Posted tagged ‘rpm’

Latest Updates in Mechanical Engineering

September 25, 2011
01-job-interview-easy selection in interview
  • 1hp=how much rpm

We need Torque to find out.

Apply this formula:

T = HP x 5252
           rpm

T = torque (in lb-ft)
HP = horsepower
5252 = constant
rpm = revolutions per minute

  • which mechanism is used in automobile gearing system

Differential mechanism

  • why different types of sound are produced in different bikes though they say run on SI engine

Engine specifications are different in different manufactures like as bore diameter(cc),ignition timing.Also the exhaust passage take more responsible for sound.

  • why entropy decreases with the increase in temperature?

ds=dQ/T

Entropy is inversely proportional to the temperature so.as temp. increases,entropy decreases

  • What type of metal is used in a propeller

Aluminium,stainless steel,magnesium bronze,NIBRAL(nickel,brass,aluminium)

  • why involute curve used in gear

1) it’s smooth to drive the gear.
2) in gears contact is only point, this type is curve take the more load than normal one

  • How Trains take turns, though there is no any differential

Purpose of the differential is to enable vehicles to take turn, by allowing both the wheel to rotate with different speed. This is required when wheels, like in car, are connected with same axle. Interestingly, wheel in trains are not connected with the axle, they are independent and hence can take turns without ant differential. This is same as how the bullock cart takes turns, without any differential.

  • Why freezer in the fridge is placed in top level?

Because density of cold air is higher than warm air,hence itis placed at top.Cold air comes downward & cool the bottom part.

  • what is more dangerous longitudinal stress or Hoop stress and why?

Hoop stress is more dangerous thanlongitudinal stress, because the dangerous area coming underthe hoop stress is circumferential,while in longitudinal,theaxial area will come under dangerous area will will be lessthan circumferential area.So the hoop stress is more dangerous than longitudinal stress

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Idling Stop Technology | i-stop

September 16, 2011

Idle stop systems save fuel by shutting down a vehicle’s engine automatically when the car is stationary and restarting it when the driver resumes driving. Especially in urban areas, drivers often let their car’s engine idle at traffic lights or when stopped in traffic jams. Switching off the engine to stop it idling in these situations enhances fuel economy by about 10% under Japan’s 10-15 mode tests.

Conventional idling stop systems restart a vehicle’s engine with an electric motor using exactly the same process as when the engine is started normally. Mazda’s ”i-stop”, on the other hand, restarts the engine through combustion. Mazda’s system initiates engine restart by injecting fuel directly into a cylinder while the engine is stopped, and igniting it to generate downward piston force. This system not only saves fuel, but also restarts the engine more quickly and quietly than a conventional idle-stop system.

01-i-stop operation-operating principle of the i-stop-idling stop technology-piston position control

  • Piston stop position control and combustion restart technology

In order to restart the engine by combustion, it’s vital for the compression-stroke pistons and expansion-stroke pistons to be stopped at exactly the correct positions to create the right balance of air volumes. Consequently, Mazda’s ”i-stop” effects precise control over the piston positions during engine shutdown. With all the pistons stopped in their optimum position, the system restarts the engine by identifying the initial cylinder to fire, injecting fuel into it, and then igniting it. Even at extremely low rpm, cylinders are continuously selected for ignition, and the engine quickly picks up to idle speed.

Thanks to these technologies, the engine will restart with exactly the same timing every time and will return to idle speed in just 0.35 seconds, roughly half the time of a conventional electric motor idling stop system. As a result, drivers will feel no delay when resuming their drive. With the ”i-stop”, Mazda can offer a comfortable and stress-free ride as well as better fuel economy.

Design of Screw Conveyor

September 8, 2011

01-screw conveyor-screw conveyor design-screw conveyor design calculations-screw conveyor housing- screw conveyor flights- screw conveyor formulae- screw conveyor flow rates

The size of screw conveyor depends on two factors

1. The capacity of the conveyor

2. The lump size of the material to be conveyed (Maximum dimensions of the particle)

Usually there are three ranges of lump sizes which are considered for selection of screw size. These are:

· A mixture of lumps and fines in which not more than 10% are lumps ranging from maximum size to one half of the maximum, and 90% are lumps smaller than one half of the maximum size.

· A mixture of lump and fines in which not more than 25% are lumps ranging from the maximum size to one half of the maximum, and 75% are lumps smaller than one half of the maximum size.

· A mixture of lump only in which 95% or more are lumps ranging from maximum size to one half of the maximum size and 5% or less are lumps less than one tenth of the maximum size.

