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Controlled Auto Ignition
By-Intakhab khan(VTP2984)
Seminar
Prime Movers and Transmission
2161AU201
Under- Dr. S Jaichandar
Introduction
• CAI known as Controlled auto ignition are the engine in
which we get maximum fuel economy and low emission.
They are also known as Gasoline HCCI engine.
• A homogeneous Gasoline fuel is auto ignited without the use
of Spark plug and auto ignition at various point
• They have the advantage of SI on emissions and CI on fuel
economy.
• The 𝑁𝑂𝑥 emission are even less than that of SI engine while
HC is little higher due to low operating temperature and
unburnt gases. CO emission is observed lower than that of SI
• CAI is more under research and only one 4 cylinder have
used it for commercial vehicle. (MAZDA SKYACTIV 3)
02/12/2020 Controlled Auto Ignition 2
Advantages
- Low 𝑁𝑂𝑥 emission(due to less engine
operating and peak temperature)
- High fuel economy(since they run leaner)
- No need of spark
- Lower HC and CO emission compared to
CI engine
- Can run at too lean mixture
- No dependence on flame travel
- Easy after treatment compared to CI and
HCCI diesel
- No local heating
02/12/2020 Controlled Auto Ignition 3
Disadvantages
- Less control in combustion timing and heat release
rate
- Knocking is an issue
- Misfiring issue
- Partial burning issue
- Low range of operation
- To reach ignition temperature the Compression
ratio is increased hence walls must be made thicker
- Problem during cold start
- Less peak power
- At low speed the exhaust temperature is also less
hence have to design proper catalytic converter for
proper function
CAI operating range
02/12/2020 Controlled Auto Ignition 4
Methods to achieve CAI
• EGR(Exhaust gas recirculation)(Hot and Cold) and preheating
• Exhaust gas trapping
• Control of valve timing and lift for exhaust gas trapping or
Early Inlet Valve open
• Controlling Air fuel ratio
• Varying engine speed
• Increasing compression ratio
• Controlling coolant temperature
• Fuel additives
• Controlling injection timing(In case of GDI)
02/12/2020 Controlled Auto Ignition 5
A. EGR (Exhaust gas recirculation)
1. Hot EGR
2. Cold EGR
With hot EGR the inlet gas can be heated to get auto ignition known as preheating and also the
dilution takes place reducing the amount of oxygen per intake. Also the burnt gas increases the
heat capacity increasing the combustion duration. Exhaust gas can also participate chemically in
combustion increasing the combustion duration. start of ignition is advanced due to increased
temperature. Also by decreasing amount of oxygen the peak temperature is reduced reducing 𝑁𝑂𝑥
Varying EGR content affects the combustion most
02/12/2020 Controlled Auto Ignition 6
Methods to achieve CAI
02/12/2020 Controlled Auto Ignition 7
A. EGR (Exhaust gas recirculation)
Effect of cold EGR
Combustionduration
Effect of Hot EGR
B. Exhaust Gas Trapping
• Exhaust gas trapping is done by varying the valve opening and closing duration and timing.
The benefit of Exhaust gas trapping it to create dilution of the air and fuel inside the cylinder
chamber and also to increase the combustion chamber temperature helping in auto ignition.
• But at low speeds the exhaust temperature is not that high hence it won’t help in auto ignition.
• Also due to exhaust gas trapping there is the distribution of temperature as shown below
experimentally which is good for getting auto ignited
• RGF- Residual gas fraction
02/12/2020 Controlled Auto Ignition 8
C. Variable valve timing and lift
• In case of Early inlet valve opening some of the burnt gases are pushed into the inlet manifold
heating the inlet air and diluting the inlet air. This is known as back flow strategy
02/12/2020 Controlled Auto Ignition 9
C. Variable valve timing and lift
• Early inlet valve opening is providing better auto ignition
• In case of exhaust gas trapping the Negative valve overlap must happen.
• Also variable valve actuation can be used to de activate different cylinder at low load demand
02/12/2020 Controlled Auto Ignition 10
D. Controlling AF ratio
• CAI engine runs leaner but if it is too lean the partial burning may take place or if it is too rich
the misfiring may take place due to low temperature(lambda=> airf/fuel). Also running too lean
leads to less peak temperature and hence less 𝑁𝑂𝑥. But during misfiring and partial burning lot
of HC and CO is emitted. Also rich mixture increases 𝑁𝑂𝑥.
02/12/2020 Controlled Auto Ignition 11
02/12/2020 Controlled Auto Ignition 12
D. Controlling AF ratio
02/12/2020 Controlled Auto Ignition 13
D. Controlling AF ratio
• By engine speed if it is too low the heat will be lost to walls(implies partial burning) and if
the engine speed is high it will get less time to get it transferred to the walls(implies knock
tendency)
02/12/2020 Controlled Auto Ignition 14
E. Varying engine speed
• By increasing compression ratio if it is too less no auto ignition or partial burning if it is
too high knocking takes place
02/12/2020 Controlled Auto Ignition 15
F. Varying Compression ratio
• On reducing coolant temperature to 65°C, the upper limit can be extended up to 14% while
with increasing the coolant temperature the lower limit can be extended up to 28% for a
single-cylinder engine operating in CAI through the negative valve overlap approach.
