Thermodynamic Determination of T.D.C. in Piston Combustion Engines

s̒, Marek J. Sta

doi:10.4271/960610

Cited by 32 publications

(17 citation statements)

References 1 publication

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“…Unlike for the TDC variation, where a TDC offset resulted in ROHR deviation with the same sign in compression and expansion regions, it can be observed that for a pressure offset variation, ROHR curves feature deviations with different signs in compression and expansion regions, which coincides with the results from the Table 1. Figures 2 and 4 thus in addition to the governing equations in Section 2.3 and results generated thereof confirm the basic hypothesis of the proposed method stating that ROHR features different characteristic deviations in the compression phase and the expansion phase when subjected to the TDC and the pressure offset. This further proves the hypothesis that, considering assumption stated after Equation (18) in Section 2.3, it is possible to determine both offset simultaneously using Equations (17) and (18) …”

Section: Qualitative Validation Of the Rohr For The Pressure And Tdc supporting

confidence: 69%

A New Method for Simultaneous Determination of the TDC Offset and the Pressure Offset in Fired Cylinders of an Internal Combustion Engine

et al. 2017

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An innovative computationally efficient method for the simultaneous determination of top dead centre (TDC) offset and pressure offset is presented. It is based on characteristic deviations of the rate of heat release (ROHR) that are specific for both offsets in compression phase and expansion phase after the end of combustion. These characteristic deviations of the ROHR are derived from first principles and they were also confirmed through manual shifts of the pressure trace. The ROHR is calculated based on the first law of thermodynamics using an in-cylinder pressure trace, engine geometrical parameters and operating point specific parameters. The method can be applied in off-line analyses using an averaged pressure trace or in on-line analyses using a single pressure trace. In both application areas the method simultaneously determines the TDC position and the pressure offset within a single processing of the pressure trace, whereas a second refinement step can be performed for obtaining more accurate results as correction factors are determined more accurately using nearly converged input data. Innovative analytic basis of the method allows for significant reduction of the computational times compared to the existing methods for the simultaneous determination of TDC offset and pressure offset in fired conditions. The method was validated on a heavy-duty and a light-duty diesel engine.

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Section: Qualitative Validation Of the Rohr For The Pressure And Tdc supporting

confidence: 69%

A New Method for Simultaneous Determination of the TDC Offset and the Pressure Offset in Fired Cylinders of an Internal Combustion Engine

et al. 2017

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“…The calculations resulted in a θ loss of − 0.4 °CA, which is near the reported values of − 1.0 °CA [26], 0.35 °CA [27] and 0.7 °CA [28]. The small differences may be accounted to some dependence of θ loss on engine configuration, which ranged from 4-cylinder spark ignition [27] to 6-cylinder supercharged diesel engine [28]. Figure 5 shows the in-cylinder pressure and volume of the motored engine, and θ loss .…”

Section: Resultssupporting

confidence: 66%

Analysis of processing methods for combustion pressure measurement in a diesel engine

Silva

Oliveira

Sodré

2019

J Braz. Soc. Mech. Sci. Eng.

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This paper analyzes combustion chamber pressure data processing methods related to the number of cycles averaged, top dead center referencing and pressure referencing (pegging). A total of 1000 consecutive engine cycles were measured in a four-cylinder diesel engine. The number of cycles that minimizes the influence of cycle-to-cycle oscillations depends on engine operating conditions and the parameters under analysis. The top dead center (TDC) referencing, using the motored curve, revealed that the thermodynamic loss shifts the peak pressure − 0.4 °CA from TDC. Four pegging methods were compared-least-squares, fixed-point, three-point and two-point-introducing as main novelty the fact they have not been previously investigated on the same baseline conditions. The least-squares based method showed the lowest sensitivity to random noise, but with longer processing time, and the fixed-point method presented higher dispersion in the heat release analysis. The three-point referencing method considers a variable polytropic coefficient, but suffers from noise sensitivity, and the two-point referencing method presented close values and higher dispersion in comparison with the least-squares method. The choice of which method to use depends on the type of analysis, signal quality and processing time available.

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“…This occurs due to heat transfer and mass losses, and the angle interval between these events is named loss angle (Figure 9). Several enough accurate methods have been proposed for determining the loss angle (Pinchon, 1984;Stas, 1996), and usually manufacturers of indicating equipment include in their manual recommendations to estimate loss angle values, which depend on the kind of the engine (spark ignition or diesel) and compression ratio.…”

Section: Crank Angle Measurements and Tdc Position Identificationmentioning

confidence: 99%