ULTRA-DOWNSIZING OF INTERNAL COMBUSTION ENGINES€¦ · ULTRA-DOWNSIZING OF INTERNAL COMBUSTION ENGINES Victor Gheorghiu, Prof PhD ME Hamburg University of Applied Sciences, Germany

ULTRA-DOWNSIZING OF INTERNAL COMBUSTION ENGINES

Victor Gheorghiu, Prof PhD ME Hamburg University of Applied Sciences, Germany

1st International Conference on Engine Processes 6-7 June 2013

Content Introduction Aspirated Engines Quasi-Atkinson Cycle Implementation (Symmetrical Crank Mechanism) Real-Atkinson Cycle Implementation (Asymmetrical CM)

Turbocharged Engines Quasi-Atkinson Cycle Implementations (Symmetrical CM) Ultra-Downsizing Concept and Goals of these Investigations Real-Atkinson Cycle Implementations (Asymmetrical CM) Searching for Optimal Ratios between Internal (within cylinder) and

External (within turbocharger) Expansions and Compressions (IC A) Real-Atkinson Cycles for Part & Full Loads for steady AFR by means of

concurrently VCR & Boost Pressure Control (IC B) Evaluation of Maximum Improving Potential of Ultra-Downsizing

Performances and Comparison with Seiliger Cycle by means of an Ideal V,p,T-Model

Conclusion

2 1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu

1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu

3

Introduction Thermodynamic Ways for Improving IFCE* of Engine Cycles and therefore for CO2 Emission Reduction:

Ways 1. Increasing effective compression

ratio 2. Shorten eff. compression stroke (e.g.

delaying intake valve closing) 3. Completing eff. expansion stroke

(e.g. delaying exh. valve opening) 4. Turbo-charging for a concurrent

increase in IFCE & BMEP

Schematic Pressure-Volume diagram of a four stroke Seiliger cycle, where Heat Release is modeled by constant Volume (2-3v), Pressure (3v-3p) and Temperature (3p-3). For this reason this Ideal Cycle can be referred as Seiliger V,p,T-cycle.

Note: Effective compression and expansion strokes of classical ICE cycle (usual named as Seiliger cycle) are almost identical.

*IFCE = Indicated Fuel Conversion Efficiency

4








1.









5



1.

2.




6








1.

2.

3.




7

Introduction Thermodynamic Ways for Improving IFCE of Engine Cycles and therefore for CO2 Emission Reduction:





increase in IFCE & BMEP*

Schematic Pressure-Volume diagram of a four stroke Seiliger cycle, where Heat Release is modeled by constant Volume (2-3v), Pressure (3v-3p) and Temperature (3p-3).

1.

2.

3. 4.



* BMEP = Break Mean Effective Pressure

8

Introduction

Ways 1. Increasing effective

compression ratio 2. Shorten eff. compression

stroke (e.g. delaying intake valve closing)

3. Completing eff. expansion stroke (e.g. delaying exh. valve opening)

4. Turbo-charging for a concurrent increase in IFCE & BMEP

Conclusion: The first three Thermodynamic Ways for improving IFCE lead from Seiliger to Atkinson cycle, i.e. to a cycle with shorted effective compression stroke!

Schematic Pressure-Volume diagrams of classical four stroke Seiliger (left) and Atkinson V,p,T-cycles


9

Introduction Thermodynamic Ways for Improving IFCE & BMEP and

Consequences & Restriction of their Implementation on ICE with Symmetrical (Classical) Crank Mechanism

Thermodynamic Ways

1. Increasing effective compression ratio

2. Shorten eff. compression stroke (e.g. delaying intake valve closing)

3. Completing eff. expansion stroke (e.g. delaying exh. valve opening)

4. Turbo-charging for a concurrent increase in IFCE & BMEP

Consequences & Restrictions

Exceeding pmax , Tmax , NOx (Diesel & SI) limits, knocking occurrence (SI)

Decreased aspirated fluid mass lower BMEP & lower IFCE improvement

Large displacement of the engine heavy engine, lower IFCE improvement

Exceeding pmax , Tmax , NOx (Diesel & SI) limits, knocking occurrence (SI)


Introduction

1. Quasi-Atkinson cycles have been implemented so far mostly with symmetrical crank mechanisms, where intake valves are closed very late on cycle. Thus, a part of charge sucked into cylinder is pushed back to intake pipes, and effective compression stroke is in this way decreased.

