Page 208 - Energy from Toxic Organic Waste for Heat and Power Generation

186 Energy from Toxic Organic Waste for Heat and Power Generation

reduced due to decreased combustion temperatures and air utilization. One
possible contributing factor to improve the combustion at low load is to
reduce leanness of the fuel combinations used. This can be achieved by
increasing liquid fuel supply at lower loads. The fuel substitution values for
HOME-PG(HCC) and HOME-PG (RCC) operation with 10%, 20%, and
30% fuel oil were found to be 55.2%, 54.4%, 58.2% and 59.8%, respectively,
compared to 61.0% for diesel-PG operation (HCC).

11.8.3 Combustion Characteristics
The performance and emissions of diesel engine mainly depend on the
combustion quality. Hence, use of gaseous fuels in a diesel engine changes
the combustion behavior. It depends on the air-fuel mixture quality and
is mainly caused by type of fuel used and combustion chamber geometry
used. The different combustion parameters for dual-fuel mode of operation
with different combustion chambers are summarized below.
The variation of ignition delay with brake power for different fuel com-
binations is shown in Fig. 11.27. Delay period decreases with increase in
load and is affected by the type and quantity of fuel and combustion cham-
ber used. From Fig. 11.27, for the same combustion chamber design, it is
noticed that diesel-PG operation resulted in lower ignition delay when
compared to HOME-PG operation. Reduced mixing of air and fuel and
inducting producer gas with higher CO concentration in the gas itself are
responsible for the increased delay period during HOME-PG operation.

Speed: 1500 RPM, CR: 17.5
Inj.timing: 27bTDC, Biomass: Babul wood
30 Injector: For diesel 3hole, 0.2mm, for HOME 4hole, 0.3 mm
IOP: For diesel 205bar, for HOME 230bar
Carburetor: Parallel flow gas entry
25
Ignition delay (degree CA) 20 Diesel-PG (HCC)

15

10
HOME+FO10-PG (RCC)
5 HOME-PG (HCC)
HOME+FO20-PG (RCC)
HOME+FO30-PG (RCC)
0
0.00 0.74 1.48 2.22 2.96 3.70
Brake power (kW)
Fig. 11.27 Effect of combustion chamber shape and fuel oil addition on ignition delay