scholarly journals Some Effects of Hydrogen Self-Ignition and Combustion in Supersonic Flow

2014 ◽  
Vol 16 (2-3) ◽  
pp. 245
Author(s):  
U. Zhapbasbayev ◽  
V. Zabaykin ◽  
Y. Makashev ◽  
A. Tursynbay ◽  
B. Urmashev
Keyword(s):  
Supersonic Flow ◽  
Heat Release ◽  
Chemical Reactions ◽  
Laboratory Data ◽  
Combustion Process ◽  
Supersonic Combustion ◽  
Low Flow ◽  
Diffusion Combustion ◽  
Maximum Pressure ◽  
Combustion Mode

<p>Results are presented of computational and experimental investigations of the influence of temperature and flow composition on the hydrogen combustion kinetics for a coaxial fuel supersonic flow. Depending on the flow parameters, combustion is shown to occur with an intense heat release governed by the speed of chemical reactions, or a diffusion combustion with heat release governed by mixing. The computational results are in good agreements of with laboratory data and portrays many important features of supersonic combustion. The influence of the gas temperature and composition on the diffusion combustion of a circular hydrogen jet in supersonic coaxial flow at the over expanded exhaust regimes is investigated. It is found that at low flow temperatures (Т<sub>2 </sub>~ 900 K) and in the absence of water vapors in the oxidizer gas composition, the speed of chemical reactions is the determining factor for combustion. An increase in the flow temperature (Т<sub>2</sub> &gt; 1200 K) causes a reduction of the induction time of the reactive mixture, because the mixing of fuel with oxidizer decreases, and a “sluggish” diffusion combustion of non-mixed gases is observed. The presence of water vapor and active radicals in the gas ensures the self-ignition from the start of the mixing, and the diffusion combustion mode is limited by mixing of the hydrogen jet with the coaxial flow (similar to the case with high initial temperatures of the air stream). In the case of the delay combustion process the maximum pressure level on the wall is 10% more than that in the combustion mode with ignition at the start of mixing. A sluggish combustion regime may lead to an incomplete hydrogen burnout.</p>

Analysis of chemical effects on reflected-shock flow fields in combustible gas

1985 ◽  
Vol 160 ◽  
pp. 29-45 ◽  
Author(s):  
Yasunari Takano ◽  
Teruaki Akamatsu
Keyword(s):  
Heat Release ◽  
Chemical Reactions ◽  
Induction Time ◽  
Combustion Process ◽  
Chemical Species ◽  
Flow Fields ◽  
Rate Equations ◽  
Reflected Shock ◽  
Combustible Gas ◽  
Analytical Results

This paper analyses effects of chemical reactions on reflected-shock flow fields in shock tubes. The method of linearized characteristics is applied to analyse gasdynamic disturbances due to chemical reactions. The analysis treats cases where combustible gas is highly diluted in inert gas, and assumes that flows are one-dimensional and that upstream flows in front of the reflected-shock waves are in the frozen state. The perturbed gasdynamic properties in the reflected-shock flow fields are shown to be expressible mainly in terms of a heat-release function for combustion process. In particular, simple relations are obtained between the heat-release function and the physical properties at the end wall of a shock tube. As numerical examples of the analysis, the present formulation is applied to calculate gasdynamic properties in the reflected-shock region in a H2–O2–Ar mixture. Procedures are demonstrated for calculation of the heat-release function by numerically integrating rate equations for chemical species. The analytical results are compared with rigorous solutions obtained numerically by use of a finite-difference method. It is shown that the formulation can afford exact solutions in cases where chemical behaviours are not essentially affected by gasdynamic behaviours. When the induction time of the combustion process is reduced to some extent owing to gasdynamic disturbances, some discrepancies appear between analytical results and rigorous solutions. An estimate is made of the induction-time reduction, and a condition is written down for applicability of the analysis.

scholarly journals Effect of Injection Strategies in Diesel/NG Direct-Injection Engines on the Combustion Process and Emissions under Low-Load Operating Conditions

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 990 ◽  
Author(s):  
Jinze Li ◽  
Longfei Deng ◽  
Jianjun Guo ◽  
Min Zhang ◽  
Zhenyuan Zi ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Direct Injection ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Operating Conditions ◽  
Diffusion Combustion ◽  
Combustion Mode ◽  
Low Load ◽  
Hc Emissions ◽  
Injection Strategies

