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Applicability of high dimensional model representation correlations for ignition delay times of n-heptane

Wang LIU, Jiabo ZHANG, Zhen HUANG, Dong HAN

《能源前沿（英文）》 2019年 第13卷 第2期   页码 367-376 doi: 10.1007/s11708-018-0584-9

摘要： It is difficult to predict the ignition delay times for fuels with the two-stage ignition tendency because of the existence of the nonlinear negative temperature coefficient (NTC) phenomenon at low temperature regimes. In this paper, the random sampling-high dimensional model representation (RS-HDMR) methods were employed to predict the ignition delay times of n-heptane/air mixtures, which exhibits the NTC phenomenon, over a range of initial conditions. A detailed n-heptane chemical mechanism was used to calculate the fuel ignition delay times in the adiabatic constant-pressure system, and two HDMR correlations, the global correlation and the stepwise correlations, were then constructed. Besides, the ignition delay times predicted by both types of correlations were validated against those calculated using the detailed chemical mechanism. The results showed that both correlations had a satisfactory prediction accuracy in general for the ignition delay times of the n-heptane/air mixtures and the stepwise correlations exhibited a better performance than the global correlation in each subdomain. Therefore, it is concluded that HDMR correlations are capable of predicting the ignition delay times for fuels with two-stage ignition behaviors at low-to-intermediate temperature conditions.

关键词： ignition delay     random sampling     high dimensional model representation     n-heptane     fuel kinetics    

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Effect of 2,5-dimethylfuran addition on ignition delay times of n-heptane at high temperatures

Zhenhua GAO, Erjiang HU, Zhaohua XU, Geyuan YIN, Zuohua HUANG

《能源前沿（英文）》 2019年 第13卷 第3期   页码 464-473 doi: 10.1007/s11708-019-0609-z

摘要： The shock tube autoignition of 2,5-dimethylfuran (DMF)/n-heptane blends (DMF0-100%, by mole fraction) with equivalence ratios of 0.5, 1.0, and 2.0 over the temperature range of 1200–1800 K and pressures of 2.0 atm and 10.0 atm were investigated. A detailed blend chemical kinetic model resulting from the merging of validated kinetic models for the components of the fuel blends was developed. The experimental observations indicate that the ignition delay times nonlinearly increase with an increase in the DMF addition level. Chemical kinetic analysis including radical pool analysis and flux analysis were conducted to explain the DMF addition effects. The kinetic analysis shows that at lower DMF blending levels, the two fuels have negligible impacts on the consumption pathways of each other. As the DMF addition increases to relatively higher levels, the consumption path of n-heptane is significantly changed due to the competition of small radicals, which primarily leads to the nonlinear increase in the ignition delay times of DMF/n-heptane blends.

关键词： ignition delay time     shock tube     kinetic model     2     5-dimethylfuran (DMF)     n-heptane    

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Study on electrical ignition and micro-explosion properties of HAN-based monopropellant droplet

Yonggang YU, Ming LI, Yanhuang ZHOU, Xin LU, Yuzhu PAN,

《能源前沿（英文）》 2010年 第4卷 第3期   页码 430-435 doi: 10.1007/s11708-010-0010-4

摘要： In order to study the electrical ignition characteristics of hydroxylammonium nitrate (HAN)-based liquid propellant, an experimental device for the electrical heating ignition of a liquid propellant droplet was designed. By using a high speed camera system, the ignition properties of the LP1846 single droplet were observed at different electrical heating speeds. The results show that when the LP1846 droplet is electrified, it mainly goes through an evaporization process, a periodic expansion and contraction process, a stronger thermal decomposition process, and an ignition and combustion process. The periodic expansion and contraction process accompanies the droplet micro-explosion phenomenon, and the micro-explosion mechanism is formed mainly due to the overheated water component in LP1846. When peak load voltage is from 80 to 140V/s, the ignition delay of the LP1846 droplet is linearly shortened from 0.82 to 0.62s, but the flame is lighter. Based on the above experiments, a simplified model of the electrical heating ignition of the LP1846 single droplet is established.

