Diesel Cycle Research Articles

Optimal performance for a steady-flow endoreversible refrigerator model including five typical cycles

The optimal performance of a universal endoreversible steady-flow refrigerator cycle consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches with heat transfer loss was analysed using finite-time thermodynamics. The analytical formulae about cooling load, coefficient of performance, exergy loss rate, exergy output rate and ecological criterion of the endoreversible steady-flow refrigerator cycle are derived. Moreover, analysis and optimisation of the model were carried out in order to investigate the effect of the cycle process on the performance of the cycles using numerical examples. The results obtained include the performance characteristics of endoreversible steady-flow Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. The results can provide some theoretical guidance for the design of practical refrigerators.

Finite-time exergoeconomic performance optimization for a universal steady flow irreversible heat pump model

The finite-time exergoeconomic performance of a universal steady flow irreversible heat pump cycle model, which consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches with the losses of heat transfer, heat leakage and internal irreversibility, is analysed and optimized by using the theory of finite-time thermodynamics. The analytical formulae for the heating load, coefficient of performance (COP) and profit rate function of the irreversible heat pump cycle model are derived. The optimal heating load, COP and profit rate characteristics are obtained by searching the optimal heat conductance distributions of the hot- and cold-side heat exchangers for a fixed total heat exchanger inventory. Moreover, analysis and optimization of the cycle performance are carried out in order to investigate the effects of heat leakage, internal irreversibility and price ratio on the performance of the cycle by using numerical examples. It is shown that the heat leakage changes the profit rate characteristics qualitatively, and internal irreversibility decreases the profit rate of the cycle quantitatively. The performance characteristics of the steady flow irreversible Diesel, Atkinson, Otto, Brayton, Dual, Miller and Carnot heat pump cycles are included in the universal results obtained herein.

Realization of the Closed Cycle Diesel Control System

The exhaust gas produced by the diesel engine is reclaimed to the mixing chamber where it was mixed with pure oxygen and argon. The mixture which forms "artificial air" will be used as the diesel intake to achieve the diesel engine’s working in closed cycle. The most critical part in closed cycle diesel engine control system is to control the oxygen concentration and specific heat of the intake. This paper is based on the design of GE9030-based PLC and the monitoring interface used in this paper is designed by KingView6.53, finally, the control of specific heat of the intake, concentration of the oxygen intake and pressure of the intake are realized. Moreover, real-time displaying, gathering and fault alarm of the operating parameters in this system are achieved.

Optimal paths of piston motion of irreversible diesel cycle for minimum entropy generation

A Diesel cycle heat engine with internal and external irreversibility’s of heat transfer and friction, in which the finite rate of combustion is considered and the heat transfer between the working fluid and the environment obeys Newton’s heat transfer law [q≈ Δ(T)], is studied in this paper. Optimal piston motion trajectories for minimizing entropy generation per cycle are derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston motion trajectories for the cases of with piston acceleration constraint on each stroke and the optimal distribution of the total cycle time among the strokes. The optimal piston motion with acceleration constraint for each stroke consists of three segments, including initial maximum acceleration and final maximum deceleration boundary segments, respectively. Numerical examples for optimal configurations are provided, and the results obtained are compared with those obtained when maximizing the work output with Newton’s heat transfer law. The results also show that optimizing the piston motion trajectories could reduce engine entropy generation by more than 20%. This is primarily due to the decrease in entropy generation caused by heat transfer loss on the initial portion of the power stroke.

A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices

A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices The article proposes valuating the operation of an arbitrary diesel engine, based on the sample case of a ship's main engine in which energy conversion processes take place in a given time. The above operation is understood as the energy transfer to the screw propeller in the given time in which the energy conversion into work and/or heat and its further transmission take place. The here proposed method for evaluating the operation of the main engines installed in marine power plants consists in comparing the operation of these engines to a physical quantity the measuring unit of which is the joule-second (joule x second). A new term is introduced which bears the name of the theoretical engine operation and is the standard (ideal) operation which can be compared to the operation of real engines revealing different levels of wear. It was shown that the calculations of the theoretical operation defined in the above way cannot make direct use of commonly known theoretical Diesel and Sabathe cycles. Instead they should use the cycles modified by heat abstraction taking place in accordance with the isobaric, or isothermal process. Other new terms introduced in the article are: the degree of excellence of energy conversion to work, considered as the measure of excellence of engine operation, and the degree of engine operation dissipation, being the measure of its real operation. It is shown that if in time t of engine operation the case takes place that: Li = idem and Le = idem, then the engine operation dissipation is equal to its mechanical efficiency.

