Fundamentals of Increasign Engine Power

The principles of increasing the engine capacity of
Fundamentals of Increasing Engine Power
Definitions:
– Mechanical efficiency Mechanical efficiency (hm):
    

	,
(1)

Thermal efficiency (hth, i ) Indicated:
   = 

Divide both the denominator and the numerator by time t

(2)

Brake thermal efficiency (hth, b):

(3)

 
Volumetric efficiency (hV):
  

(4)

 
From equation (3) we find that:

(5)

From equation (5), we find that the engine power depends on:
1- Thermal braking efficiency hb, th               
2- The rate of fuel consumption mf  
3- The calorific value of the fuel cv                                              
* by multiplying equation (1) by  

(6)

From equation (6) we find that the engine power depends on:
4- The ratio of fuel to air (f / e) F
5- The rate of air entry (air mass) ma  
* from equation No. (6)

(7)

From equation (7) we find that the engine power depends on:
6- The density of the incoming air ra     
7- The rate of air entry (air volume) Va    
* by multiplying equation (7) by  

(8)

From equation (8), we find that the engine power depends on:
8- the volumetric efficiency (degree of fullness) hV           
* and since the volume of air entering the engine is equal to:

If equation (8) becomes

(9)

 
From equation (9) we find that the engine power depends on:            
9- Engine capacity (cylinder capacity x number of cylinders) Veng               
10- Engine rotational speed N   
11- Number of engine strokes (quadruple i = 2, binary i = 1) i
* Since the engine size equals volume of cylinder x number of cylinders

Whereas, the compression ratio (r) is:

 
Substituting in equation (9) a value of x Z Veng = Vcy we get:

(10)

 
From equation (10), we find that the engine power depends on:
12- compression ratio r
* where the mechanical efficiency is equal to (the actual (braking) power divided by the theoretical power), so it is:

(11)

 
From equation (11) we find that the power of the motor depends on:
13- Mechanical efficiency hm 
14- Graphical power Pi                            
 
Factors affecting the power of the motor:

1	Braking thermal efficiency	Reduce heat loss, loss in cooling
2	fuel consumption rate	Increase the amount of fuel
3	calorific value of fuel	Using a fuel with a high calorific value
4	fuel to air ratio	Ratio increase during acceleration
5	air intake rate	Depends on the air intake path section area, air passage speed, cylinder section area, piston speed, timing and number of valves, forced charging.
6	Intake air density	Forced charging, inlet air temperature, cooling
7	Inlet air volume	forced freight
8	Volumetric efficiency (degree of fullness)	Forced charging, valve timing
9	Engine Capacity	Depends on engine design, number of cylinders, cylinder diameter, stroke length
10	Engine rotation speed	Limited to the maximum value of the inertial force
11	Number of engine strokes	A two-stroke engine has twice the power of a four-stroke engine
12	compression ratio	Depends on the engine design, limited by the slapping limit of the gasoline engine, and the increased stresses for the diesel engine
13	mechanical efficiency	Depend on friction, it has running parts and accessories of the engine
14	graphic ability	Thermal cycle, ignition

 
Table of symbols used:

code	the meaning	Meaning
hm	mechanical efficiency	Mechanical efficiency
hth, i	Thermal Efficiency – Graphic	Indicated thermal efficiency
hth, b	Thermal Efficiency – Braking	Break thermal efficiency
hV	Volumetric efficiency	Volumetric efficiency
Pb	Engine brake power (kW)	Engine brake power (kW)
Pi	Graphic motor power (kw)	Engine indicated power (kW)
W	Engine work output (joules)	Output work (J)
t	time (sec)	Time(s)
mf	fuel mass (kg)	Fuel mass (kg)
mf	Fuel inlet rate (mass) (kg/sec)	Fuel rate (kg/s)
cv	Fuel heat capacity (joules/kg)	Fuel Calorific value (kJ/kg)
ma	intake air mass (kg)	Actual input air mass (kg)
ma th	Theoretical air mass (kg)	Theoretical air mass (kg)
ma	Air intake rate (mass) (kg/sec)	Rate of input air mass (kg/s)
F	Fuel-Air Ratio (Reciprocal of H/F Ratio)	Fuel air ratio
ra	Actual air density (kg/m3)	Actual air density (kg/m3)
ra, th	Theoretical air density (kg/m3)	Theoretical air density (kg/m3)
Va	Air intake rate (volume) (m3/s)	Rate of input air volume (kg/s)
d	Engine cylinder diameter (cm)	Cylinder bore diameter (m)
L	Stroke Length (cm)	Stroke length (m)
Z	Engine cylinder number	Number of engine cylinder
N	Engine rotational speed (rpm)	Engine rotation speed (rpm)
i	A number indicating the number of engine revolutions per revolution  = 2: four-stroke engine = 1: two-stroke engine	Number of engine rev/cycle =2: four stroke  =1: two stroke
Veng	Engine Capacity – Engine displacement (m3)	Engine swept volume (m3)
Vcy	cylinder volume – cylinder volume (m3)	Cylinder swept volume (m3)
Vc	Clearance Size (m3)	Clearance volume (m3)
r	compression ratio	Compression ratio