关键词： liquid propellant     electrical ignition     ignition delay time     transient measurement    

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Ignition delay of dual fuel engine operating with methanol ignited by pilot diesel

ZOU Hongbo, WANG Lijun, LIU Shenghua, LI Yu

《能源前沿（英文）》 2008年 第2卷 第3期   页码 285-290 doi: 10.1007/s11708-008-0060-z

摘要： An investigation on the ignition delay of a dual fuel engine operating with methanol ignited by pilot diesel was conducted on a TY1100 direct-injection diesel engine equipped with an electronic controlled methanol low-pressure injection system. The experimental results show that the polytropic index of compression process of the dual fuel engine decreases linearly while the ignition delay increases with the increase in methanol mass fraction. Compared with the conventional diesel engine, the ignition delay increment of the dual fuel engine is about 1.5° at a methanol mass fraction of 62%, an engine speed of 1600 r/min, and full engine load. With the elevation of the intake charge temperature from 20°C to 40°C and then to 60°C, the ignition delay of the dual fuel engine decreases and is more obvious at high temperature. Moreover, with the increase in engine speed, the ignition delay of the dual fuel engine by time scale (ms) decreases clearly under all engine operating conditions. However, the ignition delay of the dual fuel engine increases remarkably by advancing the delivery timing of pilot diesel, especially at light engine loads.
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An experimental study on ignition of single coal particles at low oxygen concentrations

Wantao YANG, Yang ZHANG, Lilin HU, Junfu LYU, Hai ZHANG

《能源前沿（英文）》 2021年 第15卷 第1期   页码 38-45 doi: 10.1007/s11708-020-0692-1

摘要： An experimental study on the ignition of single coal particles at low oxygen concentrations ( <21%) was conducted using a tube furnace. The surface temperature ( ) and the center temperature ( ) of the coal particles were obtained from the images taken by an infrared camera and thermocouples respectively. The ignition processes were recorded by a high-speed camera at different values and furnace temperatures . Compared with literature experimental data obtained at a high value, the ignition delay time decreases more rapidly as increases at the low region. The responses of and to the variation of are different: decreases while remains nearly constant with increasing at a low value. In addition, is less sensitive to while the ignition temperature is more sensitive to at a low value than in air. Observations of the position of flame front evolution illustrate that the ignition of a coal particle may change from a homogeneous mode to a heterogeneous or combined ignition mode as decreases. At a low value, buoyancy plays a more significant role in sweeping away the released volatiles during the ignition process.

关键词： coal particles     low oxygen concentration     ignition     ignition temperature     ignition modes    

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Numerical study of ignition mechanism of n-heptane direct injection compression-ignition engine

Xiaoping GUO, Zhanjie WANG,

《能源前沿（英文）》 2009年 第3卷 第4期   页码 432-439 doi: 10.1007/s11708-009-0050-9

摘要： A detailed chemical dynamical mechanism of oxidation of n-heptane was implemented into kiva-3 code to study the ignition mechanism of a high-temperature, high-pressure, three-dimensional-space, transient turbulent, non-homogeneous, mono-component fuel in the engine. By testing the quantity of the heat released by the chemical reaction within the cylinder cell, the elementary reaction showing an obvious increase in the cell temperature was defined as ignition reaction and the corresponding cell as ignition position. The main pathway of the ignition reaction was studied by using the reverse deducing method. The result shows that the ignition in the engine can be divided into low-temperature ignition and high-temperature ignition, both of which follow the same rule in releasing heat, called the impulse heat releasing feature. Low-temperature ignition reaction, whose ignition reaction is c5h9o1-4=ch3cho+c3h5-a, follows the oxidation mechanism, while high-temperature ignition reaction, whose ignition reaction is c2h3o1-2=ch3co, follows the decomposition mechanism. No matter which ignition it is in, the chemical reaction that restrains the ignition reaction from lasting is the deoxidization reaction of alkylperoxy radicals.