• Additive-like Dimethyl-ether(DME) have low octane number and also water can be used as
additive to reduce the combustion rate. Also affects the ignition timing and reduces NOx.
02/12/2020 Controlled Auto Ignition 16
G. Varying Coolant temperature
H. Additives
I. Controlling of injection timing
• In case of GDI(Gasoline Direct Injection) the injection timing to control the start of
ignition which is difficult during the port injection and throttle body injection in case of
CAI.
• ECU (Electronic control unit) manages the amount of fuel injected and timing of injection
as per the condition of operation and feedback from the previous combustion.
Further Innovation in CAI
• Hybridization of concept between Spark ignition at low speed and cold starting condition and
CAI at other speeds
• Other concept of hybridization is use of spark plug to just create the pressure by combusting
small stratified charges near spark plug and rest all combusts by auto ignition.
• The innovation is used in MAZDA Skyactiv X which is only the commercial 4 stroke engine
in the market.
02/12/2020 Controlled Auto Ignition 17
MAZDA SKYACTIV-X
02/12/2020 18Controlled Auto Ignition
References
[1]. Chen, Tao, et al. "Methods to achieve HCCI/CAI combustion at idle operation in a 4VVAS
gasoline engine." Applied energy 116 (2014): 41-51.
[2]. Milovanovic, Nebojsa, and Rui Chen. A review of experimental and simulation studies on
controlled auto-ignition combustion. No. 2001-01-1890. SAE Technical Paper, 2001.
[3]. Zhao, H., Z. Peng, and N. Ladommatos. "Understanding of controlled autoignition combustion
in a four-stroke gasoline engine." Proceedings of the Institution of Mechanical Engineers, Part D:
Journal of Automobile Engineering 215.12 (2001): 1297-1310.
[4]. Allen, Jeff, and Don Law. Variable valve actuated controlled auto-ignition: speed load maps
and strategic regimes of operation. No. 2002-01-0422. SAE Technical Paper, 2002.
[5]. Kulzer, Andre, et al. "Controlled auto-ignition." AutoTechnology 7.4 (2007): 56-59.
[6]. Zhao, Hua. HCCI and CAI engines for the automotive industry. Elsevier, 2007.
[7]. Saurabh et al. “Seminar on HCCI and CAI engine” 2016-2017.
02/12/2020 Controlled Auto Ignition 19

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Controlled auto ignition

  • 1. Controlled Auto Ignition By-Intakhab khan(VTP2984) Seminar Prime Movers and Transmission 2161AU201 Under- Dr. S Jaichandar
  • 2. Introduction • CAI known as Controlled auto ignition are the engine in which we get maximum fuel economy and low emission. They are also known as Gasoline HCCI engine. • A homogeneous Gasoline fuel is auto ignited without the use of Spark plug and auto ignition at various point • They have the advantage of SI on emissions and CI on fuel economy. • The 𝑁𝑂𝑥 emission are even less than that of SI engine while HC is little higher due to low operating temperature and unburnt gases. CO emission is observed lower than that of SI • CAI is more under research and only one 4 cylinder have used it for commercial vehicle. (MAZDA SKYACTIV 3) 02/12/2020 Controlled Auto Ignition 2
  • 3. Advantages - Low 𝑁𝑂𝑥 emission(due to less engine operating and peak temperature) - High fuel economy(since they run leaner) - No need of spark - Lower HC and CO emission compared to CI engine - Can run at too lean mixture - No dependence on flame travel - Easy after treatment compared to CI and HCCI diesel - No local heating 02/12/2020 Controlled Auto Ignition 3 Disadvantages - Less control in combustion timing and heat release rate - Knocking is an issue - Misfiring issue - Partial burning issue - Low range of operation - To reach ignition temperature the Compression ratio is increased hence walls must be made thicker - Problem during cold start - Less peak power - At low speed the exhaust temperature is also less hence have to design proper catalytic converter for proper function
  • 4. CAI operating range 02/12/2020 Controlled Auto Ignition 4
  • 5. Methods to achieve CAI • EGR(Exhaust gas recirculation)(Hot and Cold) and preheating • Exhaust gas trapping • Control of valve timing and lift for exhaust gas trapping or Early Inlet Valve open • Controlling Air fuel ratio • Varying engine speed • Increasing compression ratio • Controlling coolant temperature • Fuel additives • Controlling injection timing(In case of GDI) 02/12/2020 Controlled Auto Ignition 5
  • 6. A. EGR (Exhaust gas recirculation) 1. Hot EGR 2. Cold EGR With hot EGR the inlet gas can be heated to get auto ignition known as preheating and also the dilution takes place reducing the amount of oxygen per intake. Also the burnt gas increases the heat capacity increasing the combustion duration. Exhaust gas can also participate chemically in combustion increasing the combustion duration. start of ignition is advanced due to increased temperature. Also by decreasing amount of oxygen the peak temperature is reduced reducing 𝑁𝑂𝑥 Varying EGR content affects the combustion most 02/12/2020 Controlled Auto Ignition 6 Methods to achieve CAI
