CGR (Combustion Gas Recycling)

plantcalicobeansUrban and Civil

Nov 29, 2013 (3 years and 4 months ago)

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CGR (Combustion Gas Recycling)

New Technology

Summary


1

The
diesel
emission problem

today

At partial engine load or low rpm
, during diesel combustion, O
2

of the excess air oxidizes N
2

to NO
X

(generic for NO & NO
2
).
Diesel fuel self
-
ignites at
~
210 C
°

and

burns on ~210
0 C
°
. NO
X

start
s

to form at
~
1540 C
°. The formation rate
depends on pressure and
rises exponentially with the combustion
temperature.

Air contains 21% O
2

and 78% N
2
. Efforts to reduce N
2

in the intake air
failed so
f
ar.

Instead, O
2

displacem
ent

by CO
2

(combustion dilution by
EGR)

and NO
X
removal in catalytic converter is
used.

NO
X

is

an

air pollutant. Its 2014 legal limit is set to 0.4 g/kWh, which is only 4% of the 2004 limit.
Other pollutants (CO, HC and PM) are also limited in

a
similar ex
tent. Additionally, there are new

EPA

requirements to reduce tailpipe gas CO
2

content and raise fuel efficiency by 20%

in many
US
diesel
vehicle categories
.


2

The EGR solution (
The
current
technology)

To meet
the
legal NO
X

limit, EGR (exhaust gas recycli
ng

between exhaust and intake manifolds
) is used
at low
-

and high
-
pressure
s
. The low
-
pressure exhaust gas is cooled and

recycled

in
part by fraction x
.
That is
,

if the EGR rate is
62% (x=0.62
), then the intake air's O
2

content is reduced
from 21% to 13
%.
H
eywood has shown in 1988 that
NO
X

forms

approximately

in proportion to e
-
11
x
, so

62
% EGR

reduces
NO
X

formation rate

a

~10
00
-
fold.
That is sufficient to meet NO
X

standard
s
, but at the expense
of engine
power and torque losses up to 25
%. In about the same am
ount, the fuel efficiency is

also

lost.

At high engine loads and speeds, EGR is not used.

The high pressure EGR is not cooled. It mainly used to
recycle heat for quick engine warm
-
up.

EGR thus
works against

engine downsizing.

3

The CGR solution (
The propo
sed

technology
)

CGR offers a sing
le
-
action and a

double
-
action CGR solution to the problem.
During or after fuel
injection, a mixture of fuel, air and combustion products is diverted from a cylinder working in its
expansion phase, to the same or another c
ylinder working in its compression phase. To store CGR gas,
the process requires feed
-
return valves and heat
-
insulated chambers or a pipe
,

connecting the cylinders.
In both cases,

combustion gas is recycled in part by fraction of x, which dilu
tes combustio
n just as EGR
does,

however not to the detriment of engine performance

and economy
but rather to its improvement
.


The added recycled mixture accelerates the mixing. The pressure and temperature of the compressed
air elevates faster than via piston
-
work al
one. That shortens the ignition delay and lessens the mixture
penetration at the early combustion phase, which reduces
the detonation rise

rate and the NOx
formation rate. The CGR recycles heat, as well as unburned hydrocarbons and soot for multiple burnin
g
and emission improvement thereof.

CGR thus allows for
compression ratio
drop
and
engine downsizing.

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3.1

The single
-
action CGR

In each cylinder head, a

poppet valve opens at ~9
0
°

CA BTDC
and closes at ~18
° CA ATDC

[Fig. 1
A
-
1F
]
.
During the
~108
° valve open
ing, gas can communicate between the cylinder and a heat insulated
chambe
r, formed in the cylinder head [Fig. 2].
The chamber may be lined with a
metallic

or
ceramic
insert, which maintains combustion temperature during engine runs. The volume of the cham
ber is
about twice the volume of the fully compressed cylinder gas volume. That ensures 62% effective CGR
rate
, which is t
he theoretical 67% rate
reduced by 5% to account for heat loss and
flow
-
work lost by
valve chocking.

For

a
compression ratio

of r=
16.5
, the chamber volume is
~12% cylinder volume.
The
fuel injection begins at ~
1
3
° BTDC

and ends at ~33° ATDC
.

The

valve lift peaks

at

~36° BTDC.

