scholarly journals Study on Combustion Properties of Aviation Carpet under Low Ambient Pressure

2020 ◽  
Vol 38 (2) ◽  
pp. 319-324
Author(s):  
Xuhong Jia ◽  
Xiaoguang Yang ◽  
Song Huang ◽  
Maoyong Zhi ◽  
Xinhua Zhu
Keyword(s):  
Carbon Monoxide ◽  
Volume Fraction ◽  
Ambient Pressure ◽  
Ignition Time ◽  
Normal Pressure ◽  
Low Pressure ◽  
Combustion Properties ◽  
Civil Aircraft ◽  
Transport Condition ◽  
Normal Transport

The flame-retardant materials in the cabin of civil aircraft is possible to induce fire accident, which can cause certain threat to the operation safety of aircraft. The cabin pressure of civil aircraft is generally maintained at 75~84 kPa under normal transport condition, and the combustion behavior of aviation carpet will change under this pressure. Combustion properties of an aviation carpet, selected from civil aircraft, were studied at Guanghan City (520 m altitude) and Kangding airport (4290 m altitude), Sichuan province of China in this work, respectively. The results showed that the smoke density of the aviation carpets increased sharply and the decreasing rate of the oxygen volume fraction became more quickly under low pressure. Furthermore, the rising rate of carbon dioxide volume fraction also became rapidly with the decrease of the ambient pressure. The content of the carbon monoxide under low pressure was lower than that under normal pressure at the beginning of the combustion. However, the carbon monoxide production increased sharply when the combustion lasted for 4 minutes. In addition, the ignition time of the aviation carpet was shorter under low pressure.

scholarly journals Experimental Study for Biogas Upgrading by Water Scrubbing under Low Pressure

2015 ◽  
Vol 9 (1) ◽  
pp. 34-38 ◽  
Author(s):  
Li Huang ◽  
Chunyao Qing ◽  
Hongge Tao ◽  
YanJin Wang ◽  
Xinping Liu
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Fraction ◽  
Removal Rate ◽  
Rural China ◽  
Water Flow Rate ◽  
Normal Pressure ◽  
Low Pressure ◽  
Flow Rate Ratio ◽  
Biogas Upgrading

Biogas fuels is effective to alleviate the problem of energy shortage and ecological environment for sustainable developing in rural China. But CO2 and other impurity in biogas will impede its use for generating high quality energy. In this paper, water scrubbing technology has been used for biogas upgrading under low scrubbing pressure, and the influence of CO2 removal rate and CO2 solubility caused by different experimental parameters including the feed gas flow rate, water flow rate and scrubbing pressure were examined, and the experiments dates were analyzed by SPSS17.0, and then the corresponding mathematical models were established. The result showed that, under the three scrubbing pressure level(with normal pressure, 0. 15 Mpa and 0. 3 Mpa), the improve rate of CH volume fraction increased about 15%, and CO2 volume fraction declined about 20% when scrubbing pressure raised in each level, and under 0.3 Mpa of pressure, with 0.28 of flow rate ratio of gas and liquid, CO2 removal rate gotten as high as 73.14%.So the method of water scrubbing under low pressure could be used for biogas preliminary upgrading processing when there is rich of water.

scholarly journals Flow and Noise Characteristics of Centrifugal Fan in Low Pressure Environment

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 985 ◽  
Author(s):  
Xilong Zhang ◽  
Yongliang Zhang ◽  
Chenggang Lu
Keyword(s):  
Ambient Pressure ◽  
Characteristic Curve ◽  
Normal Pressure ◽  
Low Pressure ◽  
Centrifugal Fan ◽  
Working Process ◽  
Fan Noise ◽  
Environmental Pressure ◽  
Noise Characteristics ◽  
Consumption Curve

The influence of low-pressure environment on centrifugal fan’s flow and noise characteristics was studied experimentally and numerically. A testbed was established to conduct the experimental test on the performance of a centrifugal fan, and the characteristic curve and power consumption curve of the fan under different pressure were obtained. Then the simulation model of the centrifugal fan was established, which was used to simulate the working process of centrifugal fan under different negative pressures. The results showed that the total pressure and static pressure of the fan decrease with the decrease of the ambient pressure. The total and static pressures of the fan under 60 kPa pressure condition decreased by 42.3% and 38.3%, respectively, compared with those of fan under the normal pressure. The main reason for this phenomenon is that the decrease of the environmental pressure leads to the decrease of air density. Besides, with the drop of environmental pressure, the sound pressure and sound power of the fan noise decreases.