2. Real-Atkinson cycles can be implemented only with help of asymmetrical

crank mechanisms. This implementation allow to use concurrently very high boost pressures (to increase IMEP) and higher VCR (to enhance IFCE) and to set them much more independently of each other compared to Seiliger cycles.

Possible Ways for Atkinson Cycle Implementation


How could such asymmetrical crank mechanisms look?

Introduction

1. Quasi-Atkinson cycles have been implemented so far mostly with symmetrical crank mechanisms, where intake valves are closed very late on cycle. Thus, a part of charge sucked into cylinder is pushed back to intake pipes, and effective compression stroke is in this way decreased.

2. Real-Atkinson cycles can be implemented only with help of asymmetrical

crank mechanisms. This implementation allow to use concurrently very high boost pressures (to increase IMEP) and higher VCR (to enhance IFCE) and to set them much more independently of each other compared to Seiliger cycles.

Possible Ways for Atkinson Cycle Implementation


How could such asymmetrical crank mechanisms look?

12

A possible Realisation of such Asymmetrical Crank Mechanism

US 1278563A


13

US 1326129A

An other possible Realisation of such Asymmetrical Crank Mechanism







Conclusion


15 Source: Toyota

Delaying

The questions are: 1. Is this Atkinson cycle

implementation optimal? 2. If not, why?

Quasi-Atkinson cycle

Aspirated Engines Quasi-Atkinson Cycle Implementation of Toyota in Prius II

a) Shorten of Effective Compression Stroke by means of Delaying of Intake Valve Closing & b) Enhancing of Volumetric Compression Ratio (VCR)


16 log(Pressure) - Volume diagrams for 1V and 2V related to SV

SV = Standard Variant (Classical Cycle for Aspirated Engines, Seiliger Cycle) 1V = SV + 100°CA Delayed Intake Valve Closing 2V = 1V + 90% Increased Volumetric Compression Ratio (VCR) ~ Quasi-Atkinson Cycle Implementation of Toyota in Prius II Note: AFR is kept identical (stoichiometric) and heat exchange is not considered (adiabatic cylinder)

intake valve closing in SV

eo = exhaust open ec = exhaust close io = intake open ic = intake close

intake valve closing in 1V

Increased VCR in 2V

intake valve closing in 1V & 2V

Aspirated Engines Simulation of such Quasi-Atkinson Cycle Implementations


17

IFCE - Crank Angle diagram

Pushing out of burned gases consumes more piston work in 1V as in SV because of lower pressure at exhaust valve opening & consequently of sluggish cylinder emptying (reduced free exhaust ratio)

log(Pressure) - Volume diagram

Note: Toyota uses an SI aspirated engine in its Prius II which tries to achieve high efficiency by using an Quasi-Atkinson cycle, where the intake valve is kept open for a large part of the compression stroke and the volumetric compression ratio (VCR) is enhanced.

SV & 1V




18

IFCE - Crank Angle diagram

The forth and back flow through intake valve in 1V causes most important IFCE losses referred to SV. Note: VCR is kept unchanged!

