Browse Publications Technical Papers 2005-01-2531
2005-05-16

NVH Experiments and Analyses for an Single Cylinder Engine Model Assembled with Tap-Bolts and with Through-Bolts 2005-01-2531

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, with bore sizes of 100mm. Each engine model consists of a cylinder head, a cylinder block and a bedplate. Each has the same size of 150mm × 150mm, with different heights of 100mm, 200mm and 80mm, respectively. By choosing 112 measuring points on the structure surfaces, we performed a series of impact tests for the following cases,
  1. (a)
    The cylinder head and the bedplate were fastened to the cylinder block by two sets of ISO M10 Tap-bolts, each with the lengths l1=117mm and l2=97mm.
  2. (b)
    The cylinder head and the bedplate were fastened to the cylinder block together by a set of ISO M10 Through-bolts of grip length l3=380mm.
From a series of acceleration measurements, it was found that
  1. (1)
    Significantly dominant bending nodes are induced in the X-Y plane, which is vertical to the crankshaft center line.
  2. (2)
    13 of the resonance peaks appeared in the frequency range below 7000 Hz for the case (a), whereas only 6 for the case (b).
  3. (3)
    Compared to the 3143Hz of the lowest fundamental natural frequency for the case (a), a higher value of 3450Hz appeared for the case (b).
  4. (4)
    Significant reduction of the engine model surface vibration is caused for the case (b).
To investigate the reasons of such differences, the engine structure model was idealized as a set of beam elements consisting of variable cross-sections, to calculate the fundamental natural frequency, by Rayleigh's method. By applying 38 beam elements, and 3 sets of bolt joints each consisting of bolt and clamped member, we could calculate the fundamental natural frequencies successfully. Finally, we found that the higher natural frequencies and excellent NVH characteristics are caused by the larger values of flexural rigidity for the case (b).

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