PEMP- AME504

Alternate Fuels and Hybrid Power

Train

Session Speaker
Dr. H.K Narahari

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Day 8
• Session Topic
– Alternate Fuels
– Hybrid Power Train
• Session objectives is to learn about
– Various alternate fuels
– Configurations of hybrid power train

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Petroleum Fuels

1. Gasoline (North American Term) or Petrol

(British term
2. Diesel Fuel
3. Jet Fuel
4. Liquefied Petroleum Gas
5. Vapourised Petroleum Gas
6. Compressed Natural Gas

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Distillation of Crude oil and byproducts
C1 to C4 gasses
Fractionating LPG
column 200 C
C5 to c9 Naptha
Chemicals
700 C
Fractions decreasing
in density and boiling C5 to C10 petrol
point Petrol for vehicles
1200 C
C10 to C16 kerocene
Jet fuel, paraffin for
1700 C lighting and heating

C14 to C20 Diesel

Diesel fuels
2700 C
Crude oil
C20 to C50
lubricating oil
Lubricating oils, waxes,
polishes
C20 to C70 Fuels for
fuel oil ships,
factories and
Fractions 6000 C central
increasing in
> C70 residue Bitumen heating
density and
boiling point for roads
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Fuel Properties
Substance Density Main Boiling Ignition Latent heat of Specific Calorific
(kg/litre) constituents temperature temperature vapourisation value (MJ/kg)
0C 0C kJ/kg
SI engine fuel
Regular 0.72-0.775 86 C, 14 H 25-210 300 380-500 42.7
Premium 0.72-0.775 86 C, 14 H 25-210 400 --- 43.5
Aviation fuel 0.72 85 C, 18 H 40-180 500 --- 43.5
Kerosene 0.77-0.83 87 C, 13 H 170-260 250 --- 43
Diesel fuel 0.82-0.845 86 C, 14 H 180-360 250 250 42.5
Iso-octane 0.69 84 C, 16 H 99 410 297 44.6
Benzene 0.88 92 C, 8 H 80 550 394 40.2
Toluene 0.87 91 C, 9 H 110 530 364 40.6

Ethanol 0.79 84 C, 16H, 78 420 954 26.8

35 O
Methanol 0.79 38 C, 12H, 65 450 1110 19.7
50 O

Latent heat and Calorific values on volume basis can be obtained by multiplying per kg
value with density in kg/litre. 6
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Fuel Properties (contd)

Substance Air requirement Lower ignition limit Upper ignition
Theorotical kg/kg (% by volume of gas limit (% by
in air) volume of gas in
air)

SI engine fuel
Regular 14.8 0.6 8
Premium 14.7 -- --
Aviation fuel -- 0.7 8
Kerosene 14.5 0.6 7.5
Diesel fuel 14.5 0.6 7.5
Iso-octane 15.2 1 6
Benzene 13.3 1.2 8
Toluene 13.4 1.2 7

Ethanol 9 3.5 15
Methanol 6.4 5.5 26

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Octane Rating
Octane number: It is the percentage by Vol ume of Iso-Octane
present in a mixture of Iso-Octane and Normal heptane.
Isooctane has an octane number of 100 (minimal knock) and
heptane is 0 (bad knock).
Example: A gasoline with an octane number of 92 has the same
knock as a mixture of 92% isooctane and 8% heptane.
The most common type of octane rating worldwide is the
Research Octane Number (RON). RON is determined by
running the fuel through a specific test engine with a variable
compression ratio under controlled conditions, and comparing
these results with those for mixtures of isooctane and n-heptane.
There is another type of octane rating, called Motor Octane
Number (MON) or the aviation lean octane rating, which is a
better measure of how the fuel behaves when under load. 8
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Octane Rating
• It is possible for a fuel to have a RON greater than 100, because
isooctane is not the most knock-resistant substance available.
Racing fuels, straight ethanol, Avgas and liquified petroleum
gas (LPG) typically have octane ratings of 110 or significantly
higher - ethanol's RON is 129
• A gasoline's octane rating depends on the blend of
hydrocarbons in the fuel and other ingredients that are added to
it. Tetraethyl lead was long used as an anti-knock additive to
improve gasoline octane. In fact, it was the most effective and
least expensive octane-boosting additive that could be used for
this purpose.