Fluid Mass - Volume diagram

SV & 1V

In 1V remain 46% less mass as in SV in cylinder after scavenging




19

IFCE - Crank Angle diagram Fluid Mass - Volume diagram

SV & 1V & 2V

Only the increasing with 90% of volumetric compression ratio in 2V restores the value of indicated fuel conversion efficiency referred to SV

intake valve closing in 1V & 2V

The forth and back flow through intake valve in 1V causes most important IFCE losses referred to SV



20

log(Pressure) - Volume diagram Volume - Crank Angle diagram

SV = Standard Variant (classical Cycle for Aspirated Engines, Seiliger Cycle) 1V = SV + 100°CA Delayed Intake Valve Closing 2V = 1V + 90% Increased Volumetric Compression Ratio (VCR) 3V = 2V + Modified Crank Mechanism


Increased VCR in 3V

Aspirated Engines Comparison between Quasi- and Real-Atkinson Cycle Implementations

21

+15% for 3V

Simulation Results for Aspirated Engines

6%

The losses caused by the suction and partial expulsion of the fresh charge in 1V & 2V are in 3V eliminated. As result a 15% higher value of IFCE is achieved in 3V related to SV & 2V.

In 3V the entire gas mass sucked in remains in cylinder for combustion. Although the compression stroke is much shorter, the sucked mass in 3V is 6% greater than in 2V.

Fluid Mass - Volume diagram IFCE – Crank Angle diagram 1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu

22

In the case of aspirated engines, where the intake valve is kept open for a large part of the compression, the advantage of performing the cycle using this Quasi-Atkinson cycle implementation is of little benefit for following reasons: The Gain in IFCE is modest and is largely dependent on the fine tuning of all

parameters Pushing out of the burned gases consumed more piston work as in SV Forth & back flow through intake valve causes most important losses in IFCE BMEP is low because of the decreased retained mass of fresh charge in cylinder

before combustion. As consequence a relatively large displacement and therefore heavy engine is needed to power the vehicle.

Supercharging seem to be the necessary solution to compensate the diminishing of BMEP and for enhancing of IFCE.

Aspirated Engines

Conclusion referred to this Quasi-Atkinson Cycle Implementation







Conclusion


Source: Schutting, E, Neureiter, A, Fuchs, Ch., Schwarzenberger, T, Klell, M, Eichlseder, H, Kammerdiener, T: Miller- und Atkinson-Zyklus am aufgeladenen Dieselmotor, MTZ 06 / 2007

24

Turbocharged Engines Quasi-Atkinson Cycle Investigations from Reference [3] on CI Engine

with Symmetrical Crank Mechanism implemented by means of Delaying of Intake Valves Closing

25

Turbocharged Engines Simulations* of such Quasi-Atkinson Cycle Implementations

Pressure - Volume diagram IFCE – Crank Angle diagram

SV-TC & 1V-TC

Delayed Suction in 1V-TC

Very Delayed Suction in 2V-TC

SV-TC = Standard Variant (classical Cycle for Turbocharged Engines) 1V-TC = SV-TC + Delayed Suction + Increased Boost Pressure 2V-TC = 1V-TC + Very Delayed Suction + Increased VCR + Very High Boost Pressure

1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu *Used simulation tool is AVL-BOOST®

Maximum Pressure is kept almost the same

26

Simulation Results SV-TC = Standard Variant 1V-TC = SV-TC + Delayed Suction + Increased Boost Pressure 2V-TC = 1V-TC + Very Delayed Suction + Increased VCR + Very High Boost Pressure

log(Pressure) - Volume diagram IFCE - Crank Angle diagram

VCR

AFR

IMEP

pC , TC

IFCE

Piston Work for Scavenging is very different

Delayed Suction in 1V-TC

Very Delayed Suction in 2V-TC


SV-TC & 1V-TC

27

Temperature - Volume diagram IFCE - Crank Angle diagram

Maximum Pressure & Temperature are kept almost the same, but AFR must be adapted.

VCR

AFR

IMEP

pC , TC

IFCE



SV-TC & 1V-TC

28

Fluid Mass - Volume diagram IFCE - Crank Angle diagram

Flowing back into intake pipe in 1V-TC

lower retained Fluid Mass in 2V-TC

VCR

AFR

IMEP

pC , TC

IFCE

Although the boost pressure is very different, IMEP and IFCE are virtually the same



SV-TC & 1V-TC

29

In 1V-TC (= SV-TC + Delayed Suction) although the boost pressure is 40% higher, IFCE and IMEP are 6% less than in the SV-TC (standard version of Seiliger cycle).

