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 a 1 MW cogenerative internal combustion engine for diagnostic scopes

This paper contributes to the development of a thermo-dynamic model of the 1 MW cogenerative internal combustion engine (I.C.E.), including also an artificial neural network simulator of the electronic control module. Such a study is part of a more wide research activity, concerning the development of a diagnosis and monitoring system specifically for power plants. In particular, the engine model was realized to simulate the engine functioning also in the case of malfunctions and failures occurrence, taking in consideration the compensation effect operated by the regulation system.     

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++.     

Diagnosis and control of abnormal combustion of hydrogen internal combustion engine based on the hydrogen injection parameters

In order to improve the limitation of evaluating the abnormal combustion problem of hydrogen internal combustion engine by single index, the abnormal combustion risk coefficient is proposed and defined based on AHP(Analytic Hierarchy Process)-entropy method. The abnormal combustion risk of PFI hydrogen internal combustion engine is comprehensively evaluated from multiple indexes such as the uniformity coefficient of the mixture, the temperature of the hot area, the maximum temperature rise rate, the residual amount of hydrogen in the intake port and the cylinder temperature at the end of the exhaust. The influence of hydrogen injection parameters on abnormal combustion was explored. The results show that the temperature and the maximum temperature rise rate in the hot area decrease first and then increase with the increase of hydrogen injection angle and hydrogen injection flow rate. Although large hydrogen injection angle and hydrogen injection flow rate can reduce the cylinder temperature at the end of exhaust, they will increase the residual hydrogen amount in the intake port. Appropriate hydrogen injection angle and hydrogen injection flow scheme can ensure that all parameters are at a better level, so that the risk coefficient of abnormal combustion decreases by 2.1%–5.5%, and the possibility of abnormal combustion is reduced.     

Optimization of a 50 MW bubbling fluidized bed biomass combustion chamber by means of computational particle fluid dynamics

An efficient utilization of biomass fuels in power plants is often limited by the melting behavior of the biomass ash, which causes unplanned shutdowns of the plants. If the melting temperature of the ash is locally exceeded, deposits can form on the walls of the combustion chamber. In this paper, a bubbling fluidized bed combustion chamber with 50 MW biomass input is investigated that severely suffers deposit build-up in the freeboard during operation. The deposit layers affect the operation negatively in two ways: they act as an additional heat resistance in regions of heat extraction, and they can come off the wall and fall into the bed and negatively influence the fluidization behavior. To detect zones where ash melting can occur, the temperature distribution in the combustion chamber is calculated numerically using the commercial CPFD (computational particle fluid dynamics) code, Barracuda Version 15. Regions where the ash melting temperature is exceeded are compared with the fouling observed on the walls in the freeboard. The numerically predicted regions agree well with the observed location of the deposits on the walls. Next, the model is used to find an optimized operating point with fewer regions in which the ash melting temperature is exceeded. Therefore, three cases with different distributions of the inlet gas streams are simulated. The simulations show if the air inlet streams are moved from the freeboard to the necking area above the bed a more even temperature distribution is obtained over the combustion chamber. Hence, the areas where the ash melting temperatures are exceeded are reduced significantly and the formation of deposits in the optimized operational mode is much less likely.     

Numerical study on coal/ammonia co-firing in a 600 MW utility boiler

Co-firing NH₃ in coal-fired power plants is an attractive method to accelerate the pace of global decarbonization. However, the contradiction between achieving elevated temperature within the furnace and maintaining low NO_x emission constrains the utilization of NH₃ as fuel. In this study, 3-dimensional numerical simulations on coal/NH₃ co-firing cases were conducted in a full-scale boiler for the first time. The influences of NH₃ blending ratio, O₂ enrichment combustion and deep air-staging technology were investigated. The results show that the burnout properties of NH₃ are excellent in co-firing boiler. Higher NH₃ blending ratio leads to lower temperature in the furnace. Enriching O₂ concentration to 30% in the secondary air can compensate the temperature decline caused by 50% NH₃ co-firing, while it brings an undesired surge in NO_x concentrations. The high temperature and strong reducing atmosphere (HT&SRA) could be created by combining the O₂ enrichment and deep air-staging combustion. The NO emission drops by 49.6% due to HT&SRA. Then, high flue gas temperature and low NO_x emission can be achieved simultaneously. HT&SRA improves the overall exergy efficiency for 50% NH₃ co-firing case from 51.65% to 51.78%. The findings open up a promising strategy for utilizing NH₃ as a stationary fuel.     

