(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/02829l(22) International Filing Date:(25) Filing Language:

14 March 2011 0 4 ·03 ·2011 )EnglishEnglish(26) Publication Language:(30) Priority Data:
61/313,831
15 March 2010 (15.03.2010)61/363,825
13 July2010 (13.07.2010)18 July2010 (18.07.2010)61/365,343
61/404,239 29 September 2010 (29.09.2010)

us
us
us
us

(71) Applicant (for all designated States except US): SCUDERI GROUP, LLC [US/US]; llll Elm Street, Suite 33,
West Springfield, MA 01089 (US).

---;;;;;;;;;;;;;;;--;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;WO 2011/115877 A1BADAIN, 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). PHILLIPS, Ford; 9303 Strong Box Way, San Antonio, TX 78254 (US).
(74) Agents: FILDES, Christopher, J. et al.; Fildes & Outland, P.C., 20916 Mack Avenue, Suite 2, Grosse Pointe
Woods, MI 48236 (US).
(81) Designated States (unless otherwise indicated, for every
kind of national protection available): AE, AG, AL, AM,
AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ,
CA, CH, CL, CN, CO, CR, CU, CZ, DE, DK, DM, DO,
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,
KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD,
ME, MG, MK, MN, MW, MX, MY, MZ, NA, NG, NI,
NO, NZ, OM, PE, PG, PH, PL, PT, RO, RS, RU, SC, SD,
SE, SG, SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR,
TT, TZ, VA, UG, US, UZ, VC, VN, ZA, ZM, ZW.

(72) Inventors: MELDOLESI, Riccardo; 55 New Road,
Shoreham-by-Sea, West Sussex BN43 6RB (GB).

[Continued on next page](54) Title: SPLIT -CYCLE ENGINE HAVING A CROSSOVER EXPANSION VALVE FOR LOAD CONTROL

FIG. 1(57) Abstract: An engine includes a crankshaft rotatable about a crankshaft
axis. A compression piston is slidably received within a compression cylinderand operatively connected to the 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 at least one of an Engine Firing (EF) mode, an Firing andCharging (FC) mode, and an Air Expander and Firing (AEF) mode of the engine, the timing of the XovrE valve closing is variable to control engine load,
and the engine has a residual expansion ratio at XovrE valve closing of 14 to I
or greater.

W 0 2011/11587 7 A 1 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN, GQ,(84) Designated States (unless otherwise indicated, for every
GW, ML, MR, NE, SN, TD, TG).
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, 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,wo 2011/115877

PCT/US2011/028291

1

SPLIT-CYCLE ENGINE HAVING A CROSSOVER EXPANSION VALVE FOR
LOAD CONTROLTECHNICAL FIELD

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

expansion

to

valve

such

for

an

engineload

havingcontrolacrossoverandoptionallyincorporating 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

compression
cylinder
such

that

pistonslidablyreceived

withinandoperatively

connected

tothecompression

pistonathe

reciprocateswo 2011/115877

PCT/US2011/028291

2

through an intake stroke and a compression stroke during asingle rotation of the crankshaft;anwithin5

expansionan expansion(power)cylinderpistonslidablyreceived

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

compression and expansion cylinders,
10

including

at

least

a

crossoverinterconnecting

thethe crossover passage

expansion(XovrE)

valve

disposed therein, but more preferably including a crossovercompression(XovrC)valve and a crossover expansion(XovrE)valve defining a pressure chamber therebetween.
United States
15

8,

Patent No.

6,543,225 granted April

2003 to Scuderi and United States

granted October 11,

Patent No.

2005 to Branyon et al.,are incorporated herein by reference,
discussion
addition,
20ofsplit-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.
Split-cycle
cycle

enginewithanair-hybrid
airengines

reservoir

combineand variousasplit-

controls.

This combination enables a split-cycle air-hybrid engine to
25

store

energyreservoir.

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:30

a crankshaft rotatable about a crankshaft axis;acompression
crankshaft

compression
cylinder
such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocateswo 2011/115877

PCT/US2011/028291

3

through an intake stroke and a compression stroke during asingle rotation of the crankshaft;anwithin5

expansionan expansion(power)cylinderpistonslidablyreceived

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

compression and expansion cylinders,
10

including

at

least

a

crossoverinterconnecting

thethe crossover passage

expansion(XovrE)

valve

disposed therein, but more preferably including a crossovercompression(XovrC)valve and a crossover expansion(XovrE)valve defining a pressure chamber therebetween; andan15crossoverairreservoir

passageandoperatively

selectively

connected

operable

to

to

the
store

compressed air from the compression cylinder and to delivercompressed 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 be
25

normal operating or firing
theEnginemodes.

Firing(EF)

In the EF mode,

mode)

30

reservoir.

connecting

the

mode
and

in a

(also commonly called
four

basic

air-hybrid

the engine functions as a non-air

hybrid split-cycle engine,
air

(NF)

run

operating without the use of its

In the EF mode,crossoverpassageatank valve operatively
to

the

air

reservoir

remains closed to isolate the air reservoir from the basic
split-cycle engine.

wo 2011/115877

PCT/US2011/028291

4

The

split-cycle

air-hybrid

engineoperates

the use of its air reservoir in four hybrid modes.

withThe fourhybrid modes are:
1)

Air

5

Expandercompressed

(AE)

air

mode,

energy

which

from

includes

the

air

using

reservoir

without combustion;
2)

Air Compressor(AC)compressedenergyairmode,which includes

into

the

air

storing

reservoir

without combustion;
10

3)

Air Expander and Firing (AEF) mode, which includes
using compressed air energy from the air reservoir
with combustion; and4)Firingandstoring
15

Charging

compressed

(FC)
air

mode,

which

includesenergy

into

the

air

AE,

AC,

reservoir with combustion.
However,further

AEF and FC,

optimization ofthese modes,EF,

is desirable to enhance efficiency and reduce

emissions.

20

SUMMARY OF THE INVENTION

The

present

invention

providesasplit-cycle

engine in which the use of at least one of the Engine Firing
(EF)
25

mode,

the Firing and Charging

Expander and Firing

(AEF)

(FC)

mode,

and the Air

mode is optimized for potentiallyany vehicle in any drive cycle for improved efficiency.
More particularly,

an exemplary embodiment of anengine in accordance with the present invention includes acrankshaft rotatable about a crankshaft axis.
30

pistonisslidably received within

and operatively connected tothea

A compression

compression

crankshaft

cylindersuch thatthecompression piston reciprocates through an intake stroke andacompression

strokeduringasinglerotationofthewo 2011/115877

PCT/US2011/028291

5

crankshaft.
anAn expansion piston is slidably received within

expansion

crankshaft

cylinder

such

that

and

operatively

theexpansionconnected

pistontothereciprocatesthrough an expansion stroke and an exhaust stroke during a5singlerotationofthecrankshaft.