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Octane Rating

• But leaded fuel cannot be used in a vehicle with a catalytic

converter because the lead fouls the catalyst. So unleaded fuel
must contain other octane-boosting additives such as MBTE
(methyl tertiary butyl ether (MTBE) or alcohol.
• Most unleaded gasoline today is rated at 87 octane, which is
sufficient for engines with compression ratios of up to about 9
to 12. Higher compression engines, engines with turbochargers
or superchargers, or ones used frequently for towing should
use a higher grade or premium gasoline.

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Cetane Rating
• The performance rating of a diesel fuel, corresponding to
the percentage of cetane in a cetane-methylnaphthalene
mixture with the same ignition performance.
• Diesel at the pump can be found in two CN ranges: 40-46
for regular diesel, and 45-50 for premium. Premium diesel
has additives to improve CN and lubricity, detergents to
clean the fuel injectors and minimize carbon deposits,
water dispersants, and other additives depending on
geographical and seasonal needs.
• Some fuel additives used to raise the cetane number are
eg. alkyl nitrates and di-tert-butyl peroxide.

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Compressed Natural Gas

• Compressed Natural Gas (CNG) is a substitute for
gasoline (petrol) or diesel fuel. It is considered to be an
environmentally "clean" alternative to those fuels. It is
made by compressing purified natural gas, and is typically
stored and distributed in hard containers.
• In response to high fuel prices and environmental concerns,
compressed natural gas is starting to be used in light-duty
passenger vehicles and pickup trucks, medium-duty
delivery trucks, and in transit and school buses.
• Compressed natural gas (CNG) is natural gas pressurized
and stored in welding bottle-like tanks at pressures up to
3,600 psig. Typically, it is same composition of the local
"pipeline" gas, with some of the water removed.
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Other Fuels for Engines

1. Hydrogen
2. Biodiesel/Biofuels
1. Biobutanol,
2. Peanut oil
3. Vegoils,
4. Bioethanol,
5. Biomethanol
6. Wood alcohol
7. Other biofuels

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Biodiesel
• Biodiesel (mono alkyl esters) is a cleaner-burning diesel fuel
made from natural, renewable sources such as vegetable oils.
• Biodiesel operates in compression ignition engines like
petroleum diesel thereby requiring no essential engine
modifications.
• Moreover it can maintain the payload capacity and range of
conventional diesel. Biodiesel fuel can be made from new or
used vegetable oils and animal fats.
Advantages of biodiesel
- The lifecycle production and use of biodiesel produces
approximately 80% less carbon dioxide emissions, and almost
100% less sulphur dioxide.

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Biodiesel

- Combustion of biodiesel alone produces over a 90% reduction

in total unburned hydrocarbons, and a 75-90% reduction in
aromatic hydrocarbons. Biodiesel further provides significant
reductions in particulates and carbon monoxide than
conventional diesel fuel.
- Biodiesel is the only alternative fuel that runs in any
conventional, unmodified diesel engine.
- Needs no change in refueling infrastructures and spare part
inventories.
- Maintains the payload capacity and range of conventional
diesel engines.

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Advantages of biodiesel
- Diesel skilled mechanics can easily attend to biodiesel
engines.
- 100% domestic fuel.
- Neat biodiesel fuel is non-toxic and biodegradable. Based on
Ames Mutagenicity tests, biodiesel provides a 90% reduction
in cancer risks.
- Cetane number is significantly higher than that of
conventional diesel fuel (CN: 55-70)
- Lubricity is improved over that of conventional diesel fuel.
- Has a high flash point of about 300 F compared to that of
conventional diesel, which has a flash point of 125 F.

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Disadvantages of biodiesel
Some of the disadvantages of biodiesel are:

-Quality of biodiesel depends on the blend thus quality can be

tampered.

