spark egnition engine using biogas and natural gas

electricity production through biogas

1. Mar Baselios Christian
College of Engineering &Technology
Department of Electrical and Electronics Engineering
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Department of Electrical and Electronics Engineering
Under the guidance of
Prof. VENMA PRABASH
SUDHEESH.A (MBC21EE012)
Presented By
SPARK IGNITION ENGINES USING BIOGAS AND NATURAL GAS
Technical Seminar on

2. INDEX
5
4
3
2
1
9
8
7
6INTRODUCTION
SI ENGINES OVERVIEW
BIOGAS AS A FUEL
NATURAL GAS AS A FUEL
ENGINE PERFORMANCE AND
OPTIMIZATION
CHALLENGES AND SOLUTIONS
ADVANTAGES
CONCLUSION
REFERENCES

3. INTRODUCTION
Spark Ignition (SI) Engines:
Internal combustion engines where the air-fuel mixture is ignited by a spark plug.
Alternative Fuels:
Biogas:
●Produced from organic waste via anaerobic digestion.
●Renewable, reduces waste, lowers greenhouse gas emissions.
Natural Gas:
●Fossil fuel, primarily methane.
●Cleaner combustion, fewer pollutants, higher octane rating.
Relevance to SI Engines:
●Compatibility: Both fuels can be used in SI engines with minimal modifications.
●Performance: Comparable to gasoline with lower emissions and potential cost savings.
Research Focus:
●Goal: Optimize SI engines for biogas and natural gas to improve efficiency and reduce emissions.
●Significance: Supports the transition to sustainable energy in transportation and beyond.

4. Research Objectives
Primary Goal:
●Investigate the performance of Spark Ignition (SI) engines using biogas and natural gas as alternative
fuels.
Key Objectives:
Enhance Exergy Efficiency:
●Focus: Improve the second-law (exergy) efficiency of SI engines.
●Importance: Maximizing energy use to reduce waste and improve overall engine performance.
Optimize Engine Design:
Target: Develop a conceptual design for SI engines that maximizes performance when using biogas and
natural gas.
Considerations: Combustion chamber geometry, turbulence, and compression ratio adjustments.
Significance:
Impact: Contributing to more efficient and sustainable engine technologies, reducing reliance on
conventional fuels, and lowering environmental impact.

5. Background
1
2Natural Gas:
●Source: A fossil fuel composed mostly of
methane (CH ).
₄
Biogas:
●Source: Produced from organic materials
like animal waste and agricultural
residues.
●Composition: Mainly methane (CH ) and
₄
carbon dioxide (CO ).
₂
3
Spark Ignition (SI) Engines:
●Operation: Combustion is initiated by a spark plug igniting the air-fuel mixture.
●Compatibility with Alternative Fuels:Both biogas and natural gas can be used with
minimal modifications to existing SI engines.Offers similar performance to gasoline with
environmental and economic benefits.

6. Spark Ignition Engines
Overview of Spark Ignition
(SI) Engines
1
Basic Principles:
Operation: SI engines use a spark plug to ignite the air-fuel mixture in the combustion chamber, causing an explosion
that drives the engine.
Components:
●Spark Plug: Initiates combustion.
●Combustion Chamber: Area where the air-fuel mixture is burned.
●Piston: Moves to convert combustion energy into mechanical work
2 Importance of Compression Ratio:
●Definition: The ratio of the volume of the combustion chamber at its largest capacity (bottom dead center)
to its smallest capacity (top dead center).
3
Combustion Process:
●Stages:
●Intake: Air-fuel mixture enters the cylinder.
●Compression: Mixture is compressed.
●Power: Spark plug ignites the mixture, causing an explosion that pushes the piston.
●Exhaust: Burnt gases are expelled.