200MW机组运行性能诊断的热经济学方法

在热经济学结构理论的基础上,讨论了热力系统运行性能诊断的热经济学方法,以200MW机组热力系统的计算模型为例,阐述了各部件及产品关系,建立了系统的热经济学生产模型,并对故障诊断的方法、故障引起的系统资源消耗增量进行了理论分析和实际计算,提出了具有较高灵敏度的故障判别指标,以及反映故障影响的量化指标,并针对具体算例进行了分析计算。     

Artificial intelligence for the modeling and control of combustion processes: a review

Artificial intelligence (AI) systems are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. They can learn from examples, are fault tolerant in the sense that they are able to handle noisy and incomplete data, are able to deal with non-linear problems, and once trained can perform prediction and generalization at high speed. They have been used in diverse applications in control, robotics, pattern recognition, forecasting, medicine, power systems, manufacturing, optimization, signal processing, and social/psychological sciences. They are particularly useful in system modeling such as in implementing complex mappings and system identification. AI systems comprise areas like, expert systems, artificial neural networks, genetic algorithms, fuzzy logic and various hybrid systems, which combine two or more techniques. The major objective of this paper is to illustrate how AI techniques might play an important role in modeling and prediction of the performance and control of combustion process. The paper outlines an understanding of how AI systems operate by way of presenting a number of problems in the different disciplines of combustion engineering. The various applications of AI are presented in a thematic rather than a chronological or any other order. Problems presented include two main areas: combustion systems and internal combustion (IC) engines. Combustion systems include boilers, furnaces and incinerators modeling and emissions prediction, whereas, IC engines include diesel and spark ignition engines and gas engines modeling and control. Results presented in this paper, are testimony to the potential of AI as a design tool in many areas of combustion engineering.     

基于BP神经网络的GD-1高压共轨系统的建模研究

基于GD-1高压共轨燃油喷射系统,运用BP神经网络理论对GD-1系统高压油泵及共轨管进行建模,在Matlab平台上利用实际测得的数据对所建的神经模型进行训练,利用Simulink工具将训练好的高压油泵及共轨管模型与GD-1控制策略连接在一起进行闭环仿真,仿真结果表明设计的神经网络能很好地模拟共轨管内实际油压变化.     

Shape design and numerical analysis on a 1 MW tidal current turbine for the south-western coast of Korea

The study concentrates on the shape design and numerical analysis of a 1 MW horizontal axis tidal current turbine (HATCT), which can be applied near the southwest regions of Korea. On the basis of actual tidal current conditions of south-western region of Korea, configuration design of 1 MW class turbine rotor blade is carried out by blade element momentum theory (BEMT). The hydrodynamic performance including the lift and drag forces, is conducted with the variation of the angle of attack using an open source code of X-Foil. The optimized blade geometry is used for Computational Fluid Dynamics (CFD) analysis with hexahedral numerical grids. This study focuses on developing a new hydrofoil and designing a blade with relatively shorter chord length in contrast to a typical TCT blade. Therefore, after a thorough study of two common hydrofoils, (S814 and DU-91-W2-250, which show good performance for rough conditions), a new hydrofoil, MNU26, is developed. The new hydrofoil has a 26% thickness that can be applied throughout the blade length, giving good structural strength. Power coefficient, pressure and velocity distributions are investigated according to Tip Speed Ratio by CFD analysis. As cavitation analysis is also an important part of the study, it is investigated for all the three hydrofoils. Due to the shorter chord length of the new turbine blade in contrast to a typical TCT blade design, a Fluid Structure Interaction (FSI) analysis is also done. Concrete conclusions have been made after comparing the three hydrofoils, considering their performance, efficiency, occurrence of cavitation and structural feasibility.     

