JUNE-JULY 2018 Nov-Dec 2017 - Copy - Page 94

BOOK IN SERIES The type we are now going to describe should not be mistaken with the double staggered gearpumps. We can see in Figure 4.6 (Single suction and delivery phases) that the fluid flowing out of the upper outlet cannot be delivered uniformly. As a matter of fact, the oil held in each meatus is alternately driven by the right and left teeth, thus causing a pulsating delivery along with slightly variable pressures, noise and vibrations. Luckily, the cycle is not remarkably pulsating, so it does not have the trend shown in the left part of Figure 4.15: as previously explained, the expulsion of the last drops from a specific tooth coincide with the beginning of the first phase of a tooth of the other wheel. Actually, the curve trend in standard pumps depends on the number of gear teeth: the more teeth a gear has, the less it pulsates; yet, a high number of teeth cause different types of technical problems. Pulsating flow in gear pumps Q Maximum ow variation (it does not occur in gear pumps) Q t Standard ow variation in standard gear pumps t Fig ΥΙ”€ΠΈΔΤ)Ρ‘”½Ρ‘•Θ‰δ„Ν‘••Πέ₯Ρ „±•…Ι…Ή”‘½±”Έ1•…‘₯Ήœέ‘••±Μ)…Ι”…α₯…°…ΉΝ½±₯‘±δ½ΉΉ•Ρ•ΡΌ„Ν₯Ή±”ΡΙ…ΉΝ΅₯ΝΝ₯½ΈΝ‘…™Π)…Ή½‰Ω₯½ΥΝ±δΡ‘”…Ν₯Ήœ‘…́„Ν₯Ή±”½ΥΡ±•ΠΈQ‘”‘½Υ‰±”Α…₯Θ)½˜ΝΡ…•Ι••…Ίɕ‘Ս•ΜΑΥ±Ν…Ρ₯½ΉΜ‰δ…‰½ΥΠ€άΐ€”‘ΥΙ₯Ήœ)‘•±₯Ω•ΙδΈ)%˜Ή½₯Ν”₯́ѽΌ±½Υ…Ήε•Πέ”έ…ΉΠΡΌΥΝ”Ρ‘₯ٕ́ΙδΡεΑ”½˜)ΑΥ΅ΐ°έ”…ΈΙ•Ν½ΙЁѼ•αΡ•ΙΉ…°‘•±₯…°•…ȁΑΥ΅ΑΜθΡ‘•δ…Ι”)ΕΥ₯Ρ”Ή½₯Ν•±•Ν́‰ΥЁ΅½Ι”•αΑ•ΉΝ₯Ω”…ΉΡ‘•δ…ΈΝΥΝΡ…₯Έ„)±½έ•ΘΉ½΅₯Ή…°ΑΙ•ΝΝΥΙ”Ρ‘…ΈΝΡ…Ή‘…ɐΑΥ΅Ά‰•…ΥΝ”½˜Ρ‘”)ΝΥ‰ΝΡ…ΉΡ₯…°±½…‘Ν‰•Ρέ••ΈΡ‘”‰ΥΝ‘₯ΉΜ…ΉΡ‘”Ρ••Ρ €‘₯ΥΙ”(ΠΈΔά€Έ)™…΅½Ύ₯ΉΡ•ΙΉ…Ρ₯½Ή…°½΅Α…Ήδ‘…́ɕ•ΉΡ±δ±…ΥΉ‘•„)ΝΑ•₯…°•…ȁΑΥ΅ΐΡ‘…ЁΑ…ΙΡ₯…±±δ΅••Ρ́ё”Ή••™½ΘΩ…Ι₯…‰±”)™±½άΈΝ₯Ή±”…Ν₯Ήœ‘½±‘́ΡέΌΝ•Α…Ι…Ρ••αΡ•ΙΉ…°•…Θ)ΑΥ΅Άё…Ё͑…Ι”‘•±₯Ω•Ι䁅ΉΝՍΡ₯½Έ‘½Ν•ΜμΡ‘”Α…ΙΡ́…Ι”)΅ΥΡΥ…±±δ…α₯…°…Ή½ΉΉ•Ρ•ΡΌΡ‘”Ν₯Ή±”ΡΙ…ΉΝ΅₯ΝΝ₯½Έ)Ν‘…™ΠΈ%˜Ρ‘”‘ε‘Ι…Υ±₯Œ₯ɍΥ₯ЁɕΕΥ₯ɕ́„±₯΅₯Ρ•™±½ά°Ρ‘”™±½ά)₯́•Ή•Ι…Ρ•‰δ„Ν₯Ή±”ΑΥ΅ΐ°έ‘₯±”Ρ‘”½Ρ‘•ΘΑΥ΅ΐ₯́½Έ)ΝΡ…Ή‘‰δ‘Υ”ΡΌ₯Ρ́‘•‘₯…Ρ•Ω…±Ω”Έ]‘•Έ΅½Ι”™±½ά€‘‘•Ή”)΅½Ι”Α½έ•Θ€₯́Ή••‘•°„1½…M•ΉΝ₯ΉœΝ₯Ή…°Νέ₯э‘•ΜΡ‘”)Ω…±Ω”½˜Ρ‘”Ν•½ΉΑΥ΅ΐΡ‘Ύ₯ΉΙ•…Ν₯ΉœΡ‘”™±½άΈ!½έ•Ω•Θ°)Ρ‘₯́‘•Ω₯”…ΉΉ½Π‰”±…ΝΝ₯™₯•…́„Ω…Ι₯…‰±”™±½άΑΥ΅ΐ)‰•…ΥΝ”™±½ά‘₯ΝΡΙ₯‰ΥΡ₯½Έ°…±‰•₯Ё…ΥΡ½΅…Ρ₯…±±δ°₯́…™™•Ρ•‰δ)Ρ‘”‘₯ΝΑ±…•΅•ΉΠ½˜Ρ‘”ΡέΌΑΥ΅Α₯ΉœΑ…ΙΡΜθ₯˜‰½Ρ ½˜Ρ‘•΄°)…Ё„•ΙΡ…₯ΈΙΑ΄°ΑΥ΅ΐ€Δΐ°½΅₯Έ°ΝεΝΡ•΄™±½έ́…Έ…΅½ΥΉΠΡΌ)…́±₯ΡΡ±”…Μ€Δΐ½Θ€Θΐ°½΅₯ΈΈ)₯ΥΙ”€ΠΈΔΨ(δΠ)%Έ‘½Υ‰±”ΝΡ…•Ι••…ΙΑΥ΅ΑΜ€‘₯ΥΙ”€ΠΈΔΨ€°Ρ‘”Ρ••Ρ ½˜)Ρ‘”Ν•½ΉΑ…₯ȁ½˜•…Ί…Ι”½™™Ν•Π‰δ„‘…±˜Ρ½½Ρ ΝΑ…₯Ήœ(‘„Ρ½½Ρ ½˜Ρ‘”Ν•½ΉΑ…₯ȁ₯́…ΙɅ啐₯ΈΡ‘”΅₯‘‘±”½˜Ρ‘”)ΝΑ…”‰•Ρέ••ΈΡέΌΡ••Ρ ½˜Ρ‘”™₯ΙΝЁ½Ή”€…Ή‘₯Ω₯‘•™Ι½΄)₯ΥΙ”€ΠΈΔά)έέάΉ‘΅•‘₯…‰ΥΝ₯Ή•ΝΜΉ½΄