Study of the Miller Cycle on a Turbocharged DI Gasoline Engine Regarding Fuel Economy Improvement at Part Load

Xuewei Pan,Yinghua Zhao,Diming Lou,Liang Fang

doi:10.3390/en13061500

Abstract

This contribution is focused on the fuel economy improvement of the Miller cycle under part-load characteristics on a supercharged DI (Direct Injection) gasoline engine. Firstly, based on the engine bench test, the effects with the Miller cycle application under 3000 rpm were studied. The results show that the Miller cycle has different extents of improvement on pumping loss, combustion and friction loss. For low, medium and high loads, the brake thermal efficiency of the baseline engine is increased by 2.8%, 2.5% and 2.6%, respectively. Besides, the baseline variable valve timing (VVT) is optimized by the test. Subsequently, the 1D CFD (Computational Fluid Dynamics) model of the Miller cycle engine after the test optimization at the working condition of 3000 rpm and BMEP (Brake Mean Effective Pressure) = 10 bar was established, and the influence of the combined change of intake and exhaust valve timing on Miller cycle was studied by simulation. The results show that as the effect of the Miller cycle deepens, the engine’s knocking tendency decreases, so the ignition timing can be further advanced, and the economy of the engine can be improved. Compared with the brake thermal efficiency of the baseline engine, the final result after simulation optimization is increased from 34.6% to 35.6%, which is an improvement of 2.9%.

Highlights

As one of the main means of transportation in people’s lives, cars have become an indispensable part of modern life
The results show that as the effect of the Miller cycle deepens, the engine’s knocking tendency decreases, so the ignition timing can be further advanced, and the economy of the engine can be improved
Compared with the brake thermal efficiency of the baseline engine, the final result after simulation optimization is increased from 34.6% to 35.6%, which is an improvement of 2.9%

Summary

Introduction

As one of the main means of transportation in people’s lives, cars have become an indispensable part of modern life. The dramatic increase in the number of cars poses a huge challenge to the environment and energy, causing increasingly stringent fuel consumption regulations. To ensure that the engine has sufficient output torque at high load, turbocharging technology is often used, which increases the tendency of knock during the high-load operation. To solve this problem, a common solution is to delay the ignition advance angle; another way is to reduce the geometric compression ratio of the engine, but these strategic or structural changes make it difficult for the engine to achieve optimal thermal efficiency, which in turn sacrifices the fuel economy of the engine [1]

Methods

Results

Conclusion