Electronically Controlling the System of Preheating Intake Air by Flame for Diesel Engine Cold-Start

In order to improve the cold start performance of heavy duty diesel engine, electronically controlling the preheating of intake air by flame was researched. According to simulation and thermodynamic analysis about the partial working processes of the diesel engine, the amount of heat energy, enough to make the fuel self ignite at the end of compression process at different temperatures of coolant and intake air, was calculated. Several HY20 preheating plugs were used to heat up the intake air. Meanwhile, an electronic control system based on 8 bit micro controller unit (MCS 8031) was designed to automatically control the process of heating intake air. According to the various temperatures of coolant and ambient air, one plug or two plugs can automatically be selected to heat intake air. The demo experiment validated that the total system could operate successfully and achieve the scheduled function.

Complete Modeling for Systems of a Marine Diesel Engine

This paper presents a simulator model of a marine diesel engine based on physical, semi-physical, mathematical and thermodynamic equations, which allows fast predictive simulations The whole engine system is divided into several functional blocks： cooling, lubrication, air, injection, combustion and emissions. The sub-models and dynamic characteristics of individual blocks are established according to engine working principles equations and experimental data collected from a marine diesel engine test bench for SIMB Company under the reference 6M26SRP1. The overall engine system dynamics is expressed as a set of simultaneous algebraic and differential equations using sub-blocks and S-Functions of Matlab/Simulink. The simulation of this model, implemented on Matlab/Simulink has been validated and can be used to obtain engine performance, pressure, temperature, efficiency, heat release, crank angle, fuel rate, emissions at different sub-blocks. The simulator will be used, in future work, to study the engine performance in faulty conditions, and can be used to assist marine engineers in fault diagnosis and estimation （FDI） as well as designers to predict the behavior of the cooling system, lubrication system, injection system, combustion, emissions, in order to optimize the dimensions of different components. This program is a platform for fault simulator, to investigate the impact on sub-blocks engine＇s output of changing values for faults parameters such as： faulty fuel injector, leaky cylinder, worn fuel pump, broken piston rings, a dirty turbocharger, dirty air filter, dirty air cooler, air leakage, water leakage, oil leakage and contamination, fouling of heat exchanger, pumps wear, failure of injectors （and many others）.

Effects of Hydrogen Addition on Power and Emissions Outputs from Diesel Engines

Energy efficiency and environmental impact have become dominant topics in internal combustion engines development. Among many strategies to improve power and emissions outputs from diesel engines is the partial mix of hydrogen and air as fresh charge components to form extremely lean and homogenous mixture, which resist the spontaneous combustion, while diesel fuel is injected directly inside combustion chamber using the conventional fuel injection systems. This contribution presents an analytical and experimental investigation for the effects of adding hydrogen on diesel engines power output and the reduction of emissions. Parametric analysis is used based on lamped parameters modeling of intake manifold to estimate in cylinder trapped charge. The fuel energy flow to engine cylinders is compared for a range of loads and concentrations to simulate relevant case studies. Diesel fuel reduction for significant range of part-load operation can be achieved by introducing hydrogen, along with power improvement emission reductions are affected positively as well. This is achievable without compromising the engine maximum efficiency, given that most engines are operated at small and part-load during normal driving conditions, which allow for introducing more hydrogen instead of large quantities of excess air during such operation conditions that also can be further improved by charge boosting.

Experimental Investigation of Nozzle Effects on Thrust and Inlet Pressure of an Air-breathing Pulse Detonation Engine

Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.

Investigations of an Air Starting Motor of Marine Medium-Speed Diesel Engine with Numerical Analyses

The marine medium-speed diesel engines are started by two methods;one is the electric motors,and the other air starting motors.Even though air starting motor is dependent of the engine types and sizes,it has been widely used in this area due to its simplicity,convenience and reliability.The purpose of this paper is to give the designing parameters in order to make a proper "Air Starting Motor" using CFD.The aerodynamic approaches were given to understand the internal flow characteristics of the air starting motor.In addition,we have carried out the investigation of effects of tip clearance.In the calculations the tip clearance of air starting motor has been varied between 0,2.8,4.3 and 5.7% of blade span.The results of computation are the tip clearance increased to 2.8%,the torque decreased 24%,and there was no more large changes when the clearances increased to 4.3% and 5.7%.

