Improve engine efficiency with transonic combustion

Transonic Combustion
STC/SPRT/ME/2016-17 Page 1
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

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.

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,”

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 EngineGasoline Engine Diesel Engine
Fig 3.1: Brief Classification of I.C Engines

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.

 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

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

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

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”.

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

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

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.

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

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.

5. DISADVANTAGES
 Might be Costly.
 Extraction of supercritical fluid is may be difficult.
 Needs regular maintenance.
 If ECU goes wrong somehow efficiency affects.

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.

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.

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

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]

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