In 2V-TC (= 1V-TC + Very Delayed Suction + Increased VCR + Very High Boost Pressure) the retained fresh charge mass into cylinder is much lower as in the SV-TC. Although the boost pressure in 2V-TC is more than five times higher at virtually the same IMEP, only a minor improvement of the IFCE can be detected. Note: This improvement can be expected to be somewhat better if AFR is kept identical in both cycles.

For these reasons, the Quasi-Atkinson cycle implementations by means of a significant delay of the suction and a strong enhancement of the boost pressure applied to an engine with symmetrical crank mechanism does not represent a suitable solution.

Therefore, a new approach is needed to implement Real-Atkinson Cycles.

Turbocharged Engines

Conclusion referred to these Quasi-Atkinson Cycle Implementations







Conclusion


31

Requirements: To raise IFCE & IMEP simultaneously: The engine must be highly

turbocharged Compression stroke must be much

shorter as expansion stroke and VCR accordingly adapted. Most of Compression of working gas

should occur outside of cylinder and most of Expansion within cylinder.

& to limit Pressure & Temperature Peaks during combustion: Intensive Intercooling Optimizing Ratios between internal

and external compression and expansion VCR must be continuously adapted

to Boost Pressure Level accordingly

Advantages: As an important part of Compression

takes place beyond cylinder, this high compressed fresh charge can be cooled intensively before suction. Following moderate Compression

within cylinder leads to lower temperature peaks during combustion and thus to less NOx raw emissions. Feasible Realization of Real-Atkinson

Cycles for Part & Full Loads for steady AFR by means of concurrently VCR & Boost Pressure Control On SI Engines even with

stoichiometric AFR & without throttling, intensive external EGR, mixture stratifying, HCCI… Only 3-Way Catalysts should be

sufficient for after-treatment

Ultra-Downsizing Concept and Goals of these Investigations

1st ICEP, Berlin 2013, Prof. Dr.-Ing. Victor Gheorghiu

32 1st ICEP, Berlin 2013, Prof. Dr.-Ing. Victor Gheorghiu

1. To look for optimum ratio between internal (i.e. within cylinder) and external (within turbines) expansions of working gas, which leads simultaneously to maximizing IFCE and enabling sufficiently high values of IMEP.

2. To make possible the implementation of Atkinson cycles for part and full loads with steady (e.g. stoichiometric) AFR and without throttling and/or intensive EGR.

3. To evaluate the maximum improving potential of Ultra-Downsizing performances, however avoid the high optimizing effort of all BOOST model parameter.

Simulation Tools:

BOOST (AVL)

BOOST (AVL)

Self made analytical model

Ultra-Downsizing Concept and Goals of these Investigations


BOOST Simulation Tool and Model

BOOST*-Model considers true geometrical dimensions of engine components and losses caused by friction and heat transfer.

Power balances of all three turbochargers (TC) determine actual boost pressure level.

Expansion processes in turbines (Tx) are described by means of their discharge coefficients (mTx). Note: When boost pressure required for preserving pressure limit on cycle is low, superfluous TC are kept for simplicity and comparability in use (i.e. they are not bypassed here).

Inta

ke s

ide

Exha

ust

side


Setting of Simulations Most parameters of BOOST model are selected for a hypothetical engine and are kept unchanged for all simulations, e.g.:

All geometrical dimensions (with exception their of crank mechanism) Valve timing Wall temperatures, heat transfer coefficients, efficiencies and pressure losses of

intercoolers (target efficiency = 0.75, target pressure drop = 5 kPa), friction coefficient in pipes (0.019), blow by gap size of cylinder, frictional characteristic curve of engine etc.

