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The crude oil depletion, as well as aspects related to environmental pollution and global warming has caused researchers to seek alternative fuels. Biogas is one of the most attractive available fuels. It is of great interest both economically and ecologically. However, it faces problems that may compromise its industrial use. The dual-fuel engines have been investigated as a technique for the recovery of these gases and finding solutions to these problems. In the present work, performance and emissions of a direct injection diesel engine were first evaluated in conventional mode and dual fuel mode. The effect of biogas composition, based on methane content, is then examined. Also, dual fuel operation with regard to knock is investigated. The results show that, up to 95% of engine full load, the brake thermal efficiency (BTE) is lower in dual fuel mode. In terms of the specific consumption, although at high load the gap is much less, it is more significant in case of dual fuel mode.

Numerical simulation is a useful and a cost-effective tool for engine cycle prediction. In the present study, a dual Wiebe function is used to approximate the heat release rate in a DI, naturally aspirated diesel engine fuelled with eucalyptus biodiesel/diesel fuel blends and operated at various engine loads. This correlation is fitted to the experimental heat release rate at various operating conditions (fuel nature and engine load) using a least squares regression to find the unknown parameters. The main objective of this study is to propose a model to predict the Wiebe function parameters for more general operating conditions, not only those experimentally tested. For this purpose, an artificial neural network (ANN) is developed on the basis of the experimental data. Engine load and eucalyptus biodiesel/diesel fuel blend are the input layer, while the six parameters of the dual Wiebe function are the output layer.

Natural gas composition depends on when and where it is recovered. Variations of composition affect the performance of combustion systems and the accuracy of delivered energy in fiscal gas metering. This paper presents a methodology to determine combustion properties of natural gases (higher heating value, Wobbe index and the stoichiometric air-fuel ratio). A pseudo-gas formulation is used to determine a composition of the most influent constituents of the natural gas. The pseudo-composition is then determined by solving a nonlinear system of equations using thermal conductivity at three levels of temperature and the carbon dioxide concentration. The tested natural gases are chosen to represent typical European gases as well as to account for large variations of individual components. The error on the combustion properties is less than 0.5% for the most of the examined gases and below 1% for gases with high carbon dioxide fractions.

This study focuses on the development of a simulation software able to predict the car cabin blown air temperature. This software describes the fluid circuits (water, oil and air) and the engine blocks using the nodal method. It aims to enhance the global knowledge of the equipment suppliers in the thermal management between the engine and the rest of the car. A new correlation for the prediction of the engine heat losses is proposed. This correlation predicts the indicated efficiency as a function of engine settings and parameters, obtained from a statistical study. This leads to develop a reduced combustion model, which combined with the simulation software, will offer a real-time running prediction tool.

This paper focuses on the prediction of thermal losses and indicated performance in modern automotive engines. In a previous study, a complete simulation software was developed in order to both predict the car cabin blown air temperature and simulate the fluid circuits temperature. The two-zone, 0-dimensionnal combustion model presented in this paper aims to enhance this software. Theoretical overview reveals that thermal losses can be deduced from a predictive correlation of indicated performance. This correlation is established with a statistical tool and empirical coefficients are proposed. As a result of this study, the simulation software becomes a real-time computing tool that considers variable parameters previously neglected.

This paper focuses on the modelling of the exhaust gas temperature of a spark ignition engine in order to propose a new and non-intrusive method of knock detection. A zero-dimensional model is developed and accounts for the heat transfer amplification due to knock. The heat transfer coefficient is a function of the mass burnt rate because knock intensity is linked to the autoignited mass of fuel. The decrease of exhaust gas enthalpy due to knock is pointed out and analysed for a large tunings and fuel composition range. The numerical results show that a knock indicator based on the calculated maximal temperature and the measured average exhaust gas temperature as well as engine tunings can be developed.

