tailieunhanh - GUIDELINES ON SHAFTING ALIGNMENT phần 2

Mô hình của sự châm biến Số Alignment tính Vòng bi động cơ trong mô hình Kể từ khi nhấn mạnh trong các tính toán liên kết sự châm biến truyền thống đã được đặt trên tránh tải cạnh trong vòng bi sterntube, ít chú ý đã được trả cho các vòng bi động cơ chính. trong thực hành thực tế của nhà máy đóng tàu khác nhau. | PART A GUIDELINES ON SHAFTING ALIGNMENT TAKING INTO ACCOUNT VARIATION IN BEARING OFFSETS WHILE IN SERVICE CldSSNK 3. Modelling of Shafting for Alignment Calculation Number of Engine Bearings in Model Since the emphasis in traditional shafting alignment calculations has been placed on avoiding edge loading in sterntube bearings little attention has been paid to main engine bearings. Figure shows the number of engine bearings taken into account in the alignment calculations with respect to the n in the actual practice of various shipyards. As can be seen from Fig. in some c M E bearings were incorporated into the calculation model although this varies fr Fig Howeve f engine cylinders aftmost three ccount in current unde ed apprec be ber of M E bearings in the calculation model has most three M E bearings while no noticeable effects can actions as shown in Fig. when the number of bearings is er engine. In particular the reactions of the second and third kably when the number of M E bearing changes from three to four ine full number M E bearings are taken into account the reaction of the overestimated while the reaction of the third aftmost M E bearing is M E bearings are incorporated into the calculation model. When the number to four the result is reversed namely the reaction of the second aftmost M E ated while the reaction of the third aftmost M E bearing is overestimated. The result is of M E be bearing is und close to the true value when the number of M E bearings is increased to five or more. Although the above result was based on a seven-cylinder engine the result is virtually independent of the number of cylinders although it was used as an example here. That is to say that when the reaction of a M E bearing needs to be accurately evaluated two more M E bearings beyond the bearing have to be incorporated in the calculation model. For example if the reactions of five aftmost M E bearings of a nine-cylinder engine have to be calculated precisely