFIs, which will assist the RAN to determine its fuel operational and holding distribution policy. 1.1 General Sustainment A significant issue with the management of the RAN s capabilities within a Whole of Life - Whole of Capability conceptual framework is the ability to assess and predict the sustainment requirements of naval ships beyond their initial deployment periods. Sustainment is defined in this paper as being a ship s demand over a defined time period for consumables such as ammunition, food, fuel, lubricants, maintenance, medical supplies, spare parts, etc. Ships inherently have the ability to initially operate for a period of time before needing replenishment of consumables. The need to improve the sustainment assessment of items such as fuel is also driven by the current resource-constrained environment in which the RAN operates coupled with its highest level of operational activity since the Vietnam War. In response, the RAN is attempting to better determine its operational requirements with respect to sustainment items such as fuel to ensure sustainment costs are minimised. To this end the RAN has tasked DSTO to develop an enduring decision support tool that will enhance the understanding and optimising of relationships that exist between the acquisition, storage, distribution and consumption of diesel fuel. DSTO is developing, for the RAN, a fuel demand model and fuel stockholding methodology that will enable the formulation of robust and transparent reserve stockholding policies and determination of long-term tankage requirements particularly in the north of Australia. Fuel is the first in a series of sustainment items to be addressed by DSTO activities that will involve the The model simulates single or multiple ship fuel usage requirements and currently exists as a prototype undergoing validation and assessment by various naval authorities. development of methodologies and models for 1. INTRODUCTION assessment and reporting. The RAN will, by improving its ability to assess and predict sustainment requirements, be better positioned to prioritise resources across all sustainment items. One aim is to ensure that no essential sustainment item is under-resourced in relation to others, thereby significantly reducing operational sustainment.. For example, it is no use for Navy to have a one-year operational supply of ammunition and medical supplies, if it only has threemonths worth of spare parts. Assessments and predictions also need to take into account that many items used by the RAN have long production leadtimes and cannot be obtained at short notice even with significant resources. 1.2 Fuel Requirements Military operations conducted by the Australian Defence Force (ADF) over the last couple of years have highlighted the need for the Australian Defence Organisation (ADO) to ensure that adequate RANspecific fuel stocks are maintained against the possibility of operations being conducted at short notice. Such short notice operations potentially preclude the purchase, prior to the operation commencing, of RAN-specific fuel stocks due to production lead-times. The RAN s current strategic work on its forward fuel needs has arisen out of a decision by the Directorate of Navy Preparedness and Plans (DNPP) to examine Naval fuel and stockholding requirements because of concerns about stockholding levels falling below prescribed minima. Of considerable current interest is the fact that the Darwin Naval Fuel Installation (NFI) is at the end of its operational life, and a fuel stock holding policy will help determine its future and whether it is required or to be rebuilt.

2 2. ROYAL AUSTRALIAN NAVY FUEL USAGE 2.1 Fuel Usage Issues There are three main issues driving the RAN fuel usage modelling and simulation: (i) Peacetime fuel distribution; (ii) Costing of operations for peacekeeping and wartime situations; (iii) Fuel stockholding and distribution policy. The RAN is currently using over A$120 million worth of fuel and lubricants per year. This equates to a sizeable portion of its budget and potentially there is a large opportunity to save much in the way of fuel costs by optimising ordering and distribution arrangements. The RAN currently operates four NFIs around Australia at Sydney, Stirling (WA), Darwin and Cairns. Fuel is purchased and delivered to these NFIs via bulk fuel standing offer contracts. These Standing Offers are purchasing contracts that set the details of the price, delivery, payment and quality of fuel at the commencement of the standing offer period. The standing offers do not detail the amount of fuel to be used at any location, due to the high level of uncertainty that the RAN has in predicting the expected annual fuel usage, due to unanticipated operational tasking. By being able to model future fuel usage scenarios with reasonable accuracy, the RAN will be able to purchase fuel either when fuel costs are low or by bulk forward buying resulting in cost savings. 