stepped piston engine

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)


CRANKCASE SCAVENGED 347 cm³ 350LC(H) -180° 2 CYLINDER 19.5 kW/5500 RPM


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)


STEPPED PISTON 290 cm³ UMA290 -180° 2 CYLINDER 17.7 kW/5250 RPM


Engine Type

Torque (Nm)

Pk-Pk

/mean

Factor

Mean

Pk-Pk

2 cycle flat 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)


4 CYCLE INLINE 4 CYLINDER 40 kW/5000 RPM


Engine Type

Torque (Nm)

Pk-Pk

/mean

Factor

Mean

Pk-Pk

2 cycle flat twin


22.0

248.9

11.31


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


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)


V-4 STEPPED PISTON ENGINE 35.4 kW/5250 RPM


Engine Type

Torque (Nm)

Pk-Pk

/mean

Factor

Mean

Pk-Pk

2 cycle flat twin


22.0

248.9

11.31



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


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>

stepped piston engine

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