关键词： compression-ignition engine     ignition mechanism     elementary reaction     n-heptane    

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Influence of different oil feed rate on bituminous coal ignition in a full-scale tiny-oil ignition burner

Chunlong LIU, Qunyi ZHU, Zhengqi LI, Qiudong ZONG, Xiang ZHANG, Zhichao CHEN

《能源前沿（英文）》 2013年 第7卷 第3期   页码 406-412 doi: 10.1007/s11708-013-0266-6

摘要： To reduce oil consumption during firing-up and partial-load operation, a tiny-oil ignition burner has been recommended. Through reacting-flow experiments performed on a full-scale experimental setup, the influence of different oil flow rates on bituminous coal combustion as well as flow rates without coal feed was analyzed. The ignition burner is identical to that normally used in an 800 MWe utility boiler. Under operating conditions with flow rates of 50, 100, and 150 kg/h, gas temperature distributions were measured in the burner. At the equivalent measuring points at the exits of the first and second combustion chambers, these distributions remained almost unchanged under a constant coal feed rate of 4 t/h. However on the burner centerline, distributions increased slightly with increasing flow rate. Different gas concentrations were measured at the center of the burner exit. For instance, the O concentration at the burner exit varied from 0.01% to 0.31% whereas CO concentrations were more than 10000 ppm. At the same coal feed rate of 4 t/h, burner resistances are 480, 600, and 740 Pa for oil flow rates of 50, 100, and 150 kg/h, respectively.

关键词： ignition     coal     burner     boiler     oil flow rate    

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Numerical simulation of combustion characteristics at different coal concentrations in bituminous coal ignitionin a tiny-oil ignition burner

Chunlong LIU, Qunyi ZHU, Zhengqi LI, Qiudong ZONG, Yiquan XIE, Lingyan ZENG

《能源前沿（英文）》 2013年 第7卷 第2期   页码 255-262 doi: 10.1007/s11708-013-0255-9

摘要： With the objective of producing a full-scale tiny-oil ignition burner, identical to the burner used in an 800 MWe utility boiler, numerical simulations were performed using Fluent 6.3.26 to study the progress of ignition for four coal concentration settings covering sub-operation conditions prevailing during the experiments performed with the burner. The numerical simulations conformed to the experimental results, demonstrating the suitability of the model used in the calculations. Simulations for a coal concentration of 0.40 kg/kg corresponding to a single burner operating at its rated output were also conducted, which indicated that gas temperatures along the burner centerline were high. As gas flowed to the burner nozzle, the high-temperature region expanded, ensuring a successful pulverized-coal ignition. With increasing coal concentration (0.08–0.40 kg/kg), the gas temperature along the burner centerline and at the first and second combustion chamber exits decreased at the equivalent radial points. At the center of the second combustion chamber exit, the O concentrations were almost depleted for the five coal concentrations, while the CO concentrations peaked.

关键词： numerical simulation     tiny-oil ignition burner     pulverized coal     temperature field    

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柴油在热壁面上的着火

栗元龙,陆守香,范维澄

《中国工程科学》 2004年 第6卷 第11期   页码 63-65

摘要：

研究了柴油机燃料泄漏后在热壁上的着火，利用统计方法得到着火的临界温度。发现样品燃料的热壁着火温度与自燃点的差值比其它燃料热壁着火的相应值要小得多，而且着火方式也有很大差异。详细解释了泄漏后的液体在热表面上的沸腾蒸发模式，给出了燃料蒸气的质量流率推导公式。

关键词： 热壁面     着火实验     沸腾    

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Detection of schedule delay risk of empirical construction projects

Tsegay GEBREHIWET, Hanbin LUO

《工程管理前沿（英文）》 2018年 第5卷 第2期   页码 251-267 doi: 10.15302/J-FEM-2018086

摘要： In Ethiopian construction projects, schedule delay risk is a predominant issue because it is not properly addressed. Although several studies have been focused on the various effects of risk in construction projects, limited efforts have been made to investigate the typical and the overall schedule delay risk. In this study, our aim is to detect the typical and overall schedule delay risk throughout the construction project lifecycle, which consists of the pre-construction, construction, and post-construction stages, and compare the stages with each other. Common criteria, sub-criteria, and attributes were developed for all alternatives for the purpose of making a risk decision. The methodology that was followed integrated the multiple-criteria decision-making (MCDM) model of fuzzy analytic hierarchy process comprehensive evaluation (FAHPCE) and the relative important index (RII). Data were collected from 77 participants, who were selected through purposive sampling from different contracting organizations in Ethiopian construction projects by means of questionnaires that were distributed to experienced experts. The findings showed that there is a typical delay risk either in the type or in the level of the different construction activities. Consequently, the most influenced alternative is the construction stage because of the high-risk responsibility, resource, and contract condition related criteria. The post-construction stage was the second most influenced stage because of the high-risk responsibility-related criteria. The pre-constructed stage was the least influenced stage that consist high-risk criteria of responsibility, resource, and contract condition related. These differences provided noteworthy information about risk mitigation in construction projects by identifying the exact risk level on specific activity to make appropriate decision.