디젤엔진축계 진동저감을 위한 스프링-점성 댐퍼의 매개변수 결정 연구

Excessive torsional vibrations from marine engine shafting systems can be reduced by using torsional vibration dampers. But in order to be tuned effectively, the dampers should be designed through the optimum design procedure. In this paper, the procedure to get the optimum values of system parameters of spring-viscous dampers using effective modal mass of inertia and stiffness is suggested and the damping is determined by the exact algebra optimization method. The validity of the suggested method is confirmed through the application to a 1800 kW four cycle diesel engine and generator system.

Analysis of Used Vegetable Oils Treated with Paraíba/Brazil Clays by Kinematic Viscosity

The search for new sources of renewable energy order to minimize environmental impacts has led the scientists to develop new alternatives, such as the use of recycling of frying oils to produce biodiesel. The utilization of fuels of agricultural origin in the cycle diesel engines is a good alternative to reduce dependence on importation petroleum, since these fuels are a renewable source of energy. The utilization of biodiesel as biofuel is a contribution to the environment, reducing the qualitative and quantitative form levels of environmental pollution. However, these oils should go through a process of decontamination and decoloration up the stage of chemical conversion which is used clay to lighten the oil. This study aimed to characterize clay of Paraíba to be used in the clearing of frying oil. It was observed through the technique of kinematic viscosity the clays show good results in treatment used vegetable oils.

Heating load and COP optimizations for a class of generalized irreversible universal steady-flow variable-temperature heat reservoir heat pump cycle model

The heating load and coefficient of performance (COP) of a class of generalized irreversible universal steady-flow heat pump cycle model with variable-temperature heat reservoirs and the losses of heat transfer, heat leakage and internal irreversibility are investigated by using the theory of finite-time thermodynamics. The universal heat pump cycle model consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches. Expressions of heating load and COP of the universal heat pump cycle model are deduced, respectively. By means of numerical calculations, the heat conductance distributions between hot- and cold-side heat exchangers are optimized by taking the maximum heating load as objective. There exist both optimal heat conductance distributions and optimal thermal capacity rate matching between the working fluid and heat reservoirs which lead to the double maximum heating load. The effects of heat leakage, internal irreversibility, total heat exchanger inventory and thermal capacity rate of the working fluid on the optimal performance of the cycle are discussed in detail. The results obtained herein include the optimal performance of endoreversible and irreversible, constant- and variable-temperature heat reservoir Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles. The results obtained can provide some theoretical guidelines for the designs and operations of practical heat pumps.

Finite time exergoeconomic performance for six endoreversible heat engine cycles: Unified description

The operation of a universal steady flow endoreversible heat engine cycle model consisting of two constant thermal-capacity heating branches, a constant thermal-capacity cooling branch and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the universal endoreversible heat engine cycle is investigated by taking profit optimization criterion as the objective. The analytical formulae for power, efficiency and profit rate function of the universal endoreversible heat engine cycle with heat resistance loss are derived. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (efficiency) for endoreversible cycles. Moreover, analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the universal endoreversible heat engine cycle using numerical examples. The results obtained herein include the performance characteristics of six endoreversible heat engines, including Carnot, Diesel, Otto, Atkinson, Brayton and Dual cycles.

Effects of variable specific heat ratio of working fluid on the performance of an irreversible Diesel cycle

SYNOPSIS The effects of the variable specific heat ratio of the working fluid on the performance of a Diesel cycle, with considerations of heat transfer and friction-like term losses, are investigated by using finite time thermodynamics in this paper. The relationships between power output and compression ratio, between thermal efficiency and compression ratio, as well as the optimal relationship between power output and efficiency of the cycle, are derived by detailed numerical examples. The results obtained herein show that the effects of variable specific heat ratio of working fluid on the power output and thermal efficiency of the cycle are significant and should be considered in the design of practical Diesel engines.

Effects of variable specific heat ratio of working fluid on performance of endoreversible Diesel cycle

Abstract The performance of a Diesel cycle with heat transfer loss and variable specific heat ratio of working fluid is analysed. Using finite time thermodynamics, the characteristic curves of the work output v. compression ratio, the thermal efficiency v. compression ratio and the work output v. thermal efficiency are obtained. Moreover, the effects of variable specific heat ratio of working fluid on the cycle performance are significant. The results obtained in this work can help to understand how the cycle performance is influenced by the variation specific heat ratio, and they should be considered in practical cycle analysis.

