Entity

Time filter

Source Type

Valladolid, Spain

Reyes M.,University of Valladolid | Tinaut F.V.,University of Valladolid | Gimenez B.,University of Valladolid | Perez A.,CIDAUT Foundation
Fuel | Year: 2014

In this work a study of the influence of the fuel/air equivalence ratio and engine rotational speed on the cycle-to-cycle variations in combustion in a natural gas spark ignition engine is presented. The study considers both classic estimators of cyclic dispersion and a new one, based on the burned mass and burning rate. The engine experimental conditions were as follows: Intake pressure 0.5 bar, while fuel/air equivalence ratio was changed from 1.0 to 0.63, and engine rotational speed was varied from 1000 rpm to 2500 rpm. For each equivalence ratio and engine speed, a diagnosis model is used to process the experimentally obtained combustion pressure data in order to provide combustion relevant results such as the mass burning rate at a cycle level. A procedure based on the use of genetic algorithms is used to obtain a very accurate and objective (without human intervention) adjustment of the optimum parameters needed for combustion diagnosis: angular positioning and pressure offset of the pressure register, dynamic compression ratio, and heat transfer coefficients. The model allows making the diagnosis of series of 830 consecutive engine cycles in an automatic way, increasing the objectivity of the combustion diagnosis. The paper focuses on using the values of the mass fraction burned computed from the pressure register and especially on the analysis of the combustion cycle to cycle variation in the natural gas fuelled engine. A new indicator for the study of cycle-to-cycle variations is proposed, i.e. the standard deviation of the mass fraction burning rate. The values of this new indicator are compared with other classic indicators, showing the same general trends. However, a deeper insight is provided on the combustion cyclic variation when the values of the new indicator are plotted as a function of the mass fraction burned, since this allows analyzing the cyclic variation along the combustion development in each cycle from a mass fraction burned of zero to one, with a relevant value at mass fraction burned of 0.5. More important is that the consideration of the dependence of the combustion variables (density, flame front surface, combustion speed) on the mass fraction burned allows ensemble averaging of all registered cycles for each value of mass fraction burned. This permits using the ensemble averaged mass fraction burning rate as an estimator of combustion speed. The analysis of the general trends of cyclic dispersion when engine speed and equivalence ratio are modified (1000, 1750 and 2500 rpm; 0.7, 0.8, 0.9 and 1.0) indicate that cycle-to-cycle variations show, as expected, a strong dependence on the engine rotational speed, increasing the variation with engine rpm. However, when the standard deviation of mass fraction burning rate is plotted as a function of mass fraction burned, there is a linear dependence on engine rpm, but only a very weak dependence on equivalence ratio. This means that the proposed estimator of cyclic dispersion is sensitive to only flow turbulent intensity and not to equivalence ratio. © 2014 Elsevier Ltd.


Duque-Perez O.,University of Valladolid | Morinigo-Sotelo D.,University of Valladolid | Rodriguez-Carrascal A.,CIDAUT Foundation | Garcia-Escudero L.A.,University of Valladolid | And 2 more authors.
19th International Conference on Electrical Machines, ICEM 2010 | Year: 2010

The introduction of Voltage Source Inverter fed motors has produced significant changes in the field of diagnostics being necessary further research to overcome various challenges. To enhance the diagnosis of motor faults it is advisable to consider as many fault signatures as possible, so, in this paper it is analyzed the detection of broken bars using the spectra around harmonics introduced by the power supply. Since the harmonic content of the voltage waveform and the amplitude of the harmonics depend on the voltage supply, in order to establish diagnosis criteria that are independent of the voltage supply, an induction motor has been tested being supplied by a Programmable Power Source, which has allowed to completely control the harmonic content of the input voltage waveform. The results are discussed and some guidelines for condition monitoring are suggested. ©2010 IEEE.


