transonic novel fuel injection system engine.pdf

A Seminar Report On Transonic Engine

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Department of Mechanical Engineering, VIT (EAST), JAIPUR

CHAPTER 1

1. INTRODUCTION

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 optimise 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 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.


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1.1 Transonic Engine Principle:

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

is removed and redesigned the fuel injection.

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 GHG emissions.

Transonic’s patented product is its TSCi™ fuel injection system that utilizes supercritical fuel,

enabling significant improvements in fuel consumption Employing supercritical fuel in automotive

powertrains is being pioneered independently by Transonic according to Brian Ahlborn, the

company’s CEO. Supercritical fuels have unusual physical properties that facilitate short ignition

delay, fast combustion, and low thermal energy loss. This 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’s proposition may facilitate a

significantly more efficient combustion process than is currently employed.

While the intellectual property is understandably proprietary, Transonic Combustion’s unique

feature is that it injects fuel in a different manner. Fuel is raised to a supercritical state and injected

during the combustion process with more precise timing, meaning Transonic’s process uses

substantially less fuel than conventional systems. The supercritical fuel is directly injected as a

"non-liquid fluid" rather than “droplets” into the 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. A wide variety of fuels

can be accommodated by Transonic’s systems, with internal testing having been successful with

gasoline, biodiesel and advanced biofuels.

Transonic foresees a bright future for its factory TSCi™ technology. With the intention of acting

as a supplier to global OEMs (and already working directly with five), the scale at which this


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technology could be adopted is large. There is relatively little additional cost involved in

incorporating the technology into existing production lines without the need for 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. 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.

Additionally, 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. 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. SC fluids have unique properties. 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.


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FIG: 1.1 TSCi FUEL INJECTION SYSTEM


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CHAPTER 2

2. 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. 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 enables 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.


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FIG 1.2: SUPERCRITICAL FUEL INJECTION

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.

2.1 Ignition Timing The Key

SC fluids have unique properties. 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.


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Additionally, a SC fluid has a very low surface tension. This enables quicker mixing, and it exhibits

catalytic activity that is two to three orders of magnitude faster than the purely liquid form of the

substance.

If you eliminates the time it takes to vaporize fuel and the heat lost with contact with the cylinder

walls, we could improve the base efficiency of an engine far beyond what would normally be

possible to achieve with.

The TSCi system uses supercritical fuel to place most of the combustion in the hot eddy of gas that

forms at the centre of a standard diesel cylinder chamber. It is been figured that by changing the

ignition delay so that that fuel ignited in that area, the flame can be kept away from contact with

the walls, which take heat out the engine.

It was designed to limit combustion to with in the first 20 to 30 degrees past top dead center, to

make full use of mechanical energy created by burning while reducing the heat lost to the exhaust.

FIG: 1.3 SUPERCRITICAL FUEL INJECTION IN OPTICAL SPRAY VESSEL


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2.2 Sweet Spot

To minimise 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. There may

be some advantage to going a little higher, but the developers had tried to keep the fuel system

within the range that OEMs understand.

The fundamental problem is that on average about 15% of the energy from the gasoline you put

into your tank gets used to move your car down the road (U.S. Department of Transportation:

Transportation Research Board). The rest of the energy is lost to engine and driveline inefficiencies

and idling.

The engine is where most thermal efficiency loss takes place. Combustion irreversibly results in

large amount of waste heat escaping through the cylinder walls and unrecoverable exhaust energy.

Normal engines runs with rich air to fuel ratios, which also results in fuel being trapped in the

crevice as well as partially combusting near the cylinder walls, this energy loss is the core of

automotive inefficiency.

While we explore solutions for a car industry that accounts for half of the transportation sector’s

fuel consumption and greenhouse gas emissions, many short-term and long term alternatives are

being considered, each option has deep implications in terms of sourcing raw materials, changing

automotive powertrain architectures, revamping energy infrastructures, and many unknown

technological and environmental consequences. The considerable economic costs to consumers

and society must be carefully considered to pursue the most viable, sustainable solutions.

