Investigation Techniques of Arson Fire in Low-Temperature Warehouses Using ED-XRF

Investigation techniques for fire prevention in low-temperature warehouses were studied using energy dispersive X-ray fluorescence (ED-XRF). In the first experiment, a sample (galvanized steel sheet plus urethane foam plus sandwich panel) was burned with 500 mL of a flammable liquid (gasoline, thinner, kerosene, and light oil)/ Then, the component change of the sample was measured. In the combustion experiment, there was a difference in the heat of combustion depending on the type of flammable liquid; however, as a result of measuring the component change of the sample with ED-XRF after combustion, the largest component change was measured in the combustion experiment with gasoline. The change was in the order of thinner, kerosene, and diesel. Using ED-XRF, it was possible to distinguish the flammable liquid used in the experiment by measuring the component change of the sample resulting from the difference in the combustion heat of the flammable liquid. A second experiment was conducted under the same conditions as the first experiment, assuming a fire brigade fire suppression condition, and the combustion time of the flammable liquid was limited to 600 s. A combustion characteristic of flammable liquids is that the temperature and heat flux reach the maximum value within 300 s after the start of combustion regardless of the type of liquid. Because the change of composition was confirmed in the order of light oil, it was possible to distinguish the flammable liquid used at the fire site using the ED-XRF measurement result.

Control-Oriented Model of the Mean and Dispersion of Diesel Combustion Phasing With Ignition Assist

Diesel engines equipped with ignition assist devices such as glow plugs may improve combustion behavior at low temperatures and with low cetane fuels found in remote fields. The coordination of injection timing and the energy input of the ignition assist needs to continuously adjust to maintain the best combustion phasing at all conditions. However, most diesel engines do not use closed-loop combustion control and operate in a sub-optimal manner because the dispersion of combustion phasing, also known as cycle-to-cycle variability, requires careful feedback controller design. This work presents an initial investigation of a control-oriented model that captures the average and statistical influence of commercial glow plugs used for ignition assist beyond the start-up phase. Experiments were conducted at a single speed and load operating point as a proof of concept to obtain a model that quantifies the combustion phasing statistics and thus can guide feedback control design. The developed phenomenological model includes the engine’s thermal state because it impacts combustion behavior over the course of repeated experiments. The 3-term mean phasing model and 2-term standard deviation model estimate start of combustion within 0.6 and 0.2 crank angle degrees, respectively, and can be readily expanded to more operating conditions.

Study on the Relationship between Combustion Parameters and Cylinder Head Vibration Signal in Time Domain

Combustion-related characteristic parameters, such as the start of combustion (SoC) and the timing of the peak pressure increase rate (PIR), can be used as the feedback signals for the closed-loop control of combustion. A dynamic Finite Element Method (FEM) model was firstly developed to confirm the closely related time period between combustion pressure and vibration. On this basis, a fast processing method was developed to estimate the timings of SoC and the peak PIR in the closely related time period. This method was verified on a twelve-cylinder heavy-duty diesel engine at various engine speed and load. Results showed that the maximum deviation of the two parameters were within 2 °CA and 1.5 °CA, respectively, which suggested that the proposed method had an adequate accuracy.

Combustion parameter evaluation of diesel engine via vibration acceleration signal

Efficient combustion control has increasingly become a quality requirement for automobile manufacturers because of its impact on pollutant and greenhouse gas emissions. In view of this, the management system development of modern internal combustion engines is mainly aimed at combustion control. The real-time detection of in-cylinder pressure characteristic parameters has a considerable significance on the closed-loop combustion control of the internal combustion engine. This paper presents a detection method in which the start of combustion, peak pressure, maximum pressure rise rate, and phase of maximum pressure rise rate are identified through vibration acceleration signal. In order to analyze the relationship between vibration and in-cylinder pressure signal, experimental data are acquired in a diesel engine by implementing various injection strategies and engine operating conditions (speed and load). The results show that the start of combustion can be detected by analyzing its relationship with the peak position of the filtered vibration signal, and the phase of the maximum pressure rise rate can be identified by examining its relationship with the zero-cross position that is adjacent to the right of the peak position. Moreover, the filtered vibration signals are also truncated in the same length and utilized as inputs for algorithms to detect the peak pressure and the maximum pressure rise rate. The algorithms are mainly performed on data compression (or feature extraction) and target regression. Major algorithms, such as one-dimensional convolutional neural network, compression sensing, wavelet decomposition, multilayer perceptron, and support vector machine, are tested. Various experimental results verify that for the test engine the phase detection accuracy of the start of combustion and maximum pressure rise rate is less than 1.7°CA for a 95% prediction interval width. For the detection of the peak pressure and maximum pressure rise rate, the normalized error threshold is set as 0.05, then the accuracies can be not less than 95%.

