Modelling and Optimisation of the Hydraulic System on a Submarine

Abstract

A hydraulic system is designed to transport fluid power over large distances, from pumps to actuators where the fluid power is transformed to mechanical power. The submarines, built and designed by Saab Kockums, utilises such systems. There are, however, challenges as the hydraulic pumps consume much energy, and the system accumulators command significant space. As both energy and space are limited on a submarine, Saab Kockums wished to optimise the hydraulic system with respect to these quantities.

To explore alternative system configurations, a simplified model, with a selected number of key functions, was built using MATLAB Simscape. Five configurations, with varying available pump power and accumulator volume, were simulated for different operations situations. The time range simulated was, however very short due to slow convergence and difficulties with automatic control.

The simulation results were analysed in regards to energy and accumulator volume, as well as the performance of any masts, valves and rudders in the system. While the results were heavily affected by project limitations, and not entirely conclusive, a viable alternative system configuration was determined. A 50 % decrease of the volume pump flow showed potential to consume less energy while still retaining the performance of the applications.

The other configurations, though rejected, did nonetheless contribute to increasing system knowledge. Firstly, it is possible to lower accumulator volume, though 50 % is too much. Secondly, the location of the accumulators is less important than total volume, increasing options as they can be relocated more freely. Thirdly, this master thesis has proven that optimisation of the submarine hydraulic system is a subject worth exploring further, with many alternative system configurations to investigate.

Popular Abstract

The submarine, a vital component of the Swedish defence line requires a well-functioning hydraulic system which is both energy efficient and space efficient. Can such a system be achieved?

“Esse non videri”, the motto of the first Swedish Submarine flotilla, to be, but not be seen. The Submarines in the Swedish navy form an important first line of defence for the nation. Their mission, to guard the Baltic Sea and to gather intelligence relevant for national security.

You might ask yourself, what does the hydraulic system have to do with the submarine’s ability of collecting intelligence? Well, simply put, the less energy the hydraulic system consumes, the longer the submarine can stay below surface, and the longer it can gather intelligence. Easy! Or is it?

The hydraulic system on a submarine is responsible for operating much of the heavy-duty equipment, e.g., masts and rudders, equipment critical for the performance of the submarine. What does that mean? Well, the masts are heavy, and their weight must be overcome for the mast to rise. By using a cylinder, with a piston, one side of the piston can be filled with hydraulic fluid. As pressure builds up, so does the force acting on the piston. Ultimately, the force becomes so large that the piston starts to move. The cylinder is a so-called linear actuator, there are also rotary actuators working with the same principle, though they rotate and create torque. The oil used to fill the actuator is supplied by a pump and transported through a piping system. The system also contains large accumulators, used to supply extra oil if the pump flow is not enough.

Here matters become complicated, energy is after all not the only factor taken into account for optimising the system. For the submarine to perform, there has to be enough oil for the equipment to function. However, the amount of oil available is dependent both on the accumulator volume and the pump power. The former takes up space that could be used for other important systems, and the latter consumes more energy the larger it is. So, what is the most optimal solution? Does a more optimal solution even exist?

There is a more optimal solution! It has been shown that not only does the submarine perform adequately with a lower accumulator volume, it performs well with a lower pump flow as well. In fact, the pump flow can be as low as 50 % of what the system was designed for, and with that, a lower energy consumption. The results open up a world of possibility, all depending on the requirements of the submarine. It has shown that, the performance of the submarine can be enhanced either by changing the accumulator volume, or lowering the pump flow which directly affects the power consumption of the pump.

• author: Andersson, Anna
• supervisor: Marcus Thern
• organization: Department of Energy Sciences
• course: MVKM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• report number: LUTMDN/TMHP-20/5456-SE
• ISSN: 0282-1990
• language: English
• id: 9155224
• date added to LUP: 2024-06-13 14:19:01
• date last changed: 2024-06-13 14:19:01