-Biodiesel has excellent solvent properties. Any deposits in the filters

and in the delivery systems may be dissolved by biodiesel and result
in need for replacement of the filters.

- There may be problems of winter operatibility.

- Spills of biodiesel can decolorize any painted surface if left for long.

- Neat biodiesel demands compatible elastomers (hoses, gaskets, etc.).

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Reduction of emission from biodiesel compared to petroleum diesel
Emissions B100 B20
Regulated Emissions
Total Unburned Hydrocarbons -93% -30%
Carbon Monoxide -50% -20%
Particulate Matter -30% -22%
NOx +13% +2%
Non-Regulated Emissions
Sulphates -100% -20%*
Polyciclic Aromatic Hydrocarbons (PAH)** -80% -13%
NPAH (Nitrated PAHs)** -90% -50%***
Ozone Potential of Speciated HC -50% -10%
Life-Cycle Emissions
Carbon Dioxide (LCA) -80%
Sulphur Dioxide (LCA) -100%

*Estimated from B100 results. **Average reduction across all compounds measured.
***2-nitroflourine results were within test method variability.
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Hydrogen Vehicle
• Hydrogen Vehicles use hydrogen as primary source of power for
locomotion
•Hydrogen is used in two ways for generating power (i) by directly
combusting in the IC engine and (ii) by way of electrochemical
conversion in a fuel cell.
•In combustion method, the hydrogen is burned in engines in
fundamentally the same method as traditional gasoline cars.
•In fuel-cell conversion method, the hydrogen is reacted with
oxygen to produce water and electricity, the produced electrical
power is used to power electric motors.

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Hydrogen Vehicle

Hydrogen-Powered 1965 Cobra Replica

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Sources of Hydrogen

The required hydrogen for automotives can be obtained through

various thermochemical processes such as
•Coal gasification, as well as from natural gas,
•By thermolysis from LPG and biomass through biomass
gasification
•Through microbiological process to produce biohydrogen
•From water using electrolysis

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The hydrogen option: diverse feedstocks

Crude Oil Gasifier

Coal Gasifier
Natural Gas Reformer
Nuclear Hydrogen
Nuclear Electric Power Plant
Solar Photo-voltaic
Hydro Generator
Electrolyzer
Wind Generator
Wave Generator
Geothermal Electric Power Plant
Wood Gasifier
Organic Waste Gasifier
Biomass Gasifier

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Hydrogen Fueling Station Components

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Hydrogen-Status in India
Metal Hydride Storage
Developed by Banaras Hindu University (BHU)

Use of hydrogen in IC engines

IIT, Delhi developed hydrogen gas induction system for IC
engines - Small gensets to large capacity S. I. engines.

Development of Fuel Cells

BHEL R&D, Hyderabad,
SPIC Science Foundation-Chennai,
Glass & Ceramic Research Institute – Kolkata
IICT – Hyderabad,
DRDO – Naval Material Research Lab.,
TERI – Delhi 29
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Hydrogen for Automotives

• The advantage of hydrogen is that it can be directly produced
onboard and consumed.
• However, the car running on hydrogen produced using
hydrocarbon results in more pollution than a car running on
gasoline or diesel.
• This is because, although the hydrogen fuel cells produce less
CO2, the production of hydrogen results in higher emission.
• Hence the production of hydrogen using fossil fuels is not
advisable and other methods of production are welcome.
• At present production of hydrogen from other sources are not
economically viable.

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Hydrogen’s potential: light-vehicle CO2

emissions
From processes to produce fuel
Lb CO2 / 100 Miles From combustion of fuel
120

100 Conventional ICEs

80
Hybrid H2 FCVs

60 Hybrid ICEs
40

20

0
Gasoline Diesel CNG H2 Gasoline Diesel H2 NG Grid Renewable
reforming electrolysis electrolysis

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Hydrogen for Automotives
As a 2007 article in Technology Review argued,

In the context of the overall energy economy, a car like the BMW
Hydrogen 7 would probably produce far more carbon dioxide
emissions than gasoline-powered cars available today.

