transonic combustion seminar report

Transonic Combustion

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1. INTRODUCTION

A project “Transonic Combustion” is focusing on raising not only the fuel

mixture‟s pressure but also its temperature. In fact, is to generate a little known,

intermediate state of matter also called supercritical fluid (SC), which could markedly

increase the fuel efficiency of next generation power plants while reducing their

exhaust emissions. Advanced diesel and gasoline engines, and alternative fuels, are

really at the middle of everything. For the next 30 years, these are more „classical

powertrains‟ will dominate in industry.

The traditional four stroke Otto cycle engine piston engine only has a thermal

efficiency of 25-30 percent; there is clearly still plenty of room for improvement.

While most of the green automobile attention in recent years has been focused on

electrification, liquid fuels still have about 100 times the energy density of today‟s best

lithium-ion batteries, a difference that probably won‟t change significantly any time in

the near future. With that in mind, there is still plenty of effort being expended on

improving the humble internal combustion engine. These efforts range from

completely different structures like Eco Motors opposed piston opposed cylinder

(OPOC) to new combustion processes such as homogeneous charge compression

ignition (HCCI). One of the most interesting combustion related developments comes

from a transonic combustion. In 2007, a company was claiming it could get an ICE

vehicle to 100 mpg. The transonic system isn‟t really a radical departure from what we

have today on engines. The system has fuel injectors, a common rail, a fuel pump, and

a control system. The system could be readily integrated in to existing engines;

company anticipates production of the concept in 2015 time frame. It is a fact that

liquid fuels are going to be there for a long time more and more they‟re going to be

from alternative sources.

That‟s why we need to optimize the propulsion system for those liquid fuels.

The heart of transonic technology is a new fuel delivery system. To get the liquid fuel

into a supercritical state before injecting into the combustion chamber. Traditionally,

matter has been thought of as having three states liquid, solid, gas and any given

material can exist in one of those at any point in time depending on the temperature

and pressure. Fuels like gasoline and diesel generally only burn after they are


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vaporized. The injector may operate on a wide range of liquid fuels including gasoline,

diesel and various bio fuels. The injector fire at room pressure and up to the practical

compression limit of IC engines. Spark ignition gasoline engine efficiency is limited

by a number of factors; these include the pumping losses that result from throttling for

load control, spark ignition and the slow burn rates that result in poor combustion

phasing and a compression ratio limited by detonation of fuel. A new combustion

process has been developed based on the patented concept of injection-ignition known

as Transonic Combustion or TSCi™; this combustion process is based on the direct

injection of fuel into the cylinder as a supercritical fluid. Supercritical fuel achieves

rapid mixing with the contents of the cylinder and after a short delay period

spontaneous ignition occurs at multiple locations. Multiple ignition sites and rapid

combustion combine to result in high rates of heat release and high cycle efficiency.

The injection-ignition process is independent from the overall air/fuel ratio contained

in the cylinder and thus allows the engine to operate un-throttled. Spark ignition

gasoline engine efficiency is limited by a number of factors; these include the pumping

losses that result from throttling for load control, spark ignition and the slow burn rates

that result in poor combustion phasing and a compression ratio limited by detonation

of fuel. A new combustion process has been developed based on the patented concept

of injection-ignition known as Transonic Combustion or TSCi™; this combustion

process is based on the direct injection of fuel into the cylinder as a supercritical fluid.

Supercritical fuel achieves rapid mixing with the contents of the cylinder and after a

short delay period spontaneous ignition occurs at multiple locations. Multiple ignition

sites and rapid combustion combine to result in high rates of heat release and high

cycle efficiency.