7. Knocking in SI Engines
What is Knocking?:
●Definition: Knocking (or "engine knock") occurs
when the air-fuel mixture in an engine's cylinder
detonates prematurely, causing a sharp and
damaging knocking noise.
Factors Contributing to Knocking:
●Fuel Quality: Fuels with lower octane ratings are more
prone to knocking.
●Engine Temperature: Higher operating temperatures can
lead to knocking.
Impact on Engine Performance:
●Efficiency Loss: Knocking reduces engine efficiency
because the combustion occurs at the wrong time,
wasting fuel energy.
●Damage: Prolonged knocking can cause severe
damage to engine components like the piston,
cylinder walls, and valves.
Strategies to Suppress Knocking:
●Use of Higher-Octane Fuels: Biogas and natural gas
generally have higher methane numbers, which reduce
knocking.
●Turbulence Enhancement: Increasing turbulence in the
combustion chamber helps in even and controlled
combustion.
Understanding Knocking in Spark
Ignition Engines

8. Methane Number (MN)
What is Methane Number (MN)?:
●Definition: Methane Number (MN) is a measure of a fuel's
resistance to knocking in an engine, similar to the octane
rating for gasoline.
●Scale: MN is measured on a scale where pure methane has
an MN of 100, and hydrogen has an MN of 0.
Factors Affecting MN:
●Fuel Composition: The presence of higher hydrocarbons
(like ethane, propane) lowers the MN, while a higher
methane content increases it.
●Biogas and Natural Gas: Typically, biogas has a lower MN
due to the presence of CO2, while natural gas usually has
a high MN, making it less prone to knocking.
Importance of MN in Engine Performance:
●Knocking Resistance: A higher MN indicates better
resistance to knocking, making the fuel more suitable for use
in high compression ratio engines.
●Fuel Selection: MN helps in selecting the appropriate fuel or
fuel blend for specific engine designs to minimize knocking
and maximize efficiency.
Relevance to the Study:
●Optimizing Engine Design: The study uses MN to
evaluate and optimize the design of SI engines for running
on biogas and natural gas.
●Engine Tuning: Understanding MN allows for better tuning
of the engine’s compression ratio and ignition timing,
reducing the likelihood of knocking.
Understanding Methane Number (MN) and Its
Importance

9. Cooperative Fuel
Research (CFR) Engine
Determining Methane Number (MN):
•Methodology: Comparing the knocking behavior of test fuels against standard methane-hydrogen mixtures.
•Importance: Establishing the MN helps assess the suitability of biogas and natural gas for use in SI engines
under various conditions.
What is a CFR Engine?
●Definition: A standardized, single-cylinder engine specifically designed for fuel testing and
research purposes.
●Purpose: Used to determine fuel characteristics such as knock resistance, octane number,
and Methane Number (MN).
Functions of the CFR Engine in This Study:
Measuring Critical Compression Ratio (CCR):
●CCR Definition: The highest compression ratio at which a fuel can operate without causing engine
knock.

10. Advantages of Using CFR Engine:
●Standardization: Provides consistent and comparable results across different studies and fuel types.
●
Precision: Accurate control over engine parameters such as compression ratio, ignition timing, and fuel-air mixture.
●Versatility: Capable of testing a wide range of fuels, including gaseous and liquid forms.
●
Engine Optimization: Data from CFR engine tests inform adjustments in SI engine design to minimize knocking and
enhance efficiency when using biogas and natural gas.
●Fuel Quality Assessment: Enables a thorough evaluation of alternative fuels' performance characteristics under controlled
conditions.
●Benchmarking: Provides baseline data to compare alternative fuels against conventional fuels like gasoline.

11. Exergy Efficiency in SI Engines
What is Exergy Efficiency?
●Definition: Exergy efficiency refers to the efficiency with which a
system converts available energy (exergy) into useful work,
considering the second law of thermodynamics.
Importance in SI Engines:
●Maximizing Useful Work: Higher exergy
efficiency means more of the fuel's available
energy is converted into useful mechanical
work, reducing waste.
●Reducing Irreversibilities: Identifying and
minimizing sources of energy losses, such as
friction, heat loss, and incomplete combustion.
Factors Affecting Exergy Efficiency:
●Thermodynamic Losses: Losses due to heat transfer, exhaust gases,
and friction within the engine components.
●Fuel Type: Different fuels have different energy contents and
combustion characteristics, affecting their exergy efficiency.
Understanding Exergy Efficiency in Spark Ignition
Engines

