ENGINE ROOM COATING

APPLICATION REPORT Prepared By Mert Doganli, Ph.D.

Istanbul Technical Uni. & Texas Tech Uni.

08.12.2018 info@novosim.com www.novosim.com

Summary This report is prepared to show the efficiency of coating application with regards to

vibrations and noise.

1. Introduction:

Impact tests are done on different parts of vessels in order to understand the response of the

structure for a given load. This data in general is called a „transfer function`. Since the output

levels (acceleration in our case) is normalized to applied force, the graph shows the sensitivity

of the part under testing for different frequencies.

With this information, all possible resonances of the structure are known and they are

independent of the applied load, meaning that a unit input is given and the response is formed

only by the dynamic characteristics of the part under study.

This report is an extension to the first report “Impact_Testing_Report_10122018.pdf”. The

main development is to illustrate the efficiency of the application in the engine room.

A 3 dimensional accelerometer is mounted on the bulkhead with and without Temp Coat-SR-

1000 application. Also, in another run, a 3D accelerometer is mounted on the engine

mounting structure to identify critical frequencies which may end up causing structure-borne

noise in the target locations.

Please check the following Figure (Fig.1) for the impact testing on a coated wall.

Figure 1. Impact testing in longitudinal direction of the yacht.

Figure 2 shows the impact testing to identify the lateral direction sensitivity.

Figure 2. Impact testing in lateral direction of engine support structure.

2. Results:

Figure 3 shows the results of “transfer functions” for the coated and uncoated wall up to 1000

Hz. In general structure-borne noise is estimated to be up to 250-300 Hz. Therefore, the

critical region is highlighted in the chart.

As shown in the figure (Fig. 3), a drastic improvement is achieved in reducing the vibration

levels in x-direction due to a unit input. This means, when the input from the engine takes

place, the unit input will raise to a certain level (will depend on mount stiffness, locations and

orientation and engine power) , and the acceleration levels will change according to the

inputs.

10000 100 200 300 400 500 600 700 800 90050 150 250 350 450 550 650 750 850 950

Hz

1.00

100e-6

1.00e-3

10.0e-3

100e-3

200e-6

300e-6

400e-6

600e-6

2.00e-3

3.00e-3

4.00e-3

6.00e-3

20.0e-3

30.0e-3

40.0e-3

60.0e-3

200e-3

300e-3

400e-3

600e-3

Lo

g

N/g

1.00

0.00

Am

plit

ude

F TF_1x+/1X+ (FRF)

F TF_1x+/1X+ (FRF)

Wall without coating

Wall with coating

g/N

Figure 3. Impact Testing Results for Coated and Uncoated Walls.

Next step during testing was to understand the noise levels generated due to the impacts.

Figure 4 shows the results of noise levels measured to due the impact. Under normal

measurement conditions, calculation of reverberation time would provide a better insight

about the effectiveness of the coating. The doors were not mounted at the time of

measurement but in any case the results were shared to have a back to back comparison.

300 10 202 4 6 8 12 14 16 18 22 24 26 28

s

Time

90.00

40.00

50.0

60.0

70.0

80.0

45.0

55.0

65.0

75.0

85.0

42.5

47.5

52.5

57.5

62.5

67.5

72.5

77.5

82.5

87.5

dB

(A)

Pa

1.00

0.00

Am

plit

ude

F Overall level mic:S (A) Mic_no_coating 1 Project1

F Overall level mic:S (A) Mic_coating Project1

Figure 4. Sound Pressure Levels during Impact Testing.

Figure 5. Articulation Index during Impact Testing (Higher Better).

Articulation index is a psycho acoustical metric which is used to understand the intrusion of

noise during listening and talking. In some cases, even though the levels may be similar, when

people try to talk to each other in the cabins, the frequency of the noise may match with the

hearing frequencies and may end up in a poor sound quality.

Another important metric which should be considered is the “reverberation time T60”.

Reverberation time is an important metric which is used to show the absorption level of

materials used in the room. With a better absorption, reverberation times decreases. Since the

doors were not mounted, the initial calculations are shared to give some idea. The calculation

is based on the duration of the signal to decrease 60 dB s. In general, the levels will reduce by

25-30 dB s and with the help of an extrapolation, Reverberation Time T60 can be calculated.

Please check Figure 6 for rough calculations. These levels should be recalculated for closed

rooms.

Type 30 dB 60 dB

Not Coated 1 sec. 2 sec.

Coated 0.91 sec. 1.82 sec.

Figure 6. Reverberation Level Initial Calculations.

Final stage is to highlight any sensitivity which may arise due to engine mounting structure.

Lateral direction seems to be the weakest direction and the results for this direction are shared

(Figure 7).

30.000.00 10.00 20.002.00 4.00 6.00 8.00 12.00 14.00 16.00 18.00 22.00 24.00 26.00 28.00

s

Time

99.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

5.00

15.00

25.00

35.00

45.00

55.00

65.00

75.00

85.00

95.00

Am

plit

ude

%A

I

1.00

0.00

Am

plit

ude

F Articulation Index mic:S Mic_coatingF Articulation Index mic:S Mic_no_coating 1

Figure 7. Engine Mounting Structure Sensitivities.

Figure 7 shows the results for possible vibration levels during motor operation. Since, engine

is a 6 cylinder inline engine, dominant orders will be 3 and 6. Depending on the max. rpm –

(estimated 2400 rpms) , maximum frequency excited will be 240 Hz (for 6th

order). Therefore,

a structural problem or an extra vibration level may be observed due to engine vibration.

3. Conclusions:

1) Transfer functions seem to be improve in critical frequency ranges with the

application of coating.

2) AI and Reverberation Time calculations should be repeated to have a better

understanding of the system when all enclosures are mounted. Rough, initial

calculations are shared.

3) Engine housing structure have resonances in operation range which may cause

durability (fatigue related) problems and higher vibration levels.

Customer : Volony Group

Project : Motor Yacht 30 mt

Location : Tuzla -İstanbul /TURKEY

10000 100 200 300 400 500 600 700 800 90050 150 250 350 450 550 650 750 850 950

Hz

0.10

100e-12

1.00e-9

10.0e-9

100e-9

1.00e-6

10.0e-6

100e-6

1.00e-3

10.0e-3

300e-12

2.00e-9

4.00e-9

20.0e-9

40.0e-9

200e-9

400e-9

2.00e-6

4.00e-6

20.0e-6

40.0e-6

200e-6

400e-6

2.00e-3

4.00e-3

20.0e-3

40.0e-3

Lo

g(A

)

N/g

1.00

0.00

Am

plit

ude

175.93207.38

F FRF 2:+Y/1:+Y (A)