With the accelerated green and intelligent upgrading of China's inland waterway shipping, the traditional shaft propulsion systems equipped for conventional inland bulk carriers have many drawbacks such as large cabin space occupation, poor maneuverability, high energy consumption and complicated maintenance. They can hardly adapt to the complex navigation conditions of inland waterways featuring narrow channels, dense port areas and frequent berthing operations. As a medium and high-power marine electric propulsion equipment, the 300kW full-revolution pod propulsion unit boasts core advantages including modular integration, 360° omnidirectional propulsion, high efficiency and energy saving as well as flexible control. It precisely meets the power demands of thousand-ton class inland bulk carriers, becoming a preferred solution for the power upgrading of inland vessels and providing strong technical support for cost reduction, efficiency improvement and low-carbon transformation of inland waterway shipping.

I. Core Structure and Technical Principle of 300kW Full-Revolution Pod Propulsion Unit

The 300kW full-revolution pod propulsion unit is an integrated electric propulsion device designed and manufactured in strict accordance with the industry standard Pod-type Electric Propulsion System (T/CANSI47—2022). It abandons complex mechanical structures of traditional vessels such as long shaft lines, steering gears and stern tubes, and adopts an integrated architecture of underwater pod, above-water slewing mechanism and electric control system. Featuring compact overall structure and high modularity, it satisfies the installation requirements of inland vessels for lightweight design and low space occupation.

Its core components including high-power permanent magnet propulsion motor, reduction transmission mechanism and propeller are all integrated inside the streamlined underwater pod shell. Suspended at the bottom of the vessel stern via wing-shaped struts and equipped with an electro-hydraulic slewing drive system, the unit enables continuous 360° unrestricted rotation. It can realize all vessel maneuvers including steering, transverse moving and turning around without a steering gear. With a rated power of 300kW, it belongs to the high-power propulsion grade suitable for inland vessels, achieving a power density of 4.2kW/kg and a low-speed torque response time less than 120 milliseconds. It delivers stable and rapid power output, fully adapting to all operating conditions of inland bulk carriers including heavy-load navigation, low-speed sailing and precise berthing.

In terms of process and protection design, key structures are made of high-strength alloy materials with excellent moisture and corrosion resistance. The overall protection class reaches no less than IP56, which effectively prevents equipment damage caused by sediment erosion, water corrosion and water level fluctuation in complex inland water areas such as the Yangtze River, Beijing-Hangzhou Grand Canal and Pearl River. Meanwhile, the unit is fitted with an intelligent variable frequency electric control system to realize stepless speed regulation and accurate power adjustment, greatly improving the stability of power output compared with traditional diesel engine propulsion.

II. Existing Pain Points of Traditional Propulsion Systems for Inland Bulk Carriers

Currently, most mainstream 1000–3000 ton-class inland bulk carriers in China adopt the traditional propulsion mode combining diesel engine, long shaft line and steering gear, which has exposed numerous limitations after long-term operation in inland navigation scenarios. Firstly, the complex traditional shaft line runs through the cabin and occupies a large amount of effective cargo hold space, reducing the economic benefits of vessel transportation. Components such as shaft lines, bearings and steering gears suffer severe mechanical wear, leading to high daily maintenance costs and long downtime for repairs, which impairs vessel operational efficiency.

Secondly, inland waterways are generally characterized by numerous narrow bends, dense vessels in port areas and complicated water flow. Traditional propulsion systems feature large turning radius and delayed control with poor maneuverability, making vessel turning, berthing and evasion difficult. This easily causes navigation congestion and prolonged berthing time, and raises navigation safety risks. Thirdly, traditional mechanical propulsion has high transmission loss and low propulsion efficiency with insufficient energy utilization, resulting in high fuel consumption, excessive carbon emissions and noise pollution. It fails to comply with current national policies on carbon peaking and carbon neutrality as well as requirements for green navigation of inland waterways. In addition, traditional power systems generate intense vibration and noise, which may cause fatigue damage to hull structures during long-term operation and shorten the service life of vessels.

III. Application Advantages of 300kW Full-Revolution Pod Propulsion Unit on Inland Bulk Carriers

(1) High Efficiency and Energy Saving to Improve Navigation Economy

Adopting the direct electric drive mode, the 300kW full-revolution pod propulsion unit eliminates mechanical transmission loss of traditional shaft lines. Combined with the streamlined hydrodynamic structure, its propulsion efficiency is 8%–12% higher than that of conventional shaft propulsion systems, which greatly cuts energy consumption per voyage. Aiming at the operating characteristics of inland bulk carriers including frequent start-stop, low-speed cruising and variable-load sailing, the intelligent variable frequency control system dynamically matches power output to navigation demands and avoids energy waste caused by high idling speed of traditional diesel engines. Under the same cargo capacity and sailing distance, it effectively reduces power or fuel consumption, and remarkably lowers long-term operational costs, fully meeting the core demand for low-cost operation of inland waterway shipping.