Efficiency of turbochargers (compressor efficiency = 0.75, turbocharger overall efficiency = 0.5)

AFR, engine speed Combustion parameters:

Simple Vibe function (for modeling of heat release) Different positions of TDC on Atkinson cycles are compensated by choosing a

suitable start of combustion (SOC), so that combustion begins in all cycles uniformly at 15°CA before TDC.






Conclusion



1st Goal: Investigation Case of Optimal Ratio between Internal and External Expansions

In Investigation Case A (IC A) VCR is varied and VER is kept steady

Expansion stroke is kept unchanged and compression stroke is varied significantly to allow modification of ratio between internal and external expansions.

Atkinson (Atk) cycles are implemented by varying eccentric radius exx of crank mechanism used.

Seiliger cycle is realized with zero eccentric radius.

TDC

Seiliger

Rela

tive

Pist

on P

ositi

on [-

]

Crank Angle [°]

Expa

nsio

n St

roke

Com

pres

sion

Stro

ke

Inta

ke S

trok

e

Exha

ust S

trok

e

Table shows: VER VCR, mTx, n (engine speed), AFR, SOC, CD (combustion duration), mVibe (exponent of Vibe heat release function), IFCE, IMEP, max(p) and max(T) (maximum cylinder pressure and temperature), pMP8 and TMP8 (mean boost pressure and temperature; i.e. at Measuring Point MP8) and pMP12 and TMP12 (mean exhaust back pressure and temperature; i.e. at MP12) for Cylinder 1 (C1). 37

Parameter and Simulation Results for IC A

MP8

MP12

C1

Inta

ke s

ide

Exha

ust

side

MP8 MP12 C1

Turbine discharge coefficients mTx are tuned in all cycles for reaching max(p) ≈ 230 bar. For reaching approximately same expansion rate in all three turbines, their mTx are set at the same level and compensated with cross sections ratios of turbine output pipes. Hence, only mT3 is adapted for each cycle to meet max(p) ≈ 230 bar.

38


MP8

MP12

C1

Inta

ke s

ide

Exha

ust

side


39


log(Pressure) - Volume diagram IFCE - Crank Angle and Volume - Crank Angle diagrams

Atk e62

TDC

IFCE

[-]

-33%

Forced exhaust



40


In IC A for all Atkinson cycles the aspirated gas mass changes only slightly

Seiliger (VCR=7)

Seiliger (VCR=15)

Atk e62

Fluid Mass - Volume diagram log(Pressure) - Volume diagram




Trends arise from analysis of table values: All Atkinson show better IFCE values than Seiliger cycles. Seiliger cycles reach higher IMEP values because of longer intake stroke and thus

of more aspirated gas mass. IMEP follows IFCE variation and is mostly independent of boost pressure variation

in all Atkinson cycles. Highest IFCE value of Atkinson cycles is not reached in variant with highest VCR,

but in variant where VCR is ≈50% of VER.






Conclusion


43

In Investigation Case B (IC B) VER and VCR are simultaneously varied

Expa

nsio

n St

roke

Com

pres

sion

Stro

ke

All four strokes are simultaneously varied by setting of parameter g while eccentric radius is kept steady to e32. Dashed curve shows null

position (g = 0) where a) expansion & exhaust and b) intake & compression strokes are identical (like IC A).

Inta

ke

Stro

ke

Exha

ust

Stro

ke

Volume - Crank Angle diagram

VIR = Volumetric Intake Ratio VXR = Volumetric Exhaust Ratio

2nd Goal: Atkinson cycles for part & full load for steady AFR, without throttling and/or intensive EGR


44

IC B = simultaneously variation of VER & VCR by steady eccentric radius (e32)

Turbine discharge coefficients mTx should be set appropriately (while parameter g is varied) for fulfilling restriction for maximal cylinder pressure max(p) ≈ 230 bar.

