(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/028288(22) International Filing Date:
14 March 2011 (14.03.2011)

WO 2011/115875 A1
Sea, West Sussex BN43 6WL (GB). GILBERT, Ian; 67
Beach Green, Shoreham-By-Sea, West Sussex BN43 5YE(GB).
(74) Agents: FILDES, Christopher, J. et al.; Fildes & Outland, P.C., 20916 Mack Avenue,suite 2, Grosse Pointe
Woods, MI 48236 (US).

(71) Applicant (for all designated States except US): SCUDERI GROUP, LLC [US/US]; llll Elm Street, Suite 33,
West Springfield, MA 01089 (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).
BADAIN, Nicholas; 37 Rosslyn Road, Shoreham-By-(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,(25) Filing Language:

English(26) Publication Language:

English(30) Priority Data:
61/313,831
61/363,825
61/365,343

15 March 2010 (15.03.2010)13 July2010 (13.07.2010)18 July2010 (18.07.2010)

us
us
us

[Continued on next page]--(54) Title: SPLIT -CYCLE AIR-HYBRID ENGINE HAVING A THRESHOLD MINIMUM TANK PRESSURE

FIG. 1--;;;;;;;;;;;;;;;--;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

12(57) Abstract: A split-cycle air-hybrid engine includes a rotatable crankshaft.
A compression piston is slidably received within a compression cylinder andoperatively 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 compression (XovrC)
valve and a crossover expansion (XovrE) valve defming a pressure chamber
therebetween. An air reservoir is operatively connected to the crossover passage. An air reservoir valve selectively controls air flow into and out of the air
reservoir. The engine is operable in an Air Expander and Firing (AEF) mode.
In the AEF mode, the pressure in the air reservoir is greater than or equal toapproximately 5 bar absolute, preferably greater than or equal to approximately 7 bar absolute, and more preferably greater than or equal to approximately
I 0 bar absolute.

W 0 2011/11587 5 A1 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, Published:
TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, with international search report (Art. 21 (3))
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).

wo 2011/115875

PCT/US2011/028288

1

SPLIT-CYCLE AIR-HYBRID ENGINE HAVING A THRESHOLD MINIMUMTANK PRESSURETECHNICAL FIELD

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

tosuch an engine incorporating an air-hybrid system.

BACKGROUND OF THE INVENTION

For
10engine"aspurposes

used

in

of

the

clarity,present

theterm"conventional

applicationreferstoaninternal combustion engine wherein all four strokes of thewell-known

Otto

cycle

compression,

expansion(i.e.,

the(or power)

intake(orinlet) ,and exhaust strokes)

arecontained in each piston/cylinder combination of the engine.
15

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.
Also,
20

for

purposesofclarity,thefollowing

definition is offered for 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

split-cycle

engineasreferredtohereincomprises:25

a crankshaft rotatable about a crankshaft axis;acompression
crankshaft

compression
cylinder
such

that

pistonslidablyreceived

withinandoperatively

connected

tothecompression

pistonathe

reciprocatesthrough an intake stroke and a compression stroke during a30

single rotation of the crankshaft;wo 2011/115875

PCT/US2011/028288

2anwithinexpansionan 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 2011/115875

PCT/US2011/028288

3anwithinexpansionan 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 2011/115875

PCT/US2011/028288

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 present invention provides a split-cycle air20

hybridengineFiring

(AEF)

in

which

the

use

of

the

Air

Expanderandmode is optimized for potentially any vehicle

in any drive cycle for improved efficiency.
Moreparticularly,

anexemplaryembodimentofasplit-cycle air-hybrid engine in accordance with the present
25

invention includes a crankshaft rotatable about a crankshaft
axis.

A compression piston iscompression
crankshaft

cylinder
such

that

slidably received within aandoperatively

thecompression

connected
pistontothereciprocatesthrough an intake stroke and a compression stroke during a30

single rotation of the crankshaft.
slidablyreceived

operatively
expansion

withinconnected

pistonto

An expansion piston isanexpansionthecrankshaft

reciprocatesthroughancylinder
such

that

expansionandthestrokewo 2011/115875

PCT/US2011/028288

5

and

an

exhaustcrankshaft.

