Yasin Ust

An approach for analysing transportation costs and a case study

One of the important parameters in the determination of optimal transportation system is economy. Therefore, a realistic method based on the technical, economical and operational parameters of various transportation modes, namely, road, railway, and sea routes is required in the analysis of costs. This method will take into consideration the probable price escalations during the lifetime of a certain transportation system. The cost of a unit of cargo or passenger per route length should be considered since it is an indicator of economics. In this paper, an approach for transportation cost analysis based on the economic analysis of the alternative modes of cargo or passenger transportation, is presented.

The effects of intercooling and regeneration on the thermo-ecological performance analysis of an irreversible-closed Brayton heat engine with variable-temperature thermal reservoirs

A thermo-ecological performance analysis of an irreversible intercooled and regenerated closed Brayton heat engine exchanging heat with variable-temperature thermal reservoirs is presented. The effects of intercooling and regeneration are given special emphasis and investigated in detail. A comparative performance analysis considering the objective functions of an ecological coefficient of performance, an ecological function proposed by Angulo-Brown and power output is also carried out. The results indicate that the optimal total isentropic temperature ratio and intercooling isentropic temperature ratio at the maximum ecological coefficient of performance conditions (ECOPmax) are always less than those of at the maximum ecological function ( ) and the maximum power output conditions ( ) leading to a design that requires less investment cost. It is also concluded that a design at ECOPmax conditions has the advantage of higher thermal efficiency and a lesser entropy generation rate, but at the cost of a slight power loss.

Optimization of a regenerative gas-turbine cogeneration system based on a new exergetic performance criterion: Exergetic performance coefficient

Abstract A performance analysis and an optimization based on a new exergetic performance criterion named exergetic performance coefficient (EPC) have been carried out for an irreversible regenerative gas-turbine cogeneration system. The EPC objective function defined as the total exergy output per unit loss rate of availability is taken as the optimization criterion. The design parameters and performances under optimal conditions have been investigated and the results obtained are compared with those obtained using the alternative criteria given in the literature. It is shown that for the regenerative gas-turbine cogeneration system, a design based on the maximum EPC conditions is more advantageous from the viewpoint of entropy generation rate, exergy efficiency, and investment cost.

Ecological coefficient of performance (ECOP) optimization for an irreversible Brayton heat engine with variable-temperature thermal reservoirs

An ecological performance analysis for an irreversible Brayton heat engine with variabletemperature thermal reservoirs based on the ecological criterion called Ecological Coefficient of Performance (ECOP) is presented. The model considered includes irreversibilities due to finiterate heat transfer and internal dissipations. The effects of design parameters such as isentropic temperature ratio, heat exchanger effectiveness, thermal reservoir inlet temperature ratio and the ratio of hot-to-cold thermal capacity rates of thermal reservoirs, on the general and optimal ecological performances have been investigated in detail. Comparisons of the results with those of an alternative ecological objective function defined in the literature, the maximum power output conditions, and thermal efficiency are also provided.

Ecological coefficient of performance (ECOP) optimization for generalized irreversible Carnot heat engines

A performance analysis and optimization based on a new thermoecological criterion has been performed for a generalized irreversible Carnot heat engine with losses due to heat transfer across finite temperature differences, heat leak and internal irreversibilities. The ratio of the power produced by the engine to the loss rate of availability, which is named ecological coefficient of performance (ECOP), has been taken as an objective function for the optimization. The maximum of the ecological coefficient of performance function and the corresponding optimal conditions have been derived analytically. The effects of internal irreversibilities, heat leakage and source temperature ratio on the global and optimal performances have been investigated. The results are compared with those of the ecological performance criterion in the literature.

New method to reduce NOx emissions of diesel engines: electronically controlled steam injection system

In this study, the electronically controlled water steam injection (ESI) system was introduced as a new method to reduce NOx emissions. In this system, the energy required for obtaining steam was supplied from exhaust gases. Throttling by injector, pressured and heated water, which is in the form of saturated liquid, becomes superheated steam; thus, the corrosion problem caused by condensation is prevented. It was determined in full load condition engine tests that NOx emissions reduce up to 33%, power and moment increase up to 3% and specific fuel consumption decrease up to 5%. When a steam injection system was tried in engine running with 20% biodiesel, it was determined that all the emission parameters, also including NOx, reduced. As a result, the ESI system is considered to be an important method that can be adapted easily in cruise ships, ferries sailing in continental waters and merchant ships in order to reduce NOx emissions.

Investigation of Heat Transfer Influences on Performance of Air-Standard Irreversible Dual-Miller Cycle

An analysis has been performed for an irreversible dual-Miller cycle with late inlet valve closing (LIVC), taking into consideration the influences of heat transfer loss and internal irreversibilit...

Determination of the optimum temperatures and mass ratios of steam injected into turbocharged internal combustion engines

Water injection method into the internal combustion engines is commonly used to improve performance and emissions. However, condensed water causes to deteriorate the lubrication oil, in-cylinder corrosion is carried out and also wear rate of moving parts of engine increases. In order to prevent this bad effect of condensed water, steam injection is proposed. Electronically controlled steam injected method has been used for naturally aspirated engines and successful results have been obtained in terms of performance and NOx emissions. However, supercharged engine systems are used in practical life. In this study, steam injection method is developed for turbocharged systems. The optimum temperatures and mass ratios are determined based on thermo dynamical analyses.

Heat transfer effects on the performance of an air–standard irreversible dual cycle

The objective of this study is to analyse the effects of heat transfer loss and internal irreversibilites, resulting from adiabatic processes, on an irreversible diesel heat engine. Thermodynamic optimisation has been carried out based on the Maximum Power (MP), Maximum Thermal Efficiency (MEF) and Maximum mean Effective Pressure (MEP) criteria for the dual cycle. Power output, thermal efficiency and mean effective pressure are obtained by introducing variable compression ratio, inlet temperature, combustion and heat transfer constants, and compression and expansion efficiencies. Optimal performance and design parameters of the dual cycle are obtained numerically for the MP, MEF and MEP conditions. The optimal compression ratio and pressure ratio at MEP conditions are compared with those results obtained by using the MP and MEF criteria for different constants of heat transfer and combustion in the characteristic grid curves. The results obtained in this paper may provide a guide to the performance and improvement of practical diesel engines.

Performance optimisation of irreversible cogeneration systems based on a new exergetic performance criterion: exergy density

AbstractThis paper reports a new kind of exergetic performance analysis for a general cogeneration system model. In the model considered, the irreversibilities due to finite rate heat transfer, internal dissipations and the possible heat leakage between heat source and heat sink are taken into account. A new exergetic performance criterion named the exergy density has been proposed as an objective function which can include the consideration of the system sizes in the analysis. The exergy density function is defined as the ratio of total exergy rate to the maximum volume in the cycle. The general and optimal performances based on the exergy density objective have been investigated. The effects of the design parameters such as the ratio of the generated power to the produced heat rate and consumer temperature ratio on the global and optimal performance have been discussed. The obtained results based on the exergy density criterion are compared with the total exergy rate in terms of the exergy efficiency an...