This document provides an overview of internal combustion engines. It discusses indicator diagrams for 4-stroke engines, two-stroke engines, valve timing diagrams, variable valve timing (VVT), supercharging, and the types of superchargers. Key points covered include the operation of two-stroke and four-stroke engines, the components and control of VVT systems, and the objectives and effects of supercharging engines.

1. SHARAD INSTITUTE OF TECHNOLOGY, POLYTECHNIC,
YADRAV
POWER ENGINEERING AND REFRIGERATION
A
LECTURE ON
INTERNAL COMBUSTION ENGINE
BY
MS. VIDDYA S.PATIL
(ASSI.PROF. DEPARTMENT OF MECHANICAL ENGINEERING)

2. CONTENTS-
• Indicator diagrams for 4 stroke Engine
• Two stroke Engine
• Comparison of Two stroke and four stroke Engine
• Valve timing diagrams
• VVTI Engine- concept and arrangement
• Supercharging – Objectives and advantages

3. Indicator diagrams for 4 stroke Engine-
Indicator diagrams of two types- 1. Theoretical or Hypothetical diagram
2. Actual
Indicator diagrams for 4 stroke SI Engine-

4. Indicator diagrams for 4 stroke CI Engine-

5. Two stroke Engine-
• Two stroke- 1. Compression stroke
2. Power or expansion stroke
• One power stroke completes in one revolution
• Piston motion controls opening and closing valves
• Ports control the exhaust and inlet flows while the
piston is close to BDC
• Applicable to both SI and CI Engines
• High power to weight ratio
• Simple valve design
1. Compression stroke-
 Compress the cylinder contents and draws fresh
charge into the crankcase
 Initiation of combustion near TDC
2. Power or Expansion Stroke-
 Exhaust ports and intake ports are uncovered
sequentially.
 Induction of fresh charge compressed in the
crankcase

6. Types of two stroke engine–
Depending upon the scavenging method used there
are basically two types of two-stroke engines:
(i) crankcase scavenged engine
(ii) separately scavenged engine
I ) crankcase scavenged engine-
There are three ports in this engine.
(i) intake port at the crankcase
(ii) transfer port
(iii) exhaust port

7. ii) separately scavenged engine

8. Comparison of Two
stroke and four stroke
Engine

9. Comparison of Two
stroke and four stroke
Engine

10. Valve timing diagrams-
Valve timing diagrams for four stroke SI or Otto Engine-

11. Valve timing diagrams for four stroke CI or
Diesel Engine-

12. VVTI Engine- concept and arrangement
WHAT IS VVT ? • Variable Valve Timing (VVT) ,is a generic term for an automobile piston engine technology •
VVT allows the lift or duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while
the engine is in operation • Two stroke engines use a power valve system to get similar results to VVT
WHAT IS VVT-i • The VVT-i system is designed to control the intake camshaft with in a range of 50°(of
Crankshaft Angle ) to provide valve timing i.e. optimally suited to the engine condition .This improves the torque
in all the speed ranges as well as fuel economy ,and reducing exhaust emissions. • This system controls the intake
camshaft valve timing so as to obtain balance between the engine output, fuel consumption & emission control
performance. The actual intake side valve timing is feed back by means of the camshaft position sensor for constant
control to the target valve timing.

13. CONSTRUCTION The Variable Valve Timing (VVT) system includes
ECM
OCV
VVT controller
• The ECM sends a target duty-cycle control signal to the OCV. This control signal regulates the oil
pressure supplied to the VVT controller. Camshaft timing control is performed according to engine
operating conditions such as the intake air volume, throttle valve position and engine coolant
temperature.
• The ECM controls the OCV, based on the signals transmitted by several sensors. The VVT controller
regulates the intake camshaft angle using oil pressure through the OCV. As a result, the relative
positions of the camshaft and crankshaft are optimized, the engine torque and fuel economy improve,
and the exhaust emissions decrease under overall driving conditions. The ECM detects the actual intake
valve timing using signals from the camshaft and crankshaft position sensors, and performs feedback
control. This is how the target intake valve timing is verified by the ECM.
•The ECM optimizes the valve timing using the VVT system to control the intake camshaft. The VVT
system includes the ECM, the OCV and the VVT controller. The ECM sends a target duty-cycle control
signal to the OCV. This control signal regulates the oil pressure supplied to the VVT controller. The
VVT controller can advance or retard the intake camshaft.

16. 1.VVT-i Controller
• It consist of the housing driven from the timing chain & the vane coupled with the intake camshaft.
• The oil pressure sent from the advance or retard side path at the intake camshaft causes rotation in the VVT-i
controller vane circumferential direction to vary the intake valve timing continuously.
• When the engine is stopped the intake camshaft will be in the most retard state to ensure start ability.
• When hydraulic pressure is not applied to the VVT-i controller immediately after the engine has been started,
the lock pin locks the movement of the VVT-i controller to prevent a knocking noise.

17. 2.Camshaft Timing Oil Control valve
• The camshaft timing oil control valve controls the spool valve position in accordance with the duty-cycle control from
the ECM. This allows the hydraulic pressure to be applied to the VVT-i controller advance or retard side

18. OPERATION •
The camshaft timing oil control
valve selects the path according to
the advance, retard or hold signal
from the ECM. The VVT-i
controller rotates the intake
camshaft in the timing advance or
retard position or holds it according
to the position where the oil pressure
is applied.

19. In proportion to the engine speed, intake air volume throttle position and water temperature, the ECM calculates optimal
valve timing under each driving condition & controls the camshaft timing oil control valve. In addition ECM uses signal
from the camshaft position sensor & the crankshaft position sensor to detect the actual valve timing, thus performing
feedback control to achieve the target valve timing

21. ADVANTAGES-
• Improved torque & output
• Battery & fuel economy
• Reduced nitrogen oxide & hydrocarbon
emissions

22. Supercharging -
Objectives-
1.To increase the power output of the engine by increasing the density of charge at intake.
2. To reduce the weight to power ratio.
3. To overcome the loss of power at high altitudes either in case of static engines or in case of aircraft
applications.
4. To reduce the bulk of the engine where weight and space are important considerations like in case of
locomotives and marine engines.
EFFECTS OF SUPERCHARGING
 Higher power output
 Greater induction of charge mass
 Better atomization of fuel
 Better mixing of fuel and air
 Better scavenging of products
 Better torque characteristic over the whole speed range
 More complete and smoother combustion
 Smoother operation and reduction in diesel knock tendency
 Increased detonation tendency in SI engines
 Improved cold starting

23. Reduced exhaust smoke
Reduced specific fuel consumption, in turbocharging
Increased mechanical efficiency
Increased thermal stresses
Increased heat losses due to increased turbulence
Increased gas loading
Increased valve overlap period of 60 to 160◦ of crank angle Increased cooling requirements of pistons and valves
Limitations-
1. Increase in intake pressure increases the maximum pressure attained in the cylinder. This increases the weight of
cylinder since the engine has to be designed to withstand higher pressure.
2. Increased maximum pressure in the cylinder tend to increase detonation tendency in case of SI engines.
3. Higher peak pressure increases the friction losses
4. Higher peak pressure increases the bearing loads and frictional losses
5. Excessive supercharging may result into higher mean cylinder wall temperatures and it may cause the melting of
piston top and pre-ignition problems
6. Higher peak temperatures will lead to higher exhaust gas temperatures. It causes overheating of exhaust valves.

24. 1. TYPES OF SUPERCHARGERS-
1. Centrifugal type
2. Root’s type
3. Vane type

26. Thank You