Experimental study of combustion noise radiation during transient turbocharged diesel engine operation

Diesel engine noise radiation has drawn increased attention in recent years since it is associated with the passengers’ and pedestrians’ discomfort, a fact that has been acknowledged by the manufacturers and the legislation in many countries. In the current study, experimental tests were conducted on a truck, turbocharged diesel engine in order to investigate the mechanism of combustion noise emission under various transient schedules experienced during daily driving conditions, namely acceleration and load increase. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events. Analytical diagrams are provided to explain the behavior of combustion noise radiation in conjunction with cylinder pressure (spectrum), turbocharger and governor/fuel pump response. Turbocharger lag was found to be the main cause for the noise spikes during all test cases examined, with the engine injection timing calibration and the slow adjustment of cylinder wall temperature to the new fueling conditions playing a vital role. The analysis was extended with a quasi-steady approximation of transient combustion noise using steady-state maps, in order to better highlight the effect of dynamic engine operation on combustion noise emissions.     

Comparative study of turbocharged diesel engine emissions during three different Transient Cycles

Starting from the 1980s (diesel‐engined) vehicles have been tested for exhaust emissions, prior to type approval, using sophisticated standardized transient tests (Transient Cycles). These are usually characterized by long duration consisting of both speed and load changes under varying operating schedules. In the present work, a fast and, relatively, easy to apply approach was developed in order to be able to make a first approximation of the engine performance and emissions during a speed/torque vs time Transient Cycle. The procedure is based on a previous steady‐state experimental investigation of the engine for the formulation of polynomial expressions of all interesting engine properties with respect to engine speed and torque. Correction coefficients are then applied, based on experiments conducted on the engine under study, to account for transient discrepancies. Using the developed algorithm, a comparative study was conducted for the European, American and the Worldwide heavy‐duty Transient Cycles. It was revealed for the current engine that the European ETC, being the most aggressive and having the shortest idling period, is also the most demanding in terms of absolute emissions (g), particularly soot. At the same time, the importance of abrupt transients (primarily experienced during urban driving) on engine emissions was highlighted. A comparative analysis was also performed that detailed the individual technical and transient characteristics of each cycle. Copyright © 2009 John Wiley & Sons, Ltd.     

Lubricating oil effects on the transient performance of a turbocharged diesel engine

The modeling of transient turbocharged diesel engine operation appeared in the early seventies and continues to be in the focal point of research, due to the importance of transient response in the everyday operating conditions of engines. The majority of research has focused so far on issues concerning thermodynamic modeling, as these directly affect performance and pollutants' emissions. On the other hand, issues concerning the dynamics of transient operation are usually over-simplified, possibly for the sake of speeding up program execution time. In the present work, an experimentally validated transient diesel engine simulation code is used to study and evaluate the importance of the lubricating oil properties (oil-type, viscosity, temperature) on the transient response of a turbocharged diesel engine. It is revealed how the lubricating oil affects mechanical friction and hence, the speed response as well as the other interesting parameters, e.g. fuel pump rack position or turbocharger operating point for load-change schedules typical in the European Transient Cycles for heavy-duty engines. Particularly under low ambient conditions, the high oil viscosity is responsible for a significant increase in the respective frictional losses worsening the engine transient response.     

Comparative second-law analysis of internal combustion engine operation for methane,methanol, and dodecane fuels

A method for both combustion irreversibility and working medium availability computations in a high-speed, naturally-aspirated, four-stroke, internal combustion engine cylinder is presented. The results of the second-law analysis of engine operation with n-dodecane (n-C₁₂H₂₆) fuel are compared with the results of a similar analysis for cases where a light, gaseous (CH₄) and an oxygenated (CH₃OH) fuel is used. The rate of entropy production during combustion is analytically calculated as a function of the fuel reaction rate with the combined use of first- and second-law arguments and a chemical equilibrium hypothesis. It is shown theoretically that the decomposition of lighter molecules leads to less entropy generation compared to heavier fuels. This is verified computationally for the particular fuels and the corresponding decrease in combustion irreversibility is calculated. Special reference is made to the effect of the lower mixing entropy of the exhaust gas of an oxygenated fuel (CH₃OH) as a contribution to the discussion of the advantages and disadvantages of the use of such fuels.     

