1. Real I. C. Engines Vs Ideal Models
P M V Subbarao
Professor
Mechanical Engineering Department
Ideal Cycles Set Performance Limits !!!
Real Engines are Yet Reach these Limits…

2. Performance of an Ideal Engine for Unit Distance Travel by Vehicle
Ideal cycle work to be provided by A Powering Engine:
The speed of the vehicle in km/h is:
Time required to travel 1 km distance by vehicle in hours:
Work to be done by Engine for Unit Distance Travel by Vehicle
Engine Fuel Consumption for Unit Distance Travel by Vehicle

3. Future Targets for LCVs
EU:60.6
Japan:55.1
US:LDV:49.1

4. Gap in Conventional Concepts - factor of 2 in efficiency
Ideal Otto cycle engine with CR = 8: 52%
Real engine: %
Differences are due to
Heat losses
Friction losses
Fluid Dynamic losses

5. Displacement Work Devices for Execution of Macro Thermodynamic Operations
Intake
Stroke
Combustion
Products
Exhaust
Stroke
Power
Stroke
Compression
Stroke

6. Nature of Temporally Cycling Devices
The thermal operation of an IC engine is a transient cyclic process.
Even at constant load and speed, the magnitude of in-cylinder thermodynamic parameters vary with time.
Each event may get repeated again and again.
So, an IC engine operation is a transient process which gets completed in a known or required Cycle time.
Higher the speed of the engine, lower will be the Cycle time.
How to fix the cycle time?
Within a given cycle time, how to allocate the time slots for each process?
Within a given time slot, how to control the process speed and hence rates of changes in thermodynamic properties?

7. The Art of Positive Displacement Work
Onset of displacement of system provokes the process.
The rate of change in instantaneous displacement controls, decides the rates of changes of other thermodynamic variables.
The brain of an animal controls the strain rates in Muscles…..
How to design the basic brain of these devices?

8. Control Dominates the Strength

9. Control System of A Conventional I.C. Engine
Primary Thermodynamic Requirement:
How to select other geometrical parameters?

10. Engine Geometry Vs Airstandard Otto Cycle

11. Otto Cycle Volume to meet the Demand

12. Engine Geometry Vs Diesel Cycle

13. Maximum Diesel Cycle Volume to meet the Demand

14. Cycle Volume Vs Cylinder Volume
A given cycle can be met using m number of similar cylinders if required.
Any restriction on stroke length can be satisfied by using multi-cylinder engine.
Why is this required?

15. Review of History
Gottlieb Daimler built an improved four-stroke engine with mushroom-shaped valves and two V-slant cylinders.
Wilhelm Maybach built the first four-cylinder, four-stroke engine.