Diagnosis methodology for the turbocharger groups installed on a 1 MW internal combustion engine

The issue of internal combustion engine (ICE) diagnosis attracts great interest because modern engines need continual control of the operational status, in order to obtain high efficiency in energy conversion and accurate control of the polluting emissions. In particular, in reference to an alternative ICE of 1 MW, the present study relates the development, through the design of neural simulators, of the turbocharger maps to reproduce the operational states characterized by new&clean conditions and allowing the evaluation of particular “health state” indices of such a module. In detail, after an experimental campaign, turbocharger fundamental characteristics referred to new&clean conditions, such as the compressor isoentropic efficiency and the mass flow elaborated by the turbine, were evaluated at different operation conditions of the alternative ICE Subsequently, the neural simulators were developed through the training and test of different neural architectures.     

Cylinders diagnosis system of a 1 MW internal combustion engine through vibrational signal processing using DWT technique

In the present study an innovative diagnostic system of the combustion process, developed especially for cogenerative reciprocating engines, is introduced. This work is part of a more wide research activity, dedicated to the development of diagnostic systems for energy plants. This system is based on the evaluation of the energy content of the vibration signal directly acquired on the cylinders head through the Discrete Wavelet Transform technique and the Parseval’s theorem. The system development and its test took place alongside a consistent maintenance work that has allowed to distinguish between different engine operative functioning, and, in particular, between good and bad conditions of the combustion chambers. Then, starting from the obtained results, a diagnostic system has been developed, basing on the acquired vibration signals and the operative engine load, in order to formulate for each cylinder a judgment about the quality of the combustion process.     

Modeling of internal combustion engine based cogeneration systems for residential applications

A parametric model that can be used in the design and techno-economic evaluation of internal combustion engine (ICE) based cogeneration systems for residential use is presented. The model, which is suitable to be incorporated into a building simulation program, includes sub-models for internal combustion engines and generators, electrical/thermal storage systems, and secondary system components (e.g. controllers), and is capable of simulating the performance of these systems in 15-min time steps. Water storage tanks for thermal storage and electrochemical (battery) systems for electrical storage are modeled. The parametric model provides users with useful information about the cogeneration system performance in response to a building’s electrical and thermal demands. This paper presents the model, and the results of sensitivity analyses obtained using the model with a building simulation program. The results demonstrate the capabilities of the model and provide an insight into the energetic performance of ICE based cogeneration systems.     

Process analysis of 1 MW MCFC plant

Molten carbonate fuel cells (MCFCs) have received a great deal of attention in recent years and are now at a pre-commercial stage.     

Design of the measurements validation procedure and the expert system architecture for a cogeneration internal combustion engine

A research activity has been initiated to study the development of a diagnostic methodology, for the optimization of energy efficiency and the maximization of the operational time in those conditions, based on artificial intelligence (AI) techniques such as artificial neural network (ANN) and fuzzy logic.The diagnostic procedure, developed specifically for the cogeneration plant located at the Engineering Department of the University of Perugia, must be characterized by a modular architecture to obtain a flexible architecture applicable to different systems. The first part of the study deals with the identifying the principal modules and the corresponding variables necessary to evaluate the module “health state”.Also the consequent upgrade of the monitoring system is described in this paper. Moreover it describes the structure proposed for the diagnostic procedure, consisting of a procedure for measurement validation and a fuzzy logic-based inference system. The first reveals the presence of abnormal conditions and localizes their source distinguishing between system failure and instrumentation malfunctions. The second provides an evaluation of module health state and the classification of the failures which have possibly occurred. The procedure was implemented in C++.     

An onboard hydrogen generator for hydrogen enhanced combustion with internal combustion engine

Hydrogen enhanced combustion (HEC) for internal combustion engine is known to be a simple mean for improving engine efficiency in fuel saving and cleaner exhaust. An onboard compact and high efficient methanol steam reformer is made and installed in the tailpipe of a vehicle to produce hydrogen continuously onboard by using the waste heat of the engine for heating up the reformer; this provides a practical device for the HEC to become a reality. This use of waste heat from engine enables an extremely high process efficiency of 113% to convert methanol (8.68 MJ) for 1.0 NM of hydrogen (9.83 MJ) and low cost of using hydrogen as an enhancer or as a fuel itself. The test results of HEC from the onboard hydrogen production are presented with 2 gasoline engine vehicles and 2 diesel engines; the results indicate a hike of engine efficiency in 15–25% fuel saving and a 40–50% pollutants reduction including 70% reduction of exhaust smoke. The use of hydrogen as an enhancer brings about 2–3 fold of net reductions in energy, carbon dioxide emission and fuel cost expense over the input of methanol feed for hydrogen production.     

