Khamid Mahkamov

2-D lumped-parameter thermal modelling of axial flux permanent magnet generators

Results from lumped parameter thermal modeling of an axial flux permanent magnet generator based on the application of the 2-D equivalent thermal circuit are presented. The components of the generator and the internal air-flow domain are split into a system of connected and interacting control volumes. Energy and mass conservation equations are then solved for each of volume to determine its thermal state. This method takes into account heat transfer due to both conduction and convection. Two case studies have been performed to validate the accuracy of the 2-D equivalent thermal circuit model by comparison with CFD results.

Multi-zone diesel fuel spray combustion model for the simulation of a diesel engine running on biofuel

Abstract A mathematical model for the calculation of the multi-zone diesel fuel spray combustion process in compression ignition engines is refined in order to expand its capability to describe the operation of diesel engines running on different bio-fuel blends. As an illustration of the capacity of the proposed model to accurately describe the working process numerical simulations of a Caterpillar diesel engine operating on diesel oil and different soybean methyl ester (SME) blends are presented in this paper. A comparison of these theoretical results with published experimental data for the SME 20 and 40 per cent blends shows good agreement. As the proposed model provides a fairly accurate prediction of the heat release rate during the combustion process and the levels of NOx and PM emission formations the model may be used for the optimisation of the engines design and its working process parameters.

Computations on heat transfer in axial flux permanent magnet machines

Effective cooling is of paramount importance for axial flux permanent magnet (AFPM) machines due to their high power density. This paper presents a computational investigation on the effect of variation in some geometric parameters, (running clearance, rotor groove depth and rotational speed), on the cooling effectiveness of an AFPM machine. The numerical model used has been validated by comparison with a small test rig and the basic flow pattern inside the generator has been described.

Thermal modelling of the building and its HVAC system using Matlab/Simulink

The aim of this paper is to develop a simplified building-HVAC system which could predict the temperature variation within the building and estimate the amount of energy required to get the comfort level using the Matlab/Simulink. For the estimation, this model would take into account of different physical properties of building, location of building, weather, gains and heating system. As a case study, the model has been implemented to a semi-detached dwelling with all the real data. The results obtained from Matlab/Simulink are then compared with another software which is verified against IEA Building Energy Simulation Test (IEA BESTEST) building load and HVAC tests. The main advantage of this model is its simplicity and less computational resources.

Self-Ignition delay prediction in PCCI direct injection diesel engines using multi-zone spray combustion model and detailed chemistry

A multi-zone direct-injection (DI) diesel combustion model has been implemented for full cycle simulation of a turbocharged diesel engine. The above combustion model takes into account the following features of the spray dynamics: • the detailed evolution process of fuel sprays; • interaction of sprays with the in-cylinder swirl and the walls of the combustion chamber; • the evolution of a Near-Wall Flow (NWF) formed as a result of a spray-wall impingement as a function of the impingement angle and the local swirl velocity; • interaction of Near-Wall Flows formed by adjacent sprays; • the effect of gas and wall temperatures on the evaporation rate in the spray and NWF zones. In the model each fuel spray is split into a number of specific zones with different evaporation conditions including in zones formed on the cylinder liner surface and on the cylinder head. The piston bowl in the modelling process is assumed to have an arbitrary axi-symmetric shape. The combustion model considers all known types of injectors including non-central and side injection systems. A NOx calculation sub-model uses detailed chemistry analysis which considers 199 reactions of 33 species. A soot formation calculation sub-model used is the phenomenological one and takes into account the distribution of the Sauter Mean Diameter in injection process. The ignition delay sub-model implements two concepts. The first concept is based on calculations using the conventional empirical equations. In the second approach the ignition delay period is estimated using relevant data in the calculated comprehensive 4-D map of ignition delays. This 4-D map is developed using CHEMKIN detailed chemistry simulations which take into account effects of the temperature, the pressure, the Air/Fuel ratio and the EGR. The above approach is also planned to be used in future for calculations of ignition delays in diesel engines fuelled by bio-fuels. The model has been validated using published experimental data obtained on high-and medium-speed engines. Comparison of results demonstrates a good agreement between theoretical and experimental sets of data. The above sub-models were integrated into DIESEL-RK software, which is a full-cycle engine simulation tool, allowing more advanced analysis of PCCI and HCCI diesels.

Experimental study of the performance of multieffect solar thermal water desalination system

The pilot project of a multistage solar thermal water desalination system has been developed, and experimental investigations have been carried out. This paper presents the results of the testing of the system under laboratory conditions. The results show that the productivity of the developed system is two times higher than that of the conventional solar distillers of the greenhouse type.

