This document discusses the fundamentals of internal combustion engine design and operating parameters, covering performance definitions, torque and power measurements, and geometrical properties of reciprocating engines. It also presents various engine performance parameters, design comparisons between spark ignition and compression ignition engines, and related calculations such as gas loading force and side thrust force. The content is aimed at engineering students and includes MATLAB program references for problem-solving.

1. Internal combustion
engine fundamentals
Chapter no. 02
Engine design and operating parameters
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2.  Presented by
Hassan Raza 2013-ME-310
M Ansar Alam 2013-ME-311
Zaighum Shabbiir 2013-ME-313
Soban Ahmad Sair 2013-ME-317
Junaid Khalid 2013-ME-311
 Presented to
Dr. Shahid Imran
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3. Contents
 Performance Definitions
 Geometrical properties
 Torque and Power
 Engine performance parameters
 Design comparison
 Problems
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4. Performance Definitions
 Maximum Rated Power: The maximum power
developed by an engine for short period of time.
 Normal Rated Power: The highest power an
engine is allowed to develop in continuous
operation
 Rated Speed: The crank shaft rotational speed at
which rated power is developed
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5. Torque and Power
Torque of output shaft is measured using a
dynamometer
The Torque exerted by the engine is T = F . B
The Power (P) delivered by the engine turning at a
speed N and absorbed by the dynamometer is
P = ω . T = (2πN) T units: Watt
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6. Geometrical properties of reciprocating
engine
 Compression ratio
𝑟𝑐 =
𝑉𝑑 + 𝑉𝑐
𝑉𝐶
 Ratio of cylinder bore to length
𝑅 𝑐 =
𝐵
𝐿
; 𝑤ℎ𝑒𝑟𝑒 𝐿 = 2𝑎
 Ratio of connecting rod length to
crank radius
𝑅 =
𝑙
𝑎
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7.  Cylinder volume at any crank
position
𝑉 = 𝑉𝑐 +
𝜋𝐵2
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𝑙 + 𝑎 − 𝑠
 Distance between crank shaft and
piston at different crank positions
𝑠 = 𝑎𝑐𝑜𝑠𝜃 + (𝑙2 − 𝑎2 𝑠𝑖𝑛2 𝜃)
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2
 Mean piston speed and
instantaneous speed
𝑆 𝑝 = 2𝐿𝑁; 𝑆 𝑝 =
𝑑𝑠
𝑑𝑡
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8. Engine performance parameters
 Indicated power
𝑃𝑖 =
𝑊𝑐,𝑖 𝑁
𝑛 𝑅
;
𝑛 𝑅 = 2; 𝑓𝑜𝑟 4 𝑠𝑡𝑟𝑜𝑘𝑒
𝑛 𝑅 = 1; 𝑓𝑜𝑟 2 𝑠𝑡𝑟𝑜𝑘𝑒
 Brake power and frictional loss
𝑃𝑖𝑔 = 𝑃𝑏 + 𝑃𝑓
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9. 
 Mechanical efficiency
Ƞ 𝑚 =
𝑃𝑏
𝑃𝑖𝑔
= 1 −
𝑃𝑓
𝑃𝑖𝑔
 Mean effective pressure
𝑚𝑒𝑝 =
𝑃𝑛 𝑅
𝑉𝑑 𝑁
 Efficiency related to specific fuel consumption
𝑠𝑓𝑐 =
𝑚 𝑓
𝑃
Ƞ 𝑓 =
1
𝑠𝑓𝑐𝑄 𝐻𝑉
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10.  Air to fuel & fuel to air ratio
𝐴 𝐹 =
𝑚 𝑎
𝑚 𝑓
; 𝐹 𝐴 =
𝑚 𝑓
𝑚 𝑎
 Volumetric efficiency
Ƞ 𝑣 =
𝑚 𝑎
𝜌 𝑎,𝑖 𝑉𝑑
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11. Design comparison
SI Engines
 𝑟𝑐 = 8 𝑡𝑜12
 𝐵 𝐿 = 0.8 𝑡𝑜 1.2
 𝑅 = 3 𝑡𝑜 4
 𝑚𝑒𝑝 = 850 𝑡𝑜1050 𝑘𝑃𝐴
 𝑠𝑓𝑐 = 270 𝑔/𝑘𝑊ℎ
 12 ≤ 𝐴 𝐹 ≤ 18
CI Engine
 𝑟𝑐 = 12 𝑡𝑜 24
 𝐵 𝐿 = 0.5
 𝑅 = 5 𝑡𝑜 9
 𝑚𝑒𝑝700 𝑡𝑜 900 𝑘𝑃𝐴
 𝑠𝑓𝑐 = 200 𝑔/𝑘𝑊ℎ
 18 ≤ 𝐴 𝐹 ≤ 70
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12. Problems
Draw a free body diagram of the piston. Also calculate
the magnitude of the gas loading force and the side
thrust force due to the connecting rod at θ = 45° for the
following:
(a) A SI engine with an 85 mm bore at a cylinder pressure
of 20 bar (at θ = 45°)
(b) Note the relative magnitude of the different terms in
the road power requirement. Also estimate the force for
accelerating the vehicle from 40 to 60 mph in 5 seconds
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13. Gas loading force
Side thrust force
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14. FBD of piston
 N =[ F*cos(α)/cos(φ)]- m*a - m*g
 F= P/ r* ω =P/(2πn/60)*r (N)
 Sin (φ) = r*sin(θ)/b => φ=sin–1 (r*sin(θ)/b)
 θ+ φ+ α = 90o
 α = 90o – [θ+ sin –1(r*sin(θ)/b)]
 m = piston + connecting rod
 a = r*ω2*[cos(θ)+cos(2* θ)/(2*b/r)]
 N= [F*cos{90o–[θ+ sin –1(r*sin(θ)/b)]}*
cos{ sin–1 (r*sin(θ)/b)}]-m*a-m*g
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15.  F(thrust) = F*cos(α)*sin(φ)
 F(thrust)= F*cos{90o – [θ+ sin –1(r*sin(θ)/b)]}* r*sin(θ)/b
 Force for accelrating the piston
F=m*a=m*(vf-vi)/t
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16. MAT Lab program (a)16

17. Results (a)17

18. MAT Lab program (b)18

19. Results (b)19

20. Thank you
Any question
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