Project 885 / 885M - Propulsion
A characteristic feature of the Russian 4th generation nuclear submarines was to become a new type of power plant. Especially for new projects, at the end of the 1980s, a new KTP-6-85 water-water steam production unit (PPU) was developed with the KTP-6-185SP reactor (sometimes the name KPM is erroneous) with a thermal capacity of about 200 MW with production in the Engineering Design Bureau imeni. I.I.Afrikantova.
A distinctive feature of the new type of reactor was the so-called integral monoblock design in which the reactor itself and its first cooling circuit are mounted in a single housing. This solution allows excluding large pipelines from the design of the PUF (their maximum diameter was reduced from 675 to 40 mm) and, thereby, facilitates the natural circulation of the coolant in all operating modes. The latter is one of the key criteria for the low noise of the entire boat, eliminating the need for continuous operation of circulation pumps and reducing by an order of magnitude the energy consumption of the reactor for its own needs (higher overall efficiency). Such a PUF is much more compact than the previous generation, easier to maintain, more secure and reliable.
At the same time, the integration of all systems and components of the reactor in a single housing negatively affects the maintainability of the installation due to their low availability. Therefore, the developers of the 4th generation reactors were tasked with ensuring their maintenance-free service life throughout the life cycle of the boat. The reactor core is designed so that it is necessary to reload it half as often as in similar installations of 3rd generation boats.
Design solutions for the new generation of PUFs were tested at the KV-2 ground-based research bench with the TM-4 and KTM-6 experimental reactors in Sosnovy Bor (the theme is “Canyon-C.1”), and in 1996 the reactor was officially approved for serial production. However, it never appeared on the lead submarine of the 885 project. The difficulties associated with the production of the block steam turbine installation led to the fact that in the process of redesign, the Severodvinsk boat received a block PPU OK-650V with a previous generation VM-11 reactor with a thermal capacity of 190 MW, which significantly reduced the combat potential of the submarine even despite the whole series of other decisions taken at it to reduce the noise of the main power plant.
It is known that OKBM imeni. I.I.Afrikantova developed a new type of reactor under the designation KTP-7I (OCD "Phoenix"). It is possible that it is intended for installation on later serial boats of Project 885M, and there are two possible fundamental options for this installation. According to one version, it is a question of further evolutionary development of monoblock reactors with bringing the core life to 30 years or more, which will allow their use without refueling throughout the entire life cycle of a nuclear submarine. For example, all foreign developers of similar equipment go along this path.
According to another version, the new installation can be based on the principle of superheating of steam directly in the core (a type of so-called “boiling” reactor) and is designed to replace today's water-cooled reactors. In this case, if it is possible to solve a number of design difficulties associated with the development of such a steam generating plant, in particular, with ensuring radiation safety, the customer will receive a single-loop reactor with even greater efficiency and even more compactness compared to previous developments. However, as expected, this technology is promising primarily for the 5th generation of nuclear submarines.
A special feature of the Mirage steam turbine unit developed by the Kaluga Turbine Plant, which was originally intended for Ashen, was its block layout with a high degree of integration of all elements. In addition, it had to provide both high-speed running under turbo-gear units with a reduction gearbox and a drive to the main shaft, and a “creeping mode” driven by a propeller motor, which, in turn, was powered by autonomous turbogenerators. GTZA, which is one of the main sources of noise on the nuclear submarines, remains disconnected. Such hybridization of the power plant made it possible to make full use of the fact that the new type of reactor operates in the same heat release mode at all operating modes. Also, the design of the gearbox has been greatly simplified.
Unfortunately, the financial problems of the KTZ plant practically stopped all work on it during the 90s. In 2006, the Mirage vocational school with a rated power of about 43,000 hp bench tests have already passed and, apparently, it was the start of its serial production that will allow starting from the second boat of the series to fully utilize the potential laid down in Project 885. In the absence of a new anti-tank missile, the OK-9VM block anti-tank missile was used at Severodvinsk Sapphire-VM ”with a capacity of 43,000 hp, previously used on boats of the 945th and 971th projects. Both units provide a maximum underwater speed of about 31 knots. (surface speed - 16 knots.) Changes in the configuration of the energy compartment equipment required additional corrections in the design of the Severodvinsk submarine, such as redesigning the bulkheads and installing a recess in the area of the propeller shaft line.
Great attention in the design of the boat was paid to reducing the level of underwater noise it produces. For this, the foundations of all critical nodes are equipped with an active noise suppression system (SAG) based on piezocrystalline drives. Discrete low-frequency noise components were also reduced due to the development of new types of non-combustible spiral-torsion shock absorbers to replace the previously adopted rubber-cord ones. In the future, on the boats of the series, mass introduction of composite structural elements with high strength, low weight and damping properties is expected. These include various vibration-absorbing honeycomb frames, laminated beams, pillars, elements of pipelines and air ducts that reduce vibration noise at individual frequencies by 10-30 dB.
Contrary to the widespread assumption, neither Severodvinsk nor Kazan have a water-jet main propulsion, but are equipped with a seven-blade propeller of a composite structure with composite damping of the blades, which allows reducing the total noise level by 2-3 dB. As a backup propulsion system for travel at speeds up to 4.5 knots. GAP-300 electric motors with a capacity of 300 kW each are provided in folding columns in the aft and bow parts of the hull. They are also used as thrusters. Initially, this type of RDK was used on the Project 971 nuclear-powered submarines. For the Project 885M, a new low-noise ring-type RDK is currently being developed on the Lomovik topic.
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