All four volumetric ratios are varied simultaneously by setting parameter g.

null position

≈ 230 bar

max(p) mT1

mT3 mT2

Parameter g Parameter g 1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu

VIR = Volumetric Intake Ratio VXR = Volumetric Exhaust Ratio

45

IFCE varies in all OPs only within a 6% wide band by unchanged heat release! Residual gas resides < 7% IMEP varies between 8.5 and 42 bar max(T) varies between 1800 and 2300 K Boost pressure varies between 2.5 and

12 bar Boost temperature does not exceed

360 K Maximal cylinder back pressure reaches

≈11 bar Max. temperature before T3 (back

temperature) achieves only ≈1000 K

IC B Parameter & Performance at Full & Part Loads (stoichiometric AFR, without Throttling & external EGR)

6%

IFCE Residual Gas

IMEP max(T)


Boost pressure

Boost temperature

Back pressure

Back temperature

46

Comments: Required cylinder back pressure pMP12

diminishes the level of IFCE by ca. 25% because of consumed work for forced exhaust. The load independence of these IFCE

losses is quite unexpected, but if the difference between cylinder pressure at “eo” and cylinder back pressure is noted, the positive effect of free exhaust becomes evident.

IFCE - Crank Angle (right axis) & Volume - Crank Angle diagrams



47

Forced exhaust

Free

exh

aust



Comments: Required cylinder back pressure

pMP12 diminishes the level of IFCE by ca. 25% because of consumed work for forced exhaust. The load independence of these

IFCE losses is quite unexpected, but if the difference between cylinder pressure at “eo” and cylinder back pressure is noted, the positive effect of free exhaust becomes evident.


g+2

g-8






Conclusion


49

3rd Goal: Evaluation of Maximum Improving Potential of Ultra-Downsizing Performances and Comparison with

Seiliger Cycle by means of an Ideal V,p,T-Model

In the case of supercharged engines, the number of parameters which influence the IFCE and BMEP is very high.

As a consequence, the effort to achieve combinations of parameters which maximize the performances of the real (by BOOST) cycle becomes difficult and very time expensive.

For these reasons, the V,p,T analytical model of ideal open cycles have been developed for this purpose (see Appendix).

In ideal V,p,T-cycle the heat is partially released isochorically (2 – 3v), isobarically (3v – 3p) and isothermally (3p – 3). The amounts of heat released isochorically and isobarically depend on the targets

for maximum pressure and temperature on the cycle (i.e. isochorically up to max(p) isobarically up to max(T) and the rest of the heat is released isothermally).


50

Some Details of V,p,T-Model for Open Cycles

V,p,T (dashed curves) with optimized valve timing heat release turbocharging …

BOOST (solid curves)

eo, ec = exhaust open / closed io , ic = intake open / closed


Isentropic exponents for unburned and for burned parts of the working fluid are kept constant throughout the cycle. Entire fuel mass is added to the

cylinder gas mass in the state “3v”. Mass contribution of exhaust rest gas

part is also taken into consideration. Available heat is decreased by the

amount of heat transferred to cylinder wall. In this case, compression, combustion and expansion can be treated adiabatically. Cylinder backpressure (equivalent of

MP12 from the BOOST model) is computed by means of energy balance at the turbocharger for the desired boost pressure.


51

Comparison between simulations doing for IC B by BOOST and V,p,T-Model

1 2

3v 4

5

6

7

Pressure - Volume diagram Fluid Mass - Volume diagram

V,p,T (dashed curves) with optimized valve timing heat release turbocharging …

BOOST (solid curves)

eo, ec = exhaust open / closed io , ic = intake open / closed

52 Parameter g Parameter g Parameter g Parameter g

IFCE

IMEP

pMP8 TMP8

pMP12 TMP12

Residual Gas

κc κe

ψ

AFR

1 - ψ - θ

θ

ma

Heat

Rel

ease

Rat

es

max(p)

max(T)

Ther

mal

Pr

oper

ties

Comparison between simulations doing for IC B by BOOST and V,p,T-Model (max(T) is in BOOST & V,p,T-Model identical)

