Justification of the parameters of the propellers of a towing device for the transportation of small-sized timbertransport units

Economically viable development of the main reserves of wood raw materials is often only possible if it is delivered from remote forest areas via a network of medium and small rivers. Due to shallow depths and short navigation periods, the use of existing vessels on them is generally impossible or economically impractical. The problem can be solved by using the proposed relatively cheap and simple shallow draft towing device, which is delivered to the timber place of departure by road transport. The work was carried out with the aim of obtaining the parameters of the propellers of the proposed device, which would reduce towing costs under the specified conditions. The absence of idle speed allows propellers to be designed specifically for towing mode, which increases their operating efficiency in this mode. In order to maximize the use of flow energy, it was decided to tow units having high resistance at a minimum speed that ensures their control. At this speed, efficient use of engine power and obtaining maximum thrust is achieved by using propellers with a particularly small pitch ratio. This involves increasing their diameter and rotation speed. In the case under consideration, the diameter of the propellers is limited by the depths along the route and, unlike ships, is not directly related to the hull draft. With a power of 125 kW, the most suitable engine for the proposed device, the use of one small diameter propeller (0.6-0.8 m) at a towing speed of 4.5 km/h suggests the occurrence of cavitation, insufficient strength, or low thrust. With two propellers, their diameter can be from 0.6 m, and the thrust increases significantly. For the proposed device, graphs and empirical formulas have been obtained, which make it possible to easily determine the parameters of propellers under various operating conditions in practice. Changing the propellers diameter from 0.6 to 1.0 m results in an increase in the total thrust from 15.0 to 21.3 kN.

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