Upon the valve lifting, the near peak cylinder pressure and temperature
retained

gas starts flowing
back
to the
cylinder, which is now working in its compression phase. That adds heat and pressure to the heat
and pressure generated by the piston work.

However, since

in

compressed air
,

pressure c
hanges faster
than temperature
--
around peak valve lift
--
the pressure bal
ances

between the chamber
and cylinder
volumes. Due to the added chamber volume, the compression ratio droops to
r=
15. The pressure
release eases on the piston work expended to compress the air

with

the added
mixture
. Upon the
commencement of fuel injectio
n, the combustion begins in both the cylinder and the chamber with
rapid pressure and temperature rise. The added recycled mixture accelerates the mixing and preheating
rates
.
That shortens the ignition delay and lessens the mixture penetration at the earl
y combustion
phase, which reduces
the detonation rise rate

and the NOx formation rate.


As the
CGR
valve closes, the

added volume is removed and

the combustion gas energy is
expended to
drive the piston (to

power the engine
)
.

Thus,
t
he CGR recycles heat, a
s well as unburned hydrocarbons
and soot for multiple burning

and emission improvement thereof
.

The heat recycling accelerates

e
ngine
warm
-
up time. T
he pressure vs. crankshaft angle
plot
now
bulges

towards the expansion phase,
so
--
proportional
ly to the hea
t recycling ratio
--
the engine torque and power rise by 45%. The peak pressure
drops 10% while the average only 6%. The peak temperature
rises 4% while the average temperature
remains unchanged.
Compared to
62% EGR
, the NO
X

level remains about the
same
,
bu
t
the

PM

formation rate
drops
by
~
62% and the HC and CO formation rates by
~
26%.

The performance increase
by this CGR
allows for either
42%
fuel savings or for
~
19%
engine downsizing.

3.2

The double
-
action CGR

The
double
-
action CGR is similar to the singe
-
action CGR,
but requires a valve opening
-
and
-
closing in the
expansion phase and another one in the compression phase [Ref. 1]. The first charges
CGR gas into
a
pipe
,

which interconnect
s the cylinders
,
while the second one discharges it. If the timing of th
ese actions
allows it, CGR gas may directly flow between the coupled cylinders.
To ensure the required 62% CGR
ratio, t
he pipe volume
now
is about
twice
a cylinder volume. P
ressure balancing during the CGR flow can
happ
en only in special valve timing

achie
vable by

electronic control

only
. That means that during this
CGR action, the CGR raises the pressure and temperature of the cylinder gas.
To

limit

such rises, the
compression ratio may be dropped

by about 10%
.
The CGR efficiency is

dictated
rather by valv
e timing,
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than by volumetric ratios.

Electronic valve control allows transitioning between the single
-

and double
-
acting CGR on demand.

The recycled fuel now has more time to mix with air before the fuel injection. Yet, the mix is so lean that
it ignite
s

o
nly upon fuel injection, however than
,

it ignites volumetrically. That
stretches the

combustion
time

and smoothes

the heat addition curve.
An HCCI assist effect may result, which contributes to
improvement in

flame spreading, combustion
quality and

engine
performance (power and torque)
.

4

Preferred CGR embodiments

The CGR valves preferred to be poppet valves built into the engine head

similarly to

exhaust valves.
However, to clear the piston at around TDC, the valve may need to be recessed by the height of
the
valve lift.

Due to the high temperature and pressure of the CGR gas, its valve can be smaller than the
exhaust valve. That allows enlarging the exhaust valve, which may need to be done if the CGR valve
would displace an exhaust valve, say in a four
-
va
lve per cylinder engine [Fig. 3]. The double
-
action CGR
valves may be face mounted to the engine head [Fig. 4
A
-
4D
]. Pneumatic or hydraulic valves may control
the double
-
acting CGR [Fig. 5
A
-
5B
].
The poppet valves may be operated electro
-
pneumatically [Ref.
2] or
electro
-
hydraulically [Ref. 3].

S
teady

rpm diesel engines, such as electric power generators, which may
include small onboard engines
of diesel
-
hybrid vehicles

and portable or stationary EPG
s
, may be
configured inexpensively with cam operated single
-
action CGR

poppet

valves.


4.1

Manufacturability


The CGR components are widely available in the industry and can be manufactured by normal processes
adopted by car manufacturers. No special material, tolerances or finishes are needed. Common
pneumatic val
ves may be modified by designing the valve pistons as engine pistons with metal rings
.


