(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)(19) World Intellectual Property Organization
International Bureau

11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111(10) International Publication Number(43) International Publication Date

22 September 2011 (22.09.2011)

PCT(51) International Patent Classification:
F02B 33122 (2006.01)(21) International Application Number:
PCT/US20ll/028274(22) International Filing Date:

WO 2011/115866 A1(72) Inventors: MELDOLESI, Riccardo; 55 New Road,
Shoreham-by-sea, West Sussex BN43 6RB (GB).
BADAIN, Nicholas; 37 Rosslyn Road, Shoreham-by-sea,West Sussex BN43 6WL (GB). GILBERT, Ian; 67
Beach Green, Shoreham-by-sea, West Sussex BN43 5YE(GB).

14 March 2011 0 4 ·03 ·2011 ) (74) Agents: FILDES, Christopher, J. et al.; Fildes & OutEnglish
land, P.C., 20916 Mack Avenue, Suite 2, Grosse Pointe(25) Filing Language:
Woods, MI 48236 (US).
(26) Publication Language:
English(81) Designated States (unless otherwise indicated, for every(30) Priority Data:kind of national protection available): AE, AG, AL, AM,
15 March 2010 (15.03.2010)
61/313,831
us
AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ,
61/363,825
13 July2010 (13.07.2010)
us
CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO,
18 July2010 (18.07.2010)61/365,343
us
DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT,
HN, HR, HU, ID, IL, IN, IS, JP, KE, KG, KM, KN, KP,(71) Applicant (for all designated States except US): SCUDKR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD,
ERI GROUP, LLC [US/US]; llll Elm Street, Suite 33,
ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI,
West Springfield, MA 01089 (US).
NO, NZ, OM, PE, PG, PH, PL, PT, RO, RS, RU, SC, SD,- ------------------------------------------------------------------------------------------- FIG. 1[Continued on next page];;;;;;;;;;;;;;;(54) Title: SPLIT-CYCLE ENGINE WITH HIGH RESIDUAL EXPANSION RATION(57) Abstract: An engine includes a rotatable crankshaft. A compression piston
is slidably received within a compression cylinder and operatively connected tothe crankshaft. An expansion piston is slidably received within an expansion
cylinder and operatively connected to the crankshaft. A crossover passage interconnects the compression and expansion cylinders. The crossover passage includes a crossover expansion (XovrE) valve disposed therein. In an Engine Firing (EF) mode of the engine, the engine has a residual expansion ratio at XovrE
valve closing of 10.0 to I or greater, and more preferably 15.7 to I or greater.

--;;;;;;;;;;;;;;;-

12

W 0 2011/115866 A1 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR,
TT, TZ, UA, UG, US, UZ, VC, VN, ZA, ZM, ZW.

EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU,
LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK,
SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ,
GW, ML, MR, NE, SN, TD, TG).

(84) Designated States (unless otherwise indicated, for every
kind of regional protection available): ARIPO (BW, GH,
GM, KE, LR, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, Published:
ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, with international search report (Art. 21 (3))TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK,

wo 2011/115866

PCT/US2011/028274

1

SPLIT-CYCLE ENGINE WITH HIGH RESIDUAL EXPANSION RATIOTECHNICAL FIELD

This invention relates to split-cycle engines and,more particularly,
5

expansion

ratio

to such an engine having a high residualand optionally incorporating an

air-hybrid

system.

BACKGROUND OF THE INVENTION

10

For
engine"15

aspurposes

used

in

of

the

clarity,presentthetermapplicationinternal combustion engine wherein all

four

well- known

Otto

intakecompression,

expansion

cycle"conventional(i.e.,

the(or power)referstoanstrokes of the(orinlet) ,and exhaust strokes)

arecontained in each piston/cylinder combination of the engine.
Each stroke requires

one half revolution of the crankshaft(180 degrees crank angle
the crankshaft(CA)),and two full revolutions of(720 degrees CA)

are required to complete theentire Otto cycle in each cylinder of a conventional engine.
20

Also,

for

purposes

definition is offered forofclarity,thefollowing

the term "split-cycle engine" as

may be applied to engines disclosed in the prior art and as
referred to in the present application.
A
25

split-cycle

engineasreferredtohereincomprises:
a crankshaft rotatable about a crankshaft axis;acompression
crankshaft

30

compression
cylinder
such

that

pistonslidablyreceived

withinandoperatively

connected

tothecompression

pistonathe

reciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft;wo 2011/115866

PCT/US2011/028274

2

anwithinexpansionan expansion(power)cylinderpistonslidablyreceived

and operatively connected tothe crankshaft such that the expansion piston reciprocatesthrough an expansion stroke and an exhaust stroke during a5single rotation of the crankshaft; andacrossoverpassage(port)

compression and expansion cylinders,
including

at

least

a

crossoverinterconnecting

thethe crossover passage

expansion(XovrE)

valve

disposed therein, but more preferably including a crossover
10compression(XovrC)valve and a crossover expansion(XovrE)valve defining a pressure chamber therebetween.
United States
8,6,543,225 granted April

2003 to Scuderi and United States

granted October 11,
15

Patent No.

Patent No.

2005 to Branyon et al.,are incorporated herein by reference,
discussion
addition,ofsplit-cycle

and6, 952,923

both of whichcontain an extensive

similar-type

engines.

In

these patents disclose details of prior versionsof an engine of which the present disclosure details further
developments.
20

Split-cycle
cycle

enginewithanair-hybrid
airengines

reservoir

combineand variousasplit-

controls.

