# No. of cylinder calculaions

Discussion in 'Diesel Engines' started by Rhys2908, Dec 10, 2016.

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### Rhys2908Junior Member

I'm currently doing a question that asks to calculate the number of cylinders of a marine diesel engine.

Given the following equation, how can I achieve this?
Power at MCR = 6500 kW
Bore = 460mm
Stroke/Bore ratio = 4.2
Maximum brake mean effective pressure = 19bar
RPM = 129

Thank you

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### gonzoSenior Member

What is the thermal efficiency?

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### Rhys2908Junior Member

We don't have thermal efficiency but we have the following:
fuel consumption = 173 g/kWh
the air-to-fuel ratio is 51
the temperature of the exhaust gas exiting the engine is 237oC
the engine radiation losses percentage is 0.6%
the turbocharger compressor absorbed power is 42% of the engine brake power
the turbocharger mechanical efficiency is 96%
The used fuel lower heating value is 42700kJ/kg
The engine room temperature is 38oC

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### gonzoSenior Member

This may be one of those problems designed by academics. They make assumptions that they don't explicitly say. I always have a hard time with them. The thermal efficiency is the ratio between the actual power produced to the theoretical one.

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One assumes you realise when all else fails - Google is your friend?

It is imperial units but shows the methodology:

http://www.designchambers.com/wolfhound/wolfhoundRACHP.htm

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### Mr EfficiencySenior Member

The answer is eleventy. Give or take some.

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