Assessment of comfort index (CI) based on vibration characteristics in CNG control system development

Compressed Natural Gas (CNG) is an environmentally friendly alternative fuel that is affordable with high octane value. Although numerous preliminary studies have been developed about CNG, none examines engine vibrations on human body comfort. Based on these problems, this research proposes an experimental method to observe engine vibration characteristics in developing a CNG engine control system for human body comfort. In the first test, the vehicle was evaluated at an environmental temperature of 18 C-degrees and air humidity of 98 %. The second method tested it at environmental temperature of 23 C and air humidity of 73 %. The results of the first method test showed that the machine vibration amplitude on the x-axis decreased from (2.82-2.25 mm) to (0.85-0.82 mm). The Comfort Index (CI) assessment consisted three checks, namely vibration acceleration, vibration frequency and damping. Vibration acceleration was in a cluster close to III with a maximum threshold value of 4 h for engine vibration. Meanwhile, the test results of the second method showed that the vibration amplitude in the x-axis decreased from (2.82-2.35 mm) to (0.85-0.81 mm. The Comfort Index (CI) assessment was close to cluster II with the threshold value maximum limit of 6 h for engine vibration. The decrease in CI in the second test method was because the second test had a higher environmental temperature and lower humidity. The density of the air/CNG significantly influenced the engine speed and vibration acceleration. This research failed to test ignition angles with various positions, lean and rich AFR, or fuel consumption. Therefore, in future research, is needed to consider these variables.