Contents 1 ▣ Engine General - Diesel Engine Basic - A-2.5TCI Common Rail Direct Injection - Sigma - 3.4 Diesel Engine System 2 Diesel Engine Diesel Fuel Property 3 ■ Comparison Property / Fuel Diesel Gasoline Heat Value(kcal/kg) 12,840 11,300 Specific Gravity 0.75 Flash Point(℃) 60~85℃ -40℃(below) Ignition Point (℃) 350 (℃) 550 (℃) Viscosity(Sec.) Diesel > Gasoline Ignitibility(Knock) Cetane No. Fuel Consumption(g/ps) 150~240 230~300 ※ Others : Sulfur content, Carbon number, Oxidation & water Cetane Number 4 ■ Cetane No. vs Carbon monoxide Diesel Fuel Property 5 ■ Diesel fuel’s injection condition 1. Atomization : - The atomized mist pressurized by high pressure (nearly 100 ~ 1500bar) pump is injected through small nozzle hole at the end of injector.
This fuel mist has collisions with compressed air in the combustion chamber with high speed. The size of this injected mist needs to be atomized as smaller as possible so that its total surface contacted with air becomes larger. In this reason, the atomization is the most important factor for ignition and perfect combustion. Penetration : - Even though the injected fuel is in good condition in atomization, it is difficult to meet fresh air in compressed combustion chamber if this mist hasn’t enough power to go fast and quite a way off.
Generally Atomization and Penetration can not be met together in normal situation since atomized mist has much more resistor for air. Diesel Fuel Property 6 3. Distribution : - It is important for Injected fuel to have good distribution in combustion chamber for perfect combustion. Pre chamber combustion and swirl type was adapted to make gas pulsation be increased in the process of the distribution in combustion chamber.
▽ Direct Injection ▽ Pre-combustion chamber ▽Swirl Chamber Nozzle Glow Plug Nozzle Swirl Chamber Nozzle Piston Glow Plug Piston Chamber Piston M.Chamber Diesel Fuel Property 7 ■ Swirl energy Comparison Distribution difference 8 ■ Distribution difference by injector install type Soot Formation 9 ■ Soot and Nox formation theory Diesel Combustion Process 10 ■ Internal Pressure Diagram in Combustion T A: beginning of fuel delivery from pump A-C : Injection Lag B: beginning of fuel injection from nozzle C-D : Explosive Combustion C: beginning of combustion D-E : Extensive Combustion T: point of TDC E-F : After Combustion D: fuel injection end E: after injection F: combustion end F C E B A D After injection -100 ˚ 0˚ 100 ˚ TDC Diesel System Advantage and Disadvantage 11 ■ Ignition Lag : - Diesel combustion process is a little different by several reasons compared to Gasoline’s. The ignition in diesel happens in several points by heated air when atomized fuel mist is injected. In that reason, the fire deflection is affected by several things such as combustion pressure, fuel temperature, water coolant temperature, rpm and so on. The ignition lag in internal pressure diagram shows the connection among the mentioned items before.
Generally in diesel engine this lag becomes about 3~ 7ms, but it’s different by conditions. If Ignition lag becomes longer, the detonation, diesel knock easily happens. The way to shorten this lag is : - Using High compression rate - High Centan No. fuel - Retard the injection time - Using swirl to increase deflection speed - Turbocharger with intercooler - Small nozzle size - appropriate working temperature in fuel, water coolant and air intake Diesel development 12 ■ Dynamic of diesel development Diesel System Advantage and Disadvantage 13 ■ System Comparison Items / Fuel Diesel Gasoline Mixture(A/F) Irregular Regular Ignition Heat of Compression Electrical Spark Compression ratio 16~23:1(only air) 8~11:1(A:F) Fuel Efficiency(%) 35~40 25~35 Explosion Pressure 120~160kg/㎠ 50~70kg/㎠ Max.