The allowable size of a lump in a screw conveyor is a function of the radial clearance between the outside diameter of the central pipe and the radius of the inside of the screw trough, as well as the proportion of the lumps in the mixture.

The lump size of the material affects the selection of screw diameter which should be at least 12 times larger than the lump size of a sized material and four times larger than the largest lumps of an un-sized material.

Example, if screw diameter is 250mm means radial clearance is 105mm, & Maximum lump size is 60mm of 10% lumps.

Capacity of Screw Conveyor:

01-screw conveyor capacity calculation-screw conveyor manufacturers-screw conveyor shaft- screw conveyor capacity- screw conveyor components- screw conveyor bearings

 

The capacity of a screw conveyor depends on the screw diameter, screw pitch, speed of the screw and the loading efficiency of the cross sectional area of the screw. The capacity of a screw conveyor with a continuous screw:

Q = V. ρ

Q = 60. (π/4).D2.S.n.ψ.ρ.C

Where,

Q = capacity of a screw conveyor

V = Volumetric capacity in m3/Hr

ρ = Bulk density of the material, kg/m3

D = Nominal diameter of Screw in m

S = Screw pitch in m

N = RPM of screw

Ψ = Loading efficiency of the screw

C = Factor to take into account the inclination of the conveyor

 

Screw Pitch:

Commonly the screw pitch is taken equal to the diameter of the screw D. However it may range 0.75 – 1.0 times the diameter of the screw.

 

 

 

 

01-screw conveyor pitch- screw conveyor inlet- screw conveyor output- screw conveyor blade- screw conveyor motor

Screw Diameter:

 

Nominal Size D Trough height from center of screw shaft to upper edge of the trough Trough width C Thickness of Tough Tubular shaft (d1 * Thickness)

Outside diameter of solid shaft

Coupling diameter of shaft
Heavy Duty Medium Duty Light Duty
100 63 120 2 1.6 33.7*2.5 30 25
125 75 145 2 1.6 33.7*2.5 30 25
160 90 180 5 3.15 1.6 42.4*2.5 35 40
200 112 220 5 3.15 2 48.3*3.5 40 40
250 140 270 5 3.15 2 60.3*4 50 50
315 180 335 5 3.15 76.1*5 60 50
400 224 420 5 3.15 76.1*5 60 75
500 280 530 5 3.15 88.9*5 70 75

RPM of Screw:

The usual range of RPM of screw is 10 to 165. It depends on the diameter of screw and the type of material (Max RPM of screw conveyor is 165)

Loading efficiency:

The value of loading efficiency should be taken large for materials which are free flowing and non abrasive, while for materials which are not free flowing and or abrasive in nature, the value should be taken low:

Ψ = 0.12 to 0.15 for abrasive material

= 0.25 to 0.3 for mildly abrasive material

= 0.4 to 0.45 for non abrasive free flowing materials

Inclination Factor:

The inclination factor C is determined by the angle of screw conveyor with the horizontal.

 

Angle of screw with the horizontal 10° 15° 20°
Value of factor C 1 0.9 0.8 0.7 0.65

Types of screw flight:

The screw of the conveyor may be right hand or left hand, the right hand type being the usual design. The threads of the screw may be single, double or triple.

The flight of the screws may be made in either of the two ways:

1. As Helicoids

2. As Sectional flight

Helicoids Flight:

They are formed from a flat bar or strip into a continues helix. The threads are thinner at the outer edge and thicker at the inner edge.

01-screw conveyor types- screw conveyor trough- screw conveyor theory- screw conveyor thrust bearings- screw conveyor torque-helicoid flights-continues helix-flight of screws

Sectional flights:

Sectional flights are formed from a flat disc and the thickness of the thread is uniform throughout. A continuous helix is made by joining a number of sectional flights together on a piece of pipe and butt welded them. Various styles of screw flights are in use, depending on the service required.

01- screw conveyor technology- screw conveyor incline- screw conveyor introduction- screw conveyor inlet- screw conveyor information- screw conveyor output-sectional flights-continuous helix-short pitch

Some of the typical configurations are:

1. Short pitch or continuous flight:

If the conveyor is required to handle dry granular or powdered materials that do not pack, this style of flight may be selected. It is of regular construction and recommended for inclined conveyors having a slope of 20 or more, including vertical conveyors. This style is extensively used as feeder screw.

