the rkm engine principle
DESCRIPTION
ANALYSIS OF POTENTIAL INCREASES IN ENERGY EFFICIENCY FOR PISTON COMBUSTION MACHINES WITH UNCONVENTIONAL GEOMETRY ICSAT conference Dr.-Ing. Andreas Gotter, gofficient, Kaarst Dr. Boris Schapiro, RKM, Berlin 26.02.2010. The RKM engine principle. - PowerPoint PPT PresentationTRANSCRIPT
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ANALYSIS OF POTENTIAL INCREASES IN ENERGY EFFICIENCY FOR PISTON COMBUSTION
MACHINES WITH UNCONVENTIONAL GEOMETRY
ICSAT conference
Dr.-Ing. Andreas Gotter, gofficient, Kaarst
Dr. Boris Schapiro, RKM, Berlin
26.02.2010
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The RKM engine principle
RKM (Rollkolbenmotor) engine has different geometry
than other IC engines
Principle:
Rolling piston instead
of oscillating piston
Different variants possible:
Inner piston
Outer piston
For more details, have a look at
the geometry presentations
of RKM engines
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Objective
Target: Analysis of the potential of the RKM engine
How can that be estimated ?
a) Simulation of a final designed RKM engine and compare to start of the art IC engine
- not possible due to to many uncleared parameters yet- would achieve only weak answer for potential (more for the individual design)
b) Identification of boundaries of conventional IC engines, which can be shiftedand simulation of benefit of shifting that boundaries- simulation can be done independent from individual design parameters- gives an good overview of thermodynamic potential
Method of choice
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Thermodynamics
Short excurse to basic thermodynamics of Combustion engines
Overall process efficiency is limited to
basic thermodynamic lawa and depends mainly on- Compression ratio- Isentropic coefficient of process medium
Limitations
Compression ratio is limited by knock
behaviour, if gasoline engine is used
Isentropic coefficient depends on exhaust gas
and drops with raising temperature
Limiting effects in real engine- Non-ideal combustion- Wall heat losses- Friction- Backpressure by exhaust components not perfect valve timing- etc
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
2 4 6 8 10 12 14 16 18 20
Lambda 0,8
Lambda 1,0
Lambda 1,7
Lambda 3,0
Lambda 100
η = 1 – ε1 – κ
-5-
Boundary conditions
Which boundary conditions
a) Limit current IC engine efficiency
b) Could be moved by other engine concepts such as RKM ?
These parameters were identified:
Parameter Current limitation Investigation of up to…
Maximum peak pressure ~120 bar (Otto) 400 bar
~200 bar (Diesel)
Compression ratio ~20 (Diesel) 50
Break mean effective pressure ~25 bar 100 bar (a.m.a.p)
Friction mean effective pressure ~0.5 bar 0.1 bar
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Simulation software SimEngine
The used simulation software is SimEngine
- A product of gofficient- Has capability of complex thermodynamic simulation of all kinds of
- internal combustion engines- water/steam processes
- Is the unique simulation software for integrated simulation of different processes
Features
- Simulates real gas behaviour and has database for many fluids and gases- Stationary and transient calculation of fluid dynamics- Great component library for internal combustion engines- Lots of special analysis functions- Integration of calibration and control database (currently in development)
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Some screenshots of SimEngine
Component library
drawing area
data input
Analysis windows
Simulation software SimEngine
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Results
Variation of Injection timing
Test : Movement of WOT injection timing to earlier comustion angles
Effects : Rising max. pressure,small efficiency improvement with optimum ~6°CA earlier
41.0%
42.0%
43.0%
44.0%
45.0%
46.0%
0 2 4 6 8 10 12
injection timing (°CA rel. to Basis)
effi
cien
cy [
%]
