Download SNS COLLEGE OF ENGINEERING Kurumbapalayam(Po

SNS COLLEGE OF ENGINEERING
Kurumbapalayam(Po), Coimbatore – 641 107
Accredited by NAAC-UGC with ‘A’ Grade
Approved by AICTE & Affiliated to Anna University, Chennai
INTERNAL ASSESMENT EXAMINATIONS - III
COURSE: B.E –MECHANICAL
ME6016 - ADVANCED IC ENGINES
Answer Key
1.
2.
3.
4.
Explore the term trans-etherification.
In organic chemistry, transesterification is the process of exchanging the alkoxy group of an
ester compound by another alcohol. These reactions are often catalyzed by the addition of an
acid or base.
BaseTriglycerides + Free Fatty Acids (<4%) + Alcohol ——> Alkyl esters + glycerin.
Comment on the water tolerance of alcohol fuels.
The maximum permissible limit of water in the alcohol fuel is called
as water tolerance of alcohol fuels.
Unearth the sources of methanol and ethanol.
It can be produced from natural gas, coal and renewable sources such as municipal waste,
biomass and recycled carbon dioxide.
Methanol – CH3OH – is four parts hydrogen, one part oxygen and one part carbon
Can one use solid fuels for IC Engines? If so how?
Combustion of solid fuels in IC engines is not possible n practical case.
Compare and contrast the octane number and calorific value of alcohol and Petrol.
Both alcohols have a high octane rating, with ethanol at 109 RON (Research Octane
Number), 90 MON (Motor Octane Number), (which equates to 99.5 AKI) and methanol at
109 RON, 89 MON (which equates to 99 AKI).
5.
Octane rating is the measure of a fuel's ability to resist "knocking" or "pinging" during
combustion, caused by the air/fuel mixture detonating prematurely in the engine. In the U.S.,
unleaded gasoline typically has octane ratings of 87 (regular), 88–90 (midgrade), and 91–94
(premium).
The calorific value of is 45.8 MJ/kg and alcohol fuel is 36.8 MJ/kg
Mention the principle of a surface Ignition engine.
The hot-bulb engine is a type of internal combustion engine in which fuel is ignited by being
6. brought into contact with a red-hot metal surface inside a bulb, followed by the introduction
of air (oxygen) compressed into the hot-bulb chamber by the rising piston. There is some
ignition when the fuel is introduced, but it quickly uses up the available oxygen in the bulb.
Vigorous ignition takes place only when sufficient oxygen is supplied to the hot-bulb
chamber on the compression stroke of the engine.
Characterize the stratified charge engine.
A stratified charge engine is a type of internal combustion engine, used in automobiles, in
7. which the fuel is injected into the cylinder just before ignition. This allows for higher
compression ratios without "knock," and leaner air/fuel ratio than in conventional internal
combustion engines.
Outline the method to measure the in-cylinder pressure in an engine.
8.
Physical probes: in-cyl pressure, fast gas sampling valve, FID
1

Optical diagnostics:


Classical: direct photography, absorption and emission
spectroscopy, schlieren/shadowgraphy