Modeling Study of a New Circulating Fluidized Bi—Bed Boiler Combustion System

INTRODUCTIONThecirculatingfluidizedbed(CFB)boileriscurrentlybeingactivelydevelopedinChina.AnalysisofthecharacteristicsofCFBismadetoeffectivelydesign,operateandcontroltheCFB.Mechanismanalysisandaccumulatedexperiencewereusedtodevelopasetofgeneraldynami...     

Production function of a simple model internal combustion engine

The paper deals with an analysis in terms of production function of a simplified Beau de Rochas irreversible engine. The combustion reaction is the main source of irreversibility. The production function is concave. This property is an extension of similar behaviours for endoreversible heat engines.     

内燃机进气流动数值计算中三维几何建模问题的探讨

本文主要对内燃机进气流动数值计算中的三维几何建模的方法进行了探讨，并针对进气道稳流试验台的仿真计算提出了几种几何模型，计算结果与试验数据进行了比较，分析了各模型的计算误差，表明三维简化几何模型的结构对计算精度有较大影响。     

Performance analysis of a novel eco‐friendly internal combustion engine cycle

The Miller cycle applications have been performed to diminish NO_x released from internal combustion engines (ICEs), in recent years. The Miller cycle provides decreased compression ratio and enhanced expansion ratio; hereby, maximum in‐cylinder combustion temperatures diminish, and NO_x formations slow down remarkably. Another less‐known method is Takemura cycle application, which provides heat addition into engine cylinder at constant combustion temperatures. In this study, a novel cycle including the Miller cycle and the Takemura cycle has been developed by using novel numerical models and computing methods with seven processes and a novel way to decrease NO_x emissions at higher levels compared with the single applications of known cycles. A comprehensive performance examination of the proposed cycle engine in terms of performance characteristics such as effective power (EFP), effective power density (EFPD), exergy destruction (X), exergy efficiency (ε), and ecological coefficient of performance (ECOP) has been conducted. The impacts of engine operating and design parameters on the performance characteristics have been computationally examined. Furthermore, irreversibilities depending on incomplete combustion loss (INCL), exhaust output loss (EXOL), heat transfer loss (HTRL), and friction loss (FRL) have been considered in the performance simulations. The minimum exergy destruction and maximum performance specifications have been observed with 30 of the compression ratio. Maximum effective power values have been obtained at range between 1 and 1.2 of equivalence ratio. The optimum range for exergy efficiency is between 0.8 and 1 of equivalence ratio. Increasing engine speed has provided enhancing effective power. However, an optimum range has been found for the exergy efficiency that is interval of 3000 to 4000 rpm. The results obtained can be assessed by researchers studying on modeling of the engine systems and designs.     

Modeling of the non-uniform combustion in a scramjet engine

Due to the high-speed of the air stream, the scramjet combustion is neither uniform nor complete. An empirical fuel distribution model is developed to describe non-uniform combustion for scramjet engines. The combustor is subdivided into different regions by radius with different local equivalence ratios. The conservation equations of the regions for the combustion and exhaust expansion are computed independently. The results indicate that scramjet thrust is more related to the fuel equivalence ratio and combustion efficiency. If the combustion efficiency is 100% and the fuel equivalence ratio is constant, there is no obvious effect of different fuel distribution to the engine except for the exhaust parameter distribution. It is also revealed that the sum of isolator shock loss and combustor Rayleigh loss is nearly constant under the same isolate cross-sectional area. Lower isolator inlet Mach is benefit to the thrust performance and the best thrust performance is at the thermal choking boundary. When the isolator inlet Mach increases, the thrust decreases.     