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2. LITERATURE REVIEW OR SURVEY

2.1 Researches and Reviews:

Researches in New York demonstrated a supercritical diesel fuel injection

system that can reduce engine emission by 80 percent and increase overall by 10

percent. Diesel engines tend to be more efficient than gasoline, but the tradeoff is that

they are usually more polluting. Because diesel is heavy, viscose, and less volatile than

gasoline, not all the fuel is burned during combustion, resulting in carbon compounds

being released as harmful particulate soot. The higher combustion temperatures

required to burn diesel also lead to increased nitrogen oxides emissions. A fluid

becomes supercritical when its temperature & pressure exceed a critical boundary

point, causing it to take on novel properties between those of a liquid and a gas.

George Anitescu, a research associate at the Department of Biomedical

Chemical Engineering at Syracuse University in New York State, who developed the

new engine design, says that supercritical diesel can burned more. By raising diesel to

a supercritical state before injecting it to an engine‟s combustion chamber, viscosity

becomes less of a problem, says Anitescu. Additionally, the high molecular diffusion

of supercritical fluids means that the fuel and air mix together instantaneously. So

instead of trying to burn relatively large particles of fuel surrounded by air, the

vaporized fuel mixes more evenly with air, which makes it burn more quickly, cleanly,

and completely.

In a sense, it is like an intermediate between diesel and gasoline, but with

benefit of both, says Anitescu, who presented his review from a University of Syracuse

in New York State, in a conference held in Dearborn, MI. At the same conference,

Transonic Combustion, a company based in of Camarillo, CA, presented details of an

alternative way to use supercritical fuels that involves a novel fuel injector and is

designing the engine‟s entire valve system and combustion chamber. Another approach

is to treat conventional diesel with additives, he says. But with either approach, going

supercritical does not come without a cost; says Birgel “You still need the viscosity

because most diesel fuel systems depend upon the fuel for lubrication,”


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3. CONSTRUCTION AND WORKING

3.1 Overview of IC Engines & Thermal Losses:

3.1.1 Brief Outline about IC Engines:

An internal combustion engine (ICE) is a heat engine where the combustion of

a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an

integral part of the working fluid flow circuit.

Main drawbacks of IC engines are losses which in turn affects the efficiency.

In gasoline-powered vehicles, over 62 percent of the fuel's energy is lost in the

internal combustion engine (ICE). ICE engines are very inefficient at

converting the fuel's chemical energy to mechanical energy, losing energy to

engine friction etc.

Improper combustion leads to increase in emission of NOx, HC and CO and

there by polluting the environment

Diesel engine is quite efficient than Gasoline engine.

I.C. Engine

Reciprocating Rotary

Gas Turbine Wrankel Engine Gasoline Engine Diesel Engine

Fig 3.1: Brief Classification of I.C Engines


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3.1.2 Thermal Losses in an I.C Engine:

Engine Losses : 62.4 percent

In gasoline-powered vehicles, over 62 percent of the fuel‟s energy is lost in the

internal combustion engine (ICE). ICE engines are very inefficient at converting the

fuel‟s chemical energy to mechanical energy, losing energy to engine friction pumping

air into and out of the engine, and wasted heat. Advanced engine technologies such as

variable valve timing and lift, turbo charging, direct fuel injection, and cylinder

deactivation can be used to reduce these losses. In addition, diesels are about 30-35

percent more efficient than gasoline engines, and new advances in diesel technologies

and fuels are making these vehicles more attractive.

Idling Losses : 17.2 percent

In urban driving, significant energy is lost to idling at stop lights or in traffic.

Technologies such as Start Stop systems help reduce these losses by automatically

turning the engine off when the vehicle comes to a stop and restarting it

instantaneously when the accelerator is pressed.

Accessories : 2.2 percent

Air conditioning, power steering, windshield wipers, and other accessories use

energy generated from the engine. Fuel economy improvements of up to 1 percent may

be achievable with more efficient alternator systems and power steering pumps.

Driveline Losses : 5.6 percent

Energy is lost in the transmission and other parts of the driveline.

Technologies, such as automated manual transmission and continuously variable

transmission, are being developed to reduce these losses.