A crossover

passageinterconnects the compression and expansion cylinders.
crossovervalve

passagedisposed

includestherein.

acrossoverThetimingexpansionoftheclosing is variable to control engine load,
10

The(XovrE)

XovrE

valve

and the engine

has a residual expansion ratio at XovrE valve closing of 14
to 1 or greater.
A method of operating an engine is also disclosed.
The

engineincludescrankshaft axis.
15

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.
slidably

20

received

operatively
expansion
andanwithinconnected

pistonexhaustcrankshaft.

toanexpansionthecrankshaft

reciprocatesstrokeA

An expansion piston isduringcrossoverthrougha

includesatherein.

expansionTheinmethodthattheexpansion

strokesinglerotationoftheinterconnects

thepassagecrossover

such

and

an

compression and expansion cylinders.
25cylinderThe crossover passage(XovrE)

accordance

valve

with

invention includes the following steps:

disposedthepresent

controlling engine

load by varying the timing of the XovrE valve closing;maintaining30

aresidual

expansion

ratio

at

XovrE

and

valve

closing of 14 to 1 or greater.
These

and

other

invention will be morefeaturesandadvantages

fully understood from the

of

the

followingwo 2011/115877

PCT/US2011/028291

6
detailed description of the invention taken together with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS5

In the drawings:
FIG.

1 is a lateral sectional view of an exemplary

split-cycle air-hybrid engine in accordance with the present
invention;
10

FIG. 2 is a graphical illustration of closing angle(timing) of a crossover expansion (XovrE) valve in accordancewith the present invention as a function of engine speed atvarious engine loads;
FIG.

15

3 is a graphical illustration of a preferred

exemplary range of residual expansion ratio(i.e.,

effective

volumetric expansion ratio) versus closing angle of the XovrE
valve in accordance with the present invention;
FIG.

4 is a graphicalillustration of compression

cylinder, expansion cylinder, and crossover passage volume as
20

a function of crank angle of the expansion piston;
FIG.

5

is

a

graphical

crossover passage pressurefortimingXovrEversusavariableaillustration

fixed XovrE
valveclosingcomparingvalve

closingtimingasafunction of engine speed and engine load; and
25

FIG.

6

is

a

graphical

illustration

of

fuel

consumption improvement for an optimized XovrE valve closing
timing versus a fixed XovrE valve closing timing over a range
of engine speeds and engine loads.

30

DETAILED DESCRIPTION OF THE INVENTION

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

wo 2011/115877

PCT/US2011/028291

7
In General
Unless otherwise specified,closing timings

are measured inall valve opening andcrank angle

degrees

after

top dead center of the expansion piston (ATDCe) .
5

Unlessotherwise

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.
10

15

Bar: Unit of pressure, 1 bar = 10 5 N/m 2
BMEP:

Brake

referstotheoutputas

outputshaft),

after

frictionfor.

Brake Mean Effective Pressure

effective

pressure.

deliveredThe

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

is the engine's

brake torque output expressed in terms of a mean effective
pressure
divided(MEP)
byparameter

20

mean

value.

BMEP

isenginedisplacement.

taken

after

the

equal

to

This
lossesthebraketorqueistheperformance

due

to

friction.

Accordingly,

BMEP=IMEP-friction.

Friction,in this case isusually also

expressed

of

value

known

its

associated

in

terms

Frictional Mean Effective Pressure
Compressor:

The

compression

an MEP

as(or FMEP)

cylinderandcompression piston of a split-cycle engine.
Effective TDC:
25

the

total

The timing,

combined

volumein crank angle degrees,ofthecompression

at whichcylinder,expansion cylinder, and crossover passage is at a minimum.
Exhaust(or EXH) valve: Valve controlling outlet of gas fromthe expander cylinder.
Expander:30

The

expansion

cylinderandexpansion piston of a split-cycle engine.
FMEP: Frictional Mean Effective Pressure.

its

associatedwo 2011/115877

PCT/US2011/028291

8

IMEP:

Indica ted

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.

Inlet: Inlet valve.
5

Inlet

valve:

Valve

controllingintake

of

gas

into

the

compressor cylinder.
Pumping work (or pumping loss): For purposes herein, pumping
work (often expressed as negative IMEP)

relates to that partof engine power which is expended on the
10

fuel

and air

chargeinto

the engine

induction of theand theexpulsion of

combustion gases.
Push-Pullmethod:compression(XovrE)
15

The(XovrC)

method

valve

of

and

openingthethecrossovercrossover

expansion

valve while the expansion piston is descending from

TDC and the compression piston isascending toward TDC inorder to simultaneously transfer a substantially equal massof gas into and out of the crossover passage.
RPM: Revolutions Per Minute.
Sonic flow
20

(velocity): Air flow in which the velocity of the

air reaches the speed of sound.
Sonic flow period: A duration during which air flow into the
expansion cylinder is at sonic velocity.
Sonic flow ratio: The ratio of the pressure in the crossover
passage to the pressure in the expansion cylinder necessary

25

to achieve

sonic flow.

For air,

the

sonic

flow

ratio

is

1.894.
T

junction:

Junction

in

Xovr

port

for

connecting

to

air

connecting

the

Xovr

passage

with

the

tank.
Tank
30

valve:

Valve

compressed air storage tank.
Valve duration:

The interval in crank degrees between startof valve opening and end of valve closing.

wo 2011/115877

PCT/US2011/028291

9

VVA:

Variable

operable

to

valve

alter

actuation.

A

shape

timingtheormechanism
of

a

or

methodvalve's

lift

profile.
Xovr
5

(or

Xover)

valve,

passage

or

port:

The

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

cylindersthrough

which

gas

flows

from

compression to expansion cylinder.
XovrC(or XoverC)

valves:Valves at

the compressor end of

the Xovr passage.
10

XovrE

(or XoverE) valves: Valves at the expander end of thecrossover (Xovr) passage.
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 cylinders
15

of

a

conventional

enginewithacombination

of

one

compression cylinder 12 and one expansion cylinder 14.

