The paper presents the concept of a new engine called variable volume engine. The volume of variable volume engine is not constant. In the variable volume four stroke engines, during the two strokes there will be one volume and during the other two strokes, there will be another volume. The main aim of this engine is to achieve a combined advantage of the variable compression ratio and supercharging. It is observed that overall efficiency of the engine also increases. Thus variable volume engine has the advantage of the increased volumetric efficiency due to supercharging and the increased efficiency of the engine due to both supercharging and variable compression ratio. Otto and diesel cycles are drawn and the performance of variable volume engine is compared with the supercharged engine and their simulated graphs are drawn.


                    The present trend of increasing volumetric efficiency is by supercharging and turbo charging. In the above method, compressor is run to supply compressed air fuel mixture to the engine. This compressor is driven by the turbine which utilizes heat from the exhaust gas. The method used for obtaining variable compression ratio is by means of three links connecting the crank and the piston. However supercharged engine presently does not have the advantage of variable compression ratio. The purpose of the variable volume engine is to get a combined advantage of supercharging and the variable volume compression ratio and thereby getting an increased efficiency for the engine. However it is not the method of just attaching a turbo charger with the variable compression ratio engines. The combined advantage is obtained only by a single arrangement. The volume of the engine is not constant during all the four strokes and so the name, ‘variable volume engine’ is given.


                Let us start the working principle from the power stroke. Gas will expand only on the main piston. Thus mechanical power is transmitted to the flywheel only through the main piston. The volume of the cylinder during the starting of the power stroke is the combustion chamber volume. This is same as conventional engine. Then exhaust stroke starts and exhaust gas is allowed to escape out through exhaust valve. Then suction stroke starts. During this stroke, main piston sucks the air or air fuel mixture. Along with the main piston, sub piston also sucks air or air fuel mixture. The motion to the sub piston is given by the cam shaft through cam against the spring load. As the sub piston sucks air or air fuel mixture, the lock is pressed down from the slot by another cam. At the end of the suction stroke, the volume of the cylinder is sum of volume of the main cylinder and the volume of the extended cylinders. This will be the volume at the start of the compression stroke. Compression starts from this volume and ends at the conventional combustion chamber volume.
                  During this stroke along with the main piston, sub pistons also compress the air or air fuel mixture. The motion to the sub piston is due to the expansion force of the spring. During the forward motion of the sub piston, it slides over the lock and compresses the air or air fuel mixture. At the end of the compression stroke, sub-piston will be locked by the lock mechanism. Thus power acts only on the main piston. Thus this cycle continues and during the other two strokes, the sub pistons will not be under motion. These sub pistons due to the lock will not move during gas burst arising at the power stroke. At last, the power is only developed on the main piston.

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Sachin Thorat

Sachin is a B-TECH graduate in Mechanical Engineering from a reputed Engineering college. Currently, he is working in the sheet metal industry as a designer. Additionally, he has interested in Product Design, Animation, and Project design. He also likes to write articles related to the mechanical engineering field and tries to motivate other mechanical engineering students by his innovative project ideas, design, models and videos.

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