Set 18 - E Pariksha MEK Motor MEO class 4 questions

1. The main function of tie rods in the construction of large, low speed diesel engines is to
stiffen the bedplate in way of the main bearings to increase the engine's longitudinal strength
accept most of the tensile loading that results from the firing forces developed during operation
mount the engine frame securely to the hull to prevent shaft coupling misalignment
connect the crosshead solidly to the piston rod

2. The fall in speed that occurs in a diesel engine equipped with governor, on increase of load is called:
Offset
Speed drop
Speed droop
Speed offset

3. What do you mean by surge limit of a turbocharger ?
Characteristic curve of a turbocharger
Portion of compressor characteristic curve which lies on the left side of the point of maximum pressure
A line joining all the points of maximum pressure on compressor characteristic curves , drawn at various speeds of operation
Maximum rpm limit of T/C above which surging will start

4. In case of 2-stroke marine diesel engines, the top part of the liner forming the combustion chamber experiences very high pressure induced mechanical stresses as well as high thermal stresses. Which of the following is a correctly designed liner for catering both the above stresses ?
Thick top portion with jacket cooling to take care of both the high mechanical and thermal stresses
Thick top portion to take care of high mechanical stresses while bore cooling to reduce thermal gradients
Thin top portion to reduce thermal gradients and hence thermal stresses while supporting ribs to take care of mechanical stresses
Thick top portion to take care of high mechanical stresses with jacket cooling combined with allowance for thermal expansion to minimize the thermal stresses

5. Which of the following is a reasonable statement about water washing of turbine side of a T/C ?
It leads to thermal shock and reduces the life of the T/C
It leads to thermal shock and not so effective as solid washing
If properly carried out keeping rpm , load ,temperature limits & other factors into account , it is quite safe and more effective than solid washing
It should never be carried out as most of the engine manufacturers recommend against the same

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