Exergoeconomic performance optimization for a steady-flow endoreversible refrigerator cycle model including five typical cycles

The operation of a universal steady-flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, a constant thermal-capacity cooling branch and two adiabatic branches is viewed as a production process with exergy as its output. The finite-time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate as the optimization objective. The relations between the profit rate and the temperature ratio of the working fluid, between the coefficient of performance (COP) and the temperature ratio of the working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit) and the utilization factor (COP) for endoreversible cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical examples. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson and Brayton refrigeration cycles. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Effects of varying air-fuel ratio on the performance of a theoretical Diesel cycle

This paper analyses the effects of varying air-fuel ratio on the performance of a theoretical Diesel cycle under a temperature restriction as maximum. Amount of heat addition at constant pressure is defined as a function of fuel's energy with utilising the combustion efficiency. The amount of released energy into the cylinder restricts the compression ratio. Relations between the combustion efficiency and compression ratio and also their limitations are explained. Variation of the compression ratio and combustion efficiency making the work output to maximise are presented. Utilising the combustion efficiency is found to be more useful to realise the cycle feasibility.

A methodology for analysis of diesel engine in-cylinder flow and combustion

A methodology is developed for the analysis of diesel engine in-cylinder processes and combustion. Beginning from CAD data of the engine geometry, the methodology involves use of a commercial code AVL FIRE for simulation of suction stroke, and an open-source code KIVA-3V for simulation of the closed-valve part of the diesel cycle. For this, an algorithm is first developed to map a generalised three-dimensional Computational Fluid Dynamics (CFD) solution from an unstructured mesh in AVL FIRE to a structured mesh in KIVA-3V to provide initial conditions for the closed-valve simulations. For simulation of diesel combustion process, an integrated KIVA-3V code is developed by incorporating two well-validated models into the standard code: the Shell hydrocarbon auto-ignition model for simulation of diesel auto-ignition under conditions of high temperature and pressure, and the Characteristic-time model for simulation of subsequent diesel combustion. The integrated code is validated and calibrated against experimental pressure measurements in a naturally aspirated direct injection diesel engine. These tools are then used for exploring the potential of a constant-speed, turbocharged diesel engine towards emission reduction. The case study involves combustion simulations for exploring multiple injection strategy for the engine concerned.

21101 高速ディーゼル機関におけるバイオ燃料の燃焼及び排ガス特性(OS11 環境に優しいエンジン技術(2),オーガナイズドセッション)

With regard to global wanning, reduction of carbon dioxide (CO_2) emission is a problem of great urgency. The thermal efficiency of a marine diesel engine is high. Therefore it is difficult to reduce CO_2 emission by improvement of the thermal efficiency. For such a reason, it is realistic to restrain the use of fossil fuel by using bio-fuel (raw vegetable oil, waste cooking oil) as a countermeasure against global warming, hi this paper, we studied on the emission characteristics of the high speed, naturally aspirated, 4 stroke cycle diesel engine using gas oil, marine diesel fuel (MDF), raw rapeseed oil, raw palm oil and waste cooking oil. The followings were found: Emission of CO of bio fuels is higher than that of gas oil or MDF. Smoke of bio fuels is lower than that of gas oil or MDF.

A highly efficient six-stroke internal combustion engine cycle with water injection for in-cylinder exhaust heat recovery

A concept is presented here that adds two additional strokes to the four-stroke Otto or Diesel cycle that has the potential to increase fuel efficiency of the basic cycle. The engine cycle can be thought of as a 4 stroke Otto or Diesel cycle followed by a 2-stroke heat recovery steam cycle. Early exhaust valve closing during the exhaust stroke coupled with water injection are employed to add an additional power stroke at the end of the conventional four-stroke Otto or Diesel cycle. An ideal thermodynamics model of the exhaust gas compression, water injection at top center, and expansion was used to investigate this modification that effectively recovers waste heat from both the engine coolant and combustion exhaust gas. Thus, this concept recovers energy from two waste heat sources of current engine designs and converts heat normally discarded to useable power and work. This concept has the potential of a substantial increase in fuel efficiency over existing conventional internal combustion engines, and under appropriate injected water conditions, increase the fuel efficiency without incurring a decrease in power density. By changing the exhaust valve closing angle during the exhaust stroke, the ideal amount of exhaust can be recompressed for the amountmore » of water injected, thereby minimizing the work input and maximizing the mean effective pressure of the steam expansion stroke (MEPsteam). The value of this exhaust valve closing for maximum MEPsteam depends on the limiting conditions of either one bar or the dew point temperature of the expansion gas/moisture mixture when the exhaust valve opens to discard the spent gas mixture in the sixth stroke. The range of MEPsteam calculated for the geometry of a conventional gasoline spark-ignited internal combustion engine and for plausible water injection parameters is from 0.75 to 2.5 bars. Typical combustion mean effective pressures (MEPcombustion) of naturally aspirated gasoline engines are up to 10 bar, thus this concept has the potential to significantly increase the engine efficiency and fuel economy while not resulting in a decrease in power density.« less

