Vol 17, No 3 (2023)

BACKGROUND: Low temperature of the intake air is one of the reasons of difficult starting of a cold diesel engine in conditions of negative outside temperatures. For a reliable staring of a cold diesel engine, it is necessary to have the temperature at the end of the compression stroke higher than the fuel self-ignition temperature. As the temperature at the end of the compression stroke is defined, first, by the temperature at the end of the intake stroke, the mentioned condition can be satisfied with preliminary warming of the air entering in a cylinder.

AIMS: The article is devoted to solving the task related to development of a mathematical model of a diesel engine taking into account air pre-heating in the intake system and ensuring simulation of the pre-starting mode, starting and operation of a diesel engine in conditions of low negative outside temperature.

METHODS: The enhanced mathematical model of a diesel engine basing on heat mechanics (thermodynamics of opened systems) which reflects main features of an internal combustion engine (ICE) as the system transforming energy in time domain is proposed in the article. The mathematical model’s equation system is based on laws of conservation of energy and mass, solid bodies’ motion equation and includes differential equations of changing of temperature and density of the working body in a cylinder, in the intake system and in the ICE’s crankcase, the ideal gas state equation as well as differential equations of changing of rotation velocity and rotation angle of an engine’s crankshaft.

RESULTS: The mathematical model was tried out on the example of the 1Ch9.5/8.0 multi-purposed air-cooled diesel engine. The results of simulation of the pre-starting mode, starting and operation of the diesel engine taking into account air pre-heating in the intake system are presented in the article.

CONCLUSIONS: Implementation of air pre-heating at the intake in the design of diesel engines is the most effective way of ensure starting of the engines at low negative outside temperature. The obtained results help to develop recommendations of choosing power and operation modes of pre-heating devices for ensuring starting and operation of diesel engines in conditions of low negative outside temperatures.

BACKGROUND: Modern methods of calculating energy characteristics of steam turbine units (STU) are based on development of digital models. Considering this, the main components of the STU’s model is a model of a multistage turbine.

AIMS: Improvement of existing methods of calculating energy characteristics taking into account influence of efficiency of flow compartments.

METHODS: Results of the studies dealing with new methods of development of energy characteristics of multi-stage turbines are presented in the article. In particular, the new method of considering the influence of changing the efficiency of flow compartments of multi-stage turbines depending on working body flow rate is proposed. The method of calculation of turbine energy characteristics is given. The proposed method is based on development of the model of a turbine unit taking into account changing of technical and economic performance of its specific elements depending on the load.

RESULTS: Results of theoretical justification of a non-linear dependency of turbine flow compartments’ power on working body flow rate based on changing internal efficiency of stages at variable modes described with the Stodola-Fluegel equation are given in the article.

Based on the solution of the Stodola-Fluegel equation, the equation for vane efficiency and the equation of isentropic heat drop, the dependence of flow compartment’s operation efficiency on relative working body flow rate is obtained. The advice for using it when modelling turbines is given.

The analysis of the experimental data obtained at the testing of the PT-60-130/13 steam turbine was carried out. Experimental dependency of the stages’ efficiency on steam flow rate are presented. It is established that the proposed dependency of internal efficiency of turbines’ flow compartments complies with the theoretical and experimental data in a good quality and can be used in calculation of energy characteristics and modelling.

As a practical value of the study, the model of the PT-60-130/13 turbine unit was developed. The mode diagram built with the use of the model and complying with the heat testing results is given.

CONCLUSIONS: The developed model of the turbine unit helps to simulate any operation mode depending on electric and heat loads. In addition, with the use of the model, it is possible to take into account the influence of deviation of external factors from nominal values at development of the system of correction or estimation of fuel consumption increase related to these deviations.

BACKGROUND: When calculating velocities of free precipitation of solid particle in a viscous Newtonian liquid, it is assumed that influence of incoming vessel head can be neglected. Necessity of considering this factor grows with a vessel head getting closer and with decrease of particles’ geometrical size.

