scholarly journals Numerical Study on the Gas Leakage and Dispersion at the Street Intersection of a Building Group

2020 ◽  
Vol 123 (3) ◽  
pp. 1247-1266
Author(s):  
Weitao Zhang ◽  
Mengqi Liu ◽  
Kaiyi Wang ◽  
Fan Zhang ◽  
Lei Hou
Keyword(s):  
Numerical Study ◽  
Gas Leakage ◽  
Street Intersection

Evaluation of the Effect of Gas Leakage on Operation of an Optical Engine

2010 ◽  
Author(s):  
E. Kapusuz ◽  
B. Ekici
Keyword(s):  
Gas Flow ◽  
Combustion Engine ◽  
Numerical Study ◽  
Mass Loss Rate ◽  
Ic Engine ◽  
Gas Leakage ◽  
Engine Model ◽  
Optical Engine ◽  
Laser Diagnostic ◽  
Flow Through

An experimental and numerical study is carried out to evaluate the significance of gas leakage for a non-lube optically accessible internal combustion engine and to obtain estimation for the gas flow out of the combustion chamber at each engine cycle and its effect on the in-cylinder component states during optical engine’s operation. Attention is paid to blow-by and circumferential flow through the gaps between the piston rings and the liner. Optical engines are typically operated without lubrication to avoid window fouling and generation of fluorescence by oil particles that interfere with laser diagnostic signals, in view of this circumstance significant blow-by is expected in optical engines due to lack of “wet-seal” on the cylinder walls which permits circumferential flow of gases through the piston ring pack region resulting in increased blow-by. Semi analytical model estimating the mass loss rate is incorporated into zero dimensional thermodynamic IC engine model which simulates in-cylinder processes. Predicted results are compared for leaking and non-leaking engine simulations.

scholarly journals Numerical study of the physical processes of gas leakage in the compression ring in diesel engines

2021 ◽  
Vol 2118 (1) ◽  
pp. 012016
Author(s):  
J A Pabón León ◽  
J P Rojas Suárez ◽  
M S Orjuela Abril
Keyword(s):  
Numerical Model ◽  
Internal Combustion Engines ◽  
Numerical Study ◽  
Cylinder Liner ◽  
Combustion Engines ◽  
Combustion Gases ◽  
Gas Leakage ◽  
Lubrication Film ◽  
Compression Ring ◽  
Complex Mathematical Model

Abstract In this research, the construction of a numerical model is proposed for the analysis of the friction processes and the thickness of the lubrication film present in the compression ring of internal combustion engines. The model is built using MATLAB software, and three load conditions are used as reference (2 Nm, 4 Nm, and 6 Nm) with a rotation speed of 3600 rpm, which correspond to a stationary single-cylinder diesel engine. Comparison between model estimates and experimental results show that the development model could predict the actual engine conditions. The deviation between the numerical model and the experimental data was 17%. It was shown that the increase in engine load causes a 16% increase in the friction force of the compression ring, which implies a 50% increase in power loss due to friction processes. In general, the model developed allows the analysis of the friction processes in the compression ring and its effect on the lubrication film, considering the leakage of the combustion gases. In this way, the construction of a more complex mathematical model is achieved, which allows improving the precision in the analyzes related to the interaction between the compression ring and the cylinder liner.

A Gasless Reservoir Solution for Electro-Hydraulic Compact Drives With Two Prime Movers

2020 ◽  
Author(s):  
Søren Ketelsen ◽  
Damiano Padovani ◽  
Morten Kjeld Ebbesen ◽  
Torben Ole Andersen ◽  
Lasse Schmidt
Keyword(s):  
Control Strategy ◽  
Numerical Study ◽  
Mimo System ◽  
Chamber Pressure ◽  
Gas Leakage ◽  
Reservoir Volume ◽  
Reservoir Solution ◽  
Flow Imbalance ◽  
Prime Movers ◽  
Gas Volume

