1. Mechanical Losses in An Engine
P M V Subbarao
Professor
Mechanical Engineering Department
Estimation of Curse…..
One-Third of Car Fuel Consumption Is Due to Friction Loss !!!

2. Design Vs Actual p-V Diagram

3. The Cyclic Integral
k=1:for two-stroke cycle
k=2:for four-stroke cycle

4. Frictional Limit of A Thermodynamic Cycle
Integration of Real p-V diagram of an engine cycle will give net indicated work output per cycle.
This is only an indicative work output.
Only a fraction is available for use.
Actual work output available for use is called as engine brake work output.
Any thermodynamic cycle can be implemented as an engine.
Thermodynamic model generates indicated work output and engine generates brake work output.
Any thermodynamic concept is said to be practically feasible, only when engine brake power is positive and significant with respect to physical size of the engine.
The difference between indicative work output and brake work output is defined as Frictional Work.
The value of brake or frictional work is practically accepted as significant by comparing to the size of the engine.

5. Friction Loss
As the internal parts of an engine move, they rub against each other and lose energy due to friction.  
An example is the piston rubbing against the cylinder walls.  As power output and spin rate increase, the losses due to friction account for a larger portion of the engine's gross output.  
This is why efficiency falls off above the "sweet spot".  
Oil is circulated in the engine to reduce friction, but the primary goal is to reduce wear to an acceptable level.  
Until recently, engine design did not go to great lengths to further reduce friction and as a result improve efficiency.  
Ironically, friction becomes more of a problem as engines get smaller.  
So, when we make an engine smaller to address the partial power problem, we give up some of the gain to increased friction losses.

6. Science Daily (Jan. 12, 2012)
No less than one third of a car's fuel consumption is spent in overcoming friction.
This friction loss has a direct impact on both fuel consumption and emissions.
New technology can reduce friction by anything from 10% to 80% in various components of a car, according to a joint study by VTT Technical Research Centre of Finland and Argonne National Laboratory (ANL) in USA.
It should thus be possible to reduce car's fuel consumption and emissions by 18% within the next 5 to 10 years and up to 61% within 15 to 25 years.

7. Distribution of Fuel Power

8. Fuel energy distribution for a medium size passenger car during an urban cycle

9. Distribution of Mechanical Losses

10. Effect of Speed & Size on Component of Friction

11. Major Components of IC Engine Friction
Crank Shaft Friction
Reciprocating Friction
Valve train Friction
Auxiliary component friction
Pumping losses.

12. Fundamental Idea to Reduce Friction & Wear

13. Challenges in Implementing Optimal Lubrication

14. Anatomy of Piston Assembly

15. Parameters of Piston Assembly for Optimal Design
Gas pressure variations
Ring groove clearance
Groove flank profile
Ring flank groove interaction
Piston motion
Elastic and thermal deformation effects
Non-axisymmetric considerations including non-circular bores
Ring and cylinder liner wear
Surface topography influences
Ring and piston mechanical design
Crevice volume
Cavitation considerations

16. Friction due to Crank Shaft and other Bearings
Hydrodynamic Lubrication

19. Geometrical Solutions to Contain Friction in Bearings
The loads on the bearings vary significantly with crank angle, the connecting rod geometry and the combustion gas pressure.
Size of a bearing:
Diameter of crankshaft main bearing: 65% of bore.
Connecting rod bearings 55% of bore.
Bearing lengths are sized at 35 to 45% of bore.

20. Friction Force
Friction force is directly proportional to piston velocity
where m is a coefficient of friction that takes into account the global frictional losses