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Aerodynamic Drag : 2.6 percent

A vehicle must expend energy to move air out of the way as it goes down the

road, less energy at lower speed sand progressively more as speed increases. Drag is

directly related to the vehicle‟s shape. Smoother vehicle shapes have already reduced

drag significantly, but further reductions of 20-30 percent are possible.

Rolling Resistance : 4.2 percent

Rolling resistance is a measure of the force necessary to move the tire forward

and is directly proportional to the weight of the load supported by the tire. A variety of

new technologies can be used to reduce rolling resistance, including improved tire

tread and shoulder designs and materials used in the tire belt and traction surfaces. For

passenger cars, a 5-7 percent reduction in rolling resistance increases fuel efficiency by

1 percent. However, these improvements must be balanced against traction, durability,

and noise.

Overcoming Inertia; Braking Losses : 5.8 percent

To move forward, a vehicle‟s drivetrain must provide enough energy to

overcome the vehicle‟s inertia, which is directly related to its weight. The less a

vehicle weighs the less energy it takes to move it. Weight can be reduced by using

lightweight materials and lighter-weight technologies (e.g., automated manual

transmissions weigh less than conventional automatics).

Fig 3.1.2: Thermal Losses in I.C Engine


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3.2 Transonic Combustion

3.2.1 Transonic Combustion Principle:

Transonic engine is based on the principle of the fuel injection. In transonic

engine ignition system is removed and redesigned the fuel injection. This combustion

process is based on the direct injection of fuel into the cylinder as a supercritical fluid.

Supercritical fuel achieves rapid mixing with the contents of the cylinder and after a

short delay period spontaneous ignition occurs at multiple locations. Multiple ignition

sites and rapid combustion combine to result in high rates of heat release and high

cycle efficiency. Transonic Combustion is a venture capital and private equity funded

start-up with facilities in Los Angeles and Detroit. Founded in 2006, its focus is to

develop and commercialize fundamentally new fuel injection technologies that enable

conventional internal combustion automotive engines to run at ultra-high efficiency.

By operating high compression engines that incorporate precise ignition timing

with carefully minimized waste heat generation, Transonic Combustion may have a

“transformational” technology—one that can achieve double efficiency compared to

current gasoline powered vehicles in urban driving. In turn, the company‟s products

also may significantly reduce fossil fuel consumption and GH emissions. Supercritical

fuels have unusual physical properties that facilitate short ignition delay, fast

combustion, and low thermal energy loss. These results in highly efficient air-fuel

ratios over the full range of engine conditions from stoichiometric air-fuel ratios of

14.7:1 at full power to lean 80:1 air-fuel ratios at cruise, down to 150:1 at engine idle.

Many existing gasoline engines can only achieve around 20:1.

The implication is clear transonic proposition may facilitate a significantly

more efficient combustion process than is currently employed. The supercritical fuel is

directly injected as a "non-liquid fluid" rather than “droplets” into combustion chamber

very near the top of the piston stroke This ensures that the heat of combustion is

efficiently released only during the power stroke, thus allowing for more degrees of

freedom in engine management There is relatively little additional cost involved in

incorporating the technology into existing production lines without the need for


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Massive reconfiguration and it has lower lead times than more drastic changes in the

manufacturing process. This is reflected in the 2013 date for commercial production at

scale that Transonic believes is realistic.

Spark ignition gasoline engine efficiency is limited by a number of factors;

these include the pumping losses that result from throttling for load control, spark

ignition and the slow burn rates that result in poor combustion phasing and a

compression ratio limited by detonation of fuel. A new combustion process has been

developed based on the patented concept of injection-ignition known as Transonic

Combustion or TSCi™; this combustion process is based on the direct injection of fuel

into the cylinder as a supercritical fluid. Supercritical fuel achieves rapid mixing with

the contents of the cylinder and after a short delay period spontaneous ignition occurs

at multiple locations. Multiple ignition sites and rapid combustion combine to result in

high rates of heat release and high cycle efficiency. For a start, their density is midway

between those of a liquid and gas, about half to 60% that of the liquid. On the other

hand, they also feature the molecular diffusion rates of a gas and so can dissolve

substances that are usually tough to place in solution.

