The air-cooled mobile screw compressor driven by diesel engine is a common general-purpose machine for field work. The common structure of this type of machine is: the compressor drives the male rotor through the coupling to drive the speed increasing gear, and the fan is transmitted from the gear on the extension end of the female rotor to the fan shaft, and the fan shaft is equipped with a fan coupling. In the section, the fan is fixed on the fan coupling by screws (KL diagram D. Under this structure, the unit often has a series of problems such as breakage of the cooling fan blade, which seriously affects the normal use. This article deals with this problem in a 10mVmin exhaust. On the screw compressor driven by the diesel engine, the in-depth test and analysis were carried out, and finally a solution was proposed.
2 Analysis of the problem In the normal working condition test of 500h in the early stage of the test, the unit is in good condition, but when using the actual working conditions, the following problems occur continuously: what causes the occurrence of these problems, the calculation and analysis, and further simulation test Verification, found in Table 1 Table 1 serial number phenomenon preliminary analysis fan gear broken gear material performance is insufficient. Fan shaft key breaks the cooperation between the fan shaft and the gear mounting part. The strength of the broken shaft of the fan shaft is not enough. The cooling fan blade breaks the fan blade. The lack of preliminary analysis of material and quality is not the root cause. Taking the fan shaft fracture as an example, the measured fan shaft output torque is 39.m, and the shaft design allowable torque is 123N*m. It is reasonable to say that the shaft is not broken; what is the force to make the shaft break after repeated observation, It has been found that, in continuous and stable operation, moving parts such as shafts and blades are operated under the conditions of allowable strength without problems.
When the unit is stopped, the fan is almost insufficient from about 200r/min to stop. 8s time to complete, according to the calculation formula of braking torque r T = JWm test, the total moment of inertia of the load iron, drive shaft, etc. is about 0.6kg 'm2, angular acceleration is about 262 rad / s2, at this time The braking torque is approximately 157 N*m, which has exceeded the allowable torque of the shaft. The braking torque acting on the blade also exceeds the allowable stress at the root of the blade.
The impact force of the diesel engine during start-up or stoppage is large, especially in the last turn of the diesel engine stop, from the flameout to the cylinder and the gas rebounds, which gives the fan a large reverse impact force, so the internal combustion engine is indirectly applied to the wind. A large braking torque of the blade and the shaft, which is the root cause of the series of problems. The conventional cooling fan transmission structure is directly fixed on the half coupling, which is a rigid connection and has no buffer for some instantaneously varying loads. Therefore, when the diesel engine is started and stopped, the impact torque of the instantaneous speed change is directly transmitted to the fan, and the instantaneously varying impact torque generates a large instantaneous acceleration to the fan, so that the instantaneous force of the fan blade is increased several times and is easily damaged. . It also has the same effect on the relevant parts, which shortens the service life accordingly.
From the calculation formula of braking torque r: r=/r, it can be found that there is no big change in the moment of inertia of the load. To solve the problem that the braking torque is too large, causing the blade or shaft to yield to fracture, only the angle is lowered. Acceleration, the original rigid connection system was changed to a flexible connection system. If the belt drive is used, this force can be eliminated, but the structure changes greatly, the workload is large, and the arrangement is not ideal. If the transmission is through the elastic coupling, the fan is connected by the cantilever and the other end is unsupported. After a groping attempt, a single-point cantilever flexible coupling was designed.
3 Solution For this problem, we used a single-point cantilever flexible coupling. The connection of this new structure is that the drive torque is directly connected to the half coupling, the fan is connected to the floating connection, and the power of the coupling is transmitted to the floating connection through the elastomer, see.
The single-point cantilever elastic coupling is more worried than the previous rigid cantilever connection system: the torque is transmitted through the elastic body, and the cushioning performance is good; the change of the instantaneous moment of the Q does not cause too much force to the fan; The system has little influence on the force change, and the system has a long service life and high system reliability; (4) axial positioning with spring, no axial displacement, high positioning accuracy, no sloshing, and low wear.
4 Conclusion In the diesel engine-powered fan drive system, the elastic connection can effectively absorb the instantaneous impact force, improve the maximum force of the fan, and buffer the impact force generated by the instantaneous speed change of the diesel engine starting and stopping, so that the fan The impact of the related parts is reduced and the life is extended. Can also be used for other occasions similar to working conditions. The product has been put into mass production until now, the performance is stable, the work is reliable, the user's actual application is better, the life of the fan and its related parts is greatly prolonged, and no damage has been found so far. The single-point cantilever flexible coupling has applied for national patent
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