The direct injection of natural gas (NG), which is an important research direction in the development of NG engines, has the potential to improve thermal efficiency and emissions. When NG engines operate in low-load conditions, combustion efficiency decreases and hydrocarbon (HC) emissions increase due to lean fuel mixtures and slow flame propagation speeds. The effect of two combustion modes (partially premixed compression ignition (PPCI) and high pressure direct injection (HPDI)) on combustion processes was investigated by CFD (Computational Fluid Dynamics), with a focus on different injection strategies. In the PPCI combustion mode, NG was injected early in the compression stroke and premixed with air, and then the pilot diesel was injected to cause ignition near the top dead center. This combustion mode produced a faster heat release rate, but the HC emissions were higher, and the combustion efficiency was lower. In the HPDI combustion mode, the diesel was injected first and ignited, and then the NG was injected into the flame. This combustion mode resulted in higher emissions of NOx and soot, with a diffusion combustion in the cylinder. HC emissions significantly decreased. Compared with PPCI combustion, HPDI had a higher thermal efficiency.

Effects of combustor geometry on the combustion process of an RBCC combustor in high-speed ejector mode

2019 ◽  
Vol 33 (27) ◽  
pp. 1950330
Author(s):  
Taiyu Wang ◽  
Zhenguo Wang ◽  
Zun Cai ◽  
Jian Chen ◽  
Mingbo Sun ◽  
...  
Keyword(s):  
Supersonic Flow ◽  
Flow Field ◽  
Heat Release ◽  
Reaction Mechanisms ◽  
Total Pressure ◽  
High Speed ◽  
Combustion Process ◽  
Numerical Approach ◽  
Combined Cycle ◽  
Chemical Reaction Mechanisms

The combustion characteristics of high-speed ejector mode in a 2-dimensional strut-based RBCC (rocket-based combined cycle) combustor had been investigated numerically in a Mach 2.5 supersonic flow. The numerical approach had been validated by comparing numerical results with available experimental data. Besides, three different hydrogen-air chemical reaction mechanisms had also been compared. The effect of the combustor geometry on the combustion process was then discussed by analyzing the heat release distribution and flow field. It was found that the wall configuration, closeout angle of the converging location and converging ratio all have significant influences on the heat release distribution and flow field structures. It is demonstrated that a converging–diverging wall configuration is beneficial for the combustion process with significant heat release increase compared to the other wall configurations. In addition, the closeout angle of the converging location is also closely related to the combustion performance, and there exists an optimized closeout angle in a specific combustor geometry. It is also revealed that the major heat release region moves upstream obviously with increase in the converging ratio, leading to an enhanced combustion process. However, the converging ratio is still to be optimized to keep a balance between heat release increase and total pressure loss of the supersonic flow.

A fully analytical treatment of heat release in diesel engines

2003 ◽  
Vol 217 (8) ◽  
pp. 701-717 ◽  
Author(s):  
J G Hawley ◽  
F J Wallace ◽  
S Khalil-Arya
Keyword(s):  
Heat Release ◽  
Diesel Engines ◽  
Local Density ◽  
Combustion Process ◽  
Diffusion Combustion ◽  
Analytical Treatment ◽  
Validation Data ◽  
Torque Curve ◽  
Extensive Test ◽  
Further Development

The paper details a wholly analytical approach to heat release modelling. The approach is based on the diffusion combustion process which is specific to diesel engines operating under very high injection pressures. The combustion is subsequently controlled mainly by two items, the instantaneous fuel mass present in the cylinder charge and the local density of turbulent kinetic energy. Analytical solutions are developed for each. An extensive test series was undertaken, covering the limiting torque curve (LTC) between 1250 and 4000 r/min and utilizing a high-pressure common rail diesel engine to generate the necessary validation data. The validation exercise has shown the flexibility of this heat release modelling approach to be extremely accurate and suitable for further development.

Effects of Steam Injection Flow in Burner and Outside Water Tube to the Increasing of Boiler Temperature

2007 ◽  
Vol 7 (1 & 2) ◽  
pp. 120
Author(s):  
M. Djoni Bustan
Keyword(s):  
Human Life ◽  
Combustion Process ◽  
Production Capacity ◽  
Steam Injection ◽  
Oil Refinery ◽  
Specific Enthalpy ◽  
Maximum Pressure ◽  
Injection Flow ◽  
Electrical Generator ◽  
Generator Unit

Energy is an expensive basic need for human life, especially energy from fossils, such as crude oil, gas, and coal. In an oil refinery factory or electrical generator unit, where heat is most dominantly utilized, the boiler is used to generate steam. The main problem in a boiler is its uncompleted combustion process because of the incomplete ratio of air–fuel. This problem is caused by the addition of deposits or sealing inside and outside of the tube fire heater which will reduce the performance of fired heater. The objective of this research is to study the effect of steam flow variation on burner and tubing for increasing heat and temperature as well as the quality of steam. This research used a package boiler B&W series 1986 model which can be seen at an oil refinery factory or steam power electrical generator unit in Indonesia. This package boiler has 50kg/hours steam production capacity, qualified superheated steam, maximum pressure and temperature at 7kgs/cms2 and 700oC. Quantitatively, the achievable heat efficiency which corresponded to the temperature increase caused by the steam injection is 41.25% and the specific enthalpy is 12.07%.