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

14 to cover andseal the cylinders.
20

The

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,

perform the intake(or inlet)

and compression strokes,

and the expansion cylinder 14, together with its associated25

expansion piston 30,
exhaust strokes.

perform the expansion(or power)

and

The Otto cycle is therefore completed inthese two cylinders 12, 14 once per crankshaft 16 revolution(360 degrees CA) about crankshaft axis 17.
During the intake stroke, intake (or inlet) air is
30

drawn

into

port

19

the

compression

disposedinthecylindercylinder12headthrough
33.

An

an

intakeinwardly

opening(opening inwardly into the cylinder and toward thepiston)poppetintake(orinlet)

valve

18

controls

fluid

wo 2011/115877

PCT/US2011/028291

10communication between the intake port 19 and the compression
cylinder 12.
During5piston20

chargeintothecompression

pressurizes
the

the

air

stroke,chargecrossover passage

the

and

compression

drives(or port)

typically disposed in the cylinder head 33.

22,

the

air

which

is

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

gas

to

the

crossoverpassage22,

which acts as the intake passage for the expansion cylinder
10

14.

In some embodiments,

two or more crossover passages 22

interconnect the compression cylinder 12 and the expansion
cylinder 14.
The geometric (or volumetric) compression ratio of

15

the

compression cylinder

12

of

for

split-cycleingeneral)referred toengine.

asenginesthesplit-cycle engine"compression ratio"

The geometric(or volumetric)isherein

of

the

20

(and

commonly

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" or "geometric expansion ratio"of the split-cycle engine.

The geometric compression ratioof a cylinder is well known in the art as the ratio of the25

enclosed(or trapped)

recesses)whenbottom deadavolume in the cylinder

pistoncenter(BDC)(including allreciprocating

thereinposition

the

to

is

enclosedatits

volume(i.e., clearance volume)in the cylinder when said piston is

at

(TDC)

its

top

dead

centerposition.

Specifically for

split-cycle engines as defined herein, the compression ratioof a compression cylinder is determined when the XovrC valve30

isclosed.

Also

specificallyfor

split-cycle

enginesasdefined herein, the expansion ratio of an expansion cylinder
is determined when the XovrE valve is closed.

wo 2011/115877

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11

Due to very high compression ratios
1,

5

30

1,

40

to

greater)withinthecylinder12,anoutwardly opening(opening

outwardly awaythecylinder)

valve

24

at

the

flow

from

control

20 to 1,poppetcrossovercrossovercrossover passage(e.g.,

or

20 to

to

from

1,

(e.g.,

the22.

passagecompression
Due

30 to 1,

to40

compression

compression
inlet(XovrC)

25

is

used

to

cylinder

12

into

the

very high expansion

to 1,

or greater)

ratioswithin the

expansion cylinder 14, an outwardly opening poppet crossover
10

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,

15

the

crossover

26 are timed to maintainpressureinpassage

22

at

a

high

minimumpressure(typically 20 bar or higher at full

load)

duringall four strokes of the Otto cycle.
Atleast 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
20

occursdead

shortly before expansion piston 30
centerposition.

The

air/fuel

reacheschargeits

topenterstheexpansion cylinder 14 when expansion piston 30 is close to
its

25

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
plug

tip

39.

Combustion

can

be

initiated

while

the

expansion piston is between 1 and 30 degrees CA past its top
30

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
preferably,(TDC)

position.

Most

combustion can be initiated while the expansion

wo 2011/115877

PCT/US2011/028291

12

piston is between 10
center(TDC)

initiated
such
5

as

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,
10port 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.
35 do
15

port

35

are

The exhaust valve 34

separate

from

the

crossoverThat is, exhaust valve 34 and the exhaust port

not makecontact with,or are not disposed in,thecrossover passage 22.
With the split-cycle engine concept, the geometricengineparameters

length,volumetriccompression
20(i.e.,

12

and

bore,

stroke,connecting

rodcompression

ratio,

etc.)

the

expansion

14cylindersofaregenerally

independent from one another.

For example, the crank throws

36,

cylinder38forcylinder 14,

thecompression

12

and

expansionrespectively, may have different radii and may

be phased apart from one another such that top dead center
(TDC)
25

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.
The geometric independence of engine parameters inthe split-cycle engine 10 is also one of the main reasons30

why pressure can be maintained in the crossover passage 22
as discussed earlier.
reaches

its

topSpecifically, the expansion piston 30

deadcenterposition

prior

to

the

compression piston reaching its top dead center position bywo 2011/115877

PCT/US2011/028291

13

a 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
the5

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 valves10

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

BDC position towards its TDC position.
15

time
26

(or crankshaft rotation)

are

both

transferred

open,
( 1)

a

crossover passage 22 and
to
20

the

period,from

expansion

equal

mass

of

cylinder

air

is

into

the

from the crossover passage 22
14.

Accordingly,

duringthisthe pressure in the crossover passage is prevented

dropping(typically25

During the period ofcompression cylinder 12
(2)

its

that the crossover valves 24,

substantiallyfrom the

from

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.

As a result,the pressure in the crossover passage 22 is maintained at apredetermined minimum pressure
30

duringallfourstrokesofmethodofhavingthethe engine's pressure/volume cycle.
For

purposesherein,the

XovrC 24 and XovrE 26 valves open while the expansion piston
30 is descending from TDC and the compression piston 20 iswo 2011/115877

PCT/US2011/028291

14

ascending 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
5enablesthetransfer.

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.

10

As

discussed

disposedintheseparatefromearlier,theexhaust

port

of

the

cylinderpassage

22.

The

exhaustthecrossover35

arrangement of the exhaust valve 34
the crossover passage 22,

15

valve

34

is

head

33

structural

not being disposed inand therefore the exhaust port 35

notsharing 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,

large

cyclic drops

in pressure

are prevented

which may force the pressure in the crossover passage below
the predetermined minimum pressure.
20

XovrE valve 26 opens shortly before the expansion
piston30

reaches

its

time,

the

pressure

top dead center position.

ratio

of

the

pressure

in

At

this

crossoverpassage 22 to the pressure in expansion cylinder 14 is high,due to the fact that the minimum pressure in the crossover
25

passageistypically20

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

In other words,

when XovrE valve 26 opens, the pressure in crossover passage
22
30

is

substantially higher than the pressure

cylinder 14
This

high

and/orin expansion(typically in the order of 20 to 1 or greater).
pressurefuelhigh speeds.

chargeratio
tocausesflow

intoinitialflow

expansionofthecylinder

14

air
at

These high flow speeds can reach the speed ofwo 2011/115877

PCT/US2011/028291

15

sound, which is referred to as sonic flow.
isparticularly

becausethe5advantageous

it causes

split-cycle

pressures

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
10(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 eachcrossover passage 22 may operatively connect to separate air
15

reservoirs 4 0.
The tank valve 42 is typically disposed in an air
reservoir(tank)

passage 22

to

and

a

second44,

which

the air tank 40.

divided into a
20

port

first
air

extends

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
section 4 8 connects the air tank valve 42 to the air tank
40.
25

The

includesvolumeofthe volumes

the

first

of all

air

tank

port

additional ports

section46

and recesses

which connect the tank valve 42 to the crossover passage 22
when the tank valve 42 is closed.
The tank valve 42 may be any suitable valve device
or system.
30

For example, the tank valve 42 may be an active

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

pneumatic,

Additionally,

hydraulic,the tank valve

cam,electricorthelike).