2. Ribbon flight:

If the conveyor is to handle lumpy, clinging, sticky, gummy or viscous substances, this type flight may be selected. It consists of continuous helical flight formed from steel bar and secured to the pipe by supporting lugs.

01-screw conveyor part- screw conveyor pitch- screw conveyor power- screw conveyor length- screw conveyor layout- screw conveyor lift- screw conveyor loading-ribbon flight-cut flight

3. Cut flight:

In this type of flight screws have notches cut in the periphery of the flight. These notches supplement the conveying with moderate mixing action. They are recommended for conveyors required to handle light, fine, granular or flaky materials.

01-screw conveyor length- screw conveyor layout- screw conveyor lift- screw conveyor loading-cut flight-screw flight-sectional flight

4. Cut and folded flights:

This type of flight is characterized by notches as in cut flight, together with folded segments. This type of flight creates agitation and aeration resulting in better mixing. This type of flight is used to handle light or medium weight materials having fine, granular or flaky materials.

5. Some screw conveyors have cut flight with paddles mounted at regular intervals. The paddles counteract the flow of material past the flight resulting in greater agitation and mixing.

6. Sometimes screws are made of stainless steel to suit special requirements, like the sanitation requirements for handling food, drugs and other hygienic materials.

Vertical screw conveyors

September 8, 2011


01-Vertical screw conveyors- Vertical screw pump- Vertical screw conveyor design- Vertical screw conveyor calculations

A vertical screw conveyor conveys material upward in a vertical path. It requires less space than some other types of elevating conveyors. Vertical screw conveyor can handle most of the bulk materials provided there is no large lump. The maximum height is usually limited to 30m.

A vertical screw conveyor consists of a screw rotating in a vertical casing. The top bearing for the screw shaft must be designed to stand against radial and thrust loads. A suitable inlet port at the lower end and a discharge port at the upper end of the casing are provided. Feeding a vertical screw conveyor deserves careful consideration. Most materials are fed to the vertical conveyor by a straight or offset horizontal feeder conveyor. The ideal operation of a vertical screw conveyor is to have a controlled and uniform volume of material feeding.

Uneven feeding and start stop operation may adversely affect the performance of the vertical screw conveyor in terms of speed, capacity and horse power.

Average capacities and speeds of vertical conveyor

Nominal diameter of screw in mm Capacities in m3/hr Speed of screw
150 10 Up to 400 RPM
250 35 300 RPM
300 75 250 RPM
400 170 200 RPM

Vertical screw conveyors or some special design of vertical screw conveyor finds wide application in ship unloading.

01-Vertical screw lift- Vertical screw elevator- Vertical screw feeder- vertical screw conveyor-vertical screw pump

Practical experience with these conveyors has shown that the resistance factor for vertical conveyors is higher than those of the horizontal conveyors. Resistance factor λ may be taken as 5.5 to 7.5 for grains. 6.5 to 8.3 for salt.

01-screw conveyor design calculation- screw conveyor power calculation- screw conveyor efficiency- screw conveyor theory- screw conveyor formulae- screw conveyor flow rates

The driving power of the loaded screw conveyor is given by:

P = PH + PN + Pst

Where,

PH = Power necessary for the progress of the material

PN = Driving power of the screw conveyor at no load

Pst = Power requirement for the inclination of the conveyor

Power necessary for the progress of the material PH:

For a length L of the screw conveyor (feeder), the power PH in kilo watts is the product of the mass flow rate of the material by the length L and an artificial friction coefficient λ, also called the progress resistance coefficient.

PH = Im.L. λ.g / 3600 (kilowatt)

= Im.L. λ / 367 (kilowatt)

Where,

Im = Mass flow rate in t/hr

λ = Progress resistance coefficient

Each material has its own coefficient λ. It is generally of the order of 2 to 4. For materials like rock salt etc, the mean value of λ is 2.5. For gypsum, lumpy or dry fine clay, foundry sand, cement, ash, lime, large grain ordinary sand, the mean value of λ is 4.0.

In this connection it should be noted that the sliding of the material particles against each other gives rise to internal friction. Other resistance due to grading or shape of the output discharge pattern contributes to the resistance factor. That is why the parameter λ is always higher than that due to pure friction.

Drive power of the screw conveyor at no load, PN:

This power requirement is very low and is proportional to the nominal diameter and length of the screw.

PN = D.L / 20 (Kilowatt)

Where,

D = Nominal diameter of screw in meter

L = Length of screw conveyor in meter

Power due to inclination: Pst

This power requirement will be the product of the mass flow rate by the height H and the acceleration due to gravity g.

