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Experimental investigation of the air–fuel charging process in a four-valve supercharged two-stroke cycle GDI engine

  • Macklini Dalla NoraEmail author
  • Thompson Diórdinis Metzka Lanzanova
  • Mario Eduardo Santos Martins
  • Paulo Romeu Moreira Machado
  • Hua Zhao
Technical Paper
  • 42 Downloads

Abstract

Fuel consumption standards imposed in several countries for the next years have prompted the development of hybrid passenger cars with ever smaller internal combustion engines. In such powertrain, fuel consumption is as important as engine packaging and power density, so two-stroke engines may be an option due to their higher combustion frequency compared to four-stroke engines. Therefore, the present research investigates the air–fuel charging process of an overhead four-valve direct injection supercharged engine operating in the two-stroke cycle. The optimum start of fuel injection was evaluated for commercial gasoline by means of indicated and combustion efficiencies where a trade-off was found between early and late fuel injections. By advancing the injection timing, more fuel was prone to short circuit to the exhaust during the valve overlap, while late injections resulted in poor charge preparation. The gas exchange parameters, i.e. charging and trapping efficiencies, were obtained from seventy operating points running at fuel-rich conditions. The Benson–Brandham mixing-displacement scavenging model was then fit to the experimental data with a coefficient of determination better than 0.95. With such model, the air trapping and charging efficiencies could be estimated solely based on the scavenge ratio and exhaust lambda, regardless of the engine load, speed, or air/fuel ratio employed. Further twenty-five different lean-burn testing points were tested to certify the proposed methodology applied to the poppet valve two-stroke engine. The in-cylinder lambda was calculated and found different from the exhaust lambda due to mixing between burned gases and intake air during the scavenging process.

Keywords

Two-stroke cycle engine Overhead poppet valves Fuel injection timing Gasoline direct injection Benson–Brandham scavenging model Lean-burn combustion 

Abbreviations

ATDC

After top dead centre

CA

Crank angle

CE

Charging efficiency

DI

Direct injection

EGR

Exhaust gas recycling

EVC

Exhaust valve closing

EVO

Exhaust valve opening

GDI

Gasoline direct injection

IMEP

Indicated mean effective pressure

IVC

Intake valve closing

IVO

Intake valve opening

K

Water–gas equilibrium constant

LHVfuel, LHV

Lower heating value of fuel

\({\text{LHV}}_{{{\text{H}}_{ 2} }}\)

Lower heating value of hydrogen

LHVC

Lower heating value of solid carbon

LHVCO

Lower heating value of carbon monoxide

LHVUHC

Lower heating value of unburned hydrocarbons

mair

Intake air mass per cycle

\(m_{{{\text{trap }}\;{\text{air}}}}\)

In-cylinder trapped air mass per cycle

\(\dot{m}_{\text{air}}\)

Air mass flow rate

\(\dot{m}_{\text{fuel}}\)

Fuel mass flow rate

\(\dot{m}_{\text{soot}}\)

Mass flow rate of soot

\(\dot{m}_{\text{CO}}\)

Mass flow rate of carbon monoxide

\(\dot{m}_{{{\text{H}}_{2} }}\)

Mass flow rate of hydrogen

\(\dot{m}_{\text{UHC}}\)

Mass flow rate of unburned hydrocarbons

NOx

Oxides of nitrogen

PFI

Port fuel injection

rpm

Revolutions per minute

R2

Coefficient of determination

SCair

Air short-circuiting

SI

Spark ignition

SOI

Start of fuel injection

SR

Scavenge ratio

SRpd

Scavenge ratio of perfect displacement

TEair

Air trapping efficiency

TEfuel

Fuel trapping efficiency

TWC

Three-way catalyst

UHC

Unburned hydrocarbons

Vclr

Clearance volume

Vivc

In-cylinder volume at intake valve closure

y

Hydrogen-to-carbon ratio

[CO]

Volumetric exhaust carbon monoxide concentration

[NOx]

Volumetric exhaust nitrogen oxides concentration

[soot]

Soot concentration

[UHC]

Volumetric exhaust unburned hydrocarbons concentration

ηc

Combustion efficiency

λ

Relative air/fuel ratio (lambda)

λcyl

In-cylinder lambda

λexh

Exhaust lambda

ρint

Intake air density

Notes

Acknowledgements

The first and second authors would like to acknowledge the Brazilian council for scientific and technological development (CNPq–Brasil) for supporting their PhD studies at Brunel University London.

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Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2019

Authors and Affiliations

  1. 1.Engines Research Group (GPMOT)Federal University of Santa MariaSanta MariaBrazil
  2. 2.Centre for Advanced Powertrain and Fuels Research (CAPF)Brunel University LondonUxbridgeUK

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