Robert Radu

Estimation of a noise level using coarse-grained entropy of experimental time series of internal pressure in a combustion engine

We report our results on non-periodic experimental time series of pressure in a single cylinder spark ignition engine. The experiments were performed for different levels of loading. We estimate the noise level in internal pressure calculating the coarse-grained entropy from variations of maximal pressures in successive cycles. The results show that the dynamics of the combustion is a non-linear multidimensional process mediated by noise. Our results show that so defined level of noise in internal pressure is not monotonous function of loading.

Modeling and Performance Analysis of an Integrated System: Variable Speed Operated Internal Combustion Engine Combined Heat and Power Unit–Photovoltaic Array

The paper presents the model of a combined heat and power (CHP) unit, based on a variable speed internal combustion engine (ICE) interfaced with a photovoltaic (PV) system. This model is validated by means of experimental data obtained on an 85 kWe CHP unit fueled with natural gas and a PV system with a rated power of 17.9 kW. Starting from daily load profiles, the model is applied to investigate the primary energy saving (PES) of the integrated CHP + PV system in several operating conditions and for different sizes of PV array. The results demonstrate the dependence of the CHP performance on the operating mode and a limited convenience of the variable speed strategy. The integrated system operation leads to performance improvements, which depend on the size of the PV component.

SIMULINK-FEMLAB Integrated Dynamic Simulation Model for a PEM Fuel Cell System

The necessity for reliable simulation models, able to support the fuel cell systems development activity, has increased continuously during the last years. The present work proposes a model which integrates the finite element method in a dynamic simulation, in order to achieve higher accuracy and the possibility to investigate the influence of various parameters on the fuel cell dynamics. The model is implemented using MATLAB /SIMULINK and consists of two interacting main subsystems that calculates the fuel cell power response and the stack thermal behavior. The first simulates the mass transport and electrochemical phenomena using a model implemented in FEMLAB , and considers as input parameters the stack geometry, reactants pressure, flow rate and composition, and the stack average temperature. The last parameter is also evaluated by the second model, implemented also in FEMLAB , which considers the stack geometry, cooling air flow rate and ambient temperature. Both models were validated using the experimental data acquired on a Ballard Nexa 1.5kWe proton exchange membrane (PEM) system. The results prove that integrated model simulates with accuracy the dynamics of the proton exchange membrane fuel cell type (PEMFC) system and the interaction between the stack and the auxiliaries. The proposed model was used as a predictive tool for two situations. In the first simulation, with a relative fast dynamic, the model demonstrates that the cooling fan control strategy is essential for transient conditions characterized by a significant load decreasing. In the second, the model estimates the variation of the PEMFC main parameters on a 24h cycle, confirming its reliability.

Investigations of Pyrolysis Syngas Swirl Flames in a Combustor Model

An atmospheric combustor model with optical access for confined, non-premixed swirl-stabilized flames was developed in order to investigate the combustion behaviour of gas turbine flames fired with low-caloric syngases. The applied measuring techniques are Particle Image Velocimetry (PIV) for cold aerodynamic analysis, IR thermometry in open flame conditions, thermocouple traverses and global emissions analyzer in confined flame conditions. Two different fuels were chosen: propane and a synthetic mixture of CH4 , CO, CO2 , H2 having a composition typical of a gas from wood pyrolysis. Thermal powers between ∼5 kW and ∼20 kW were obtained with two different air flow rates and equivalence ratio varied in the range φ = 0.2–1.0. The experimental results constitute a database for the validation of numerical combustion models. Preliminary numerical analysis was carried out with STAR-CD software package.Copyright