5

strokeAduringcrossoverasinglepassagerotationoftheinterconnects

thecompression and expansion cylinders.

The crossover passage

includes(XovrC)acrossovercompression

crossover

expansion(XovrE)

chamber

therebetween.

An

valve
air

valve

and

a

pressuredefining

reservoirisaoperatively

connected to the crossover passage and selectively operable
to store compressed air from the compression cylinder and todeliver
10compressed air

theexpansion

cylinder.

An

airreservoir valve selectively controls

air flow into and outofengineisoperable

in

an

Air

mode.

In

the

mode,

the

the

air

reservoir.

ExpanderandFiringpressure

in theapproximately
15

to

The
(AEF)

AEF

air reservoir

is greater than or equal

to

bar

preferablyor5

absolute,equal to approximately 7 bar absolute,

greaterthan

and more preferably

greater than or equal to approximately 10 bar absolute.
Amethodofoperatingengine is also disclosed.

asplit-cycle

air-hybrid

The split-cycle air-hybrid engine

includes a crankshaft rotatable about a crankshaft axis.
20

A

compression piston is slidably received within a compression
cylinder

and

that

compression piston reciprocatestheoperatively

connected

tothecrankshaft

through ansuchintakestroke and a compression stroke during a single rotation ofthe25

crankshaft.

withintheanAnexpansion

crankshaft

expansion piston
cylindersuch thatandisslidably received

operatively

connected

tothe expansion piston reciprocatesthrough an expansion stroke and an exhaust stroke during asinglerotationofthecrankshaft.

Acrossoverpassageinterconnects the compression and expansion cylinders.
30

crossover passage
valve

and

pressureacrossoverchamber

operatively

includesacrossover

expansion

therebetween.

connected

tothecompression(XovrE)
An

valve
air

crossoverThe(XovrC)

definingareservoirispassageandwo 2011/115875

PCT/US2011/028288

6
selectively

operablecompression

cylinder and to

expansiontocylinder.

store

An

compresseddeliver

air

air

from

compressed air

reservoir

valve

the

to

selectively

controls air flow into and out of the air reservoir.
5

the

The

engine is operable in an Air Expander and Firing (AEF) mode.
The method in accordance with the present invention includes
the10

following

steps:

openingtheadmittingcompressed

air

from

the

expansion

cylinder

with

fuel,

at

expansion

stroke,theexpanded

on

the

same

piston,transmitting

fuel

air
air

reservoir

the

being

stroke

power

the

of

valve;

into

beginning

ignited,expansiontoreservoir

the

of

an

burnedandtheexpansion

crankshaft,

and

the

combustion products being discharged on the exhaust stroke,
whereby15

themaintaining

engineaisoperatedpressure

in

in

the

AEF

mode;

the

air

reservoir

featuresandadvantages

and
above

approximately 5 bar absolute.
These
invention will

and

other

be morefully understood from the

of

the

followingdetailed description of the invention taken together with the20

accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings:
25

FIG.

1 is a lateral sectional view of an exemplary

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

DETAILED DESCRIPTION OF THE INVENTION
30
The following glossary of acronyms and definitionsof terms used herein is provided for reference.

wo 2011/115875

PCT/US2011/028288

7

In General
Unless otherwise specified,closing timings

all valve opening andare measured in crank angle degrees

after

top dead center of the expansion piston (ATDCe) .
Unless5otherwise

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

Bar: Unit of pressure, 1 bar

10 5 N/m 2

Compressor:

cylinderThe

compression

and

its

associatedits

associatedcompression piston of a split-cycle engine.
Expander:The

expansion

cylinderandexpansion piston of a split-cycle engine.
15

Tank

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.
Xovr
20

(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.
25

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
30

of

a

conventional

enginewithacombinationofcompression cylinder 12 and one expansion cylinder 14.

oneAcylinder head 33 is typically disposed over an open end of

wo 2011/115875

PCT/US2011/028288

8the expansion and compression cylinders 12,

14 to cover andseal the cylinders.
The

four

strokes

of

the

Otto

cycle

are

"split"over the two cylinders 12 and 14 such that the compression
5cylinder 12, together with its associated compression piston
20,

perform the intake(or inlet)

and the expansion cylinder 14,
expansion piston 30,
exhaust strokes.
10and compression strokes,

together with its associatedperform 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

