Turning Moment Diagram for a Four Stroke Engine

What is the Turning Moment Diagram?

The turning_moment diagram is the plot between the turning moment of the crank to the position of the crank. It is also known as the Crank-Effort Diagram since it represents the crank-effort for various positions of the crank.

Turning Moment Diagram

As we said above the turning_moment diagram is the plot between the turning moment of the crank to the position of the crank. We can draw this by the following formula

Where

• F_P= Pison effort
• θ = Crank angle
• r = Crank Radius
• n = crank ratio (Ratio of connecting rod to the stroke or the radius of the crank)

Let us consider a turning moment diagram of a Four-stroke engine and discuss in detail about it.

Turning Moment Diagram for a Four Stroke Engine

Following is the Turning_moment Diagram of a Four Stroke Internal-combustion Engine. As we already know that the four-stroke engine will have one power stroke (working stroke), for every two revolutions of the crank (720°).

• During the suction stroke, the pressure inside the cylinder is less than the atmosphere, that is the reason for the negative slope in the suction region in the above graph.
• During the compression, the work is done on the gasses so it is also represented under the negative slope.
• Under the expansion/power stroke the fuel combustion will happen and the piston moves downward and produces some mechanical work on to the crank. This is work done by the gasses onto the piston. As shown above, there is a huge positive loop shown this area of the graph represents work done by the gasses.
• And further, the combustion particles will exhaust, during this stroke, the work is done on the exhaust gasses, therefore there is a negative slope represented.

In the above graph, the effect of the inertia forces also considered. Since there are the positive loops present in the suction and the exhaust graph regions shown above.

This is the turning_moment diagram for a Four Stroke Engine.

Conclusion

We have discussed the turning_moment diagram for the four-stroke engine and also we have given the formula how to draw one. If you have any further thoughts on this topic, let us know in the comment section below.