And changing this calculation would take multiple breakthroughs--

which study after study has predicted will take decades, if they
arrive at all.

In fact, the Hydrogen 7 and its hydrogen-fuel-cell cousins are, in

many ways, simply flashy distractions produced by automakers who
should be taking stronger immediate action to reduce the
greenhouse-gas emissions of their cars.
Source: wikipedia
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Limitations of Hydrogen Use in Automobiles
At present the use of hydrogen for power plant in the automobile has
following serious limitations, be it direct combustion in the engine or
through fuel cell.
• Hydrogen has the lowest volumetric energy density at ambient
conditions, one third of methane. This necessitates compression of
hydrogen to high pressure levels and/or cryogenic storage leading to
very high costs.
Even when the fuel is stored as a liquid in a cryogenic tank or in a
pressurised tank, the volumetric energy density (megajoules per m3)
is small relative to that of gasoline.
Because of the energy required to compress or liquefy the hydrogen
gas, the supply chain for hydrogen has lower well-to-tank efficiency
compared to gasoline.
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Limitations of Hydrogen Use in Automobiles

• Some research has been done into using special crystalline

materials to store hydrogen at greater densities and at lower
pressures, however with additional cost.
•Currently the use of hydrogen in fuel cells for power plant in the
automobiles is very expensive, and lead to a fragile power plant
which may not survive the bumps that an automobile experience.
•Current technologies utilize between 25 to 50 percent of the higher
heating value to produce hydrogen and deliver it to the vehicle
tank. Electrolysis, currently the most inefficient method of
producing hydrogen, uses 65 percent to 112 percent of the higher
heating value on a well-to-tank basis, owing to the comparatively
inefficient conversion of fuels to electric power

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Fuel Cost Comparison for H2 & Its Competitors

Hydrogen Production Cost for Vehicle Fueling at 5000 psi*

Hydrogen Relative Fuel Cost/Mile

12
Fossil
Nuclear (Future) Solar Photovoltaic
10 Wind Projected CA Elec. Prices
Biomass
8 H2 from electrolysis

4 H2 from natural gas

2 Gasoline

0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Key Issues:
Electricity Cost, Cents/kWh *Assumes: 1) FCV’s have 50% and H2
ICE’s 10-20% better fuel economy than
• Dispensed hydrogen more costly per mile than gasoline advanced gasoline or hybrid vehicles,
• Electrolysis more expensive than NG reforming, due and 2) all fuels (gasoline or H2) are taxed
largely to electricity costs on an equivalent BTU/mile basis.

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Limitations of Hydrogen Use in Automobiles

• As stated earlier, the use of hydrogen produced from fossil fuels in

automobile to power the vehicle would result in more pollution than
an automobile which is running on the fossil fuel itself.
This is because the production of hydrogen from fossil fuels lead to
more production of green-house effect gasses.

With all these discouraging facts on the use of hydrogen onboard an

automobile, efforts are on to invent new technologies which would
lead to the production of hydrogen at lesser cost and pollution and
ease of storing.

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Automobiles using hydrogen for power plant

• In 1807, François Isaac de Rivaz built the first hydrogen-fueled

internal combustion vehicle. However, the design was very
unsuccessful.
• A BMW hydrogen car (BMW H2R) broke the speed record for
hydrogen cars at 186 mi/h (300 km/h), and BMW has an even newer
Hydrogen 7 model.
• BMW — The BMW Hydrogen 7 is powered by a dual-fuel Internal
Combustion Engine and with an Auxiliary power based on UTC
Power fuel cell technology.
• Mazda has developed Wankel engines to burn hydrogen.
• DaimlerChrysler — F-Cell, a hydrogen fuel cell vehicle based on
the Mercedes-Benz A-Class.
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The BMW Hydrogen 7 car

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Automobiles using hydrogen for power plant

