Milan Marcic

A New Method for Measuring Fuel-Injection Rate

Abstract The paper deals with the basic principles of use and testing of the new method for measuring injected volumes of liquids. The above method was employed in measuring the injected fuel volume in diesel injection systems, where fuel is injected at time intervals of up to 4 ms. It works by measuring the electric charge deposited by liquid droplets impacting a metal electrode. The electric charge is generated mainly in the injection nozzle, where the fuel rubs against the metal parts of injection nozzle, resulting in one portion of free electrons moving from the metal to the fuel. The fuel then transfers this electric charge to the sensor electrode. Rubbing merely serves to bring many points of the surface into good contact. The electric current appears also due to the temperature gradient in the sensor electrode. The temperature gradient in the electrode is a result of the transformation into heat of kinetic energy of fuel droplets hitting the electrode at velocities of 100–300 m s−1. The electric charge is led from the electrode to the charge amplifier, where it is converted into electric current. The test results showed a very reliable operation of the sensor and a linear dependence of the area under the injection rate curve upon the injected fuel volume. The comparison of the injected rates measured with the charge and Bosch measuring method, which is most frequently utilised today, showed a good matching of results in any operating regime.

Measuring method for diesel multihole injection nozzles

Abstract A vast majority of the medium and high speed diesel engines are equipped with multihole injection nozzles nowadays. Inaccuracies in workmanship and changing hydraulic conditions in the nozzles result in differences in injection rates between individual injection nozzle holes. The new deformational measuring method described in the paper allows injection rate measurement in each injection nozzle hole. The differences in injection rates lead to uneven thermal loads of diesel engine combustion chambers. The criterion of the injected fuel is expressed by the deformation of membrane occurring due to the rapid rise of the fuel in the measuring space and the collision of the pressure wave against the membrane. The pressure wave is generated by the injection of the fuel into the measuring space. The pressure wave is analysed by the theory of hydraulic impact in the high-pressure pipes. The membrane deformation is measured using strain gauges, glued to the membrane and forming the Wheatstone bridge. We devoted special attention to the temperature compensation of the Wheatstone bridge and the membrane, heated up during the measurements. All four strain gauges were arranged in a full Wheatstone bridge configuration and glued to the membrane. The strain gauges are all exposed to identical temperature resulting in a temperature compensated Wheatstone bridge. Described in the paper are the measurements of a three-hole nozzle and the reasons analysed of injection rate differences in the injection nozzle holes. We divided the causes of the inequality in the injection rate into structural and hydraulic groups.

Calculation of elastic modulus and other thermophysical properties for molecular crystals

A mathematical model for the calculation of thermodynamic properties of solids is described. The mathematical model, based on statistical thermodynamics, is designed to assess the impact of atom vibration, the electron excitation, and the effect of binding energy between atoms in a crystal. To calculate the configuration integral, perturbation theory was used with the van der Waals model as the perturbation. The temperature-variable coefficients were introduced into the model. Finally, the model was compared with experimental data, proving a good match.

Influence of Multipolar and Induction Interactions on the Speed of Sound

At large distances between molecules, the intermolecular forces are essentially attractive. They can be classified conveniently into three types, that is, multipolar, induction, and dispersion forces. We consider rigid nonlinear molecules with enough symmetry so those principal axes of the quadrupole tensor of the polarizibility coincide. Multipolar and induction interactions are calculated with the help of quantum mechanical calculations of the intermolecular energy function and the help of perturbation theory. The multipole expansion is terminated at the quadrupole term. The focus is on the development of a mathematical model for calculation of the influence of multipole and induction interactions on the speed of sound and other thermodynamic functions of state. For the calculation of the thermodynamic functions of state, perturbation theory with the Lennard-Jones potential as the reference is used. The thermodynamic and structural properties of the Lennard-Jones system are known from Monte Carlo and molecular dynamics computer simulations. All important contributions are featured (translation, rotation, internal rotation, vibration, intermolecular potential energy, and the influence of electron and nuclei excitation). The analytical results are compared with the experimental data and models obtained by classical thermodynamics and show relatively good agreement.

Development of a mathematical model for the heat transfer of the system man – clothing – environment

Purpose – To develop a mathematical model of the heat transfer from human body to environmental air that will be numerically solved by a personal computer.Design/methodology/approach – Development of the heat transfer model for the system man – clothing – environment is based on studying all forms of dry heat transfer (radiation, convection and conduction).Findings – The advantage of the model for heat transfer is the ability of the fast evaluation of heat transfer for various textile materials incorporated into the clothing system under different ambient conditions.Originality/value – Modelling the heat transfer is original and has an important contribution to thermal comfort.

