TỰ ĐỘNG HÓA HỆ THỐNG LẠNH

Marine Diesel Engines • Theory: 90 periods (in class) Structure: 50 periods Theory of working processes: 40 period • Practice : 22 periods • Simulator: 10 periods • Subject thesis: 13 periods • Total: 135 periods 14/05/16 Editor: Nguyen Trung Cuo CHAPTER 1: Operational Principle of Diesel engines • • • • • • 1.1 Introduction and development history of diesel engine 1.2 The operational principles of four stroke engine 1.3 The operational principles of two stroke engine 1.4 Classification of internal combustion engine 1.5 The symbol of diesel engine of some firms 1.6 Nomenclature of internal engine 14/05/16 Editor: Nguyen Trung Cuo 1.1 History of engine development • In the 19th century and early 20th century, steam engines • were strongly developed in Europe as propulsion plants for trains, pumps, and steam ships In these engines, potential energy of the steam is converted into mechanical work of a piston that moves in a cylinder 14/05/16 Editor: Nguyen Trung Cuo 1.1 History of engine development • The steam is provided to the cylinder by a boiler The steam engines can be called as the external-combustion engines • In 1778, the first internal combustion engine was designed by a German engineer, Mr Otto This engine was called spark-ignition engine 14/05/16 Editor: Nguyen Trung Cuo 1.1 History of engine development • In 1892, a German engineer, Rudolf Diesel designed a new type of high compression engine that was constructed in 1897 • This engine was operated on kerosene and hereafter called a diesel engine • To memory its designer, the compression-ignition engines were called Diesel engines 14/05/16 Editor: Nguyen Trung Cuo 1.1 History of engine development • Application of the internal combustion engines: • The internal combustion engines, especially diesel engines, have a wide use in stationary, marine and transport applications compared to other heat engines • Due to their advantages of:  compact design, small weight, ability of high power creation, the ability of operating with cheap fuel oils (heavy oil products) 14/05/16 Editor: Nguyen Trung Cuo 1.1 History of engine development The tendency of engine development • Nowadays, the diesel engines have been being more and more used for marine applications, especially as main engines on board ships Type of engines Percentage % Low speed diesel engines 75.5% Medium, High speed engines 23.0 Steam, Gas Turbines 1.5% Market share Maker MAN-B&W SULZER Mitsubishi Others Share 54% 9% 3% 14/05/16 34% Editor: Nguyen Trung Cuo 1.1 History of engine development The tendency of engine development • • • • • • • Increasing the power rate Decreasing the fuel consumption  Moderating propeller revolution  Settling the counter-measures for the degraded fuel oil Increasing the reliability and durability and Obtaining the easy handling and maintenance Reduction of environment pollution 14/05/16 Editor: Nguyen Trung Cuo 1.2 The operational principle of four stroke engine • 1) 2) • By cycle performance, the internal combustion engine is classified into: Two-stroke engine Four-stroke cycle engines  The four-stroke cycle is completed in four strokes of the piston, or two revolutions of the crankshaft 14/05/16 Editor: Nguyen Trung Cuo 1.2 The operational principle of four stroke engine • To simplify this operation, we can suppose that the principle operation of a 4-stroke diesel engines consists of basic processes as follows: – Suction stroke – Compression stroke – Firing (combustion) and expansion stroke and, – Exhaustion stroke 14/05/16 Editor: Nguyen Trung Cuo 10 1.3 The operational principle of two stroke engine • Opposed piston diesel engine This cycle is used in the Doxford engine, which is no longer manufactured although many are still in operation 14/05/16 Editor: Nguyen Trung Cuo 29 1.3 The operational principle of two stroke engine • • • Graphic indication working The piston moves downwards from TDC to BDC When the crank is about 40600 before BDC (point b), the piston uncovers the exhaust ports, and blow down the exhaust gas to a manifold The speed of opening the exhaust ports is very rapid and the pressure of the gases in side cylinder falls quickly Editor: Nguyen Trung Cuo (bd) 14/05/16 30 1.3 The operational principle of two stroke engine • • • Graphic indication working By the time the pressure of the gases has fallen slightly below the scavenging air pressure, the piston uncovers the scavenging ports (d); The scavenging air blows in to the cylinder, forcing out the remaining gases The scavenging ports begins to be uncovered by the piston movement when the crankshaft is about 35 – 550 before BDC 14/05/16 Editor: Nguyen Trung Cuo 31 1.3 The operational principle of two stroke engine • Timing diagram of two stroke diesel engine •The scavenging ports begins to be uncovered by the piston movement when the crankshaft is about 35 – 550 before BDC 14/05/16 Editor: Nguyen Trung Cuo 32 Definition 14/05/16 Editor: Nguyen Trung Cuo 33 Comparison of two-stroke and four-stroke cycles Four stroke engine Two stroke engine • The • The four stroke cycle engine, with one working or power stroke every two revolution 14/05/16 two-stroke cycle engine, with one working or power stroke every revolution • theoretically, develop twice the power of a fourstroke engine of the same swept volume • Inefficient scavenging however and other losses, reduce the power advantage to about 1.8 Editor: Nguyen Trung Cuo 34 Comparison of two-stroke and four-stroke cycles Four stroke engine • The four stroke engine require the intake, exhaust valves and complicated valve operating mechanism 14/05/16 Two stroke engine • The two stroke loop scavenging engine does not require the intake, exhaust valves and complicated valve operating mechanism Editor: Nguyen Trung Cuo 35 Comparison of two-stroke and four-stroke cycles Four stroke engine • The four stroke engine require the intake, exhaust valves and complicated valve operating mechanism 14/05/16 Two stroke engine • The two-stroke cycle Uniflow scavenging engine, require the exhaust valves and valve operating mechanism only Editor: Nguyen Trung Cuo 36 Comparison of two-stroke and four-stroke cycles Four stroke engine • The four stroke engine require the intake, exhaust valves and complicated valve operating mechanism 14/05/16 Two stroke engine • Ports are arranged in the cylinder liner for air inlet and a valve in the cylinder head enables the release of exhaust gases.( two stroke cycle Uniflow scavenging engine), or for air inlet and exhaust gas outlet (two stroke cycle lop scavenging engine) Editor: Nguyen Trung Cuo 37 1.4 Classification of internal combustion engines 1.4.1 By cycle performance: • 4-stroke engines, 2-stroke engines 1.4.2 By kind of fuel used: • Light liquid fuel (Petrol, kerosene) • Gaseous fuel • Heavy liquid fuel:(FO, DO, HFO) • Mixed fuel (gas and liquid fuel) and • Multi-fuel (petrol, kerosene, DO, FO, etc.) 1.4.3 By method of mixture formation • Internal mixture formation • External mixture formation 14/05/16 Editor: Nguyen Trung Cuo 38 1.4 Classification of internal combustion engines 1.4.4 By type of combustion chambers • Pre-combustion chamber • Direct injection chamber • Vortex chamber (Swirl chamber) 1.4.5 By method of igniting the working mixture • Spark-ignition engine • Compression-ignition engine • Gaso-diesel engine 1.4.6 By working process • Constant-volume combustion • Constant-pressure combustion • Combined combustion (diesel engine) 14/05/16 Editor: Nguyen Trung Cuo 39 1.4 Classification of internal combustion engines 1.4.7 By the method of charging air • Non-supercharged engine • Supercharge engine 1.4.8 By the engine construction a/ By the number of cylinders •           single-cylinder •           multi-cylinder b/ By the arrangement of cylinders •           Vertical in-line •           Horizontal in-line •           V-shape •           Star-shape • Opposed piston 14/05/16 Editor: Nguyen Trung Cuo 40 1.4 Classification of internal combustion engines 1.4.9 By the reversibility of the crankshaft • Irreversible (Non-reversible) engines • Reversible engines 1.4.10 By cylinder action • single acting • double acting 1.4.11 By mean engine speed •   Low speed engine : n < 250 rpm •   Medium speed engine: n = 251÷ 750rpm •   High speed engine: n >7 50rpm 14/05/16 Editor: Nguyen Trung Cuo 41 1.4 Classification of internal combustion engines 1.4.12 By applications of the engine • Stationary engines: power plants, pumping units etc • Marine engines: main engines, generators etc • Locomotives • Vehicle engines • Airplane engines and • Engines for other machinery used in agriculture, construction, • road building etc 14/05/16 Editor: Nguyen Trung Cuo 42 Questions: Please explain the operational principle of a 4-stroke diesel engine Please explain the operational principle of a 2-stroke diesel engine 14/05/16 Editor: Nguyen Trung Cuo 43