scholarly journals Springtime daily variations in lower-tropospheric ozone over east Asia: the role of cyclonic activity and pollution as observed from space with IASI

2015 ◽  
Vol 15 (18) ◽  
pp. 10839-10856 ◽  
Author(s):  
G. Dufour ◽  
M. Eremenko ◽  
J. Cuesta ◽  
C. Doche ◽  
G. Foret ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
East Asia ◽  
Tropospheric Ozone ◽  
North China Plain ◽  
North China ◽  
Low Pressure ◽  
The North ◽  
The North China Plain ◽  
Co Observations ◽  
Low Pressure Systems

Abstract. We use satellite observations from IASI (Infrared Atmospheric Sounding Interferometer) on board the MetOp-A satellite to evaluate the springtime daily variations in lower-tropospheric ozone over east Asia. The availability of semi-independent columns of ozone from the surface up to 12 km simultaneously with CO columns provides a powerful observational data set to diagnose the processes controlling tropospheric ozone enhancement on synoptic scales. By combining IASI observations with meteorological reanalyses from ERA-Interim, we develop an analysis method based only on IASI ozone and CO observations to identify the respective roles of the stratospheric source and the photochemical source in ozone distribution and variations over east Asia. The succession of low- and high-pressure systems drives the day-to-day variations in lower-tropospheric ozone. A case study analysis of one frontal system and one cut-off low system in May 2008 shows that reversible subsiding and ascending ozone transfers in the upper-troposphere–lower-stratosphere (UTLS) region, due to the tropopause perturbations occurring in the vicinity of low-pressure systems, impact free and lower-tropospheric ozone over large regions, especially north of 40° N, and largely explain the ozone enhancement observed with IASI for these latitudes. Irreversible stratosphere–troposphere exchanges of ozone-rich air masses occur more locally in the southern and southeastern flanks of the trough. The contribution to the lower-tropospheric ozone column is difficult to dissociate from the tropopause perturbations generated by weather systems. For regions south of 40° N, a significant correlation has been found between lower-tropospheric ozone and carbon monoxide (CO) observations from IASI, especially over the North China Plain (NCP). Considering carbon monoxide observations as a pollutant tracer, the O3–CO correlation indicates that the photochemical production of ozone from primary pollutants emitted over such large polluted regions significantly contributes to the ozone enhancements observed in the lower troposphere via IASI. When low-pressure systems circulate over the NCP, stratospheric and pollution sources play a concomitant role in the ozone enhancement. IASI's 3-D observational capability allows the areas in which each source dominates to be determined. Moreover, the studied cut-off low system has enough potential convective capacity to uplift pollutants (ozone and CO) and to transport them to Japan. The increase in the enhancement ratio of ozone to CO from 0.16 on 12 May over the North China Plain to 0.28 over the Sea of Japan on 14 May indicates photochemical processing during the plume transport.

scholarly journals Experimental study on the effect of spray cone angle on the characteristics of horizontal jet spray flame under sub-atmospheric pressure

2020 ◽  
Vol 24 (5 Part A) ◽  
pp. 2941-2952 ◽  
Author(s):  
Kai Xie ◽  
Xingqi Qiu ◽  
Yunjing Cui ◽  
Jianxin Wang
Keyword(s):  
Atmospheric Pressure ◽  
Cone Angle ◽  
Flame Temperature ◽  
Normal Pressure ◽  
Low Pressure ◽  
Dimensionless Temperature ◽  
Thermal Imager ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Matlab Programming

