| If the lubrication system of a helicopter reducer is compromised, its gears and bearings will be at non-lubricating oil work state, which quickly causes the reducer to be damaged, thereby resulting in disastrous consequences. For this,many countries require helicopters to be able to maintain flight operation for 30 to 60 min in an oil-out condition. Oil/mist lubrication and oil/air lubrication require a smaller quantity of oil, which can reduce the quality of the helicopter’s performance. Because compressed air can remove a great deal of heat, oil/mist lubrication and oil/air lubrication have good anti-wear effects. Until now, the study of extreme-pressure and anti-wear additives has been limited to full lubrication, such as dip lubrication, whereas oil/mist lubrication and oil/air lubrication that contain extreme-pressure and anti-wear additives have not been given any attention. For this study, we adopted oil/mist lubrication and oil/air lubrication that contain extreme-pressure and anti-wear additives for gear lubricating oil of ammonium thiophsphonate(T307)、sulphurised isobutylene(T321)、parathion ding simbo alkyl zinc salt(T202)and ashless organic phosphonate(T391)in an effort to discover the best anti-wear additive, and the best way it could be employed using a minimal quantity of lubrication. In order to reduce the cost of testing, a pin-on-disc friction test was used instead of a gear transmission.The friction pairs used in the study were made of 12Cr2Ni4 A. The upper specimens were small cylinders with dimensions of Φ10mm×4mm, and the lower specimens were disks with dimensions of Φ98mm×4mm. The friction pair surface was carburized to a depth of 0.8-1.0mm, and the surface hardness was not less than HRC60. The friction device was a UMT-Ⅱ test machine. The test load was 100 N. The cylindrical surface of the upper specimen and the lower disk specimen formed a line of contact, and the relative sliding velocity was 2.62 m/s. The air pressure of the oil/mist lubrication was 0.1MPa, and the air pressure of the oil/air lubrication was 0.4MPa. During the friction test, when the friction coefficient increased rapidly, oil/mist or oil/air was jetted at the entrance of the friction area. Each period of the test for the minimum quantity of lubrication lasted 45 min.The results show:(1)Extreme pressure and anti-wear additives have different adaptabilities in different aeronautical oils. For example:various 2% additives of T307、T321、T202 and T391 were mixed with 926 and DOD-L-85734 aeronautical oils to make 45 min oil-mist lubrication experiments to 12Cr2Ni4 A steel tribo-pair. The best effect of resistance wear was 926 aeronautical oil containing 2%T202 and DOD-L-85734 aeronautical oil containing 2%T391.(2)The anti-wear effect of oil/air lubrication containing extreme pressure and anti-wear additives is clearly superior to that of oil/mist lubrication, as oil/air lubrication containing extreme pressure and anti-wear additives consumes less oil and produces less wear and a lower temperature rise.(3)Each kind of extreme pressure and anti-wear additives has the best anti-wear content. To DOD-L-85734 aeronautical oil, the best anti-wear content of T202 and T391 was 2%, but the best anti-wear content of T307 and T321 was 1%. All of the four best anti-wear contents show excellent anti-wear effect, and the best anti-wear effect is 2%T391.The technology of oil/air lubrication containing extreme pressure and anti-wear additives is a feasible way to improve the oil-out operational ability of a helicopter transmission system. As an area of further study, testing of oil/air lubrication that contains extreme-pressure and anti-wear additives will need to be performed for helicopter reducer gears. |
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