This combination enables a split-cycle air-hybrid engine to
store

energyreservoir.
25

in

the

form

of

compressed

air

in

the

air

The compressed air in the air reservoir is later

used in the expansion cylinder to power the crankshaft.
A split-cycle

air-hybrid

engineasreferredtoherein comprises:
a crankshaft rotatable about a crankshaft axis;
a30

compression
crankshaft

compression
cylinder
such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft;wo 2011/115866

PCT/US2011/028274

3

anwithinexpansionan expansion(power)cylinderpistonslidablyreceived

and operatively connected tothe crankshaft such that the expansion piston reciprocatesthrough an expansion stroke and an exhaust stroke during a5single rotation of the crankshaft;acrossoverpassage(port)

compression and expansion cylinders,
including

at

least

a

crossoverinterconnecting

thethe crossover passage

expansion(XovrE)

valve

disposed therein, but more preferably including a crossover
10compression(XovrC)valve and a crossover expansion(XovrE)valve defining a pressure chamber therebetween; andancrossoverairreservoir

passageandoperatively

selectively

connected

operable

to

to

the
store

compressed air from the compression cylinder and to deliver
15

compressed air to the expansion cylinder.
United States
8,

20

Patent No.

2 0 0 8 to Scuderi et al.,7,353,786 granted April

which is incorporated herein byreference,contains an extensive discussion of split-cycle

air-hybrid

andsimilar-type

patent discloses details

engines.

In

addition,of prior hybrid systems

thisof whichthe present disclosure details further developments.
A split-cycle air-hybrid engine can benormal operating or firing
the25

Enginemodes.

Firing(EF)

In the EF mode,

mode)

reservoir.

connecting

mode
and

(also commonly called
four

basic

air-hybrid

operating without the use of its

In the EF mode,

the

in a

the engine functions as a non-air

hybrid split-cycle engine,
air

(NF)

run

crossoverpassageatank valve operatively
to

the

air

reservoir

remains closed to isolate the air reservoir from the basic
30

split-cycle engine.
The

split-cycle

air-hybrid

engineoperates

the use of its air reservoir in four hybrid modes.
hybrid modes are:with

The fourwo 2011/115866

PCT/US2011/028274

4

Air

1)

Expandercompressed

(AE)

air

mode,

energy

which

from

includes

the

air

using

reservoir

without combustion;
2)
5

Air Compressor(AC)compressedenergyairmode,which includes

into

the

air

storing

reservoir

without combustion;
3)

Air Expander and Firing (AEF) mode, which includes
using compressed air energy from the air reservoir
with combustion; and10

4)Firingandstoring

Charging

compressed

(FC)
air

mode,

which

includesenergy

into

the

air

AE,

AC,

reservoir with combustion.
However,further

AEF and FC,
15

optimization of these modes,EF,

is desirable to enhance efficiency and reduce

emissions.

SUMMARY OF THE INVENTION

The
20

present

invention

providesaengine in which the use of the Engine Firing

split-cycle(EF)mode isoptimized for potentially any vehicle in any drive cycle for
improved efficiency.
More particularly,

an exemplary embodiment of anengine in accordance with the present invention includes a25

crankshaft rotatable about a crankshaft axis.
pistonisslidably received within

and operatively connected tothea

A compression

compression

crankshaft

cylindersuch thatthecompression piston reciprocates through an intake stroke anda30compression

crankshaft.
anduringasinglerotationoftheAn expansion piston is slidably received within

expansion

crankshaft

strokecylinder

such

that

and

operatively

theexpansionconnected

pistontothereciprocatesthrough an expansion stroke and an exhaust stroke during a

wo 2011/115866

PCT/US2011/028274

5

singlerotationofthecrankshaft.

A crossover

passageinterconnects the compression and expansion cylinders.
crossoverpassageincludesvalve disposed therein.
5

Firing (EF) mode.
expansion

ratio

a

crossover

expansion

The(XovrE)The engine is operable in an Engine

In the EF mode, the engine has a residual
at

XovrE

valve

closing

of

10.0

to

1

or

greater, and more preferably 15.7 to 1 or greater.
A method of operating an engine is also disclosed.
The
10

engineincludescrankshaft axis.

acrankshaft

rotatable

about

a

A compression piston is slidably received

within a compression cylinder and operatively connected tothe crankshaft such that the compression piston reciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft.
15

slidablyreceived

operatively
expansion
andanconnected

pistonexhaustcrankshaft.
20

to

an

expansionthecrankshaft

reciprocatesstrokeA

throughduringcrossoveracrossover

such

and

that

the

expansion

strokesinglerotationoftheinterconnects

thepassage

expansion

cylinderancompression and expansion cylinders.

The crossover passage

includesatherein.

The engine is operable in an Engine Firing

mode.

(XovrE)

valve

disposed(EF)

The method in accordance with the present invention

includes25

withinAn expansion piston isthefollowing

steps:

drawing in and compressing

inlet air with the compression piston; admitting compressed
air

from

the

compression

cylinder

into

the

expansion

cylinder with fuel, at the beginning of an expansion stroke,
the

fuel

being

ignited,burnedandexpanded

on

the

same

expansion stroke of the expansion piston, transmitting power
30

to

the

crankshaft,

and

the

combustion

products

beingdischarged on the exhaust stroke; and maintaining a residual
expansion

ratio

at

XovrE

valve

closingofgreater, more preferably 15.7 to 1 or greater.

10.0

to

1

or

wo 2011/115866

PCT/US2011/028274

6

These

and

other

invention will be morefeaturesandadvantages

fully understood from the

of

the

followingdetailed description of the invention taken together with theaccompanying drawings.
5

BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings:
FIG. 1 is a lateral sectional view of an exemplary
10

split-cycle air-hybrid engine in accordance with the present
invention;
FIG.

2 is a graphical illustration of a preferred

exemplary range of residual expansion ratio
volumetric15

crossover

expansion

ratio)

expansion(XovrE)

versusvalve

in(i.e.,

closing

effective

angle

accordance

of

with

a
the

present invention;
FIG.

3 is a graphical illustration of inlet valve

opening timing with respect to engine speed and load;
FIG.
20

4 is a graphical illustration of inlet valve

closing timing with respect to engine speed and load;
FIG.

5 is a graphical illustration of inlet valve

duration with respect to engine speed and load;
FIG.
compression
25

6

is

(XovrC)agraphical

valve

opening

illustration
timingwithofcrossoverrespect

toengine speed and load;
FIG.

7 is a graphical illustration of XovrC valve

closing timing with respect to engine speed and load;
FIG.

