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Research Papers: Gas Turbines: Aircraft Engine

Impact of Measurement Uncertainty in the Characteristic Maps of a Turbocharger on Engine Performance

[+] Author and Article Information
Holger Mai

Department of Internal Combustion Engines,
Berlin Institute of Technology,
Carnotstr. 1A,
Berlin D-10587, Germany
e-mail: holger.mai@tu-berlin.de

Mathias Vogt

IAV–Automotive Engineering,
Carnotstr. 1,
Berlin D-10587, Germany
e-mail: mathias.vogt@iav.de

Roland Baar

e-mail: roland.baar@tu-berlin.de

Andreas Kinski

e-mail: andreas.kinski@web.de
Department of Internal Combustion Engines,
Berlin Institute of Technology,
Carnotstr. 1A,
Berlin D-10587, Germany

1Corresponding author.

Contributed by the Aircraft Engine Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received August 22, 2013; final manuscript received September 11, 2013; published online November 1, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(2), 021201 (Nov 01, 2013) (12 pages) Paper No: GTP-13-1318; doi: 10.1115/1.4025485 History: Received August 22, 2013; Revised September 11, 2013

The main goal of current engine development is to increase power density and efficiency and to minimize engine emissions. The idea is to obtain the desired power output with a highly charged combustion engine in combination with exhaust gas turbocharging and a very small engine displacement, which is known as downsizing. The selection of a turbocharger is based on the maps of the turbine and compressor, which are usually measured on a test bench. They also provide important boundary conditions on the engine process simulation of a supercharged engine with this turbocharger. In general, a very accurate measurement of the characteristic maps is desired to ensure the best possible matching. However, random and systematic errors have an impact on the measurement results. In order to assess the quality of the measured and calculated values, it is necessary to determine the uncertainties of the measurement variables as accurately as possible; particularly, the error propagation in calculating the efficiencies. The uncertainties are based on a systematic uncertainty component of the sensor and the confidence interval. In this way, the measurement uncertainty is estimated by linear and geometric combination of the calculated random and systematic uncertainties. After that, the respective uncertainty contributions and the identification of the relevant parameters that influence the resulting measurement uncertainty are evaluated. Knowing the measurement uncertainties of the characteristic maps of a turbocharger, the influence on engine operation will be determined with a one-dimensional engine process simulation model. Consequently, the determined measurement uncertainty will be applied as a deviation on the efficiencies and will be investigated in a GT POWER simulation. The impact of the measurement uncertainty on the engine performance is shown on the basis of load steps.

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Figures

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Fig. 1

Classification of measurement deviations, according to Mühl [5]

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Fig. 2

Uncertainty contributions and error propagation in the uncertainty of the isentropic compressor efficiency (left) and the turbine net efficiency (right)

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Fig. 3

Reference characteristic map of the compressor with the isentropic compressor efficiency ηC,is

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Fig. 4

Characteristic map of the compressor with the distribution of the uncertainty ugeo(ηC,is) of the isentropic compressor efficiency ηC,is as a geometric combination

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Fig. 5

Characteristic map of the isentropic compressor efficiency ηC,is and its uncertainty envelope ulinC,is) as a linear combination

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Fig. 6

Characteristic map of the isentropic compressor efficiency ηC,is and its uncertainty envelope ugeo(ηC,is) as a geometric combination

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Fig. 7

Proportion of the the uncertainty contributions urdm(ηC,is) and usys(ηC,is) of the uncertainty ulin(ηC,is) of the isentropic compressor efficiency ηC,is as a linear combination

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Fig. 8

Uncertainty amounts u(xk) of the measured input variables on the measurement uncertainty of u(ηC,is)

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Fig. 9

Extended map of the turbine net efficiency ηT= ηT,is*ηm and its associated distribution of uncertainty ugeo(ηT) as a geometric combination

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Fig. 10

Extended map of the isentropic turbine efficiency ηT,is and its associated distribution of uncertainty ugeo(ηT,is) as a geometric combination

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Fig. 11

Proportion of the uncertainty contributions urdm(ηT,is) and usys(ηT,is) of the uncertainty ulin(ηT,is) of the isentropic turbine efficiency ηT,is as a linear combination

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Fig. 12

Uncertainties u(xk) of the measured input variables as proportions of the measurement uncertainty of u(ηT)

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Fig. 13

Simplified view of the GT POWER model

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Fig. 14

Simulated load step shown in the engine map with the impact of the measurement uncertainty as a geometric combination (ugeo) on the BSFC

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Fig. 15

Simulated load step shown in the compressor map with the values of the measurement uncertainty of the isentropic compressor efficiency as a geometric combination ugeo(ηC,is)

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Fig. 16

Combined TC efficiency (compressor isentropic efficiency ηC,is × net turbine efficiency ηT) and the TC speed during vehicle acceleration depending on the uncertainty propagation method

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Fig. 17

Deviation to standard in acceleration time from 60 km/h to 80 km/h in 5th gear, turbine with the net efficiency ηT (unhatched), and with the isentropic efficiency ηT,is (hatched)

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