This Concept was published in WCE 2010, London, UK. In conventional engine suction & expansion volume will be same and compression & exhaust volume will be same. But In VVE suction, compression, expansion volume are different and exhaust volume will be equal to compression. So in VVE 3 types of volume are present which gives it a combine effect of supercharging and variable compression ratio.

2. content
• Introduction
• Construction of variable volume engine
• Working
• Supercharging and Variable compression ratio
• Modified otto & diesel cycle
• conclusion

3. 1- introduction
Q. What is Variable Volume Engine ?
In Variable Volume Engine, volume of engine during all four strokes is not constant. There will
be 2 different volume during Suction and Power strokes.
Aim of this Engine is to achieve a combined advantage of the Variable Compression Ratio and
Supercharging.

4. 2- construction
• Sub Pistons and Extended Cylinder
o Extended Cylinders are present below the Combustion Chamber.
And Sub Pistons are present inside these Extended Cylinders.
o The motion to the Sub Pistons are given by a Cam which will be
connected to the Crank Shaft of the Engine.
o These Sub Pistons will be in motion during Suction Stroke and
the Compression Stroke of the Main Piston.
o The top surface of the Sub Piston is Concave. This surface will
coincide with the Inner Surface of the Cylinder to form the
Combustion Chamber as in Conventional method.
o During power stroke of the Main Piston, the Cylinder acts as a Conventional Cylinder by Lock
Mechanism.
Figure 1-Extended cylinders
Sub Piston
Sub Cylinder

5. • Lock mechanism
o In the bottom of Extended Cylinder there is a cut,
and a lock assembly will be present in this cut.
o There is a Sliding Surface on one side and a Flat Surface on other side of the Lock.
o This sliding arrangement allows the Sub Piston to move towards the main cylinder, and the
flat surface does not allow the Sub Piston to move apart from main Cylinder.
Figure 2-Lock mechanism
Lock

6. 3- working
• During Suction stroke, main piston sucks the Air or Air-Fuel mixture. Along with the main
piston, sub piston also sucks air or air fuel mixture.
• During Suction Stroke, the Lock is pushed down by mean of cam and overall Suction Volume
increases.
Figure 3- Suction Stroke
Inlet valve Exhaust Valve
Suction Stroke

7. • Compression starts from this volume and ends
at the conventional combustion chamber volume.
• At the end of the compression stroke,
Sub-Piston will be locked by the lock mechanism.
Figure 4- Compression stroke
Compression Stroke

8. • Because sub pistons are locked,
The Power is only developed in the Main Piston.
• Then Exhaust stroke starts and Exhaust gas
is removed through exhaust valve.
Figure 5- Power Stroke
Figure 6- Exhaust Stroke
Power Stroke
Exhaust Stroke

9. • Supercharging and Variable Compression Ratio
o Supercharging is the process of increasing the volumetric efficiency of the engine. Power for the
Supercharger can be provided mechanically by means of Belt, Gears, Shaft or Chain drives via
Crankshaft.
o But in Variable Volume Engine Supercharging can be done by Sub-pistons. Because Sub-pistons can
suck more air or air fuel mixture. Results in increasing compression ratio.
o In order to make Compression Ratio variable, stroke length of the sub pistons is adjusted to control the
extended volume. And this can be achieved by controlling the Lock Mechanism.
o Increasing the stroke length leads to an increase in the extended volume, thus increasing the
compression ratio.
o Thus variable compression ratio and supercharging can be achieved by this variable volume engine by
using Sub-pistons.

10. 4- Modified otto & diesel cycle
• OTTO Cycle
o Let volume of Sub Cylinder = a
o Total Suction Volume V5 = V1+a
o Clearance volume = V2
o Compression Ratio r =
o Since here total volume is V5 so compression
ratio is written as rm , rm =
o Efficiency of OTTO cycle will be η = 1 - , Since rm > r so efficiency of modified otto
cycle will be more.
Figure 6- Actual OTTO cycle Figure 7- Modified OTTO cycle
Total volume
Clearance Volume
V5
V2
1
(γ-1)
rm
6 ,5

11. • DIESEL Cycle
Figure 8 – Actual Diesel Cycle Figure 9 –Modified Diesel Cycle
o Let volume of Sub Cylinder = a
o Total Suction Volume V5 = V1+a
o Clearance volume = V2
o Cut off Ratio c =V3/V2
o Modified Compression ratio is similar to Otto Cycle , rm =
o Thermal Efficiency of modified diesel cycle will be
rm>r so efficiency of modified Diesel cycle will be more.
V5
V2
ηth = 1 - 1 [(cγ-1)]
(rm) γ[(c-1)](γ-1)

12. Conclusion
• Variable Volume Engine requires less space, as compared to supercharged engines.
• For supercharger, direct power is taken from engine to run compressor.
But in Variable Volume Engine no direct power is required.
• Variable compression ratio is a technology to adjust the compression ratio of an internal
combustion engine while the engine is in operation.
• In VVE variable compression ratio can be obtained by adjusting the stroke length of sub
piston.
• So in VVE two different phenomena can be obtained with the single assemble.