12. Application to Biogas and Natural Gas:
Biogas: The presence of CO in biogas can lead to lower exergy efficiency compared to natural gas due to lower energy
₂
content and potential combustion inefficiencies.
Natural Gas: Generally offers higher exergy efficiency due to its higher methane content and better combustion
characteristics.
Optimization: The study aims to enhance the exergy efficiency of SI engines when running on biogas and natural gas by
optimizing engine design and operating conditions.
Sustainability: Improving exergy efficiency contributes to more sustainable engine operation by reducing fuel consumption
and emissions.

13. Engine Design Considerations for
Alternative Fuels
1
Compression Ratio:
●Optimization: The compression ratio must be optimized for each fuel to maximize efficiency and minimize knocking.
2
Combustion Chamber Design:
●Geometry: The shape of the combustion chamber influences the air-fuel mixture’s flow and combustion quality.
●Turbulence Enhancement: Introducing turbulence can improve the mixing of air and fuel, leading to more complete
combustion and reducing the likelihood of knocking.
3
Ignition Timing:
●Precise Control: The timing of the spark is critical for achieving optimal combustion and minimizing knock.
●Fuel-Specific Adjustment: Different fuels require different ignition timing; natural gas might require earlier ignition
compared to biogas.
Key Design Considerations for SI Engines Using Biogas
and Natural Gas

14. 6
5
4
Exhaust Gas Recirculation (EGR):
Purpose: EGR is used to reduce NOx emissions and can help control knocking by lowering the peak combustion
temperature.
Material Selection:
Durability: Engine materials must withstand the specific conditions created by alternative fuels, such as higher
temperatures or corrosive components (e.g., H S in biogas).
₂
Fuel Delivery System:
System Compatibility: Ensuring that the fuel delivery system (e.g., injectors, fuel lines) is compatible with the specific
properties of biogas and natural gas.

15. Combustion Characteristics of
Biogas and Natural Gas
1. Combustion Speed:
Biogas:
●Lower Combustion Speed: Due to the presence of CO₂, biogas burns more slowly than natural gas.
.
Natural Gas:
●Higher Combustion Speed: Natural gas, primarily methane, burns more rapidly and completely.
Comparative Combustion Characteristics of Biogas and Natural
Gas

16. 2. Flame Propagation:
Biogas:
●
Slower Flame Speed: The slower flame speed of biogas can cause uneven combustion,
which may increase the risk of knocking.
Natural Gas:
●
Faster Flame Propagation: Ensures more uniform combustion, reducing the likelihood of
knocking and improving power output.
3. Energy Content:
Biogas:
●Lower Energy Density: The presence of non-combustible gases like CO₂ lowers the overall
energy content of biogas.
Natural Gas:
●Higher Energy Density: With a high methane content, natural gas provides a higher energy
content per unit volume, leading to better engine performance.

17. 4. Emission Characteristics:
Biogas:
●Lower CO and HC Emissions: Due to its lower carbon content, biogas typically produces fewer carbon monoxide
(CO) and hydrocarbon (HC) emissions.
Natural Gas:
Clean Combustion: Burns cleaner than biogas, with lower emissions of CO, HC, and particulate matter.
NOx Emissions: Natural gas also tends to produce lower NOx emissions compared to conventional fuels, especially
when combustion is properly controlled.
5. Combustion Stability:
Biogas:
Variability: The composition of biogas can vary, leading to fluctuations in combustion stability.
Natural Gas:
Stable Combustion: Consistent composition leads to stable and predictable combustion behavior, making it easier to
optimize engine settings.

