Executive Programs

Workshops

Projects

Blogs

Careers

Student Reviews

More

Informative Articles

Find Jobs

We are Hiring!

All Courses

Choose a category

All Courses

All Courses

19 Jan 2023

# Working Mechanism of a Four-Stroke Engine

Skill-Lync

Internal combustion engines are very important to prime movers in automobiles, power plants, and standalone applications. These are heat engines that convert fossil fuel energy into mechanical energy by thermodynamic cycles. The most important thermodynamic cycles that these engines are working on are the Otto and Diesel cycles. Otto cycle is used in petrol or gasoline engines, and the diesel cycle is used with diesel fuel and biodiesel fuel. The basic construction of an engine consists of a piston and a cylinder assembly. The whole assembly is an inversion of the four-bar linkage and is known as the slider crank mechanism as shown in the image below.

Stroke is defined as the motion of the piston from the topmost point of its motion(TDC) to the bottommost point of its motion(BDC). Both the cycles referred to before are four-stroke cycles. That means to complete one thermodynamic cycle, the piston has to complete four strokes inside the cylinder.

## The Otto Cycle

In the Otto cycle, there are four strokes to be required by the piston to complete on cycle. The P-V diagram of the Otto cycle is shown in the image below.

Also, the different positions of the piston for the four strokes are given in the image below.

In the above figure, we can see the four strokes clearly. The P-V plot also shows the four strokes of the piston. Also, this engine has a spark plug which implies it uses gasoline or petrol as fuel. So it works on the Otto cycle, which uses a spark to ignite the fuel. Now let's look at the different strokes in the Otto cycle.

Intake stroke(0-1): In this Stroke of the piston the Intake valve is open, and the piston moves from TDC to BTC. That will create a suction in the cylinder, which will draw air from the atmosphere. This air will draw fuel from the carburettor through a nozzle, and the fuel is mixed with the air. This mixture of air and fuel is known as a charge. This intake charge is then drawn into the engine.

Compression stroke(1-2): In this stroke, the piston moves from BDC to TDC, and the intake and exhaust valves are closed. This will increase the pressure and temperature inside the cylinder. At the end of this stroke, the spark plug ignites and starts the combustion.

Power stroke(3-4): The process from 3-4 is known as the power stroke or the expansion stroke. During this stroke, the piston moves from TDC to BDC again. The high pressure generated from the combustion will push the piston downward and produce an output torque.

Exhaust stroke(4-1): In this stroke, the burnt charges will be expelled from the cylinder. The exhaust valve remains open in this stroke. The piston moves from TDC to BDC, and the piston pushes on the burnt gas out of the cylinder.

Processes 2-3 and 4-1 are heat addition and rejection, respectively. Heat addition is the combustion, and heat rejection is the blowdown process.

The valves are operated by using a camshaft which rotates at half the speed of the crankshaft. The camshaft has cam lobes that push the valves at the right moment.

## The Diesel Cycle

The diesel cycle is very similar to the Otto cycle. The only difference is in how the combustion process occurs inside the cylinder. Here the combustion is started by injecting fine fuel spray into the hot compressed air inside the cylinder. Instead of a spark plug, we will have an injector at the top of the cylinder head.

In the four-stroke diesel cycle, all four strokes as mentioned for the Otto cycle, are present. The only difference is in the fuel induction and fuel ignition.

Author

Author

Skill-Lync

Related Blogs

Shock tube simulation

Learn how to render a shock-tube-simulation and how to work on similar projects after enrolling into anyone of Skill-Lync's CAE courses.

10 May 2020

Design of Frontal BIW enclosure of a car (Bonnet)

In this blog, read how to design the frontal BIW enclosure of a car (Bonnet) and learn how Skill-Lync Master's Program in Automotive Design using CATIA V5 will help you get employed as a design engineer.

10 May 2020

What is Tetra Meshing?

Tetrahedral is a four- nodded solid element that can be generated through the tria element by creating a volume and also through the existing volume of the geometry. These elements are used where the geometry has high thickness and complexity. The image attached below is a representation of a Tetra element. The Tetra element will have 4 triangular faces with four nodes joining them together

02 Aug 2022

Realizing Connectors In HyperMesh

A connector is a mechanism that specifies how an object (vertex, edge, or face) is connected to another object or the ground. By often simulating the desired behaviour without having to build the precise shape or specify contact circumstances, connectors make modeling simpler.

03 Aug 2022

Mesh Sizing In Ansys Workbench

One of the most crucial processes in carrying out an accurate simulation using FEA is meshing. A mesh is composed of elements that have nodes—coordinate positions in space that might change depending on the element type—that symbolise the geometry's shape.

04 Aug 2022

Author

Skill-Lync

Related Blogs

Shock tube simulation

Learn how to render a shock-tube-simulation and how to work on similar projects after enrolling into anyone of Skill-Lync's CAE courses.

10 May 2020

Design of Frontal BIW enclosure of a car (Bonnet)

In this blog, read how to design the frontal BIW enclosure of a car (Bonnet) and learn how Skill-Lync Master's Program in Automotive Design using CATIA V5 will help you get employed as a design engineer.

10 May 2020

What is Tetra Meshing?

Tetrahedral is a four- nodded solid element that can be generated through the tria element by creating a volume and also through the existing volume of the geometry. These elements are used where the geometry has high thickness and complexity. The image attached below is a representation of a Tetra element. The Tetra element will have 4 triangular faces with four nodes joining them together

02 Aug 2022

Realizing Connectors In HyperMesh

A connector is a mechanism that specifies how an object (vertex, edge, or face) is connected to another object or the ground. By often simulating the desired behaviour without having to build the precise shape or specify contact circumstances, connectors make modeling simpler.

03 Aug 2022

Mesh Sizing In Ansys Workbench

One of the most crucial processes in carrying out an accurate simulation using FEA is meshing. A mesh is composed of elements that have nodes—coordinate positions in space that might change depending on the element type—that symbolise the geometry's shape.

04 Aug 2022

Book a Free Demo, now!

Related Courses

Ultimate SOLIDWORKS Course
4.8
17 Hours of content
Design Domain
4.8
203 Hours of content
Design Domain
Recently launched
0 Hours of content
Electrical Domain
Recently launched
10 Hours of content
Cae Domain
Showing 1 of 4 courses