(2) Flexible Control to Adapt to Complex Inland Navigation Conditions

Its core strength lies in 360° omnidirectional unrestricted propulsion, which can deliver thrust at any angle and completely reform the conventional one-way propulsion and gear-dependent steering mode of traditional vessels. It enables vessels to turn around in-situ, move transversely and sail at a stable low speed when navigating narrow inland channels, evading other vessels in dense port areas and berthing precisely at docks. The turning radius is greatly reduced and vessel maneuverability is significantly enhanced. Compared with vessels equipped with traditional propulsion systems, the berthing time is shortened by more than 30%, boosting port turnover efficiency. It perfectly adapts to the operational features of inland bulk carriers with complex routes and frequent berthing, and also reduces potential safety hazards such as collision and grounding.

(3) Cabin Space Saving to Increase Cargo Capacity

The 300kW pod propulsion unit adopts external installation. All core propulsion components are integrated into the external pod structure of the hull without occupying interior cabin space, completely saving the space occupied by traditional long shaft lines, steering gear rooms and transmission equipment. For inland bulk carriers, the effective cabin capacity is maximized, directly increasing cargo volume and payload. Without changing the main dimensions of vessels, the transportation economic benefit of single vessel is effectively improved, conforming to the profit-oriented operation mode of inland bulk carriers. Meanwhile, the modular structure enables simple installation without complex hull perforation and shaft alignment work, which greatly reduces the difficulty of vessel construction and retrofitting.

(4) Green and Low Noise to Comply with Low-Carbon Shipping Trend

Powered purely by electricity, the 300kW full-revolution pod propulsion unit can be matched with clean energy power systems such as ship lithium batteries and generator sets to achieve zero exhaust emissions during navigation, thoroughly solving the problems of black smoke and waste gas pollution from traditional diesel engines. It satisfies environmental protection requirements for navigation in special water areas including inland ecological waterways and drinking water source protection zones. In addition, the direct motor drive features low vibration and noise, which not only minimizes disturbance to inland water ecology but also improves the working environment for crew members. Furthermore, the integrated structure brings low wear rate and failure rate as well as long maintenance cycles, substantially cutting later operation and maintenance costs and downtime, and extending the annual operating hours of vessels.

IV. Practical Application Adaptability and Optimization Solutions

The 300kW power rating is precisely tailored for mainstream 1000–3000 ton-class inland bulk carriers. It can be installed in single unit or dual parallel units to meet the thrust and speed requirements of vessels of different tonnages. Targeting the features of inland water with high sediment content and drastic water level variation, the streamlined design of the pod shell is optimized to reduce sediment adhesion and water flow resistance. Equipped with anti-winding and anti-wear protective structures, it effectively prevents entanglement by aquatic weeds and sundries, ensuring long-term stable operation in complex inland water areas.

In terms of adaptation for new ship construction and old ship retrofitting, the propulsion unit features strong modular compatibility and requires no major modification to hull structures. It can be directly installed on newly-built vessels, while the power upgrading of old bulk carriers requires short construction period and low retrofitting cost. When combined with the intelligent ship control system, it realizes real-time monitoring of propulsion status, automatic fault alarm and intelligent power regulation, keeping pace with the intelligent upgrading trend of inland vessels and facilitating the transformation of inland bulk carriers from extensive traditional operation to efficient, intelligent and green operation mode.

V. Application Prospect and Summary

Against the backdrop of green transformation, intelligent upgrading and increasingly stringent environmental policies for inland waterway shipping, traditional propulsion systems with high energy consumption and poor flexibility can no longer meet market demands. Boasting comprehensive advantages of high efficiency, energy saving, flexible control, high cabin utilization rate, environmental friendliness and convenient maintenance, the 300kW full-revolution pod propulsion unit effectively solves the core operational pain points of inland bulk carriers and fits the operating conditions and upgrading direction of mainstream inland bulk carriers.

With the full localization and maturity of domestic pod propulsion technology, the cost of full-revolution pod propulsion units of this power level keeps decreasing while their reliability and stability are greatly improved, laying a solid foundation for large-scale promotion and application. In the future, the 300kW full-revolution pod propulsion unit will be widely applied in the construction of new inland bulk carriers and the retrofitting of old vessels. It will effectively enhance the efficiency, safety and environmental performance of inland bulk cargo transportation, and provide solid technical and equipment support for the high-quality development of China's inland waterway shipping and the construction of a green low-carbon water transportation system.