Assessment of economical and ecological benefits from deployment of a domestic combined heat and power unit based on its experimental performance

Abstract A number of technologies have been embarked upon for combating the problems of escalating energy requirements and the resulting greenhouse gas emissions. Micro or domestic combined heat and power (CHP) has been considered to be one of such technologies. Estimation of the benefits from implementing a pre-commercial prototype of a WhisperGen Mk 3, Stirling engine based, micro CHP (MCHP) unit, in a typical UK semi-detached house with high efficiency electrical appliances and with a typical non-condensing boiler was carried out and some of these results are presented in this article. The initial stage of the investigations focused on mapping thermal and electrical operational performance of the MCHP through physical experimentation on the pre-production unit. Then, to estimate the economical and environmental benefits over a 12-month period, the typical heat and power demand profiles within a household were modelled. In the final stage of the research, the operation of MCHP was simulated within the household, taking into account information on heat and electricity demands and data on the experimental performance of the domestic CHP system. The simulation indicated that with the application of this pre-commercial prototype as a replacement for the typical non-condensing boiler a 9 per cent reduction in both utility bills (using electricity and natural gas prices that were effective in March 2005) and CO2 emissions with a seasonal efficiency of 86 per cent could be achieved assuming that no auxiliary heating system was used to rapidly compensate the hot water deficit in the storage tank in periods of the high hot water demand.

CFD analysis of the thermal state of an overhead line conductor

At present commercial CFD packages such as Fluent, ANSYS CFX, and Star-CD are widely used for investigation of heat and mass transfer processes in various fields of engineering. These codes can also be successfully applied to estimate the thermal state of major components of electrical distribution networks, such as overhead lines, underground cables and transformers. This paper presents some results obtained from numerical modelling of the temperature field in the Lynx overhead conductor in both cross and parallel wind conditions using 2-D and 3-D CFD models. The CFD results obtained demonstrate that for an applied load of 433 A and considering the summer rating (Lynx conductors ER P27 [1]) the maximum temperature in the conductor is considerably lower (16 degrees) than the prescribed design conductor temperature. This indicates that there is headroom for increasing the ampacity of the conductor.

A "Gamma"-Type Stirling Engine: Some Results of Second-Order Numerical Simulations and Experimental Tests

The paper describes investigations performed on a test rig at the University of Durham (UK) with a small “ �”-type Stirling engine. The engine is equipped with instant pressure and temperature sensors and a set of thermocouples connected to a data acquisition system for the registration of parameters of the working cycle and the experimental performance of the engine. An “in -house” second-order ty pe computer code was used to numerically simulate the working process es of the engine and a comparison of theoretical and numerical data demonstrates that the developed code is capable of predicting the performance of the engine within an accuracy which is acceptable for engineering purposes.

Optimization of Mixture Formation and Combustion in Two-Stroke OP Engine Using Innovative Diesel Spray Combustion Model and Fuel System Simulation Software

In this study theoretical investigations were carried out to determine design and working parameters modifications in order to increase by 20% power output and reduce fuel consumption in a marine two stroke medium speed diesel engine with opposite pistons. To achieve the above aim software packages, such as DIESEL-RK, INJECT and ANSYS, were deployed. The phenomenological multi-zone fuel spray combustion model in DIESEL RK software was refined to take into account complex interactions of fuel sprays and the influence of air swirl in the cylinder on evolution of fuel spays. For this purposes a 3D grid was created with regular cubical cells in the combustion chamber of the engine. The density of mesh was 50 cells across the diameter of the cylinder. In contrast to CFD technique, the transfer of liquid fuel and fuel vapour in the computational grid was carried out using empirical equations which had been validated by other researchers. Such novel approach made it possible to preserve the high speed computational performance of DIESEL-RK and good accuracy of modeling. In this new methodology for calculation of combustion in multiple zones only energy balance equation is solved to calculate the temperature of combustion gases, fuel droplets and process of fuel evaporation. Computational time for modeling of one mode of engines operation takes only few minutes even for the case when 8 side injectors are deployed in the cylinder. For optimisation of angles of sprays orientation a sub-programme is developed in C++ for 3D visualisation of modelling results using the cross platform library OpenGL. With refined model of combustion DIESEL-RK was further developed to make it possible to simulate simultaneous application of several separate fuel injection systems even with supply of different types of fuel into the cylinder. Optimisation of the engine also results in specification of requirements to fuel supply systems. Using such technical specification of requirements and using INJECT software the main design features of the main elements of the high pressure pump, pipe work of the fuel supply system and fuel injector are defined. It was found that the fuel injection pressure should be higher than 2000 bar but lower than 2800 bar so the Common Rail fuel supply system does not have advantages over conventional unit pump systems if no ultra-low limits on the level of emissions are imposed. Finally, the thermal loading of the engines piston was evaluated using ANSYS software. It was found that the maximum temperature on edges of the pistons crown made of cast iron limits the level of enhancing of engines performance.