Numerical investigation on the effects of load conditions and hydrogen-air ratio on the combustion processes of a HSDI engine

Owing to high specific energy and low emissions production, hydrogen is a desirable alternative fuel. The combustion and emission performance can be improved by hydrogen addition injected in-cylinder, intake manifold and aspirated with air. However, engine loads and hydrogen-air ration have a significant effect on the performance, combustion and emission of the diesel-hydrogen (high speed direct injection) HSDI engine. In this paper, the CFD method is used to calculate the combustion process of a diesel-hydrogen dual HSDI engine working at constant speed of 4000 rpm, at different hydrogen added from intake port (hydrogen volume fraction of 0%–10%) and five engine loads (equivalent to 20%, 40%, 60%, 80% and 100% of its maximum output power), respectively. The modelling results showed that the in-cylinder pressure and temperature under low engine load were more affected by hydrogen addition. With increasing hydrogen volume fraction, the indicated expansion work and in-cylinder peak pressure increased, and combustion duration decreased due to faster fuel-air mixing and spray flame speed.     

Modeling and optimization of biodiesel engine performance using kernel-based extreme learning machine and cuckoo search

This study presents the optimization of biodiesel engine performance that can achieve the goal of fewer emissions, low fuel cost and wide engine operating range. A new biodiesel engine modeling and optimization framework based on extreme learning machine (ELM) is proposed. As an accurate model is required for effective optimization result, kernel-based ELM (K-ELM) is used instead of basic ELM because K-ELM can provide better generalization performance, and the randomness of basic ELM does not occur in K-ELM. By using K-ELM, a biodiesel engine model is first created based on experimental data. Logarithmic transformation of dependent variables is used to alleviate the problems of data scarcity and data exponentiality simultaneously. With the K-ELM engine model, cuckoo search (CS) is then employed to determine the optimal biodiesel ratio. A flexible objective function is designed so that various user-defined constraints can be applied. As an illustrative study, the fuel price in Macau is used to perform the optimization. To verify the modeling and optimization framework, the K-ELM model is compared with a least-squares support vector machine (LS-SVM) model, and the CS optimization result is compared with particle swarm optimization and experimental results. The evaluation result shows that K-ELM can achieve comparable performance to LS-SVM, resulting in a reliable prediction result for optimization. It also shows that the optimization results based on CS is effective.     

Microstructure and mechanical properties of Nb4AlC3 MAX phase synthesized by reactive hot pressing

The present study aims at synthesizing the Nb₄AlC₃ MAX phase by reactive hot pressing using Nb:Al:NbC as starting materials. In order to identify the reaction path, interrupted tests at intermediate temperatures were performed as well as differential thermal analyses (DTA) of powders. Coupling between DTA and XRD data and SEM/EDS analyses of the samples allows a better understanding of the reaction mechanisms. Pure and fully dense Nb₄AlC₃ samples were obtained and characterized for the first time by EBSD and SEM to assess, using an original method, grain size and microstructure. For instance, in the present study, an average grain length of 5–7?µm was obtained.Standard mechanical characterizations showed interesting properties: K_Ic≈?6?MPa?m^1/2, E?≈?350?GPa and α?≈?7.10^?6 °C^?1. Oxidation performance of Nb₄AlC₃ was evaluated at 1100?°C under cyclic conditions. A breakaway regime was instantaneously established for this condition, thus demonstrating the impossibility of using such an unprotected material for structural applications at high temperature in air environment.     

Recent advancement and prospective of waste plastics as biodiesel additives: A review

Recently, commodity plastics have been shown to be a promising additive to improve the fuel properties of biodiesel, which offers a promising solution to the plastic pandemic. As many environmental and societal issues arise from plastic pollution, repurposing technologies are paramount in order to meet Sustainable Development Goals (SDG). A potentially cost-effective approach can be achieved by using waste plastics as biodiesel additives – resonating to the expression ‘to kill two birds with one stone’. However, given the novelty of such investigation, current optimization studies show varying results on the ideal plastic-to-biodiesel ratio as well as the reaction parameters. The difficulty in determining the exact optimum values is due to the many variations of biodiesel properties and the complex behaviour of plastic polymers, which are seldom discussed in review papers. Hence, to address the literature gap, this paper offers the necessary fundamentals of biodiesel and plastic dissolution; facilitating future researches to advance the application of plastics as viable biodiesel additives. Accordingly, the topics covered include the fuel and solvent properties of biodiesel related to its' composition, as well as the polymer dissolution phenomena. Finally, as the focal aim of the paper, a synopsis on the recent advancement of plastic-added biodiesel is presented; in particular, those that are related to the blend characteristics, fuel properties, combustion quality, and environmental impact.     