8 is a graphical illustration of XovrC valve

duration with respect to engine speed and load;
30

FIG.

9 is a graphical illustration of XovrE valve

opening timing with respect to engine speed and load;
FIG. 10 is a graphical illustration of XovrE valve
closing timing with respect to engine speed and load;wo 2011/115866

PCT/US2011/028274

7FIG.

11 is a graphical illustration of XovrE valve

duration with respect to engine speed and load;
FIG.

12

is

a

graphical

illustrationof

exhaustvalve opening timing with respect to engine speed and load;
5

FIG.

13

is

a

graphical

illustrationof

exhaustvalve closing timing with respect to engine speed and load;
and
FIG.

14

is

a

graphical

illustrationof

exhaustvalve duration with respect to engine speed and load.
10

DETAILED DESCRIPTION OF THE INVENTION

The following glossary of acronyms and definitionsof terms is provided for reference.
15

In General
Unless otherwise specified,closing timings

are measured

inall valve opening andcrank angle

degrees

after

top dead center of the expansion piston (ATDCe) .
Unless20

otherwise

are in crank angle degrees
Air tank

specified,

all

valve

durations(CA).

(or air storage tank):

Storage tank for compressed

air.
ATDCe: After top dead center of the expansion piston.
Bar: Unit of pressure, 1 bar = 10 5 N/m 2
25

BMEP:

Brake

mean

effective

pressure.

referstotheoutputas

outputshaft),

after

frictionfor.

Brake Mean Effective Pressuredeliveredtolosses

The
the

term

crankshaft(FMEP)(BMEP)"Brake"are(oraccounted

is the engine's

brake torque output expressed in terms of a mean effective
30

pressure
divided(MEP)
byparameter
Accordingly,

value.

BMEP

isenginedisplacement.

taken

after

the

BMEP=IMEP-friction.

equal
This
losses

to

the

brake

torqueistheperformance

due

to

friction.

Friction,in this case iswo 2011/115866

PCT/US2011/028274

8usually also expressed in termsof an MEP value

known

as

Frictional Mean Effective Pressure (or FMEP)
Compressor:

The

compression

cylinderandits

associatedcompression piston of a split-cycle engine.
5

Exhaust (or EXH) duration: Exhaust valve duration.
Exhaust (or EXH) valve: Valve controlling outlet of gas fromthe expander cylinder.
Expander:The

expansion

cylinderandits

associatedexpansion piston of a split-cycle engine.
10

IMEP:

Indicated

Mean

Effective

Pressure.

The

term

"Indicated" refers to the output as delivered to the top of
the piston, before friction losses (FMEP) are accounted for.
RPM: Revolutions Per Minute.
Tank
15

valve:

Valve

connecting

the

Xovr

passagewith

thecompressed air storage tank.
Valve duration: The interval in crank degrees between startof valve opening and end of valve closing.
VVA:

Variable

operable
20

to

valve

alter

actuation.

A

shape

timingtheormechanism
of

a

or

methodvalve's

lift

profile.
Xovr(orXover)

valve,

passage

or

port:

The

crossovervalves, passages, and/or ports which connect the compression
andexpansion

cylindersthrough

which

gas

flows

from

compression to expansion cylinder.
25

XovrC

(or XoverC)

valves:Valves at

the compressor end of

the Xovr passage.
XovrC Duration: The interval in crank degrees between startof XovrC valve opening and end of XovrC valve closing.
XovrE
30

(or XoverE) valves: Valves at the expander end of thecrossover (Xovr) passage.
XovrE duration: The interval in crank degrees between startof XovrE valve opening and end of XovrE valve closing.

wo 2011/115866

PCT/US2011/028274

9

Referring to FIG. 1, an exemplary split-cycle airhybrid engine is shown generally by numeral 10.

The split-

cycle air-hybrid engine 10 replaces two adjacent cylindersof5aconventional

enginewithacombinationofcompression cylinder 12 and one expansion cylinder 14.

oneAcylinder head 33 is typically disposed over an open end of
the expansion and compression cylinders 12,

14 to cover andseal the cylinders.
The
10

four

strokes

of

the

Otto

cycle

are

"split"over the two cylinders 12 and 14 such that the compression
cylinder 12, together with its associated compression piston
20,

15

performtheintakeandpistonstrokes.

The Otto cycle is therefore completed in these twocylinders

12,

once

per

the

its

the

expansion

performwithandcylinder30,

togetherstrokes,

expansion

14

14,

compression

expansion

crankshaft

16

associatedandexhaustrevolution(360

degrees CA) about crankshaft axis 17.
During the intake stroke, intake air is drawn into
the20

compression

disposedinthecylinder12throughcylinder

head

33.

an

intake

port

19

An

inwardly

opening(opening inwardly into the cylinder and toward the piston)poppet intake valve 18 controls fluid communication between
the intake port 19 and the compression cylinder 12.
During25

piston20

chargeinto

thepressurizes
thecompression
the

air

stroke,chargecrossover passage

and

the

drives(or port)

typically disposed in the cylinder head 33.

compression

22,

the

air

which

is

This means thatthe compression cylinder 12 and compression piston 20 are asource30ofhigh-pressure

gas

to

the

crossoverpassage22,

which acts as the intake passage for the expansion cylinder
14.

In some embodiments,

two or more crossover passages 22

interconnect the compression cylinder 12 and the expansion
cylinder 14.

wo 2011/115866

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10
The geometric5(or volumetric)

thecompression

cylinder

12

of

for

split-cycle

enginesingeneral)referred

to

as

the

engine.

The geometriccompression ratio ofsplit-cycle"compressionishereinoftheratio"(or volumetric)

engine(andcommonly

split-cycle

compression ratio of

the expansion cylinder 14 of split-cycle engine 10
split-cycle engines in general)

10(and foris herein commonly referred

to as the "expansion ratio" of the split-cycle engine.
geometric compression ratio of a10

the art as the ratio of the enclosedthecylinderreciprocating

15

cylinder is well(including
therein

is

all
at

(or trapped)

recesses)itsbottomknown involume in

when
dead

The

a

pistoncenter(BDC)

position to the enclosed volume(i.e.,

clearance volume)thesaid piston

is

at

its

Specificallyfor

split-cycle

cylinder

(TDC)

when

position.

definedherein,thecompression

ratio

top

of

dead

centerenginesainascompression

cylinder is determined when the XovrC valve is closed.

