The document discusses air/fuel ratio control in combustion engines. It defines key combustion terminology like stoichiometric ratio and explains the importance of controlling the air/fuel ratio for efficiency and emissions. Different methods for controlling air/fuel ratio are presented, including inspirators, mechanically-linked valves, electronically-linked valves, and fully metered mass flow control. The advantages and disadvantages of each method are provided. Throttle valves, air management valves, and electronic throttle actuators are also described.

1. PRESENTED TO:
SIR MUZAMMIL
PRESENTED BY:
HAFIZ SHAHREYAR RAZA
SHAHRUKH WASEEM

2. Overview
 Intro toAir/Fuel Ratio
 CombustionTerminology and
Fundamentals
 Importance ofAir/Fuel Ratio Control
 Methods ofAir/Fuel Ratio Control
 Pros and Cons of Each Method

3. Throttle valve
• A valve designed to regulate the supply of a fluid
(as steam or gas and air) to an engine and
operated by a hand wheel, a lever, or
automatically by a governor.

4. Combustion Terminology
 Combustion –The rapid oxidation of a fuel,
usually via the oxygen present in air, resulting
in the release of energy (heat and light).
 Combustion is the CONTROLLED rapid oxidation of
a fuel.
 Explosion is the UNCONTROLLED rapid oxidation
of a fuel.
 Stoichiometric Ratio –The perfect amount of
oxygen and fuel mixed during combustion
such that nothing is left over.
 Example Reaction with Natural Gas (CH4):
 CH4 + 2O2 + 8N2  CO2 + 2H2O + 8N2 +
heat

5. Combustion Terminology (cont.)
 Excess air / lean – When more air (oxygen)
is present than necessary to combust the
fuel, resulting in left over oxygen.
 Most industrial combustion applications
are run with excess air to ensure that there
is no wasted fuel.
 Example: A Natural Gas burner which
receives 15 parts air for every part fuel is
running with 50% excess air. This burner can
be described as “running lean”.
 CH4 + 3O2 + 12N2  CO2 + 2H2O + O2 + 12N2 +
heat

6. Combustion Terminology (cont.)
 Excess fuel / rich –When less air is
present than necessary to combust the
fuel, resulting in unburned fuel.
 Certain applications that require a long,
luminous flame or need to control the amount
of oxygen within the combustion chamber
would have burners set-up to run with excess
fuel.
 Sometimes called “sub-stoich” since it’s
below the stoichiometric air-to-fuel ratio.
 2CH4 + 2O2 + 8N2  CH4 + CO2 + 2H2O + 8N2 +
heat

7. Combustion Fundamentals
 All fuels have a lower and upper
flammability limit.
 Combustion can only occur between these
limits.
 When changing the firing rate of a burner,
both the air and fuel need to travel together
to stay between these limits.
Type of Gas LFL UFL Stoich
Natural Gas
(CH4)
5.0% 15.0% (10:1) - 9.1%
Propane Gas
(C3H8)
2.1% 9.5% (25:1) - 3.8%
Butane Gas
(C4H10)
1.8% 8.4% (32:1) - 3.0%

8. Optimal Air/Fuel ratio control
 Prevent nuisance shut-downs
 Improper air/fuel ratio can cause the flame
safeguard to lose the flame signal
 Improve fuel efficiency
 Improper air/fuel ratio can waste fuel
 Help obtain tighter control for emissions driven
applications
 Improper air/fuel ratio can increase NOx or CO
production
 Help obtain better temperature control
 Improper air/fuel ratio can make controlling
temperature more difficult

9. Inspirators
 High pressure fuel is delivered to the inlet of the
inspirator
 Venturi tube design pulls combustion air into the
inspirator
 Ratio control dictated by the size of the fuel
nozzle and an air adjustment damper

10. Inspirators (cont.)
 ~40:1Turndown
 Pros: Low Cost,
Simple Design,
Available in many
sizes
 Cons: Low
turndown, Minimal
characterization
 Critical Component:
Gas Nozzle/Spud

11. Cross-Connected Ratio
Regulators Composed of the following components:
 Air Control Device (Control Valve or VFD)
 Proportionator/Ratio Regulator
 Limiting Orifice
 Control signal sent to the air control device, and
an impulse line from air manifold feeds the fuel’s
ratio regulator to adjust the fuel flow.

12. Cross-Connected Ratio Regs
(cont.) ~20:1
Turndown
 Pros: Flexible
Installation,
Low Cost
 Cons:
Minimal
characterizat
ion
 Critical
componen
t: Impulse
Line

13. Mechanically-Linked Control
Valves Air Valve and FuelValve connected via
mechanical linkage.
 Commonly found in boiler applications
 Characterizable fuel valves offer adjustment
capabilities for the entire range of operation.
 Good for multi-fuel and oil-fired applications.