15

drawn

into

port

19

the

compression

disposedinthecylindercylinder12through

head

33.

an

An

intakeinwardly

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

valve

18

controls

fluidcommunication between the intake port 19 and the compression
cylinder 12.
During20

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 asource25ofhigh-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.
The geometric (or volumetric) compression ratio of30

thecompression cylinder 12of split-cycle engine

10

for

split-cycle

general)commonlyreferred toengine.

asenginesthein"compression ratio"

The geometric(or volumetric)ishereinof the(andsplit-cycle

compression ratio ofwo 2011/115875

PCT/US2011/028288

9the expansion cylinder 14 of split-cycle engine 10
split-cycle engines in general)(and foris herein commonly referred

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

The

geometric compression ratio of a cylinder is well known in5

the art as the ratio of the enclosed (or trapped) volume inthecylinderreciprocating

10(including
therein

is

all
at

recesses)

its

when

bottom deadapistoncenter(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 when15

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

20

1,

40

to

greater)withinthecylinder12,anoutwardly opening(opening

outwardly away

from

the

cylinder)

valve

24

at

the

flow

from

controlcrossover passage(e.g.,

20 to 1,

or

20 to

to

30

1,

(e.g.,

poppetcrossovercrossoverthe22.

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
25

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,

30

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

wo 2011/115875

PCT/US2011/028288

10

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
5

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
10

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
15

preferably,(TDC)

initiated
such
20

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,
25

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.
35 do
30

port

35

are

separate

The exhaust valve 34
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 geometricenginelength,parametersvolumetric(i.e.,

bore,

stroke,connecting

rodcompression

ratio,

etc.)

the

of

wo 2011/115875

PCT/US2011/028288

11

compression

12

expansion

14cylindersaregenerally

independent from one another.

For example, the crank throws

36,

cylinder38forcylinder 14,
5

and

the

compression

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.
10

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

15

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
the20

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 valves25

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.
30

time
26

(or crankshaft rotation)

are

both

transferred

open,
( 1)

a

crossover passage 22 andDuring the period of

equal

mass

of

compression cylinder 12
(2)

its

that the crossover valves 24,

substantiallyfrom the

from

air

is

into

the

from the crossover passage 22

wo 2011/115875

PCT/US2011/028288

12

to

the

period,from

expansion

14.

Accordingly,

duringthisthe pressure in the crossover passage is prevented

dropping(typically5cylinder

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.
10

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
15

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
20

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.

25

As

discussed

disposedintheseparatefromearlier,theexhaust

port

of

the

cylinderpassage

22.

The

exhaustthecrossover35

arrangement of the exhaust valve 34
the crossover passage 22,

30

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

wo 2011/115875

PCT/US2011/028288

13which may force the pressure in the crossover passage below
the predetermined minimum pressure.
XovrE valve 26 opens shortly before the expansion

5

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 stroke10

is typically about one to two bar absolute.

In other words,

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

issubstantially higher than the pressure

cylinder 14
This
15

high

and/or(typically in the order of 20 to 1 or greater).
pressure

fuel

ratio

chargehigh speeds.

tocausesflow

initial

into

flow

expansion

20

theadvantageous

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
25

an air reservoir(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,
30

or alternatively eachcrossover passage 22 may operatively connect to separate air
reservoirs 40.
The tank valve 42 is typically disposed in an air
reservoir(tank)

port

44,

which

extends

fromcrossoverwo 2011/115875

PCT/US2011/028288

14

passage 22

tothe air tank 40.

divided into aandasecondfirst
air

The air tank port

air reservoir

reservoir(tank)(tank)

port

44

is

port section 46
section

4 8.

The

first air tank port section 46 connects the air tank valve
5

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.

