Modeling and Validation of a Roots-type Supercharger Using GT-SUITE

Superchargers are engine driven positive displacement devices which increase the air mass flow into the engine, thereby leading to a better combustion efficiency. This gives an advantage of extracting more power from the same engine [1], thereby reducing emissions and achieving a better fuel economy [2]. With emission norms getting more and more stringent, the need for boosting engine intake air becomes very important [3]. There are many types of superchargers based on design [4], out of which, the roots-type positive displacement supercharger, is discussed in here. A 1-dimensional model of supercharger gives flexibility of choosing the right aspect ratio (length to the diameter of the rotor), deciding on the clearances (a tradeoff between volumetric efficiency and manufacturing capabilities) and arriving at the inlet and discharge port dimensions. The dependency of the above parameters on mass flow rate of air and volumetric efficiency of the supercharger can be studied in good depth with a simplified one dimensional model [3]. This paper aims to present a one dimensional model of roots-type twin rotor (each 3 lobed) supercharger using pre-modeled library components on GT-Suite. This model has been validated with the test setup for different speeds and pressure ratios and is found to be accurate to the tune of min. 90% on mass flow and min. 97% on discharge temperatures. This model further assists in developing a supercharger map which helps in matching supercharger to the engine requirements.