Also

specifically for split-cycle engines as defined herein,

theexpansion ratio of an expansion cylinder is determined when20

the XovrE valve is closed.
Due to very high compression ratios
1,

25

30

20

to

1,

40

to

or

greater)withinthecylinder12,anoutwardly

opening(opening

outwardly

from thecylinder and piston)(XovrC)to1,(e.g.,

poppettocompressionawaycrossover compression

valve 24 at the crossover passage inlet 25 is used

control

flow

from

crossoverpassage(e.g.,

to

20

1,

22.
30

to

the

compression

Due
1,

to

40

very

to

1,

cylinder
high

12

into

expansionor greater)theratioswithintheexpansion cylinder 14, an outwardly opening poppet crossover
30

expansion(XovrE) valve 26 at the outlet 27 of the crossover

passage 22 controls flow from the crossover passage 22 into
the expansion cylinder 14.

The actuation rates and phasingof the XovrC and XovrE valves 24,

26 are timed to maintainwo 2011/115866

PCT/US2011/028274

11

pressure

inthecrossoverpassage

22

at

a

high

minimumpressure(typically 20 bar or higher at full

load)

duringall four strokes of the Otto cycle.
At5

least onefuelinjector 2 8 injects

fuel

into

the pressurized air at the exit end of the crossover passage
22 in correspondence with the XovrE valve 26 opening, which
occursshortly before expansion piston 30

deadcenterposition.

The

air/fuel

reacheschargeits

topenterstheexpansion cylinder 14 when expansion piston 30 is close to
10

its

top

dead

centerposition.

descent

fromits

dead center position,

top

XovrE valve 26 is still open,aspark plug

tip

39

that

As

piston30

beginsits

and whilethespark plug 32, which includes

protrudes

intocylinder14,isfired to initiate combustion in the region around the spark
15

plug

tip

39.

Combustion

can

be

initiated

while

the

expansion piston is between 1 and 30 degrees CA past its top
dead center (TDC) position.

More preferably, combustion canbe initiated while the expansion piston is between 5 and 25
degrees CA past its top dead center
20

preferably,(TDC)

initiated
such
25

as

position.

Most

combustion can be initiated while the expansion

piston is between 10
center(TDC)

and 2 0 degrees

position.

throughwithAdditionally,

other

glow

CA pastignitionplugs,

top dead

combustion

devicesmicrowave

its

and/ormaybemethods,

ignitiondevicesor

exhaust

gases

are

through compression ignition methods.
Duringtheexhauststroke,pumped out of the expansion cylinder 14 through exhaust port
35 disposed in cylinder head 33.
exhaust valve 34,30

port 35,

An inwardly opening poppet

disposed in the inlet 31 of the exhaust

controls fluid communication between the expansion

cylinder 14 and the exhaust port 35.
and

the

exhaustpassage 22.

port

35

are

separate

The exhaust valve 34
from

the

crossoverThat is, exhaust valve 34 and the exhaust port

wo 2011/115866

PCT/US2011/028274

1235 do not make contact with,or are not disposed in,thecrossover passage 22.
With the split-cycle engine concept, the geometricengine5parameters

length,volumetriccompression

12

and

bore,

stroke,connecting

rodcompression

ratio,

etc.)

the

expansion

14cylindersofaregenerally

independent from one another.

For example, the crank throws

36,

cylinder38forcylinder 14,
10(i.e.,

thecompression

12

and

expansionrespectively, may have different radii and may

be phased apart from one another such that top dead center(TDC)

of the expansion piston 30 occurs prior to TDC of thecompression piston 20.
cycle

engine10

toThis independence enables the split-

potentiallyachievehigherefficiency

levels and greater torques than typical four-stroke engines.
15

The geometric independence of engine parameters inthe split-cycle engine 10 is also one of the main reasons
why pressure can be maintained in the crossover passage 22
as discussed earlier.
reaches

20

its

top

Specifically, the expansion piston 30

deadcenterposition

prior

to

the

compression piston reaching its top dead center position bya discreet phase angle(typically between 10 and 30

crank

angle

phase

properdegrees).

This

angle,

togetherwithtiming of the XovrC valve 24 and the XovrE valve 26, enables
the25

split-cycle

engine10

tomaintainpressurecrossover passage 22 at a high minimum pressure

in

the

(typically

20 bar absolute or higher during full load operation) during
all four strokes of its pressure/volume cycle.

That is, thesplit-cycle engine 10 is operable to time the XovrC valve 24
and the XovrE valve 26 such that the XovrC and XovrE valves30

are both open for a substantial period of time (or period of
crankshaft

rotation)

during whichtheexpansion piston

30

descends from its TDC position towards its BDC position andthecompression piston

2 0 simultaneously ascends

from

its

wo 2011/115866

PCT/US2011/028274

13

BDC position towards its TDC position.
time
26(or crankshaft rotation)

are

both

transferred
5

( 1)

a

the

from theperiod,from

expansionthat the crossover valves 24,

substantially

equal

mass

of

compression cylinder 12crossover passage 22 andto(2)cylinder

air

is

into

the

from the crossover passage 22
14.

Accordingly,

duringthisthe pressure in the crossover passage is prevented

dropping(typically
10

open,

During the period of

20,

below

a

predetermined

minimum

30,

40

bar

duringorabsolutepressure
full

load

operation).

