Experimental Study of Diesel-NG Dual Fuel Electronic System for F6L912Q Engine

In order to improve the diesel engine emission performance and convert the diesel engine to dual fuel engine, a dual fuel (diesel and compressed natural gas (CNG)) electronic system was developed, in which electromagnetic valves were used to control multi point natural gas injection. The system was designed for type F6L912Q diesel engine and the function of the system was testified on test cell. The test results showed that the system had great advantages in power ability and emission performance. The average CNG substitution at rated load was over 80%. The dual fuel system was practical. To adopt dual fuel system was a good way to improve the engine's emission performance.

Effect of exhaust gas recirculation and intake pre-heating on performance and emission characteristics of dual fuel engines at part loads

Achieving simultaneous reduction of NOx,CO and unburned hydrocarbon(UHC) emissions without compromising engine performance at part loads is the current focus of dual fuel engine research.The present work focuses on an experimental investigation conducted on a dual fuel(diesel-natural gas) engine to examine the simultaneous effect of inlet air pre-heating and exhaust gas recirculation(EGR) ratio on performance and emission characteristics at part loads.The use of EGR at high levels seems to be unable to improve the engine performance at part loads.However,it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency,resulting in reduced levels of both unburned hydrocarbon and NOx emissions.CO and UHC emissions are reduced by 24% and 31%,respectively,The NOx emissions decrease by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.

Study of CNG／diesel dual fuel engine＇s emissions by means of RBF neural network

Great efforts have been made to resolve the serious environmental pollution and inevitable declining of energy resources. A review of Chinese fuel reserves and engine technology showed that compressed natural gas (CNG)/diesel dual fuel engine (DFE) was one of the best solutions for the above problems at present. In order to study and improve the emission performance of CNG/diesel DFE, an emission model for DFE based on radial basis function (RBF) neural network was developed which was a black-box input-output training data model not require priori knowledge. The RBF centers and the connected weights could be selected automatically according to the distribution of the training data in input-output space and the given approximating error. Studies showed that the predicted results accorded well with the experimental data over a large range of operating conditions from low load to high load. The developed emissions model based on the RBF neural network could be used to successfully predict and optimize the emissions performance of DFE. And the effect of the DFE main performance parameters, such as rotation speed, load, pilot quantity and injection timing, were also predicted by means of this model. In resumé, an emission prediction model for CNG/diesel DFE based on RBF neural network was built for analyzing the effect of the main performance parameters on the CO, NOx emissions of DFE. The predicted results agreed quite well with the traditional emissions model, which indicated that the model had certain application value, although it still has some limitations, because of its high dependence on the quantity of the experimental sample data.

Fault Tree Analysis of Fire and Explosion Accidents for Dual Fuel （Diesel/Natural Gas） Ship Engine Rooms

In recent years, China's increased interest in environmental protection has led to a promotion of energy-efficient dual fuel(diesel/natural gas) ships in Chinese inland rivers. A natural gas as ship fuel may pose dangers of fire and explosion if a gas leak occurs. If explosions or fires occur in the engine rooms of a ship, heavy damage and losses will be incurred. In this paper, a fault tree model is presented that considers both fires and explosions in a dual fuel ship; in this model, dual fuel engine rooms are the top events. All the basic events along with the minimum cut sets are obtained through the analysis.The primary factors that affect accidents involving fires and explosions are determined by calculating the degree of structure importance of the basic events.According to these results, corresponding measures are proposed to ensure and improve the safety and reliability of Chinese inland dual fuel ships.

Application of neural network in the study of combustion rate of natural gas／diesel dual fuel engine

In order to predict and improve the performance of natural gas/diesel dual fuel engine (DFE), a combustion rate model based on forward neural network was built to study the combustion process of the DFE. The effect of the operatin g parameters on combustion rate was also studied by means of this model. The stu dy showed that the predicted results were good agreement with the experimental d a ta. It was proved that the developed combustion rate model could be used to succ essfully predict and optimize the combustion process of dual fuel engine.

Knock prediction for dual fuel engines by using a simplified combustion model

The present work used a methane-air mixture chemical kinetics scheme consisting of 119 elementary reaction steps and 41 chemical species to develop a simplified combustion model for prediction of the knock in dual fuel engines. Calculated values by the model for natural gas operation showed good agreement with corresponding experimental values over a broad range of operating conditions.

