過給機 特性線圖를 利用한 디젤機關과 過給機의 매칭計算에 關한 硏究

Abstract

Basic methods to increase power output of internal combustion reciprocating engine is increasing of engine revolutions and engine displacement. But they have limitations because of reduction of volumetric efficiency, increase of mechanical losses, noise, vibration, size and weight of engine.

For this reason, most of engines have been coupled with a turbo charging system in order to increase engine power. Turbocharging can be defined as the introduction of air into an engine cylinder at a density greater than atmosphere. This allows a corresponding increase in the fuel that can be burned hence raises the available power output.

The engine is designed for variable speed and the operation will usually exhibit some deterioration in performance both at extreme low and high speed. However, the useful speed range can be wide, since engine is well suited to cater for a wide range of mass flow rate.

The performance of turbocharger is directly dependent upon the gas angle at entry of the impeller, diffuser of compressor and turbine rotor. The blade angles are set to match these gas angle, but a correct match will only be obtained when the mass flow rate is correct for a specified rotor speed. Therefore turbocharger is not well suited for operation over a wide flow range.

Turbocharger is not ideally suited to operate in conjunction with a engine. So the combination of diesel engine and turbocharger must be planned with care.

The objective of turbocharger matching is to fit a turbocharger with the most suitable characteristics of an engine in order to obtain the best overall performance. Matching of the correct turbocharger to a diesel engine is very important and is vital for successful operation of a turbocharged diesel engine. It will principally be governed by required performance with engine.

Simulation program used for the optimum calculation of turbocharger matching is very effective method to estimate turbocharged diesel engine performance.

In this paper the author has studied a calculation of turbocharger matching for 4 stroke automotive diesel engine and marine diesel engine through development of simulation program by using performance characteristics of turbocharger, and has estimated effects of efficiency, size of turbine and fuelling on the engine and turbocharger.

It was assured that simulation results agreeed well with experimental results of thermodynamic states at turbocharger and intake, exhaust manifold, and yield correct tendencies of estimation according to efficiency, size of turbine and fuelling.