## 3 Results and Discussion  
The effect of experiment fuels on the effective efficiency depends on the engine load is shown in Figure 4. The highest effective efficient was achieved about 28.34% using LPG-70 fuel at 1250 W engine load. The ignition delay, uncontrolled combustion, and post-combustion phases were occurred in a short time because of better atomization of the LPG fuel in the cylinder. The lower heating value and C/H ratio of LPG lead to higher flame temperature and effective combustion. In addition, LPG direct injection does not affect intake air and maximum air charging results in the air intake stroke. This phenomenon led to decreasing the fuel consumption and increasing the effective efficiency overall LPG fuel ratios. Effective efficiency results are in concordance with other studies [21; 22; 36; 37]. The changes in EGT depends on the engine load are shown in Figure 5. In the experiments, the amount of consumed fuel and EGT increased continuously through the increase of engine load. In addition, EGT presented incremental behavior for all fuel types. However, as the engine load increased, the increase in the LPG ratio reflected more on the EGT. At the lower engine loads ignition delay period of diesel fuel increases and also, fine ignition and combustion of LPG do not occur due to low temperature and pressure inside the combustion chamber. However, at the higher engine  
Figure 4: Effect of engine loads change on effective efficiency. loads ignition delay period of diesel fuel decreases and also pressure and the temperature inside the cylinder become higher, an increase in EGT occurs due to this fine ignition and combustion of LPG. In addition, the low C/H ratio of LPG, high combustion rate, and better fuel atomization than diesel fuel have improved combustion process. These similar results were also observed by other researchers [21; 34; 35; 36; 37; 38]. The effect of engine loads change on the amount of the fuel consumption is given in Figure 6. The fuel consumption was reduced by means of occurring better combustion because the lower heat value of LPG is higher than diesel fuel about 8%. This situation may be explained by increasing of the LPG flow rate increases the heat release because of the overall equivalence ratio and the combustion is inclined to be more complete, leading to high in-cylinder pressures and increased power output. The fuel consumption results are in concordance with those of other researchers [21; 30; 32; 37; 39]. The BSFC for experiment fuels is given as a function of engine loads in Figure 7. The lowest BSFC was achieved using LPG-70 fuel at 1000-Watt engine load. When the BSFC was compared in terms of D-100 and LPG-70, it was seen that BSFC demonstrated reducing behavior by about 6%. Thus, the BSFC decreased because of the lower heat value of LPG was higher than pure diesel. Similar results were reported in other studies [21; 30; 40; 41; 42]. Figure 5: Effect of engine loads change on Exhaust Gas Temperature (EGT). Figure 6: Effect of engine loads change on fuel consumption. The NOx emission is given as a function of engine load in Figure 8. Although better combustion in the cylinder and increasing effective efficiency is desired in the automotive industry, they cause to rise NOx emission directly. It is well known that NOx emissions are the result of nitrogen reacts with oxygen at the high temperature in the cylinder. The cylinder peak pressure, the maximum heat release rate, the maximum cylinder mean gas temperature, the proportion of the premixed heat release, and NOx emission increase while increasing the propane proportion in the fuel blends [42; 43]. As the load is increased, the richer mixture results in higher temperatures which in turn results in higher NOx emissions. Due to locally rich combustion, NOx emissions of the diesel engine are less sensitive to temperature increases resulting from increasing load [31; 32; 33].