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1

Assessing diagnostic applicability of heat release characteristics determined based on ship engine indicator diagrams

100%
Polanowski S.
Polish Maritime Research
|
2009
|
tom 16
|
nr 3
In order to determine indicator diagrams-based heat release characteristics, a single- zone model of net heat release was used for perfect gas. It was proved that when a constant value for isentropic exponent is assumed, the error in determining the characteristics can be limited to 1% at the nominal load. The effect of errors in determining the position of piston TDC, as well as that of gas passages and indicator valves on the calculated characteristics was evaluated. It was shown that for low-speed engines the effect of gas passages in negligible, while for medium-speed engines the characteristics reveal some deformations (waves), which are repeatable for an individual cylinder in the examined engine construction. The results of the performed investigations and analyses suggest possibility and advisability of the use of heat release characteristics in diagnosing ship engines, in particular low-speed machines
2

Determination of location of Top Dead Centre and compression ratio value on the basis of ship engine indicator diagram

100%
Polanowski S.
Polish Maritime Research
|
2008
|
tom 15
|
nr 2
In the polytropic model of compression process, exponent of polytropic compression curve was replaced with a power polynomial in which the piston travel was used as its argument. It was shown that 3rd order polynomial is optimum one. In the model were taken into account the following: design parameters of cylinder, influence of cylinder wear andgas blow-by on compression process, error in determining the piston’s Top Dead Centre (TDC) location, measurement error due to indicator diagram’s truncation. The presented solution of the non-linear model is based on its partial linearization, use of the least squares method as well as on application of the optimum determination methods known in the theory of experiment. The model makes it possible to determine TDC location on indicator diagram dealing with combustion, determination of total compresion ratio, pressure value of indicator diagram truncation, as well as determination of maximum values of compression pressure on the diagrams in which self-ignition occurs before reaching the TDC
3

Application of movable approximation and wavelet decomposition to smoothing-out procedure of ship engine indicator diagrams

100%
Polanowski S.
Polish Maritime Research
|
2007
|
tom 14
|
nr 2
In this paper - on the basis of indicator diagram processing taken as an example - were shown possibilities of the smoothing-out and decomposing of run disturbances with the use of the movable multiple approximation based on the least squares criterion. The notion was defined of movable approximating object and constraints used to form approximation features. It was demonstrated that the multiple approximation can be used to decompose disturbances out of an analyzed run. The obtained smoothing-out results were compared with those obtained from full-interval approximation of runs by means of splines as well as wavelet decomposition with using various wavelets, Wavelet Explorer and Mathematica software. Smoothing-out quality was assessed by comparing runs of first derivatives which play crucial role in the advanced processing of indicator diagrams
4

Hałda Zagórska

100%
Polanowski S.
Przyroda Górnego Śląska
|
2014
|
nr 77
5

Processing methods of measured runs of torque and angular speed of combustion engine propulsion system

100%
Polanowski S.
Polish Maritime Research
|
2006
|
tom 13
|
nr 4
In this paper four processing methods of cyclic data runs, namely : Fourier interpolation and transformation, least-squaresapproximation by means of trigonometric polynomials , synchronous averaging and movable approximation , were presented by using, as an example, discretely measured runs of torque and angular speed. It was demonstrated that for extrac-ting a useful signal out of disturbance background and decomposing the disturbances the appropriate methods are the synchronous averaging and multiple movable approximation. To emerge significant spectral lines from a spectrum the least-squares approximation byusing trigonometric polynomials can be applied. The method contains a criterion for signal filtration andis insensitive to disturbances, run truncation and sampling irregularity. Fast Fourier Transform (FFT) may have an auxiliary significance for preliminary spectral analysis. Its main disadvantage is that in order tobuild a smoothing-out filter its parameters should be determined in advance, e.g. by applying one of theremaining methods
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