Unit - 6

Measurement and Testing of IC engines

Q1) How we will test the IC engine?

A1)

The performance of an engine is evaluated on the basis of the following;
(a) Specific Fuel Consumption.

(b) Brake Mean Effective Pressure.

(c) Specific Power Output.

(d) Specific Weight.

(e) Exhaust Smoke and Other Emissions.

Basic measurements The essential measurements to be undertaken to evaluate the general overall performance of an engine on almost all assessments are the following:

1. Indicated power (if possible);
2. Brake power;
3. Morse check for mechanical overall performance in case of multi-cylinder immoderate tempo engines; (
4. Rate of fuel consumption and its calorific value;
5. Rate of flow of cooling water and its rise of temperature, for calculating the j warm temperature carried away thru jacket cooling water;
6. Heat carried away thru the exhaust gases - this is expected each immediately thru } exhaust fuel line calorimeter or thru measuring air consumption and temperature of M exhaust gases, and engine room temperature.

The approach of locating indicated electricity of 1 cylinder of a multi-cylinder I.C. Engine with out using a excessive pace indicator is called the Morse test. The engine is first run beneathneath the specified circumstance of load, pace, temperature, etc., and the brake electricity is measured accurately.

Q2) How to measure the indicated power?

A2)

Measurement of indicated power:

It is extraordinarily tough to decide the ti indicated power, specifically whilst slight or excessive engine speeds are used. The ratio of most if strain with inside the engine cylinder to the suggest strain at some stage in the cycle in an I.C. Engine * is an awful lot more than that of another warmness engine. Thus, to save you vibrations being set up, the spring used need to be stiff however on the identical time it have to supply sufficient top of the indicator diagram. The manufacturing of genuine quantity scale is frequently hindered through the absence or inaccessibility of any appropriate factor of attachment for the indicator cord, in order that it could transmit the piston movement, consisting of is supplied through the cross-head of a steam engine. Any miniature crank or cam tool connected to the crank shaft need to bephased with big accuracy, even as slackness, inertia and elasticity with inside the mechanism might also additionally supply very severe results. The piston and pencil detail utilized in steam engine exercise is vain besides at very low speeds, the price of strain upward thrust inflicting violent oscillatlbns which can't be damped with out introducing errors. The substitute of the piston through a diaphragm and using excessive optical or electric magnification of its deflection, lessen the oscillation hassle however fatigue of the diaphragm metallic and alternate of its calibration through warmness are each possibly to occur.

Q3) How to measure break power and how to perform motoring test?

A3)

Measurement of brake power:

There may be very little problem in measuring this amount correctly if normal precautions are taken. This can be received via way of means of the usage of both a mechanical, electrical, hydraulic and air brake, etc. The distinction among the indicated energy and brake energy is referred to as the mechanical or friction loss, and consists of the poor loop of the indicator diagram. The following technique is followed to decide the friction energy in order that the indicated energy can be correctly determined.

Motoring test:

An approximate fee of friction energy can be located straight away following a length of strolling, via way of means of measuring the energy required to motor the engine (the engine is pushed via way of means of an electric powered motor) on the needful velocity and with the ignition switched Such a check must be performed as close to as most working temperature possible, the viscosity of the lubricant growing very significantly with a fall of temperature. Unfjprtunately the skinny movie of lubricant at the cylinder wall, the shearing of that is the motive of approximately 1/2 of the whole engine friction, suffers massive deterioration via way of means of warmness and oxidation at the same time as the engine is strolling, and on switching off the ignition, this broken oil on which the piston generally operates, is swiftly washed from the partitions and changed via way of means of oil in proper condition. The energy required to motor the engine therefore falls very swiftly inside possibly minutes, and then it starts offevolved to upward thrust slowly because of the cooling of wails. A affordable correct willpower of strolling friction is, therefore, very difficult, if now no longer not possible with ordinary check equipment.

Q4) How to perform morse test?

A4)

“Morse” test for mechanical efficiency:

For multi-cylinder excessive pace engine the Morse check is available, and is much less open to objection that the easy motoring check. The technique of locating indicated electricity of 1 cylinder of a multi-cylinder I.C. Engine with out using a excessive pace indicator is referred to as the Morse check. The engine is first run below the desired situation of load, pace, temperature, etc., and the brake electricity is measured accurately. Each cylinder is then cut-out in turn; the brake load being unexpectedly adjusted in every case to deliver the engine pace returned to the desired fee on the given attitude of enhance and throttle settling.

Q5) How to measure rate of fuel?

