Yi Cui

Equivalent turbocharger model of regulated two-stage turbocharging system

Abstract A theoretical study on the regulated two-stage turbocharging (R2S) system is conducted based on the equivalent turbocharger concept. Expressions for the equivalent turbine flow area and the equivalent turbocharger efficiency of the R2S system were derived. The equivalent turbine flow area can be used in the analysis of the regulating capacity of the R2S system, according to which the combination of the high and low pressure stage turbochargers is determined. The equivalent turbocharger efficiency gives the criteria for matching the R2S system with diesel engine, which is optimising the exhaust energy distribution between the two-stage turbines to maintain high equivalent turbocharger efficiency. The paper closes with a computational analysis of the characteristic of the R2S system, and the application of the equivalent turbocharger model for matching and optimisation of the R2S system is studied.

Turbocharging System Design and Performance Analysis of a Marine Diesel Engine

The selection of turbocharging systems for 8-cylinder marine diesel engines is difficult due to the existence of scavenge interference between cylinders. The constant pressure and pulse converter turbocharging systems have been used to eliminate the scavenge interference by applying large volume exhaust manifolds or grouped exhaust branches according to the firing order. But, the performance of constant pressure turbocharging system under low speed conditions of propulsion characteristics and transient conditions is poor, because of less available exhaust gas energy. The structure and arrangement of pulse converter turbocharging system is complex, meanwhile, and the performance at high speed and loads is not as good. In this paper, three new turbocharging systems, such as, MIXPC (mixed pulse converter) system, dual-turbocharger system (DTS) and controllable exhaust system (CES) were designed to improve the performance of a marine diesel engine. In the upstream part of MIXPC system, the separated small diameter branch pipes were used to isolate the exhaust gas interference. In the downstream part of MIXPC system, the single main pipe was connected with one entry turbocharger to improve the operation efficiency of the turbocharger. In the DTS, two one-entry turbochargers were used, one of which connected with 4 cylinders by two branch pipes and a mixer. The two cylinders with firing intervals of 270 crank angles were connected with one branch pipe. In the CES, a control valve was used to control the exhaust gas flow. The valve was opened at high speed and load conditions and closed at low speed and load conditions. The steady and transient performance of the three turbocharging systems was analyzed by simulation. The experimental studies were also carried out to compare the performance of the three turbocharging systems. The experimental results showed that the CES had the best fuel efficiency under low speed and load conditions, and the DTS had the best fuel efficiency under high speed and load conditions. Compared with the MIXPC system, the overall brake specific fuel consumption under propeller operating conditions was reduced by 11.3g/kWh with DTS and 5.3g/kWh with CES. But the uniformity of exhaust gas temperatures of cylinder heads was the best for MIXPC system. In general, the DTS was superior considering the structure simplicity and performance of the engine.Copyright

Study on variable geometry exhaust manifold turbocharging system for six‐cylinder diesel engine

AbstractThe variable geometry exhaust manifold (VGEM) turbocharging system can realise the switch between two charging modes by controllable valves, and it can perform well both at high and low speed operations. In order to apply the VGEM turbocharging system to a six‐cylinder diesel engine, this paper puts forward a newly designed VGEM turbocharging system. In this paper, first, the simulation of the VGEM turbocharging system has been carried out by GT‐POWER. The simulation results indicate that the brake specific fuel consumption (BSFC) can be reduced by 5·4u2005gu2005kWh−1 on the rated operation condition. Then, the simulated experiments of the VGEM turbocharging system have been performed. Two charging modes of the VGEM turbocharging system have been simulated by changing the exhaust manifold structure, from the original exhaust manifold to the newly designed exhaust manifold. The experimental results indicate that the BSFC of the VGEM turbocharging systems can be reduced by 4·7u2005gu2005kWh−1 on the rated operation...

Variable geometry exhaust manifold turbocharging system for vehicle diesel engine

A Variable Geometry Exhaust Manifold (VGEM) turbocharging system has been designed for a six-cylinder vehicle diesel engine. The VGEM turbocharging system can realise the switch between two charging modes. Experiments have been carried out on the VGEM turbocharging system. The case when the controllable valves are closed is tested by use of an original exhaust manifold. The case when the controllable valves are opened is tested by use of a newly designed exhaust manifold. Experimental results indicate that the Brake Specific Fuel Consumption (BSFC) of the VGEM turbocharging system can be reduced by 4 g/kWh on the rated operation condition.