The injector may operate on a wide range of liquid fuels including gasoline,

diesel and various bio fuels. The injector fire at room pressure and up to the practical

compression limit of IC engines. If we doubled the fuel efficiency numbers in

dynamometers tests of gas engine installed with the SC fuel injection systems.

Fig 3.2.1: Four Strokes of Transonic Combustion


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3.2.2 Working of Transonic Combustion Technology (A Novel Injection-Ignition

System):

The stratified nature of the charge under part load conditions reduces heat loss

to the surrounding surfaces, resulting in further efficiency improvements. The short

combustion delay angles allow for the injection timing to be such that the ignition and

combustion events take place after TDC. This late injection timing results in a

fundamental advantage in that all work resulting from heat release produces positive

work on the piston which is called as in terms of transonic combustion. Other

advantages are the elimination of droplet burning and increased combustion stability

that results from multiple ignition sources.

Engine test results are presented over a range of speed, load and operating

conditions to show fuel consumption, emission and combustion characteristics

from initial injector and combustion system designs. The results are correlated

with thermo-dynamic modeling and comparisons are made with contemporary

engines. The Transonic Technology provides a heated catalysed fuel injector

for dispensing fuel predominately or substantially, exclusively during the

power stroke of an IC engine.

This injector lightly oxidizes the fuel in a supercritical vapour phase via

externally applied heat from an electrical heater or other means.

The injector may operate on a wide range of liquid fuels including gasoline,

diesel and various bio fuels.

The injector fire at room pressure and up to the practical compression limit of

IC engine.

Since the injector may operate independent of spark ignition or compression

ignition, its operation is referred to herein as “injection-ignition”.


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The transonic technology provides a heated catalyzed fuel injector for

dispensing fuel predominately or substantially, exclusively during the power stroke of

an IC engine. This injector lightly oxidizes the fuel in a supercritical vapour phase via

externally applied heat from an electrical heater or other means. The injector may

operate on a wide range of liquid fuels including gasoline, diesel and various bio fuels.

The injector fire at room pressure and up to the practical compression limit of IC

engines. Since the injector may operate independent of spark ignition or compression

ignition, its operation is referred to herein as “injection-ignition”.

There are two major aspects to transonic technology, the fuel preparation and

the direct injection system. The fuel delivery system is an evolution of current

direction injection systems that use a common high pressures (200-300 bars) rail to

deliver fuel directly to each combustion chamber through individually controlled

injectors. According to the transonic, the fuel is catalyzed in the gas phase or

supercritical phase only, using oxygen reduction catalysts. The injector greatly reduces

both front end and back end heat losses within the engine. Ignition occurs in a fast burn

zone at high fuel density such that a leading surface of the fuel is completely burned

within several microseconds. In operation, the fuel injector precisely meters instantly

igniting fuel at a predetermined crank angle for optimal power stroke production. More

particularly, the fuel is metered in to the fuel injector, such that the fuel injector heats,

vaporizes compresses and mildly oxidizes the fuel, and then dispenses the fuel as a

relatively low pressure gas column into a combustion chamber of the engine.

Fig 3.2.2: A Fuel Injection System in Transonic Combustion and Normal Combustion


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3.3 Supercritical Fuel:

A supercritical fluid is any substance at a temperature and pressure above its

critical point, where distinct liquid and gas phases do not exist. It can effuse through

solids like a gas, and dissolve materials like a liquid.

3.3.1 Supercritical fuel and injection system:

A comparison of standard direct injection of liquid fuel and transonic‟s novel

supercritical injection process (as viewed through an optical engine fitted with a quartz

window) shows that the new TSCi fuel delivery system does not create fuel droplets.

Throughout the history of internal combustion engine, engineers have boosted cylinder

compression to extract more mechanical energy from a given fuel-air charge. The extra

pressure enhances the mixing and vaporization of the injected droplets before burning.