Experts from academia and industry agree that the technologies required to improve the efficiency

of new cars and trucks mainly involve incremental change to conventional internal combustion

engines. According to a recent study, efficiency improvements of internal combustion engines can

reach 30% by 2020 and up to 50% by 2030.

The potential benefits are large and greatly exceed the expected costs of improved fuel economy.

Cutting global average automotive fuel consumption by 50% would reduce emissions of CO2 by

over 1 gig ton a year by 2025 and over 2 gig tons by 2050, resulting in annual savings of imported

oil worth over $300 billion in 2025 and $600 billion in 2050 (oil = $100/barrel).

For consumers, the cost of improved technology for more fuel efficient cars could be recovered by

fuel savings in the first few years of use of a new car. But volatile oil prices create conditions that


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influence new car buyers purchase consideration of higher efficiency, higher priced vehicles that

in turn influence product offerings from global car manufacturers.

Another study found that fuel efficiency improvements enabled by advanced combustion

technologies of 50% or more for automotive engines and 25% or more for heavy duty truck engines

relative to today’s diesel truck engines) are possible in the next 10 to 15 years .

The most promising directions for novel combustion strategies for high efficiency, clean internal

combustion engine technology involve combustion of lean or dilute fuel air mixtures beyond limits

that have been reached to date. Local mixture composition is the driving parameter for ignition,

combustion rate and pollutant formation. Therefore it is crucial to understand and control how fuel,

air, and potentially recirculated exhaust gas are mixed.

The potential to improve fuel efficiency with advanced internal combustion engine technologies

is enormous. Transonic’s breakthrough high energy efficiency, low carbon footprint solution

disrupts the stagnant efficiency trajectory of the internal combustion engine over the past 100

years.

Transonic’s lean combustion process utilizes lean air to fuel ratios that minimize many of thermal

efficiency losses from today’s engine technology. Transonic’s precision controlled fuel injection

systems address these issues to dramatically improve the efficiency and halve the emissions of

modern internal combustion engines.

2.3 The Transonic Combustion Technology

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 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 bar) rail to deliver fuel directly to each combustion chamber

through individually controlled injectors.


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According to the transonic, the fuel is catalysed 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: 2.3.1 THE COMBUSTION TECHNOLOGY BY COMMON RAIL SYSTEM

The transonic combustion, engine include a combustion chamber, wherein the fuel injector is

mounted substantially in the center of the cylinder head of the combustion chamber. During

operation, a fuel column of hot gas is injected into the combustion chamber, such that a leading


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surface of the fuel column auto detonates and the fuel column is radially dispensed into a swirl

pattern mixing with the intake air charge. The combustion chamber provides a lean burn

environment, wherein 0.15 to 5% of the fuel is pre oxidised in the fuel injector by employing high

temperature and pressure. Pre oxidation within the fuel injector may include the use of surface

catalysts disposed on injector chamber walls and oxygen sources including standard oxygenating

agents such as methyl tetra butyl ether (MTBE), ethanol, other octane and cetane boosters, and

other fuel oxygenator agents, pre oxidation may further comprise a small amount of additional

oxygen taken from air or from recirculated exhaust gas. Cheiky's aim, in fact, is to generate a little-

known, intermediate state of matter—a so-called supercritical (SC) fluid—which he and his co-

workers at Camarillo, CA-based Transonic Combustion believe could markedly increase the fuel

efficiency of next-generation power plants while reducing their exhaust emissions. Transonic’s

proprietary TSCi fuel-injection systems do not produce fuel droplets as conventional fuel delivery

units do, according to Mike Rocke, Vice President of Marketing and Business Development. 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 enables better control of the location and timing of the

combustion process. The novel SC injection systems, which “almost drop-in” units, include “a