Moreover,engine cycle(typically 80% of the entire engine cycle orgreater),during a substantial portion of thethe XovrC valve

24

and XovrE valve

26

are bothclosed to maintain the mass of trapped gas in the crossover
passage 22 at a substantially constant level.
15

As a result,the pressure in the crossover passage 22 is maintained at apredetermined minimum pressureduringallfourstrokesofmethodofhavingthethe engine's pressure/volume cycle.
For

purposesherein,the

XovrC 24 and XovrE 26 valves open while the expansion piston
20

30 is descending from TDC and the compression piston 20 isascending toward TDC in order to simultaneously transfer a
substantially

equal

mass

of

gas

into

and

out

of

the

crossover passage 22 is referred to herein as the Push-Pullmethod of gas
25

enablesthetransfer.

pressure

in

It

is

the

Push-Pull method thatthecrossoverpassage

22

of

the

split-cycle engine 10 to be maintained at typically 20 bar
or higher during all four strokes of the engine's cycle whenthe engine is operating at full load.

30

As

discussed

disposedintheseparatefromearlier,theexhaust

port

of

the

cylinderpassage

22.

The

exhaustthecrossover35

arrangement of the exhaust valve 34
the crossover passage 22,

valve

34

is

head

33

structural

not being disposed inand therefore the exhaust port 35

wo 2011/115866

PCT/US2011/028274

14

not

sharing any common portion with thecrossover passage

22,

is preferred in order to maintain the trapped mass ofgas in the crossover passage 22 during the exhaust stroke.
Accordingly,
5

large

cyclic drops

in pressure

are prevented

which may force the pressure in the crossover passage below
the predetermined minimum pressure.
XovrE valve 26 opens shortly before the expansion

10

piston30

reaches

its

time,

the

pressure

top dead center position.

ratio

of

the

pressure

At

in

this

crossoverpassage 22 to the pressure in expansion cylinder 14 is high,due to the fact that the minimum pressure in the crossover
passageistypically20

barabsoluteorhigherandthepressure in the expansion cylinder during the exhaust stroke
is typically about one to two bar absolute.
15

when XovrE valve 26 opens, the pressure in crossover passage
22

issubstantially higher than the pressure

cylinder 14
This

high

and/or20

In other words,(typically in the order of 20 to 1 or greater).
pressurefuelhigh speeds.

ratio

chargetocausesflow

initial

into

flow

expansion

the25

advantageous

it causes

split-cycle

pressures

the
14

air
at

These high flow speeds can reach the speed ofparticularly

becauseofcylindersound, which is referred to as sonic flow.
isin expansion

even

a

to

This sonic flow

split-cycle

rapid combustion event,engine10

tothoughignitionmaintainisengine10

which enables

highinitiatedcombustion
while

the

expansion piston 30 is descending from its top dead center
position.
The split-cycle air-hybrid engine 10 also includes
an air reservoir
30(tank)

40,

which is operatively connectedto the crossover passage 22 by an air reservoir (tank) valve
42.

Embodiments with two or more crossover passages 22 may

include a tank valve 42 for each crossover passage 22, whichconnect to a common air reservoir 40,

or alternatively eachwo 2011/115866

PCT/US2011/028274

15crossover passage 22 may operatively connect to separate air
reservoirs 40.
The tank valve 42 is typically disposed in an air

5reservoir(tank)

passage 22

toasecond44,whichextends

the air tank 40.

divided into a
and

port

first
air

crossover

The air tank port

air reservoir

reservoir

from(tank)(tank)

port

44

is

port section 46
section

4 8.

The

first air tank port section 46 connects the air tank valve
42 to the crossover passage 22, and the second air tank port
10

section 4 8 connects the air tank valve 42 to the air tank
40.

The

includesvolumetheofvolume

the
of

first
all

air

tank

additional

port

ports

sectionand46

recesses

which connect the tank valve 42 to the crossover passage 22
when the tank valve 42 is closed.
15

The tank valve 42 may be any suitable valve device
or system.

For example, the tank valve 42 may be an active

valve which is activated by various valve actuation devices(e.g.,

pneumatic,

Additionally,20

hydraulic,the tank valve

system with two

cam,electricorthelike).

42 may comprise a tank valve

or more valvesactuated with two

or moreactuation devices.
Air

tank

40

is

utilized to

store

energy intheform of compressed air and to later use that compressed air
to
25

power

the

crankshaft

16,

as

described

intheaforementioned United States Patent No. 7,353,786 to Scuderi
et al.

This mechanical means for storing potential energy

providesnumerousstate of the art.

potential

advantages

For instance,

over

the

current

the split-cycle engine 10

can potentially provide many advantages in fuel efficiency
30

gains

and

NOx

emissions

reductionatrelatively

lowmanufacturing and waste disposal costs in relation to othertechnologies

on

the

market,electric-hybrid systems.

such

as

dieselenginesandwo 2011/115866

PCT/US2011/028274

16

Byclosingofselectively
the

air

tank

controlling

the

valve

thereby42

andopening

and/orcontrolling

communication of the air tank 40 with the crossover passage
22,5

the split-cycle air-hybrid engine 10 is operable in an

Engine Firing

(EF)

mode,

an Air Expander

(AE)

mode,

an AirCompressor (AC) mode, an Air Expander and Firing (AEF) mode,
and a Firing and Charging (FC) mode.

The EF mode is a non-hybrid mode in which the engine operates as described above

10

without the use of the air tank 40.

The AC and FC modes areenergymode

storagemodes.

The

AC

is

an

air-hybrid

operating mode in which compressed air is stored in the air
tank

15

40

without

combustion

cylinder14(i.e.,

utilizingthekinetic

engineduring braking.

10

nooccurring

fuel

in

the

expenditure) ,energyexpansion

such

as

by
the

of

a

vehicleincluding

The

FC

mode

an

is

air-hybrid

operating mode in which excess compressed air not needed for
combustion isstored in the air tank 40,

than full engine load
at constant speed) .
20

mode

has

an

(e.g.,

such asengine idle,

at

less

vehicle cruising

The storage of compressed air in the FCenergycost(penalty);

therefore,itisdesirable to have a net gain when the compressed air is usedat alater time.

usage modes.