The burning state of a plateau environment is attracting more and more attention. In this paper, in order to have a deeper scientific understanding of diesel spray combustion and the characteristics of a flame under different spray cone angles in a plateau environment, experiments were carried out in a low pressure chamber. The flame morphology was recorded by a high speed video instrument, and the temperature change was recorded by a thermal imager and thermocouples. The MATLAB programming was used to process the video image of the flame, and the probability of its binarization was calculated. The results indicate that the flame becomes longer and wider under different pressures with the same spray angle. The variation is more pronounced at a smaller spray taper angle. The flame uplifted height characteristic is mainly negatively related to the atmospheric pressure. According to the normalized flame temperature and the dimensionless horizontal projection, the length can be divided into three regions. In the region of buoyancy flame, the dimensionless temperature varies with sub-atmospheric pressure more than with normal pressure. In addition, under different spray cone angle conditions, the law of variation in the normalized flame temperature under sub-atmospheric pressure is exactly opposite to that under normal pressure. This study is of great significance to the scientific research on flames in a low pressure environment, and the design of different fuel nozzles for application in a plateau environment.

High-Pressure Synthesis and Crystal Structure of the New Orthorhombic Polymorph β-HgB4O7

2005 ◽  
Vol 60 (8) ◽  
pp. 815-820 ◽  
Author(s):  
Holger Emme ◽  
Matthias Weil ◽  
Hubert Huppertz
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ambient Pressure ◽  
Normal Pressure ◽  
High Pressure Phase ◽  
Synthesis And Crystal Structure ◽  
Space Group ◽  
High Pressure Synthesis ◽  
Pressure Synthesis ◽  
Pressure Phase

The new orthorhombic polymorph β-HgB4O7 has been synthesized under high-pressure and hightemperature conditions in a Walker-type multianvil apparatus at 7.5 GPa and 600 °C. β-HgB4O7 is isotypic to the known ambient pressure phases MB4O7 (M = Sr, Pb, Eu) and the high-pressure phase β-CaB4O7 crystallizing with two formula units in the space group Pmn21 with lattice parameters a = 1065.6(2), b = 438.10(9), and c = 418.72(8) pm. The relation of the crystal structure of the high-pressure phase β-HgB4O7 to the normal pressure phase α-HgB4O7 as well as the relation to the isotypic phases MB4O7 (M = Sr, Pb, Eu) and β-CaB4O7 are discussed.

PRESSURE-INDUCED ELECTRONIC PHASE TRANSITIONS AND SUPERCONDUCTIVITY IN TITANIUM

2009 ◽  
Vol 23 (05) ◽  
pp. 723-741 ◽  
Author(s):  
K. IYAKUTTI ◽  
C. NIRMALA LOUIS ◽  
S. ANURATHA ◽  
S. MAHALAKSHMI
Keyword(s):  
High Pressure ◽  
Band Structure ◽  
Fermi Surface ◽  
High Pressures ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Normal Pressure ◽  
Orbital Method ◽  
Superconducting Transition ◽  
Electronic Band

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium ( Ti ) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB LMTO), we predict a phase transformation sequence of α( hcp ) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis, we predict a δ (distorted bcc) phase which is not stable at any high pressures. At ambient pressure, the superconducting transition occurs at 0.354 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp–Ti . On further increase of pressure, Tc begins to decrease at a rate of 1.464 K/Mbar. The highest value of Tc(P) estimated is 5.043 K for hcp–Ti , 4.538 K for ω– Ti and 4.85 K for bcc – Ti . From this, it is inferred that the maximum value of Tc(P) is rather insensitive to the crystal structure of Ti . The nonlinearities in Tc(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω- Ti > hcp - Ti > bcc- Ti > γ- Ti .

Gasoline engine performance simulation of water injection and low-pressure exhaust gas recirculation using tabulated chemistry

2020 ◽  
Vol 21 (10) ◽  
pp. 1857-1877 ◽  
Author(s):  
Tim Franken ◽  
Fabian Mauss ◽  
Lars Seidel ◽  
Maike Sophie Gern ◽  
Malte Kauf ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Nitrogen Oxide ◽  
Water Injection ◽  
Exhaust Gas Recirculation ◽  
Low Pressure ◽  
Exhaust Gas ◽  
Nitrogen Oxide Emissions ◽  
Direct Water Injection ◽  
Tabulated Chemistry ◽  
Gas Recirculation

This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at λ = 1 at full load using water–fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air–fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air–fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions.

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