rpm 4500 7500 Load Control Fuel A/F Mixture Exhaust Temp. Low High Diesel System Advantage and Disadvantage 14 ■ Advantage - Using cheaper fuel (Generally) - Using the heat of compression to ignite ⇒ It makes system simple. - High efficiency at light loads and idle speeds - High compression ratio⇒ good fuel consumption - Fuel efficiency is higher (by 15%) - Components’ durability ■ Disadvantage - Precise in injection system and durability⇒ these make them more expensive to build - Output torque range is shorter than gasoline’s - Harmful emission gas ⇒ soot-laden(particles), sulfur content, - Detonation is easy to occur Stroke Cycle Comparison 15 ■ Diesel : Compression ignition Injector Air Compressed Only Air ex.gas Cylinder Piston Intake Compression Power Exhaust ■ Gasoline : Spark Ignition Spark Plug Compressed Ignite Air/Fuel ex.gas Piston Air/Fuel Intake Compression Power Exhaust Group discussion 16 ■ Subject : Common Rail System 1. Discuss by party what the common rail system is - Concept, main components, the difference verse IDI system, - Your country’s situation in commercial diesel vehicle - Advantage or disadvantage etc.
Present each party’s output - Use 5 minutes for presentation Common Rail Direct Injection (CRDI) 17 ■ CRDI System Overview - Over the years, a wide variety of different requirements in diesel engine, such as severe exhaust gas regulation, high power output at any range, and easy installation at any vehicle types from small sized passenger cars to heavy truck, have led to the using CRDI system which is met all of requirements. - Compared to conventional cam-driven mechanical injection system, the CRDI fuel injection system provides for considerably higher flexibility in the adaptation of the injection system to the engine. - The main advantage to a common-rail system is that there is no relationship between engine speed and injector pressure. In traditional fuel-injection systems, you can get only limited pressure at low engine speeds.
In addition, high-speed engines offer reduced time for fuel/air mixture formation, so injection pressure is key to move the combustion along at a fast pace. In addition, it can generate almost 1,000 bars of pressure already at an engine speed of only 1,500 rpm, which was previously impossible. Common Rail Direct Injection (CRDI) 18 -The diesel common-rail systems embody the same concept as gasoline-engine rails, which feature an accumulator connected with tubes to the injectors. The basic difference between them is the injector pressure.
In a common-rail diesel, it reaches 1,300 to 1,600 bars of pressure. In a gasoline rail system, the pressures are much less than 3 or 4 bars ■ Main Features - Extensive area of application - High injection pressures of up to approx. 1400bar - Variable start of injection - Possibility of pilot injection, main injection and post injection - Matching of injection pressure to the operating mode New technology - VGT 19 ■ VGT (Variable Geometry Turbo) VGT Vacuum Actuator Nozzle Vane Unison Ring A-2.5 TCI Mechanical system A-2.5 TCI CRDI Eng.5 TCI (CDRI) – High Speed Direct Injection 22 ■ Increasing specific power and fuel consumption - DOHC 4 valve with swing roller arm - Turbocharger with intercooler - State-of-the-art Electronic Diesel Control(EDC) by Bosch with Common Rail - Electronically controlled high precise injectors installed in the center of the combustion chamber - High injection pressure up to approx. 1,350 bar ■ Low emission and NVH decreased - Pilot injection prior to main injection - Balance shafts - EGR system with oxidation catalytic converter - Cam carrier and ladder frame type bed plate A-2.5 TCI (CDRI) – High Speed Direct Injection 23 ■ A-2.5 TCI Items A-Eng.
EMS Bosch Available Vehicle Sorento Displacement(cc) 2,497 High Pressure Timing Chain Pump Drive Pull-in currency Injector Control (20A) by EMS Pilot Injection Fuel Injection Main Injection Max. Fuel Pressure 1350bar Fuel Pressure Control Inlet Control Glow plug Heating Device Water coolant heater Fuel Heater Valve Clearance HLA Comparison with J Ⅲ 2.9ℓ C/R Items J Ⅲ-Eng EMS Delphi Available Vehicle Carnival Displacement(cc) 2,902 High Pressure Timing belt Pump Drive Pull-in currency Injector Control (10A) by EMS Pre Injection Fuel Injection Main Injection Max. Fuel Pressure 1400bar Fuel Pressure Control Inlet Control Air Heater Heating Device Fuel Heater Water Coolant Heater Valve Clearance HLA Comparison with HTI D-Eng. Items D-Eng EMS Bosch Available Vehicle Carens Displacement(cc) 2.0ℓ High Pressure Camshaft Driven Gear Pump Drive Pull-in currency Injector Control (20A) by EMS Pre Injection Fuel Injection Main Injection Max.
