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Methods of real-time parametric diagnostics for marine diesel engines

Varbanets Roman, Minchev Dmytro, Kucherenko Yury, Zalozh Vitalii, Kyrylash Olena, Tarasenko Tetyana

Polish Maritime Research

2024

nr 3

71--84

Using modern high-performance microcontrollers with wireless interfaces, built-in ADCs and low overall consumption, we develop a portable, real-time parametric diagnostic system for marine engines. The system is based on the use of modern Android/iOS gadgets that receive information from sensors via Bluetooth and then carry out the necessary calculations and display charts and data in real time. The system developed here uses a combination of a gas pressure sensor in the working cylinder and a vibroacoustic sensor, which expands the diagnostic capabilities of marine diesel engines under operating conditions. This solution allows for diagnosis of the fuel injection system, the valve train mechanism, and several other engine systems. In order to develop a portable diagnostic system for marine diesel engines, it is first necessary to solve the problem of analytically determining top dead centre (TDC), since such a system does not use special sensors for this. An algorithm for determining TDC is proposed here, based on an analysis of the measured pressure diagram rather than its derivative, which minimises the influence of digital and analogue noise. Our algorithm for determining TDC and subsequent data synchronisation is applicable in the absence of information about the actual compression ratio in the cylinder, which is a typical scenario for modern engines with variable valve timing. The algorithm also works under conditions of only approximate data on the charge air pressure, which are refined during the iteration process. A formula is proposed for determining the initial TDC position. Parameters for irregular operation of the engine are considered, and can be calculated in real time using time diagrams of pressure and vibration. Methods for expressly assessing the stability of the functioning of the main engine systems by monitoring and analysing a number of successive operating cycles are considered. To assess the unevenness of operation of the engine, a dispersion estimate of the deviations in the main parameters is used. To enable a comprehensive assessment of the engine stability in real time, the CII (cycle irregularity index) criterion is developed. The data processing methods described in this article provide an accurate estimate of the indicated power, due to the precise determination of TDC, thereby enabling an analysis of the stability of the operating cycles, optimal tuning of the engine systems, and monitoring of the results during operation.

Determining of the optimum size of turbofan engine for obtaining the maximum range of multi-purpose airplane

Wygonik P.

Journal of KONES

2010

Vol. 17, No. 2

511-518

Aircraft range is one of the most important criteria of the assessment of the performance properties of an aircraft. For the needs of the paper the mathematical model of an aircraft (multi-purpose aircraft) and the engine which propels the aircraft was built (turbofan, two-spool, with jet mixer). For the analysis it was chosen so-called typical Breguet model and the conventional range. The models were modified as they should consider the characteristics of the engine in the non-dimensional form. The aim of the simulation research was to discuss the influence of the engine parameters (geometrical and thermodynamic) on the aircraft range, realized mainly in the subsonic and supersonic conditions. The decision which of these conditions can have a significant influence on the selection of the calculating point (i.e. the point which determines the geometrical dimensions of the engine) is difficult as there is no clear direction which aircrafts make up the important share in a mission or missions. It was decided that the parameter which connects the engine geometry with the range model is so-called non-dimensional coefficient of engine geometry which is the relation of the area on the inlet to the engine related to the wing area of the aircraft. It was shown that for various parameters of the engine cycle it is possible to show such a value of the non-dimensional coefficient of geometry which maximizes the aircraft range. The results obtained show opposite requirements as for the engine geometry for the subsonic and supersonic flight. On this basis the compromise solution was proposed to fulfil the requirements of the multi-purpose aircraft.