42 may comprise a tank valve

wo 2011/115877

PCT/US2011/028291

16

system with two

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
5

to

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

providesnumerous

potential

state of the art.
10

advantages

For instance,

over

the

current

the split-cycle engine 10

can potentially provide many advantages in fuel efficiency
gains

and

NOx

emissions

reductionatrelatively

lowmanufacturing and waste disposal costs in relation to othertechnologies

on

the

market,such

asdieselengines

andelectric-hybrid systems.
15

Byclosingofselectively
the

air

tank

controlling

the

valve

thereby42

andopening

and/orcontrolling

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

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

Engine Firing
20

(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

25

without the use of the air tank 40.

The AC and FC modes areenergymode

modes.

The

AC

is

an

air-hybrid

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

30

storage40

without

combustion

cylinder14(i.e.,

utilizingthekinetic

engineduring braking.

10

nooccurringfuelenergyintheexpenditure) ,expansion

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) .

(e.g.,

engine idle,

such asatlessvehicle cruising

The storage of compressed air in the FC

wo 2011/115877

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17

mode

has

an

energycost(penalty) ;therefore,itisdesirable to have a net gain when the compressed air is usedat alater time.

usage modes.
5

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 todrive 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 the10

expansion cylinder 14 for combustion.
In the EF mode, the compression piston 20 draws inand compresses inlet air for use in the expansion cylinder
14.

The compressed air from the compression cylinder 12 isadmitted
15

to

the

expansion

cylinderbeginning of an expansion stroke,

14

with

fuel,

at

which is ignited,theburnedand expanded on the same expansion stroke of the expansion
piston 30,

transmitting power to the crankshaft 16, and the

combustion products

aredischarged ontheexhauststroke.

Since compressed air is neither stored in nor released from20

the air tank 40

in the EF mode,

the air tank valve 42

isclosed.
In the FC mode, the compression piston 20 draws inand compresses inlet air for use in the expansion cylinder
14 during a single rotation of the crankshaft 16.
25

thecompressed

admitted

to

the

air

from

the

expansion

compression

cylinderbeginning of an expansion stroke,

14

Some ofcylinder

with

fuel,

which is ignited,

12

is

at

the

burnedand expanded on the same expansion stroke of the expansion
piston,30transmitting

combustion products

power
are

to

the

discharged on

crankshaft,theexhaustandthestroke.

The air tank 40 is also charged with compressed air during
the same single rotation of the crankshaft 16 by selectively
opening and then closing the air tank valve 42.

wo 2011/115877

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18
In the AEF mode,

compressed air stored in the airtank 40 is admitted to the expansion cylinder 14 with fuel,at the beginning of an expansion stroke, by keeping the airtank valve 42 open for at least a portion of the crankshaft
5

rotation.
expandedThe

air/fuel

the

same

on

piston 30,

mixtureisexpansion

ignited,strokeoftheburnedandexpansiontransmitting power to the crankshaft 16,

and thecombustion products are discharged on the exhaust stroke.
In the AE mode,
10

tank

40

is

admitted tocompressed air stored in the air

theexpansion

beginning of an expansion stroke.

cylinder

14,

at

the

Since in this mode the

air tank valve 42 is kept open for at least a portion of the
crankshaft rotation, air flow into the expansion cylinder 14

15

is controlled by the XovrE valve 26.

The air is expanded ontheexpansion

same

expansion

strokeofthetransmitting power to the crankshaft 16,

and thepiston30,(expanded)

air is discharged on the exhaust stroke.
The XovrE valve
valve
20

capable26 may beof variable valveavariably actuatable

actuation

the opening and/ or closing timings(VVA)such that(in crank angle degrees)of the XovrE valve may be varied from one engine cycle to25

another.

In at least one of the EF mode,

AE mode,and the AEF mode,

closingisvariedtoexpressed as

torquein units

units of Bar)the FC mode,thecontrol

the FC mode,thetiming of the XovrE valve
engineof NM or as

load(typically

IMEP or BMEP in

That is, during at least one of the EF mode,
the AE mode,and the AEF mode,

the XovrE valve

closing timing is varied from at least a first cycle of theengine's 10 operation to a second cycle of the engine's 1030

operation to provide a first mass of air required to produce
a first torque at the first cycle and a second mass of air
required to produce a second torque at the second cycle.

wo 2011/115877

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19

Moreover, the XovrE valve 26 closing timing may bevaried to meter into, and trap in, the expansion cylinder 14
the necessary mass of air to produce a required amount of
torque for any cycle of engine 10 operation during any of5

the EF,FC,

AEand AEF modesof operation.

The

required

torque can be produced by combining the metered air with therequired amount of fuel to be ignited, burned,
during a combustion event as in the EF,
Alternatively,
10

therequired

torqueFC,canand expanded

and AEF modes.

beproducedbymetering just air into the expansion cylinder to be expanded
during the AE mode.

As shown by example in FIGS. 2 and 3,

in the EF and AEF modes the XovrE valve 26 should preferably
be closed at least 30 degrees or less ATDCe, more preferablyshould be closed at approximately 27 degrees or less ATDCe,
15

and even more preferably should be closed at approximately
22 degrees or less ATDCe as it meters air into the expansion
cylinder to control load.

However, the ranges shown in FIG.

2 are only one exemplary embodiment specific to the EF mode,and other embodiments and other engine modes may have other20

ranges of XovrE valve 26 closing.
FIG.