关键词： fuzzy analytic hierarchy process comprehensive evaluation     construction project     detection of delay risk     relative important index    

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Effect of distributions of fuel concentration and temperature on ignition processes in a diesel PCCI

Yang YU, Wanhua SU,

《能源前沿（英文）》 2010年 第4卷 第2期   页码 269-279 doi: 10.1007/s11708-009-0046-5

摘要： The distributions of fuel concentration and temperature have significant effect on the ignition processes of diesel premixed charge compression ignition (PCCI) combustion. It was found in this study that the ignition process of PCCI combustion organized by multi-pulse injection was strongly influenced by conditions of fuel stratification. The start of low temperature reactions occurred in the leaner area of the combustion chamber in the test engine because the temperature here first reached the point of low temperature reactions. Ignition always occurred in the position where the mixture featured with equivalence ratios close to the mean equivalence ratio of the overall mixture, while the neighboring area of the initial ignition area accumulate heat with a finite speed until finally autoigniting. Moreover, the appearance of highest combustion temperature occurred in the same area at the combustion chamber. For more homogeneous mixture, a higher amount of mixture reached ignition simultaneously, resulting in a larger initial ignition area and a higher temperature at the ignition area. Furthermore, V-type distribution of equivalence ratio was found to be beneficial to retarding high temperature reaction.

关键词： PCCI     fuel stratification     multi-pulse injection     ignition    

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New experimental technique to determine coal self-ignition duration

ZHANG Xinhai, XI Guang, ZHANG Xinhai

《能源前沿（英文）》 2008年 第2卷 第4期   页码 479-483 doi: 10.1007/s11708-008-0058-6

摘要： An artificial neural network (ANN) model was adopted to simulate the relationship between self-ignition duration and sulfur content, ash content, oxygen consumption rate, carbon monoxide as well as carbon dioxide generation rate of coal at different temperatures of self heating process. The data from spontaneous combustion experiments were used for ANN training to obtain the connection strength between nerve cells. An oil-bath programmed temperature experiment device was designed and the experimental condition and the size of the test tube were determined for testing the oxygen consumption and the gases generation rate of coal during self-heating process. The sulfur content, the ash content and the data from the oil-bath experiment were taken as ANN inputs to calculate the experiment self-ignition duration of coal. Compared with spontaneous combustion experiment, less than 1% of coal sample and 10% of time are required with an error of less than 3 days to test self-ignition duration of coal.
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A model reference adaptive control based method for actuator delay estimation in real-time testing

Cheng CHEN, James M. RICLES

《结构与土木工程前沿（英文）》 2010年 第4卷 第3期   页码 277-286 doi: 10.1007/s11709-010-0072-8

摘要： Real-time testing provides a viable experimental technique to evaluate the performance of structural systems subjected to dynamic loading. Servo-hydraulic actuators are often utilized to apply calculated displacements from an integration algorithm to the experimental structures in a real-time manner. The compensation of actuator delay is therefore critical to achieve stable and reliable experimental results. The advances in compensation methods based on adaptive control theory enable researchers to accommodate variable actuator delay and achieve good actuator control for real-time tests. However, these adaptive methods all require time duration for actuator delay adaptation. Experiments show that a good actuator delay estimate can help optimize the performance of the adaptive compensation methods. The rate of adaptation also requires that a good actuator delay estimate be acquired especially for the tests where the peak structural response might occur at the beginning of the tests. This paper presents a model reference adaptive control based method to identify the parameter of a simplified discrete model for servo-hydraulic dynamics and the resulting compensation method. Simulations are conducted using both numerical analysis and experimental results to evaluate the effectiveness of the proposed estimation method.

关键词： real-time testing     actuator delay     compensation     adaptive control     MIT rule     discrete transfer function    

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Numerical simulation of bituminous coal combustion in a full-scale tiny-oil ignition burner: influence

Zhengqi LI, Chunlong LIU, Xiang ZHANG, Lingyan ZENG, Zhichao CHEN

《能源前沿（英文）》 2012年 第6卷 第3期   页码 296-303 doi: 10.1007/s11708-012-0191-0

摘要： The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 (corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively), which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the burner wall and the high-temperature region was enlarged in the radial direction along the primary air flow direction. The O concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.

