Instabilities at the Low-Flow Range of a Turbocharger Compressor

Dehner, Rick; Figurella, Neil; Selamet, Ahmet; Keller, Philip; Becker, Michael; Tallio, K. V.; Miazgowicz, Keith; Wade, Robert

doi:10.4271/2013-01-1886

Cited by 27 publications

(14 citation statements)

References 5 publications

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“…Here, the ratio between inlet and outlet compressor pressure is shown as a function of the reduced mass flow rate for different compressor speeds. The first aspect to be addressed is that the real operating range of the compressor can exceed the operating region shown in Figure 3 (the surge line can be exceeded) [1,3,6]. To avoid interpolation errors, the compressor map has been extrapolated according to the methodology presented by El Hadef et al [2].…”

Section: Turbocharger Speed Calculationmentioning

confidence: 99%

“…Average values of the Fourier expansion applied to Equation (3) return the usual balance equation for the turbocharger assembly: (4) In this case, the effect of turbocharger speed fluctuations on η o (mechanical efficiency) is neglected, since the amplitude of speed fluctuations is very low with respect to turbocharger speed mean value. Taking into account the frequency domain transform of Equation (3) evaluated in correspondence of the combustion harmonic component (harmonic 4, that corresponds to engine order 2 for a 4 cylinders engine with evenly-spaced combustions) and considering that only turbine power will show significant order 2 fluctuations, due to the pulsating exhaust gas flow entering the turbine, it can be obtained: (5) Assuming that a proportional correlation between average power and pulsating power due to the flow exiting by each cylinder exists [11,12], it is possible to write: (6) In addition, since the only speed fluctuation of interest is the one corresponding to engine order 2 (harmonic 4), amplitude, i.e. the amplitude of ω TC first derivative evaluated in the frequency domain, can be written through Equation (7).…”

Section: Turbocharger Speed Fluctuations Estimationmentioning

confidence: 99%

“…The main limit of these methodologies consists in the fact that only turbocharger rotational speed mean value (evaluated over a complete revolution) can be estimated, while no information about the amplitude of speed fluctuations is provided. The knowledge of this quantity would be crucial for the investigation of phenomena due to unsteady flow conditions, such as errors in interpolation/extrapolation of data maps [6] or instabilities at low-flow range [7], and to determine the actual power delivered by the turbine, as it will be discussed in the following. Due to the above reasons, this work has been carried out to demonstrate that the vibration signal coming from one accelerometer mounted on the compressor diffuser can be used to extract both turbocharger speed mean value and speed fluctuations due to pulsating flows.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Non-Intrusive Methodology for Estimation of Speed Fluctuations in Automotive Turbochargers under Unsteady Flow Conditions

Ponti¹,

Ravaglioli²,

Corti³

et al. 2014

SAE Int. J. Engines

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The optimization of turbocharging systems for automotive applications has become crucial in order to increase engine performance and meet the requirements for pollutant emissions and fuel consumption reduction. Unfortunately, performing an optimal turbocharging system control is very difficult, mainly due to the fact that the flow through compressor and turbine is highly unsteady, while only steady flow maps are usually provided by the manufacturer. For these reasons, one of the most important quantities to be used onboard for optimal turbocharger system control is the rotational speed fluctuation, since it provides information both on turbocharger operating point and on the energy of the unsteady flow in the intake and exhaust circuits.This work presents a methodology that allows determining the instantaneous turbocharger rotational speed through a proper frequency processing of the signal coming from one accelerometer mounted on the turbocharger compressor. Consequently, the developed algorithm can be used to determine both rotational speed mean value and the amplitude of speed fluctuations that are caused by unsteady flows. From this last evaluated quantity, it is also possible to obtain an estimation of power delivered by the turbine, that might be used for control and diagnostic purposes.The whole estimation algorithm has been developed and validated for a light duty turbocharged Diesel engine installed in a test cell at the University of Bologna. This paper reports the experimental layout used in this work and the accuracy obtained applying the speed fluctuations estimation procedure to the turbocharged Diesel engine under study.