Also, the ranges shown in

2 are dependent upon engine load.

engineload of

2 bar

IMEP,

the

XovrE

For example,
valve

at an

2 6 should beclosed at approximately 25 degrees or less ATDCe, whereas at
an engine load of 3 bar IMEP,
25

the XovrE valve 26 should beclosed at approximately 22 degrees or less ATDCe.
Further, as shown by example within the EF and AEF
ranges depicted in FIG. 3,

the engine 10 in accordance withtheapresent

inventionhas

residual

expansion

ratio

at

XovrE valve 26 closing of approximately 10 to 1 or greater
30

during a majority of its operating range,
residual

expansion

greater,more preferably has a residual expansion ratio of

15.7

1 or greater,

to

ratio

of

preferably has aapproximately

14

and most preferably has

to

a

1

or

residual

wo 2011/115877

PCT/US2011/028291

20
expansion ratio of approximately 20
earlier(ATDCe)to 1 or greater.

that the XovrE valve 26 closes,The

the greater

the residual expansion ratio, which is defined as the ratio(a/b) of (a) the trapped volume in the expansion cylinder 14
5(i.e.,

thevolumeofcylinder 14 wall,thebottomofdefined bythethe top of the expansion piston 30,

and

the

a

chambercylindergenerally

head

33)

piston 30 is at bottom dead center to

when

the

expansion(b) the trapped volume

in the expansion cylinder 14 at the time just when the XovrE
10valve 2 6 closes.
the15

expansionOnce the XovrE valve 2 6 is closed during
strokeoftheexpansion

pistonexpanding trapped massis present

cylinder14isClearly,

the earlier the XovrE valve 2 6 closes,

the

and

work

expansion piston

30

to

the

solely in the expansion

produced

is

30,

as

top

the

dead

mass

expands.

the closer

center,thus

thegreater the residual expansion ratio and the more work thatis produced during the expansion stroke.
Ahighresidual

expansion

ratio

results

when

engine load is controlled with the XovrE valve 2 6 because20

thechargesonic

airenteringthevelocity

duringmost

conditions.
into

the

Due

to

expansion

expansionofthecylinder12engineisatoperatingthe high velocity of the air

flowingcylinder2 6 must

12,

the

XovrE

valve

close quickly after top dead center of the expansion piston
25

30

in

order

cylinder

14

to
the

meter

into,

and

necessary masstrap

of airtorque during a given operating cycle.
the earlier(i.e.,

quicker)theto produce

expansionagiven

As discussed above,

the XovrE valve 2 6 closes,

higher the residual expansion ratio,
30

in,which,

thein the case of

the present invention is typically 10 to 1 or greater,andpreferably 14 to 1 or greater.
Sonic velocity of the air entering the expansion
cylinder 14 when the XovrE valve 26 is initially opened iswo 2011/115877

PCT/US2011/028291

21

achievedbymaintaining

thepressure

inthecrossoverpassage 22 at more than 1.894 the pressure in the expansion
cylinder during the exhaustpressure
5

engine,

ratio
a

for

high

air).

strokeInpressure

in(i.e.,

above

thethe EF and FC modes
thecrossoversonicof thepassage22

ismaintained by utilizing the Push-Pull method of gas transfer
described above.

In the AEF mode as well as the AE mode,ahigh pressure in the crossover passage 22 is maintained bykeeping
10

the

air

tank

40

pressure

at

or

above

5

bar,

preferably above 7 bar, and more preferably above 10 bar.
Further,air

travellingin order to maintain the pressure of thethroughthecrossoverpassage

22

from

the

compression cylinder 12 to the expansion cylinder 14 at ahigh pressure,15

the volume of the crossover passage must be

small compared to the total volume of the compression andexpansion

cylinders

12,

14("totalcylinder volume")

the respective compression and expansion pistons 20,
at bottom dead center(BDC) .

when

30 are

The total cylinder volume issignificant because in the Push-Pull method, both the XovrC
20

valve 24 and XovrE valve 26 are open when a mass of air istransferred through thevolumeof bothcylinder

14

the

are

crossover passage 22.

compression

cylindersimultaneouslyin12Hence,
andcommunication

expansionwithcrossover passage 22 during the Push-Pull method.
25

in

FIG.

4,

in

an

exemplary embodiment

of

the

the

expansion

piston30)

isgreaterthe

As shown

split-cycle

engine 10, the maximum expansion cylinder 14 volume
of

the

than

510

(at BDC
cubic

centimeters (cc), the maximum compression cylinder 12 volume(at BDC of the compression piston 20)
30

cc,

the

less
(i.e.,

total

than
the

70

crossover passage
cc,

and

expansion

theis greater than 570

22volumeismaximum

totalcylindercylinder14volumecompression cylinder 12 volume at BDC)

atconstant

BDC

atvolumeplus

theis greater than 1080

wo 2011/115877

PCT/US2011/028291

22
cc.

Therefore,

in order to maintain a high pressure in the

crossover passage 22, the total cylinder volume should be at
least

8

times

passage 22,
5greaterthan

preferably atvolumeofthecrossover

least

15

times

greaterthevolumeofthecrossoverleast 10 times greater than thepassage,

than

and

the

more

volumepreferably

of

the

4,

in

at

crossoverpassage.
Additionally,

10

order

to

maintain a high pressure in the crossover passage 22,

themaximum

deadcompression

as

shown

cylinder

in

12

FIG.

volumecenter of the compression piston 20)(atbottomshould be at least 2

times greater than the volume of the crossover passage 22,
preferably at least 4 times greater than the volume of thecrossover passage, more preferably at least 6 times greater
15

than

the

volumeofthecrossoverpassage,

and

most

preferably at least 8 times greater than the volume of thecrossover passage.

Further,

in

order

pressure in the crossover passage 22,20

to maintain

a

high

the maximum expansion

cylinder 14 volume(at bottom dead center of the expansion

pistonbe

30)

should

at

least

2

times

volume of the crossover passage 22,

greaterthan

preferably attheleast 4times greater than the volume of the crossover passage,

andmore preferably at least 6 times greater than the volume of
the crossover passage.
25

Also,
crossoverin order to maintain a high pressure in thepassagecompression

22,

the

minimum

totalcylinder12,

expansion

crossover passage 22 at "effective" TDC
in crank angle degrees,
30

of

the

compression

crossover passage

iscylinder(i.e.,

of

the

14,

and

the timing,

at which the total combined volume

cylinder,atvolumeexpansiona minimum)

cylinder,should be

less

and

than

4

times the total volume of the crossover passage, preferably
less than 3 times the volume of the crossover passage,andwo 2011/115877

PCT/US2011/028291

23

more

preferably

crossover

less

than

2

times

the

volumeForinstance,inthepassage.

embodiment of FIG.

4,

the

exemplarythe crossover passage has a constanttotal volume of approximately 62
5ofcc and the minimum total

volume at "effective" TDC (which in this case occurs at 10.8
degrees ATDCe)is approximately 100 cc.