AIMS: Development of the method of calculating solid particles’ precipitation rate in a Newtonian fluid considering the incoming vessel head and definition the limits of its application.

METHODS: The known analytical model of motion of precipitating disperses solid particles when approaching a vessel head is analyzed. It is shown that the known model of calculation of solid particles’ precipitation rate near the vessel head needs to be refined.

RESULTS: The proposed modification of the analytical model of definition the solid particles’ precipitation rate considering the existence of a vessel head helps to ensure more credible results from physical standpoint. Recommendations regarding the influence of the Brownian motion of fluid’s molecules on motion of precipitating solid particles are given.

CONCLUSION: Practical value of the study lies in ability to calculate solid particles’ precipitation rate near to a vessel head.

BACKGROUND: During the operation, tractor cabin’s vibration isolators are under the simultaneous load vertical, longitudinal- and lateral-angular vibrations of the cabin. These vibrations have different amplitudes, frequencies and time-domain behavior. It is possible to simulate comprehensive operational loads on vibration isolators only with bench testing.

AIMS: Within this study, the trial to define parameters of loading modes for bench testing of tractor cabin’s vibrational isolators and to define corresponding parameters of drives of the bench loading devices was made.

METHODS: This paper presents explanation and the results of calculation of loading modes parameters for testing of tractor cabin’s vibration isolator at the bench capable of producing loads from vertical, longitudinal- and lateral-angular vibrations of a tractor cabin simultaneously, as well as the results of calculation of corresponding parameters of drives of this bench. The procedure of preparation for testing was developed. This procedure includes estimation of values of operational loads amplitudes and frequencies, the range of change of necessary velocities and torques of electric drives of the bench loading devices and identification of adequate drives with required properties, determination of behavior of force and kinematic excitation reproduced by the test bench. Exemplary calculation of parameters of vertical loading at the considered bench was performed for the AKSS-400M rubber-metal vibration isolator used in cabin suspension of the K-708.4 wheeled tractor. A number of assumptions were made in the calculation. Nominal values of velocity and torque of the electric motor drive of the vertical loading device of the bench were obtained as the results. Thus, the electric motor with the reduction gear made by TRANSTECNO was selected. Characteristics of force and kinematic excitations reproduced by the bench using electric motor frequency control were built.

RESULTS: Analysis of graphs helped to define acceptable range of frequencies reproduced by the bench for operational loads in vertical direction limited by abilities of the selected electric drive.

CONCLUSIONS: The results of calculation of electric drive parameters can be used in design of the considered bench for testing of tractor cabin’s vibration isolators, particularly in the development of loading devices (cam eccentrics, pushers, return springs).

BACKGROUND: Transport service providers and consumers specify requirements to vehicles for increasing energy efficiency, cost reduction, as well as improving ergonomics and comfort. Fuel costs are among the significant costs, so it is very promising to use vehicles with electric drives, such as battery-powered electric vehicles. It is very important for them to have energy-efficient control of traction drives that are the main sources of energy loss, characterized by high efficiency that helps to increase single-charge mileage. To achieve this, it is necessary to form the settings of the requested engine torque using the accelerator pedal only, taking into account traffic conditions, vehicle characteristics over the entire velocity range.

AIMS: Development of the fundamentals and the law of determining the settings of the traction and regenerative torque of a traction electric drive, the run-out mode depending on motion velocity and the accelerator pedal position, taking into account the required level of comfort and ergonomics of control.

METHODS: The law of determining the setting of the traction and regenerative torque of the traction electric drive, the run-out mode were modeled in the MATLAB/Simulink software package.

RESULTS: The fundamentals of building the law of determining of the setting of the traction and regenerative torque of the traction electric drive, the run-out mode for effective control, increasing ergonomics and comfort of a vehicle, as well as the results of virtual simulation of the formation of settings in the MATLAB/Simulink in conditions close to the operational are given in the paper.