4.2

Component
size, cost

and
profitability


The single
-
action CGR chamber kit fits into the cylinder head and may not add any cost and weight to
the engine. For a 2
-
lit
re turbo
-
diesel engine, the double
-
action CGR kit, including the valves, pipes and
harnesses fit in a 51x102 mm
2

space running along the engine head, just above the exhaust manifold. An
81 mm cylinder may need a 12 mm CGR pipeline. The kit

may weigh

2 kg a
nd could add 2% to the engine
cost. The electronic control of the CGR may need reprogramming of the ECM.


CGR enables the vehicle to meet emission standards, lengthen the travel range and increase mileage. It
is inexpensive to research, develop and introd
uce to the market. It may
greatly increase

sales, market
share and profits
made
on the
new technology, leading to a unique competitive edge.


5

Proof of concept prototype


A 2010 VW Jetta TDI 2L diesel engine has been retrofitted with CGR [Ref.
4
]. It is k
ept in
a
showroom and
available for inspection and test
-
driving. The test car has been driven 3,800 miles so far.
All test drive
cycles have been conducted on dyno
-
pad or in city and highway.

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5.1

Engine conversion

The CGR was configured with early discharg
e from cylinder with early charge to cylinder, using a cam
driven poppet valve in each cylinder, which was rededicated from exhaust to CGR operation by
regrinding
cam
lobes

[Figs. 5
-
6]
. The CGR gas flow was unidirectional from the two interior to the two
e
xterior cylinders.
Upon pressure balance
,

a

spring
-
loaded mechanical valve with a free
-
body ball
blocked the CGR gas flow in both the feed and the return pipelines. This also served as a CGR shutoff
valve. That enabled testing with or without CGR at will.
Spigots were added for taking engine
-
out and
retained

gas samples for analysis. A flap
-
valve and a tailpipe closure with spigot was added for tailpipe
gas sampling [Ref.
5
]. The gas cyc
le calculations are

explained

in Ref. 1
.

5.2

Testing methods

The brake
power and torque were measured on a dyno
-
pad

[Fig. 7]
. The gas samples were collected in
5
-
gal steel pressure tanks
--
at 1,600 rpm, 2200 rpm and 3800 rpm
--
and analyzed by atomic mass
-
spectrometry and gas
-
chromatography [Ref. 6].

5.3

Test results

At 50
% CGR
rate, the test engine saved 16% fuel and gained 45% power and torque

[Ref. 7]
.
Concurrently, it reduced CO
2

by 16%, NO
X

by 81%, CO by 69%, HC by 69% and PM by 66%

[Figs 8
-
9]
. The
performance gain was

sensitive to the CGR rate
, while the emission cleaning w
as not
[Fig. 10]
. The ECM
greatly reduced the EGR rate without any reprogramming. The 30/42 mpg city/highway stock car
mileage measured 48/36 mpg with CGR. The CGR transformed some soot to graphite (a dry lubricant)
and some hydrocarbon to albocarbon (a s
tronger fuel), indicating
some

qualitative change in the
combustion process. The CGR removed the turbo
-
lag and accelerated
engine
warm
-
up.


6

New technology protection status

Since 2007, 10 pending patents
--
owned by the singe inventor
--
pr
otect the CGR, non
e of which have

been licensed or assigned as of 2010 November. The
double
-
acting

prototype testing ended
and the
single
-
acting one started
on Oct. 23
, 2010
.


7

New technology benefits and drawbacks

The CGR is an inexpensive new diesel engine technology, wh
ich boosts performance and reduces
pollutants to meet emission standards by qualitatively improving the combustion process and the gas
cycle. 62% CGR allows for either 42% fuel savings or 19% engine downsizing and may replace or
supplement EGR technology,
thus makes diesel vehicles more marketable.


Test results measured on a prototype 2010 VW Jetta TDI

proved the claimed benefits of CGR.
Institutions independent from the inventor executed the engine conversion and the testing. On a
double
-
action
50
% CGR, a
long with 16% fuel savings
,

the researchers measured
a
45% increase in
performance (power and torque) and 81% NO
X
, 16% CO
2
, 69% CO & HC and 66% PM reduction
s
.