• Ford Motor – Focus FCV, a hydrogen fuel cell modification of

the Ford Focus, and E-350 buses, which began being leased in late
2006.
• General Motors — multiple models of fuel cell vehicles including
the Hy-wire and the HydroGen3
• Honda – currently experimenting with a variety of alternative
fuels and fuel cells with experimental vehicles based on the Honda
EV Plus, most notable the Honda FCX, powered by a front-
mounted 80 kW AC electric motor, with 20 kW pancake motors
• Hyundai — Tucson FCEV, based on UTC Power fuel cell
technology
• Mazda - RX-8, with a dual-fuel (hydrogen or gasoline) rotary-
engine

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Automobiles using hydrogen for power plant

• Nissan — X-TRAIL FCV, based on UTC Power fuel cell

technology

• Morgan Motor Company – LIFEcar, a performance-oriented

hydrogen fuel cell vehicle with the aid of several other British
companies

• Toyota – The Toyota Highlander FCHV and FCHV-BUS are

currently under development and in active testing.

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Hydrogen Fuelled IC engines

Combustive properties of Hydrogen:

• wide range of flammability

• low ignition energy

• small quenching distance

• high autoignition temperature

• high flame speed at stoichiometric ratios

• high diffusivity

• very low density

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Hydrogen Fuelled IC engines

• Stoichiometric ratio of A:F for hydrogen is 34:1 by mass (for

gasoline it is 14.7:1)
•This means hydrogen engine require larger amount of air for
complete combustion.

• Depending the method used to meter the hydrogen to the engine,

the power output compared to a gasoline engine can be anywhere
from 85% (intake manifold injection) to 120% (high pressure
injection).

• Because of hydrogen’s wide range of flammability, hydrogen

engines can run on A/F ratios of anywhere from
34:1 (stoichiometric) to 180:1.
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Hydrogen Fuelled IC engines

Combustion Chamber Volumetric and Energy Comparison for Gasoline and

Hydrogen Fueled Engines
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Hydrogen Fuelled IC engines

• Premature ignition is a much greater problem in hydrogen fueled

engines than in other IC engines, because of hydrogen’s lower
ignition energy, wider flammability range and shorter quenching
distance.
•Hydrogen fuel delivery system can be
(i) central injection (or “carbureted”),
(ii) port injection and
(iii) direct injection.
•The power output of a direct injected hydrogen engine is 20% more
than for a gasoline engine and 42% more than a hydrogen engine
using a carburetor.

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Hydrogen Fuelled IC engines
Engine Design:
•The most effective means of controlling pre-ignition and knock is to
re-design the engine for hydrogen use, specifically the combustion
chamber and the cooling system.
•A disk-shaped combustion chamber (with a flat piston and chamber
ceiling) can be used to reduce turbulence within the chamber. The
disk shape helps produce low radial and tangential velocity
components and does not amplify inlet swirl during compression.
•Since unburned hydrocarbons are not a concern in hydrogen
engines, a large bore-to-stroke ratio can be used with this engine.
•To accommodate the wider range of flame speeds that occur over a
greater range of equivalence ratios, two spark plugs are needed. The
cooling system must be de-signed to provide uniform flow to all
locations that need cooling. 45
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• Additional measures to decrease the probability of pre-ignition are
the use of two small exhaust valves as opposed to a single large one,
and the development of an effective scavenging system, that is, a
means of displacing exhaust gas from the combustion chamber with
fresh air.
•Due to hydrogen’s low ignition energy limit, igniting hydrogen is
easy and gasoline ignition systems can be used.
•At very lean air/fuel ratios (130:1 to 180:1) the flame velocity is
reduced considerably and the use of a dual spark plug system is
preferred.
•Spark plugs for a hydrogen engine should have a cold rating and
have non-platinum tips. A cold-rated plug is one that transfers heat
from the plug tip to the cylinder head quicker than a hot-rated spark
plug. Platinum-tip spark plugs should also be avoided since platinum
is a catalyst, causing hydrogen to oxidize with air.
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Hydrogen Fuelled IC engines