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

down into simpler hydrocarbon chains, and a precision, high-speed (piezoelectric) injector whose

resistance-heated pin places the fuel in a supercritical state as it enters the cylinder. Company

engineers have doubled the fuel efficiency numbers in dynamometer tests of gas engines fitted

with the company’s prototype 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. The 48-employee firm is finalizing a development engine for

a test fleet of from 10 to 100 vehicles, while trying to find a partner with whom to manufacture

and market TSCi systems by 2014. “A supercritical fluid is basically a fourth state of matter that’s

part way between a gas and liquid,” said Michael Frick, Vice President for Engineering. A

substance goes supercritical when it is heated beyond a certain thermodynamic critical point so

that it refuses to liquefy no matter how much pressure is applied. SC fluids have unique properties.

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.


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CHAPTER 3

3. FUEL INJECTION IN DIESEL ENGINES

3.1 Mechanical and Electronic Injection

Older engines make use of a mechanical fuel pump and valve assembly which is driven by the

engine crankshaft, usually via the timing belt or chain. These engines use simple injectors which

are basically very precise spring-loaded valves which will open and close at a specific fuel

pressure. The pump assembly consists of a pump which pressurizes the fuel, and a disc-shaped

valve which rotates at half crankshaft speed. The valve has a single aperture to the pressurized fuel

on one side, and one aperture for each injector on the other. As the engine turns the valve discs

will line up and deliver a burst of pressurized fuel to the injector at the cylinder about to enter its

power stroke. The injector valve is forced open by the fuel pressure and the diesel is injected until

the valve rotates out of alignment and the fuel pressure to that injector is cut off. Engine speed is

controlled by a third disc, which rotates only a few degrees and is controlled by the throttle lever.

This disc alters the width of the aperture through which the fuel passes, and therefore how long

the injectors are held open before the fuel supply is cut, controlling the amount of fuel injected.

This contrasts with the more modern method of having a separate fuel pump (or set of pumps)

which supplies fuel constantly at high pressure to each injector. Each injector then has a solenoid

which is operated by an electronic control unit, which enables more accurate control of injector

opening times depending on other control conditions such as engine speed and loading, resulting

in better engine performance and fuel economy. This design is also mechanically simpler than the

combined pump and valve design, making it generally more reliable, and less noisy, than its

mechanical counterpart.

Both mechanical and electronic injection systems can be used in either direct or indirect injection

configurations.

3.2 Indirect Injection

An indirect injection diesel engine delivers fuel into a chamber off the combustion chamber, called

a pre chamber, where combustion begins and then spreads into the main combustion chamber.


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3.3 Direct Injection

Modern diesel engines make use of one of the following direct injection methods:

3.3.1 Distributor pump direct injection

The first incarnations of direct injection diesels used a rotary pump much like indirect injection

diesels, however the injectors were mounted directly in the top of the combustion chamber rather

than in a separate pre-combustion chamber. Examples are vehicles such as the Ford Transit and

the Austin Rover Maestro and Montego with their Perkins Prima engine. The problem with these

vehicles was the harsh noise that they made and particulate (smoke) emissions. This is the reason

that in the main this type of engine was limited to commercial vehicles (the notable exceptions

being the Maestro, Montego and Fiat Croma passenger cars). Fuel consumption was about 15% to

20% lower than indirect injection diesels which for some buyers was enough to compensate for

the extra noise.

This type of engine was transformed by electronic control of the injection pump, pioneered by

Volkswagen Audi group with the Audi 100 TDI introduced in 1989. The injection pressure was

still only around 300 bar, but the injection timing, fuel quantity, exhaust gas recirculation and turbo

boost were all electronically controlled. This gave much more precise control of these parameters

which made refinement much more acceptable and emissions acceptably low. Fairly quickly the

technology trickled down to more mass market vehicles such as the Mark 3 Golf TDI where it

proved to be very popular. These cars were both more economical and more powerful than indirect

injection competitors of their day.