The

includesvolumetheofvolume

the
of

first
all

air

tank

additional

port

ports

sectionand46

recesses

which connect the tank valve 42 to the crossover passage 22
10when the tank valve 42 is closed.
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.,
15

pneumatic,

Additionally,

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
20

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.
25

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.
30

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wo 2011/115875

PCT/US2011/028288

15

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
5

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

10

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
15

at constant speed) .
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.
20

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 the25

expansion cylinder 14 for combustion.
In
preferably

the

kept

crankshaft 16

AEF

mode,

the

air

open

throughtheentire(i.e.,

tank

valve

42

is

rotationofthethe air tank valve 42 is kept open atleast during the entire expansion stroke and exhaust stroke30of the expansion piston) .

Thus, compressed air stored in the

air

from

tank

40

is

released

the

air

tank

40

into

the

crossover passage 22 to provide charge air for the expansion
cylinder 14.

Also, the XovrC valve 24 is kept closed throughwo 2011/115875

PCT/US2011/028288

16

the entire rotation of the crankshaft 16,
the compression cylinder 12,
expansion

pistoncompressed air
5

expansion

30

expansion stroke,
the

same

which may be deactivated.

operatesin(from the air

cylinder

14

with

its

fuel,

strokepower

tank 40)atwhich is ignited,

expansion

thereby isolating

of

is
the

mode,

The

in

that

admitted tothebeginning

anofburned and expanded ontheexpansiontransmitting power to the crankshaft 16,

piston30,

and the combustion

products are discharged on the exhaust stroke.
10

In order to enhance engine efficiency and control,
during the AEF mode the pressure in the air tank 40 should
not bereduced below

should

not

be

5 bar

reducedabsolute,

below

7

and more preferablybarabsolute,

and

most

preferably should not be reduced below 10 bar absolute.
15

Inother words, in the AEF mode the pressure in the air tank 40
should be at least 5 bar absolute or greater.

In the AEF

mode, the air tank valve 42 is opened to allow communicationofcompressed air

passage 22.
20

from

the

air

tank

40

to

the

crossover

The XovrE valve 26 controls the engine load bycontrolling theflow of compressed air from thepassage 22 to the expansion cylinder 14.

crossoverAs the pressure in

the air tank 40 decreases,

the flow rate of compressed air

simultaneously(duedecreases

to

the

drop

in

pressuredifferential between air tank 40 and the expansion cylinder
25

14).

If the air tank pressure and hence the air flow rate

become too low,
of

air

into

during one
cycle)
30

tothethe XovrE valve 26 cannot control the flow
expansion

cylinderrevolution of the

14.

crankshaft

In

other

(i.e.,

words,

one engine

at a low air flowrate the XovrE valve 26 would haveremain

open

for

too

long

necessary mass of charge airofaduration(for combustion)

to

allow

the

to enter the

expansion cylinder 14 in the required amount of time.

wo 2011/115875

PCT/US2011/028288

17

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 2011/115875

PCT/US2011/028288

18
CLAIMS

What is claimed is:
1.
5

A split-cycle air-hybrid 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;a20

crossoverpassageinterconnecting

compression and expansion cylinders,theincludinga(XovrC)

crossover

expansion

crossovercompression(XovrE)

valve

the

crossover passage
valve

and

a

pressuredefiningachamber therebetween;ancrossoverairreservoir

passageandoperatively

selectively

connected

operable

to

to

the
store

compressed air from the compression cylinder and to delivercompressed air to the expansion cylinder; and25

an air reservoir valve selectively controlling air
flow into and out of the air reservoir;
the engine being operable in an Air Expander andFiring (AEF) mode, wherein,in the AEF mode:the pressure in the air reservoir is greater than30

or equal to approximately 5 bar absolute.
2.
wherein,

The split-cycle air-hybrid engine of claim 1,

in the AEF mode,the pressure in the air reservoir

is greater than or equal to approximately 7 bar absolute.

wo 2011/115875

PCT/US2011/028288

19

3.
wherein,

The split-cycle air-hybrid engine of claim 1,

in the AEF mode,the pressure in the air reservoir

is greater than or equal to approximately 10 bar absolute.
4.
5

The split-cycle air-hybrid engine of claim 1,

wherein, in the AEF mode, the air reservoir valve is open.
5.
wherein,

The split-cycle air-hybrid engine of claim 1,

in the AEF mode,

the air reservoir valve is open

during the entire expansion stroke and exhaust stroke of the
expansion piston.
10

6.
wherein,

The split-cycle air-hybrid engine of claim 1,

in

the

AEF

mode,

compressed

air

from

the

air

reservoir is admitted to the expansion cylinder with fuel,at the beginning of an expansion stroke,burned15

andexpanded

expansion piston,the

combustion

on

the

of

the

transmitting power to the crankshaft,andproducts

samewhich is ignited,areexpansiondischarged

strokeontheexhauststroke.
7.

