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2 years ago

What is compression ratio of an Otto cycle? How does it affect the thermal efficiency of the cycle?

Engineering

1 answer:

GuDViN [60]2 years ago

6 0

Answer:

$r= \dfrac{V_1}{V_2}$

$\eta =1-\dfrac{1}{r^{\gamma-1}}$

Explanation:

Compression ratio:

Compression ratio is the ratio of volume in the cylinder.Generally it is denoted by r.

The compression ratio for Otto cycle is about 8 to 12.But the compression ratio of diesel engine is about 14 to 25.

So from the Otto cycle compression ratio can be define as

$r= \dfrac{V_1}{V_2}$

As we know that efficiency defines as the ratio of work out to the heat input.In the Otto cycle the efficiency is given as in terms of compression ratio r as

$\eta =1-\dfrac{1}{r^{\gamma-1}}$

Where γ is the heat capacity ratio.

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Answer:

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The work done by the turbine is:

$\dot W_{out} = \dot m \cdot (h_{in}-h_{out})-\dot Q_{out}$

The properties of the water are obtained from property tables:

Inlet (Superheated Steam)

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$h = 3008.2\,\frac{kJ}{kg}$

The work output is:

$\dot W_{out} = \left(1.1\,\frac{kg}{s}\right)\cdot \left(3425.9\,\frac{kJ}{kg} -3008.2\,\frac{kJ}{kg}\right) - 60\,kW$

$\dot W_{out} = 399.47\,kW$

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The flexural strength or MOR of a ceramic is 310 MPa. A block of the ceramic, which is 20 mm wide, 15 mm high, and 300 mm long,

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Answer:

$F=6200\ \text{N}\\$

Explanation:

In this problem you need to define the force that acts upon a beam in a 3 point bending problem. I put a picture of the problem taken from Wikipedia:

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$\sigma=\cfrac{3FL}{2bd^2}$

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