一种电站热工流体系统故障诊断的方法

提出了对复杂系统进行故障诊断的系统划分策略 ,并以电站中的凝结水系统为例 ,介绍了系统仿真的方法及模型 ,探讨了使用实时系统仿真模型与故障模型来进行故障判断及诊断的方法。本方法不仅可以对系统中的部分常见故障 (如管道的泄漏与堵塞 )进行诊断 ,而且解决了复杂系统中剩余量生成困难的问题 ,为实时的、自主型的故障诊断系统在电站中的应用打下了基础。     

一种基于单谐次角振动信号的内燃机工作状态监测新方法

分析了内燃机轴承低阶扭振振型特性;提出了单谐次准等差振幅模型。当内燃机轴系满足此条件时,提出一种利用曲轴低谐次扭振信号幅值监测内燃机工作状态的新方法。并以某机车柴油发电机组轴系为对象进行了应用研究,验证了本方法的实用性和诊断准确性。新方法不需要其他结构参数,简便易行,而且准确度高,适用广泛,有较强的工程实用价值。     

Research on the inducing factors and characteristics of knock combustion in a DI hydrogen internal combustion engine in the process of improving performance and thermal efficiency

Hydrogen energy is gaining greater attention because of the energy crisis and CO2 emissions, and knock combustion has become the main obstacle to improving thermal efficiency and power performance of hydrogen engines, which is an important method of hydrogen energy application. In this paper, the knock characteristic parameters and the factors affecting knock tendency of a 2.0 L DI hydrogen engine are investigated experimentally. The results reveal the variation in knock intensity is not linear with the retarding of SOI, which is related to the cylinder mixture distribution. Furthermore, methods such as increasing injection pressures can be useful in reducing the knock intensity. Equivalence ratio has a greater impact on knock compared with other parameters. The conclusions can be used in the further exploration of the knock combustion mechanism in DI hydrogen engines.     

Influence of the equivalence ratio on the knock and performance of a hydrogen direct injection internal combustion engine under different compression ratios

Hydrogen has become an ideal alternative fuel for internal combustion engines. However, with an increase in the equivalence ratio and compression ratio, knock combustion is more likely to occur, which limits its engineering application. In this study, the effects of the equivalence ratio on the knock under different compression ratios were studied through numerical simulation. The signal energy ratio (SER) were used to evaluate the knock onset (KO). The knock intensity (KI) and engine performance were compared and analyzed under different equivalence ratios and compression ratios. The results revealed that a high compression ratio can significantly amplify the effect of the equivalence ratio on combustion and knock. Under the compression ratio of 17.5, KI increases more quickly, with the constant equivalence ratio rise and is more sensitive to ignition timing with equivalence ratio increasing. For the compression ratio of 11, the ignition timing limited by knock is about 4°CA earlier than that of compression ratio of 17.5, and the engine performance is more stable in the low-knock zone. However, when KI exceeds 1 MPa, the power and ITE decreases 20.6% and 20.9% respectively.     

A numerical study on the effects of constant volume combustion phase on performance and emissions characteristics of a diesel-hydrogen dual-fuel engine

A detailed numerical study is carried out to investigate the performance of a diesel-hydrogen dual fuel (DF) compression ignition engine operating under a novel combustion strategy in which diesel injection and most of the combustion occur at a constant volume. A detailed validation of the numerical model for diesel-hydrogen DF engine operation has been carried out. Then a parametric study has been performed to investigate the effects of the constant volume combustion phase (CVCP) at up to 90% hydrogen energy share (HES) on engine performance and emissions at low and high load with comparisons to the conventional engine. The results demonstrate that the CVCP strategy can improve thermal efficiency at all HESs and load conditions with far lower carbon-based emissions. Conventional DF engines struggle at low load high HESs due to the reduced diesel injection failing to ignite the leaner premixed charge. Through use of a CVCP thermal efficiency at low load 90% HES increased from 11% to 38% with considerably reduced hydrogen emission due to the increased temperatures and pressures allowing for the wholesale ignition of the hydrogen-air mix. It was also found that increasing the time allowed for combustion within the CVCP, by advancing the diesel injection, can lead to even further thermal efficiency gains while not negatively impacting emissions.     

百万机组塔式炉脱硝供氨系统优化设计应用研究

针对国内某百万千瓦机组塔式炉选择性催化还原(Selective Catalytic Reduction,SCR)烟气脱硝装置两侧反应器喷氨量无法独立调节而造成喷氨不均的问题,结合现场测试数据,采用计算流体动力学(Computational Fluid Dynamics,CFD)数值模拟方法进行双母管供氨优化改造方案的设计及校核。结果表明:相同出口NO_x排放浓度时,两侧反应器脱硝效率偏差由改造前的19.0%下降到2.9%,平均氨逃逸浓度由3.7 mg/m~3降低到2.3 mg/m~3,局部氨逃逸浓度由6.2 mg/m~3降低到2.6 mg/m~3,两侧反应器出口NO_x浓度均值偏差得到消除。供氨系统优化改造不仅提升了脱硝装置整体性能,还降低了局部氨逃逸浓度峰值,减轻了空气预热器硫酸氢铵(Ammoniu Bisulfate,ABS)堵塞风险。     