2.2 F76 and F44 Fuel The two main fuels used by the RAN are F76 (Marine diesel) and F44 AVCAT (Aviation jet fuel for marine engines). Both these fuels are variants of commercial fuels but typically have additives incorporated to increase shelf life and flash point. In the case of F76, additives also lower the fuel clouding temperature, so that ship filters are not blocked when temperatures fall below the commercial fuel clouding temperature. One option open to the RAN is to make more use of commercially available fuel, both at non-nfi and NFI ports. This would make the RAN fuel purchasing policy simpler, in that the Navy would not have to plan for batch buys of F76, as commercial diesel would be readily available. The issues of fuel shelf life and clouding would, however, then have to be addressed and tracked on ship or at least allowed for when ships sailed south into cold waters. 3. FUEL MODEL DEVELOPMENT 3.1 Systems Dynamics Software The fuel model was developed under proprietary software called ITHINK [1], which is basically a system dynamics modelling tool. The software allows models to be developed so that they either run in real time or in the case of the fuel model, scenarios that may extend over an operational period of sixmonths or a year can be examined in a timeframe of a few seconds. 3.2 THIRSTY Fuel Model The fuel model in some respects is a virtual ship in that routes or passages that the ship will sail on are loaded into the model. It also takes into account when a vessel is in port (ie. alongside). The user has full control over the dynamics of ship operations that will affect fuel consumption. Fig 1 shows the main menu of the user interface. 1. Instructions The RAN "THIRSTY" (Time HIstory of Replenishment & SusTainabilitY) Fuel Model, single vessel - Main Menu 2a. Run Simulation 3a. Change Ship Parameters 3b. Choose Vessel/Aviation Type 3c. Change vessel Fuel Parameters 4. Observe Ship's Passage 5. Observe Ship's Fuel Level v time 6. Results and Outputting to File Print Pages Print Setup... Save Save As... Close Model Quit Figure 1. User interface for the THIRSTY fuel model

3 The main menu allows the user to access and return from all areas of the model. Modifications to default settings are made via the standard ITHINK set of control knobs, an example of which is shown in Figure 2.? No of Vessels Figure 2. Example of the standard ITHINK control knob used to change default settings within the Fuel model The following sections give a brief description of these areas and settings Vessel General Characteristics and Fuel Usage Vessel type The model simulates all current RAN vessels through a series of fuel consumption curves, which plot fuel consumption against speed. The user can change these curves to suit different engine configurations or even allow for equipment efficiency degradation due to age or maintenance schedules. Essentially the main propulsion unit is modelled as one unit along with the auxiliary service generators as a secondary unit, all drawing fuel from one major fuel tank. In reality this does not happen for every vessel, especially the larger ones, however it must be remembered that the intent of the modelling is to replicate fuel draw downs from NFIs and not to produce an actual fuel consumption model for a virtual ship. Sea state and direction conditions are also simulated in that linear variations to the vessel s fuel consumption curves are invoked by selecting the sea state and/or the sea direction Refuelling For each vessel type, the maximum useable fuel capacities are already included in the model, allowing the user to enter the desired percentage refuelling level (when refuelling is available) and the starting percentage-full level of the vessel. Like many other options in the model, this allows the user to perform what if analysis to look at the effects of changing the level at which refuelling takes place (this is usually defined in RAN doctrine depending whether a vessel is within Australian waters or not). Depending upon the route that a vessel may be sailing at the time, when it reaches port there are various refuelling codes included in the model that tell the vessel what types of fuel are available. The user has the option of changing these and therefore can opt for taking on commercial diesel as opposed to the default F76 fuel. Fuel may also be taken-on out of port such as from an oiler, and it is 20 simply a matter of changing the default refuelling options during a non-port sailing stage to do this. When refuelling from an NFI or a commercial port, the model allows the user to alter the operational characteristics of the installation. This covers the minimum and maximum permissible refuelling level capacity of the installation and also builds in delays such as ordering delay periods. If the refuelling option chosen is an oiler, then this can be incorporated into a multi-ship scenario (see Section 3.4). The model also details the cost of fuel used by utilising default fuel cost values for each of the ports in which fuel is available. These values are based upon standing offers from fuel companies that detail the cost of delivering fuel to the various NFIs. Like most other variables, the user has the option of changing these default values and in this case this is likely to be quite regularly, especially when fuel is offered by another supplier usually at a substantial discount. Many RAN vessels also carry aviation fuel (F44) for use in the fleet air arm (helicopters). The user has the option of setting the flying time of helicopters off the vessel in hours per day, whilst the model automatically checks to see if