The minimum total

volume at "effective" TDC is close to the fixed volume of
the crossover passage 22 because at actual top dead centerof the compression and expansion pistons 20, 30, the volumes
10of the compression and expansion cylinders 12,
small.
theIn other words,

the geometric compression ratio ofcompression cylinder 12geometric expansion ratio
approximately
15

50:1,

14 are veryisapproximately 95:1

and theof the expansion cylinder 14

meaning

that

there

is

a

small,

istightclearance between the compression and expansion pistons 20,
30 and the cylinder head 33
the head)at the pistons'(specifically,20,

the fire deck of

30 respective top dead center

positions.
Varying the timing of the XovrE valve 26 closing
20

to control engine load results in a higher crossover passage
22 pressure in comparison to operating with avalve closing timing.
EF

mode,

crossover
25

at

any

passage

As shown by example in FIG. 5, in the

given

engineload

thepressure

in

the

22

higher

when

VVA

is

for

the

is

XovrE valve 26 rather than aarrangement.

fixed XovrE

For example,

used

fixed valve timing actuation

at an engine speed of 2500rpm

and an engine load of 2 bar IMEP,

the crossover passage 22

pressurewhenisapproximately

6 bar

the

XovrE

valve

26

closing angle (timing) is fixed, whereas it is approximately
30

13 bar when the XovrE valve closing angle is variable.
The

increaseincrossoverpassage22

pressure

results in an increase in the sonic flow period of the mass
of

air

that

enterstheexpansion

cylinder14,

thereby

wo 2011/115877

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24

increasing the efficiency of theengineexample in FIG.

approximately a 1 to 10%

6,in the EF mode,

10.

As

shown bygain in fuel efficiency is achieved when the XovrE valve 26
closing timing is variable and optimized as compared to when5

the XovrE valve 26 closing timing is fixed.
Althoughtheinventionreference to a specific embodiment,

has

been

described

byit should be understoodthat numerous changes may be made within the spirit and scope
of
10

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 2011/115877

PCT/US2011/028291

25

CLAIMS

What is claimed is:
1.
5

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

compression

cylindercrankshaft

such

that

pistonslidablyreceived

withinandoperatively

connected

tothecompression

pistonathe

reciprocatesthrough an intake stroke and a compression stroke during a10

single rotation of the crankshaft;anexpansion

expansion

cylindercrankshaft

suchpistonandthat

slidablyreceived

withinanoperatively

connected

to

the

the

expansion

pistonreciprocatesthrough an expansion stroke and an exhaust stroke during a15

single rotation of the crankshaft; andcrossoverapassageinterconnecting

compression and expansion cylinders,
includingacrossover

expansion

the

the

crossover passage(XovrE)

valve

disposed

therein;20

wherein the timing of the XovrE valve closing isvariabletocontrolengine

load,

and

the

enginehasaresidual expansion ratio at XovrE valve closing of 14 to 1
or greater.
2.
25

expansion

The engine of claim 1,

ratio

at

XovrE

valve

wherein the residualclosing

is

20

to

1

or

wherein

the

XovrE

or less

after

greater.
3.
valve

is

The

closed atengineofclaim

approximately 27

1,degrees

top dead center of the expansion piston (ATDCe) .
30

4.

The

engineofclaim

valve is an outwardly opening valve.

1,

wherein

the

XovrE

wo 2011/115877

PCT/US2011/028291

26

valve

is

5.

The

a

variably

valve actuation
6.
5

engineofclaim

actuatable1,

whereinvalve

capable

the
of

XovrE

variable

(VVA)
The

combined volume

engineof the

of

claim

1,

wherein

the

total

compression and expansion cylinders

is at least 8 times greater than the volume of the crossover
passage.
7.
volume
10

of

The

the

engineofcompression

claim

1,

whereincylinder

is

at

the

least

total

2

times

the

total

greater than the volume of the crossover passage.
8.

The

engine

of

claim

1,

whereinvolume of the expansion cylinder is at least 2 times greaterthan the volume of the crossover passage.

15

total

9.

The

enginevolumeofthecylinder,

of

claim

wherein1,

compression

thecylinder,minimum

expansionand crossover passage at effective top dead centeris less than 4 times the volume of the crossover passage.

20

10.

The engine of claim 1, wherein:thecrossovercompression(XovrC)

compression(XovrC)valve

passageincludesacrossoverdisposed

therein,thecrossovercrossover

expansion

valve

and

the

(XovrE) valve defining a pressure chamber therebetween;
an airreservoirisoperatively connected tothecrossover passage via an air reservoir port and selectively
25

operable

to

store

compressed

air

from

cylinderandtodelivercompressed

air

air

reservoir

thetocompression

theexpansion

cylinder; and
an

valve

selectively

controls

airflow into and out of the air reservoir.
11.

30

The engine of claim 10, wherein the engine isoperable in an Engine Firing

(EF)

mode,

mode,

valve

is

the

air

reservoir

wherein,kept

in the EF

closed,thecompression piston draws in and compresses inlet air for use

wo 2011/115877

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27

in the expansion cylinder, and compressed air is admitted totheexpansion

cylinder withexpansion stroke,
the
5

same

fuel,

which is ignited,

expansion

strokepower

thetransmitting

at

to

of

the beginning ofanburned and expanded ontheexpansion

crankshaft,

and

the

piston,combustion

products are discharged on the exhaust stroke.
12.

The engine of claim 10, wherein the engine isoperable in a Firing and Charging
mode,
10

the

air

reservoir

valve

is

mode,

and in the FC

selectively

openedandclosed, the compression piston draws in and compresses inlet
air

for

use

in

the

expansionrotation of the crankshaft,

15

(FC)

cylinderduringasingleand compressed air is admitted

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

expansion stroke,burned and expanded on

the

same

which is ignited,

expansion

strokepower

thetransmitting

to

of

the

expansion

crankshaft,

and

the

products are discharged on the exhaust stroke,
reservoirischarged withcompressedairpiston,combustion
and the air

duringthesamesingle rotation of the crankshaft.
20

13.