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CGR dilutes the combustion without oxygen removal. It does not displace intake air, which
allow
s for lea
n operation at any engine speed
-
and
-
load, saving fuel at all times. An all
-
time
constant 62% CGR reduces nitrogen present at combustion from 78% to 48%. The 62% dilution
rate ensures
99%

reduction in NO
X
, which is sufficient to meet emission stand
ards.


That

single
-
action CGR gradually adds the volume of a CGR chamber to the cylinder volume near the end
of the compression phase and gradually removes it past TDC. It concurrently adds CGR gas on high
pressure (a high temperature mixture of air, smoke

and combustibles), which was retained from the
previous combustion
-
expansion cycle of the same cylinder. The result is, accelerated mixing,
a
reduction
in ignition
-
delay and early mixture penetration, extension in combustion duration, smoothing heat
addit
ion, reduction in detonation rise and NO
X

formation rates, all

which improves combustion. The heat
and HC recycling of the CGR adds an HCCI effect, which however is initiated only upon fuel injection. It
spreads the flame and extracts more energy from fuel
. The single
-
action CGR eases on the piston in the
compression phase. That takes away from the torque expended in the compression phase. The result is
increased engine power and torque, without added fuel. The double
-
action CGR allows for a beneficial
low
-
compression
-
ratio engine design.

The CGR however is not
free. The

CGR chamber

requires engine head redesign and requires high
temperature heat insulator and
iron or ceramic
heat retainer inserts. The CGR valve may be a common
poppet valve driven by cam mec
hanism. Hydraulic or pneumatic drive could ensure more control, alas at
extra cost and complexity.
Yet, t
he experimentally proven benefits of CGR outweigh its drawbacks.

CGR
may replace EGR and

may make new markets. Due to the improved fuel economy and
re
duced
need to maintain the current
emission system, on
the present markets
, it makes the
diesel vehicles more marketable.

The CGR is a present
-
technology
-
friendly new
-
technology.


8


References


[Ref. 1]


http://c2g4r8az.info/page3/page3.html


(Gas Cycle
s
)

[Ref. 2]





http://commerce.rosscont
rols.com/webapp/wcs/stores/servlet/RossControls/WebSiteArea/Sup
port/pdfs/Dale_Series_Poppet_Valves_Bulletin_200_A10343.pdf

[Ref. 3]


http://www.sturmanindustries.com/mai
n/hydraulicValveActuation.htm#

[Ref. 4]


http://z9bm324p.info/2.html



(Full Report)

[Ref. 5]


http://z9bm324p.info/4.html



(Interim Report)

[Ref. 6]


http://z9bm324p.info/5.html



(Closing Report)

[Ref. 7]


http://c2g4r8az.info/index.html



(CGR vs. EGR)

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9

Figures


Fig. 1A


Cylinder pressure vs. crankshaft revolution plots compared.



Fig. 1B

Temperature vs.
crankshaft revolution plots compared.


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Fig. 1C

C
ylinder pressure vs. volume plots compared.


Fig. 1D

Engine
torque vs.
crankshaft revolution plots compared.


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Fig. 1E

Cylinder volume vs.
crankshaft revolution plots compared.


Fig. 1F

Compression ratio vs.
crankshaft revolution plots compared.


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Fig. 2

Preferred
single
-
action
CGR chamber

embodiment

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Fig. 3

Em
bodiment schematics

for

CGR
s


Fig. 4A

Hydraulic Valve Actuator example as per Ref. 3

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Fig. 4B


Custom CGR valve operation (
main parts shown only
)




Fig. 4C


Commercial CGR valve example
as per Ref. 2

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Fig. 4
D

Embodiment schematics for double action
common rail
CGR



Fig. 5

Reground cam lobes for CGR

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Fig. 6

CGR pipes in the test engine



Fig. 7


Dyno
-
pad testing and gas sampling

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Fig. 8


Stock engine emission (normalized to CO
2
)


Fig. 9

CGR engine emission (normalized to CO
2
)


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Fig. 10

Performance test results (
stock engine with 5
-
65
% EGR,

test engine with
50
% CGR
)


10

Contact

For further information
or licensing
, please contact the inventor:

Zoltan A. Kemeny, PhD toll free on
888
-
588
-
0999 or on fax 480
-
456
-
0999 (USA) or at
2014LLC@cox.net
.







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©
, 2014 LLC, 2010.