柴油机瞬时转速的建模及仿真研究

通过利用等效圆盘等效轴法建立了两自由度的柴油机瞬时转速模型,并对其进行了仿真计算,由此得到了柴油机空车不同转速下和柴油机转速为1500r/min、不同负荷工况下的仿真结果,较为精确地揭示了瞬时转速的变化规律,为利用瞬时转速对柴油机进行状态监测以及故障诊断提供理论上的基础。     

Experimental and simulation analysis of the transient operation of a turbocharged multi-cylinder IDI diesel engine

An experimental and theoretical analysis is carried out to study the response of a multi-cylinder, turbocharged, IDI (indirect injection) compression ignition engine, under transient operating conditions. To this aim, a comprehensive digital computer model is developed which solves the governing differential equations individually for each cylinder, providing thus increased accuracy over previous ‘single-cylinder’ simulations. Special attention has been paid for diversifying the transient operation from the steady-state one, providing improved or even new relations concerning combustion, heat transfer to the cylinder walls, friction, turbocharger and aftercooler operation, and dynamic analysis for the transient case. An extended steady state and transient experimental work is conducted on a specially developed engine test bed configuration, located at the authors' laboratory, which is connected to a high-speed data acquisition and processing system. The steady-state measurements are used for the calibration of the individual submodel constants. The transient investigation includes both speed and load changes operating schedules. During each transient test four major measurements are continuously made, i.e. engine speed, fuel pump rack position, main chamber pressure and turbocharger compressor boost pressure. The hydraulic brake coupled to the engine possesses a high mass moment of inertia and long nonlinear load-change times, which together with the indirect injection nature of the engine are important challenges for the simulation code. Explicit multiple diagrams are given to describe the engine and turbocharger transient behaviour including smoke predictions. The agreement between experimental and predicted responses is satisfactory, for all the cases examined, proving the validity of the simulation process, while providing useful information for the engine response under various transient operations. © 1998 John Wiley & Sons, Ltd.     

Study of diesel engine performance and emissions during a Transient Cycle applying an engine mapping-based methodology

An engine mapping-based methodology was developed in order to be able to make a first approximation of the engine performance and emissions during a speed/torque vs. time Transient Cycle. The procedure is based on a previous steady-state experimental investigation of the engine for the formulation of polynomial expressions of all interesting engine properties with respect to engine speed and torque. Correction coefficients are then applied to account for transient discrepancies based on individual transient experiments. The developed algorithm was applied for the case of a heavy-duty diesel engine running on the European Transient Cycle. A comparative analysis was performed for each section of the Cycle, which revealed that the first part (urban driving) is responsible for the biggest amount of emissions (in g) owing to the most frequent and abrupt load changes involved. The obvious advantage of the proposed methodology is the fact that the effect of internal or external (after-treatment) measures can be easily incorporated in the code and quantified in terms of emissions improvement.     

Performance analysis and parametric study of a solid oxide fuel cell fueled by carbon monoxide

A theoretical model of the solid oxide fuel cell (SOFC) fueled by carbon monoxide is adopted and validated, in which the activation overpotential, concentration overpotential, and ohmic overpotential are regarded as the main sources of voltage losses. Based on the thermodynamic-electrochemical analysis, mathematical expressions of some performance parameters such as the cell potential, power output, efficiency, and entropy production rate are derived. The effects of microstructure parameters such as the electrode porosity, tortuosity, pore size, grain size, etc. on the electrochemical performance characteristics of the SOFC are revealed. Moreover, the effects of some operation conditions such as the current density, anode inlet gas molar fraction, operating temperature, and operating pressure on some important performance parameters of the SOFC are also discussed. It is found that there exist some optimal values of microstructure parameters and operating conditions at which the better performance can be expected. The results obtained in the paper may provide some theoretical guidance for the design and operation of practical SOFCs fueled by coal-derived gases.     

