# Can Any Genius Answer My Questions .can Any Body.

1. Oct 8, 2005

### mohdfasieh

Question :

Find out thermal efficiency of a petrol engine having the following dimensions.Stroke length of piston is 75mm .Bore (internal diameter)=50mm and clearance colume is 21.3centimer cube.

plz plz tell me the solution plz if u are genius then plz answer this

2. Oct 8, 2005

### Danger

Although this isn't my area, I have serious doubts about there being anywhere near enough information there for an answer.

3. Oct 8, 2005

### mezarashi

It is not possible to find the thermal efficiency without any knowledge of the operating temperatures. It is far easier to get work done when there is a large difference in temperature between your two thermal reservoirs. You can deduce a relationship however between the efficiency and compression ratio.

The compression ratio is the ratio between the pistol's stroke volume over the clearance volume. If the compression ratio can be denoted by C, then

thermal efficiency = 1 - C^(1-k)
where k depends on the operating temperatures of the heat-work cycle.

4. Oct 8, 2005

### shaiqbashir

Have a look at this solution

Aslamoalaikum!

see how to solve this question.
Bore=D
Stroke=L
Displacement volume=$$\pi\frac{D^2}{4}L$$
Clearance Volume= 21.3 cubic millimeter

Now you can write

r= displacement vol / clearance vol

once you find the value of r

you can use the following equation

$$\eta=1-\frac{1}{r^{k-1}}$$

Last edited: Oct 9, 2005