Radiation Heat Transfer

-
Image
View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge.  Photoshoped pics  are developed.  Some pics and GIF from Google.   Videos from YouTube ( Engineering Sights ).
Post a Comment

Gear Generation by Machining

-

Gear Generation by Machining 

Tooth profile is provided by much simpler form cutting tool through hobbing, gear shaping. It involves the following methods:
    1. Gear Hobbing
    2. Gear Shaping

1. Gear Hobbing 

It is defined as, "a machining process in which gear teeth are progressively generated by a series of cuts with a helical cutting tool".
    • Most accurate machining process.
    • Used for gears production because it has excellent surface finish.
    • Continuous Indexing Process  ↠  in which both cutting tool and workpiece rotate in constant relationship while hob is being fed into work.
Feed Directions 
The direction of feed during hobbing operation depends upon the type of gear to be cut. Following are the types of feed directions:
    1. Axial Feeding  ↠  cutting spur and helical gears (Hob axis is parallel to Blank axis).
    2. Radial Feeding  ↠  for bevel gears (Hob axis is perpendicular to Blank axis).
    3. Tangential Feeding  ↠  for worm, straight, spiral gears (Hob and Blank axes are tangential).
    4. Combined Radial and Axial Feeding
    5. Diagonal Feeding

2. Gear Shaping

It involves the cutting of gear teeth with a gear shaped cutter mounted on a spindle which is in reciprocatory motion.
    • Main axis is parallel to gear blank axis.
    • Fixed relative rpm of both cutter and blank using Gear Train formula.
Advantages
    • Automatic Indexing
    • HSS gear type with proper rake and clearance angles.
    • Accuracy and repeatability of gear tooth profile can be maintained.
    • Close tolerance maintained.
    • Except worm and worm wheels, all gears are made.
Limitations 
    • Error in one teeth  ↠  transfer to gear.
    • No cutting in return stroke.
Return Stroke Speed > Cutting Stroke Speed

Gear Shaping by Rack Type Cutters

It is defined as, "generation of teeth by reciprocating planning action of the cutter against rotating gear blank". There are two methods for the the gear shaping using rack type cutter.
    1. Magg Method
    2. Sunderland Method

1. Magg Method

    • Blank axis is vertical whereas rack cutter reciprocates vertically.
    • Less accurate because of errors in tooth geometry by provided repositioning of rack and blank for completion of entire circumference,

2. Sunderland Method (more accurate)

    • Gear Blank is mounted in horizontal plane axis.
    • Cutter reciprocates parallel to the axis of gear blank.
    • Cutter rack is disengaged from blank after the blank has rotated one or two pitch distances.
Note:

References:

  • Material from Class Lectures + Book named Fundamentals of Modern Manufacturing Materials, Processes and Systems by Groover + My knowledge. 
  • Photoshoped pics are developed. 
  • Some pics and GIF from Google.  
  • Videos from YouTube (Engineering Sights).

Comments

Post a Comment

HI, we wI'll contact you later

Popular posts from this blog

Techniques and instruments used in Hydrographic Survey

-
Image
Hydrographic Survey Hydrography is the science which determines the physical features and the navigable portions of the Earth's surface adjoining coastal areas. Surveyors study bodies of water to see what the floor looks like. Techniques and Instruments used in Hydrographic Survey : Many instruments are used in hydrographic survey like multibeam sonars, LIDAR, multibeam echo sounders(MBES), global positioning system (GPS), laser scanners etc. Among these instruments some are discussed ahead which are mostly used. 1. Light Detection and Ranging: LIDAR is used to measure the elevation or the depths of water bodies by analyzing the reflection of laser light off an object or seafloor.  Bathymetric LIDAR is used to determine is used to determine the depths of water bodies by measuring the time delay between the pulse of transmission and its return signals. 2.Multibeam Sonars: Multibeam echo sounders(MBES) or sonar systems transmit sound energy which strike seafloor a
Read more

Corrections Of Tape

-
Image
TAPING CORRECTIONS There are two types of corrections depending upon the type of errors in tape due to the different conditions.  1. Systematic Errors : Slope Erroneous tape length Temperature Tension Sag 2. Random Errors : Slope  Alignment Marking & Plumbing Temperature Tension & Sag 1. Temperature Correction  It is necessary to apply this correction, since the length of a tape is increased as its temperature is raised, and consequently, the measured distance is too small.  It is given by the formula,                         C t  = 𝛼 (T m  – T o )L Where,   C t  = the correction for temperature, in m.      𝛼 = the coefficient of thermal expansion.    T m  = the mean temperature during measurement.          T o  = the temperature at which the tape is standardized.       L = the measure length in m. For Foot Unit :                          C t  = 6.45×10^-6  (T m  – 68 )L For Metric Unit :                          C t  = 1.16
Read more

Vapour and Combined Power Cycle

-
Image
Rankine Cycle  Rankine cycle is an ideal cycle for Vapour Power Cycles and is normally used for Electricity Generation. The Rankine cycle consist of following steps: 1 ↝ 2 : Isentropic Compression in Pump. 2 ↝ 3 : Constant Pressure Heat Addition in Boiler. 3 ↝ 4 : IsentropicExpansion in Turbine. 4 ↝ 1 : Constant Pressure Heat Rejection in Condenser. Energy Balance: Since, all the devices which Rankine Cycle posses are steady flow devices, so the energy balance for Rankine cycle is: 》For Pump ( q = 0 ): 》For Boiler ( w = 0 ): 》For Turbine ( q = 0 ): 》For condenser ( w = 0 ): The thermal efficiency of Rankine Cycle is: How can we Increase the Efficiency of A Rankine Cycle: The efficiency of a Rankine cycle can be increased: Increasing the avg. temperate at which heat is added  Decreasing the avg. Temperature  at which heat is rejected. The above two objectives can be achieved by following three methods: 1. By
Read more