Maximum improving potential of Ultra-Downsizing performances (max(T) is kept steady in V,p,T-Model)

53 Parameter g Parameter g Parameter g Parameter g

IFCE

IMEP

pMP8 TMP8

pMP12 TMP12

Residual Gas

max(p)

max(T)

κc κe

ψ 1 - ψ - θ

θ

ma

Heat

Rel

ease

Rat

es

Ther

mal

Pr

oper

ties

AFR

54

Asymmetrical Crank Mechanism Used for the next Simulations with V,p,T-Model


g = -17.3 εc = 5.1

g = 10.1 εc = 11.1

g = 18.7 εc = 18.1

Volumetric Ratios - Parameter g & Piston Strokes - Parameter g

diagrams Piston Displacement - Crank Angle diagram

VCR = εc

55

Comparison between Atkinson & Seiliger Cycles by means of the Ideal V,p,T-Model



IFCE - Volume diagram

56

Comparison between Real-Atkinson & Seiliger Cycles by means of the Ideal V,p,T-Model


g = -17.3 εc = 5.1

g = 10.1 εc = 11.1

g = 18.7 εc = 18.1

IFCE = ηi Residual gas = γeg IFCE - Improvement: (ηiS - ηiA)/ηiS = ∆(ηi)/ηiS

Index A = Real-Atkinson (red) Index S = Seiliger (blue)

Boost Press. = pC Back Press. = pT

IFCE- Volume diagram

57

Comparison between Real-Atkinson & Seiliger Cycles by means of the Ideal V,p,T-Model


g = -17.3 εc = 5.1

g = 10.1 εc = 11.1

g = 18.7 εc = 18.1

Boost pressure (pC) and temperature (TC) are kept identical in both cycles . Cylinder back pressure (pT)

values are different because of the different gas mass to be exhausted in both cycles. Note: To assure similar

conditions for cylinder exhaust and, thus, for levels of cylinder back pressure and temperature (i.e. equivalent to pMP12 and TMP12 from BOOST), the pressure ratios for free exhaust φex = p4 / p5 are kept identical in both cycles.

58

CONCLUSION

The optimum ratio between internal and external expansions of the work gases which maximize IFCE is reached when the VCR is close to ca. 50% of VER.

An asymmetrical crank mechanism which permits in addition to vary the VCR makes possible to realize Real-Atkinson cycles for part and full load even with steady AFR & without throttling or intensive EGR.

The presented comparisons between V,p,T and BOOST simulations show that this analytical model of ideal open cycles can simulate real cycles relative accurate and predict correctly the upper limit of cycle performances under given engine operating conditions.

The implementation of Real-Atkinson cycles for turbocharged engines offers the following advantages: a) relatively high IMEP, b) higher IFCE, leading to fewer CO2 emissions and c) lower temperatures during the combustion stage, leading to fewer NOx

raw emissions.

Thank you for your attention! 1st ICEP, Berlin 2013 Prof. Dr.-Ing. Victor Gheorghiu


Contact Information

Victor GHEORGHIU Prof. PhD ME HAW Hamburg University of Applied Sciences Faculty TI, Engineering and Informatics Dpt. MP, Mechanical Engineering Berliner Tor 21 20099 Hamburg, Germany Tel.: + 49 40 42875-8636 Fax: + 49 40 42875-8799 [email protected] [email protected] www.haw-hamburg.de/pers/Gheorghiu www.victor-gheorghiu.de

mailto:[email protected]

mailto:[email protected]

http://www.haw-hamburg.de/pers/Gheorghiu

http://www.victor-gheorghiu.de/



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ULTRA-DOWNSIZING OF INTERNAL COMBUSTION ENGINES€¦ · ULTRA-DOWNSIZING OF INTERNAL COMBUSTION ENGINES Victor Gheorghiu, Prof PhD ME Hamburg University of Applied Sciences, Germany