关键词： numerical simulation     tiny-oil ignition burner     pulverized coal     temperature field    

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End-to-end delay analysis for networked systems

Jie SHEN,Wen-bo HE,Xue LIU,Zhi-bo WANG,Zhi WANG,Jian-guo YAO

《信息与电子工程前沿（英文）》 2015年 第16卷 第9期   页码 732-743 doi: 10.1631/FITEE.1400414

摘要： End-to-end delay measurement has been an essential element in the deployment of real-time services in networked systems. Traditional methods of delay measurement based on time domain analysis, however, are not efficient as the network scale and the complexity increase. We propose a novel theoretical framework to analyze the end-to-end delay distributions of networked systems from the frequency domain. We use a signal flow graph to model the delay distribution of a networked system and prove that the end-to-end delay distribution is indeed the inverse Laplace transform of the transfer function of the signal flow graph. Two efficient methods, Cramer’s rule-based method and the Mason gain rule-based method, are adopted to obtain the transfer function. By analyzing the time responses of the transfer function, we obtain the end-to-end delay distribution. Based on our framework, we propose an efficient method using the dominant poles of the transfer function to work out the bottleneck links of the network. Moreover, we use the framework to study the network protocol performance. Theoretical analysis and extensive evaluations show the effectiveness of the proposed approach.

关键词： Networked system     End-to-end     Delay distribution    

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标题 作者 时间 类型 操作

Applicability of high dimensional model representation correlations for ignition delay times of n-heptane

Wang LIU, Jiabo ZHANG, Zhen HUANG, Dong HAN

期刊论文

Effect of 2,5-dimethylfuran addition on ignition delay times of n-heptane at high temperatures

Zhenhua GAO, Erjiang HU, Zhaohua XU, Geyuan YIN, Zuohua HUANG

期刊论文

Study on electrical ignition and micro-explosion properties of HAN-based monopropellant droplet

Yonggang YU, Ming LI, Yanhuang ZHOU, Xin LU, Yuzhu PAN,

期刊论文

Ignition delay of dual fuel engine operating with methanol ignited by pilot diesel

ZOU Hongbo, WANG Lijun, LIU Shenghua, LI Yu

期刊论文

An experimental study on ignition of single coal particles at low oxygen concentrations

Wantao YANG, Yang ZHANG, Lilin HU, Junfu LYU, Hai ZHANG

期刊论文

Numerical study of ignition mechanism of n-heptane direct injection compression-ignition engine

Xiaoping GUO, Zhanjie WANG,

期刊论文

Influence of different oil feed rate on bituminous coal ignition in a full-scale tiny-oil ignition burner

Chunlong LIU, Qunyi ZHU, Zhengqi LI, Qiudong ZONG, Xiang ZHANG, Zhichao CHEN

期刊论文

Numerical simulation of combustion characteristics at different coal concentrations in bituminous coal ignitionin a tiny-oil ignition burner

Chunlong LIU, Qunyi ZHU, Zhengqi LI, Qiudong ZONG, Yiquan XIE, Lingyan ZENG

期刊论文

柴油在热壁面上的着火

栗元龙,陆守香,范维澄

期刊论文

Detection of schedule delay risk of empirical construction projects

Tsegay GEBREHIWET, Hanbin LUO

期刊论文

Effect of distributions of fuel concentration and temperature on ignition processes in a diesel PCCI

Yang YU, Wanhua SU,

期刊论文

New experimental technique to determine coal self-ignition duration

ZHANG Xinhai, XI Guang, ZHANG Xinhai

期刊论文

A model reference adaptive control based method for actuator delay estimation in real-time testing

Cheng CHEN, James M. RICLES

期刊论文

Numerical simulation of bituminous coal combustion in a full-scale tiny-oil ignition burner: influence

Zhengqi LI, Chunlong LIU, Xiang ZHANG, Lingyan ZENG, Zhichao CHEN

期刊论文

End-to-end delay analysis for networked systems

Jie SHEN,Wen-bo HE,Xue LIU,Zhi-bo WANG,Zhi WANG,Jian-guo YAO

期刊论文