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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.

Determination of knock start 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 easier to calibrate. Experiments were 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 (with IMPO defined as the Integral of Modulus of Pressure Oscillation and MAPO as the Maximum Amplitude of Pressure Oscillation) is proposed as a suitable indicator. In any engine setting, it remains constant under non knocking conditions. When knock occurs, a model deduced from dimensionless analysis allows to determine the oversteps of Knock Limited Spark Timing from IMPO / MAPO measurements with an accuracy lower than 1 CA.

Experiments were conducted on a single cylinder, natural gas fuelled spark ignition engine. Air fuel ratio was varied from about stoichiometric to the lean limit at two different throttle positions with optimum spark timing. Subsequently the engine was tested at constant throttle and equivalence ratio with variable spark timing. COV (coefficient of variation) of IMEP (indicated mean effective pressure) and peak pressure increase with a reduction in equivalence ratio. When the engine starts to misfire there is a drastic increase in the COV of IMEP. Spark timing has a smaller effect on COV of IMEP than on COV of peak pressure. When the spark timing is advanced, COV of peak pressure attains a minimum value just before knock sets in. Prior cycle effects were seen when there was misfire. Spark timing had little influence on the frequency distribution of IMEPs of cycles, which was generally symmetrical about the mean.

Dual fuel engines can use a wide variety of gaseous fuels efficiently while emitting lesser smoke and particulate than their diesel counterparts. In these engines, a primary gaseous fuel, like biogas, producer gas, LPG etc. supplies the major share of the input energy. The aim of this paper is to characterize the combustion process in a dual fuel engine and to develop a model using a combination simple law of Wiebe. The entire combustion process was divided into 3 stages as follows: the premixed combustion of diesel fuel, the premixed combustion of gaseous fuel and the diffusion combustion. The developed model can be used with good agreement to predict the rate of heat release in a dual fuel engine running at constant load and with variable diesel substitution. A fairly good agreement was observed between the simulation and the experimental results (error smaller than 2%).

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 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.

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.

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.

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.

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.

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.