the vessel in question is capable of supporting this type of aircraft and will not allow this option to be used if this is the case Vessel Location An integral part of the model is the way in which a vessel is sailed on pre-defined or user defined courses, as a real ship would actually be. This means that actual vessel sailing patterns can be modelled (for the RAN these are covered in the Fleet Activity Schedule or FAS) and fuel drawdowns from installations or vessel consumption figures can be modelled directly. The model does this by starting a ship at a specific longitude and latitude (typically homeport) and the ship is sailed around a course by entering specific bearings and distances to sail at user defined speeds. A default series of courses already exist in the model for various scenarios and the user has the option of modifying these or generating new ones. When a vessel completes one leg of a course combination, the model moves onto the next leg and automatically updates information such as the total distance sailed. To aid in determining legs for various course combinations, an Excel spreadsheet has been generated for course planning and recording purposes. This is covered further in Section 3.3. When a vessel enters port, the user has the option of having the vessel stay in port for whatever number of days are required and whether shore power or auxiliary ships engines provide the hotel load Output Information There are a number of important data outputs from the model. The first and major one of these are fuel draw downs which show when, where and how much fuel is taken on by a vessel at the various NFIs and commercial

4 ports around Australia and overseas. An example of this is shown in Table 1, which details a section of this information for a period of seven days. Information is usually output every quarter of a day but has been simplified to one-day periods for this example. Table 1. Typical output from fuel model showing fuel drawdowns in cubic metres (m 3 ) Route Description Day Route No. F76 (m 3 ) Com. (m 3 ) F44 (m 3 ) temperatures of around 15C or below. Figure 3 shows the fuel clouding warning meter, which is a standard ITHINK output meter modified to suit this purpose. Risk of Fuel Cloud Melbourne to Sydney Melbourne to Sydney Figure 3. Fuel clouding warning meter. Information is also output graphically such as in Figure 4, which shows the fuel stock holding levels for a NFI, Commercial Refinery and an Oiler plotted against time. Melbourne to Sydney Sydney Brisbane Sydney Brisbane Sydney Brisbane to to to Brisbane to Cairns Table 1 shows that this particular vessel did not refuel on Day 1 but took on 70.1 cubic metres of F76 fuel on day 2. Knowing that this particular route number (201) does not finish in Sydney (route 203 does) then the user can check that the vessel has been set up to be refuelled by an oiler during this part of the passage. Similarly on Day 3 the vessel takes on 90.3 and 40.4 of F76 and F44 respectively at Sydney port (end of route 203), as this is where this Sydney stage finishes. On Day 6 another refuelling takes place but this time commercial diesel is taken on when the vessel reaches Brisbane, as there is no F76 available there. In addition to the tabular drawdowns, the model also displays graphical plots of the vessel s fuel level with time and its geographical location with respect to longitude and latitude. The model also has an algorithm built in to look at situations where if commercial diesel is taken on, there will be fuel-clouding situations when the vessel sails into colder southern oceans around Australia. This is assessed based upon average sea temperatures against latitude and can be important as some commercial diesel can cloud (ie block filters) at 3.3 Associated Spreadsheet The fuel model requires leg and course information to be input via a series of route numbers, which correlate with specific routes. In order to keep track of the default values allocated to these routes an EXCEL spreadsheet has been set up to do this and to be used as a course planner when generating various scenarios. The spreadsheet contains a number of worksheets, which are discussed in the follow paragraphs Course Definition and Defaults This sheet holds all the default information on each of the specific routes and allows the user to generate new course information by entering starting and finishing longitude/latitude values for each of the course stages. This generates a bearing and stage distance. Figure 5 shows a section of this sheet The first column of Figure 5 lists the Route number, which is the defining value entered into the fuel model program when determining the combination of legs and course to be travelled. The second column defines the route. In this case three different examples are shown. For routes 6 to 14, these correlate to when a vessel is alongside in port and drawing electrical power from shore (ie no main or auxiliary engines are being run). Routes 20 to 28 allow the user to take detours from set port to port courses, such as when a vessel goes out on patrol. Routes 200 to 213 show typical combinations of routes that would be used to go from Sydney to Melbourne (Routes 200 to 204), Melbourne to Sydney (Routes 205 to 209) and Melbourne to Adelaide (Routes 210 to 213).

