stepped piston engine
TRANSCRIPT
Low mass two-cylinder engines for automotive
hybrid or range-extender applications
Dr Peter Hooper
BEng (Hons), PhD, CEng, FIMechE, PgCert, FHEA
Senior Lecturer in Mechanical Engineering
School of Engineering, Auckland University of Technology,
City Campus, WS Building, St Paul Street, Auckland, New Zealand
Messe Stuttgart, Germany 24-26 June 2014
Hybrid or Range-Extender Electric
Vehicle challenges
Hybrid Electric Vehicles (HEVs) or EVs requiring range-
extender facility need to address: -
– High mass penalty of duplicated electric and ICE powertrain
systems to further reduce CO2 emission
– Increased production cost due to provision of dual propulsion or
additional power generation systems
– Need for acceptably low NVH levels to meet demands of
modern consumers
Hybrid or Range-Extender Electric
Vehicle potential solutions
DI two-stroke cycle engines could provide potential
solutions to this requirement offering: -
– Low propulsion system mass
– Low production cost (Hooper et al, 2012)
– Low NVH compared with other comparable 2 cylinder
powerplants
– Low emissions using direct injection
– High durability using segregated charge scavenging (Hooper
et al, 2011)
– Easier potential for operation at variable compression ratios
as discussed by Turner et al (2010), Stone (2012) and
Hooper et al (2011)
Two-cylinder Crankcase-scavenged engines
Parallel twin cylinder 350LC(H) 347 cm3
modified version of Yamaha base
engine (Hooper ported)
Horizontally opposed flat twin cylinder
342 cm3 engine installed on
experimental dynamometer facility
Redesigned
cylinder block
(Image courtesy of Bernard Hooper Engineering Ltd) (Image courtesy of Bernard Hooper Engineering Ltd)
342 Flat twin engine 350LC(H) engine
Stepped Piston Engine Operating Principle
SPX Operating Principle (schematic)
ADVANTAGES
• Conventional 4 cycle wet sump
lubrication
• No valve gear
• Plain bearings
• Low thermal loading of the piston
• Low emissions with durability
• Low manufacturing costs
• Compact low mass design
• Extended oil change periods
• Fast warm up
Stepped Piston Engine
Alternative 1,2,3,4....... cylinder principles (Image courtesy of Bernard Hooper Engineering Ltd)
SPV580 UAV V-4 Engine Designed and developed under UK MoD contract
SPV580LC liquid cooled engine (air option)
Swept Volume:- 580cm³
Cylinders:- 4 (90° V-4)
Mass (kg):- 18.2 (air-cooled)
(inc stub exh) 18.5 (liquid-cooled)
Power:- 30.3kW at 5000RPM (stub exh)
35.4kW at 5250RPM (adv exh)
SFC(stub exh):- 426g/kWh -30.3kW (WOT)
347g/kWh -20kW (cruise)
SFC(adv exh):- 304g/kWh -35.4kW (WOT)
286g/kWh -20kW (cruise)
Fuel system: - Carburettor
(for all above SFC data)
Fuel:- 95 RON gasoline
(alternative 92/100RON or
JET A-1 / AVTUR kerosene)
Stepped Piston Engine
(Image courtesy of Bernard Hooper Engineering Ltd)
Inline Cylinder Stepped Piston Engines
Stepped Piston Automotive
IL3 Research Engine (Image courtesy of Bernard Hooper Engineering Ltd)
Modelling studies
predicted SFC of
0.243 kg/kWh using
VCR
Mono-block cylinder
construction
Hydro-dynamic plain shell
big end and main bearings
Stepped Pistons
Conventional four-stroke
engine type oil pump
Inline Two-cylinder Stepped Piston Charged
Engine
290cm3 Industrial Marine Generator engine
(2 cylinder version of SPV580 engine) (Image courtesy of GIL Marine/Bernard Hooper Engineering Ltd)
Computational models under development and
analysis for application of Direct Injection
350LC(H) Parallel twin cylinder engine
UMA290 stepped piston twin cylinder engine
342 Flat twin cylinder engine
WAVE Computational models of 342 Flat twin, 350LC(H) and UMA290 engines currently
under development and analysis for further investigation of Direct Injection
Experimental Specific Performance Comparisons
Specific full load performance comparison of 342 Flat twin with 350LC(H) and UMA290 180° Parallel
twin experimental engines (with expected UMA290 SFC after application of Direct Injection)
342 Flat twin
Power
UMA290
350LC(H)
342 Flat twin
SFC
UMA290 350LC(H)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
0
10
20
30
40
50
60
70
0 2000 4000 6000 8000
SF
C (
kg
/kW
h)
Sp
ecif
ic P
ow
er
(kW
/lit
re)
Engine Speed (RPM)
Anticipated full
load SFC of
UMA290 engine
with DI
Full load
SFC with
simple inlet
fuel delivery
methods
Torque Fluctuation Characteristics
Torque fluctuation is influenced by:-
The resultant computation of these forces, incrementally
throughout the engine cycle, allows calculation of the
instantaneous turning moment at the crankshaft.