A5)

Measurement of rate of fuel consumption and its calorific value:

This could be very effortlessly measured for small capability engine via way of means of noting the time taken to devour a given quantity of gasoline, despite the fact that strictly speakme it's far the mass of the oil this is required. A easy device, wherein unique glass bulbs, one in every of approximately a hundred c.c. Capability and the alternative 2 hundred c.c. Capability, can be linked via way of means of three-manner cocks to the gasoline tank and the engine gasoline deliver line. Three-manner cocks assist to fill the only bulb whilst the alternative is feeding the engine. To lessen the gasoline intake to a mass basis,, the precise gravity of the gasoline oil ought to be determined, on the temperature of the oil throughout the trial. For larger length oil engine, the best and the maximum correct approach of acquiring the gasoline intake is to help the gasoline tank on a weighing system and deliver gasoline to the engine. The fee of gasoline intake is then acquired via way of means of subtracting the mass of the gasoline and tank on the give up of the trial, from that on the beginning, the time taken to discharge this mass of gasoline being noted. The maximum dependable approach of measuring the fueloline intake of a fueloline engine is to byskip the fueloline via a graduated fueloline holder from which it's far drawn via way of means of the engine. This is greater correct than using a fueloline meter. The temperature and stress of the fueloline ought to be taken, in order that the quantity used can be decreased to regular or fashionable temperature and stress.

Q6) How to measure friction power and give the limitation of willans method.

A6)

Measurement of friction power by Willans line method:

Fig. Willan’s line method

Willan’s line approach is likewise referred to as the gas price extrapolation approach. In this approach, we draw a graph in which we take brake electricity

• As proven with inside the figure, the graph is predicted again to 0 gas waft price of 0 gas in which it cuts at factor A at the terrible X-axis.

• Point A at the terrible X-axis suggests the friction electricity on the equal pace at the engine. When damage electricity will become 0, then gas intake on the equal electricity represents the gas fed on to triumph over the friction lack of the engine.

• As consistent with the graph, variant with inside the gas waft price and brake electricity is linear. It outcomes with inside the anticipation of the immediately a part of the primary curve as a terrible crossing at the X-axis at 0 gas waft price will constitute the friction electricity (F.P).

Limitations of Willans line method:

• Willan’s line approach is best used with inside the compression ignition (C.I) engine. It isn't always relevant to S.I engine.

• The friction strength given via way of means of this approach is approximate.

• Friction strength modifications even as an boom in engine velocity. That’s why the engine must run at a steady velocity at some stage in the Willan’s line test

Q7) Give the objective of testing.

A7)

Objectives of Testing

In general, the functions of trying out an inner combustion engine are:

1. To achieve statistics approximately the engine which cannot be decided with the aid of using calculations,
2. To verify facts utilized in design, the validity of that is in doubt, and
3. To fulfill the client as to the rated strength output with the assured gas consumption

The majority of checks on inner combustion engines are accomplished for business functions so as to test the following:

1. Rated strength (brake strength) with the assured gas consumption (kg/kW-hr.),
2. The amount of lubricating oil required on brake strength foundation in step with kW-hr.,
3. The amount of cooling water required on brake strength foundation in kg in step with kW-hr.
4. The stability of the engine while loaded at exclusive loads, and (v) The overload wearing ability of the engine.

Q8) How to perform thermodynamic test?

A8)

Thermodynamic Tests:

Complete thermodynamic assessments are pretty exclusive from the economic assessments. They are executed for the motive of evaluating real effects with the theoretical or best performance. For such assessments it's far essential to degree losses similarly to the beneficial a part of the energy, and additionally to attract up a warmness stability account. Such trials have been ( the direct reason of, and incentive to, the development in warmness engines all through the duration in their development.

Power Testing:

For all strength exams with consequences to be plotted as opposed to velocity, a unmarried collection of stabilized runs at ascending velocity is enough. This collection of runs must development constantly from the bottom to the maximum. If the engine calls for to be idled among run to keep away from excessively excessive temperature, enough time must be allowed for the engine once more to attain to its stabilized situation earlier than taking readings. The brake load recorded must be regular and steady at some stage in the run.

Speed Testing:

Engine speed should be held as constant as far as possible by means of applied dynamometer load at wide open throttle, or by throttle adjustment at part load.

Frictional Power:

The friction power shall follow immediately after the power test and if not possible then rest shall be conducted under conditions those for the power test.