Experimental investigations on the effect of fuel injection parameters on diesel engine fuelled with biodiesel blend in diesel with hydrogen enrichment

Fuel injection pressure and injection timing are two extensive injection parameters that affect engine performance, combustion, and emissions. This study aims to improve the performance, combustion, and emissions characteristics of a diesel engine by using karanja biodiesel with a flow rate of 10 L per minute (lpm) of enriched hydrogen. In addition, the research mainly focused on the use of biodiesel with hydrogen as an alternative to diesel fuel, which is in rapidly declining demand. The experiments were carried out at a constant speed of 1500 rpm on a single-cylinder, four-stroke, direct injection diesel engine. The experiments are carried out with variable fuel injection pressure of 220, 240, and 260 bar, and injection timings of 21, 23, and 25 °CA before top dead center (bTDC). Results show that karanja biodiesel with enriched hydrogen (KB20H10) increases BTE by 4% than diesel fuel at 240 bar injection pressure and 23° CA bTDC injection timing. For blend KB20H10, the emissions of UHC, CO, and smoke opacity are 33%, 16%, and 28.7% lower than for diesel. On the other hand NOx emissions, rises by 10.3%. The optimal injection parameters for blend KB20H10 were found to be 240 bar injection pressure and 23 °CA bTDC injection timing based on the significant improvement in performance, combustion, and reduction in exhaust emissions.     

基于ArcGIS的煤炭储量管理方案

随着“数字矿山”建设步伐的加快和GIS技术的广泛应用,利用GIS技术进行煤炭资源管理,实现储量图件、数据的动态管理及分析、表达,保证煤炭资源的合理开采和充分利用,是煤矿管理工作者必须面对的问题.基于ArcGIS,在分析煤炭资源管理模式的基础上,提出了一套实用的煤炭储量管理方案.     

渤海油田地质信息空间数据库建设探讨

油气资源勘探开发是影响我国经济可持续发展的重要因素之一。如何利用信息化技术建立油田地质信息数据库,进而为油气资源勘探开发服务是一项重要的研究任务。本文讨论了油田地质信息空间数据库的技术方法及业务流程,并在此基础上建立渤海油田地质信息数据库。此数据库建立模式对于油气资源勘查领域具有重要的理论及实际意义。     

YZC12Ⅱ型振动压路机的降噪技术浅析

YZC12Ⅱ型振动压路机为双频双幅串联式振动压路机,该机为全液压传动,采用全电液控制技术,具有两挡无级调速、双频双幅振动、三级减振、三级制动、铰接式转向和无级喷雾洒水等功能.投放市场后,用户反应该机机外噪声大,并存在非常刺耳的周期性啸叫声的问题.对压路机的动力系统进行分析,认为柴油机风扇在高速转动过程中,风扇叶片和高速通过发动机机罩的冷却风流所发生的周期性相互作用是产生高频噪声的主要原因.运用阻尼降噪和拍振现象的原理,对发动机机罩进风口的结构形式进行改进,将原平板式网状进风口改成百叶窗式的进风口,并在百叶窗叶片下侧粘贴海绵,同时在机罩内侧封闭部分粘贴吸音海绵.改进后测得机外噪声为95.7 dB(A),降噪效果明显.同时,在发动机罩顶部的左右方向增加两条加强筋,以使发动机机罩的固有频率远离噪声的激振频率,试验证明,经过改进后,发动机高速运转时产生的周期性啸叫声被消除.     

基于ArcGIS 图元的军事标图系统

为提高军事标图系统的辅助决策能力,提出基于ArcGIS图元方法。通过多个控制点生成非规则军标,采用ArcGIS绘图函数替代图元动态绘制非规则军标,利用图元的属性标识符将军标与属性数据集成,设计和实现一个军事标图系统,并在实际工程中得到成功应用。结果表明：该系统不但标图便捷,而且具有辅助决策能力,为指挥人员作出科学决策提供强有力的手段。     

基于ArcGIS构建图库一体化海图系统的研究

针对现阶段我国海图制图与数据建库相分离的"图库两体化"现状存在的缺陷,提出了基于ArcGIS搭建图库一体化海图生产体系的技术方案。本文以中国北部海区的海事测绘数据为基础,以ArcGIS为平台,进行了一体化海图生产体系的构建研究:进行了海事数据库层次结构、属性字段和属性域规则的设计;定制了ArcGIS海图符号库、实现海图智能标注和创建Representation制图表达等关键制图技术;并基于ArcGIS Engine开发了一体化平台,实现了对ArcCatalog和ArcMap应用程序的直接调用,实现了海图建库与制图输出的一体化。