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1st & 2nd order

1st & 2nd order

1st & 2nd order

(OP)
1.what is the first order, second order in terms of NVH?

2.In auto industry, what do you mean by " any order peak at certain frequency at certain rpm?"

could you just explain me details.

3.does this statement is correct - If vehicle is at 1000 rpm at idele means it is at 17 HZ?

Please rectify it if necessary.

RE: 1st & 2nd order

1) Order is the frequency divided by the rotating frequency of the system. To keep track of the different rotational speeds we often append a letter, so 3E means 3 times engine rotational speed, 2W means twice wheel speed.

2) If you have a waterfall plot look up the line for a given rpm. It is asking for the highest peak along that line

3) At 1000 rpm, first order s at 17 Hz, 2nd order is at 33 Hz, 3rd order is at 50 Hz, 2.5 order is at 2.5*1000/60 Hz etc

 

Cheers

Greg Locock

RE: 1st & 2nd order

(OP)
Thanks for your reply,
Could you explain me the physical significance of 1st,2nd order frequency at 1000 rpm?

RE: 1st & 2nd order

On an engine first order is typically out of balance of the crankshaft etc.

Second order is typically caused by the non sinusoidal motion of the pistons, due to the L/r ratio, which rarely cancel internally except with straight six or boxer engines.

Cheers

Greg Locock

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