Abstract:
Compression Ignition (CI) engines are widely used in transportation and power generation
industries in Nigeria. However, their low thermal efficiency and high emissions have
necessitated continuous efforts at redesigning the Combustion Chamber (CC). There is still
sparse literature on effect of using non-cylindrical piston crown in addressing these limitations.
This study was therefore designed to investigate the performance characteristics of a CI engine
equipped with Truncated Cone Piston Crown (TCPC) and Inverted Truncated Cone Piston
Crown (ITCPC) using selected fuels.
A model based on mass balance, momentum, energy, and k-ε turbulent equations was developed
and solved using finite-element technique to obtain Temperature, Pressure and Emission
History (TPEH) inside the CC of a CI engine. The model was applied to two standard CI
engines utilising Automotive Gas Oil (AGO) with equivalence-ratio, initial pressure and
temperature of 0.5, 100 kPa, and 313 K respectively. The standard CI engines are Kirloskar TV1 (KTV) with 87.5 mm cylinder-bore, Compression Ratio (CR) of 17.5 and Yoshita-165F
(Y165) with 70 mm cylinder-bore, CR of 20.5. The TPEH was used to estimate Engine Thermal
Efficiency (ETE), Specific Fuel Consumption (SFC), and Carbon Monoxide Emissions (CME).
The model was further applied to KTV with TCPC (KTV-TCPC), KTV with ITCPC (KTV ITCPC), Y165 with TCPC (Y165-TCPC), and Y165 with ITCPC (Y165-ITCPC) at Truncated
Cone Base Angles (TCBA) of 25, 30, 35, 40 and 45°. Biodiesel was prepared from Shea-butter
and its physicochemical properties determined using standard techniques. The ETE, SFC and
CME were determined experimentally for Y165 and Y165-TCPC with the selected TCBA
using AGO and 100% biodiesel. Data were analysed using ANOVA at α0.05.
The ETE, SFC, and CME for KTV were 30.90%, 0.194 kg/kWh, and 1558.70 ppm,
respectively, while for Y165 were 32.20%, 0.347 kg/kWh, and 1545.24 ppm. The best TCBA
for KTV-TCPC, KTV-ITCPC, Y165-TCPC, and Y165-ITCPC was 40°. At TCBA of 40°, ETE,
SFC, and CME were 30.91%, 0.192 kg/kWh, and 1557.99 ppm, respectively for KTV-TCPC,
30.93%, 0.193 kg/kWh, and 1558.00 ppm, respectively for KTV-ITCPC, 32.26%, 0.346
kg/kWh, and 1542.94 ppm, respectively for Y165-TCPC, and 32.26%, 0.346 kg/kWh, and
1542.92 ppm, respectively for Y165-ITCPC. The determined specific gravity, calorific value,
kinematic viscosity, and cetane number for biodiesel were 0.923, 40.10 MJ/kg, 5.40 mm/s2
,
and 44.80, respectively. The ETE, SFC, and CME obtained experimentally for Y165 operated
iii
on AGO were 13.74%, 0.728 kg/kWh, and 1598.00 ppm respectively, while that of biodiesel
were 16.05%, 0.599 kg/kWh, and 1859.00 ppm respectively. The ETE, SFC, and CME for
Y165-TCPC operated on AGO were 12.60%, 0.794 kg/kWh, and 1463.00 ppm respectively,
while for biodiesel were 25.08%, 0.329 kg/kWh, and 780.00 ppm respectively. The CI engine
with TCPC and ITCPC showed better performance than KTV and Y165. There was no
significant difference between the numerical and experimental results.
The use of conical piston crown improved the performance of compression ignition engines.
The forty degree base angle truncated conical piston crown gave the best engine performance