The AE and AEF modes are stored energy

The AE mode is an air-hybrid operating mode inwhich compressed air stored in the air tank 40 is used to25

drive the expansion piston 30 without combustion occurringin the expansion cylinder 14
The

AEF

mode

is

an

(i.e.,

air-hybrid

no

fuel

operatingexpenditure).
mode

in

which

compressed air stored in the air tank 40 is utilized in the
expansion cylinder 14 for combustion.
30

In

the

EF mode,

the

air

tank

valve

42

is

kept

closed through the entire rotation of the crankshaft 16 toisolate

the

air

tank

40

from

the

rest

of

the

engine10.

Thus, compressed air is not received in the air tank 40 nor

wo 2011/115866

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17
isstored compressed air released from the air

tank.

The

compression piston 20 and expansion piston 30 are in theirrespective

compression

and

power

modes,

in

that

the

compression piston 20 draws in and compresses inlet air for
5

use

in

the

admitted

expansion

tothecylinderexpansion

14,

and

compressed

air

is

cylinder

14

with

at

the

beginning of an expansion stroke,

which isfuel,ignited,burnedand expanded on the same expansion stroke of the expansion
piston 30,
10transmitting power to the crankshaft 16,

combustion products are discharged on the exhaust stroke.
Thetiming ofthe

XovrE valve

beginning of the expansion stroke
30

descends

efficiency
15

and thebecause,

from
of

the

dead

enginecenter)10

in22

piston wherein

is

part

is
the

combustion

of

the

takes

closing at

thethe expansion pistonsignificant
EF

when the XovrE valve 26 is open,

crossover passage
the

top

(as

26

mode.

to

the

This

is

the volume of theclearance
place.

space

Yet

above

virtually

all of the fuel is in the expansion cylinder 14, and none of
it is in the crossover passage 22.
20

is closed,

the entire combustion process is confined to the

expansion cylinder 14,
fuel

Once the XovrE valve 26

and air

and the expanding combusting mass of

can most effectively do work upon

the piston

30.
The later the XovrE valve
25

theresidual

which

is

(i.e.,

defined26 closes,

effective volumetric)

as

the

ratio

(a/b)

volume in the expansion cylinder 14

of(i.e.,

the smaller

expansion

ratio,(a)trappedthethe volume of achamber generally defined by the cylinder 14 wall,of the expansion piston 30,
30

head

and the bottom of the cylinder

33)

when

the

center to(b)the trapped volume in the expansion cylinder

14 at the time

expansion

the toppiston30

isatbottomjust when the XovrE valve 26 closes.

dead

Once

the XovrE valve 26 is closed during the expansion stroke ofwo 2011/115866

PCT/US2011/028274

18

the

expansionpresent

piston30,

inexpansion

solelythetheproduced as the mass expands.

expandingcylinderClearly,

trapped

mass

is

14

work

is

and

the later the XovrE

valve 26 closes, the farther the expansion piston 30 is from
5

top

dead

ratio

center,

and

the

thus
less

the

smaller

work

that

the

is

residual

produced

expansion

duringtheexpansion stroke.
As

shown

deterioration
10

in

in

FIG.

engine

2,

to

avoid

significant

in

the

mode,

efficiency

EF

the

residual expansion ratio should be 10.0:1 or greater.

More

preferably, the residual expansion ratio should be 15.7:1 orgreater.
a

In this exemplary embodiment,

residual

expansion

ratio

of

10:1

in order to achieve

or greater,

the

XovrE

valve should be closed at approximately 30 degrees or less
15

ATDCe, and more preferably should be closed at 22 degrees orless ATDCe.
FIGS.

3 through 14 are graphical illustrations of

exemplary valve timings and durations
closing)
20

and(time from opening toacross a range of engine speeds

engine

loads

(1

to

5

bar

( 10 0 0 to 4 0 0 0 rpm)

IMEP).

approximately 2500 rpm and 3 bar IMEP:

For
(i)

example,atthe inlet valve

18 is opened at about 36 degrees ATDCe and closed at about
102 degrees ATDCe resulting in a inlet valve open durationof about 66 degrees;
25

(ii)

the XovrC valve 24 is opened atabout -18 degrees ATDCe and closed at about 24 degrees ATDCe
resultingindegrees;

(iii)

a

XovrC

valve

the XovrE valve

open
26

duration
is

of

about

42

opened at

about

-14

degrees ATDCe and closed at about 22 degrees ATDCe resulting
in a XovrE valve open duration of about 36 degrees; and (iv)30

the exhaust valve 34 is opened at about 148 degrees ATDCe
andclosed

at

about

-13

degrees

ATDCeresultingexhaust valve open duration of about 199 degrees.

inanwo 2011/115866

PCT/US2011/028274

19

Althoughtheinventionreference to a specific embodiment,

has

been

described

byit should be understoodthat numerous changes may be made within the spirit and scope
of
5

the

inventive

concepts

described.

Accordingly,itisintended that the invention not be limited to the describedembodiment,

but that it have the full

language of the following claims.

scope defined by thewo 2011/115866

PCT/US2011/028274

20
CLAIMS

What is claimed is:
1.
5

An engine comprising:a crankshaft rotatable about a crankshaft axis;acompression

compression

cylindercrankshaft

such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocatesthrough an intake stroke and a compression stroke during a10

single rotation of the crankshaft;anexpansion

expansion

cylindercrankshaft

suchpistonandthat

slidably

operatively

theexpansion

received withinanconnected

thepistontoreciprocatesthrough an expansion stroke and an exhaust stroke during a15

single rotation of the crankshaft; andcrossoverapassageinterconnecting

compression and expansion cylinders,
includingacrossover

expansionthethe crossover passage(XovrE)

valve

disposed

therein;20

the engine being operable in an Engine Firing (EF)mode,

wherein,expansion

in

ratio

the EF mode,

at

XovrE

valve

the

engine hasclosing

of

a

10.0

residual
to

1

or

the

EF

greater.
2.
25

The

engineofclaim 1,

wherein,inmode, the residual expansion ratio at XovrE valve closing is15.7 to 1 or greater.
3.
mode,

The

engineofclaim 1,

wherein,

in

the

EF

the XovrE valve is closed at 30 degrees or less after

top dead center of the expansion piston (ATDCe) .
4.