Hydrogen Internal Combustion Engine

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Hydrogen Fuelled IC engines
Crankcase Ventilation

Crankcase ventilation is even more important for hydrogen engines

than for gasoline engines.
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Hydrogen Fuelled IC engines
Crankcase Ventilation
• As with gasoline engines, unburnt fuel can seep by the piston
rings and enter the crankcase.
•Since hydrogen has a lower energy ignition limit than gasoline,
any unburnt hydrogen entering the crankcase has a greater
chance of igniting. Hydrogen should be prevented from
accumulating through ventilation.
•Ignition within the crankcase can be just a startling noise or
result in engine fire. When hydrogen ignites within the
crankcase, a sudden pressure rise occurs. To relieve this pressure,
a pressure relief valve must be installed on the valve cover.
•Since hydrogen exhaust is water vapor, water can condense in
the crankcase when proper ventilation is not provided. This may
result in poor lubrication and result in high engine wear.
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Hydrogen Fuelled IC engines

• Hydrogen engines have high thermal efficiency compared gasoline

engines due to the high ratio of specific heats of hydrogen (1.4)
when compared to that of gasoline vapour (1.1)
•Emission:
The combustion of hydrogen with oxygen produces water as its only
product: 2H2 + O2 = 2H2O

The combustion of hydrogen with air however can also pro-duce

oxides of nitrogen (NOx): H2 + O2 + N2 = H2O + N2 + NOx

The oxides of nitrogen are created due to the high temperatures

generated within the combustion chamber during combustion.

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Hydrogen Fuelled IC engines
Emission:

Emissions for a Hydrogen Engine

The emission of NOx is of the same order as that of gasoline
engine, however the absence of emission of CO and CO2 notable.
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Hydrogen Fuelled IC engines

Power

• Hydrogen burning in engine results in high gas temperatuers due

to high flame temperature resulting in high production of NOx.
•Therefore, usually hydrogen is burned with very lean mixtures
(more of air than stoichiometric ratio) to keep the temperatures at
low values. This leads to a larger volume of cylinder.
•Hence hydrogen engines invariably use superchargers and
turbochargers to keep up with the power to size ratio.

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Compressed Natural Gas (CNG) for Vehicles

COMPOSITION

• Major components of Natural gas are Methane, Ethane

and Propane.

•The proportions of these gases vary according to the

region where the gas was recovered.

•Other Components are Carbon Di Oxide, Nitrogen and

Sulphur, which may occur in Trace Amounts.

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CNG AS A FUEL
1. Natural gas is a safe Fuel.
2. It has a Vapour Density nearly three times lighter than Air,
hence it rises and dissipates quickly when released.
3. It has excellent Anti-Knock qualities which allows use of
Higher Compression Ratios for improved Power and Better fuel
Efficiency.
4. Combustion with Natural Gas is complete and homogeneous.
• This reduces the levels of unburnt Hydrocarbons, Carbon
Monoxide and Hydrocarbons.
5. It exhibits very low particulate emissions.

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CNG Composition

Methane 85-90%
Ethane 4-5%

Propane 1.7-2%
C4 & Higher 0.7-0.8%
C6 & Higher 0.2-0.3%
CO2+N2. 3-9%

Hydrocarbon 0.1-0.2%

Oxygen 0.5-0.6%
Oxygen 0.5-0.6%

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Natural Gas Composition

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Properties Gasoline CNG

Motor octane number 80–90 120
Molar mass (kg/mol) 110 16.04
Carbon weight fraction (mass%) 87 75
(A/F)s 14.6 16.79
Stoichiometric mixture density (kg/m3) 1.38 1.24
Lower heating value (MJ/kg) 43.6 47.377

Flammability limits (vol% in air) 1.3–7.1 5–15

Spontaneous ignition temperature ( C) 480–550 645
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• The ignition and burning characteristics of CNG are considerably

different from that of gasoline.
• CNG has a longer ignition delay time than most hydrocarbons, and
has higher minimum ignition energy than gasoline.
• Thus when CNG is used in a gasoline fuelled engine, the
combustion duration becomes relatively long and more advance
spark timing is required.