3.3.2 Common rail direct injection

In older diesel engines, a distributor-type injection pump, regulated by the engine, supplies bursts

of fuel to injectors which are simply nozzles through which the diesel is sprayed into the engine's

combustion chamber.

In common rail systems, the distributor injection pump is eliminated. Instead an extremely high

pressure pump stores a reservoir of fuel at high pressure - up to 1,800 bar (180MPa) - in a "common

rail", basically a tube which in turn branches off to computer-controlled injector valves, each of

which contains a precision-machined nozzle and a plunger driven by a solenoid.

http://en.wikipedia.org/wiki/Fuel_injection#Direct_injection

http://en.wikipedia.org/wiki/Megapascal

http://en.wikipedia.org/wiki/Solenoid


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Most European automakers have common rail diesels in their model lineups, even for commercial

vehicles. Some Japanese manufacturers, such as Toyota, Nissan and recently Honda, have also

developed common rail diesel engines.

Different car makers refer to their common rail engines by different names, e.g. DaimlerChrysler's

CDI, Ford Motor Company's TDCi (most of these engines are manufactured by PSA), Fiat Group's

(Fiat, Alfa Romeo and Lancia) JTD, Renault's DCi, GM/Opel's CDTi (most of these engines are

manufactured by Fiat, other by Isuzu), Hyundai's CRDI, Mitsubishi's D-ID, PSA Peugeot Citroen's

HDI, Toyota's D-4D, Volkswagen's TDi, and so on.

3.3.3 Unit direct injection

This also injects fuel directly into the cylinder of the engine. However, in this system the injector

and the pump are combined into one unit positioned over each cylinder. Each cylinder thus has its

own pump, feeding its own injector, which prevents pressure fluctuations and allows more

consistent injection to be achieved. This type of injection system, also developed by Bosch, is used

by Volkswagen AG in cars (where it is called "pump nozzle"), and most major diesel engine

manufacturers, in large commercial engines (Cat, Cummins, Detroit Diesel). With recent

advancements, the pump pressure has been raised to 2,050 bar (205 MPa), allowing injection

parameters similar to common rail systems.

3.3.4 Gasoline direct injection

Gasoline Direct Engines offer many advantages as compared to PFI engines, as regard efficiency

and specific power. To fully exploit this potential a particular attention must be paid to the in

cylinder formation process of air/fuel mixture. More demanding performance is required to the

combustion system, since injectors must provide a fine fuel atomization in considerably short time,

achieving a spray pattern able to interact with in cylinder air motion and piston top surface. This

is made possible through the Common Rail technology allowing an injection pressure one order

of magnitude higher as compared with that of conventional PFI engines. Fuel economy can be

obtained regulating load by mixture leaning, minimizing throttle usage at low loads where

pumping losses are more significant, and requiring charge stratification for a stable ignition and

combustion. Charge stratification can be pursued based mainly on the sole action of the fuel spray

or on its interaction with a specially shaped surface on piston top or with the air bulk motion.

http://en.wikipedia.org/wiki/Megapascal


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Depending on the modality of stratification attainment, different combustion systems can be

considered. The injector design has in turn a key role being the final element of fuel metering

required to the desired spray pattern, injected fuel mass per injection event, resistance to thermal

stress and deposits. Injector housing and orientation with respect to the combustion chamber has

to be carefully chosen, exploiting in this regard the indications of computational fluid dynamics

(CFD), provided by 3D simulations. Some fundamental scheme is provided for the whole high

pressure fuel delivery plant, as employed in current vehicles equipped with GDI spark ignition

engines. The fuel injector is mounted substantially in the center of the cylinder head of the

combustion chamber. Heated catalyzed fuel injector that dispenses fuel substantially exclusively

during the power stroke of an internal combustion engine. Wherein 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. The transonic combustion system (TSCi) brings together the injection and ignition

process to become Injection-Ignition system.