Finite-time thermodynamic modeling and analysis for an irreversible Dual cycle

The performance of an air standard Dual cycle is analyzed by using finite-time thermodynamics. An irreversible Dual cycle model which is more close to practice is established. In the model, the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss computed according to the mean velocity of the piston, the internal irreversibility described by using the compression and expansion efficiencies, and heat transfer loss are considered. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, and the optimal relation between power output and the efficiency of the Dual cycle are derived by detailed numerical examples. Moreover, the effects of internal irreversibility, heat transfer loss, frictional loss and pressure ratio on the cycle performance are analyzed. The power output versus compression ratio and efficiency versus compression ratio curves of the Diesel and Otto cycles are the maximum and minimum envelope lines of the performance of the Dual cycle, respectively. The results obtained herein may provide guidelines for the design of practical internal combustion engines.

A comparative study of GERIPA ethanol with other fuels

The GERIPA project aimed at generating renewable energy integrated with food production has led to a beneficial option for producing ethanol and electricity. Ethanol has economic, social and environmental potential. Considering just the first one, Brazil consumes 39 billion liters per year-LD/yr of diesel oil, 18% of it being imported. The Federal Government has a recovery programme for the soybean agribusiness aimed at soybean biodiesel (SBD) production in which a 10% addition to diesel has been proposed. This 10% involves producing 10.7 million LSBD/d. Soybean biodiesel production is not self-sustainable and such proposal could require an annual subsidy of up to US$1.33 billion. Soybean plantations would need about 10 to 12 times more land than is necessary for sugarcane plantations to produce the same equivalent thermal energy (ETE). Sixty-seven GERIPA projects (GP) producing 80,000 liters of ethanol per day (GP80) could be set up with the sum of US$1.33 billion; this would substitute current Brazilian biodiesel demand by 4.28%, adding the same value for each new subsidiary. Considering ETE, ethanol-GP cost would be 37% to 50% below that for a liter of SBD on account of its raw material (RM) and region. The diesel cycle's thermal efficiency (ηt) yield is around 50% and that of the Otto cycle engine ηt is around 37%. The cost per km driven (CKD) by substituting SBD for ethanol-GP80 would thus indicate an 18% minimum and 59% maximum cost reduction for vehicle engines.

Quantum thermodynamic cycles and quantum heat engines. II.

We study the quantum-mechanical generalization of force or pressure, and then we extend the classical thermodynamic isobaric process to quantum-mechanical systems. Based on these efforts, we are able to study the quantum version of thermodynamic cycles that consist of quantum isobaric processes, such as the quantum Brayton cycle and quantum Diesel cycle. We also consider the implementation of the quantum Brayton cycle and quantum Diesel cycle with some model systems, such as single particle in a one-dimensional box and single-mode radiation field in a cavity. These studies lay the microscopic (quantum-mechanical) foundation for Szilard-Zurek single-molecule engine.

Homogeneous charge compression ignition of hydrogen in a single-cylinder diesel engine

Homogeneous charge compression ignition (HCCI) of hydrogen was studied using a single-zone model based in chemical reaction kinetics and using a single-cylinder Cooperative Fuels Research (CFR) diesel engine. Comparison was made with conventional diesel combustion at the same compression ratio and load. Simulation indicated that hydrogen HCCI should be feasible at compression ratios around 18 with intake heating to 100 °C, with peak efficiency occurring for moderately dilute equivalence ratios (0.2–0.5) with the minimum possible amount of intake heating. Experimental hydrogen HCCI was achieved with intake heating to 80 °C and 100 °C for equivalence ratios between 0.15 and 0.37. Hydrogen HCCI exhibited unburned hydrogen emissions of the order of 0.5–1.0 per cent, corresponding to combustion efficiencies of 90–95 per cent. Emissions of nitric oxides were typically below 1 ppm and were at least two orders of magnitude lower than a comparable diesel cycle. Efficiency of hydrogen HCCI was lower than a comparable diesel cycle owing primarily to higher thermal losses and higher chemical enthalpy losses (lower combustion efficiency). These losses are hypothesized to depend strongly on surface area—volume ratio, and methods of mitigating these losses suggest how an engine could be designed to employ hydrogen HCCI.