*2.4. Test Procedure*

The schematic view of the experimental setup is shown in Figure 3. A lamp load unit was built that had 500, 750, 1000, 1250 and 1500 W lamps in order to determine engine performance and emissions under different load states at constant 3000 rpm.

**Figure 3.** Schematic view of the experimental setup.

The technical specifications of SPIN ITALO PLUS exhaust emission device are given in Table 3. The exhaust emission analyzer can measure CO (% vol) with 0.001 sensibility, HC (ppm), NOx (ppm) and opacity (%) values. The exhaust gas analyzer device measurement method is based on laser absorption spectroscopy technology, which determines the gas concentration and temperature from the optical absorption at a specific wavelength. The instantaneous exhaust gas concentration and temperature are obtained by the analysis of laser light falling on the measurement sensor after passing through the exhaust gas. A K-type thermocouple with a temperature indicator was mounted to the exhaust pipe for measurement of the Exhaust Gas Temperature (EGT).

**Table 3.** Exhaust gas analyzer and opacimeter technical specifications.


The digital scales having 1 mg sensitive and a digital chronometer were used to measure both the diesel and LPG fuels flow by weight difference in a constant period. The specific fuel consumption was calculated. The calculated mass fuel consumption is compared to the engine power and the brake specific fuel consumption was found. The Brake Specific Fuel Consumption (BSFC) is estimated in g/(kW h) by using Equation (2).

$$\text{BSFC} = \frac{\text{mf}\_{\text{diesel}} + \text{mf}\_{\text{LPG}}}{\text{P}\_{\text{e}}} \tag{2}$$

The effective efficiency was calculated with Equation (3) by considering the lower heating value and mass flow rate of both fuels diesel and LPG.

$$\eta = \frac{\text{P\_e}}{(\text{mf} \ast \text{LHV})\_{\text{diesel}} + (\text{mf} \ast \text{LHV})\_{\text{LPG}}} \tag{3}$$

Before the data collection, the test engine was run until it reached engine operating temperature of 90 ◦C with experimental fuels. Experiments were conducted on stable operation modes by loading with lamp load unit. For each fuel blends (D-100, LPG-30, LPG-50, and LPG-70) used in experiments, engine performance and emissions were measured and recorded according to entire load conditions. Experimental measurements were repeated for three times for each operation point and obtained results were averaged. In the experiments, effective efficiency, EGT, fuel consumption, BSFC, and exhaust emissions (NOx, Smoke, HC, CO) were measured.