Transonic Combustion uses supercritical-state fuel to radically shift the technological benefits of

the automotive internal combustion engine. TSCi Fuel Injection achieves lean combustion and

super efficiency by running gasoline, diesel, and advanced bio-renewable fuels on modern diesel

engine architectures.

The basis of the combustion process here is that injection of the fuel is delayed to the extent that

the heat release predominantly takes place after TDC of the engine power stroke.

In order to achieve this, the combustion process must have a short delay period, followed by rapid

air fuel mixing and combustion. Such characteristics are achieved by injecting the fuel in the form

of a supercritical fluid.

Supercritical fuel injection facilitates short ignition delay and fast combustion, precisely controls

the combustion that minimizes crevice burn and partial combustion near the cylinder walls, and

prevents droplet diffusion burn.

The engine control software facilitates extremely fast combustion, enabled by advanced micro-

processing technology.

The injection system can also be supplemented by advanced thermal management, exhaust gas

recovery, electronic valves, and advanced combustion chamber geometries.


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CHAPTER 4

4. SUPERCRITICAL FLUID TECHNOLOGY

Many new research studies and technologies are making strides to improve methods of treating

hazardous waste. Researchers are examining many diverse topics for treating chemical

contamination of water and soils. Some of the most recent treatment processes include reverse

osmosis, ozone/peroxide/UV treatment, zero-valent metal reduction, and supercritical fluid

oxidation. The focus of this paper is to explain supercritical fluid oxidation. Also highlighted is

promising research of supercritical fluids and innovative technology for the efficient destruction of

a wide range of industrial hazardous wastes.

Fluids may exist as liquids, gases and supercritical fluids. Supercritical fluids exist at high

temperatures and pressures and exhibit properties between those of a gas and liquid phase.

Supercritical fluid oxidation is a rapid process that completely oxidizes organic contaminates. This

process requires creating a supercritical fluid, as the name implies, to act as a solvent to organics

and initiates inorganic precipitation. The following discussion will cover the background and

process description and design considerations of supercritical fluid oxidation.

A supercritical fluid is a material at an elevated temperature and pressure that has properties between

those of a gas and liquid and is a substance with a temperature above its critical temperature and

critical pressure. Specifically, the supercritical fluid has densities approaching those of a liquid

phase and diffusivities and viscosities approaching those of a gas phase. The temperature and

pressure required to initiate supercritical properties will differ from material to material as viewed

in Table 1. Viewing the temperature-pressure phase diagram of water or CO2, the ranges at a given

temperature and pressure will exhibit liquid, solid, gas, or supercritical properties. From the phase

diagram, the critical point of the material is shown as the highest temperature and pressure, which

the vapour and liquid are in equilibrium. Within the supercritical region, phase changes from liquid

to vapour occurs gradually. The supercritical region differs from the other regions in the phase

diagram because phase changes occur instantaneously at pressures and temperatures lower than the

critical point (e.g., at the triple point). The duration that the injector is open (called the pulse width)

is proportional to the amount of fuel delivered.

A table which shows the supercritical properties of various fluids below:


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.

Solvent Temperature

(oC)

Pressure

(atm)

Density (g/cm3)

Carbon Dioxide 31.1 73.0 0.460

Water 374.15 218.4 0323

Ammonia 132.4 111.5 0.235

Benzene 288.5 47.7 0.304

Toluene 320.6 41.6 0.292

Cyclohexane 281.0 40.4 0.270

Table 4.1

Supercritical Properties for Various Solvents

Once supercritical properties are obtained, organics within the waste stream can either be removed

or destroyed. Removal occurs when an organic waste stream meets a supercritical fluid. Organics

are known to have high solubility in supercritical fluid thus partitioning from the contaminate

inflow. Once the supercritical fluid dissolves the organics, removal of the waste from the

supercritical fluid is accomplished by either reducing the pressure or temperature. Reducing the

temperature or pressure will then decrease the solubility of the organics in supercritical fluid thus

creating a concentrated extract Pressure reduction typically occurs by passing the flow through a

pressure reduction valve. Temperature reduction can occur by passing the flow by a heat exchanger

that is effective in the recycling process to reheat the fluid to the supercritical state.