ETA i
ETA e
120
160
200
240
280
320
0 2 4 6 8 10 12
injection timing (°CA rel. to Basis)
max
. p
ress
ure
[b
ar]
16
18
20
22
24
26
28
30
32
34
36
pmax
pmi
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Results
Variation of Compression ratio
Test : Raising compression ratio to extreme values
Effects : Strong rising max. pressure,efficiency improvement of ~2%-points
raising friction
optimum (eta e) ~ 28, optimum (eta i) ~ 32
41.0%
42.0%
43.0%
44.0%
45.0%
46.0%
15 20 25 30 35
compression ratio
effi
cien
cy [
%]
ETA i
ETA e 120
160
200
240
280
320
15 20 25 30 35
compression ratio
max
. p
ressu
re [
bar
]
16
18
20
22
24
26
28
30
32
34
36
imep
[b
ar]
pmax
pmi
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Results
Variation of A/F ratio
Test : Variation of A/F ratio at WOT conditions at const imep (variaton of charge air pressure for compensation)
Effects : slowly rising max. pressure with lean mixtureefficiency improvement of > 2%-points
41,0%
42,0%
43,0%
44,0%
45,0%
46,0%
47,0%
1 1,2 1,4 1,6 1,8 2 2,2 2,4rel. A/F ratio
effi
cien
cy [
%]
ETA i
ETA e
120
160
200
240
280
320
1 1,2 1,4 1,6 1,8 2 2,2 2,4rel. A/F ratio
max
. p
ress
ure
[b
ar]
16
20
24
28
32
36
imep
[b
ar]
pmax
pmi
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Results
Charge Air pressure
Test : Raising charge air pressure ratio to extreme values at constant compression ration of 19.5
Effects : Strong rising max. pressure & imepefficiency improvement of up to 2%-points
41.0%
42.0%
43.0%
44.0%
45.0%
46.0%
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
effi
cien
cy [
%]
ETA i
ETA e 120
160
200
240
280
320
360
400
440
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
max
. p
ress
ure
[b
ar]
16
20
24
28
32
36
40
44
48
imep
[b
ar]
pmax
pmi
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Results
Charge Air pressure
Test : Raising charge air pressure ratio to extreme values at constant compression ration of 26
Effects : Strong rising max. pressure & imepefficiency improvement of up to 2%-points
42.0%
43.0%
44.0%
45.0%
46.0%
47.0%
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
effi
cien
cy [
%]
ETA i
ETA e
120
160
200
240
280
320
360
400
440
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
max
. p
ress
ure
[b
ar]
16
20
24
28
32
36
40
44
48
imep
[b
ar]
pmax
pmi
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Results
Charge Air pressure
Test : Raising charge air pressure ratio to extreme values at constant compression ration of 26 and lean A/F ratio of 1.6
Effects : Strong rising max. pressure,further efficiency improvement, but also raising frictionefficiency @400bar pmax: 47.1% indicated and 45.3% effective
43.0%
44.0%
45.0%
46.0%
47.0%
48.0%
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
effi
cien
cy [
%]
ETA i
ETA e
120
160
200
240
280
320
360
400
440
1.5 2 2.5 3 3.5 4 4.5 5
charge air pressure [bar]
max
. p
ress
ure
[b
ar]
16
20
24
28
32
36
40
44
48
imep
[b
ar]
pmax
pmi
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Conclusion
Friction
The assumption for friction have been calculated with similarity to conventional engines
If fmep could be reduced, the indicated efficiency is the upper efficiency limit
Conclusion
- By exceeding the current boundaries of mechanical engines, there
could an efficiency increasement potential of 7% (=3%-points) be achieved (if other paramters would stay constant)
- Imep and bmep can be increased to values of ~50bar,while engine speed will probably be lower
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Outlook
Outlook
Alternative engine designs such as RKM engines may be an
alternative for special applications with highest demands
Due to high possible pressure ratio and various speed, RKM engines
can also be used as compressors or expanders, e.g. for steam processes
Simulation is an important tool to discover potentials and application
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Thank youfor the attention