Modern diagnostics: LDV, PIV, laser particle sizer, LIF,
Raman scattering, Rayleigh Scattering...
Interpret the function of charge amplifier.
This applies to measurements taken, for example, in the combustion chambers of
9. reciprocating engines or in gas turbines. In these cases, external charge amplifiers are
used, which convert the charge signal to a voltage signal outside the hightemperature zone.
Examine Lean Burn Engine.
10.
11 (a)
(i)
Justify alcohols as alternate fuels for IC engines and list their merits and
demerits.
The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of
interest as fuels because they can be synthesized chemically or biologically, and they
have characteristics which allow them to be used in internal combustion engines. The
general chemical formula for alcohol fuel is CnH2n+1OH.
Most methanol is produced from natural gas, although it can be produced from
biomass using very similar chemical processes. Ethanol is commonly produced from
biological material through fermentation processes. However, ethanol that is derived
from petroleum should not be considered safe for consumption as the mixture contains
about 5% methanol and may cause blindness or death. Biobutanol has the advantage in
combustion engines in that its energy density is closer to gasoline than the simpler
alcohols (while still retaining over 25% higher octane rating); however, biobutanol is
currently more difficult to produce than ethanol or methanol. When obtained from
biological materials and/or biological processes, they are known as bioalcohols (e.g.
"bioethanol"). There is no chemical difference between biologically produced and
chemically produced alcohols.
(ii)
Explain any three techniques of using alcohol in diesel engine
2
1.mixing with diesel
2.after trans estrification
3.Direct combustion.
12
(b)
(i)
Elaborate the methods to extract ethanol from grains and sugar cane.
(a)
(i)
Describe in detail about methods to extract methanol from Coal and Municipal solid
waste
3
(b)
(ii)
(a)
13
Explain the two methods by which hydrogen can be used in CI engine
1.
Direct injection into the intake manifold
2.
As an auxiliary fuel
Examine the utilization of biogas as a fuel for CI Engines.
(i)
(ii)
Persuade the necessity for gasoline injection? Explain with suitable sketch
In non-diesel internal combustion engines, gasoline direct injection (GDI), also
known as petrol direct injection, direct petrol injection, spark-ignited direct
injection (SIDI) and fuel-stratified injection (FSI), is a variant of fuel injection
employed in modern two-stroke and four-stroke gasoline engines.
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(b)
Discuss the possibility of using CNG and LNG as a fuel in SI Engines
(i)
In bi-fuel for diesel engine, natural gas as a fuel for diesel engines offers the advantage
of reduced emissions of nitrogen oxides, particulate matter, and carbon dioxide while
retaining the high efficiency of the conventional diesel engine.
Elaborate HCCI Engine
Homogeneous charge compression ignition (HCCI) is a form of internal combustion
in which well-mixed fuel and oxidizer (typically air) are compressed to the point of
auto-ignition. As in other forms of combustion, this exothermic reaction releases
energy that can be transformed in an engine into work and heat.
Automotive-HCCI-Engine-Laboratory
HCCI combines characteristics of conventional gasoline engine and diesel engines.
Gasoline engines combine homogeneous charge (HC) with spark ignition (SI),
abbreviated as HCSI. Diesel engines combine stratified charge (SC) with compression
ignition (CI), abbreviated as SCCI.
(ii)
As in HCSI, HCCI injects fuel during the intake stroke. However, rather than using an
electric discharge (spark) to ignite a portion of the mixture, HCCI raises density and
temperature by compression until the entire mixture reacts spontaneously.
Stratified charge compression ignition also relies on temperature and density increase
resulting from compression. However, it injects fuel later, during the compression
stroke. Combustion occurs at the boundary of the fuel and air, producing higher
emissions, but allowing a leaner and higher compression burn, producing greater
efficiency.
Controlling HCCI requires microprocessor control and physical understanding of the
ignition process. HCCI designs achieve gasoline engine-like emissions with diesel
engine-like efficiency.
HCCI engines achieve extremely low levels of Nitrogen oxide emissions (NO
x) without a catalytic converter. Unburned hydrocarbon and carbon monoxide
emissions still require treatment to meet automotive emission regulations.
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14 (a)
(i)
Inspect the term charge stratification. Explain the method of achieving the same with
suitable sketches. Discuss the merits and demerits of charge stratification
A stratified charge engine is a type of internal combustion engine, used in
automobiles, in which the fuel is injected into the cylinder just before ignition. This
allows for higher compression ratios without "knock," and leaner air/fuel ratio than in
conventional internal combustion engines.
Conventionally, a four-stroke (petrol or gasoline) Otto cycle engine is fueled by
drawing a mixture of air and fuel into the combustion chamber during the intake stroke.
This produces a homogeneous charge: a homogeneous mixture of air and fuel, which
is ignited by a spark plug at a predetermined moment near the top of the compression
stroke.
In a homogeneous charge system, the air/fuel ratio is kept very close to stoichiometric,
meaning it contains the exact amount of air necessary for a complete combustion of the
fuel. This gives stable combustion, but it places an upper limit on the engine's
efficiency: any attempt to improve fuel economy by running a lean mixture with a
homogeneous charge results in unstable combustion; this impacts on power and
emissions, notably of nitrogen oxides or NOx.
(b)
(i)
15 (a)
(i)
(ii)
Illustrate how a diesel engine can be controlled electronically.
Explain briefly plasma – jet ignition system.
A plasma jet ignition system for an internal combustion engine has a plasma jet spark
plug which receives ignition energy from two energy sources, one for a spark ignition
and the other for a plasma jet ignition, and performs a plasma jet ignition as well as a
spark ignition. There are further provided various control circuits to control the ignition
energy to reduce energy consumption and to promote the functions of the plasma jet
ignition. One of these circuits is arranged to stop the plasma jet ignition during a
cranking period while cranking is continued after duration of a plasma jet ignition for a
predetermined time period. Another control circuit is arranged to control the plasma jet
ignition energy corresponding to the engine temperature.
Describe the features of common rail direct injection engine with neat sketches
6
(b)
(i)
OR
Diagnosis the problems associated with using alternative fuels in IC Engine and invent
methods to solve the problems
There are numerous economic drawbacks to the use of ethanol as a substitute for
petroleum-based fuels. Ethanol is still far from being economically competitive when
compared to fuels derived from fossil fuels (Larkin, Ramage & Scurlock, 2004;
Howard & Olszack, 2004). Expensive direct costs required for the production of
ethanol can include fertilisers, pesticides, irrigation, fuels and electricity as well as
machine or equipment maintenance (Vadas, Barnett & Undersander, 2008). Fixed costs
tend to include land charges, wages for labourers, insurance and depreciation of assets
such as equipment and buildings (Vadas, Barnett & Undersander, 2008). The
economics of ethanol production are very uncertain; its viability depends on the price
of crude oil and the world prices of the raw material, for example, sugar (Larkin,
Ramage & Scurlock, 2004). The production and use of ethanol is not economically
competitive at present, suggesting that it is not a viable alternative.
There are disadvantages linked to the use of methanol and ethanol as alternative fuels.
Ethanol has a lower amount of energy generated per litre combusted than gasoline
(Baird & Cann, 2008). The use of pure ethanol and methanol is limited in colder
climates by their low vapour pressures (Baird & Cann, 2008). A disadvantage in using
methanol is that it is more toxic than gasoline (U.S. Congress, Office of Technology
Assessment, 1990). Erosion, nitrogen leaching and denitrification are also other
significant problems related to corn produced alcohols (Vadas, Barnett & Undersander,
2008). Environmental degradation is an issue related to ethanol production from crops,
which leads to the concern of whether biofuel generation is indeed sustainable for
certain crops (Vadas, Barnett & Undersander, 2008). Ethanol yield from various crops
can vary significantly, and are usually inefficient (Larkin, Ramage & Scurlock, 2004;
Ragauskas, et al., 2006). The production and use of ethanol does not always provide a
sufficient net energy gain and there are adverse environmental effects, indicating that it
is not a viable alternative.
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