CONCLUSIONS: The practical value of the study lies in the possibility of using the proposed law for determining the setting of the traction and regenerative torque of the traction electric drive, the run-out mode for the development of a traction drive control system for transport vehicles.

BACKGROUND: This paper discusses switch inductor generators for special vehicles. A generator is the main source of current that provides consumers with power in all operating modes of the engine, as well as charges an electrical battery. The main requirements that are imposed on generators are defined, such as high reliability and durability, corresponding to the service life of an internal combustion engine, as well as manufacturability, low cost and simple maintenance. It is shown that these requirements are most satisfied by switch inductor generators.

AIMS: Study of switch inductor generators in order to determine their main characteristics and parameters.

METHODS: The calculation of the idling characteristic is based on the circuit equivalent to the magnetic circuit of the inductor machine. The Blondel diagram is used to calculate the current-velocity characteristic.

RESULTS: A review and analysis of switch inductor generators of various design has been carried out. In recent years, anisotropic magnets have been used to increase the power of the generator and reduce its dimensions and weight, which, basically, are mortised to a rotor. The main characteristics and parameters of inductor generators are considered. A characteristic feature of an inductor machine, in comparison with conventional synchronous alternating current machines, is that there is a decrease in the electromotive force generated by the generator at high degrees of saturation, therefore, in inductor machines, the saturation level should be lower than in conventional synchronous ones.

CONCLUSIONS: In this paper, a switch inductor generator with a nominal voltage of 14 V and a maximal recoil current of 72 A was calculated according to a well-known method. As a result of the calculation, the main design parameters of the machine were determined, the calculation of the magnetic circuit of the electric machine was carried out and on the basis of which the idling characteristic was constructed. The calculation of the current-velocity characteristic was carried out using the Blondel diagram.

BACKGROUND: The pace of transport system development not corresponding to current demands of a town is a significant obstacle on the way of achieving target values of business activity and quality of life. One of the main indicators of quality of life in a modern large city is satisfaction with city public transport. The backbone mean of public transport in Saint Petersburg is underground which efficiency indicators are share of accomplishment of train schedule and accomplishment of stations’ operation schedule. However, funding based on subsidies and requirement of proper fulfillment of given efficiency indicators make the Petersburg Underground SUE look for new ways of adaptation of planning and control processes for managing available resources ensuring keeping outdating infrastructure operable and cost reduction based on state-of-the-art informational technologies.

AIMS: Establishment of enlarged hardware facility and basic structural solution necessary for unrolling software for planning and control of maintenance of the underground’s escalator park. The study object is the underground’s escalator park; the study subject is automation of maintenance system.

METHODS: In the first part of the paper, as a result of statistical compilation and comparison of homogeneous data from annual reports of the Petersburg Underground SUE in the tabular form as well as analysis of qualitative and quantitative indicators of the escalator park considering the information on the history of maintenance system formation, the statement was made about existence of interaction between the changes taking place in the city transport system and demands of adaptation of processes of planning and control of operations in the escalator park maintenance system. In the second part of the paper, on the basis of analysis of regulatory framework and requirements to development of data processing centers, the main structural element for implementation of facility of planning and control of performing the underground’s escalator park maintenance was established.

RESULTS: The theoretically valuable result of the study is the found interaction between changes taking place at the level of the city transport system and demands in changing the underground’s escalator park maintenance system for achieving the comprehensive evolution of the transport system. Meanwhile, the basic structure of the hardware-software facility, main structural element of which is the corridor isolation system implementing the tool of adaptation of processes of planning and control the operation, is significantly valuable for practical use.

CONCLUSIONS: Structure and equipment of the hardware-software facility as well as the installed software for monitoring, planning and control of the operations ensuring/not ensuring fulfillment the efficiency indicators give the opportunity to transfer the infrastructure parts from the running hours-based maintenance system to the state-based maintenance system.