In our previous paper, a new gas exchange concept termed divided exhaust period regulated two-stage (DEP R2S) system has been proposed. In this system, two exhaust valves in each cylinder are separately functioned with one valve feeding the exhaust mass flow into the high-pressure (HP) manifold, while the other valve evacuating the remaining mass flow directly into the low-pressure (LP) manifold. By adjusting the timing of the exhaust valves, the target boost can be controllable while improving the engine's pumping work and scavenging is attainable which results in better fuel efficiency from the gas exchange perspective. This paper will continue this study by adding an appropriate knock model to examine the benefits this concept could bring to the combustion phasing. The results at full load showed that under knock limited spark advance (KLSA) and fully optimized exhaust valve timing condition, the DEP R2S system benefited from lower pumping loss and better scavenging due to the reduced backpressure and improved pulsation interference despite suffering from reduced expansion ratio and expansion work. The combustion phasing was advanced across the engine speed which is mainly attributed to the reduced residual and the reduced requirement of gross indicated mean effective pressure (IMEP). The net brake-specific fuel consumption (BSFC) was observed to improve by up to 3% depending on the engine operating points. At part load, the DEP R2S system could be used as a mechanism to extend the “duration” of the exhaust valve. This will reduce the recompression effect of the exhaust residuals during the beginning and the end of the exhaust stroke compared to the original R2S model with late exhaust valve opening and early exhaust valve opening. In addition, increased internal exhaust gas recirculation (EGR) due to the increased overlap between the LP and the intake valve is also beneficial for the improved pumping mean effective pressure (PMEP) as the throttle can be further opened to reduce the corresponding throttling loss. The average net BSFC improvement is expected to be approximately 6–7%.

References

References
1.
Capon
,
G. C.
, “
Turbocharging the Automotive Diesel Engine
,” (to be published).
2.
Möller
,
C.
,
Johansson
,
P.
,
Grandin
,
B.
, and
Lindström
,
F.
,
2005
, “
Divided Exhaust Period—A Gas Exchange System for Turbocharged SI Engines
,”
SAE
Technical Paper No. 2005-01-1150.
3.
Hu
,
B.
,
Brace
,
C.
,
Akehurst
,
S.
,
Copeland
,
C.
, and
Turner
,
J. W. G.
,
2014
, “
Simulation Study of Divided Exhaust Period for a Regulated Two-Stage Downsized SI Engine
,”
SAE
Technical Paper No. 2014-01-2550.
4.
Turner
,
J. W. G.
,
Popplewell
,
A.
,
Ratel
,
R.
,
Johnson
,
T. R.
,
Darnton
,
N. J.
,
Richardson
,
S.
,
Bredda
,
S. W.
,
Tudor
,
R. J.
,
Bithell
,
C. I.
,
Jackson
,
R.
,
Remmert
,
S. M.
,
Cracknell
,
R. F.
,
Fernandes
,
J. X.
,
Lewis
,
A. G. J.
,
Akehurst
,
S.
,
Brace
,
C. J.
,
Copeland
,
C.
,
Martinez-Botas
,
R.
,
Romagnoli
,
A.
, and
Burluka
,
A. A.
,
2014
, “
Ultra Boost for Economy: Extending the Limits of Extreme Engine Downsizing
,”
SAE Int. J. Eng.
,
7
(
1
), pp.
387
417
.
5.
Copeland
,
C.
,
Martinez-Botas
,
R.
,
Turner
,
J.
,
Pearson
,
R.
,
Luard
,
N.
,
Carey
,
C.
,
Richardson
,
S.
,
Martino
,
P. D.
, and
Chobola
,
P.
,
2012
, “
Boost System Selection for a Heavily Downsized Spark Ignition Prototype Engine
,”
IMechE 10th International Conference on Turbochargers and Turbocharging
, London, May 15–16, pp.
27
42
.
6.
Douaud
,
A.
, and
Eyzat
,
P.
,
1978
, “
Four-Octane-Number Method for Predicting the Anti-Knock Behavior of Fuels and Engines
,”
SAE
Technical Paper No. 780080.
7.
GTI, 2014, GT-SUITE Manual,
Version 7.4.0 Build 1, Gamma Technologies Inc., Westmont, IL.
8.
Carey
,
C.
,
McAllister
,
M.
,
Sandford
,
M.
,
Richardson
,
S.
,
Pierson
,
S.
,
Damton
,
N.
,
Bredda
,
S.
,
Akehurst
,
S.
,
Brace
,
C.
,
Turner
,
J.
,
Pearson
,
R.
,
Luard
,
N.
,
Martinez-Botas
,
R.
,
Copeland
,
C.
,
Lewis
,
M.
, and
Fernandes
,
J.
,
2011
, “
Extreme Engine Downsizing
,”
Innovations in Fuel Economy and Sustainable Road Transport
, Pune, India, Nov. 8–9, pp.
135
147
.
9.
Hu
,
B.
,
Brace
,
C.
,
Akehurst
,
S.
,
Copeland
,
C.
, and
Turner
,
J. W. G.
,
2014
, “
The Effect of Divided Exhaust Period for Improved Performance in a Highly Downsized Turbocharged Engine
,”
IMechE 11th International Conference on Turbochargers and Turbocharging
, London, May 13–14, pp.
27
39
.
10.
Hu
,
B.
,
Akehurst
,
S.
,
Brace
,
C.
,
Copeland
,
C.
, and
Turner
,
J.
,
2014
, “
1-D Simulation Study of Divided Exhaust Period for a Highly Downsized Turbocharged SI Engine—Scavenge Valve Optimization
,”
SAE Int. J. Eng.
,
7
(
3
), pp.
1443
1452
.
11.
Gundmalm
,
S.
,
Cronhjort
,
A.
, and
Angstrom
,
H.
,
2013
, “
Divided Exhaust Period: Effects of Changing the Relation Between Intake, Blow-Down and Scavenging Valve Area
,”
SAE Int. J. Eng.
,
6
(
2
), pp.
739
750
.
12.
Roth
,
D.
, and
Becker
,
M.
,
2012
, “
Valve-Event Modulated Boost System: Fuel Consumption and Performance With Scavenge-Sourced EGR
,”
SAE Int. J. Eng.
,
5
(
2
), pp.
538
546
.
13.
Agarwal
,
A.
,
Jung
,
H.
,
Byrd
,
K.
,
Stein
,
R. A.
,
Kassem
,
A.
,
Whitaker
,
P.
, and
Spanner
,
C.
,
2011
, “
Blowdown Interference on a V8 Twin-Turbocharged Engine
,”
SAE Int. J. Eng.
,
4
(
1
), pp.
202
218
.
14.
Alger
,
T.
,
Chauvet
,
T.
, and
Dimitrova
,
Z.
,
2009
, “
Synergies Between High EGR Operation and GDI Systems
,”
SAE Int. J. Eng.
,
1
(
1
), pp.
101
114
.
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