scholarly journals The Effect of RME-1-Butanol Blends on Combustion, Performance and Emission of a Direct Injection Diesel Engine

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2941
Author(s):  
Wojciech Tutak ◽  
Arkadiusz Jamrozik ◽  
Karol Grab-Rogaliński
Keyword(s):  
Diesel Engine ◽  
Heat Release ◽  
Direct Injection ◽  
Specific Energy Consumption ◽  
Combustion Process ◽  
Constant Load ◽  
Combustion Stability ◽  
Performance And Emission ◽  
Energy Share ◽  
The Stability

The main objective of this study was assessment of the performance, emissions and combustion characteristics of a diesel engine using RME–1-butanol blends. In assessing the combustion process, great importance was placed on evaluating the stability of this process. Not only were the typical COVIMEP indicators assessed, but also the non-burnability of the characteristic combustion stages: ignition delay, time of 50% heat release and the end of combustion. The evaluation of the combustion process based on the analysis of heat release. The tests carried out on a 1-cylinder diesel engine operating at a constant load. Research and evaluation of the combustion process of a mixture of RME and 1-butanol carried out for the entire range of shares of both fuels up to 90% of 1-butanol energetic fraction. The participation of butanol in combustion process with RME increased the in-cylinder peak pressure and the heat release rate. With the increase in the share of butanol there was noted a decrease in specific energy consumption and an increase in engine efficiency. The share of butanol improved the combustion stability. There was also an increase in NOx emissions and decrease in CO and soot emissions. The engine can be power by blend up to 80% energy share of butanol.

scholarly journals Combustion Thermodynamics of Ethanol, n-Heptane, and n-Butanol in a Rapid Compression Machine with a Dual Direct Injection (DDI) Supply System

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2729
Author(s):  
Ireneusz Pielecha ◽  
Sławomir Wierzbicki ◽  
Maciej Sidorowicz ◽  
Dariusz Pietras
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Internal Combustion Engines ◽  
Direct Injection ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Injection System ◽  
Rapid Compression Machine ◽  
Process Indicators ◽  
Rapid Compression

The development of internal combustion engines involves various new solutions, one of which is the use of dual-fuel systems. The diversity of technological solutions being developed determines the efficiency of such systems, as well as the possibility of reducing the emission of carbon dioxide and exhaust components into the atmosphere. An innovative double direct injection system was used as a method for forming a mixture in the combustion chamber. The tests were carried out with the use of gasoline, ethanol, n-heptane, and n-butanol during combustion in a model test engine—the rapid compression machine (RCM). The analyzed combustion process indicators included the cylinder pressure, pressure increase rate, heat release rate, and heat release value. Optical tests of the combustion process made it possible to analyze the flame development in the observed area of the combustion chamber. The conducted research and analyses resulted in the observation that it is possible to control the excess air ratio in the direct vicinity of the spark plug just before ignition. Such possibilities occur as a result of the properties of the injected fuels, which include different amounts of air required for their stoichiometric combustion. The studies of the combustion process have shown that the combustible mixtures consisting of gasoline with another fuel are characterized by greater combustion efficiency than the mixtures composed of only a single fuel type, and that the influence of the type of fuel used is significant for the combustion process and its indicator values.

Vibration analysis and combustion parameter evaluation of CI engine based on Fourier Decomposition Method

2021 ◽  
pp. 146808742098819
Author(s):  
Wang Yang ◽  
Cheng Yong
Keyword(s):  
Vibration Analysis ◽  
Decomposition Method ◽  
Combustion Process ◽  
Pressure Rise ◽  
Maximum Pressure ◽  
Vibration Signals ◽  
Loop Control ◽  
Fourier Decomposition ◽  
Surface Vibration ◽  
Rise Rate

As a non-intrusive method for engine working condition detection, the engine surface vibration contains rich information about the combustion process and has great potential for the closed-loop control of engines. However, the measured engine surface vibration signals are usually induced by combustion as well as non-combustion excitations and are difficult to be utilized directly. To evaluate some combustion parameters from engine surface vibration, the tests were carried out on a single-cylinder diesel engine and a new method called Fourier Decomposition Method (FDM) was used to extract combustion induced vibration. Simulated and test results verified the ability of the FDM for engine vibration analysis. Based on the extracted vibration signals, the methods for identifying start of combustion, location of maximum pressure rise rate, and location of peak pressure were proposed. The cycle-by-cycle analysis of the results show that the parameters identified based on vibration and in-cylinder pressure have the similar trends, and it suggests that the proposed FDM-based methods can be used for extracting combustion induced vibrations and identifying the combustion parameters.