Injection Strategy in Natural Gas–Diesel Dual-Fuel Premixed Charge Compression Ignition Combustion under Low Load Conditions

Dual-fuel premixed charge compression ignition (DF-PCCI) combustion has been proven to be a viable alternative to conventional diesel combustion in heavy-duty compression ignition engines due to its low nitrogen oxides (NOx) and particulate matter (PM) emissions. When natural gas (NG) is applied to a DF-PCCI engine, its low reactivity reduces the maximum pressure rise rate under high loads. However, the NG–diesel DF-PCCI engine suffers from low combustion efficiency under low loads. In this study, an injection strategy of fuel supply (NG and diesel) in a DF-PCCI engine was investigated in order to reduce both the fuel consumption and hydrocarbon (HC) and carbon monoxide (CO) emissions under low load conditions. A variation in the NG substitution and diesel start of energizing (SOE) was found to effectively control the formation of the fuel–air mixture. A double injection strategy of diesel was implemented to adjust the local reactivity of the mixture. Retardation of the diesel pilot SOE and a low fraction of the diesel pilot injection quantity were favorable for reducing the combustion loss. The introduction of exhaust gas recirculation (EGR) improved the fuel economy and reduced the NOx and PM emissions below Euro VI regulations by retarding the combustion phasing. The combination of an NG substitution of 40%, the double injection strategy of diesel, and a moderate EGR rate effectively improved the combustion efficiency and indicated efficiency, and reduced the HC and CO emissions under low load conditions.

Neutronics Optimization of LiPb-He Dual-Cooled Fuel Breeding Blanket for the Fusion-Driven sub-critical System

The concept of the liquid Li17Pb83 and Helium gas dual-cooled Fuel Breeding Blanket (FBB) for the Fusion-Driven sub-critical System (FDS) is presented and analyzed. Taking self-sustaining tritium (TBR >1.05) and annual output of 100 kg or more fissile 239Pu (FBR > 0.238) as objective parameters, and based on the three-dimensional Monte Carlo neutron-photon transport code MCNP/4A, a neutronics-optimizated calculation of different cases was carried out and the concept is proved feasible. In addition, the total breeding ratio ( BR = TBR + FBR ) is listed corresponding to different cases.

不同海拔下氢气/柴油双燃料发动机燃烧与排放特性研究

基于大气模拟综合测试系统,模拟0 m、1 000 m和2 000 m海拔的大气压,对不同海拔下氢气/柴油双燃料发动机燃烧与排放特性进行研究。研究结果表明:不同海拔下,随着氢气替代率增加,预混合燃烧增强,缸内燃烧速度加快,缸压峰值升高,其对应相位提前;碳烟和CO排放先下降后上升,NO_(x)排放增加,CO_(2)排放减少。随着海拔上升,过量空气系数减小,有效热效率降低。转速为1 600 r/min时,随着海拔高度升高,预混合燃烧减弱,发动机缸压峰值下降,其对应相位推迟;CO排放最低时,与0 m海拔比较,海拔上升至1 000 m、2 000 m,碳烟排放分别增加44.44%和127.78%,CO排放增加8.95%和16.86%,CO_(2)排放增加4.34%和16.86%,碳烟和CO_(2)排放增幅随海拔增加而上升。转速为3 000 r/min时,随着海拔高度上升,缸压峰值略有升高,缸压峰值对应相位提前,预混合燃烧增强;碳烟、NO_(x)、CO和CO_(2)排放升高,排放增幅随海拔升高而增大。与海拔0 m比较,当碳烟排放最低时,海拔上升至1 000 m、2 000 m,碳烟排放分别升高18.67%和56.04%,NO_(x)排放分别上升14.78%和38.40%,CO_(2)排放分别升高7.29%和15.80%;CO排放最低时,海拔上升至1 000 m、2 000 m,CO排放分别上升24.53%和62.87%。

引燃柴油量对双燃料发动机循环变动的影响

为了降低重型高压共轨柴油机燃用LNG-柴油的燃烧循环变动,优化引燃柴油量控制,通过双燃料发动机试验台架,研究了在最大转矩转速1600r/min,功率输出为73kW工况下,随引燃柴油喷油量的增加,峰值压力、峰值压力升高率、平均指示压力循环变动的变化趋势。研究结果表明,随引燃柴油量的增加,双燃料发动机的峰值压力、峰值压力升高率和平均指示压力的循环变动趋势相同,它们的均值均增大,标准差减小,循环分布集中,循环变动系数降低。在不导致爆震燃烧的前提下,适当增大引燃柴油量,能够改善双燃料发动机的燃烧稳定性。

