{"id":12231,"date":"2017-09-18T10:30:21","date_gmt":"2017-09-18T08:30:21","guid":{"rendered":"https:\/\/mag.ebmpapst.com\/en\/?p=12231"},"modified":"2024-03-12T17:55:22","modified_gmt":"2024-03-12T16:55:22","slug":"the-formula-for-flow-rate","status":"publish","type":"post","link":"https:\/\/mag.ebmpapst.com\/en\/products\/fans\/the-formula-for-flow-rate_12231\/","title":{"rendered":"The formula for flow rate"},"content":{"rendered":"

Stefan Magerl (left), Plat\u00adform Devel\u00adop\u00adment engi\u00adneer at ebm-papst Land\u00adshut and Remo Fedele (right), Advanced Devel\u00adop\u00adment engi\u00adneer at ebm-papst Mulfingen<\/p><\/div><\/div>\n

In die-casting, the molten metal is pressed into a mold at high velocity and under great pres\u00adsure. The velocity of the molten metal in the gate vg is usually between 30 and 60 m\/s. Casting pres\u00adsures attain values of between 400 and 800 bar. A high mold filling rate and high pres\u00adsures make it possible to produce cast\u00adings with high dimen\u00adsional accu\u00adracy and extremely good surface prop\u00ader\u00adties. The specific casting pres\u00adsure occurs in the cavity of the perma\u00adnent mold. The higher this is, the higher will be the gate velocity.<\/p>\n

When calcu\u00adlating the casting pres\u00adsure it is however impor\u00adtant to make allowance for the fact that flow resis\u00adtances that have to be over\u00adcome occur at changes in cross-section and direc\u00adtion, at corners, at edges and on account of wall rough\u00adness. These resis\u00adtances are calcu\u00adlated using a dimen\u00adsion\u00adless quan\u00adtity, the resis\u00adtance coef\u00adfi\u00adcient \u03c6<\/span>. According to the Bernoulli equa\u00adtion p=( va2<\/sup>)\/(2 \u03c6<\/span2<\/sup>), a rela\u00adtion\u00adship exists between the metal pres\u00adsure and the gate velocity or flow rate. At low velocity there is a risk of solid\u00adi\u00adfi\u00adca\u00adtion in the gate before the secondary compres\u00adsion of the liquid metal takes effect in the mold cavity. It also results in irreg\u00adu\u00adlar\u00adi\u00adties in the stream struc\u00adture, such as slag or oxide parti\u00adcles, and in local clog\u00adging. Low flow rates do however cause less turbu\u00adlence and are favor\u00adable with respect to gas removal from the mold cavity.<\/span><\/span><\/span><\/p>\n

\"Darstellung<\/a>

Repre\u00adsen\u00adta\u00adtion of flow rate<\/p><\/div><\/div>\n

The local wear and cavi\u00adta\u00adtion asso\u00adci\u00adated with higher flow rates shorten the service life of the casting mold. These do however normally produce cast\u00adings with smooth surfaces and a fine-grained struc\u00adture.<\/p>\n

Depending on the casting mate\u00adrial and the casting concerned it is there\u00adfore impor\u00adtant to choose an appro\u00adpriate specific pres\u00adsure to obtain a casting of optimum quality. Casting simu\u00adla\u00adtion can be helpful here. This numer\u00adical simu\u00adla\u00adtion is primarily a math\u00ade\u00admat\u00adical descrip\u00adtion of the Bernoulli equa\u00adtion. It provides a graph\u00adical repre\u00adsen\u00adta\u00adtion of the rela\u00adtion\u00adships between pres\u00adsure and flow rate as a func\u00adtion of the optimum casting temper\u00ada\u00adture for the various alloys. With the results obtained, compo\u00adnents and tools can be opti\u00admally designed.<\/p>\n","protected":false},"excerpt":{"rendered":"

In die-casting, the molten metal is pressed into a mold at high velocity and under great pres\u00adsure. The velocity of the molten metal in the gate vg is usually between 30 and 60 m\/s. Casting pres\u00adsures attain values of between 400 and 800 bar. A high mold filling rate and high pres\u00adsures make it possible [\u2026]<\/p>\n","protected":false},"author":17,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"wp_typography_post_enhancements_disabled":false,"footnotes":""},"categories":[16],"tags":[],"class_list":["post-12231","post","type-post","status-publish","format-standard","hentry","category-fans"],"acf":[],"_links":{"self":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/12231","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/comments?post=12231"}],"version-history":[{"count":1,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/12231\/revisions"}],"predecessor-version":[{"id":18650,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/posts\/12231\/revisions\/18650"}],"wp:attachment":[{"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/media?parent=12231"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/categories?post=12231"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mag.ebmpapst.com\/en\/wp-json\/wp\/v2\/tags?post=12231"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}