Once supercritical properties are obtained, organics within the waste stream can either be removed

or destroyed. Removal occurs when an organic waste stream meets a supercritical fluid. Organics

are known to have high solubility in supercritical fluid thus partitioning from the contaminate

inflow. Once the supercritical fluid dissolves the organics, removal of the waste from the

supercritical fluid is accomplished by either reducing the pressure or temperature.

18 | P a g e

Reducing the temperature or pressure will then decrease the solubility of the organics in

supercritical fluid thus creating a concentrated extract Pressure reduction typically occurs by

passing the flow through a pressure reduction valve. Temperature reduction can occur by

passing the flow by a heat exchanger that is effective in the recycling process to reheat the fluid

to the supercritical state.

In supercritical fluid oxidation the organic compound is destroyed rather than removed. In

normal environmental oxidation processes, molecular oxygen takes so long to oxidize an organic

compound at ambient temperatures and pressures that it is considered non-reactive. However,

when air is brought to supercritical conditions, the oxidation potential is vastly increased (Watts,

1998). With the conditions for oxidation potential increased and the ability of the supercritical

fluid to contain all of the organics, the destruction of organics occurs rapidly. LaGrega indicated

that with the proper conditions (temperature = 600 -650oC) the residence or reactor detention

time can be less than one minute with 99.9999% removal efficiencies. From bench scale studies,

various compounds have yielded specific efficiencies, temperatures, and time to obtain

destruction.

Under supercritical conditions, the inorganic compounds are influenced. At ambient

temperature and pressure, the dielectric constant is high thus producing high inorganic solubility.

Under supercritical conditions the dielectric constant decreases with increasing temperature

which then decreases the solubility of inorganic compounds. The reaction of inorganic

compounds to supercritical properties is the inverse to that of hydrocarbon compounds in that

the later increases in solubility with increasing temperature.

4.1 Applications

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

extraction industry. Supercritical fluids put to use for extraction and separations began in the

1970’s and 1980’s. Each year tens of millions of kilograms of the world’s coffee and tea is

decaffeinated using supercritical carbon dioxide.i In Germany for example, most decaffeinated

coffee is produced using this method. Not only does this result in a cleaner industrial process,

but it also ensures that the final product is purer because it has not been exposed to harmful

solvents.

Environmental applications of supercritical fluids are seen in both pollution prevention and

remediation of wastes. Supercritical fluids provide an environmentally friendly alternative for

solvents used in industrial applications. One of the properties of supercritical fluids is their


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excellent ability to dissolve other substances. For example, CO2 is currently being used to

replace harmful hazardous solvents and acts as a reaction medium for materials processing. CO2

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 fluids are important additions to remediation efforts. The solubility behavior of

Naphthalene in Supercritical Carbon Dioxide is shown in figure 4 below. This curve is a general

representation of the behavior of most compounds dissolving in supercritical fluids.

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 is because water is

readily miscible with both oxygen and organics and can achieve very high destruction

efficiencies with very short residence times (1min).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.

4.2 Design Considerations

Challenges facing this new technology are scaling and corrosion. The byproduct of the process

is a highly corrosive mineral acid. In addition, salts will form is bases are added to neutralize.

The salts formed are insoluble in water under these conditions. Another important design

consideration in the development of supercritical water oxidation is the optimization of reactor

operating temperature and feed preheats temperatures.

Increasing temperature or pressure may favour better oxidation or solvent properties, however

cost will increase due to pumps and heating. However to reduce costs, one may pick a

supercritical fluid that has a lower critical temperature and critical pressure. Finally, these

fluids are extremely corrosive to holding chambers and are flammable under supercritical

conditions.