The engine of claim 10, wherein the engine isoperable in an Air Expander and Firing
the

AEF

mode,

the

air

compressed air

from

the

cylinderwith

expansion
25

expansion stroke,
the

same

reservoir
air

power

the

transmittingatwhich is ignited,stroketovalvereservoir

fuel,expansion

(AEF)

of

and in

kept

open,

is

is

the

mode,

admitted to
beginning

the

of

an

burned and expanded ontheexpansion

crankshaft,

and

the

piston,combustion

products are discharged on the exhaust stroke.
14.
30

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

compression
cylinder
such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocateswo 2011/115877

PCT/US2011/028291

28through an intake stroke and a compression stroke during asingle rotation of the crankshaft;an5

expansion

expansion

cylindercrankshaft

suchpistonandthat

slidablyreceived

withinanoperatively

connected

to

the

the

expansion

pistonreciprocatesthrough an expansion stroke and an exhaust stroke during asingle rotation of the crankshaft; andcrossoverapassageinterconnecting

compression and expansion cylinders,
10

includingacrossover

expansion

the

the

crossover passage(XovrE)

valve

disposedload by varying thetiming oftherein;the method including the steps of:controlling engine
the XovrE valve closing; and15

maintainingaresidual

expansion

ratio

at

XovrE

valve closing of 14 to 1 or greater.
15.
maintaining

The method of claim 14, including the step oftheresidual

expansion

ratio

at

XovrE

valve

closing at 20 to 1 or greater.
20

16.

The method of claim 14, including the step ofclosing the XovrE valve at approximately 27 degrees or lessafter top dead center of the expansion piston (ATDCe) .
17.
includes a
25

the

The

methodofclaimcrossover compression

crossoverpassage,the14,(XovrC)

crossovervalve and the crossover expansion
pressure chamber therebetween,

whereinthevalve disposed incompression(XovrE)

engine(XovrC)valve defining aan air reservoir operatively

connected to the crossover passage via an air reservoir port
and selectively operable
30

compression

cylinderexpansion cylinder,toand tostore

compressed air

deliver

fromcompressed air

and an air reservoir valve

to

the
the

selectively

controlling air flow into and out of the air reservoir.

wo 2011/115877

PCT/US2011/028291

29The method of claim 17,

18.

including the

steps

of:
operatingtheengineinanEngineFiring(EF)mode;
keeping the air reservoir valve closed;

5

drawinginandcompressing

inlet

air

with

the

compression piston; andcylinder10admittingcompressed

intoexpansion

beginning of
burned

and

the
an

expansion

expanded

expansion piston,the

combustion

on

air

cylinderstroke,thefromcompression

with

fuel,

fuel

being

the

ignited,thetransmitting power to the crankshaft,

and

being

expansion

atofproducts

same

the

the

discharged

strokeontheexhauststroke.

15

19.

The method of claim 17,

including the

steps

of:
operating the engine in a Firing and Charging (FC)mode;drawing
20

compressioninpistonandcompressing

duringa

inletsingle

air

with

the

rotationofthecrankshaft;admittingcylinder with fuel,
the
25

fuel

being

compressed

air

into

the

expansionat the beginning of an expansion stroke,

ignited,burnedandexpanded

on

the

same

expansion stroke of the expansion piston, transmitting power
to thecrankshaft,and discharging the combustion productson the exhaust stroke; andchargingtheairreservoir

withcompressed

airduring the said single rotation of the crankshaft.
30

20.

The method of claim 17,

including the

steps

of:
operating the engine in an Air Expander and Firing(AEF) mode; andwo 2011/115877

PCT/US2011/028291

30
admitting

air

from

the

air

reservoir

into the expansion cylinder with fuel,at the beginning ofan expansion stroke,burned and expandedon5

compressed

the

same

which is ignited,

expansiontransmitting powertostroke

the

of

the

crankshaft,expansion

piston,and discharging

thecombustion products on the exhaust stroke.
21.

An engine comprising:a crankshaft rotatable about a crankshaft axis;
a10

compression

compression
crankshaft

cylinder
such

that

pistonslidablyreceived

withinandoperatively

connected

tothecompression

pistonathe

reciprocatesthrough an intake stroke and a compression stroke during asingle rotation of the crankshaft;an15

expansion

expansion

cylindercrankshaft

suchpistonandthat

slidablyreceived

withinanoperatively

connected

to

the

the

expansion

pistonreciprocatesthrough an expansion stroke and an exhaust stroke during asingle rotation of the crankshaft; anda20crossoverpassageinterconnecting

compression and expansion cylinders,theincludinga(XovrC)

crossover

expansion

crossovercompression(XovrE)

valve

the

crossover passage
valve

and

a

pressuredefiningachamber therebetween;
wherein the timing of the XovrE valve closing is
25

variable to control engine load,

the total combined volumeofcylindersthecompression

and expansion

is

at

least

times greater than the volume of the crossover passage,
theminimum

total

expansion cylinder,
30

volumeofthecompression

8andcylinder,and crossover passage at effective top

dead center is less than 4 times the volume of the crossover
passage.

wo 2011/115877

PCT/US2011/028291

31

22.

The engine of claim 21 comprising:the XovrE valve closing timing being operable to
vary

from

a

first

cycle

of

the

engine's

operation

second cycle of the engine's operation to provide a
5

to

a

first

mass of air required to produce a first torque at the firstcycle and a second mass of air required to produce a second
torque at the second cycle.

10

23.

The engine of claim 22, wherein:thecrossovercompression(XovrC)

valve

compression(XovrC)passageincludesacrossoverdisposed

therein,thecrossovercrossover

expansion

valve

and

the

(XovrE) valve defining a pressure chamber therebetween;
an air reservoir is operatively connected to thecrossover passage via an air reservoir port and selectively
15

operable

to

store

compressed

air

from

cylinderandtodelivercompressed

air

an

air

reservoir

thetocompression

theexpansion

cylinder;valve

selectively controls

airflow into and out of the air reservoir;
20

theenginebeing

operable

in

any

one

of

an

EF

variedtomode, an FC mode, an AE mode, and an AEF mode; andthemeter into,

XovrE

valve

and trap in,closingtimingbeing

the expansion cylinder a mass of

air to produce a required amount of torque for a cycle of25

engine operation during at least one of the EF,

FC, AE,andAEF modes.
2 4.

The

engine

of

claim

2 3,

whereinvalve closing timing is varied to meter into,

the

XovrE

and trap in,

the expansion cylinder a mass of air to produce a required
30

amount of torque for a cycle of engine operation during eachof the EF, FC, AE, and AEF modes.

wo 2011/115877

PCT/US2011/028291

32

25.
volume

of

the

The

enginecompression

of

claim

22,

whereincylinder

is

at

least

the

total

2

times

the

total

greater than the volume of the crossover passage.
2 6.
5

The

engine

of

claim

22,

whereinvolume of the expansion cylinder is at least 2 times greaterthan the volume of the crossover passage.

wo 2011/115877

PCT/US2011/028291

1/5

FIG. 1

FIG. 2

27.5

XoverE Closing:.;;-c3 25.0 -------- -------- -------- --------- --------- --------0

~

22.5

---g' 20.00IMEP
- - - 1 bar-WA---2bar-WA- - - - 3 bar-WA------- Fixed TimingN0......
......
......
......