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Case study on CNG Engine
M.U. Aslam et al., An experimental investigation of CNG as an alternative fuel for a
retrofitted gasoline vehicle, Fuel, Volume 85, Issues 5-6, March-April 2006, Pages 717-724

• In a case study on retrofitted CNG fuelled engines showed the

potential for higher FCE (Fuel Conversion Efficiency) and
significant reduction of emissions. The following concluding
remarks were drawn from the study
• Retrofitted CNG engine produces around 16% less BMEP and
consumes 17–18% less BSFC, or consumes an average of
1.65 MJ less energy per kWh at WOT condition with CNG
compared to gasoline.
• The engine shows an average of 2.90% higher FCE nearly at
stoichiometric air–fuel ratio (λ=1) with CNG at WOT
condition and this higher value decreases with the decrease of
λ value.
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Case study on CNG Engine

• On average retrofitted engine reduced CO by around 80%,

CO2 by 20% and HC by 50% and increases NOx emissions by
around 33% with CNG compared to gasoline.
• For reducing CNG vehicles efficiency penalty due to heavier
CNG storage tank and for providing easy refueling it is
required to develop lighter CNG storage tank (400+ km) and
extensive networks of CNG supply stations at convenient
locations through out the country.
• Retrofitted CNG fuelled engines can be used for the moment
for economic, environment and energy security reasons.

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Case study on CNG Engine

NOx and HC concentration vs. engine speed at WOT.

Filled rhombus: NOx concentration with gasoline;
Open rhombus: NOx concentration with CNG;
Filled triangle: HC concentration with gasoline;
Open triangle: HC concentration with CNG.
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LPG for Automotive power
• LPG is a by-product of natural gas processing or a product that
comes from crude oil refining and is composed primarily of
propane and butane with smaller amounts of propylene and
butylenes.
• Since LPG is largely propane, the characteristics of propane
sometimes are taken as a close approximation to those of LPG.
Composition of LPG and CNG is given in the following table.

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Some of the components of LPG
Boiling Point C
Component Chemical Formula
(@ atm. pr)

Propane & derivatives C3H8 -42.1

Butane &derivatives C4H10 -0.5 to -11.7
Propylene C3H6 -47.7
Butene (s) C4H8 +3.7 to -6.47
Ethane C2H6 -88.6
Ethylene C2H4 -103.7
Pentane(s) C5H12 -27.9 to 36.1
Hexane (s) C6H14 60.2 to 69.0
Methyl Mercaptan CH3SH 5.8
Ethyl Mercaptan C2H5SH 36.7
Sulphides - -60.7 to 37.3

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Physical Properties of LPG:

• Boiling Point: The boiling point of LPG presently

marketed ranges from -42 C to -5 C.
• Density/Specific Gravity: LPG in gaseous state is nearly
twice as heavy as air. Any leakage of LPG. therefore, tends to
settle down at floor level, particularly in depressions, pits,
drains etc.
• Ground level ventilation to disperse leaking gas and prevent
accumulation is therefore most important. However, liquid
LPG is almost half as heavy as water.
• Liquid LPG expands to 246 volumes of gaseous LPG. The
leakage of liquid LPG is therefore very dangerous.
• Its flammability limits (2.1-9.5 vol.%) and auto ignition
temperature (450 degrees C) are also lower than natural gas
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Calorific value of LPG: 94 MJ/m3 or 26.1 kWh

Calorific Value of NG: 38 MJ/m3 or 10.6 kWh

• Although LPG has a relatively high energy content per unit mass,
its energy content per unit volume is low.

• Thus LPG tanks take more space and weigh more than petrol or
diesel fuel tanks.

• The range of LPG vehicles is equivalent to that of petrol or diesel

vehicles.

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• The main constituent of LPG is propane. Lower carbon-to-

hydrogen ratio, higher octane rating and its ability to form a
homogeneous mixture inside the combustion chamber enable it to
produce lesser emissions compared to conventional fuels.

