Determination of the pneumatic engine indices for the hybrid power unit of a city car

Abstract

The problem of environmental pollution by the motor transport forces to look for new ecologically cleaner power units. Definition and the choice of the mode and dimensional indicators of the piston pneumatic engine working as a part of such hybrid unit of a city car was the goal of work. The methodology of the research was based on computational research of indicators of the pneumatic engine using the liquefied air which heats up at the entrance to cylinders of the pneumoengine due to the heat of the environment and the waste heat of ICE. Calculations and the choice of optimum mode and dimensional indicators of the pneumo-engine were made for the hybrid power unitof the car with a full weight of 1200 kg moving with a speed of 60 km/h. Three operating modes of plant with parallel operation of ICE and the pneumoengine with distribution of power between them 50/50, 60/40 and 70/30 were considered. Gear ratio of the drive of driving wheels of the car from the pneumoengine was accepted as 1:1. The results of the research are presented in the form of graphic dependences of key indicators of the pneumoengine on the parameters of compressed air at the entrance to its cylinders. On the basis of calculations of work indicators of ICE on the corresponding modes and thermal balances between compressed air, cooling liquid and the exhaust ICE gases the operating mode of the unit and the parameters of air at the entrance to pneumoengine cylinders which provide the minimum flow of air at small dimensions of the engine is chosen. Such an optimum operating mode of the unit is the mode of distribution of power between ICE and pneumoengine as 60/40 with the air pressure at the entrance to cylinders of the pneumoengine of 1.6 MPa and the degree of cylinders filling 0.219. The results allow to make a choice of an optimum operating mode of the hybrid power unit "ICE – pneumoengine" with parallel operation of engines for the city car and indicators of operation of the pneumoengine which provide a low flow of air at small dimensions of the engine