Variable volume Engine
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The document describes the variable volume engine, which features two different volumes during suction and power strokes to achieve advantages of variable compression and supercharging. It details the construction, working mechanism involving sub pistons and a lock mechanism, and how these components enhance engine performance. The conclusion highlights the benefits of the variable volume engine in terms of space efficiency and the ability to adjust compression ratios dynamically during operation.
![• 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)](https://image.slidesharecdn.com/variablevolumeenginenew-170420144335/85/Variable-volume-Engine-11-320.jpg)
Variable volume Engine
- 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.