  • 7. 02/12/2020 Controlled Auto Ignition 7 A. EGR (Exhaust gas recirculation) Effect of cold EGR Combustionduration Effect of Hot EGR
  • 8. B. Exhaust Gas Trapping • Exhaust gas trapping is done by varying the valve opening and closing duration and timing. The benefit of Exhaust gas trapping it to create dilution of the air and fuel inside the cylinder chamber and also to increase the combustion chamber temperature helping in auto ignition. • But at low speeds the exhaust temperature is not that high hence it won’t help in auto ignition. • Also due to exhaust gas trapping there is the distribution of temperature as shown below experimentally which is good for getting auto ignited • RGF- Residual gas fraction 02/12/2020 Controlled Auto Ignition 8
  • 9. C. Variable valve timing and lift • In case of Early inlet valve opening some of the burnt gases are pushed into the inlet manifold heating the inlet air and diluting the inlet air. This is known as back flow strategy 02/12/2020 Controlled Auto Ignition 9
  • 10. C. Variable valve timing and lift • Early inlet valve opening is providing better auto ignition • In case of exhaust gas trapping the Negative valve overlap must happen. • Also variable valve actuation can be used to de activate different cylinder at low load demand 02/12/2020 Controlled Auto Ignition 10
  • 11. D. Controlling AF ratio • CAI engine runs leaner but if it is too lean the partial burning may take place or if it is too rich the misfiring may take place due to low temperature(lambda=> airf/fuel). Also running too lean leads to less peak temperature and hence less 𝑁𝑂𝑥. But during misfiring and partial burning lot of HC and CO is emitted. Also rich mixture increases 𝑁𝑂𝑥. 02/12/2020 Controlled Auto Ignition 11
  • 12. 02/12/2020 Controlled Auto Ignition 12 D. Controlling AF ratio
  • 13. 02/12/2020 Controlled Auto Ignition 13 D. Controlling AF ratio
  • 14. • By engine speed if it is too low the heat will be lost to walls(implies partial burning) and if the engine speed is high it will get less time to get it transferred to the walls(implies knock tendency) 02/12/2020 Controlled Auto Ignition 14 E. Varying engine speed
  • 15. • By increasing compression ratio if it is too less no auto ignition or partial burning if it is too high knocking takes place 02/12/2020 Controlled Auto Ignition 15 F. Varying Compression ratio
  • 16. • On reducing coolant temperature to 65°C, the upper limit can be extended up to 14% while with increasing the coolant temperature the lower limit can be extended up to 28% for a single-cylinder engine operating in CAI through the negative valve overlap approach. • Additive-like Dimethyl-ether(DME) have low octane number and also water can be used as additive to reduce the combustion rate. Also affects the ignition timing and reduces NOx. 02/12/2020 Controlled Auto Ignition 16 G. Varying Coolant temperature H. Additives I. Controlling of injection timing • In case of GDI(Gasoline Direct Injection) the injection timing to control the start of ignition which is difficult during the port injection and throttle body injection in case of CAI. • ECU (Electronic control unit) manages the amount of fuel injected and timing of injection as per the condition of operation and feedback from the previous combustion.
  • 17. Further Innovation in CAI • Hybridization of concept between Spark ignition at low speed and cold starting condition and CAI at other speeds • Other concept of hybridization is use of spark plug to just create the pressure by combusting small stratified charges near spark plug and rest all combusts by auto ignition. • The innovation is used in MAZDA Skyactiv X which is only the commercial 4 stroke engine in the market. 02/12/2020 Controlled Auto Ignition 17
  • 19. References [1]. Chen, Tao, et al. "Methods to achieve HCCI/CAI combustion at idle operation in a 4VVAS gasoline engine." Applied energy 116 (2014): 41-51. [2]. Milovanovic, Nebojsa, and Rui Chen. A review of experimental and simulation studies on controlled auto-ignition combustion. No. 2001-01-1890. SAE Technical Paper, 2001. [3]. Zhao, H., Z. Peng, and N. Ladommatos. "Understanding of controlled autoignition combustion in a four-stroke gasoline engine." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 215.12 (2001): 1297-1310. [4]. Allen, Jeff, and Don Law. Variable valve actuated controlled auto-ignition: speed load maps and strategic regimes of operation. No. 2002-01-0422. SAE Technical Paper, 2002. [5]. Kulzer, Andre, et al. "Controlled auto-ignition." AutoTechnology 7.4 (2007): 56-59. [6]. Zhao, Hua. HCCI and CAI engines for the automotive industry. Elsevier, 2007. [7]. Saurabh et al. “Seminar on HCCI and CAI engine” 2016-2017. 02/12/2020 Controlled Auto Ignition 19