Performance of a compression ignition engine fuelled with animal fat and its emulsions as fuel is evaluated. A single cylinder air-cooled, direct injection diesel engine developing a power output of 2.8 kW at 1500 rev/min is used. Base data is generated with standard diesel fuel. Subsequently, animal fat is modified into its emulsions using water and methanol. Comparison is undertaken with diesel, neat animal fat and its emulsion as fuels. Results show improved performance with animal fat emulsions as compared to neat fat. Peak pressure and rate of pressure rise are increased with animal fat emulsions due to improved combustion rate. Heat release pattern shows higher premixed combustion rate with the emulsions. Higher ignition delay and lower combustion duration are found with animal fat emulsions than neat fat. Drastic reduction in black carbon smoke and NO are found with the emulsions as compared to neat animal fat and neat diesel.

A realistic simulation of engine thermal transient behavior requires a coupling between a combustion model and a thermal model of the engine cooling system. This paper describes a procedure used to realize such a simulation. We will develop reasons that lead us towards the choice of Hohenberg's correlation as an engine heat transfer model. A thermal transient simulation of air blown into the car cabin has been computed on a NEDC driving cycle. An experimental study in a wind tunnel has been carried out to validate the heater core heating power and air temperature simulations.

Reduction of internal combustion engines fuel consumption is permanently researched. It leads automotive companies towards global energetic simulation tools to describe the interactions between the engine and the energy consumer systems. Valeo with the EMN Department of Energetic, develop a vehicle energy management tool. It will be able to describe the interactions between: engine, the car cabin heating system, electrical systems and other energy consumers (additional heating system, air conditioning system) implied in the vehicle operation. The first results given by the simulation model have approached quite accurately, the coolant loop warm-up curve, measured during a vehicle test in wind tunnel. The model solves the energy balance on the oil and coolant loops and computes: the heat flux from engine to coolant, the distribution of coolant flows in branches, the thermal exchanges involved in the heater core, the cooling radiator and the oil cooler.

This paper presents a methodology for a rapid determination of biogas composition using easily detectable physical properties. As biogas is mainly composed of three constituents, it is possible to determine its composition by measuring two physical properties and using specific ternary diagrams. The first part of the work deals with the selection of two physical properties, which are easy and inexpensive to measure, from a group comprising thermal conductivity, viscosity and speed of sound. Then, in the second part, a model to express these properties in terms of ternary composition is presented. It is demonstrated that the composition of a ternary gas mixture can be determined with good precision using the above. The model is applied to specific situations such as the online determination of the lower heating value of biogas without any complicated apparatus like calorimeters or batch techniques (gas chromatographs).

Experiments were conducted on a single cylinder SI engine fuelled by natural gas. Equivalence ratios varying from 0.7 to 1.0 were used and the spark timing was changed from no knock to high knock conditions. Pressure crank angle data from 160 consecutive cycles was analysed. It was found that coefficient of variation of peak pressure (COVPP) and standard deviation of the angle of occurrence of peak pressure (SDAPP) can be used to set the engine for knock free operation. These parameters show a sudden rise from a minimum value that they attain near a spark timing where knock sets in. When the average knock intensity is low, there are two groups of cycles. The first comprises of non-knocking to slightly knocking ones. The other contains cycles with relatively high knock intensity. The sudden emergence of two groups is responsible for the observed trends of SDAPP. At high overall knock intensities the first group is absent.

An extension of a thermodynamic methodology of TDC determination in IC engines is presented. The effect of an error on the TDC position coupled with an error on the compression ratio is analyzed in the temperature-entropy diagram. When the TDC position and the compression ratio are well calibrated, compression and expansion strokes under motoring conditions are symmetrical with respect to the peak temperature in the (T,S) diagram. Moreover, in case of an error on the TDC position, a loop appears, which has no thermodynamic significance. In the same way, in case of a compression ratio error the (T,S) diagram leans. Hence, an easy methodology has been conceived to obtain the right position of TDC and eventually to correct the compression ratio. This methodology is applied on motoring measurements to assess its performance.

A thermodynamic methodology of TDC determination in IC engines based on a motoring pressure-time diagram is presented. This method consists in entropy calculation and temperature-entropy diagram analysis. When the TDC position is well calibrated, compression and expansion strokes under motoring conditions are symmetrical with respect to the peak temperature in the (T,S) diagram. Moreover, in case of error on the TDC position, a loop appears, which has no thermodynamic significance. Hence, an easy methodology has been conceived to obtain the actual position of TDC. This methodology is applied to motoring measurements in order to present its performance, which are compared to usual methods.