Varying Ignition Quality of a Fuel for a HCCI Engine Using a Photochemically-Controlled Additive: The Development of a ‘Smart’ Fuel

This study examines the possibility to provide control over ignition timing in a homogeneous charge compression ignition engine (HCCI) using a fuel additive whose molecular structure can be adapted upon exposure to UV light. The UV adapted molecule has a greater influence on retarding ignition than the original molecule, hence the ignition time can be modulated upon expose to UV light. The new fuel is referred to as a ‘smart fuel’. The fuel additive is in the form of 1,3-cyclohexadiene (CHD), upon UV exposure it undergoes electro-cyclic ring opening to form 1,3,5-hexatriene (HT). Various solutions of iso-octane, n-heptane and CHD have been irradiated by UV light for different amounts of time. CHD to HT conversion was examined using gas chromatography coupled with mass spectrometry. A primary reference fuel (PRF) mixture of 90% iso-octane and 10% n-heptane was used as a baseline in an optically accessible combustion chamber in a large bore, single cylinder compression ignition engine. The engine was operated in HCCI mode, using early injection to provide homogeneous mixture and utilized heated and compressed air intake. Following this a PRF with 5% CHD was used in the engine. A PRF with 5% CHD was then irradiated with UV light for 240 min, resulting in a PRF mixture containing 1.72% HT, this was then used in the engine. The HT containing PRF had a much later start of combustion compared with the CHD containing PRF, which in turn had a later start of combustion compared with the PRF baseline. This study has successfully validated the concept of using a photo-chemical ‘smart’ fuel to significantly change the ignition quality of a fuel in HCCI mode combustion and demonstrated the concept of on-board ‘smart fuel’ applications for ICE.

Optimization of Injection Pressure and Injection Timing on Fuel Sprays, Engine Performances and Emissions on a Developed DI 20C Biodiesel Engine Prototype

Biodiesel, as a renewable fuel that has the potential to replace diesel fossil fuels. With properties in the form of viscosity, density, and surface tension, which are higher than diesel fossil fuel, biodiesel produces poor spray characteristics, and also the high cetane number and oxygen content so that the ignition delay is shorter causes the start of combustion will shift more forward, therefore need to improve injection parameters including injection pressure and timing. The aim of this research is to get the optimal injection parameter optimization so as to improve engine performances and emissions. The method used is to increase the fuel injection pressure from 200 to 230 kg/cm2 and the injection timings were retarded from 22° to 16° BTDC. The results show that increasing injection pressure can improve spray characteristics as indicated by shorter penetration and smaller spray diameter of 30% and 9.8%, respectively and increase in spray spread angle of 21.9%. Then the optimization of engine performances and emissions, obtained at an injection pressure of 230 kg/cm2 and injection timing of 16° BTDC with an increase of power and thermal efficiency of 3.9% and 13.9%, respectively and reduction in smoke emissions of 45.2% at high load.

Numerical Investigation of the Characteristics of the In-Cylinder Air Flow in a Compression-Ignition Engine for the Application of Emulsified Biofuels

This paper presents a numerical analysis of the application of emulsified biofuel (EB) to diesel engines. The study performs a numerical study of three different guide vane designs (GVD) that are incorporated with a shallow depth re-entrance combustion chamber (SCC) piston. The GVD variables were used in three GVD models with different vane heights, that is, 0.2, 0.4 and 0.6 times the radius of the intake runner (R) and these were named 0.20R, 0.40R and 0.60R. The SCC piston and GVD model were designed using SolidWorks 2017, while ANSYS Fluent version 15 was used to perform cold flow engine 3D analysis. The results of the numerical study showed that 0.60R is the optimum guide vane height, as the turbulence kinetic energy (TKE), swirl ratio (Rs), tumble ratio (RT) and cross tumble ratio (RCT) in the fuel injection region improved from the crank angle before the start of injection (SOI) and start of combustion (SOC). This is essential to break up the heavier-fuel molecules of EB so that they mix with the surrounding air, which eventually improves the engine performance.

Simulation of predictive kinetic combustion of single cylinder HCCI engine

Homogeneous Charge Compression Ignition (HCCI) engine has attracted great attention due to its improved performance and emissions compared to conventional engines. It can reduce both Nitrogen Oxides (NOx) and Particulate Matter (PM) emissions simultaneously without sacrificing the engine performance. However, controlling its combustion phasing remains a major challenge due to the absence of direct control mechanism. The start of combustion is entirely initiated by the chemical reactions inside the combustion chamber, resulted from the compression of its homogeneous mixtures. Varying some critical engine parameters can play a significant role to control the combustion phasing of HCCI engine. This paper investigates the characteristics of HCCI combustion fuelled with n-heptane (C7H16) using single-zone model computational software. The model enabled the combustion object to vary from cycle to cycle. Detailed simulations were conducted to evaluate the effects of air fuel ratio (AFR), compression ratio (CR) and intake air temperature on the in-cylinder pressure and heat release rate. The simulation results showed that the single-zone model was able to predict the two-stage kinetic combustion of HCCI engine; the Low Temperature Heat Release (LTHR) and the High Temperature Heat Release (HTHR) regions. It was found that minor changes in AFR, CR and inlet air temperature led to major changes in the HCCI combustion phasing.