18. Emissions Profile of Biogas and
Natural Gas in SI Engines
1
Carbon Dioxide (CO ) Emissions:
₂
Biogas:
●Lower Net CO Emissions: Considered carbon-neutral since the CO emitted during combustion is offset by the CO
₂ ₂ ₂
absorbed during the organic material's growth phase.
Natural Gas:
●Lower CO Emissions Compared to Gasoline: Burns cleaner with fewer CO emissions per unit of energy produced.
₂ ₂
2
Nitrogen Oxides (NOx) Emissions:
Biogas:
●Potential for Higher NOx: Due to the presence of CO , which can lead to higher combustion temperatures and
₂
thus more NOx formation.
Natural Gas:
●Lower NOx Emissions: Typically produces lower NOx compared to gasoline and biogas, especially with
optimized combustion processes.

19. 3
4
Hydrocarbon (HC) Emissions:
Biogas:
●
Lower HC Emissions: Biogas tends to produce fewer unburnt hydrocarbons due to its higher methane content.
●Combustion Efficiency: Incomplete combustion can still lead to higher HC emissions if engine settings are not
optimized.
Natural Gas:
●
Very Low HC Emissions: Natural gas is known for its clean-burning properties, resulting in significantly lower HC
emissions compared to gasoline.
Carbon Monoxide (CO) Emissions:
Biogas:
●
Lower CO Emissions: Due to more complete combustion, biogas produces lower levels of carbon monoxide.
●
Engine Tuning: Proper tuning is essential to maintain low CO emissions.
Natural Gas:
●
Minimal CO Emissions: Natural gas combustion typically results in very low CO emissions, making it an
environmentally friendly option.

20. Engine Performance Optimization with
Biogas and Natural Gas
1Air-Fuel Ratio (AFR) Optimization:
●Importance: The AFR is crucial in achieving optimal
combustion efficiency and minimizing emissions.
Biogas:
●Lean Burn Operation: Due to its lower energy content,
biogas engines often operate with a leaner AFR, improving
fuel economy but requiring precise control to avoid
knocking.
Natural Gas:
●Stoichiometric AFR: Typically operates closer to the
stoichiometric AFR, balancing power output and emissions
while maintaining combustion stability.
2 Ignition System Tuning:
Biogas:
●Advanced Ignition Timing: Due to slower combustion, biogas
engines may benefit from advanced ignition timing to ensure
complete combustion.
●Ignition Energy: High-energy ignition systems might be
necessary to reliably ignite the lean biogas-air mixture.
Natural Gas:
●Optimized Ignition Timing: Natural gas, with its faster
combustion characteristics, requires precise ignition timing to
maximize efficiency and minimize knock.
3
Fuel System Adaptations:
Biogas:
●Fuel Pre-Treatment: Due to impurities like H S, biogas may require filtering and moisture removal to prevent corrosion and ensure
₂
smooth operation.
●Injection System: Modified injection systems may be needed to handle the lower density and higher moisture content of biogas.
Natural Gas:
●High-Pressure Injection: Natural gas engines often use high-pressure direct injection to improve atomization, combustion efficiency,
and power output.
Strategies for Optimizing Engine Performance Using Biogas and
Natural Gas

21. Results: Exergy Efficiency of Biogas and
Natural Gas in SI Engines
Concept:
●Exergy: Represents the maximum useful work possible during a process that brings the system into
equilibrium with a reference environment.
●Exergy Efficiency: Measures how efficiently an energy conversion process (such as combustion in an
engine) uses available energy to perform useful work.
●Importance: Higher exergy efficiency indicates better performance and less energy waste in the form
of heat and emissions.
Bore x Stroke Ratio:
Exergy Efficiency in
Biogas and Natural Gas
Engines:
Biogas:
●Lower Exergy Efficiency: Due to the lower calorific value and higher CO content, biogas generally
₂
shows lower exergy efficiency compared to natural gas.
●Factors Affecting Efficiency
●Combustion Process: Incomplete combustion and variations in fuel composition can lead to exergy
losses.
●Engine Tuning: Proper engine tuning, including optimal air-fuel ratio and ignition timing, is crucial to
improving exergy efficiency.