A parametric study of the direct formic acid fuel cell (DFAFC) performance and fuel crossover

The effect of formic acid concentration (2–20 M), operating temperature (30–70 °C), and relative humidity (RH 40–90%) on the direct formic acid fuel cell (DFAFC) performance and fuel crossover were studied. In addition, air and oxygen were used to investigate the effect of oxidant flow rate on DFAFC performance and fuel crossover by operating the DFAFC under three modes of reactant supply: passive, semi passive (oxidant supplied), and active (both oxidant and fuel supplied). Fuel crossover was determined by measuring the percentage of exhausted carbon dioxide (CO₂) at the cathode using a CO₂ analyzer, from which the equivalent formic acid crossover flux was calculated. The results indicate that the DFAFC performance and fuel crossover were affected by formic acid concentration, temperature, humidity, oxidant flow rate, and the mode of operation. Optimums of these operating parameters were established for obtaining high performance of the DFAFC. The relationships between these parameters and the performance and fuel crossover of the DFAFC are discussed in this paper.     

Evaluation of a spark ignition engine cycle using first and second law analysis techniques

In the present work, a simulation model of the actual processes occurring during the thermodynamic cycle of a real spark ignition engine is developed. The model incorporates such important features as heat exchange of the cylinder gases with the chamber walls (during all phases), real spark ignition timings, real valve opening and closing timings, accurate simulation of the spherical flame front movement issuing from the spark plug and calculation of eight chemical species concentration during combustion, at every engine degree crank angle. The results from this first law analysis of the real cycle (for example pressure indicator diagrams, efficiencies) are compared favourably with the relevant experimental results obtained from a flexible, variable compression ratio, Ricardo E-6 spark ignition engine, located at the author's laboratory, forming thus a sound basis for moving towards a second law evaluation of this cycle. The thermodynamic state points, determined from the first law analysis, are used to determine the availability (second law analysis) at each engine crank angle and so lead to the effectiveness computation, as well as to the revelation of the magnitude of the work-potential lost during the various processes in a much more realistic way than the first law analysis can. The second law analysis results, for the actual engine in hand, are compared with the up-to-now existing ideal cycle Otto engine results. Also, a second law parametric investigation is performed over a wide range of design and operation conditions (compression ratio, fuel-air ratio, ignition advance), providing useful information for the cycle processes performance assessment by bringing state degradations and thermodynamic losses into perspective.     

Exhaust emissions of diesel engines operating under transient conditions with biodiesel fuel blends

The transient operation of turbocharged diesel engines can prove quite demanding in terms of engine response, systems reliability and exhaust emissions. It is a daily encountered situation that drastically differentiates the engine operation from the respective steady-state conditions, requiring careful and detailed study and experimentation. On the other hand, depleting reserves and growing prices of crude oil, as well as gradually stricter emission regulations and greenhouse gas concerns have led to an ever-increasing effort to develop alternative fuel sources, with particular emphasis on biofuels that possess the added benefit of being renewable. In this regard, and particularly for the transport sector, biodiesel has emerged as a very promising solution.     

SOFC cogeneration system for building applications, part 1: Development of SOFC system-level model and the parametric study

A thermal and electrochemical model is developed for the simulation of Solid Oxide Fuel Cell (SOFC) cogeneration system in this study. The modeling algorithms of electrochemical and thermal models are described. Since the fuel cell stack itself is only a single component within the whole SOFC system, the modeling of the balance-of-plant (BOP) components is also performed to assess the system-level performance. Using the new model, a parametric analysis is carried out to investigate the effects of fuel flow rate, extent of methane gas pre-reforming, fuel utilization factor, recycling rate of cathode gas and cell voltage on the overall system performance. As a result of the parametric study, fuel flow rate, cell voltage, fuel utilization and recycling rate of cathode gas turned out to improve system power output. In addition, the internal reforming turned out to have advantage over external reforming in terms of system power supply.     

