04/00408 An evaluation method for quality of air-fuel mixture distribution and movement in combustion chamber of DISI engine using CFD

2004 ◽  
Vol 45 (1) ◽  
pp. 48
2021 ◽  
Vol 2 (01) ◽  
pp. 1-6
Author(s):  
Irwansyah Irwansyah ◽  
Muhammad Arsad Al Banjari ◽  
Feddy Wanditya Setiawan

Ideally, the combustion system system in the combustion chamber, this is an alarm in order to get the right combustion results and of course will make the motorcycle power with the right fuel consumption too. There are at least 3 (three) important factors that must be met by the combustion system in the combustion motorbike, especially for gasoline-type automatic motorbikes. These three factors include the existence of an ideal fuel and air mixture (good air-fuel mixture), the right timing of business performance in producing spark plug spark quality (good spark) and good combustion chamber (good compression). An air-fuel mixture that can produce a homogeneous mixing of fuel and air. The acquisition of perfect combustion is directly proportional to the quality of a good type of spark plug cable. The ability of the type of spark plug cable must be able to support high electric current processes to produce the ideal spark. In this study, the type of business cable used is the brand that is in the market, namely proteck, extreme, hitachi and standard cable types. Performed variation testing 4 (four) types of spark plug cables. The test results show the best engine performance of a gasoline-fueled automatic motorbike using extreme spark plug cables, with a torque of 5,669 Nm at 7854 rpm and a power of 6,252 hp at 7854 rpm


Author(s):  
A. P. Shaikin ◽  
I. R. Galiev

The article analyzes the influence of chemical composition of hythane (a mixture of natural gas with hydrogen) on pressure in an engine combustion chamber. A review of the literature has showed the relevance of using hythane in transport energy industry, and also revealed a number of scientific papers devoted to studying the effect of hythane on environmental and traction-dynamic characteristics of the engine. We have studied a single-cylinder spark-ignited internal combustion engine. In the experiments, the varying factors are: engine speed (600 and 900 min-1), excess air ratio and hydrogen concentration in natural gas which are 29, 47 and 58% (volume).The article shows that at idling engine speed maximum pressure in combustion chamber depends on excess air ratio and proportion hydrogen in the air-fuel mixture – the poorer air-fuel mixture and greater addition of hydrogen is, the more intense pressure increases. The positive effect of hydrogen on pressure is explained by the fact that addition of hydrogen contributes to increase in heat of combustion fuel and rate propagation of the flame. As a result, during combustion, more heat is released, and the fuel itself burns in a smaller volume. Thus, the addition of hydrogen can ensure stable combustion of a lean air-fuel mixture without loss of engine power. Moreover, the article shows that, despite the change in engine speed, addition of hydrogen, excess air ratio, type of fuel (natural gas and gasoline), there is a power-law dependence of the maximum pressure in engine cylinder on combustion chamber volume. Processing and analysis of the results of the foreign and domestic researchers have showed that patterns we discovered are applicable to engines of different designs, operating at different speeds and using different hydrocarbon fuels. The results research presented allow us to reduce the time and material costs when creating new power plants using hythane and meeting modern requirements for power, economy and toxicity.


2014 ◽  
Vol 672-674 ◽  
pp. 1441-1446 ◽  
Author(s):  
Yu Qiang Ou ◽  
Le Feng Cheng ◽  
Jian Zhong Wen ◽  
Xuan Yu Qiu ◽  
Tao Yu

Research on reliability of distribution network has very important meaning and function to ensure the quality of power supply. This paper introduces some basic concepts of reliability in distribution network, including distribution network reliability definition, task and index. The classical reliability evaluation method was reviewed, and focused on specific distribution network, an example analysis was given, and specific reliability evaluation indexes were calculated. Finally, the future development of distribution network reliability evaluation was made a simple prospect.


2021 ◽  
Vol 50 (1) ◽  
pp. 79-87
Author(s):  
R. Z. Kavtaradze ◽  
A. M. Kondratev ◽  
Ch. Rongrong ◽  
Ch. Citian ◽  
S. Baigang ◽  
...  

2021 ◽  
Vol 12 ◽  
pp. 528
Author(s):  
Yoshimichi Sato ◽  
Toshiki Endo ◽  
Shingo Kayano ◽  
Hitoshi Nemoto ◽  
Kazuki Shimada ◽  
...  

Background: The subcallosal artery (ScA) is a single dominant artery arising from the anterior communicating artery. Its injury causes amnesia and cognitive disturbance. The conventional computed tomographic angiography (C-CTA) is a common evaluation method of the intracranial artery. However, to image tinny perforating arteries such as the ScA is technically demanding for C-CTA. The purpose of this study is to investigate whether the ultra-high-resolution CTA (UHR-CTA) could image the ScA better than C-CTA. UHR-CTA became available in clinical practice in 2017. Its novel features are the improvement of the detector system and a small X-ray focus. Methods: Between April 2019 and May 2020, 77 and 49 patients who underwent intracranial UHR-CTA and C-CTA, respectively, were enrolled in this study. Two board-certified neurosurgeons participated as observers to identify the ScA based on UHR-CTA and C-CTA images. Results: UHR-CTA and C-CTA detected the ScA in 56–58% and 30–40% of the patients, respectively. In visualization of the ScA, UHR-CTA was better than C-CTA (P < 0.05, Fisher’s exact test). Between the two observers, the Cohen’s kappa coefficient was 0.77 for UHR-CTA and 0.78 for C-CTA. Conclusions: UHR-CTA is a simple and accessible method to evaluate intracranial vasculature. Visualization of the ScA with UHR-CTA was better than that with C-CTA. The high quality of UHR-CTA could provide useful information in the neurosurgery field.


Author(s):  
Xiaoqin Zhang ◽  
Shengxin Wang ◽  
Yanling Cao ◽  
Guangqi Chen

There are two major problems in the evaluation of the teaching quality of English writing: the weak logic of the evaluation system and the low reliability of the evaluation model. To solve the problems, this paper put forward an evaluation method for the teaching quality of English writing based on the analytical hierarchy process (AHP). Firstly, the authors reviewed the current evaluation methods for the teaching quality of English writing. Next, hierarchical evaluation systems were established for the teaching quality of English writing from the perspectives of teachers and students, respectively. After that, the AHP method and the grey theory were introduced to set up an evaluation model for the teaching quality of English writing. Finally, several strategies were presented to improve the teaching quality of English writing. The proposed evaluation systems and model enriched the theories on teaching quality evaluation of English writing, and promoted the teaching quality of English writing.


Author(s):  
Tomáš Konderla ◽  
Václav Klepáč

The article points out the possibilities of using Hidden Markov model (abbrev. HMM) for estimation of Value at Risk metrics (abbrev. VaR) in sample. For the illustration we use data of the company listed on Prague Stock Exchange in range from January 2011 to June 2016. HMM approach allows us to classify time series into different states based on their development characteristic. Due to a deeper shortage of existing domestic results or comparison studies with advanced volatility governed VaR forecasts we tested HMM with univariate ARMA‑GARCH model based VaR estimates. The common testing via Kupiec and Christoffersen procedures offer generalization that HMM model performs better that volatility based VaR estimation technique in terms of accuracy, even with the simpler HMM with normal‑mixture distribution against previously used GARCH with many types of non‑normal innovations.


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