Investigation of energy losses in hydraulic shock absorbers of the BTR-4 armored personnel carrier suspension and assessment of the feasibility of using its recovery system

Abstract

Investigations of energy losses in hydraulic shock absorbers (HSA) of the BTR-4 armored personnel carrier while driving along three sections of unpaved roads and rough terrain, which met light, moderate and heavy road conditions, are presented. The speed range that was considered (20...64 km/h) covered the pre-resonant, resonant and non-resonant modes of motion. The studies were carried out by a numerical experiment using an experimentally verified mathematical model of the motion of a military wheeled vehicle along roughnesses, which was implemented in the DELPHI environment. The power was calculated, the HSA of the suspension of each wheel were absorbed, the instantaneous maximum values of these powers and the maximum vertical accelerations at the driver's seat and at the center, indicating the efficiency of the HSA and the level of ensuring the necessary smoothness. The total maximum power absorbed by the HSA of all suspensions, depending on the speed and road conditions, amounted to 2,1...19,5 kW or 0,57 ... 5,3 % of the maximum engine power, which indicates significant losses energy in the suspension vehicle BTR-4 and the feasibility of using its recovery system. HSAs of 1 suspension, which absorbed power from 1,2 kW (light road conditions, pre-resonance mode), 7,6 kW (heavy road conditions, resonance mode) and up to 6,8 kW (heavy road conditions, out-of-resonance mode), were the most loaded in all road conditions and driving modes, which amounted to 57,14 %, 42,22 % and 34,87 % of the total power, which was absorbed by the HSA of all suspensions. Thus, the energy recovery system can be used only on 1 suspension, since it is on them that on average accounts for half the energy that is absorbed by all HSAs. This will reduce the cost of this system, its weight and increase the reliability and performance of the suspension as a whole. Even taking into account the efficiency, such a recovery system will allow producing an amount of energy comparable to the energy of a regular brand 6301.3701 generator with a rated power of 4,2 kW. Studies have shown that the required smoothness of travel (maximum vertical accelerations at the driver’s place and, in particular, less than 3 g) in the entire speed range is provided only when driving in light road conditions, and, with the exception of the resonance mode (37,2...46,7 km/h) when driving in moderate traffic conditions. When driving in difficult road conditions, the required ride smoothness is not provided in the entire speed range, which indicates the need for a significant improvement of the BTR-4 suspension, including a significant, several-fold increase in the power absorbed by the HSA. In this case, the efficiency of the recovery system will also significantly increase, which, in turn, will solve another acute problem, namely, overheating and failure of the HSA. As a result of the studies carried out using the BTR-4 armored personnel carrier as an example, the feasibility of developing and using an energy recovery system of one type or another in the suspension of a military wheeled vehicle is substantiated, which, provided the suspension is comprehensively improved, can return up to 15...20 % of maximum power for future use engine. This will significantly improve such indicators of mobility as dynamism, smoothness and autonomy (power reserve), which is especially important in the case of using a hybrid power plant and electric transmission.