TITLE.PM5

GAS POWER CYCLES 639

dharm
\M-therm\Th13-3.pm5

=

10035 10035

mc Tp() 32 −T 17.77 005 1822.3 897.3( )

=

×−1.^ = 0.6048 or 60.48%. (Ans.)

Fuel consumption per kWh ; mf^ :

ηth(I) = 0.5 ηcycle = 0.5 × 0.6048 = 0.3024 or 30.24%

ηth(B) = 0.3024 × 0.8 = 0.242

Also, ηth(B) = B. P.

mCf× mf mf

=

×

=

×

1

3600

42000

3600

42000

or 0.242 =
3600
mf× 42000

or mf =
3600
0 242 42000.× = 0.354 kg/kWh. (Ans.)

13.6. Dual Combustion Cycle

This cycle (also called the limited pressure cycle or mixed cycle) is a combination of Otto
and Diesel cycles, in a way, that heat is added partly at constant volume and partly at constant
pressure ; the advantage of which is that more time is available to fuel (which is injected into the
engine cylinder before the end of compression stroke) for combustion. Because of lagging charac-
teristics of fuel this cycle is invariably used for diesel and hot spot ignition engines.
The dual combustion cycle (Fig. 13.19) consists of the following operations :
(i) 1-2—Adiabatic compression
(ii) 2-3—Addition of heat at constant volume
(iii) 3-4—Addition of heat at constant pressure
(iv) 4-5—Adiabatic expansion
(v) 5-1—Rejection of heat at constant volume.

p

3 4

2

5

1

Adiabatic

Adiabatic

V

T

s

p = C

v = C

4

2 5

1

3

Fig. 13.19.