This document contains formulas related to internal combustion engines. It defines formulas for calculating the indicated power of four-stroke and two-stroke engines, brake power, friction power, mechanical efficiency, indicated thermal efficiency, brake thermal efficiency, relative efficiency, air standard efficiency, volumetric efficiency, specific output, and specific fuel consumption. The formulas are presented along with their variables and units of measurement. The document was prepared by students for a class on combustion engines.

1. BHAGWAN MAHAVIR
INSTITUTE OF ENGINEERING AND
TECHNOLOGY
Topic:-Combustion EnginesFormulas of Internal
Guided By:- Kailas Sir
Branch:- CSE Sem- 1

2. Prepared By:-
•Darshil Shah
•Chintan Rajpara
•Darshan Lathiya

3. Introduction

4. In 1876 four stroke engine
based on Otto cycle was
developed by a German
engineer Nikolous Otto.Which
revolutionized the
development of Internal
Combustion engines and are
even used till date.Diesel
engine was developed by
another German engineer
Rudolf Diesel in the year 1892.

5. 1.Indicated power of a Four-stroke
Engine
• I.P.= Pm L A N KW
60000×2
Pm=Actual Mean Effective
pressure,N/m2
L=Length of stroke,m
A=Area of cross section of the
cylinder,m2
N=RPM of engine crankshaft

6. 2.Indicated power of a Two-stroke
Engine
• I.P.= Pm L A N KW
60000
Pm=Actual Mean Effective
pressure,N/m2
L=Length of stroke,m
A=Area of cross section of the
cylinder,m2
N=RPM of engine crankshaft

7. 3. Brake Power
• B.P.= 2∏NT = Pmb LAN KW
60000 60000
Pm=Actual Mean Effective pressure,N/m2
Pmb= Brake mean effective pressure, N/m2
L=Length of stroke,m
A=Area of cross section of the cylinder,m2
N=RPM of engine crankshaft
T=W×R N.M
[ where, W=Net Load acting on the break drum,N
R=Radious of the brake drum,m ]

8. 4. Friction Power
• F.P.= I.P – B.P.
I.P.=Indicated power
B.P.=Brake Power

9. 5. Mechanical efficiency:-
• Ƞmech = B.P
I.P
I.P.=Indicated power
B.P.=Brake Power

10. 6. Indicated Thermal Efficiency
• Ƞit = I.P
mf ×C.V
mf=Mass of fuel supplied,kg/sec
C.v=calorific value of fuel, j/kg
I.P.=Indicated power

11. 7. Brake Thermal
• Ƞbt = B.P
mf ×C.V
mf=Mass of fuel supplied,kg/sec
C.v=calorific value of fuel, j/kg
B.P.=Brake Power

12. 8. Relative efficiency:-
• Ƞrel = Ƞit
Ƞair
Ƞit = Indicated Thermal efficiency
Ƞair= Air Standard efficiency

13. 9. Air Standard efficiency
•Ƞair= 1- 1
(r)ϒ-1

14. 10. Volumetric efficiency:-
• Ƞvol = Actual volume of charge/air sucked at atm. Condition
Swept volume

15. 11. Specific output
• Specific output = B.P.
A
B.P.=Brake Power
A=Area of cross section of the
cylinder,m2

16. 12. Specific fuel consumption:-
• SFC = mf kg/kWh
B.P.
mf=Mass of fuel supplied,kg/hr
B.P.=Brake Power, kw