Fig. 7 6th order transverse velocity amplitude of engine top-fore and aft

　

Vibration measurement was carried out during both engine shop test and site commissioning test and schematic diagram for measurement are shown as Fig. 8.

At first, the stiffness of engine shop foundation for X-mode vibration was checked with dynamic vibration absorber off condition which could be achieved by stopper between casing and inner mass. Fig. 8 is the vibration readings checked at casing with dynamic vibration absorber on and 25% engine load which shows 6th resonance separated into 90, 106 rpm. Unfortunately, the stiffness of actual foundation could not be measured in site test and so using vibration measurement results for similar project⁽⁷⁾, simulation was carried out. Comparison between calculation and measurement with no load is shown as Fig. 10 and measured value for each load is shown on Table 7. From these, it is found out that theoretical and measured values are well coincided for the resonance speed range, however not for non-resonance speed range due to H-moment from uneven cylinder load and torsional vibration.

　

Fig. 8 Schematic diagram for dynamic vibration absorber test on the diesel engine

Fig.9 6th order transverse velocity ampl. of engine top-fore and aft with 25% load at shop

　

Fig. 10 The 6th order transverse velocity ampl. of engine top-fore and aft W/O load at site

　

Table 7 The 6th order X-mode vibration of engine at 103.4 rpm(unit:mm/s)

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