Engine Friction and Lubrication

Presented By:Muhammad Umair Umar 2013-ME-306

Muhammad Shoaib Rafiq 2013-ME-307

Mubashar Manzoor 2013-ME-309

Muhammad Talha Iqbal 2013-ME-346

Muhammad Ahmed Tariq 2013-ME-347

Presented To:

Dr. Shahid Imran1

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Contents:• Friction

• Frictional work

• Terminology

• Friction components

• Measuring methods

• Rubbing friction loss

• Lubrication

• Purpose of lubrication

• Modeling of engine friction

• Problem

Friction

• Dry or Non-lubricated surface

• Lubricated Surface

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Frictional Work

• Pumping work (Wp)

• Rubbing friction work (Wrf)

• Accessory work (Wa)

• Total friction work (Wtf)

Wtf = Wp + Wrf + Wa 4

Terminologies

• Mean Effective Pressure (mep)

• Brake mean effective pressure (bmep)

• Gross indicated mean effective pressure (imepg)

• Net indicated mean effective pressure (imepn)

• Total Frictional mean effective pressure (tfmep)

• Auxiliary mean effective Pressure (amep) 5

Terminologies

• In terms of power:

fp = ip – bp

• Normalized by cylinder displacement:tfmep = pmep + rfmep + amep

• Net output of engine:imepg = imepn + pmep

• Mechanical efficiency:

ῃ = bmep / imep(g)6

Friction Components

• Crankshaft friction:Main bearings, front and rear bearing oil seals

• Reciprocating frictionConnecting rod bearings, piston assembly

• Valve trainCamshafts, cam followers, valve actuation mechanisms

• Auxiliary componentsOil, water and fuel pumps, alternator

• Pumping lossGas exchange system (air filter, intake, throttle, valves,

exhaust pipes, muffler) Engine fluid flow (coolant, oil) 7

SI Engine Friction

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Measuring Methods of friction

• Measurement of fmep from imep

• Willans Line Method

• Morse Test

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Williians line method

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Morse Test

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Comparison of Engine Friction for 4 stroke CI and SI engines

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SI Engine Losses

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Lubrication System

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Lubrication

To reduce the frictional resistance

Protect the engine against wear

Cooling of frictional parts

Remove of impurities

To hold gas and oil leakage

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Purpose of Lubrication

Lubricate:

Reduces friction

Seals:

Form a gastight seal between

piston rings and cylinder walls

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Purpose of Lubrication

Absorb shocks

Absorb Contaminants

Cleans

Cools20

Purpose of Lubrication

Viscosity: Measure of oil’s resistance to flow• A low viscosity oil is thin

• A high viscosity oil is thick

Viscosity Index:Measure of how much the

viscosity of an oil changes with

temperature.

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Low Lubrication Oil Effect

• Overheating of engine

• Failure due to lack of lubrication

• Lead to seizing of the engine or fire hazard

• Failure of bearing, cams, piston rings and engine cylinders.

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Oil Change

• Every 5000 km

• 3 months

• Ignoring regular oil change intervals will shorten engine life and performance

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Problem # 01• The inlet pressure and temperatures are 1 bar and –20oC

(253K). The cranking speed is 200 rpm. The fuel has acetane number of 45.

1. For a truck engine with a 135 mm stroke, the polytropicexponent (n) for compression is 1.2. Plot the ignitiondelay as a function of compression ratio (CR) in therange of 12 to 25. Determine the minimum CR required.

2. For a small passenger car diesel engine with a stroke of80 mm, because of the higher heat loss, n =1.12. Plotthe ignition delay on the same graph.

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Calculations

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[1]

[2]

[3]

[4]

[5]

MATLAB Program

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Results

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Results

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307.464

7.466

7.468

7.47

7.472

7.474

7.476

7.478

7.48

10 12 14 16 18 20 22 24 26

Ign

itio

n D

elay

(ms)

Compression Ratio

Ignition delay in terms of crank angle

Question # 02

The soot burn-up rate may be obtained by the Nagle and

Strickland-Constable formula. The value w in the formula is the

surface oxidation rate in g/cm2-s. Since the data for the

correlation were obtained from graphite oxidation experiments,

the rate is the value for carbon. We’ll assume that the oxidation

of soot particle is at the same rate as that of carbon. Also the

density of the soot is assumed to be 2 g/cc.

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Continue…

1. Do the calculations for the following conditions:

(a) p =100 bar and T = 2500 K

(b) p =70 bar and T = 2000 K

(c) p=30 bar and T = 1400 K

The three conditions represent roughly at the peak pressurepoint, at the end of combustion, and late in the expansionprocess.

2. To show that mass transport is not the limiting processfor oxidation of small particles, calculate the transporttime ( τ = d2/D) for particle diameter d of 10, 100 and1000 nm. The mass diffusivity D is:

D(m2 /s) = 1.8x10−5(p/p0)(T/T0 )1.81 where p0 = 1bar and T0 =300K 32

Calculation

𝐺𝑖𝑣𝑒𝑛 𝐷𝑎𝑡𝑎:𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑜𝑓 𝑠𝑜𝑜𝑡 = 2𝑔/𝑐𝑐

𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 = 300 𝐾

𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = 1 𝑏𝑎𝑟

𝐷 = 1.8𝑥10 − 5(𝑝/𝑝0)(𝑇/𝑇0 )1.81

𝑁𝑎𝑔𝑙𝑒 𝑎𝑛𝑑 𝑆𝑡𝑟𝑖𝑐𝑘𝑙𝑎𝑛𝑑 − 𝐶𝑜𝑛𝑠𝑡𝑎𝑏𝑙𝑒 𝑓𝑜𝑟𝑚𝑢𝑙𝑎𝑤/12 = [𝑘𝐴 ∗ 𝑃/(1 + 𝑘𝑍

∗𝑃)] ∗ 𝑥 + 𝐾𝐵 ∗ 𝑃(1 − 𝑥) 33

Symbols

𝑋 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒

𝑇0 = 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒

𝑃0 = 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒

𝐷 = 𝑀𝑎𝑠𝑠 𝐷𝑖𝑓𝑓𝑢𝑠𝑖𝑣𝑖𝑡𝑦

𝑑 = 𝑃𝑎𝑟𝑡𝑖𝑐𝑙𝑒 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟

Ʈ = 𝑇𝑟𝑎𝑛𝑠𝑝𝑜𝑟𝑡 𝑇𝑖𝑚𝑒

𝐾𝐴,𝐾𝐵,𝐾𝑇, 𝐾𝑍 = 𝑅𝑎𝑡𝑒 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡𝑠

𝑤 = 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑚𝑎𝑠𝑠 𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒

exp = 𝐸𝑥𝑝𝑜𝑛𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛

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Solution

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