喷油压力和进气温度对氨/正十二烷双燃料发动机燃烧稳定性影响研究

基于一台光学发动机,在1200 r/min转速下,采用进气道低压喷射氨气,缸内高压直喷高活性正十二烷的双燃料燃烧模式,应用火焰高速成像方法,研究了喷油压力和进气温度对氨/正十二烷双燃料发动机缸内燃烧的影响规律.结果表明,直喷燃料喷射压力降低,导致正十二烷浓度分层增大,自燃着火点增多,更有利于正十二烷引燃均质预混合的氨气;直喷压力在30 MPa和60 MPa工况下,火焰初期NH3燃烧的橘色火焰占主导,之后呈现正十二烷预混蓝色火焰与NH3橘色火焰叠加现象;在90 MPa喷射压力下,火焰发展初期正十二烷预混蓝色火焰占主导,随着燃烧发展NH3橘色火焰的比例逐渐增多.在30 MPa喷射压力下,缸内直喷正十二烷可以实现90%氨气比例的稳定着火,但是燃烧反应速率过低,燃烧持续期过长.进气温度从100℃升高到125℃后,自燃着火点数量增加,氨双燃料燃烧反应速率提高,放热率峰值增大;然而进气温度进一步从125℃提高到150℃时,对燃烧压力和放热率影响很小.上述研究表明,较低的直喷燃料喷射压力和适当提高进气温度更有利于氨燃料的稳定着火以及燃烧速率的提升和氨在双燃料中占比的提高.

EGR技术对生物柴油混合燃料发动机性能的影响研究

为缓解柴油掺烧生物柴油导致的NO_(x)排放过高问题,将4190ZLC船用中速柴油机作为试验台架,通过AVL_FIRE软件建立燃烧室模型,并验证该模型准确性。设置生物柴油掺混比0~40%等4组变量,EGR率0~12.5%等4组变量,进行柴油机燃烧、性能和排放分析。结果表明,掺烧适量生物柴油能够降低柴油机缸内温度,降低Soot排放,但同时会导致NO_(x)排放明显升高;EGR的引入能够实现低温燃烧,显著降低NO_(x)排放,但EGR率过高会增加Soot排放。生物柴油掺混比B40、EGR率12.5%组合NO排放比原机降低47.7%,Soot排放质量分数比原机降低98.13%。本文结果将为柴油掺混生物柴油燃烧并结合EGR技术提供一定的研究方向。

甲醇-柴油反应活性控制压燃发动机排放特性与经济性预测及优化

基于甲醇-柴油双燃料反应活性控制压燃(reactivity controlled compression ignition,RCCI)发动机台架试验数据,建立了基于粒子群算法(particle swarm optimization,PSO)优化BP神经网络的甲醇-柴油RCCI发动机排放特性、经济性预测智能模型,以发动机负荷、甲醇替代率、EGR率为输入参数,NO_(x)、烟度、CO、THC排放和当量有效燃油消耗率为输出,预测模型的决定系数(R^(2))分别为0.99,0.97,0.99,0.98和0.96,平均绝对百分比误差(mean absolute percentage error,MAPE)为6.46%,0.56%,3.12%,1.21%和0.3%,表明构建的PSO-BPNN模型能够有效预测甲醇-柴油RCCI发动机的NO_(x)、烟度、CO、THC排放和经济性。基于偏最小二乘回归(partial least squares regression,PLSR)分析了不同控制参数对发动机污染物排放和经济性的相关性,将PSO-BPNN预测模型与NSGA-Ⅱ算法相结合,以NO_(x)、烟度和当量有效燃油消耗率为目标对负荷、甲醇替代率和EGR率进行协同优化,将最优控制参数组合标定至双燃料发动机的控制系统进行试验验证。结果表明:优化后烟度变化不明显,NO_(x)排放平均降低39.6%,当量有效燃油消耗率平均降低2.6%。

柴油-天然气双燃料喷射器燃料喷射特性的测试方法

针对双燃料喷射器结构复杂而无法实现喷射特性同时测量的问题,以同心双轴针式喷射器为研究对象,提出一种油和气同场测量方法,用动量法获取喷油规律及喷气规律型线,再通过测试密闭容腔内的压力变化计算喷气量,将二者结合可在测量喷气量的同时测量出精确喷气规律,最后对柴油-天然气双燃料喷射器的常用工况进行测试及验证。结果表明,采用动量法结合容积法的喷气规律测量方法得出的喷气量误差不超过5%。对喷射器的一致性进行验证,喷油量与喷气量的波动率均不超过3%,证明其喷射器一致性较好,该测试技术具有较高的准确度与可信度。

甲醇双燃料动力系统在超大型集装箱船上的应用

详细分析甲醇双燃料系统在超大型集装箱船上的应用,包括系统的设计、运营和维护,以及面临的环境问题和安全挑战。通过对甲醇供给系统、主机配置和发电机配置的技术方案进行分析,阐述甲醇双燃料系统在超大型集装箱船上应用存在的问题,并提出一系列针对性的应对策略,确保该系统安全、高效运行,助力航运业实现绿色转型。

基于ANSYS的复式膨胀节强度和轴向刚度有限元分析

通过ANSYS有限元分析,研究了复式膨胀节在同时受内压及轴向位移时的强度和轴向刚度.建立了复式膨胀节的二维轴对称模型,并考虑了非线性对复式膨胀节的影响,将分析结果与EJMA工程近似法计算结果进行对比,表明ANSYS有限元结果更接近实际情况,采用工程近似法分析复式膨胀节时存在一定误差.

