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Research Papers: Internal Combustion Engines

In-Cylinder Pressure Measurement: Requirements for On-Board Engine Control

[+] Author and Article Information
Fabrizio Ponti

DIEM, University of Bologna, Bologna 40136, Italy

J. Eng. Gas Turbines Power 130(3), 032803 (Mar 26, 2008) (9 pages) doi:10.1115/1.2830549 History: Received September 20, 2005; Revised September 16, 2007; Published March 26, 2008

During these last years, passenger vehicles have been equipped with an increasing number of sensors, in an effort to monitor and control their behavior in terms of global performance and emissions. This, together with constantly increasing electronic control unit computing power and data storage capabilities, allowed the development of more efficient engine-vehicle control strategies. In this perspective, new sensors will be employed as soon as their use will be shown to be necessary to design new engine control and diagnostic strategies, and their cost and expected life will be compatible with on-board application. A sensor that has been largely studied in recent years is the in-cylinder pressure one: advanced engine control strategies that make use of the signal coming from such a sensor have been investigated, while reliable and low-cost sensors are being developed to survive for the vehicle life the harsh on-board environment. The signal coming from the in-cylinder pressure is, in fact, very rich in information and could be used, for example, to improve engine torque management (by directly computing the instantaneous indicated torque), to improve air∕fuel ratio control, misfire and knock detection capabilities, engine emission estimation (to be used for DeNOx catalysts purging management as an example), residual gas fraction estimation, etc. Many sensor concepts have been developed, although none seems to actually fully meet both the precision and low-cost requirements necessary for on-board application. This work deals with defining the sensor precision characteristics necessary to effectively implement the aforementioned engine control and diagnostic capabilities improvements. In particular, it will be shown that only the low-frequency signal content has to be precisely measured and is critical for certain application. In addition, the importance of a correct reference of the in-cylinder pressure signal is discussed, and a novel methodology to quickly obtain this information once the engine has been setup with a proper in-cylinder pressure sensor is discussed.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

In-cylinder pressure signal for an L4 MPI engine running at 2200rpm and full load

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Figure 2

In-cylinder pressure signal frequency analysis

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Figure 3

Steady-state tests conducted

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Figure 4

In-cylinder pressure higher order frequency component over the engine operating range for an L4 MPI engine

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Figure 5

Correction terms for the second and fourth sinusoidal frequency components

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Figure 6

Comparison between IMEPmref and IMEPms720.

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Figure 7

Comparison between IMEPmref and IMEPms36

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Figure 8

Comparison between IMEPmref and IMEPms16

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Figure 9

Comparison between IMEPmref and IMEPmcorr16

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Figure 10

Frequency component 1–9 representation on the complex plane for the real and shifted in-cylinder pressure wave forms for the same test of Fig. 1 and θs≅3deg

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Figure 11

Second and fourth frequency components representation on a complex plane for the in-cylinder pressure wave forms acquired during the experimental tests reported in Fig. 3

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Figure 12

Instantaneous engine speed during the two motored tests performed for TDC evaluation (one with normal sense of rotation, the other one with reversed rotation)

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Figure 13

In-cylinder pressure during the two motored tests performed for TDC evaluation

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Figure 14

In-cylinder pressure during the two motored tests performed for TDC evaluation (zoom of Fig. 1)

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Figure 15

Peak pressure position and loss angle determination

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