**3. Performance of HDRD in CI engines**

Desirous to find solutions to the obvious inadequacies in the utilization of PBD fuel in CI engines, HDRD has been used by various researchers. However, the major performance criteria used in measuring the performance characteristics include power, torque, fuel consumption, thermal efficiency, and mean effective pressure. For example, the brake specific fuel consumption (BSFC) is an important performance metric that measures the conversion of the fuel to useful work while mechanical efficiency calculates the effectiveness of the engine as the ratio of the brake power to the indicated power. On the other hand, the brake thermal efficiency (BTE) measures the ability of the engine to efficiently convert the chemical energy in the fuel to useful work.

Using these performance criteria, the engine metrics of HDRD is compared with that of PBD fuel when used in a CI engine are compiled in **Table 4**. When HDRD was used to power a 6.5 liters, indirect-injection, water-cooled military diesel engine, it was reported that an increase in load led to increased fuel consumption and improved brake mean effective pressure (BMEP). Also, at a given fuel consumption threshold, an increment in engine speed caused a reduction in the brake torque. It was also