Transonic combustion is focusing on raising not only the fuel mixture‟s pressure but

also its temperature. In fact, is to generate a little known, intermediate state of matter

also called supercritical fluid (SC), which could markedly increase the fuel efficiency

of next generation power plants while reducing their exhaust emissions.

Fig 3.3.1: Supercritical fuel and normal fuel injection system

Supercritical Fuel Normal Fuel


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Transonic‟s proprietary TSCi fuel-injection systems do not produce fuel

droplets as conventional fuel delivery units do. The supercritical condition of the fuel

injected into a cylinder by a TSCi system means that the fuel mixes rapidly with the

intake air which enable better control of the location and timing of the combustion

process.

The novel SC injection system, called as “almost drop in” units include “a GDI

type,” common rail system that incorporates a metal oxide catalyst that breaks fuel

molecules down into simpler hydrocarbons chains, and a precision, high speed

(piezoelectric) injector whose resistance heated pin places the fuel in a supercritical

state as it enters the cylinder If we doubled the fuel efficiency numbers in

dynamometers tests of gas engine installed with the SC fuel injection systems. A

modified gasoline engine installed in a 3200 lb. (1451 kg) test vehicle, for example, is

getting 98 mpg (41.6 km/L) when running at a steady 50 mph (80 km/h) in the lab. To

minimize friction losses, the transonic engineers have steadily reduced the

compression of their test engines to between 20:1 and 16:1, with the possibility of 13:1

for gasoline engines. Fuel conditioning is an emerging technology based on the

discovery that high powered magnets placed in a particular pattern on fuel feed lines

cause the fuel to burn at a higher temperature and more efficiently. Fuel is heated

beyond thermodynamic critical point. Heating is in the presence of a catalyst. Fuel

injection is using a specially designed fuel injector.

The new technology in addition is achieving significant reductions in engine

out emissions. Some test engines reportedly generate only 55-58 g/km of CO2, a figure

that is less than half the fleet average value established by the European Union for

2012. Two automakers are currently evaluating transonic test engines, with a third

negotiating similar trials.


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3.4: Properties and Phase Diagram:

Figure 3.4 and show projections of a phase diagram. In the pressure-

temperature phase diagram the boiling separates the gas and liquid region and ends in

the critical point, where the liquid and gas phases disappear to become a single

supercritical phase. This can be observed in the density-pressure phase diagram for

carbon dioxide, as shown in figure. At well below the critical temperature, e.g., 280K,

as the pressure increases, the gas compresses and eventually (at just over 40 bar)

condenses into a much denser liquid, resulting in the discontinuity in the line (vertical

dotted line). The system consists of 2 phases in equilibrium, a dense liquid and a low

density gas. As the critical temperature is approached (300K), the density of the gas at

equilibrium becomes higher, and that of the liquid lower.

At the critical point, (304.1 K and 7.38 MPa (73.8 bar)), there is no difference

in density, and the 2 phases become one fluid phase. Thus, above the critical

temperature a gas cannot be liquefied by pressure. At slightly above the critical

temperature (310K), in the vicinity of the critical pressure, the line is almost vertical. A

small increase in pressure causes a large increase in the density of the supercritical

phase.

Fig 3.4: Carbon-dioxide pressure-temperature phase diagram


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4. ADVANTAGES

Perfect combustion of fuel.

Pollution is reduced to a greater extent because of perfect combustion.

Knocking is eliminated.

Engine life is increased.

Improved fuel efficiency.

Lower greenhouse emission.

Multi-fuel compatible.

Economical OEM Powertrain integration.

Near term adoption.

Global automotive industrial sustainability.

Energy independence.

About 50 % increase in efficiency.


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5. DISADVANTAGES

Might be Costly.

Extraction of supercritical fluid is may be difficult.

Needs regular maintenance.

If ECU goes wrong somehow efficiency affects.


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6. APPLICATIONS

In the past, practical applications of supercritical fluids were limited to the food

processing and extraction industry. Each year tens of millions of kilograms of

the world‟s coffee and tea is decaffeinated using supercritical carbon dioxide.

