The Non-premixed Combustion & Diesel CI Engines P M V Subbarao Professor Mechanical Engineering Department I I T Delhi Energy Efficient & Dangerous Reactions in Too Lean & Too Rich Zones…..

Diesel Engines : Market Penetration Diesel driving fuel economy ~ 30% better than SI 5% from fuel energy/volume 15% from eliminating throttle loss 10% from thermodynamics 2nd law losses (friction and heat transfer) Higher compression ratio Higher specific heat ratio Dominant world wide heavy duty applications Dominant military applications Created “World Diesel Economy”

1980s : Diesel Engine Menace What Menace? NOx Respiratory problems. Ground ozone and PM formation. Acid rain. Visibility and haze. Nutrient pollution. Soot PM2.5 -- PM10 contributors. Chronic respiratory issues. Change in blood chemistry. Increased coronary blockade. Interferes with protein synthesis Soot-NOx Nexus-”Diesel Dilemma” is the looming evil at the tail pipe of a dieselized global economy.

History of Indian Emission Standards Reference Date Region India 2000 Euro 1 2000 Nationwide Bharat Stage II Euro 2 2001 NCR*, Mumbai, Kolkata, Chennai 2003.04 NCR*, 10 Cities† 2005.04 Bharat Stage III Euro 3 2010.04 Bharat Stage IV Euro 4 * National Capital Region (Delhi) † Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and Agra

Emission Standards for Diesel Heavy Duty Engines Year Reference CO (g/kW-hr) HC Nox PM 1992 - 17.3-32.6 2.7-3.7 1996 11.20 2.40 14.4 2000 Euro I 4.5 1.1 8.0 0.36 2005† Euro II 4.0 7.0 0.15 2010† Euro III 2.1 0.66 5.0 0.10 2010‡ Euro IV 1.5 0.46 3.5 0.02 † earlier introduction in selected regions, Table 1 ‡ only in selected regions, Table 1

Need to Study Diffusion Combustion In detail Strict emission regulations Efficient utilization of energy resources The conventional diffusion combustion can not meet upcoming stringent emission norms (Higher Smoke and NOx emissions ) Banning of Diesel engines across various Cities world wide regardless of their high efficiency and power out put (e.g. Delhi, Chandigarh) Emerging topic worldwide to keep the High efficient diesel fuelled vehicles rolling on the roads. Demands thorough understanding of Turbulent Non-premised Flames.

Diesel Ignition & Premixed Burning Fuel rich pre-premixed burning – Release of energy and release of Chemiluminescence emissions.

Temporal Evolution of Spatial Distribution of Equivalence Ratio rcylinder

Computations on Onset of Premixed Combustion Fuel Equivalence Ratio

Transition into Diffusion Burning

Diffusion Burning Flame Oxidation of incomplete products of the rich premixed combustion. Fuel vapor at the ‘jet’/ air interface Local Extinction

Dangerous Emissions in CI Engine

Dependence of flame height on Injection Speed

Final remarks : Turbulent Diffusion Combustion Structure of Turbulent Diffusive Flame – Three-zone structure: mixing – reaction – mixing – Reaction zone is highly wrinkled – Reaction zone is rather thin in physical space – Mixing is governed by turbulence eddy motion Turbulence flame interaction: laminar flamelet regime – Large eddies transport the fuel and air to the flame (slow) – Large eddies determine the overall mixing rate – Large eddies determine the flame height – Small eddies are responsible for the mixing on molecular scale Small eddies can quench the flame

A Model for Eco-inimical Combustion

Diesel Engine Menace Why Menace? Stratified charge and φ-T in-cylinder distribution. Stoichiometric zones: High AFT-NOx in post flame. Rich zone: High PAH- Soot. Lean zone: Poor combustion- High CO and UBHC

Development of Injection Pressure & Injection System in CI Engines

Actual Vs Eco-friendly Equivalence Ratio for CI Combustion

Fluid dynamics of High Pressure Diesel Injection

Types of CI Engine Injection Systems Air assisted Fuel-Injection Systems. Unit Injector System (UIS) – Single-Cylinder CI Engine. Unit Pump System (UPS) – Multi-cylinder CI Engine. Common Rail Injection System (CRS) – Multi-cylinder CI Engine.

First Generation Common Rail Diesel Injection System The Common Rail Diesel Injection System delivers a more controlled quantity of atomized fuel. This leads to better fuel economy; a reduction in exhaust emissions; and a significant decrease in engine noise during operation.

History of CRDI The common rail system prototype was developed in the 1960's by Robert Huber of Switzerland. The technology was further  developed by Dr.Marco Ganser at the swiss Federal Institute of Technology in Zurich. The first successful usage in production vehicle began in Japan in the mid-1990's by Dr.Shohei Itoh & Masahina Miyaki of the Denso Corporation.

Present Generation (Electronically Controlled) CRDI

Common rail diesel injection system In the Common Rail system, an accumulator, or rail, is used to maintain a common reservoir of fuel under a consistent controlled pressure that is isolated from the fuel injection locations. A high-pressure pump increases the fuel pressure in the accumulator up to 1,600 bar . The pressure is set by the engine control unit and is independent of the engine speed and quantity of fuel being injected into any of the cylinders. The fuel is then transferred through rigid pipes to the fuel injectors, which inject the correct amount of fuel into the combustion chambers.

Modern Injectors for CRDI The injectors used in Common Rail systems are triggered externally by an Electronic Diesel Control, (EDC) unit. EDC controls all the engine injection parameters including the pressure in the fuel rail and the timing and duration of injection. Some common rail injectors are controlled by a magnetic solenoid on the injector. In some injectors, hydraulic force from the pressure in the system is used to open and close the injector, but the available pressure is controlled by the solenoid triggered by the Electronic Diesel Control unit.

Next Generation Injectors for CRDI Some new injectors use Piezo crystal wafers to actuate the injectors. These crystals expand rapidly when connected to an electric field. In a Piezo inline injector, the actuator is built into the injector body very close to the jet needle and uses no mechanical parts to switch injector needles. The electronic diesel control unit precisely meters the amount of fuel injected, and improves atomization of the fuel by controlling the injector pulsations. This results in quieter, more fuel efficient engines; cleaner operation; and more power output.

Next Generation Diesel Injection Systems: The HEUI (Hydraulically Actuated Electronically Controlled Unit Injector) technology

Eco-friendly Equivalence Ratio for CI Combustion Low Pressure Injection CRDI Perfect CI Engine