Estimation of trapped mass by in-cylinder pressure resonance in HCCI engines

High pressure gradients at homogeneous charge compression ignition (HCCI) engines heavily excite the pressure resonance. The pressure resonant frequency depends on speed of sound in the cylinder, and thus on the bulk gas temperature. Present paper profits this relation estimating the trapped mass inside the cylinder. In contrast to other estimation methods in the literature, the presented method is based on the trace of the in-cylinder pressure during the cycle; therefore, it permits a cycle-to-cycle mass estimation, and avoids errors associated with other assumptions, such as heat transfer during compression or initial temperature of the in-cylinder gases. The proposed strategy only needs the pressure signal, a volume estimation and a composition assumption to obtain several trapped mass estimates during one cycle. These estimates can be later combined for providing an error estimate of the measurement, with the assumption of negligible blow-by. The method is demonstrated in two HCCI engines of different size, showing good performance in steady operation and presenting great potential to control transient operation. (C) 2015 Elsevier Ltd. All rights reserved.Luján, JM.; Guardiola, C.; Pla Moreno, B.; Bares-Moreno, P. (2016). Estimation of trapped mass by in-cylinder pressure resonance in HCCI engines. Mechanical Systems and Signal Processing. 66-67:862-874. doi:10.1016/j.ymssp.2015.05.016S86287466-6

Modeling of In-cylinder pressure oscillations under knocking conditions: introduction to pressure envelope curve

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A new indicator for knock detection in gas SI engines

International audienceDetermination of knock onset for any engine tuning remains a difficult work for many engine manufacturers. This study investigates different combinations of existing knock indices in order to produce an upgraded indicator, which is easier to calibrate. Experiments are conducted on a single-cylinder gas engine bounded to combined heat and power (CHP). Effects of spark advance, volumetric efficiency and equivalent ratio are studied under constant speed operation. The ratio IMPO/(MAPO x W) (with IMPO defined as the Integral of Modulus of Pressure Oscillations, MAPO as the Maximum Amplitude of Pressure Oscillations and W as the width of the computational window) is proposed as suitable indice. In any engine setting, it remains constant under no knocking conditions. When knock occurs, a model deduced from dimensionless analysis allows determination of the oversteps of Knock Limited Spark Advance from a single IMPO/(MAPO x W) measurement with an accuracy better than 1 CA. Knock is then studied for different gas qualities by adding propane or carbon dioxide to the fuel. The results show that there is no significant effect of the fuel composition on the proposed indicator, making the model able to calculate KLSA overstep in all the situations. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved

Thermoeconomic Analysis Based on Energy Structure for CHP

International audienceThis paper proposes a unified comparison method for the calculations of thermodynamic efficiencies applied to combined heat and power (CHP) plants. Two new dimensionless indices are introduced. They are used to estimate the influence of technical and economical features on the profitability of a CHP plant. A case of a CHP installation by internal combustion engine is treated as a practical application

Impacts of substation return temperature on district cooling electricity consumption

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Model-based optimization of cooling load distribution between water-cooled centrifugal chillers with variable-speed chilled-water pumps

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Knock prevention of CHP engines by addition of N-2 and CO2 to the natural gas fuel

International audienceThis work focuses on the prevention of knock in the case of spark ignition (SI) engines supplied by natural gas network. The effects of the addition of two inert gases (N-2 and CO2) are experimentally studied. The added volumetric quantities are between 0% and 25% for N-2 and between 0% and 15% for CO2. The thermal efficiency and the emissions of the engine are very slightly affected by the addition, whereas a significant increase of the knock limited spark timing (KLST) is always measured. A twice-higher augmentation of KLST is noted when CO2 is added compared to N2 for an equivalent volumetric concentration. The overall augmentation varies between +1 and +6 degreesCA depending on engine operation. Finally, a law for predicting the KLST augmentation implied by the addition of inert gases is deduced from all the measurements. (C) 2003 Elsevier Science Ltd. All rights reserved

Thermoeconomic analysis method for cogeneration plants

International Conference on Efficiency, Cost Optimisation, Simulation and Environmental Aspects of Energy and Process Systems, UNIV TWENTE ENSCHEDE, TWENTE ENSCHEDE, NETHERLANDS, JUL 05-07, 2000International audienceIn this paper, the authors present a unified comparison method for the calculations of thermodynamic efficiencies applied to combined heat and power. Three new indicators have been introduced: two energetic structure indexes defined to size up the CHP equipment, and a heat recovering ratio that allows to adapt the developed method to open cycles. A comparison between separated solution and prime movers has been studied by using this analysis tool. These indicators have been used to estimate the influence of technical and economical features

An Experimental Study of Knock in a Natural Gas Fuelled Spark Ignition Engine

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