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4.3 The Comparison of Liquid and Supercritical Fluid:

FIG: 4.3.1 LIQUID AND SUPERCRITICAL FUEL

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.

TSCi Fuel Injection achieves lean combustion and super efficiency by running gasoline, diesel,

and advanced bio-renewable fuels on modern diesel engine architectures. Supercritical fluids

have unusual physical properties that Transonic is harnessing for internal combustion engine

efficiency. Supercritical fuel injection facilitates short ignition delay and fast combustion,

precisely controls the combustion that minimizes crevice burn and partial combustion near the

cylinder walls, and prevents droplet diffusion burn. Our engine control software facilitates

extremely fast combustion, enabled by advanced micro processing technology. Our injection

system can also be supplemented by advanced thermal management, exhaust gas recovery,

electronic valves, and advanced combustion chamber geometries.


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4.4 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.

4.5 Multi Tasker

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

addition to gasoline.

FIG: 4.5.1 GAS GUZZLER


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4.6 Benefits Of Tsci Systems

• 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.

• Perfect combustion of fuel.

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

• Knocking is eliminated.

• Engine life is increased

4.7 Pollution Chart

FIG: 4.7.1 POLLUTION CHART


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CHAPTER 5

5. 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 both 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.

The engine is supposed to eventually cost about the same as high-end fuel injection

systems currently on the market, and Transonic Combustion has previously stated that

it wants to start deploying its engine by 2014.

More efficient traditional engines could be a lower-cost way to reduce carbon emissions

from cars before electric vehicles develop into any kind of market. Auto companies will

also be looking for more efficient traditional technologies, because fuel standards in the

U.S. are set to rise from 27 miles per gallon today to 54.5 miles per gallon by

2025, thanks to the Obama administration’s plan.

Transonic Combustion is just one of a variety of start-ups that have emerged in recent

years to try to remake the internal combustion engine to optimize efficiency. Other

start-ups include Eco Motors, Pinnacle Engines, and Liquid Piston.

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.

Perfect combustion of fuel occur.

Less pollution.

http://www.technologyreview.com/news/417918/ultra-efficient-gas-engine-passes-test/

http://www.nytimes.com/2012/01/18/business/energy-environment/new-fuel-economy-rules-win-broad-support.html

https://gigaom.com/cleantech/ecomotors-raises-32-5m-from-khosla-bill-gates-braemar/

https://gigaom.com/cleantech/the-green-overdrive-show-a-super-efficient-engine-video/

https://gigaom.com/cleantech/liquidpiston-unveils-its-ultra-efficient-small-diesel-engine/


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CHAPTER 6

REFERENCES

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http://www.greencarcongress.com/2010/03/transonic-20100304.html#more

http://www.tscombustion.com/

articles.sae.org/7160/

De Boer, C., Chang, J., and Shetty, S., "Transonic Combustion - A Novel Injection-

Ignition System for Improved Gasoline Engine Efficiency," SAE Technical Paper

2010-01-2110, 2010, doi: 10.4271/2010-01-2110.

Heated catalyzed fuel injector for injection ignition engines. US patents US 8079348

B2.

Injector-ignition for an internal combustion engine. US patents US 7546826 B2

Dixon, D. J. and Johnston, K.P., "Supercritical Fluids," In Encyclopedia of Separation

Technology; Ruthven, D.M., Editor, John Wiley, 1997, 1544-1569.

Botany Susana. "Preface." The Journal of Supercritical Fluids 45. 2June 2008 133. 27

May 2008

http://www.sciencedirect.com/science/journal/08968446 .

Wikimedia.

Wikipedia.

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United States Patents - 2011/0057049 A1.

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http://www.freerepublic.com/focus/news/2465019/posts

https://gigaom.com/2012/11/08/the-internal-combustion-engine-2-0-emerges/

http://www.greencarcongress.com/2010/03/transonic-20100304.html#more

http://www.tscombustion.com/

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