Amethodofoperatingasplit-cycle

air-hybrid engine including:20

a crankshaft rotatable about a crankshaft axis;acompression

compression
crankshaft

cylinder
such

that

pistonslidablyandoperatively

thecompression

received withinconnected

pistontoathe

reciprocatesthrough an intake stroke and a compression stroke during a25

single rotation of the crankshaft;anexpansion

expansion

cylindercrankshaft

suchpistonandthat

slidably

operatively

theexpansion

received withinanconnected

thepistontoreciprocatesthrough an expansion stroke and an exhaust stroke during a30

single rotation of the crankshaft;acrossoverpassageinterconnecting

thecompression and expansion cylinders,the crossover passage

including(XovrC)acrossovercompression

valve

and

a

wo 2011/115875

PCT/US2011/028288

20crossover

expansion(XovrE)valve

definingapressurechamber therebetween;ancrossover5

airreservoir

passageandoperatively

selectively

connected

operable

to

to

the
store

compressed air from the compression cylinder and to delivercompressed air to the expansion cylinder; andan air reservoir valve selectively controlling air
flow into and out of the air reservoir;
the engine being operable in an Air Expander and

10

Firing (AEF) mode;the method including the steps of:
opening the air reservoir valve;
admitting15

compressed

air

from

the

air

reservoir

into the expansion cylinder with fuel,at the beginning ofanignited,expansion

stroke,thetheexpansion

strokepower

theexpandedonsame

piston,transmitting

fuel

to

being

of

burnedtheandexpansion

crankshaft,

and

the

combustion products being discharged on the exhaust stroke,
whereby the engine is operated in the AEF mode; and20

maintaining a pressure in the air reservoir above
approximately 5 bar absolute.
8.
maintaining

The method of claim 7,
thepressure

intheincluding the step of
airreservoir

above

approximately 7 bar absolute.
25

9.
maintaining

The method of claim 7,
thepressure

intheincluding the step of
airreservoir

above

approximately 10 bar absolute.
10.
keeping
30

open

The method of claim 7,
the

air

reservoir

including the step ofvalve

duringtheentireexpansion stroke and exhaust stroke of the expansion piston.

wo 2011/115875

PCT/US2011/028288

1/1

FIG. 1SUBSTITUTE SHEET (RULE 26)

INTERNATIONAL SEARCH REPORTInternational application No.
PCT/US2011/028288

A.

CLASSIFICATION OF SUBJECT MA TIER

IPC(B)- 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(S)- F02B 21/00, 33/20, 33/22, 41/06 (2011.01)
USPC- 91/170R; 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}
Pat Basec.

DOCUMENTS CONSIDERED TO BE RELEVANT

Category*

Citation of document, with indication, where appropriate, of the relevant passages

Relevant to claim No.

y

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

1-10.

y

US 2007/0101712 A1 (NEGREet al) 10 May 2007 (10.05.2007) entire document

1-10

0

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

"A"
"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 searchlater document published after the international filing date o&riority
date and not in conflict with the aphlication 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"T'"&" document member of the same patent family

Date of oa~ngM~~ntef~~'al search report

02 May 2011
Name and mailing address of the !SAlUS
Mail Stop PCT, Attn: ISAIUS, Commissioner for Patents
P.O. Box 1450, Alexandria, Virginia 22313-1450
Facsimile No. 571-273-3201
Form PCT/ISA/210 (second sheet) (July 2009)

Authorized officer:
Blaine R. Copenheaver
PCT Helpdesk: 571·272-4300
PCT OSP: 571·272·7774