Fuzzy control of a bio-hydrogen internal combustion engine generating system

This study proposes a fuzzy control bio-hydrogen internal combustion engine (ICE) generating system. The ICE technology is composed of thermodynamics, mechanical engineering, hydrodynamics, and electrical engineering. Bio-hydrogen can provide clean and efficient power instead of conventional fuels applied in an ICE. The two critical cores of hydrogen ICE generator are ignition time control which can precisely ignite air-fuel mixtures to make generator output stable power and air-fuel ratio control which can adjust output power to satisfy load demand. Fuzzy logic can provide precise control and response fast within various air-fuel ratios.The study establishes a fuzzy control system with an output generator and an ICE with solenoid valve that controls bio-hydrogen injection. The experimental system successfully output stable power and carried out parameters of bio-hydrogen flow rate, air-fuel ratio, injection pressure, and ignition timing. Parameters and experimental data are analyzed in the study and can be references for future development of the bio-hydrogen internal combustion engine generating system.     

内燃机薄壁气缸套的加固测量法

作者介绍一种通过改变薄壁气缸套支承形式，再用常规量具来测量薄壁气缸套内外径的方法。并对由量具和支承的作用力所引起的变形量进行了分析和计算。     

Investigation of fuel lean reburning process in a 1.5 MW boiler

This paper examines a detailed study of fuel lean reburning process applied to a 1.5 MW gas-fired boiler. Experimental and numerical studies were carried out to investigate the effect of the fuel lean reburning process on the NO_X reduction and CO emission. Natural gas (CH₄) was used as the reburn as well as the main fuel. The amount of the reburn fuel, injection location and thermal load of boiler were considered as experimental parameters. The flue gas data revealed that the fuel lean reburning process led to NO_X reduction up to 43%, while CO emission was limited to less than 30 ppm for the 100% thermal load condition. The commercial computational fluid dynamics code FLUENT 6.3, which included turbulence, chemical reaction, radiation and NO modeling, was used to predict the fluid flow and heat transfer characteristics under various operational conditions in the boiler. Subsequently, predicted results were validated with available measured data such as gas temperature distributions and local mean NO_X concentrations. The detailed numerical results showed that the recirculation flow developed inside the boiler was found to play an important role in improving the effectiveness of fuel lean reburning process.     

First-principles based microkinetic modeling of borohydride oxidation on a Au(1 1 1) electrode

Borohydride oxidation electrokinetics over the Au(1 1 1) surface are simulated using first-principles determined elementary rate constants and a microkinetic model. A method to approximate the potential dependent elementary step activation barriers based on density functional theory calculations is developed and applied to the minimum energy path for borohydride oxidation. Activation barriers of the equivalent non-electrochemical reactions are calculated and made potential dependent using the Butler-Volmer equation. The kinetic controlled region of the borohydride oxidation reaction linear sweep voltammogram over the Au(1 1 1) surface is simulated. The simulation results suggest that B-H bond containing species are stable surface intermediates at potentials where an oxidation current is observed. The predicted rate is most sensitive to the symmetry factor and the BH₂OH dissociation barrier. Surface-enhanced Raman spectroscopy confirms the presence of BH₃ as a stable intermediate.     

Energy and exergy analysis of a turbocharged hydrogen internal combustion engine

This paper has analyzed the energy and exergy distribution of a 2.3 L turbocharged hydrogen engine by mapping characteristics experiment. The energy loss during fuel energy conversion mainly includes: exhaust energy (23.5–34.7%), cooling medium (coolant and oil) energy (21.3–34.8%), intercooler energy (0.5–3.6%) and uncounted energy (5.8–14.1%), while the proportion of effective work ranges from 25.7% to 35.1%. Results show that all kinds of energies increase with engine speeds and they are not sensitive to the loads. However, the proportions of different kind of energy exhibit different characteristics. Moreover, the turbocharger can increase the brake thermal efficiency and the maximum can be increased by 4.8%. Exergy analysis shows exergy efficiency of the coolant energy does not exceed 5%, while the exergy efficiency of the exhaust energy can reach up to 23%. And the total hydrogen fuel thermal efficiency limit is theoretically above 59%.     

