49,532 research outputs found
Analysis of rocket engine injection combustion processes
Mixing methodology improvement for the JANNAF DER and CICM injection/combustion analysis computer programs was accomplished. ZOM plane prediction model development was improved for installation into the new standardized DER computer program. An intra-element mixing model developing approach was recommended for gas/liquid coaxial injection elements for possible future incorporation into the CICM computer program
Interfacial shear in adiabatic downward gas/liquid co-current annular flow in pipes
Interfacial friction is one of the key variables for predicting annular two-phase flow behaviours in vertical pipes. In order to develop an improved correlation for interfacial friction factor in downward co-current annular flow, the pressure gradient, film thickness and film velocity data were generated from experiments carried out on Cranfield University’s Serpent Rig, an air/water two-phase vertical flow loop of 101.6 mm internal diameter. The air and water superficial velocity ranges used are 1.42–28.87 and 0.1–1.0 m/s respectively. These correspond to Reynolds number values of 8400–187,000 and 11,000–113,000 respectively. The correlation takes into account the effect of pipe diameter by using the interfacial shear data together with dimensionless liquid film thicknesses related to different pipe sizes ranging from 10 to 101.6 mm, including those from published sources by numerous investigators. It is shown that the predictions of this new correlation outperform those from previously reported studies
Effervescent Breakup and Combustion of Liquid Fuels: Experiment and Modelling
Tato práce se zaměřuje na oblast effervescentnĂch sprejĹŻ a jejich aplikace na kapalnĂ© spalovánĂ s dĹŻrazem na prĹŻmyslovĂ© spalovacĂ komory. Oba aspekty – modelovánĂ a experiment – jsou Ĺ™ešeny. Práce obsahuje obecnĂ˝ Ăşvod, ve kterĂ©m jsou vysvÄ›tleny základnĂ jevy rozpadu kapaliny a vĂĹ™ivĂ©ho spalovánĂ a dále je pĹ™edstavena effervescentnĂ atomizace. PotĂ© jsou popsány pouĹľitĂ© experimentálnĂ postupy jak pro měřenĂ spreje, tak pro měřenĂ tepelnĂ˝ch tokĹŻ do stÄ›n pĹ™i spalovánĂ. V následujĂcĂ kapitole jsou popsány numerickĂ© modely a jejich podstata je vysvÄ›tlena. Jsou zde uvedeny modely pro rozpad spreje, turbulenci a spalovánĂ pouĹľitĂ© bÄ›hem vĂ˝zkumu. VlastnĂ vĂ˝sledky práce jsou uvedeny formou samostatnĂ˝ch ÄŤlánkĹŻ (vydanĂ˝ch nebo pĹ™ijatĂ˝ch) s dodateÄŤnou částĂ vÄ›novanou nepublikovanĂ˝m relevantnĂm vĂ˝sledkĹŻm. Bylo zjištÄ›no, Ĺľe standardnĂ modely sprejĹŻ jsou do jistĂ© mĂry schopny popsat effervescentnĂ spreje. NicmĂ©nÄ› aby bylo moĹľnĂ© predikovat plamen kapalnĂ©ho spreje, jsou zapotĹ™ebĂ detailnÄ›jšà modely sprejĹŻ, kterĂ© dokážà pĹ™esnÄ› zachytit zmÄ›nu prĹŻmÄ›rĹŻ kapek v radiálnĂm a axiálnĂm smÄ›ru. ExperimentálnĂ měřenĂ effervescentnĂch sprejĹŻ bylo provedeno pomocĂ navrhnutĂ© metodiky. VĂ˝sledky měřenĂ byly analyzovány s dĹŻrazem na radiálnĂ a axiálnĂ vĂ˝voj prĹŻmÄ›rĹŻ kapek a nÄ›kterĂ© novĂ© jevy byly popsány. NepĹ™Ămá ĂşmÄ›rnost mezi gas-liquid-ratio a stĹ™ednĂm prĹŻmÄ›rem kapek byla potvrzena. Dále by popsán jev, kdy pro rĹŻznĂ© axiálnĂ vzdálenosti kterĂ© dojde k ĂşplnĂ©mu pĹ™evrácenĂ závislosti stĹ™ednĂho prĹŻmÄ›ru na axiálnĂ vzdálenosti. V závÄ›ru je uvedeno shrnutĂ, kterĂ© rekapituluje hlavnĂ vĂ˝sledkĹŻ a závÄ›ry. V závÄ›reÄŤnĂ˝ch poznámkách je nastĂnÄ›n moĹľnĂ˝ budoucĂ postup. ExperimentálnĂ data pro ověřovánĂ budoucĂch effervescentnĂch modelĹŻ jsou poskytnuta.This thesis presents an investigation of effervescent sprays and their application to spray combustion with emphasis on large-scale combustors. Both aspects – modelling and experiment – are addressed. The thesis contains a general introductory part, where underlying phenomena of spray forming and turbulent combustion are explained and effervescent atomization is presented. Then, adopted experimental approaches are described both for the spray measurement and for the measurement of wall heat fluxes during combustion experiments. In the following chapter numerical models and their philosophy is discussed. Models for spray formation, turbulence and combustion adopted during the research are introduced and explained. The actual results of the thesis are presented in form of separate