Fuel Pressure 1350bar Fuel Pressure Control Outlet Control Glow plug Heating Device Fuel Heater Water Coolant Heater Valve Clearance HLA A-2.5 TCI (CDRI) – Engine Performance Curve 26 TEST MODE : JIS 82 NET ENGINE : D4CB(A2.5 TCI) 33/2OOO rpm 145/4OOO rpm ※ Sorento’s highest torque produces in 2000 rpm. Considering the fuel consumption curve with best torque it’s recommended to drive in this rpm range.5 TCI (CDRI) – Wastegate 27 ■ Wastegate A bypass valve (wasrte / regulator) allows the turbo system to develop peak charge-air pressure for maximum engine boost response while eliminating the chance of excessive manifold pressure (overboost) at high speed. The wastegate is precisely calibrated and opens to direct some exhaust gas flow around the turbine wheel. This limit shaft speed which in turn control boost pressure.5 TCI (CDRI) – Boost Pressure 28 ■ Boost pressure at intercooler outlet Check point A-2.5 TCI (CDRI) – Intercooling 29 ■ Intercooling Intercooling is a process whereby an air cooler, called the intercooler, reduces the temperature of the compressed air intake, making it denser with a higher concentration of oxygen per cubic air volume.
Coupled with turbocharging, an even higher level of combustion is achieved, thereby releasing an additional 15% engine power. The Sorento uses a front ahead type intercooler.5 TCI (CDRI) – Intercooler Out Temperature 30 ■ Intercooler outlet temperature Check point Te let ut p. O ng rp m in E e A-2.5 TCI(CRDI) - Common Rail System Layout 31 ■ System Layout – CP3 ⑦ ⑨ ⑧ ⑩ ⑪ ⑤ D ⑫ ④ ⑭ ⑬ ⑥ A ③ E B ⑮ ① C N F L ② K J M O G H I A-2.5 TCI(CRDI) - Common Rail System Layout 32 ■ Components Descriptions - ① : Fuel Tank - ⑬ : CMP sensor - J : Air-con switch - ② : Pre-filter - ⑭ : Air flow sensor - K : Diagnostic connect - ③ : Fuel filter - ⑮ : WTS - L : Can Bus - ④ : Low pressure pump - A : Glow plug relay - M : Cluster - ⑤ : High pressure pump - B : ECM - N : Vacuum Modulator - ⑥ : Pressure control valve - C : CKP sensor for EGR - ⑦ : Common rail - D : Rail pressure sensor - O : Battery - ⑧ : Pressure limiter valve - E : Turbocharger - ⑨ : Fuel return line - F : Wastegate - ⑩ : High pressure line - G : Accelerator pedal sensor - ⑪ : Low pressure line - H : Brake switch - ⑫ : Injector - I : Clutch switch A-2.5 TCI(CRDI) - Cleanliness 33 ■ Cleanliness The high pressure required by the common rail injection system makes it necessary to have much smaller holes and much tighter adjustments than those found in conventional injection systems. It is therefore absolutely essential to ensure impeccable cleanliness whenever work is being done on a common rail type injection system.
hair Injector Hole Sorento – Engine Room 34 Air Flow Sensor EGR Valve High Pressure Pump Intercooler Condenser Fan A 2. View 35 Alternator Timing Chain “C” High Pressure Pump Auto Tensioner Viscous coupling clutch A 2.5 TCI – Viscous coulping 36 ■ Viscous coulping When you start the engine, the fluid is cold and watery in consistency, so although the fan turns there isn't a very strong bond between the fan and the engine. This allows the fan to be stopped with little effort and the engine to reach optimum temperature. When your engine reaches this temperature the fluid in the coupling is hotter and has a thicker consistency.
The thicker consistency causes the bond between the engine and the fan speed to improve causing the fan to run faster at higher speeds.5 TCI – Side View 37 One Driving Belt Glow plug CKP Sensor Turbocharger Oil Cooler Air-Con.