30
mode,

The

engineofclaim 1,

wherein,

in

the

EF

the XovrE valve is closed at 22 degrees or less after

top dead center of the expansion piston (ATDCe) .

wo 2011/115866

PCT/US2011/028274

21

5.

5

The engine of claim 1, wherein the crossover

passageincludesadisposed

therein,theandcrossoverthecrossovercompression(XovrC)

valve

compression(XovrC)valve

crossover

expansion(XovrE)valve

definingapressure chamber therebetween.
6.

The engine of claim 5, including:

an

air

reservoir

passageandcrossover

operatively

selectively

connected

operable

to

to

the
store

compressed air from the compression cylinder and to deliver
10

compressed air to the expansion cylinder; andan air reservoir valve selectively controlling air
flow into and out of the air reservoir,

wherein,in the EF

wherein,inmode, the air reservoir valve is closed.
7.
15

mode,

The

engineofclaim 1,theEF

the compression piston draws in and compresses inlet

air for use in the expansion cylinder, and compressed air isadmitted

totheexpansion

cylinderbeginning of an expansion stroke,

with

fuel,

at

which is ignited,theburnedand expanded on the same expansion stroke of the expansion
20

piston,transmitting

power

to

the

crankshaft,

and

the

combustion products are discharged on the exhaust stroke.
8.

A method of operating an engine including:a crankshaft rotatable about a crankshaft axis;a25

compression

compression
crankshaft

cylinder
such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft;an30

expansion

expansion

cylindercrankshaft

such

that

pistonandtheslidably

operatively
expansion

received withinanconnected

thepistontoreciprocatesthrough an expansion stroke and an exhaust stroke during asingle rotation of the crankshaft; andwo 2011/115866

PCT/US2011/028274

22crossoverapassageinterconnecting

compression and expansion cylinders,
includingacrossover

expansionthethe crossover passage(XovrE)

valve

disposed

therein;the engine being operable in an Engine Firing (EF)

5

mode;
the method including the steps of:drawinginandcompressing

inlet

air

with

the

compression piston;10cylinderadmittingcompressed

intoexpansion

the

from

cylinder

the

fuel,

fuel

being ignited,theburnedexpansion

andexpandedthecombustion

on

the

at

the

transmitting power to the crankshaft,

and

being

discharged

residual

expansion

stroketheofproducts

same

compression

withbeginning of an expansion stroke,

expansion piston,
15

air

on

the

exhauststroke; andmaintaining

a

ratio

at

XovrE

valve closing of 10.0 to 1 or greater.
9.
20

maintaining

The method of claim 8,
theresidual

expansion

including the step of
ratio

at

XovrE

valve

closing at 15.7 to 1 or greater.
10.

The method of claim 8,

including the step ofclosing the XovrE valve at 30 degrees or less after top deadcenter of the expansion piston (ATDCe)
25

11.

The method of claim 8,

including the step ofclosing the XovrE valve at 22 degrees or less after top deadcenter of the expansion piston (ATDCe) .

30

12.

The

includesacrossovertherein,thecrossovermethodclaim

compression

crossover

expansionofcompression(XovrE)valve

8,whereintheengine(XovrC)

valve

disposed(XovrC)

valve

and

definingathepressurechamber therebetween, an air reservoir operatively connectedto the crossover passage and selectively operable to store

wo 2011/115866

PCT/US2011/028274

23

compressed air from the compression cylinder and to delivercompressedairreservoir valve

to

the

expansion

cylinder,

and

an

air

selectively controlling air

flow

into

and

out of the air reservoir; and5the method further

includes

the

step

of

keeping

the air reservoir valve closed when the engine is operated
in the EF mode.

wo 2011/115866

PCT/US2011/028274

1/14

FIG. 1

:.;;
0
N
0

FIG. 2......
......
......
......

--

Residual Expansion Ratio At XovrE Valve Closing
50
45

\

40
35
30
Residual
Expansion Ratio(-) 25
20

10

5
00

QCI

a\
a\

Exemplary Ranges For =:xpansion R atio@ XovrE Closing'\

15.7:1 @ )2 dea ATDC e
10.0:1 @ ~0 deg ATDC e-Nnrrr 1;::!1 Firinn·~-Air Ex pander+Firin g: 40.8:1@ 7 deg ATDI ~e
15.7:1 ~ 22 deqATDI ~e\-1\..)\.....Ji.

+::-.

\

~

~Air Expa nder+Firing: XovrE close :; at 7-22 deg ATDCe

\

1--

15

Ut

1\

,......-~Nor !nal Firing: X ovrE closes 3t 22-30 deg ATDCe~'"d('""')

g

~~

00
N
0

......
......

30

60

90

120
150
XovrE Closing Angle (deg ATDCe)

180

0N

QCI

N
-..l

"""

wo 2011/115866

PCT/US2011/028274

3/14

FIG. 3
Inlet Valve Opening
1 34.02 36.03 38.04 40.05 42.06 44.07 46.08 48.09 50.04--.

~ 3 l-+----l---+----+-~r--+--\-------'~~+----l---1--+-+-~-~-----l 10 52.0
Max. 50.5
Min. 34.8

a...

w
~

2
2

1
1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

4/14

FIG. 4
Inlet Valve Closing
5

1 65.02 75.03 85.04 95.05 105.0
6 115.0
7 125.0
8 135.0
9 145.0
10 155.0
11 165.0
Max. 166.0
Min. 68.7

4

--.
I....

co

3
--a...

..0w~

1 ~------~~----------~~------~~
1000
2000
4000
3000
Engine Speed (rpm)wo 2011/115866

PCT/US2011/028274

5/14

FIG. 5
Inlet Valve Duration
5

1 20.02 30.03 40.04 50.05 60.06 70.07 80.08 90.09 100.0
10 110.0
11 120.0
Max. 120.0
Min. 26.7

4

--.
I....

co

--a...

