Hydrotopics

April 17, 2009

GATE SLOTS FOR HIGH HEAD CONDUITS: PHASES OF DEVELOPMENT

Filed under: Uncategorized — Rajnikant Khatsuria @ 4:04 am

  The most practical application of slots is in high head outlet works. A slot configuration, in general, is shown in figure 1.If the downstream boundary of the slot is sharply cornered, flow separation at the corner creates a negative pressure zone. The pressures in the slot can also be negative if a clockwise vortex is caused in the slot. This is particularly so in the case with gates having skin plate and seal on the upstream side. The implications of these are quite obvious; the pressures can be as low as to cause cavitation damage to slot boundaries and negative pressure zone inside the slot can induce a downward force on the bottom of the partly open gate, viz. downpull.

  flow-around-slot8

  Improvements in slot configurations were aimed at modifying downstream corner so as to eliminate flow separation. Rounding the corners of the slot together with recessing the downstream corner and some part of the conduit wall in continuation of the slot or providing tapered transition there, was effective in reducing magnitude of negative pressures and intensity of slot vortex. Other modification consisted of providing a 5:1 quarter ellipse in continuation of the downstream corner. The improved configurations are shown in figure 2.

improvement-slot-configure4

While the above improvements were adequate for the outlets operating in relatively silt free waters, special modifications were required for the outlets handling sediment laden flows. Slot vortices can cause silt to undergo a circulatory motion in the slot area thereby inducing abrasion damage to slot boundaries. Deposition of silt into the slot can also take place and hamper smooth operation of the gate. Modifications were directed to accomplish slot configurations that would deflect sediment flow away from the slots. This indicated a need to attach some sort of a device that can deflect the flow towards centre of the outlet so that the area in the vicinity of slots remains relatively calm. Two designs were evolved; a configuration involving a slot flow deflector at the upstream corner of the slot, without projecting into the flow, and a simpler arrangement of a deflector projecting into the flow. These are shown in figures 3 and 4.

 

slot-with-deflectors3

offset-projecting-into-the-flow2

The flow conditions in the vicinity of the slots were improved to such an extent that downpull on the gates was reduced to nearly 60% of that without the modifications. However, there still remains a possibility of slight negative pressures on the slot boundaries and some abrasion damage. Therefore, such boundaries are generally provided with steel lining.

(Copyright: Neither this article nor any part may be reproduced or copied without the permission of the author in writing)

 

Advertisements

2 Comments »

  1. This article describes the development of gate slots in a coherent manner and in a nut shell. Congrtulations to the author.

    It will be highly appreciated if the design guide lines are also discussed so that a beginner can be benefitted.

    We would also welcome similar articles on pros and cons of having skin plates and seals on upstream Vs downstream side. This issue is on the debate since long but without a final say.

    Comment by K Char — May 9, 2009 @ 5:49 am | Reply

  2. SILTFREE TECHNOLOGY
    SIR,
    We are the social workers having several scientist and engineers.
    Hydro power100% GREEN ENERGY is the biggest source of energy on our planet earth which is not being harnessed except a fraction through dammed reservoirs and is being flooded in the sea as reported by several scientists including Dr. A.P.J. Abdul Kalam. And infact no mechanism to tape the concerned enormous hydro energy is searched by the scientists globally. And due to using primitive technology only 26% electric power is being generated respective to installed capacity in hydro power sector in India as per Planning Commission Report.
    After ten years research we have succeeded to develop a running model generating electricity through self developing pressure hydro turbine at India which can explain how it is working without pressure maintained by damming reservoir having following features acquiring cheapest energy with highest profitable industry on the globe, theoretically as well as practically, and are fully capable to exploit abundant hydro energy and to convert into electric energy:
    i) Highest profitable industry,
    ii) Cheapest renewable non-conventional energy,
    iii) 100% pollution free power,
    iv) Self pressure developing turbine,
    v) Silt free technology (as silt is greatest obstacle in conventional
    hydro turbine for energy harnessing),
    vi) 100% safe passage to aqueous animals,
    vii) 90%efficiency in conversion of potential energy into mechanical energy,
    viii) Immense amount energy generation capacity 0.5 to 500 megawatts,
    ix) Project completion period is six months to one year only.
    Due to silt free technology we are able to allow water flow along with sand, pebbles, cobbles etc. through present hydro turbine causing no damage to it at all and resulting extra-ordinary features:
    a) No civil construction on feeding canal is required but natural flow is permitted.
    b) No construction of weirs on feeding canal is required.
    c) Due to exclusion of such civil works, costing of project substantially reduced as well as time saving minimized.
    d) No penstock is required.
    e) Heavy amount of canal live fishes is collected lead to a extra benefit.
    Where present invented HYDRO ENERGY TAPING DESVICE can be operated:
    At any water flow point with minimum two meters altitude for device installation such as:
    i) All type of barrages.(which are more or less 4 thousand in India)
    ii) Dammed reservoirs managing for irrigation, industrial and domestic supply.
    iii) Weirs at feeding canal lead to fill dammed reservoirs.
    iv) Between upstream dam and down stream dam.
    v) High steep slope water flow.
    vi) Lakes out flow.
    vii) All types of water falls (which are about 300 in India) (without disturbing tourism as four hours for public viewing and 20 hours for power generation per day).
    viii) Directly on any river, canal by erecting two meters high retaining wall for installation of present hydro device carrying inflow and out flow.
    Due to heavy silt, several hydro-units in India have been damaged completely and are lying closed for several decades such as on MADHYA GANGA CANAL Water flow to the turbine is also completely choked by deposition of heavy silt, their hydro turbine also embedded under the silt.
    Several hydro units which are constructed in the British period such as SUMERA AT Jawaan Aligarh, PALRA at Khurja and BHOLA at Meerut etc.,etc. have become waste material. And the operation and working of the conventional hydro turbine is failed completely and are not viable thereto.
    The present mechanism is also appreciated and certified by several highly qualified Engineers and Professors after inspection of present device.
    But, if we are given opportunity, to provide some hydro sites more preferably dead/sick unit, we may be able to prove to generate more electric power beyond imagination, e.g. as a trial project, to the tune of 0.5 Mega Watt from Sumera, one mega Watt from Palra and three Mega watts from Bhola according to their quantum of water flow by installing the present innovative device within the period of six months to one year after completing legal formality and getting no objection certificates from concerned departments/bodies, for best satisfaction and for making evidence of highest electric generation through our ultra advanced technology in comparison to all other technology prevailed worldwide.
    Your kind consideration is desired to cooperate for implementation of present mechanism in boosting renewable energy and to curb the power crisis, also for saving fossils fuel and for the development of the nation in multiple ways.
    We co-cordially invite you along with expert team to visit for inspection the present running hydro turbine model installed at Civil Lines, Aligarh for technical explanation and satisfaction beyond doubt.
    Thanks
    Shaheen Ahmad & Associates
    Contact: +91-9045642678

    Comment by shaheen ahmad — August 22, 2012 @ 9:58 pm | Reply


RSS feed for comments on this post. TrackBack URI

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Blog at WordPress.com.

%d bloggers like this: