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

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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Research Octane Numbers of Primary and Mixed Alcohols from Biomass-Based Syngas

Primary alcohols (ethanol, 1-propanol, 1-butanol, and 1-pentanol) derived from biomass offer a sustainable fuel source that can improve efficiency while reducing carbon dioxide (CO2) emissions. However, the performance of these primary alcohols in spark-ignited engines is relatively unknown. In this work, the performance of primary alcohols was experimentally determined using the research octane number (RON) and the blending research octane number (BRON). The primary alcohol mixture, or "AlcoMix," consists of 75% ethanol, 11% 1-propanol, 8% 1-butanol, and 6% 1-pentanol and was approved by the U.S. EPA for use in blending with gasoline. This mixture is the probable outcome of the thermochemical conversion of biomass using Fischer-Tropsch chemistry with synthesis gas. The purpose of this research was to determine whether AlcoMix might be a suitable replacement for ethanol in fuel blending as an antiknock blending component for spark-ignited engines. As an indicative measure of knock resistance, the RONs of AlcoMix and ethanol were estimated using a modified, validated method in a CFR engine. The antiknock properties of AlcoMix as a blending component in gasoline were determined by estimating the BRON. The results show that the measured RON of the individual primary alcohols closely match published values. Additionally, the RON and BRON of the primary alcohol mixture nearly match those of ethanol. These results indicate that the primary alcohol mixture produced by thermochemical processes could be used as a substitute for ethanol as a primary fuel or as an antiknock blending component. © 2014 American Chemical Society