5 1: 2: 3: 4: 1: Com Supply 2: NFI 3: Oiler 4: F44 supply : 2: 3: 4: : 2: 3: 4: Graph 3: p1 (Single Supply Fuel Stora Days Figure 4. Graphical output of fuel stock holding levels against time - whether refuelling in port takes place - type(s) of fuel available in port - the fuel cost for each fuel type in port or from an oiler Columns 4,5,6 & 7 of the table shown in Figure 5 show the starting longitude and latitude (columns 4 & 5) and Finishing longitude and latitude (columns 6 & 7) for each of the pre-defined routes. Columns 8 & 9 show the bearing and Great Circle distances respectively for the various starting and ending longitudes/latitudes. These values are generated automatically depending on the longitude/latitude information that is entered. Although not shown in Figure 5, there are also a number of other default values incorporated into the fuel model and shown in the spreadsheet. These cover: 2:36 PM Wed, 13 Mar the average speed at which the passage stage will be traversed - the time taken to traverse the passage stage at the average speed - the sea state (sea state 1 is default) - the sea direction Route Route Name Route Start Finish Required course Great Circle No. black font indicates loaded into ITHINK No. Longitude Latitude Longitude Latitude Direction (deg) Distance (nm) (See note 3) (See note 3) (See note 1 on sheet 3) (See note 2 on sheet 3) 6 1 Day Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) Days Alongside (no engines) nm trip to north nm trip to north nm trip to north nm trip to north nm trip to north nm trip to north nm trip to north nm trip to north nm trip to north Sydney to Melbourne (stage 1) Sydney to Melbourne (stage 2) Sydney to Melbourne (stage 3) Sydney to Melbourne (stage 4) Sydney to Melbourne (stage 5) Melbourne to Sydney (s1) Melbourne to Sydney (s2) Melbourne to Sydney (s3) Melbourne to Sydney (s4) Melbourne to Sydney (s5) Melbourne to Adelaide (s1) Melbourne to Adelaide (s2) Melbourne to Adelaide (s3) Melbourne to Adelaide (s4) Figure 5. Spreadsheet section detailing route information

6 Aside from acting as a reference for the fuel model in terms of the various routes and passages that may be taken, other worksheets in the spreadsheet also allows the user to do course planning. This consists of displaying relevant information for various combinations of routes when they are entered, as they would be in the fuel model. This allows the user to determine and assess whether the routes and passages planned are the correct combination to be entered into the fuel model. 3.4 Multi Vessel Model At this stage most effort has been devoted to the development of a single vessel fuel model. However a multi vessel version has also been developed. The multi vessel version takes the single vessel version and then copies it for as many ship types that there are in the RAN. At this stage this results in 10 different vessel types with each vessel type capable of representing multiple versions. If one of the active vessels is an oiler then all the other ship types become interactive with the oiler in that they cannot refuel from it unless they are in the same approximate location as the oiler. If for instance the oiler is required to return to a port to replenish its tanks then it will be off station and other ships will refuel when they return to port. 4. SUMMARY A system dynamics model for fuel usage within the RAN has been discussed in this report. The model will help determine a strategic fuel holding and distribution policy to be developed for the RAN. The model determines the type, when, where and how much fuel will be drawn down from port or oiler locations against specified sailing routes developed by the user. REFERENCES 1. ITHINK, High Performance Systems, Hanover USA