预燃室及喷射阀对双燃料发动机性能的影响

基于三维仿真软件Converge构建了船用低速双燃料发动机仿真模型,并验证了模型的准确性.模拟了不同预燃室通道和天然气喷射阀结构下发动机的工作过程,并分析了不同参数优化燃烧和降低排放的潜力.结果表明:对预燃室通道的研究中,适度增加预燃室通道直径和长度均会促进引燃油着火,加快主燃室燃烧进程,但直径过大会增加NO_(x)排放,长度过长会抑制着火并增大点火能量损失;增加通道角度同样会加速燃烧,但当其与扫气角度一致时,角度越大,NO_(x)排放越高;对天然气喷射阀的研究中,降低阀门位置、增大喷射角度和减小阀门直径均会降低甲烷逃逸量;喷射角度对主燃室涡流比的影响较大,当喷射角度与扫气角度相反时,喷射角度越大,燃烧越快,NO_(x)排放越低;适度减小阀门直径可提高天然气射流速度,进而加速燃烧.

基于喷射策略的氨柴双燃料发动机燃烧和排放试验研究

在一台重型柴油发动机试验平台的基础上改造氨柴双燃料发动机,加装了一套电控喷氨系统,采用氨气进气道喷射、柴油缸内直喷方式,通过柴油喷射策略的变化,在发动机1 200 r/min的中高负荷下50%氨能占比工况,开展了氨柴双燃料的燃烧和排放特性优化研究。试验结果表明:氨柴双燃料燃烧时,由于氨燃料燃烧速度慢、起燃温度高等特性,柴油原机的上止点附近单次喷射策略,使得氨燃烧与柴油燃烧不同步,燃烧放热率呈现“双峰”曲线,氨燃烧效率较低。采用柴油双喷策略,通过提前柴油预喷时刻,可推迟柴油起燃时间,活化活塞凹坑外的氨燃料,促使柴油和氨燃烧趋于同步,将“双峰”放热曲线转变成“单峰”放热曲线,从而加快燃烧速度,缩短燃烧持续期,减少未燃氨排放,提升氨燃烧效率。但过度提前预喷时刻会造成柴油撞壁,对发动机指示热效率不利。

基于一次回归正交设计的船舶柴油机掺烧丁醇性能优化

为优化丁醇-柴油双燃料发动机的性能,以4190ZLC-2型船用中速柴油机为原型,利用AVL-FIRE仿真软件建立双燃料发动机高压循环模型,并通过原机验证模型的准确性。在确定丁醇掺混比例为20%后,运用一次回归正交试验设计方法对燃油系统5个参数进行优化,找出指示功率最大值和NOx排放量最小值的参数组合。结果表明:建立的指示功率、NOx排放量预测模型的准确度较高,可用于参数优化匹配研究;指示功率最大参数组合为废气再循环率0%、进气压力0.233MPa、进气温度325.15 K、喷油提前角22.6°CA、喷油孔直径0.26 mm;NO排放量最低参数组合为废气再循环率12.5%、进气压力0.173 MPa、进气温度355.15 K、喷油提前角16.6°CA、喷油孔直径0.32 mm;相较于原机,优化后的指示功率和NOx排放量分别提升7.4%和降低98.3%。

基于混合驱动的双燃料发动机燃烧模型的构建

为实现对处于长时间运行的双燃料发动机燃烧过程的实时映射和在线优化,将Wiebe方程与深度学习神经网络相结合,提出了基于混合驱动的生物柴油/柴油双燃料发动机零维(0-D)预测模型.首先通过鹈鹕算法(POA)对双Wiebe方程参数进行求解;然后利用卷积神经网络结合双向长短时记忆神经网络(CNN-Bi-LSTMNN)建立运行参数和Wiebe参数的参数辨识模型.将Wiebe方程与深度学习神经网络相结合对燃烧过程进行简化、重构,建立基于混合驱动的零维预测模型,进而可以正向求出缸内压力曲线和各种性能结果.结果表明:基于双Wiebe方程结合CNN-Bi-LSTM构建的双燃料发动机零维预测模型具有良好的预测精度和泛化性.模型的开发为双燃料发动机性能的在线评估和优化提供了可靠的数字模型支持.