An Improved Method of Determining the TDC Position in a PV-Diagram

Morishita, Mitsue; Kushiyama, Tadashi

doi:10.4271/980625

Cited by 8 publications

(5 citation statements)

References 1 publication

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“…Such a sensor has a substantial cost and its use is not really fast, since it must be fitted in the spark plug or injector hole of the cylinder. A different approach can be followed using a thermodynamic method, whose input is in-cylinder pressure sampled during the compression and expansion strokes: some of these methods, more or less valid, can be found in literature [5,6,7,8,7,8]. This paper will discuss a new thermodynamic approach to the problem of the right determination of the TDC position.…”

Section: Introductionmentioning

confidence: 99%

Determination of TDC in internal combustion engines by a newly developed thermodynamic approach

Pipitone

Beccari

2010

Applied Thermal Engineering

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In-cylinder pressure analysis is nowadays an indispensable tool in internal combustion engine research & development. It allows the measure of some important performance related parameters, such as indicated mean effective pressure (IMEP), mean friction pressure, indicated fuel consumption, heat release rate, mass fraction burned, etc.. Moreover, future automotive engine will probably be equipped with in-cylinder pressure sensors for continuous combustion monitoring and control, in order to fulfil the more and more strict emission limits. For these reasons, in-cylinder pressure analysis must be carried out with maximum accuracy, in order to minimize the effects of its characteristic measurement errors. The exact determination of crank position when the piston is at top dead centre (TDC) is of vital importance, since a 1° degrees error can cause up to a 10% evaluation error on IMEP and 25% error on the heat released by the combustion: the position of the crankshaft (and hence the volume inside the cylinder) should be known with the precision of at least 0.1 crank angle degrees, which is not an easy task, even if the engine dimensions are well known: it corresponds to a piston movement in the order of one tenth of micron, which is very difficult to estimate. A good determination of the TDC position can be pursued by means of a dedicated capacitive TDC sensor, which allows a dynamic measurement (i.e. while engine is running) within the required 0.1 degrees precision [1, 2]. Such a sensor has a substantial cost and its use is not really fast, since it must be fitted in the spark plug or injector hole of the cylinder. A different approach can be followed using a thermodynamic method, whose input is in-cylinder pressure sampled during the compression and expansion strokes: some of these methods, more or less valid, can be found in literature [5,6,7,8,7,8]. This paper will discuss a new thermodynamic approach to the problem of the right determination of the TDC position. The base theory of the method proposed is presented in the first part, while the second part deals with the assessment of the method and its robustness to the most common in-cylinder pressure measurement errors. BASE THEORY OF THE METHODThe compression and expansion processes in a motored (i.e. without combustion) engine can be described observing the energy transformations regarding the unity mass which remains in the cylinder. The first law of thermodynamics states that:where dq represents the elementary specific heat received by the gas from the cylinder walls, p and v represent the gas pressure and specific volume, and u the specific internal energy. The gas involved in the process is air and can be assumed to be a perfect gas, thus the following equations are also valid:being T the gas temperature, c P and c V the constant pressure and constant volume specific heat, and R' the gas constant. The compression-expansion process in a motored engine can be assumed to be frictionless, hence the second law of thermodynamics states that the specifi...

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Section: Introductionmentioning

confidence: 99%

Determination of TDC in internal combustion engines by a newly developed thermodynamic approach

Pipitone

Beccari

2010

Applied Thermal Engineering

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“…Because of this, a RE formulation based on the classical normal to standard normal transformation was also considered. This formulation can be seen in equation (7).…”

Section: Relative Error Formulation Selectionmentioning

confidence: 99%

“…One benefit of using equation (7) in the cost function is that it will favor the metrics with the largest variations closer to their most probable value. If a metric presents little cyclic variability and thus a small spread, the value of the metric for every cycle in that distribution will have a very similar value.…”

Section: Relative Error Formulation Selectionmentioning

confidence: 99%

“…Due to these limitations, alternative methods for processing cylinder pressure data have been proposed. Morishita et al 7 explored the effect of pressure trace parameters on polytropic index and showed three methods to average pressure ensembles (arithmetic mean, least squares and quadratic curve fitting). The study found that the least squares method is more suitable than the quadratic curve fitting and arithmetic mean for estimating this parameter.…”

Section: Introductionmentioning

confidence: 99%

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Determination of a most representative cycle from cylinder pressure ensembles via statistical method using distribution skewness

Gonzalez

Hall

Kolodziej

2021

International Journal of Engine Research

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In internal combustion engine research, cylinder pressure measurements provide valuable information about the underlying thermodynamic and combustion processes, and are typically collected in ensembles of several 100 traces. Although in some particular fields of combustion research all traces are analyzed, in most cases only one trace is studied because analyzing all the traces is impractical due to the large number of collected samples. Instead, an ensemble-averaged pressure trace is commonly calculated and used for analysis. However, this pressure trace is highly smoothed and dynamic information is lost during the averaging process. With the average trace, pressure rise rates are lower and pressure oscillations such as the ones resulting from combustion knock are lost. In this work, a statistical method was developed to determine the “most representative cycle,” which is the cycle from the ensemble that has the pressure trace most representative of the engine operating condition. Eleven characteristic parameters are computed from each pressure trace and probabilistic distributions are obtained for each of the parameters using all the traces in the ensemble. Finally, the most representative cycle is selected by means of a cost function minimization. The benefits of this method are illustrated using experimental data from four very different engine platforms, under four different combustion modes and over a range of operating conditions.

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“…Indicated horsepower (IHP) calculation by measuring the combustion pressure of fuel inside the cylinder requires a crank angle sensor and a cylinder pressure sensor. Research and devices have been developed and applied to measure accurate output performance and reduce combustion analysis errors by supplementing top dead center (TDC) errors [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Effect of Performance by Excessive Advanced Fuel Injection Timing on Marine Diesel Engine

Baek

Jung²,

Vuong

et al. 2023

Applied Sciences

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The injection timing of fuel in a diesel engine affects the combustion condition. Advanced fuel injection prolongs the ignition delay, positively impacting the increase in maximum combustion pressure and improving output. However, excessively advanced fuel injection can cause knocking. Moreover, premature ignition results in increased compression work when the maximum combustion pressure occurs before top dead center (TDC). This study aimed to diagnose and rectify starting failures, noise, and vibrations in a commercially operated ship engine by measuring the combustion pressure during low load operation. The target engine was a 4-stroke diesel, and the fuel injection system was mechanically controlled by a camshaft. The measured engine exhibited a 4.5 °CA error between the TDC, determined by the flywheel mark and the actual TDC. This discrepancy was influenced by excessively advanced fuel injection timing. It was confirmed that fuel injection and ignition were excessively advanced in all cylinders. After readjusting the engine by delaying the fuel injection timing by approximately 10 °CA, the combustion pressure was remeasured. The ignition was delayed by approximately 6.5 °CA at the same load, and the ignition intervals were uniformly adjusted. As the ignition timing was retarded, the compression work decreased and the expansion work increased in each cylinder, resulting in improved output across all cylinders. The amplitude of crankshaft angular velocity variation significantly decreased, improving uneven rotational force.

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An Improved Method of Determining the TDC Position in a PV-Diagram

Cited by 8 publications

References 1 publication

Determination of TDC in internal combustion engines by a newly developed thermodynamic approach

Determination of TDC in internal combustion engines by a newly developed thermodynamic approach

Determination of a most representative cycle from cylinder pressure ensembles via statistical method using distribution skewness

Effect of Performance by Excessive Advanced Fuel Injection Timing on Marine Diesel Engine

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