scholarly journals The Synergy of Two Biofuel Additives on Combustion Process to Simultaneously Reduce NOx and PM Emissions

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2784
Author(s):  
Jerzy Cisek ◽  
Szymon Lesniak ◽  
Winicjusz Stanik ◽  
Włodzimierz Przybylski
Keyword(s):  
Heat Release ◽  
Combustion Rate ◽  
Combustion Process ◽  
The Other ◽  
Fuel Additive ◽  
Exhaust Gas ◽  
Synergy Effect ◽  
Engine Exhaust ◽  
Other Hand ◽  
Heat Released

The article presents the results of research on the influence of two fuel additives that selectively affect the combustion process in a diesel engine cylinder. The addition of NitrON® reduces the concentration of nitrogen oxides (NOx), due to a reduction in the kinetic combustion rate, at the cost of a slight increase in the concentration of particulate matter (PM) in the engine exhaust gas. The Reduxco® additive reduces PM emissions by increasing the diffusion combustion rate, while slightly increasing the NOx concentration in the engine exhaust gas. Research conducted by the authors confirmed that the simultaneous use of both of these additives in the fuel not only reduced both NOx and PM emissions in the exhaust gas but additionally the reduction of NOx and PM emissions was greater than the sum of the effects of these additives—the synergy effect. Findings indicated that the waveforms of the heat release rate (dQ/dα) responsible for the emission of NOx and PM in the exhaust gas differed for the four tested fuels in relation to the maximum value (selectively and independently in the kinetic and diffusion stage), and they were also phase shifted. Due to this, the heat release process Q(α) was characterized by a lower amount of heat released in the kinetic phase compared to fuel with NitrON® only and a greater amount of heat released in the diffusion phase compared to fuel with Reduxco® alone, which explained the lowest NOx and PM emissions in the exhaust gas at that time. For example for the NOx concentration in the engine exhaust: the Nitrocet® fuel additive (in the used amount of 1500 ppm) reduces the NOx concentration in the exhaust gas by 18% compared to the base fuel. The addition of a Reduxco® catalyst to the fuel (1500 ppm) unfortunately increases the NOx concentration by up to 20%. On the other hand, the combustion of the complete tested fuel, containing both additives simultaneously, is characterized, thanks to the synergy effect, by the lowest NOx concentration (reduction by 22% in relation to the base). For example for PM emissions: the Nitrocet® fuel additive does not significantly affect the PM emissions in the engine exhaust (up to a few per cent compared to the base fuel). The addition of a Reduxco® catalyst to the fuel greatly reduces PM emissions in the engine exhaust, up to 35% compared to the base fuel. On the other hand, the combustion of the complete tested fuel containing both additives simultaneously is characterized by the synergy effect with the lowest PM emission (reduction of 39% compared to the base fuel).

scholarly journals Experimental and Simulation of Diesel Engine Fueled with Biodiesel with Variations in Heat Loss Model

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1622
Author(s):  
Daniel Romeo Kamta Legue ◽  
Zacharie Merlin Ayissi ◽  
Mahamat Hassane Babikir ◽  
Marcel Obounou ◽  
Henri Paul Ekobena Fouda
Keyword(s):  
Heat Release ◽  
Heat Loss ◽  
Heat Release Rate ◽  
Release Rate ◽  
Diffusion Combustion ◽  
Cylinder Wall ◽  
Compression Ignition Engine ◽  
Experimental Conditions ◽  
Load Range ◽  
Combustion Phase

This study presents an experimental investigation and thermodynamic 0D modeling of the combustion of a compression-ignition engine, fueled by an alternative fuel based on neem biodiesel (B100) as well as conventional diesel (D100). The study highlights the effects of the engine load at 50%, 75% and 100% and the influence of the heat loss models proposed by Woschni, Eichelberg and Hohenberg on the variation in the cylinder pressure. The study shows that the heat loss through the cylinder wall is more pronounced during diffusion combustion regardless of the nature of the fuels tested and the load range required. The cylinder pressures when using B100 estimated at 89 bars are relatively higher than when using D100, about 3.3% greater under the same experimental conditions. It is also observed that the problem of the high pressure associated with the use of biodiesels in engines can be solved by optimizing the ignition delay. The net heat release rate remains roughly the same when using D100 and B100 at 100% load. At low loads, the D100 heat release rate is higher than B100. The investigation shows how wall heat losses are more pronounced in the diffusion combustion phase, relative to the premix phase, by presenting variations in the curves.

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