2.2.1. Maximum Injection Pressure Measurement

A 1.5 kW class 3-phase motor (Hyosung Co., Seoul, Korea) was used as a high-pressure injection pump for a common-rail system. It can pressurize up to 200 MPa, in order to inject at the maximum possible injection pressure, as listed in Table 1. A temperature sensor is placed inside the fuel tank to automatically turn on and off the radiator and a cooling fan is used to keep the temperature constant. As shown in Figure 2, the injection period and the injection pressure were controlled through the common rail controller (Zenobalti Co., Model:ZB-9013, Daejeon, Korea) and the universal piezo injector driver (Zenobalti Co., Model:ZB-6200, Korea).

**Figure 2.** Fuel injection control system; (**a**) Common-rail controller, (**b**) Injector driver.


**Table 1.** Experimental conditions for maximum injection pressure measurement.