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Advantages of LPG as fuel for automotive engines

• It has low cold-start emissions due to its gaseous state.

• It has lower peak pressure during combustion, which generally

reduces noise and improves durability; noise levels can be less
than 50% of equivalent diesel engines.

• LPG fuel systems are sealed and evaporative losses are

negligible.

• It is easily transportable and offers ‘stand-alone’ storage

capability with simple and selfcontained LPG dispensing
facilities, with minimum support infrastructure.

• LPG vehicles do not require special catalysts.

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Advantages of LPG as fuel for automotive engines
• It contains negligible toxic components.

• LPG has lower particle emissions and lower noise levels relative
to diesel, making it more attractive for urban areas.

• Its low emissions have low greenhouse gas effects and low NOx
precursors.

• Relative to other fuels, any increases in future demand for LPG

can be easily satisfied from both natural gas fields and oil refinery
sources.

• Emissions of PAH and aldehydes are much lower than those of

diesel-fuelled vehicles.
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Disadvantages of LPG as fuel for automotive engines

• Although LPG has a relatively high energy content per unit
mass, its energy content per unit volume is lower than diesel,
which explains why LPG tanks take more space than diesel fuel
tanks. They are pressure vessels so that they also weigh more than
diesel tanks.
• It is heavier than air, which requires appropriate handling.
• Though the lower flammability limit for LPG is actually higher
than the lower flammability limit for petrol, the vapour
flammability limits in air are wider than those of petrol, which
makes LPG ignite more easily,
• It has a high expansion coefficient so that tanks can only be
filled to 80% of capacity.
• LPG in liquid form can cause cold burns to the skin in case of
inappropriate use.
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Fuel Properties Table-1

http://eerc.ra.utk.edu/etcfc/docs/altfueltable.pdf
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Fuel Properties Table-1 (..contd)

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Fuel Properties Table-1 (..contd)

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Fuel Properties Table-1 (..contd)

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Note for table-1 Fuel Properties

Notes:
(1) Octane values are for pure components. Laboratory engine
Research and Motor octane rating procedures are not suitable
for use with neat oxygenates. Octane values
obtained by these methods are not useful in determining knock-
limited compression ratios for vehicles operating on neat
oxygenates and do not represent octane performance of
oxygenates when blended with hydrocarbons. Similar problems
exist for cetane rating procedures.
(2) The higher heating value is cited for completeness only.
Since no vehicles in use, or currently being developed for
future use, have powerplants capable of condensing the
moisture of combustion, the lower heating value should be used
for practical comparisons between fuels.
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Note for table-1 Fuel Properties

(3) Calculated.
(4) Pour Point, ASTM D 97 from Reference ( c ).
(5) Based on cetane.
(6) For compressed gas at 2,400 psi.
Sources:
(a) The basis of this table and associated references was taken from: American
Petroleum Institute (API), Alcohols and Ethers, Publication No. 4261, 2nd ed.
(Washington, DC,
July 1988), Table B-1.
(b) “Alcohols: A Technical Assessment of Their Application as Motor Fuels,” API
Publication No. 4261, July 1976.
(c) Handbook of Chemistry and Physics, 62nd Edition, 1981, The Chemical Rubber
Company Press, Inc.
(d) “Diesel Fuel Oils, 1987,” Petroleum Product Surveys, National Institute for
Petroleum and Energy Research, October 1987.
(e) ARCO Chemical Company, 1987.
(f) “MTBE, Evaluation as a High Octane Blending Component for Unleaded
Gasoline," Johnson, R.T., Taniguchi, B.Y., Symposium on Octane in the 1980’s,
American Chemical Society,
Miami Beach Meeting, September 10-15, 1979.
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FUTURE VEHICLES

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Source: Jamal N. El Hout, Vice-President, Product Planning and CV operations, GM 81

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Summary
In this session the following topics were discussed
– Alternate Fuels for automotive engines
– Hybrid power train

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