Utilizing Production Viable Valve Strategies at Elevated Speeds and Loads to Improve Volumetric Efficiency via Intake Valve Modulation

Kalen R Vos,James Mccarthy,Gregory M Shaver,Lisa Farrell

doi:10.3389/fmech.2018.00002

Abstract

Valvetrain flexibility enables the optimization of the engine’s ability to breathe across the operating range, resulting in more efficient operation. The authors have shown the merit of improving volumetric efficiency via valvetrain flexibility to improve fuel efficiency at elevated engine speeds in previous work. This study focuses on production viable solutions targeting similar volumetric efficiency benefits via delayed intake valve closure at these elevated engine speeds. Specifically, the production viable solutions include reducing the duration at peak lift, as well as reducing the amount of hardware required to achieve a delayed intake closure timing. It is demonstrated through simulation that delayed intake valve modulation at an elevated speed (2200 RPM) and load (12.7 bar BMEP) is capable of improving volumetric efficiency via a production viable lost motion enabled boot profile shape. Phased and dwell profiles were also evaluated. These profiles were compared against each other for two separately simulated cases: 1) modulating both intake valves per cylinder, and 2) modulating one of the two intake valves per cylinder. The boot, phase, and dwell profiles demonstrate volumetric efficiency improvements of up to 3.33%, 3.41%, and 3.5% respectively for two valve modulation, while realizing 2.79%, 2.59%, and 3.01% respectively for single valve modulation. As a result, this paper demonstrates that nearly all of the volumetric efficiency benefits achieved while modulating IVC via dwell profiles are possible with production viable boot and phased profiles

Highlights

Variable valve actuation (VVA) enables intake and exhaust valve modulation to directly impact the gas exchange process of an engine (Payri et al, 2014)
Lancefield and Methley (2000) implemented a model to analyze early intake valve closing (EIVC) and late intake valve closing (LIVC) timings coupled with variable geometry turbine (VGT) and exhaust gas recirculation (EGR) settings on a light-duty engine and demonstrated that the amount of inducted charge mass can be altered via intake valve closure (IVC) timing modulation, resulting in variations in volumetric efficiency
IVC modulation is commonly cited as a strategy for altering volumetric efficiency through increased dwell at peak lift of the profile

Summary

Introduction

Variable valve actuation (VVA) enables intake and exhaust valve modulation to directly impact the gas exchange process of an engine (Payri et al, 2014). The work described in this article demonstrates production viable methods that include reducing the peak lift duration, as well as requiring less hardware to obtain volumetric efficiency benefits at elevated engine speeds via intake valve closure (IVC) modulation. Production Viable IVC Modulation demonstrated experimentally that late IVC realizes a 2–5% increase in volumetric efficiency, enabling a 1.2–1.9% improvement in BSFC at elevated engine speeds for a medium-duty diesel engine. Volumetric efficiency improvements enabled a decrease in BSFC via exhaust gas recirculation (EGR) and start of injection (SOI) optimization without penalizing BSNOx emissions (Vos et al, 2017). Lancefield and Methley (2000) implemented a model to analyze EIVC and LIVC timings coupled with VGT and EGR settings on a light-duty engine and demonstrated that the amount of inducted charge mass can be altered via IVC timing modulation, resulting in variations in volumetric efficiency. The models estimated volumetric efficiency for different IVC timings, engine speeds, and manifold pressures. Benajes et al (2009) discuss the ability to control in-cylinder thermodynamic conditions, namely ECR and the total intake mass flow, using IVC modulation

Methods

Results

Conclusion