Pst = Im.H.g / 3600

= Im.H / 367

H should be taken positive for ascending screws and will be negative for descending screws.

Total power requirement:

The total power requirement is the sum total of the above items

P = (Im (λ.L + H) / 367) + (D.L /20) (Kilowatt)

SKYACTIV TECHNOLOGY

August 23, 2011

01-2012-Mazda3-Skyactiv-Image-PETROL ENGINE-AUTOMATIC TRANSMISSION

Highlights of the SKYACTIV technologies:

  • SKYACTIV-G: a next-generation highly-efficient direct-injection gasoline engine with the world’s highest compression ratio of 14.0:1
  • SKYACTIV-D: a next-generation clean diesel engine with the world’s lowest compression ratio of 14.0:1
  • SKYACTIV-Drive: a next-generation highly-efficient automatic transmission
  • A next-generation manual transmission with a light shift feel, compact size and significantly reduced weight
  • A next-generation lightweight, highly-rigid body with outstanding crash safety performance
  • A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride


– First product to be equipped with SKYACTIV technology will be a Mazda Demio featuring an improved, fuel-efficient, next-generation direct-injection engine that achieves fuel economy of 30 km/L.

01-inline-skyactiv-technologies-chASSIS DESIGN-BODY DESIGN-DRIVE DESIGN-DIRECT INJECTION GASOLINE ENGINE


Overview of the SKYACTIV technologies

1. SKYACTIV-G
A next-generation highly-efficient direct-injection gasoline engine that achieves the world’s highest gasoline engine compression ratio of 14.0:1 with no abnormal combustion (knocking)
  • The world’s first gasoline engine for mass production vehicles to achieve a high compression ratio of 14.0:1
  • Significantly improved engine efficiency thanks to the high compression combustion, resulting in 15 percent increases in fuel efficiency and torque
  • Improved everyday driving thanks to increased torque at low- to mid-engine speeds
  • A 4-2-1 exhaust system, cavity pistons, multi hole injectors and other innovations enable the high compression ratio
2. SKYACTIV-D
A next-generation clean diesel engine that will meet global emissions regulations without expensive NOx after treatments — urea selective catalytic reduction (SCR) or a Lean NOx Trap (LNT) — thanks to the world’s lowest diesel engine compression ratio of 14.0:1
  • 20 percent better fuel efficiency thanks to the low compression ratio of 14.0:1
  • A new two-stage turbocharger realizes smooth and linear response from low to high engine speeds, and greatly increases low- and high-end torque (up to the 5,200 rpm rev limit)
  • Complies with global emissions regulations (Euro6 in Europe, Tier2Bin5 in North America, and the Post New Long-Term Regulations in Japan), without expensive NOx after treatment
3. SKYACTIV-Drive
A next-generation highly efficient automatic transmission that achieves excellent torque transfer efficiency through a wider lock-up range and features the best attributes of all transmission types
  • Combines all the advantages of conventional automatic transmissions, continuously variable transmissions, and dual clutch transmissions
  • A dramatically widened lock-up range improves torque transfer efficiency and realizes a direct driving feel that is equivalent to a manual transmission
  • A 4-to-7 percent improvement in fuel economy compared to the current transmission
4. SKYACTIV-MT
A light and compact next-generation manual transmission with crisp and light shift feel like that of a sports car, optimized for a front-engine front-wheel-drive layout
  • Short stroke and light shift feel
  • Significantly reduced size and weight due to a revised structure
  • More efficient vehicle packaging thanks to its compact size
  • Improved fuel economy due to reduced internal friction
5. SKYACTIV-Body
A next-generation lightweight, highly-rigid body with outstanding crash safety performance and high rigidity for greater driving pleasure
  • High rigidity and lightness (8 percent lighter, 30 percent more rigid)
  • Outstanding crash safety performance and lightness
  • A “straight structure” in which each part of the frame is configured to be as straight as possible. Additionally, a “continuous framework” approach was adopted in which each section functions in a coordinated manner with the other connecting sections
  • Reduced weight through optimized bonding methods and expanded use of high-tensile steel
6. SKYACTIV-Chassis
A next-generation high-performance lightweight chassis that balances precise handling with a comfortable ride feel to realize driving pleasure
  • Newly developed front strut and rear multilink suspension ensures high rigidity and lightness (The entire chassis is 14 percent lighter than the previous version.)
  • Mid-speed agility and high-speed stability — enhanced ride quality at all speeds achieved through a revision of the functional allocation of all the suspension and steering components