In Germany for example, most decaffeinated coffee is produced using this

method.

Supercritical fluids provide an environmentally friendly alternative for solvents

used in industrial applications. For example, CO2 is currently being used to

replace harmful hazardous solvents and can be removed from the environment,

used as an environmentally friendly solvent, and returned as CO2.

Solubility of greases and oils is very high in supercritical CO2 and no residues

remain after cleaning.

Another use in industry is textile dyeing. Industry is developing CO2 soluble

dyes that will eliminate dyed wastewater as a hazardous waste.

Supercritical CO2 also acts as a solvent to leach metals from solutions, soils

and other solids. Another application of supercritical CO2 is recovery of

uranium from aqueous solutions generated in the reprocessing of nuclear fuels.

Supercritical water acts as an excellent solvent to remove and reduce wastes.

For example, water when mixed with organics and oxygen, under supercritical

conditions, will greatly reduce the production of NOx and Sox compared with

incineration practices.

This technology is also being considered for the destruction of chemical

weapons and stockpiled explosive, as well as the cleanup of industrial waste

streams, municipal waste and used water from naval vessels.


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7. CONCLUSION

If it works as promised, the transonic combustion engine technology would

improve fuel economy by far more than other options, some of which can

improve efficiency on the order of 20 percent. It is expected to cost about as

much as high end fuel injection systems currently on the market.

The system can run an engine that uses gas and diesel as well as biofuels, and it

is supposed to create an engine that is 50 percent more efficient than standard

engines. About two years ago Transonic Combustion showed off a demo

vehicle with its engine tech that got 64 miles per gallon in highway driving.

By eliminating the ignition system and introducing a completely redesigned

fuel injection system, TSCi (Injector-Ignition) realize a 50% increase in

efficiency.

With the influence of supercritical fluid enhances a complete combustion and

there by increases engine efficiency and reduces the emissions.

When tested under lab conditions the losses associated with these IC engines

were drastically reduced

The transonic combustion engine technology would improve fuel economy by

far and also reduce exhaust emission.


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8. FUTURE SCOPE

Taking Aim at Gas Guzzlers:

When people think about reducing gasoline consumption, alternative-fuel and

hybrid cars usually come to mind. A superefficient fuel injector designed to integrate

easily into conventional cars. Unlike standard fuel injectors, the TSCi injector pressurizes

and heats gasoline to 400 degrees Celsius, bringing it to a supercritical state that is partway

between liquid and gas. When the substance enters the combustion chamber, it combusts

without a spark and mixes with air quickly, allowing it to burn more efficiently than the

liquid droplets produced by standard injectors. A Transonic test car the size and weight of

a Toyota Prius achieved 64 miles per gallon at highway speeds, compared with the 48 mpg

highway rating on the Prius. Transonic is working with three major automakers and

expects the first TSCi-equipped vehicles to hit the market in 2016.

Multi Tasker:

Transonic is testing its 10.5-inch-long injector with ethanol, biodiesel, and

vegetable oil, addition to gasoline.

Fig 8.1: Gas Guzzler


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9. REFERENCES

[1] „De. Boer‟. "Transonic Combustion - A Novel Injection-Ignition System for

Improved Gasoline Engine Efficiency," SAE Technical Paper 2010-01-2110,

2010; page no.[1,7,8]

[2] „Dixon D. J.‟ and „K.P. Johnston‟ "Transonic Combustion," In Encyclopedia

of Separation Technology; 2011-2014. Page no. [9,10]

[3] „Botany Susana‟. Preface. “The Journal of Supercritical Fluids 45”.

12 June 2008133.27. May 2008. page no. [11, 12, 13]

[4] https://www.technologyreview.com/s/414683/supercritical-fuel-injection/.2014

page no. [3]

[5] injectordynamics.com/articles/fuel-pressure-explained/.May 2015 page no. [18]