Fuel Consumption:

Fuel intake will be measured concurrently with brake power; The gas intake dimension shall now no longer be began out till the engine is stabilized. A measuring c programming language of now no longer much less than 60 seconds will be used whilst measuring pace and gas intake. All particular gas intake figures will be primarily based totally upon found brake power.

Q9) What is break thermal efficiency?

A9)

Brake Thermal Efficiency:

1. Brake-precise gas intake (BSFC) is a degree of the gas performance of any high mover that burns gas and produces rotational, or shaft energy. It is generally used for evaluating the performance of inner combustion engines with a shaft output. It is the charge of gas intake divided via way of means of the energy produced.
2. Indicated thermal performance = B/A Brake thermal performance = C/A Energy misplaced in exhaust, coolant, and radiation Energy misplaced in friction, pumping etc.
3. Compression ratio drastically improves the brake thermal performance. Warmth similarly improves the brake thermal performance. But, growing cut-off ratio resulted with decrease brake thermal performance.
4. Diesel engines in private vehicles offer little engine braking as they're now no longer ready with a throttle frame and consequently can not draw a vacuum with inside the consumption manifold. This is called an exhaust brake and commonly determined on older trucks.

Q10) What is break power?

A10)

The brake electricity (in brief written as B.P.) of an IC Engine is the electricity to be had on the crankshaft. The brake electricity of an I.C. Engine is, usually, measured by using a brake mechanism (prony brake or rope brake).

The beneficial electricity to be had on the crankshaft with inside the engine is referred to as wreck electricity (B.P.).

In case of prony brake, brake power of the engine,

where

W = Brake load in newtons,

l = Length of arm in metres, and

N = Speed of the engine in r.p.m.

In case of rope brake, brake power of the engine,

…..[Considering diameter (d) of the rope]

Where

W = Dead load in newtons,

S = Spring balance reading in newtons,

D = Diameter of the brake drum in metres,

d = Diameter of the rope in metres, and

N = Speed of the engine in r.p.m.

Q11) Explain break specific fuel consumption of an IC engine.

A11)

Brake Specific Fuel Consumption of an IC Engine:

Specific gas intake is the quantity of gas fed on via way of means of a car for every unit of electricity output. The precise gas intake of an engine is the price of gas burnt to supply a unit of thrust.

Brake-precise gas intake (BSFC) is a degree of the gas performance of any top mover that burns gas and produces rotational, or shaft electricity. It is generally used for evaluating the performance of inner combustion engines with a shaft output.

It is the price of gas intake divided via way of means of the electricity produced. In conventional gadgets, it measures gas intake in kilos according to hour divided via way of means of the brake horsepower, lb/(hp⋅h); in SI gadgets, this corresponds to the inverse of the gadgets of precise strength, kg/J = s2/m2. It can also be notion of as electricity-precise gas intake, for this reason.

BSFC permits the gas performance of various engines to be without delay compared. To calculate the real performance of an engine calls for the strength density of the gas being used. Different fuels have unique strength densities described via way of means of the gas's heating value. The decrease heating value (LHV) is used for inner-combustion-engine-performance calculations due to the fact the warmth at temperatures underneath 150 °C (300 °F) can't be positioned to use.

Some examples of lower heating values for vehicle fuels are:

Certification gasoline = 18,640 BTU/lb (0.01204 kW⋅h/g)

Regular gasoline = 18,917 BTU/lb (0.0122222 kW⋅h/g)

Diesel fuel = 18,500 BTU/lb (0.0119531 kW⋅h/g)

Thus a diesel engine's efficiency = 1/(BSFC × 0.0119531) and a gasoline engine's efficiency = 1/(BSFC × 0.0122225)

Importance:

BSFC is a measure of the fuel efficiency of any engine that burns fuel and produces rotational power output. The BSFC value indicates how efficiently the engine converts fuel supplied into useful work. One of the main parameters used to determine the characteristics of biodiesel on BSFC is calorific value.

Q12) Give the variable compression ratio engines and heat balance sheet of IC engine.

A12)

Variable compression ratio engines, heat balance sheet of IC engines

Variable compression ratio is a era to regulate the compression ratio of an inner combustion engine at the same time as the engine is in operation. Variable compression engines permit the extent above the piston at pinnacle useless centre to be changed.

Advantage:

• Gasoline engines have a restrict at the most stress throughout the compression stroke, and then the gasoline/air combination detonates as opposed to burns.

• To acquire better electricity outputs on the equal speed, greater gasoline should be burned and consequently greater air is needed. To acquire this, turbochargers or superchargers are used to boom the inlet stress.