Computer modeling and parametric study of a double effect generation absorption refrigeration cycle

This paper presents as assessment based on steady-state thermodynamic analysis and computer modeling of a double effect generation absorption refrigeration cycle for solar air-conditioning. The system consists of a second effect generator between the generator and condenser of the single effect absorption cycle and two solution heat exchangers between the absorber and the two generators. A numerical computer modeling of a water LiBr system based on the solution of simultaneous heat, mass and material balance equations for various components of the system has been carried out. The influences of component temperatures and heat exchanger effectiveness on the cooling coefficients of performance and component heat transfer rates have been investigated to obtain optimum operating conditions for the proposed air-conditioning system. Further, the single and double effect absorption cycles are compared with each other as well as with an ideal absorption cycle operating over the same range of temperatures.     

Modeling and parametric study of a 1 kWe HT-PEMFC-based residential micro-CHP system

A detailed thermodynamic, kinetic and geometric model of a micro-CHP (Combined-Heat-and-Power) residential system based on High Temperature-Proton Exchange Membrane Fuel Cell (HT-PEMFC) technology is developed, implemented and validated. HT-PEMFC technology is investigated as a possible candidate for fuel cell-based residential micro-CHP systems, since it can operate at higher temperature than Nafion-based fuel cells, and therefore can reach higher cogeneration efficiencies. The proposed system can provide electric power, hot water, and space heating for a typical Danish single-family household. A complete fuel processing subsystem, with all necessary balance-of-plant components, is modeled and coupled to the fuel cell stack subsystem. The micro-CHP system’s synthesis/design and operational pattern is analyzed by means of a parametric study. The parametric study is conducted to determine the most viable system/component design based on maximizing total system efficiency, without violating the requirements of the system. Four decision variables (steam-to-carbon ratio, fuel cell operating temperature, combustor temperature and hydrogen stoichiometry) were parameterized within feasible limits to provide insight on their effect on the overall performance of the proposed system under study and also to provide input on more efficient design in the future. The system is designed to provide maximum loads of 1 kW_e and 2 kW_th. A sensitivity analysis is applied to investigate the influence of the most important parameters on the simulated performance of the system.     

基于多体动力学的柴油机动力学性能研究

基于多体动力学原理,对某型号柴油机的动力学性能进行研究,建立以曲轴和机体为柔性体,缸盖、连杆等为刚性体的刚柔耦合动力学模型。在柴油机各个部件之间根据实际运动关系建立约束,进行曲轴、机体的模态分析与整机的振动分析与模态分析,并对柴油机的振动特性给出总体评价。     

基于UG/WAVE的柴油机连杆组自顶向下参数化设计

介绍了传统零件设计的缺陷和UG/WAVE的优点,并利用UG/WAVE技术以及参数化建模思想对某柴油机连杆组件进行了自顶向下参数化设计,减少了设计更新及等待的时间,提高了产品的市场竞争能力。     

Investigating the emissions during acceleration of a turbocharged diesel engine operating with bio-diesel or n-butanol diesel fuel blends