Inertia Forces
Gas Forces
Input Data for Computation
• Cylinder bore diameter
• Stroke
• Connecting rod centre distance
• Engine speed
• Reciprocating mass
• Compression ratio
• Timing of exhaust valve/port timing
• Maximum combustion pressure
Torque Fluctuation Factor
• Operating cycles
• Numbers of cylinders
This method of analysis can be used to compare engines of
differing:-
• Design configurations
Torque Fluctuation Factor
Where: Tp-p = Peak to Peak Torque
Tm = Mean Torque
m
pp
fT
T T
Non dimensional comparator
Torque Fluctuation – FLAT TWIN 2 CYCLE
-200
-100
0
100
200
300
0 90 180 270 360 450 540 630 720
TU
RN
ING
MO
ME
NT
(N
m)
ANGLE AFTER TDC ON FIRST CYLINDER (°)
CRANKCASE SCAVENGED 342 cm³ 2 CYCLE FLAT TWIN 16.3 kW/ 7000 RPM
Torque Fluctuation Comparison
Engine Type
Torque (Nm)
Pk-Pk
/mean
Factor
Mean
Pk-Pk
2 cycle flat twin
22.0
248.9
11.31
Torque Fluctuation – PARALLEL TWIN 2 CYCLE
-200
-100
0
100
200
300
0 90 180 270 360 450 540 630 720
TU
RN
ING
MO
ME
NT
(N
m)
ANGLE AFTER TDC ON FIRST CYLINDER (°)
CRANKCASE SCAVENGED 347 cm³ 350LC(H) -180° 2 CYLINDER 19.5 kW/5500 RPM
Torque Fluctuation Comparison
Engine Type
Torque (Nm)
Pk-Pk
/mean
Factor
Mean
Pk-Pk
2 cycle flat twin
2 cycle parallel twin
22.0
248.9
11.31
37.7
76.1
2.02
Torque Fluctuation – PARALLEL TWIN
STEPPED PISTON
-200
-100
0
100
200
300
0 90 180 270 360 450 540 630 720
TU
RN
ING
MO
ME
NT
(N
m)
ANGLE AFTER TDC ON FIRST CYLINDER (°)
STEPPED PISTON 290 cm³ UMA290 -180° 2 CYLINDER 17.7 kW/5250 RPM
Torque Fluctuation Comparison
Engine Type
Torque (Nm)
Pk-Pk
/mean
Factor
Mean
Pk-Pk
2 cycle flat twin
2 cycle parallel twin
22.0
248.9
11.31
Stepped piston parallel twin
37.7
76.1
2.02
32.2
63.4
1.97
Torque Fluctuation – INLINE 4 CYLINDER 4 CYCLE
-200
-100
0
100
200
300
0 90 180 270 360 450 540 630 720
TU
RN
ING
MO
ME
NT
(N
m)
ANGLE AFTER TDC ON FIRST CYLINDER (°)
4 CYCLE INLINE 4 CYLINDER 40 kW/5000 RPM
Torque Fluctuation Comparison
Engine Type
Torque (Nm)
Pk-Pk
/mean
Factor
Mean
Pk-Pk
2 cycle flat twin
2 cycle parallel twin
22.0
248.9
11.31
Stepped piston parallel twin
4 cycle inline 4 cylinder
37.7
76.1
2.02
32.2
63.4
1.97
76.4
338.5
4.43
38.2
291.0
7.61
4 cycle inline 2 cylinder
Torque Fluctuation – V-4 CYLINDER
STEPPED PISTON (SPV580)
-200
-100
0
100
200
300
0 90 180 270 360 450 540 630 720
TU
RN
ING
MO
ME
NT
(N
m)
ANGLE AFTER TDC ON FIRST CYLINDER (°)
V-4 STEPPED PISTON ENGINE 35.4 kW/5250 RPM
Torque Fluctuation Comparison
Engine Type
Torque (Nm)
Pk-Pk
/mean
Factor
Mean
Pk-Pk
2 cycle flat twin
2 cycle parallel twin
22.0
248.9
11.31
Stepped piston parallel twin
4 cycle inline 4 cylinder
SPV580 V-4 Cylinder
37.7
76.1
2.02
32.2
63.4
1.97
76.4
338.5
4.43
80.2
64.4
0.80
38.2
291.0
7.61
4 cycle inline 2 cylinder
Engine running 4000RPM
cruise condition
Engine shutdown
Torque Fluctuation (SPV580)
(Images courtesy of Bernard Hooper Engineering Ltd)
Conclusions to date
For Hybrid Electric Vehicles or Range extender RE-EVs : -
– DI two-stroke cycle engines could potentially offer powerplant
systems with high thermal efficiency addressing further CO2
emission reduction strategies
– Use of segregated scavenging addresses durability concerns of
conventional two-stroke cycle engines
– 90° V-4 cylinder stepped piston engine offers attractive very low
NVH characteristics
– 180° parallel twin cylinder configurations offer good compromise
of: -
– Good NVH characteristics compared with other two cylinder units
– Low manufacturing cost
– For non-steady state RE-EV operation VCR could offer further
CO2 reduction
References Hooper, P.R., Al-Shemmeri, T and Goodwin, M.J. (2011) – "Advanced modern low emission two-stroke cycle
engines” (Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile
Engineering. Vol. 225 No.11, November 2011)
Stone, R .(2012) – “Introduction to Internal Combustion Engines”, (4th Edition Palgrave MacMillan) ISBN:
9781137028297 (2012))
Turner, J., Blundell, D., Pearson, R., Patel, R., Larkman, D., Burke, P., Richardson, S., Green, N.
M., Brewster, S., Kenny, R and Kee, R. (2010) – " Project Omnivore: a variable compression ratio ATAC 2-
stroke engine for ultra-wide-range HCCI operation on a variety of fuels”. SAE paper 2010-01-1249, 201
Hooper, P.R., Al-Shemmeri, T and Goodwin, M.J. (2012) – "An experimental and analytical investigation of a
multi-fuel stepped piston engine” (Journal of Applied Thermal Engineering April 2012)
<http://dx.doi.org/10.1016/j.applthermaleng.2012.04.034>