状态监测与诊断用燃气轮机热力模型的构造方法

提出了以机组实测验收数据为估算依据,在没有详细设计参数的情况下进行机组变工况计算的建模方法,较好地解决型号平均特性与特定机组特性之间的差异问题。采用本方法对某电站单轴燃气轮机变工况性能进行了估算,计算结果与发表数据有较好的吻合,证明了该方法的有效性,可以用于燃气轮机状态监测与诊断。     

A comprehensive power loss,efficiency, reliability and cost calculation of a 1 MW/500 kWh battery based energy storage system for frequency regulation application

Battery based energy storage system (ESS) has tremendous diversity of application with an intense focus on frequency regulation market. An ESS typically comprised of a battery and a power conversion system. A calculation of performance parameters is performed in this research. The aim is to formulate an in-depth analysis of the ESS in terms of power losses of the semiconductor and electrical devices, efficiency, reliability and cost which would foster various research groups and industries around the globe to improve their future product. In view of this, a relation between the operating conditions and power losses is established to evaluate the efficiency of the system. The power loss calculation presented in this paper has taken into account the conduction and switching losses of the semiconductor devices. Afterwards, the Arrhenius Life Stress relation is adopted to calculate the reliability of the system by considering temperature as a covariate. And finally, a cost calculation is executed and presented as a percentage of total cost of the ESS. It has been found that the power loss and efficiency of the ESS at rated power is 146 kW and 85% respectively. Furthermore, the mean time between failures of the ESS is 8 years and reliability remains at 73% after a year. The major cost impact observed is for battery and PCS as 58% and 16% respectively. Finally, it has been determined that further research is necessary for higher efficient and lower cost system for high penetration of energy storage system in the market.     

Exergy destruction during the combustion process as functions of operating and design parameters for a spark‐ignition engine

The second law of thermodynamics provides different perspectives compared with the first law, and provides the property exergy. Exergy is a measure of the work potential of energy from a given thermodynamic state. Unlike energy, exergy may be destroyed, and for reciprocating engines, the major source of this destruction is during the combustion process. This paper provides an overview of the quantitative levels of exergy destruction during the combustion process as function of engine operating and design parameters, and for eight fuels. The results of this study are based on a spark‐ignition, automotive engine. The amount of exergy destroyed during the combustion process has been determined as functions of speed, load, equivalence ratio, start of combustion, combustion duration, combustion rate parameters, exhaust gas recirculation (EGR), inlet oxygen concentration, and compression ratio. In addition, design parameters that were examined included expansion ratio and the use of turbocharging. The fuels examined included isooctane (base), methane, propane, hexane, methanol, ethanol, hydrogen and carbon monoxide. For the part load base case (1400 rpm and a bmep of 325 kPa) using isooctane, the destruction of exergy was 20.8% of the fuel exergy. For many of the engine operating and design parameter changes, this destruction was relatively constant (between about 20 and 23%). The parameters that resulted in the greatest change of the exergy destruction were (1) equivalence ratio, (2) EGR, and (3) inlet oxygen concentration. For the base case conditions, the exergy destruction during the combustion process was different for the different fuels. The lowest destruction (8.1%) was for carbon monoxide and the highest destruction (20.8%) was for isooctane. The differences between the various fuels appear to relate to the complexity of the fuel molecule and the presence (or absence) of an oxygen atom. Copyright © 2011 John Wiley & Sons, Ltd.     

A process simulation model for a 2 ton h−1 incinerator (a combined bed combustion and furnace heat transfer model)

A process simulation model was constructed for a 2 ton h⁻¹ incinerator. The simulation model was designed to provide system performance parameters according to various operating conditions. In accommodating the wide variation of quality and composition of input wastes, the plant operating parameters such as amount of excess air, preheated air temperature, waste feed rate and primary air distribution over the stoker, etc. must be carefully controlled. The proposed model calculates operating variables of each submodule, by employing steady-state thermal and material balance equations. Combustion of waste bed, and its radiative heat transfer in the combusion chamber are considered. The calculated results of the combustion chamber performance are evaluated, in terms of temperature, locations and width of the flame band, and mean residence time in the secondary combustion chamber. These results are compared with a limited set of field test measurements for verification of the model. © 1998 John Wiley & Sons, Ltd.