涡轮增压柴油机高原性能提升试验研究

为解决柴油机高海拔地区扭矩下降问题,在高原进排气模拟试验台架上,开展0~4500m不同海拔高度下某型柴油机的性能试验,对比分析了不同海拔下柴油机的动力性、经济性等指标。研究表明:随着海拔的增加,柴油机扭矩逐渐下降;在同一海拔下,随着转速的下降,扭矩也随之下降,并且在高海拔时该现象更为明显。研究发现,通过采用二级可调增压技术、提高过量空气系数、优化燃油系统结构及参数等手段,柴油机在高原环境下的动力性、经济性得到了明显改善,从而为后续提升柴油机高原性能开发工作提供了可行的技术方向。

摩托车散热器护罩结构对其进风量的影响分析

为保护散热器不被泥土污染,需在散热器进风端添加散热器护罩。散热器护罩添加后对散热器进风量有明显的影响。为获取较优的散热器护罩结构设计,采用CFD分析方法搭建摩托车整车外流场计算域模型,结合不同散热器护罩结构方案,分析散热器护罩结构对其进风量的影响,选取合适的散热器护罩方案开展整车实验验证。结果表明:散热器护罩上导流板角度130°且散热器护罩与芯体间的间隙为1 mm时,散热器进风量为281.7 g/s,与无护罩状态的进风量相当。护罩与芯体间存在间隙可提升散热器进风量,建议间隙控制在1~2.5 mm;散热器护罩网孔倾斜和导流板开孔不利于风量提升。经对比测试,怠速工况、最高车速工况及最大扭矩工况下,散热器添加护罩后的发动机出水温度与无护罩状态的发动机出水温度基本一致。适当减小风扇罩挡风面积可进一步提升散热器进风量,散热器添加护罩后,人体大腿两侧不会出现明显热风。研究结果可为摩托车散热器护罩结构设计及优化提供理论参考。

基于极值搜索的柴油机空气系统模型预测控制

针对配备可变截面涡轮增压器(VGT)、高压废气再循环(EGR)和进气节流阀(TVA)的柴油机进气歧管压力、涡前压力和EGR率多目标跟踪控制问题,提出一种权重系数自学习的扩张状态模型预测控制(MPC)算法.首先,基于柴油机的简化运行机理,提出了三入三出线性变参数预测模型;其次,为补偿因模型与发动机之间偏差造成MPC性能劣化问题,将其等效为3个控制通道的总扰动,并采用扩张状态观测器(ESO)进行快速在线观测和补偿;最后,引入极值搜索算法,对MPC权重系数进行缓慢优化整定,仿真结果表明:在1800 r/min油门开度以最大开度10%的步长向上和向下连续阶跃工况下,对比涡前压力控制,瞬态上升时间相同时本算法超调量比较参数全局优化的比例-积分-微分控制(PID)算法降低30.7%.台架试验中,世界统一瞬态循环(WHTC)动态驾驶循环中进气歧管压力和EGR率跟踪误差IAE(绝对误差积分)值比较传统PID算法分别降低28.3%、17.5%.

无人机用点燃式二冲程柴油机燃烧特性研究

针对柴油燃料雾化蒸发困难导致的发动机燃烧效果差、易爆震的问题,本文采用空气辅助缸内直喷方案,对一台点燃式二冲程柴油发动机开展燃烧特性研究。建立了点燃式二冲程柴油发动机的三维仿真模型,对混合气特性和燃烧特性进行仿真研究,并通过台架试验进行了验证。研究结果表明:点燃式二冲程柴油发动机在热机工况下,点火时刻有58%的燃油蒸发,缸内平均当量比由冷起动工况下的0.2提升至0.8,混合气品质较高,缸内燃烧情况良好。通过燃用汽油、柴油两种燃料进行发动机整机性能对比试验发现,在高转速大负荷工况下,两种燃料的燃烧特性曲线十分接近,柴油燃烧的指示平均有效压力(IMEP)的分布均值仅比汽油低1.2%。总体而言,柴油燃料应用于点燃式二冲程发动机的燃烧性能与汽油燃料相似,且使用柴油燃料时缸内压力最大震荡幅值仅为0.02 MPa,远小于爆震阈值,不会出现爆震现象。