Duque-Perez O.,University of Valladolid | Morinigo-Sotelo D.,University of Valladolid | Perez-Alonso M.,University of Valladolid | Perez-Alonso M.,Antonio de Nebrija University | And 2 more authors.
SDEMPED 2011 - 8th IEEE Symposium on Diagnostics for Electrical Machines, Power Electronics and Drives | Year: 2011

With the aim of developing an expert system for condition monitoring of cage rotor induction motors fed by power inverters, laboratory tests have been performed on a motor with artificially created eccentricity in order to identify as many fault signatures as possible. The technique used to detect faults is Motor Current Signature Analysis and in this paper it is analyzed if the spectra around the time harmonics 5,roduced by an inverter are suitable for condition monitoring. monitoring. But, taking into account that the harmonic content of the voltage waveform and the amplitude of the harmonics depend on the voltage supply, in order to establish diagnosis criteria independent of the voltage supply, a programmable power source has been used as a motor supply. The results are discussed and some guidelines for condition monitoring are suggested. © 2011 IEEE.


Reyes M.,University of Valladolid | Melgar A.,University of Valladolid | Perez A.,CIDAUT Foundation | Gimenez B.,University of Valladolid
International Journal of Hydrogen Energy | Year: 2013

A methodology is presented for studying the influence of using alternative fuels on the cycle-to-cycle variations of a spark ignition engine which has been fuelled with mixtures of natural gas and hydrogen in different proportions (0-100%). The experimental facility consists of a single-cylindrical spark ignition engine coupled to an asynchronous machine with a constant engine rotation speed of 1500 rpm. A thermodynamic combustion diagnostic model based on genetic algorithms is used to evaluate the combustion chamber pressure data experimentally obtained in the mentioned engine. The model is used to make the pressure diagnosis of series of 830 consecutive engine cycles automatically, with a high grade of objectivity of the combustion analysis, since the relevant adjustment parameters (i.e. pressure offset, effective compression ratio, top dead center angular position, heat transfer coefficients) are calculated by the genetic algorithm. Results indicate that the combustion process is dominated by the turbulence inside the combustion chamber (generated during intake and compression), showing little dependency of combustion variation on the mixture composition. This becomes more evident when relevant combustion variables are plotted versus the Mass Fraction Burned of each mixture. The only exception is the case of 100% hydrogen, due to the inherent higher laminar speed of hydrogen that causes combustion acceleration and thus turbulence generation. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Reyes M.,University of Valladolid | Tinaut F.V.,University of Valladolid | Melgar A.,University of Valladolid | Perez A.,CIDAUT Foundation
International Journal of Hydrogen Energy | Year: 2016

A study is presented of the influence of using mixtures of natural gas and hydrogen in different fractions (0, 25, 50, 75, 100%) on the combustion velocity and cycle-to-cycle variations in a spark ignition engine. The experimental facility consists of a single-cylinder spark ignition engine. The engine rotational speeds are 1000, 1750 and 2500 rpm. Fuel/air equivalence ratio was kept constant equal to 0.7 during the experiments. A two-zone thermodynamic combustion diagnosis model, based on solving the mass and energy conservation equations, is used to analyze the experimentally obtained pressure combustion chamber in the engine. The two-zone model considers a spherical flame front centred at the spark plug, and solves the intersection of the flame front with the piston, cylinder head and cylinder wall, in order to provide the values of the flame radius corresponding to the burned mass volume and the surfaces for heat to the piston and walls. An automatic procedure based on genetic algorithms is used to determine the optimum parameters needed for combustion diagnosis: Angular positioning and pressure offset of the pressure register, dynamic compression ratio, and heat transfer coefficients. The paper focuses on using the values of the burning velocity computed from the pressure register and especially on the analysis of the cycle to cycle variation in the natural gas/hydrogen fuelled engine, quantified through the standard deviation and the coefficient of variation of the burning speed. Increasing the hydrogen content in the mixture with natural gas increases its burning velocity. This effect is linear with hydrogen fraction, except for very high values of the fraction, when the effect of hydrogen dominates combustion. Additionally, and of practical importance, increasing the hydrogen fraction reduces the relative dispersion of combustion. This effect of hydrogen addition on reducing combustion variability is evident from 25% hydrogen content. © 2015 Hydrogen Energy Publications, LLC.

Discover hidden collaborations