• This could bring about detonation of the gasoline/air combination until the compression ratio become decreased, i.e. the extent above the piston made extra. This may be completed to a extra or lesser volume with big will increase in electricity being possible.

• The down aspect of that is that beneath Neath mild loading, the engine can lack electricity and torque. The answer is which will range the inlet stress and regulate the compression ratio to suit.

• This offers the nice of each worlds, a small green engine able to extremely good electricity on demand. In addition, VCR lets in loose use of various fuels except petrol e.g. LPG or ethanol.

Compression ratios normally range among 1.05–7 in keeping with degree; however, a ratio of 3.5–4.zero in keeping with degree is taken into consideration most for maximum manner operations. Quite often, the temperature upward push of the fuelling throughout the compression dictates a restrict for the secure or affordable stress upward push.

Q13) Explain heat balance sheet of IC engines.

A13)

Heat Balance Sheet of IC engines:

Heat Balance Sheet is an account of warmth provided and warmth applied in diverse methods with inside the IC engine. Heat stability sheet is used to get essential data concerning the overall performance of IC Engine. Heat stability sheet may be accomplished on 2d foundation or minute foundation or hour foundation. Since warmness stability sheet is account of warmth provided and warmth used by engine. So we need to maintain listing of warmth provided to engine and warmth used by engine.

The heat supplied to engine is only by combustion of fuel and is equal to:

Qs = mf X CV

Where,

Mf = mass of fuel used in kg/min

CV = Calorific value of fuel in KJ/kg

List of heat which are utlized by the engines are:

1) Heat equivalent to brake power of engine.

2) Heat carried away by cooling water.

3) Heat exhausted with the exhaust gases

4) unaccounted heat loss.

1) Heat equivalent to brake power of engine.

Q B.P = B.P X 60 = _ K J/Min

2) Heat carried away by cooling water.

Qw = Mw X CPw X ( Two – Twi ) in KJ/min

Where ,

Mw =Mass of cooling water ciculated in Kg/Min

CPw = Specific heat of cooling water which is equal to 4.186 KJ/khK

Twi = Temperature of cooling water at inlet in °C .

Two= Temperature of cooling water at outlet of the engine in °C

3) Unaccounted heat losses:

A part of heat is lost by leakage of gases as well as by convection and radiation. Part of heat is also used to run other accessories like lubricating pump, cam shaft and water circulating pump. These part of heat cannot be measured accurately, so this is known as unaccounted heat. It is denoted by Qun.

Qun = Qs – (QB.P + Qw + Qg) in KJ / min

Now, we have values of heat supplied and heat utilized by the engine.From these values, we have to prepare a balance sheet.

Q14) How air pollution happens due to SI engine?

A14)

Air pollution due to SI engines

During that length the environment, with the assist of sunlight, stayed tremendously clean. As global populace grew, electricity plants, factories, and an ever-growing wide variety of vehicles started to pollute the air to the quantity that it changed into not acceptable. During the overdue 1940s, air pollutants as a hassle changed into first identified with inside the Los Angeles basin in California. Two reasons of this have been the huge populace density and the herbal climate situations of the area. Smoke and different pollution from many factories and vehicles blended with fog that changed into not unusualplace on this ocean area, and smog resulted. During the 1950s, the smog hassle elevated along side the boom in populace density and vehicle density. At this degree it changed into found out that the car changed into one of the primary participants to the hassle. By the Sixties emission requirements have been starting to be enforced in California.

Q15) Explain EURO I AND EURO II NORMS

A15)

EURO I AND EURO II NORMS

As we know, the exhaust fueloline despatched into the environment with the aid of using the engine carries hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx) which can be especially liable for air pollution. These pollution are recognized to motive extreme fitness problems. Therefore there are legal guidelines on emission requirements, which restrict the quantity of every pollutant with inside the exhaust fueloline emitted with the aid of using an vehicle engine. Emission requirements had been observed for a while with inside the evolved  countries. India is in prefer of the “European Model” evolved with the aid of using the European countries. The European emission norms are called ’Euro Norms’, In India, vehicle industries have evolved the “Euro” norms. Euro I emission norms had been enforced with inside the New Delhi Capital Region from June 1999 and Euro II norms have taken impact from April 2000 at some point of India. The info of Euro I and Euro II norms tailored to Indian situations are given in Table.

Q16) What is exhaust emission?

A16)

As already referred to essential exhaust emissions are

(i)            unburnt hydrocarbons, (HC)

(ii)            oxides of carbon, (CO and CO2),

This document was truncated here because it was created in the Evaluation Mode.