papers (published or accepted for publication) with an additional section devoted to unpublished relevant results. It is found that standard spray models can to some extent represent effervescent sprays. However, in order to predict a spray flame more detailed spray models are needed in order to describe accurately radial and axial variations of drop sizes. Numerous experimental measurements of effervescent sprays are performed using a proposed methodology. Drop size data are analysed with emphasis on radial and axial drop size evolutions and some new phenomena are described. The inverse relationship between gas-liquid-ratio and mean diameter has been confirmed. Moreover a complete reversal in radial mean diameter trends for various axial locations has been described. Finally, a result summary is put forward that recapitulates the main accomplishments and conclusions. In the closing remarks possible future research is outlined. Experimental data for future effervescent model validations are disclosed.
Investigation of spray characteristics for flashing injection of fuels containing dissolved air and superheated fuels
The flow, atomization and spreading of flashing injector flowing liquids containing dissolved gases (jet/air) as well as superheated liquids (Freon II) were considered. The use of a two stage expansion process separated by an expansion chamber, ws found to be beneficial for flashing injection particularly for dissolved gas systems. Both locally homogeneous and separated flow models provided good predictions of injector flow properties. Conventional correlations for drop sizes from pressure atomized and airblast injectors were successfully modified, using the separated flow model to prescribe injector exit conditions, to correlate drop size measurements. Additional experimental results are provided for spray angle and combustion properties of sprays from flashing injectors
Space processes for extended low-G testing
Results of an investigation of verifying the capabilities of space processes in ground based experiments at low-g periods are presented. Limited time experiments were conducted with the processes. A valid representation of the complete process cycle was achieved at low-g periods ranging from 40 to 390 seconds. A minimum equipment inventory, is defined. A modular equipment design, adopted to assure low cost and high program flexibility, is presented as well as procedures and data established for the synthesis and definition of dedicated and mixed rocket payloads
Physics-based prognostic modelling of filter clogging phenomena
In industry, contaminant filtration is a common process to achieve a desired level of purification, since contaminants in liquids such as fuel may lead to performance drop and rapid wear propagation. Generally, clogging of filter phenomena is the primary failure mode leading to the replacement or cleansing of filter. Cascading failures and weak performance of the system are the unfortunate outcomes due to a clogged filter. Even though filtration and clogging phenomena and their effects of several observable parameters have been studied for quite some time in the literature, progression of clogging and its use for prognostics purposes have not been addressed yet. In this work, a physics based clogging progression model is presented. The proposed model that bases on a well-known pressure drop equation is able to model three phases of the clogging phenomena, last of which has not been modelled in the literature yet. In addition, the presented model is integrated with particle filters to predict the future clogging levels and to estimate the remaining useful life of fuel filters. The presented model has been implemented on the data collected from an experimental rig in the lab environment. In the rig, pressure drop across the filter, flow rate, and filter mesh images are recorded throughout the accelerated degradation experiments. The presented physics based model has been applied to the data obtained from the rig. The remaining useful lives of the filters used in the experimental rig have been reported in the paper. The results show that the presented methodology provides significantly accurate and precise prognostic results
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