-Ut

QCI

-..l
-..l

-

·u;
0

(_) 17.5w~ 15.0I....

0>< 12.5

1000

-i'.)

1500

2000

2500

3000

3500

4000

01

Engine Speed (rpm)FIG. 5 Xover Pressure....!....

25

co

..._

..0

--- 20~

IMEP------- - - 1 bar-FIX..............

:::J

~ 15
~
a...
t::
0

--- - --

10

-

a...

-

I....

~

0

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

---- - - 1 bar-VVA- - - 2 bar-FIX- - - 2 bar-VVA- - - - 3 bar-FIX- - - - 3 bar-VVA'"d('""')g00
N0......
......

5

0N

QCI

N
1.0

>< 0

......

1000

1500

2000

2500

3000

Engine Speed (rpm)

3500

4000

:.;;
0
N
0

FIG. 3......
......
......
......

--

Residual Expansion Ratio At XovrE Valve Closing
50
45

I\\

30
Residual
Expansion Ratio(-) 25
20

5
00

15.7:1 @ ~2 dea ATDC e
10.0:1 @ BO deg ATDC e-Nnrrr ;:!I Firinn·~

1\-Air Ex )ander+Firin p: 40.8:1@ 7 degATD :;e15.7:1 ~ 22 deq ATD :;e

\

-c..v

\

01

\ --

--Air Expa nder+Firing: XovrE close Pat 7-22 de~ ATDCe

2ch\ -

15
10

QCI

-..l
-..l

Exemplary ~anges For ~xpansion R ~tio@ XovrE Closing

40
35

Ut

14:1

\

~Nor nal Firing: XpvrE closes ~t 22-30 deg ATDCe~

I~ ............._
30'"d('""')

g

-

60

00
N
0

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

120
150
XovrE Closing Angle (deg ATDCe)

90

180

0N

QCI

N
1.0

......

:.;;
0

FIG. 4N0......
......
......
......

-Ut

Cylinder, crossover port & combined volumes0..........

........ ......... ......... ... 7 ~~:": ....

100,.-/ · ' ~/ //·/ ~ 1.'

200

/ ,

300
....-

("')

E

400

~ 500
(])

E 600
:::J

~ 700
I....

(])

"'0

--

/ ,
/___ ., , /

1100

.
/

1200.
-180

-150

I

I,/

•

•'

/

___ . ,.

I

~/

•

•
/

v

I

•

-••••••• I-·-90.......

~~,......... .......... ......... ..........

,"'~'. .,..
' ' \ .... ~~
'..

..

"
.

..
r- IVIIIII IIUIII LU
volu 11e at 1~I.8
deg

••

~

-120

I

I

II.U

~·

800

-~ 900>(_) 1000-~·. i"'.

~

QCI

-..l
-..l

~~.\~A<:,~ lnr.

\

\ ..
\

.......

01. ~Power Cylinde r
Grosso ver Por s
1otal t-' orts & \ vYIS.

-60 -300
30
60
Crank Angle (deg ATDC-e)

-~

\ ..

' ..

vUIIIIJI t:::S::SUI \. [YIIIIUt::l

'

,_

..

' .. ..,

90

..

~

120 150

.. ..
180

'"d

("")

g
00
N
0

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

0N

QCI

N
1.0

......

:.;;

FIG.6

0

Engine Firing Mode: Fixed vs Optimized WA Timings

5

.;J

•

J

<

•

<

•

7

N
0
7

•

•

I

I

4

IMEP (bar)
3•

2• \

\

•

\

~

\.

•

J

.,

J

I

•

/.

"'

"'

•

\

\

•

L.......

• 1

1

r........a•......
......
......
......

--•"'=::!;;;:

o/o Gain
1 0.002 1.00
3 2.0043.00
5 4.006
5.00
I
7 6.00
8 7.00
9 8.0010 9.00
1110.00
Max: 11.67• Min: 2.01

Ut

QCI

-..:;
-..:;

U1
..............

U1

•

'"d

("")

g
00
N
0

,.

1000

•

I

1500

•

2000

I

I

I.

-...........

2500
Engine Speed (rpm)

•

3000

£

•

3500

l

l

>

>.

4000

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

0N

QCI

N
1.0

......

INTERNATIONAL SEARCH REPORTInternational application No.
PCT/US2011/028291

A.

CLASSIFICATION OF SUBJECT MATTER

IPC(8)- F028 33/22 (2011.01)
USPC- 123/70R
According to International Patent Classification (I PC) or to both national classifi~ation and IPC

B.

FIELDS SEARCHED

Minimum documentation searched (classification system followed by classification symbols)
IPC(8)- F02B 33/20,33/22,41/06 (2011.01)
USPC- 123/70R, 70V
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)
PatBaseC.

DOCUMENTS CONSIDERED TO BE RELEVANT

Category*X

Citation of document, with indication, where appropriate, ofthe relevant passages
US 2007/0157894 A1 (SCUDERI et al) 12 July 2007 (12.07.2007) entire document-yUS 1,062,999 A (WEBB) 27 May 1913 (27.05.1913) entire document

"E"
"L"

"0"
"P"

Special categories of cited documents:
document defining the general state of the art which is not considered
to be of particular relevanceearlier application or patent but published on or after the international
filing datedocument which may throw doubts on priority claim(s) or which iscited to establish the publication date of another citation or otherspecial reason (as specified)
document referring to an oral disclosure, use, exhibition or othermeans
document published prior to the international filing date but later thanthe priority date claimed

Date of the actual completion of the international search
04 May 2011
Name and mailing address of the JSA/US
Mail Stop PCT, Attn: ISAIUS, Commissioner for Patents
P.O. Box 1450, Alexandria, Virginia 22313-1450
Facsimile No. 571-273-3201
Form PCTIJSN21 0 (second sheet) (July 2009)

4

D

D Further documents are listed in the continuation of Box C.
"A"

1-3, 5-26------------

4

y

•

Relevant to claim No.

"T''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

Date of mailing of the international search report

1 3 MAY 2011
Authorized officer:
Blaine R. Copenheaver
PCT Helpdesk: 571-272-4300
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