..0

3

w
~

1~--~----~--~------~-=------~

1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

6/14

FIG. 6
XovrC Valve Opening
5

1 -20.0
2 -19.0
3 -18.0
4-17.0
5 -16.0
6 -15.0
7 -14.0
8 -13.0
9 -12.0
10-11.0
11 -10.0
Max. -10.0
Min. -20.0

4

--.
I....

co

--a... 3

..0

w
~

2

1~~~~~~--~~-----=----~~~

1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

7/14

FIG. 7
XovrC Valve Closing
5

1 12.02 15.03 18.04 21.05 24.06 27.07 30.08 33.09 36.0Max. 34.3
Min. 14.4

4

--.
I....

co

--a... 3

..0

w
~

2

1
1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

8/14

FIG. 8
XovrC Duration
5

1 25.02 30.03 35.04 40.05 45.06 50.07 55.0Max. 51.3
Min. 28.4

4

--.
I....

co

--a... 3

..0

w
~

2

1
1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

9/14

FIG. 9XovrE Valve Opening
1 -14.0
2 -12.0
3 -10.0
4 -8.00
5 -6.00
6 -4.00
7 -2.00
Max. -3.00
Min. -14.00

--.
I....

co

ea... 3 r---------~-+-r--~+-~~~------~
w
~

2

1
1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

10/14

FIG. 10
XovrE Valve Closing
5

1 12.02 14.03 16.04 18.05 20.06 22.07 24.08 26.09 28.0

4

--.
I....

co

--a...

..0Max. 25.8
Min. 13.7

3w~

1 ~~------~~~~--~~--~--~~~
1000
2000
4000
3000
Engine Speed (rpm)wo 2011/115866

PCT/US2011/028274

11/14

FIG. 11
XovrE Duration

5

--.
I....

co

---

..0

~

w
~

1 18.02 20.03 22.04 24.05 26.06 28.07 30.08 32.09 34.010 36.0
3~~-------+~+-~~HH+-+-~--~~
11 38.0
Max. 37.3
Min. 19.7

1~~~--~~~~~~--~~~~~~

1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

12/14

FIG. 12
EXH Valve Opening

5

4

8

1~----~~~~--~~~~~~--~~

1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

13/14

FIG. 13
EXH Valve Closing

5

--.
I....

co

ea...

1 -20.0
2 -17.0
3 -14.0
4 -11.0
5 -8.00
6 -5.00
7 -2.00
8 1.00
9 4.00Max. 2.25
3~~--*---~~-4--~--~--~--4-~ Min. -19.0

w~

2

1~~----~~~~~----~--~~~~

1000

2000

3000

Engine Speed (rpm)4000wo 2011/115866

PCT/US2011/028274

14/14

FIG. 14
EXH Duration

5

1 170.0
2 180.0
3 190.0
4 200.05 210.0
46 220.0
7 230.08 240.0
9 250.0
Max. 240.45
1-\-----+-------\---+------\-f-----+--+---+-----+---~ Min. 175. 0~--~~--++4-~-----++-~--~~~

a...

w
~

2

1
1000

2000

3000

Engine Speed (rpm)4000

INTERNATIONAL SEARCH REPORTInternational application No.
PCT/US20111028274

A.

CLASSIFICATION OF SUBJECT MATTER

IPC(S)- F02B 33/22 (2011.01)
USPC- 123/70R
According to International Patent Classification (IPC) or to both national classification and IPC
B.

FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)
IPC(8)- F02B 33/22 (2011.01)
USPC -60/620, 712; 91/181; 123/27R, 52.3, 52.5, 53.1, 53.5, 58.8, 68, 70R, 253, 258, 286, 292; 417/237
Documentation searched other than minimum documentation to the extent that such documents are included in the fields searchedElectronic data base consulted during the international search (name of data base and, where practicable, search terms used)
PatBase, Google PatentC.

DOCUMENTS CONSIDERED TO BE RELEVANT

Category•X

Citation ofdocurnent, with indication, where appropriate, of the relevant passages
US 2009/0272368 A1 (BRANYON et al) 05 November 2009 (05.11.2009) entire document-yRelevant to claim No.
1-5,7-11

----·
6, 12

y

US 2007/0157894 A1 (SCUDERI et al) 12 July 2007 (12.07.2007) entire document

6, 12

A

US 2006/0124085 A1 (LUTIGEHARM) 15 June 2006 (15.06.2006) entire document

1-12

A

US 4,696,158 A (DEFRANCISCO) 29 September 1987 (29.09.1987) entire document

1-12

A

US 1,350,570 A (SARJENT) 24 August 1920 (24.08.1920) entire document

1-12

D

D

Further documents are listed in the continuation of Box C.

•

Special categories of cited documents:"A" document defining the general state of the art which is not considered
to be of particular relevance"E" earlier application or patent but published on or after the international
filing date"L" document which may throw doubts on priority claim(s) or which iscited to establish the ))Ublication date of another citation or otherspecial reason (as spec1fied)"0" document referring to an oral disclosure, use, exhibition or othermeans"P" document published prior to the international filing date but later thanthe priority date claimed"T'

Date of the actual completion of the international search

Date of mailing of the international search report

02 May 2011
Name and mailing address of the ISAlUS
Mail Stop PCT, Attn: ISAlUS, Commissioner for Patents
P.O. Box 1450, Alexandria, Virginia 22313-1450
Facsimile No. 571-273-3201
Form PCTIISA/21 0 (second sheet) (July 2009)

later document published after the international filing date o1eriority
date and not in conflict with the ap~lication but cited to un erstandthe principle or theory underlying t e invention"X" document of particular relevance; the claimed invention cannot be

considered novel or cannot be considered to involve an inventive
step when the document is taken alone"Y" document of particular relevance; the claimed invention cannot be

considered to involve an inventive step when the document iscombined with one or more other such documents, such combination
being obvious to a person skilled in the art"&" document member of the same patent family

1 2 MAY 2011
Authorized officer:
Blaine R. Copenheaver
PCT Helpdesk: 571·272-4300
PCT OSP: 571-272-7n4