22. Natural Gas:
●Higher Exergy Efficiency: Natural gas, with its higher energy content and more consistent composition,
generally achieves better exergy efficiency in SI engines.
Factors Contributing to Higher Efficiency:
●Stable Combustion: Consistent fuel quality and cleaner burning properties result in more efficient energy
conversion.
●Engine Design: Engines specifically designed or optimized for natural gas can maximize exergy
efficiency, reducing waste energy.
●Efficiency Metrics:
●Biogas: Typically shows exergy efficiency in the range of 30-35% depending on engine
design and operating conditions.
●Natural Gas: Exhibits higher exergy efficiency, often in the range of 35-45%, due to
better combustion properties and optimized engine performance.
●
●Implications:
●Biogas: While less efficient, biogas's renewable nature and carbon neutrality can offset
the lower exergy efficiency in some applications.
●Natural Gas: Higher efficiency makes natural gas a more attractive option where fuel
availability and infrastructure support its use.
Comparative
Results:

23. Challenges in Using Biogas and Natural
Gas in SI Engines
1. Variability in Biogas Composition:
●Inconsistent Quality: Biogas composition can vary widely based on the source of the biomass and the production
process, affecting engine performance.
●Impact: Variability in methane content and the presence of impurities (like CO and H S) can lead to inconsistent
₂ ₂
combustion, knocking, and reduced engine efficiency.
●Solution: Requires advanced engine management systems that can adapt to changing fuel properties in real-time.
Key Challenges in Implementing Biogas and Natural Gas as Fuels for
Spark Ignition Engines

24. 2. Lower Energy Density:
Biogas:
●Challenge: The lower calorific value due to CO content means biogas has less energy per unit volume, requiring more fuel
₂
to achieve the same power output.
●Impact: This can lead to reduced engine performance and higher fuel consumption unless compensated by engine
modifications like turbocharging.
Natural Gas:
●Still Lower Than Gasoline: While natural gas has a higher energy density than biogas, it still offers less energy per volume
than gasoline, which can limit performance in conventional engines.
3. Knock Tendency:
Biogas:
●Increased Knock Risk: The presence of CO in biogas can increase the likelihood of engine knocking, especially under high
₂
load conditions.
Natural Gas:
●Lower Knock Risk: Generally has a higher Methane Number, making it less prone to knocking, but still requires optimization of
engine parameters to prevent it under high boost or load conditions.

25. 5. Engine Wear and Maintenance:
Biogas:
●
Corrosive Effects: Impurities like H₂S can cause corrosion in engine components, leading to higher maintenance costs and shorter
engine life.
Natural Gas:
●
Lower Maintenance: Natural gas is cleaner-burning, resulting in less engine wear and lower maintenance requirements compared to
biogas and traditional fuels.

26. Advantages of Using Biogas and Natural
Gas in SI Engines
1. Environmental Benefits:
•Biogas: Carbon-neutral, reduces CO and HC emissions.
•Natural Gas: Lower CO , NOx, and particulate emissions.
₂
2. Energy Security:
●Biogas: Renewable, reduces fossil fuel dependence.
●Natural Gas: Abundant supply, stable energy source.
3. Engine Performance:
●Biogas: Adaptable, reduces knock with proper tuning.
●Natural Gas: High efficiency, knock-resistant.
4. Economic Benefits:
●Biogas: Cost-effective, supports local production.
●Natural Gas: Lower operating costs.

27. Conclusion
Biogas and natural gas offer sustainable alternatives to
traditional fossil fuels, making them vital in the transition to
greener energy sources. These fuels significantly lower
greenhouse gas emissions, with biogas being carbon-neutral and
natural gas emitting fewer pollutants. When engines are
properly tuned, both fuels can enhance performance and
efficiency, making them practical choices for spark ignition
engines.
While challenges like fuel variability and lower energy density
exist, they can be addressed with advanced technologies and
strategic adaptations. By embracing these fuels, we move closer
to a future of cleaner, more sustainable transportation.
Additionally, the economic benefits, such as reduced operational
costs, align with global efforts to combat climate change and
promote environmental responsibility.

28. References
Part 2. Conceptual design of efficient spark ignition engines using biogas and natural gas.
Juan Pablo Gómez Montoya,Mechanical Engineering Department,Universidad,Tecnológica del Perú,Lima-Peru,
[email protected]