Control of transient emissions from turbocharged diesel engines is an important objective for automotive manufacturers, since stringent criteria for exhaust emission levels must be met as dictated by the legislated transient cycles. On the other hand, bio-fuels are getting impetus today as renewable substitutes for conventional fuels (diesel fuel or gasoline), especially in the transport domain. In the present work, experimental tests are conducted on a turbocharged truck diesel engine in order to investigate the formation mechanism of NO (nitric oxide) and smoke under various accelerating schedules experienced during daily driving conditions. To this aim, a fully instrumented test bed was set up in order to capture the development of key engine and turbocharger variables during the transient events using ultra-fast response instrumentation for the instantaneous measurement of the exhaust NO and smoke opacity. Apart from the baseline diesel fuel, the engine was operated with a blend of diesel fuel with 30% bio-diesel, and a blend of diesel fuel with 25% n-butanol. Analytical diagrams are provided to explain the behavior of emissions development in conjunction with turbocharger and fueling response. Unsurprisingly, turbocharger lag was found to be the main culprit for the emissions spikes during all test cases examined. The differences in the measured exhaust emissions of the two bio-fuel/diesel fuel blends, both leading to serious smoke reductions but also NO increases compared with the baseline operation of the engine were determined and compared. The differing physical and chemical properties of bio-diesel and n-butanol against those of the diesel fuel, together with the formation mechanisms of NO and soot were used for the analysis and interpretation of the experimental findings concerning transient emissions.     

Thermodynamic analysis,parametric study and optimum operation of the Kalina cycle

The work described here has a major objectives the complete thermodynamic analysis and the parametric study of the Kalina Power Unit. The device layout optimization is based on the presentation of the unit on the T-h and h/T-s thermodynamic charts. The operation of the power unit is simulated by the use of equations describing the thermodynamic behaviour of the NH₃/H₂O mixture. The important parameters of the unit, i.e. high, medium and low pressures/rich, weak, working solution and boiler vapour mass fraction are discussed and related. Correlations are developed which describe the optimum operation of the Kalina cycle. The maximum thermal efficiency, the heat required to drive the unit and the work produced may be directly calculated from analytical functions in terms of the ambient temperature and the low pressure of the units. The maximum theoretical efficiency ranges from 42·7% to 46·6%.     

Hydrogen enrichment effects on the second law analysis of natural and landfill gas combustion in engine cylinders

The availability (exergy) balance during combustion of hydrogen-enriched natural and landfill gas, which are used as fuels in combustion engine cylinders, is studied computationally using a zero-dimensional model of the closed part of the cycle. The main focus is on the demonstration of a fundamental difference in the generation of irreversibility during combustion between hydrogen and hydrocarbons. This difference relates to the mechanisms of entropy generation during the oxidation reaction of the two fuels and yields the particularly attractive characteristic of a monotonic decrease in combustion irreversibility with increasing hydrogen content of the fuel, for mole fractions of hydrogen smaller than 10%. This reduction in combustion irreversibility is reflected in an increase in second law efficiency with increasing proportions of hydrogen. The exhaust gas availability at the end of the closed part of the cycle was found to have a local maximum for a hydrogen mole fraction of the order of 5%. These trends with respect to hydrogen also apply when the fuel is diluted with a significant amount of CO₂ (of the order of 40%, as for example in the case for landfill gas), although the absolute value of each of the terms of the availability balance is affected strongly by the dilution.     

Experimental and numerical study on the combustion limiting characteristics and design margin of a marine diesel engine

In this paper, a working-process simulation model was established, and the characteristics regarding the diesel engine maximum output power were analyzed under different limiting parameters. The design margin of the marine diesel engine is obtained through numerical and experimental study. Then, the simulation model and single cylinder diesel engine test were used to investigate the theoretical determination method of limiting characteristic lines and design margin area. It can be found that using least-square method to fit the calculation results can achieve quantitative analysis of limiting characteristics, and then the design margin area can be confirmed. The analysis results show that the maximum output power of the diesel engine is limited by in-cylinder pressure, turbine speed and exhaust temperature. The limiting parameters of maximum output power are different at different speeds, and the trend with speed of maximum output power are also different under different limiting parameters. Furthermore, the analysis of the operating area shows that the margin of the marine diesel engine at rated speed is about 27%, and there is a large design margin when operating at high speed.