基于MPC的电动复合增压柴油机进气压力控制

涡轮增压技术是提高发动机动力性和经济性的主要途径之一,而传统废气涡轮增压在低速区间存在滞后性。电动增压技术能有效弥补涡轮增压技术不足,但增加了控制自由度,电复合增压控制策略是保证其性能的关键,为此提出一种基于模型预测控制(Model Predictive Control,MPC)的电复合柴油机进气控制策略。基于电动增压器数学物理方程,建立了离散预测控制模型和涡轮增压状态观测器与流量观测器;通过联合仿真平台,对控制策略和控制参数进行标定验证;对比不同工况下MPC与传统PID控制效果以及抗电源电压扰动能力。研究结果表明:基于所设计的观测器,控制算法能在不加装额外涡轮转速传感器的前提下,实现对进气压力的有效控制,最大稳态误差≤1%;能有效自适应正常工况下废气涡轮增压器的响应特性,提高低速响应,起步工况下5.2 s内达到目标进气压比;与传统PID控制算法相比,具有更好抗干扰性和控制精度,动态误差降低42%。

风冷柴油机高负荷轴流冷却风扇气动优化

针对某型风冷柴油机的具有负预旋前置导叶的冷却风扇,考虑导叶和转子的耦合效应,基于多项式代理模型和第二代非支配排序遗传算法实施了冷却风扇多目标气动优化。优化后的效率和全压在近失速工况分别提升1.19%、4.78%,在设计工况分别提高0.29%、3.16%。采用Sobol全局敏感性分析辨识了关键设计变量,结合优化前后流场变化,获得了风扇气动性能提升的流动机理:导叶叶根安装角的减小和转子叶根安装角的增大,共同减小了转子进口攻角,从而增大风扇等熵效率,并弥补了因欧拉功减小所致的全压降低;转子叶顶安装角减小,在削弱叶根与叶顶扩压不平衡度的同时补偿了全压的损失。

基于压缩空气起动的柴油机瞬态特性仿真研究

利用一维仿真软件GT-Power建立大功率船用柴油机稳态模型,在此基础上对系统进行改进,增加高压气瓶、管路、空气分配器、起动空气阀模块,构建基于压缩空气分配器起动的柴油机起动过程瞬态模型,并试验验证2种模型的准确性。系统分析了环境压力、滑油温度和起动系统参数等对柴油机起动过程性能的影响,结果表明,该压缩空气系统驱动柴油机起动时间为2.6 s,能够实现连续6次起动,满足柴油机起动性能要求;选取压缩空气压力为30 bar、气瓶容积为350 L、空气管路直径为36 mm、供气起始角为-5° CA能够有效提高柴油机起动性能;从100%负载突加突卸计算结果来看,该柴油机瞬态调速率达到4.67%,不超过5%的指标要求,转速恢复到额定转速±2%的恢复时间增加至0.57 s,满足指标要求。

高原内燃机车柴油机空气滤清系统流场仿真

为了降低内燃机车柴油机空气滤清系统的流动阻力,提高流动均匀性,采用CFD仿真计算方法,对高原环境下内燃机车柴油机的空气滤清系统进行流体动力学计算分析与研究。首先,完成机车柴油机空气滤清系统在0 m海拔高度时的性能仿真计算,根据计算结果对空气滤清系统结构进行优化。其次,对优化后的空气滤清系统进行海拔高度分别为2 200、4 000、5 100 m高原环境下的CFD计算。最后,对袋式过滤器的排列方式进行研究,将袋式过滤器在初始过滤器排列的基础上,重新排列出shun-66、cha-56、cha-65 3种排列方式,研究不同排列方式的流动均匀性和湍流性能。结果表明,cha-56排列方式的湍流性能最好,进气阻力最小,同时流动均匀性也最优。

大功率船用柴油机空气电机启动过程瞬态特性仿真

为提升大功率船用柴油机启动性能,采用GT-power软件建立船用柴油机稳态模型,增加空气电机启动系统模块,构建柴油机启动过程瞬态模型。基于仿真结果,分析环境排气背压、润滑油温度和压缩空气系统参数等对柴油机启动性能的影响规律。仿真结果可为基于空气电机启动的大功率船用柴油机的系统参数设计和性能评估提供依据。

