| Abstract [eng] |
Rowing is one of best kinds of exercises having a great impact on sportspersons physical condition, including muscle strength and endurance. There are several types of rowing machines available and hydraulic rowing machine is one of most efficient kind keeping in mind its budget, compactness and reliability. Hydraulic cylinders connected to the levers imitating oar handles are used in such machines to generate the resistance force during exercising. This force is proportional to the speed of cylinder compression/extension (their piston insertion/extraction) in turn depending on intensity of exercising. Mechanical energy of the athlete applied on the cylinder during exercising is converted to the thermal energy of the cylinder, so it tends to heat after certain period of continuous functioning, then the viscosity of fluid circulating in the cylinder and correspondingly resistance force decrease. The aim of this master’s thesis is to improve the performance of a hydraulic cylinder of the lever type rowing machine by improving its cooling rate. Therefore the analysis of design, regimes and principles of operation of the hydraulic cylinders, heat transfer mechanisms and cooling systems was carried out. The thermal loads acting the present design cylinder of rowing exerciser and excessive heat to be dissipated were determined by computational analysis of its thermal state. Two types of cooling devices (having longitudinal and circular cooling fins) mounted onto the cylinder and increasing the rate of heat transfer to the environment by increasing convection were designed and their efficiency was evaluated by means of numerical simulation. |
