Piston Assembly MBD Simulation of Different Piston Head Size Using Solidworks
Motion Analysis Of Piston Assembly Using Solidworks
Aim:- To perform motion analysis of piston assembly for getting linear displacement of piston and angular velocity of crank.
Theory :-
A two-stroke (or two-cycle) engine is a type of internal combustion engine which completes a power cycle with two strokes (up and down movements) of the piston during only one crankshaft revolution. This is in contrast to a "four-stroke engine", which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.
Two-stroke engines often have a high power to weight ratio, power being available in a narrow range of rotational speeds called the "power band". Compared to four-stroke engines, two-stroke engines have a greatly reduced number of moving parts.
Phases Of Stroke Engine:-
Commonly used engine phases/strokes (i.e. those used in a four-stroke engine) are described below. Other types of engines can have very different phases.
Induction/Intake stroke
The induction stroke is the first phase in a four-stroke (e.g. Otto Cycle or Diesel Cycle) engine. It involves the downward movement of the piston, creating a partial vaccum that draws a fuel/air mixture (or air alone, in the case of a direct injection engine) into the combustion chamber. The mixture enters the cylinder through an intake valve at the top of the cylinder.
Compression stroke
The compression stroke is the second of four stages in a four-stroke engine.
In this stage, the fuel/air mixture (or air alone, in the case of a direct injection engine) is compressed to the top of the cylinder by the piston. This is the result of the piston moving upwards, reducing the volume of the chamber. Towards the end of this phase, the mixture is ignited — by a spark plug for petrol engines or by self-ignition for diesel engines.
Combustion/Power/Expansion stroke
The combustion stroke is the third phase, where the ignited air/fuel mixture expands and pushes the piston downwards. The force created by this expansion is what creates an engine's power.
Exhaust stroke
The exhaust stroke is the final phase in a four stroke engine. In this phase, the piston moves upwards, squeezing out the gasses that were created during the combustion stroke. The gasses exit the cylinder through an exhaust valve at the top of the cylinder. At the end of this phase, the exhaust valve closes and the intake valve opens, which then closes to allow a fresh air/fuel mixture into the cylinder so the process can repeat itself
Types of power cycles
The thermodynamic cycle used by a piston engine is often described by the number of strokes to complete a cycle. The most common designs for engines are two-stroke and four-stroke. Less common designs include five stroke engine, six stroke engine and two and four stroke engine.
Two-stroke engine
Two stroke engine complete a power cycle every two strokes, which means a power cycle is completed with every crankshaft revolution. Two-stroke engines are commonly used in (typically large) marine engines, outdoor power tools (e.g. lawnmowers and chainsaws) and motorcycles.
Four-stroke engine
Four stroke engine complete a power cycle every four strokes, which means a power cycle is completed every two crankshaft revolutions. Most automotive engines are a four-stroke design.
Objective:-
To get linear displacement of piston and angular velocity of crank. With different dimensions of head cap of piston assembly.
Parts Of Piston Crank:-
Connecting Rod
Pin
Crank
End Cap
Piston Head (Offset 0mm)
Piston Head (Offset 10mm)
Piston Head (Offset -10mm)
Assembly:-
Plots:-
Piston Head (Offset 0 mm)
Linear Displacement of Piston with Piston head Offset 0 mm (Crank Motor = 2000rpm)
In this plot the piston goes up and down due to which linear displacement with respect to time plot is in a wave form.
Angular Velocity of Crank (Crank Frequency=2000rpm)
The angular velocity of crank remains constant
Piston Head (Offset 10 mm)
Linear Displacement of Piston with Piston head Offset 0 mm (Crank Motor = 2000rpm)
In this plot the linear displacement of piston goes up and down with respect to time.
Angular Velocity of Crank (Crank Frequency=2000rpm)
Angular velocity of crank remains constant
Piston Head (Offset -10mm)
Linear Displacement of piston (Frequency=2000rpm)
Linear displacement of piston with respect to time gives a wave form
Angular Velocity Of Crank (Frequency=2000rpm)
Angular velocity of crank remains constant
From the plot it can be seen that their is very slight change in linear displacement or angular velocity if change Piston head offset.
Conclusion:-
It can be concluded that the linear displacement of piston is in a wave form i.e. there is increase and decrease in linear displacement. And angular velocity of the crank remains constant throughout the process.