Valve Gear Refinement

This paper describes a new type of valve gear cam-MULTICAM-which consists of seven curves and allows an optimum cam profile design. In order to calculate the cinematic and dynamic values and to assess the minimum oil film thickness in the valve gear the mathematical model of an ideal valve gear was used. In addition, the comparison of the results between the polysine cam and the new MULTICAM cam design was made. By means of the new cam design the Hertz pressures were reduced at the point of contact between the cam and the cam follower and the lubrication properties at the top of the cam improved.

Approach for Calculating Thermophysical Properties with the Help of Statistical Thermodynamics

In engineering practice, refrigeration and cryogenics are processes of vital importance. To design devices for this field, it is necessary to be familiar with the thermodynamic properties of state in a one-phase and a two-phase environment. In most cases, thermodynamic tables and diagrams are used, as well as different empirical functions obtained from measurements. In our case, quantum statistical thermodynamics were used to calculate thermodynamic properties of state. The mathematical model for calculation of the thermodynamic properties of state in real-gas, one-component systems is treated. The virial expansion theory with quantum corrections was used to calculate the thermodynamic functions of state. The mathematical model of a weakly coupled, highly degenerate quantum fluid is also dealt with. We have calculated the thermodynamic properties of state with the help of the quantum field theory for many particle systems using finite temperature formalism. We used the Feynman-Dyson perturbation theory. We developed the expression for the grand potential of normal Maxwell-Boltzmann systems with the help of Green function temperatures and Feynmans diagrams. The results of the analysis were compared with experimental data, and they show good agreement.

Study of Lennard-Jones Chains for Hydrocarbons

A mathematical model is featured for computing equilibrium thermophysical properties of state in the fluid domain for pure hydrocarbons with the help of classical thermodynamics and statistical associating chain theories. We calculated thermodynamic properties for butane as an example of hydocarbon substances. To calculate the thermodynamic properties of a real fluid, the models based on Lennard‐Jones intermolecular potential were applied. To calculate the thermodynamic properties of a real fluid with the help of classical thermodynamics we used the Tillner‐Roth‐Watanabe‐Wagner (TRWW) equation of the Helmholtz type. We developed the mathematical model for the calculation of all equilibrium thermodynamic functions of state for pure hydrocarbons. The analytical results obtained using statistical thermodynamics are compared with the TRWW model and show relatively good agreement.

THE CALCULATION OF CHEMICAL AND THERMOPHYSICAL PROPERTIES IN PROCESS OF NATURAL GAS COMBUSTION

The presented paper features the mathematical model of computing the chemical and thermophysical properties in process of natural gas combustion.. To identify the parameters of state of combustion products their composition has to be known, which may be determined from chemical equilibrium. The computation is performed by the use of chemical potentials and use of statistical thermodynamics. The paper features all important molecular contributions (translation, rotation, vibration, and intermolecular potential energy) The thermal equation of state with two virial terms is used. The reality of the gas mixture is considered with four components: carbon dioxide, nitrogen, carbon monoxide and water. Virial coefficients are dependent on temperature and mole fractions of the real components. Mixed terms are considered. The caloric equation of state is based on ideal gas statistical thermodynamics. Considered are corrections according to the second law of thermodynamics and thermal equation of state. As the whole computation is based on matrix algebra the expansion of the component number under consideration does not represent any problem. We tested our model in high pressure region (100 bar) and low pressure region (1bar), between temperatures 500-6000K. Our analytic model is compared with other analytical models presented in the literature and show relatively good agreement. At the some time we tested the influence of reality on chemical and thermophysical properties of combustion products.

Velocity of Sound of Binary Mixture R507 and Ternary Mixture R404A

The development of mathematical models for calculation of the velocity of sound and other thermodynamic functions of state for the refrigerant mixtures R507 and R410A is discussed. For the calculation of the thermodynamic functions of state, the perturbation theory with the Lennard-Jones (12-6) potential was used as reference. A model is presented for the calculation of the influence of multipolar, induction, and dispersion interactions. Multipolar interactions are calculated up to octopole moment. All important contributions (translation, rotation, internal rotation, vibration, intermolecular potential energy, and influence of electron and nuclei excitation) are featured. The analytical results are compared with experimental data and models obtained by classical thermodynamics and show quite good agreement. Experimental data have been obtained by dynamic light scattering.