Abstract Due to an increased focus on improving the energy efficiency and compactness of hydraulic linear actuators, the electro-hydraulic compact drive (ECD) has received increased attention lately. In this study the ECD consists of variable-speed electric motors and fixed-displacement pumps, which are directly connected to the cylinder, thus controlling the linear motion in a throttleless manner. Furthermore, ECDs are self-contained systems, i.e. based on a fully enclosed oil circuit, in order to avoid external contamination and air to enter the system and to increase system compactness. Conventionally a low-pressure gas-loaded accumulator is used as an oil reservoir to compensate for the flow imbalance occurring whenever utilizing single-rod cylinders in closed systems. The accumulator pressure is to be kept relatively low to stay within the required limits governed by the permitted pump housing’s pressure. Generally, this pressure is not allowed to exceed 1–3 bar. To avoid violating this limitation, the gas volume must be significantly larger than the actual oil volume, which needs to be stored in the accumulator. This requirement decreases the obtainable compactness of the ECD, especially for systems with a large cylinder stroke. Furthermore, the accumulator represents a potential of gas leakage, which ultimately could result in the ECD being non-functional. This paper presents a gasless reservoir solution, improving the system compactness and avoiding the risk of gas leakage. The proposed solution is based on a bootstrap reservoir which is charged by the lowest cylinder chamber pressure. This strategy is feasible for the class of ECDs that is capable of controlling the lowest cylinder chamber pressure alongside the cylinder motion. An ECD consisting of two electric prime movers is considered as a case study. It is shown how the gasless reservoir may be integrated into the system, and an analysis of how this affects the operating range and the dynamic couplings of the system is presented. This leads to the derivation of a control strategy for the Multi-Input-Multi-Output (MIMO) system based on state decoupling, by defining virtual inputs to control virtual outputs. A numerical study suggests that the reservoir volume may be reduced by approximately 50% for the given system dimensions. The proposed control strategy shows good position tracking performance while also being able to control the reservoir pressure within the pre-defined limits of 1 to 3 bar.

scholarly journals Numerical Study of Fire Behavior Induced by Gas Leakage in Combined Cycle Power Plant

2015 ◽  
Vol 20 (2) ◽  
pp. 107-113
Author(s):  
Jaeyong Park ◽  
Kunhyuk Sung ◽  
Longnan Li ◽  
Jinwook Choi ◽  
Daejoong Kim ◽  
...  
Keyword(s):  
Power Plant ◽  
Numerical Study ◽  
Fire Behavior ◽  
Combined Cycle ◽  
Combined Cycle Power Plant ◽  
Gas Leakage

Physical and numerical study on the transition of gas leakage regime of ventilated cavitating flow

2021 ◽  
Vol 239 ◽  
pp. 109861
Author(s):  
Yafei Lv ◽  
Mengjie Zhang ◽  
Taotao Liu ◽  
Jie Chen ◽  
Biao Huang ◽  
...  
Keyword(s):  
Numerical Study ◽  
Cavitating Flow ◽  
Gas Leakage

scholarly journals A numerical study of harmful gas dispersion based on CALPUFF model

2020 ◽  
Vol 191 ◽  
pp. 03007
Author(s):  
Yanyan Lu
Keyword(s):  
Complex Terrain ◽  
Large Scale ◽  
Numerical Study ◽  
Meteorological Data ◽  
Impact Factors ◽  
Economic Losses ◽  
Chemical Transformations ◽  
Gas Dispersion ◽  
Gas Leakage

Severe gas leakage accidents occasionally happened during the exploitation of high-sulfur gas, the consequent harmful gas dispersion could seriously impact the air quality, cause large-scale casualties and economic losses. Therefore, people’s comprehensive understanding of harmful gas dispersion in both spatial and temporal dimensions should be improved. This paper takes gas well blowout accident in Kai County, China, as the case study, simulates and analyzes the dispersion characteristics of the leaked gas, mainly focuses on H2S. The CALPUFF model is applied to execute the experiment, the detailed meteorological data, complex terrain data, wet deposition and chemical transformations are all under consideration. The result shows that due to different impact factors, such as complex terrain and gas density variations, H2S exposure risk was higher in the valley area than that on the mountain, which also explains why Xiaoyang and Gaowang villages have a great number of casualties. Besides, the analysis result is basically consistent with the historical local news and reported data, which demonstrated that our case study of H2S gas dispersion simulation is reasonable and reliable.

Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,
Keyword(s):  
Numerical Study ◽  
Low Frequency ◽  
Lennard Jones
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