14. Mechanically-Linked Valves
(cont.) ~40:1Turndown
 Pros: Higher
Turndown,
More
Characterizati
on
 Cons: Higher
Torque
Requirements for
Control Motors,
Less Flexible
Installation
 Critical
Component:
air and fuel
valves

15. SHAHRUKH WASEEM

16. Electronically-Linked Control
Valves
located near each
other.
 Sometimes referred to as “Parallel Positioning”
 System’s control interface receives single control
signal, and controls multiple actuators (can
control up to 4).
 Built-in safeties ensure that actuators travel
together to maintain ratio.
 Actuators are characterizable, allowing for
individually defined flow curves.
 Commonly used in emissions driven
applications due to repeatability of control
and level of characterization.
 Flexible to install since air and fuel valves do not
need to be

17. Electronically-Linked Valves
(cont.) ~40:1Turndown
 Pros: Flexible
Installation,
Great Control
Resolution
 Cons: Increased
Complexity and
Cost with
Additional
Components
 Critical
Component:
Control
Interface

18. Fully Metered Mass Flow Control
 Air and Fuel flow meters used in
conjunction with electronically-linked
control valves.
 Valve positions determined by central control
interface based on heat requirement and flow
feedback.
 Commonly used in emissions driven
applications due to repeatability of control
and level of characterization.
 Flexible to install since air and fuel valves do not
need to be located near each other.

19. Fully Metered Mass Flow Control
(cont.) ~20:1Turndown
 Pros: BestAvailable
ControlTechnology,
Self-
tuning/correcting
with flow feedback
 Cons: More
expensive, Can be
slower to respond to
aggressive control
signals.
 Critical
Component:
Interface Panel

20. FUNCTION
• In general terms, the throttle valve must regulate
the air or mixture supply for the
combustion engine. Depending on the engine
concept, this serves different purposes.
• In the case of petrol engines, speed and power
output are regulated by means of fresh air or
mixture dosing.
• Diesel engines generally do not need a throttle
valve. However, in modern diesel cars, throttling
the amount of intake air facilitates precision
control for exhaust gas recirculationand stops
the engine from shaking when the ignition is
switched off.

21. ELECTRONICTHROTTLE
ACTUATORS:
• With electromotive throttle actuators, the
position of the throttle valve is regulated
mechanically via the accelerator Bowden cable.
The throttle valve electronics forward the
position of the throttle valve to the engine
control unit as an electrical signal. This
information is compared with other up-to-date
data from a variety of engine management
sensors. The engine control unit permanently
calculates the optimum throttle position for
consumption and exhaust gas emissions and
sends this information back to the throttle valve
as an electrical control signal. The position of the
throttle valve is then fine-tuned with the
assistance of a servomotor

23. Electronic throttle actuators
• With electronic throttle actuators, there is no
direct connection to the accelerator pedal. The
driver's desired load is captured by an electronic
accelerator pedal (electromotive throttle
actuator). The engine management permanently
matches this signal to all other available data
from the engine sensors, using the information
obtained to calculated the optimum throttle
position for the prevailing situation. The
electronic throttle actuator is controlled
exclusively using the control signal from the
engine management and with the assistance of a
servomotor

24. Air management valves:
• If throttle valves are used in diesel engines, they
are generally referred to as air management
valves. Air management valves can be with or
without integrated control electronics. As
indicated above, air management valves throttle
the intake air in the intake air system of diesel
engines via electromotive means in order to
achieve precision controlled exhaust gas
recirculation and prevent the inconvenient
shaking that would otherwise occur when the
engine is switched off.

26. Air flap servomotors:
• Air flap servomotors are electrical actuators with
integrated position sensor and optional
integrated electronics. They facilitate the
continuous adjustment of intake pipe flaps or
turbocharger guide vanes, for example, and, by
means of more precise control, are able to
replace conventional pneumatic drives which are
no longer sufficient for the advanced
requirements that have to be met.

28. SAFETY
The perfect function of the throttle valve is the key
to optimum power development of the vehicle in
critical situations. As such, the throttle valves
make an essential contribution to improved road
safety

29. DEPRECIATION
• Throttle valves are maintenance-free. They are
designed to last the entire service life of the
vehicle. Poor maintenance (missing oil change
intervals, for example) can lead to soiling of the
throttle valve and cause deposits to build up,
resulting in premature wear or even complete
failure. For this reason, compliance with the
maintenance intervals prescribed by the vehicle
manufacturer is essential.

30. ENVIRONMENTAL PROTECTION
• Optimum operation of the combustion engine
and minimum pollutant emissions rely on
precision control of the intake air. Throttle valve
modules with integrated electronics enable the
intake air quantity to be exactly matched to the
prevailing operation conditions independently of
the driver's performance requirements. As such
they make an important contribution to effective
fuel combustion and low pollutant emissions