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Section: Turbocharger Speed Calculationmentioning

confidence: 99%

Section: Turbocharger Speed Fluctuations Estimationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Non-Intrusive Methodology for Estimation of Speed Fluctuations in Automotive Turbochargers under Unsteady Flow Conditions

Ponti¹,

Ravaglioli²,

Corti³

et al. 2014

SAE Int. J. Engines

View full text Add to dashboard Cite

show abstract

“…A closely related approach was taken in [9], where instead of the linear spectrum obtained by |DFT{p}|, the power spectral density S pp obtained by |DFT{p}| 2 is considered; furthermore, the inlet pressure signal measured using a microphone is used instead of the outlet pressure signal. The power spectral density is integrated over an interval from 10 Hz to 30 Hz in order to better capture the signal power in this bandwidth.…”

Section: Surge Criteria For Automotive Turbocharger Compressorsmentioning

confidence: 99%

Analysis of the Turbocharger Compressor Surge Margin Using a Hurst-Exponent-based Criterion

Kerres¹,

Nair²,

Cronhjort³

et al. 2016

SAE Int. J. Engines

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Turbocharger compressors are limited in their operating range at low mass flows by compressor surge, thus restricting internal combustion engine operation at low engine speeds and high mean effective pressures. Since the exact location of the surge line in the compressor map depends on the whole gas exchange system, a safety margin towards surge must be provided. Accurate early surge detection could reduce this margin. During surge, the compressor outlet pressure fluctuates periodically. The Hurst exponent of the compressor outlet pressure is applied in this paper as an indicator to evaluate how close to the surge limit the compressor operates. It is a measure of the time-series memory that approaches zero for anti-persistence of the time series. That is, a Hurst exponent close to zero means a high statistical preference that a high value is followed by a low value, as during surge. Maps of a passenger-car sized turbocharger compressor with inlet geometries that result in different surge lines are measured on a cold gas stand. It is demonstrated that the Hurst exponent in fact decreases as the compressor moves towards surge, and that a constant value of the Hurst exponent can be used as a threshold for stable operation. Transient pressure signals of the compressor entering surge are analyzed in order to evaluate the time lag until surge can be detected using the Hurst exponent. Two surge cycles are usually needed to detect unstable operation. However, since the amplitude of these oscillations is relatively small for the first cycles, detection is possible before the oscillations grow into deep surge.

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“…The linear frequency spectrum obtained by discrete Fourier transform is applied in by Galindo et al [4], Marelli et al [5], and again Andersen et al [3]. The quadratic frequency spectrum -the power spectrum -was chosen instead by Dehner et al [6] and Kerres et al [7,8]. Another way of characterizing signal oscillations is the fluctuation function and its scaling behavior (the Hurst exponent), as proposed in [8,9].…”

Section: Introductionmentioning

confidence: 99%

A Comparison of On-Engine Surge Detection Algorithms using Knock Accelerometers

Kerres¹,

Cronhjort²,

Mihăescu³

et al. 2017

SAE Technical Paper Series

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On-engine surge detection could help in reducing the safety margin towards surge, thus allowing higher boosting pressures and ultimately low-end torque. In this paper, experimental data from a truck turbocharger compressor mounted on the engine is investigated. A short period of compressor surge is provoked through a sudden, large drop in engine load. The compressor housing is equipped with knock accelerometers. Different signal treatments are evaluated for their suitability with respect to on-engine surge detection: the signal root mean square, the power spectral density in the surge frequency band, the recently proposed Hurst exponent, and a closely related concept optimized to detect changes in the underlying scaling behavior of the signal. For validation purposes, a visual observation of the air filter vibrations are also used to diagnose surge. The four signal treatments are compared with respect to their reliability as surge indicator and the time delay between surge onset and indication. Results show that the signal power in the surge frequency band has reasonably good properties as surge indicator. The normal Hurst exponent is problematic, since periodic vibrations from engine firing dominate the scaling behavior. Root mean square and the above mentioned scaling exponent do not measure vibrations caused by surge directly, but rather the reduction in housing vibrations due to the engine load drop; nevertheless, it was found to be possible to design an indicator that gives good results based on the change in scaling behavior.

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Instabilities at the Low-Flow Range of a Turbocharger Compressor

Cited by 27 publications

References 5 publications

Non-Intrusive Methodology for Estimation of Speed Fluctuations in Automotive Turbochargers under Unsteady Flow Conditions

Non-Intrusive Methodology for Estimation of Speed Fluctuations in Automotive Turbochargers under Unsteady Flow Conditions

Analysis of the Turbocharger Compressor Surge Margin Using a Hurst-Exponent-based Criterion

A Comparison of On-Engine Surge Detection Algorithms using Knock Accelerometers

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