某机房柴油发电机组动力不足的原因分析

通过现场勘察,结合设备情况,对柴油发电机房进出风口预留面积进行核算,分析柴油发电机组动力不足的原因是降噪施工中选用的百叶窗有效通风面积不足,并提出相应整改措施。

某车用柴油机空调压缩机安装支架模态分析

针对某型号柴油机原整体结构较为紧凑,可携带外围附件少,而应用于某车用领域时其外围附件安装空间不够,在后期应用配套过程中存在空调压缩机难安装的工程实际问题。为解决空调压缩机安装困难的问题,本文提出了几种可能的空调压缩机安装方案,具体分析了几种可行方案的优缺点,并运用专业软件进行模态分析,对几种安装方案进行综合评价分析,从而为应用于某车用领域的该柴油机选择最佳空调压缩机安装设计方案提供决策支持。

整车空气量校准标定指导

在新排放法规执行后,柴油机市场的竞争日渐强化,要求主机厂能够快速适应市场变化,缩短标定周期,提升效率。针对目前柴油机适配情形,一种发动机机型通常会适配多个整车机型,整车端进气系统的差异会造成整车排放性能变化,这是当前存在的一个重要问题。本文研究由于进气系统不同造成的空气量差异问题,提出应对解决方案,以此帮助标定工程师快速了解标定过程中整车空气量校准的重要性,对整车标定工作有一定的指导意义。

人防工程内部电源利用电动汽车蓄电池可行性初探

人民防空工程平时常见于地下汽车库,是战时保障物资输送和人员安全重要组成部分。在现代信息化战争条件下,人防工程战时内部电源可靠性显得尤为重要。为了保证战时电源的安全性、可靠性,本文着重阐述了人防工程电动汽车蓄电池作为战时电源的可行性,该方案与通常在其内部独立设置柴油发电机组作为内部电源有着本质的区别。平时工程内部停放着大量的电动汽车,战时利用其蓄电池组作为内部电源,是难得的战略资源,可大幅度降低工程造价,为赢得现代信息化战争打下坚实基础。

船用柴油机相继增压系统进气均匀性提升仿真设计

为了确保V型相继增压柴油机在改变工作增压器数量时,两侧中冷器的进气能够保持均匀性,对某船用相继增压柴油机进气系统进行了多轮设计与计算流体动力学(Computational Fluid Dynamics,CFD)仿真优化。在此过程中,重点评估了柴油机在单增压模式和三增压模式下,两侧气流分布的均匀性、中冷器进气截面气流流速的均匀性以及压降情况。经过结构优化后,两侧进气流量的最大偏差仅为0.23%,两侧中冷器进气截面流速均匀性指标的最小值达到了0.883,集气腔和中冷器端盖的最大压降为18.2kPa,这些指标处于较优水平。随后,进行了试验验证,其结果表明,在不同增压模式下,两侧中冷器进气的均匀性趋势与仿真结果较为吻合,满足实际使用需求。

可变进气对船用柴油机性能影响的试验研究

为了探究可变进气系统对船用柴油机性能的影响,在一台配备进气可变配气和进气旁通阀的船用中速柴油机上开展试验研究。分别在可变配气机构处于强米勒正时和弱米勒正时,进气旁通阀处于开启和关闭状态下开展船用柴油机螺旋桨特性试验。试验结果表明:采用弱米勒正时可降低燃油消耗率,但是最高燃烧压力和NOx比排放增加,燃油消耗率降低幅度随负荷升高而减小,最高燃烧压力和NOx比排放增加幅度随负荷升高而增加,弱米勒正时对低负荷优化效果更明显。受到最高燃烧压力限制,高负荷必须采用强米勒正时。弱米勒正时角度从20°增加到30°,燃油消耗率基本不变,最高燃烧压力和NOx比排放进一步增加,对于试验柴油机而言,20°弱米勒正时配置更优。开启进气旁通阀可以提高中低负荷增压压力,降低燃油消耗率、排温和烟度。在超低负荷及高负荷时开启进气旁通阀效果与中低负荷相反。在25%及50%负荷下应用可变进气技术,燃油消耗率分别降低6.0%和2.9%、烟度分别降低61.6%和59.7%。合理的可变进气系统控制策略可有效优化船用柴油机性能。