Backfire control and power enhancement of a hydrogen internal combustion engine

Frequent backfire can occur in inlet port fuel injection hydrogen internal combustion engines (HICEs) when the equivalence fuel–air ratio is larger than 0.56, thus limiting further enhancement of engine power. Thus, to control backfire, an inlet port fuel injection HICE test system and a computational fluid dynamics model are established to explore the factors that cause backfire under high loads. The temperature and the concentration of the gas mixture near the intake valves are among the essential factors that result in backfire. Optimizing the timing and pressure of hydrogen injection reduces the concentration distribution of the intake mixture and the temperature of the high-concentration mixture through the inlet valve, thus allowing control of backfire. Controlling backfire enables a HICE to work normally at high equivalence fuel–air ratio (even beyond 1.0). A HICE with optimized hydrogen injection timing and pressure demonstrates significant enhancement of the power output.     

Experimental investigation of combustion characteristics and NOx emission of a turbocharged hydrogen internal combustion engine

In order to alleviate the contradictions of increasingly prominent environmental pollution, greenhouse gas emissions and oil resource security issues, the search for renewable and clean alternative energy sources is getting more and more attention. Hydrogen energy is known as a future energy source because of its safety, reliability, wide range of resources and non-polluting products. Hydrogen internal combustion engine combines the technical advantages of traditional internal combustion engines and has comprehensive comparative advantages in terms of manufacturing cost, fuel adaptability and reliability. It is one of the practical ways to realize hydrogen energy utilization. In this paper, the combustion characteristics and NOx emission of a turbocharged hydrogen engine were investigated using the test data. The results showed the combustion duration (the crank angle of 10%–90% fuel burned) at 1500 rpm and 2000 rpm was equal and the combustion duration is much bigger than the other loads when the BMEP is 0.27 MPa. The reason is the effect of the turbocharger on the gas exchange process, which will influence the combustion process. The cylinder pressure and pressure rise rate were also investigated and the peak pressure rise rate was lower than 0.25 MPa/°CA at all working conditions. Moreover, the NOx emission changed from 300 ppm to 1200 ppm with engine speed increasing and the maximum value can reach to 7000 ppm when the equivalence ratio is 0.88 at 2500 rpm, maximum brake torque. The NOx emission shows different changing tendencies with different working conditions. Finally, these conclusions can be used to develop controlling strategies to solve the contradictions among power, brake thermal efficiency and NOx emission for the turbocharged hydrogen internal combustion engines.     

Evaluation of Tafel-Volmer kinetic parameters for the hydrogen oxidation reaction on Pt(1 1 0) electrodes

Modelling of PEM fuel cells has long been an active research area to improve understanding of cell and stack operation, facilitate design improvements and support simulation studies. The prediction of activation polarization in most PEM models has concentrated on the cathode losses since anode losses are commonly much smaller and tend to be ignored. Further development of the anode activation polarization term is being undertaken to broaden the application and usefulness of PEM models in general.Published work on the kinetics of the hydrogen oxidation reaction (HOR) using Pt(h k l) electrodes in dilute H₂SO₄ has been recently reassessed and published. Correlations for diffusion-free exchange current densities were developed and empirical predictive equations for the anode activation polarization were proposed for the experimental conditions of the previously published work: Pt(1 0 0), Pt(1 1 0) and Pt(1 1 1) electrodes, pH₂ of 1 atm, and temperatures of 1, 30 and 60 °C. It was concluded that the HOR on Pt(1 1 0) electrodes followed a Tafel-Volmer reaction sequence.The aim of the present paper is to generalize these Tafel-Volmer correlations, apply them to published data for Pt(1 1 0) electrodes and further develop the modelling of anode activation polarization over the range of operating conditions found in PEMFC operation.     

1000 MW核电汽轮机转子扭转刚度模化分析

针对核电汽轮机转子扭振特性的模化分析,综合考虑焊接转子轮盘的复杂结构,通过应变能法计算了一系列无量纲参数下2种典型轮盘简化模型的扭转刚度,归纳得到了2种典型轮盘简化模型的扭转刚度计算方法。典型的计算例子表明文章提出的模化方法在分析轴系扭转振动特性问题上具有较高的精度和效率。