FOREWORD

      Diesel engine have been a major source of power in the industrial field for many years. This trend has continued and has been ever more pronounced in recent years with with the increased use of tractors,marine, and industrial power units. The diesel engine has proven itself to be a dependable source of economical power wherever engines high in horsepower and reliability are required.
      This book compares and points out the advantages and dis-advantage of gasoline and diesel engines and two-stroke-cycle and four-stroke-cycle engines; and it discusses practically all types and designs of diesel engines use today. An attempt has been made to clearly present and explain the theory, operation, and maintenance all type of diesel engines, including stationary power units and truck, bus tractor, and marine engines.
       The question-power-method, along with many pertinent and informative illustrations, is used in presenting all the important aspects of theorectical and practical operation as well as maintenance of Diesel engines.
       The Diesel Engine Manual will be valuable to students, mechanics, operators of Diesel-powered vehicles and stationary engines, and all others who are interested in or require a knowledge of Diesel Engines. The book will be especially valuable to the individual who is already working of Diesel engines and desires to increase his knowledge or understanding of Diesel engines in order to become more proficient in their maintenance or operation.



                       FUNDAMENTAL PRINCIPLES


what is a Diesel engine?
     - A Diesel engine is an engine which uses a low-grade oil for fuel and ignites this fuel by the heat of air compression.

Where did the Diesel engine get its name?
     - From Dr. Rudolf Diesel, an inventor, who obtained his patents on the principle of the Diesel engine in 1983.

Where can a Diesel engine be used?
     - Almost any place where power is needed-whether on land or water.

How long has the Diesel engine been in practical use?
     - since about 1900.

What are the main differences between a Diesel engine and gasoline engine?
     - The Diesel engine may use a low-grade fuel oil which is ignited in the cylinder by the heat of air compression. The gasoline engine requires high-grade gasoline for fuel which is ignited by an electric spark after the gasoline has been mixed with air in a carburetor, injected into the cylinder, and the mixture compressed.

How does a carburetor in a gasoline engine vaporize the fuel?
      - By blowing a stream of air over through the fuel, sending it out in the form of a mist or gas. This makes it easier to ignite than if it where in the liquid state. Also it mixes air with the fuel, making it into a high explosive. It is the explosion of the mixture in the cylinder which drives the piston and gives it power.

What is true Diesel engine?
       - One which ignites and burns the market grade of diesel fuel oil without preheating either the oil or any part of the cylinder to get rquired heat. It use neaither outside igniting nor mixing devices.

What is a semi-Diesel engine?
       - One which works in part on the Diesel principle that is, using some of the features of the Diesel Engine.

What is a hot-air engine?
       - One in which the expansion of heated air in used as the driving force. Air at high pressure is admitted to cylinder wherein on expansion it moves the piston. The air is then exhausted to the atmosphere or recompressed and reused. Engines of this type where the bulky for the mount of power which they gave and where used mainly where a small power output was required and plenty of cold water existed for cooling.

How does the efficiency of a Diesel engine compare with that of other types of heat engines?
       - The Diesel engine is the most efficient type of engine known from a thermal (heat) point of view and is the true internal-combustion engine. It depends solely upon its own heat, generated in the cylinders, for igniting and burning the fuel.

How is heat for ignition obtained in the Diesel engine cylinders?
      - By compressing the air in the cylinders until it has reached a temperature high enough to ignite the injected fuel.

What is the purpose of the carburetor on a gasoline engine?
      - Its purpose is to mix gasoline with air for ignition. Carburetors are made in different forms with various control devices to control the quantity of air and the quantity of gasoline mixed. The mixture is compressed in the upper part of the cylinder by the upward movement of the piston. Then a spark is sent into the cylinder to power stroke for that cylinder (Fig. 1).
        In the Diesel engine, a carburetor is not needed to mix air with the fuel oil and a spark is not needed to ignite it. Air, alone, is compressed in the cylinder and the fuel oil is sprayed into the compressed air. The heat of the compressed air ignite the fuel oil and pushes the piston downward. Therefore all the energy is produced directly inside the cylinder without outside sources.

How does compressed air heat the cylinders?
      - When a volume of air is forced into a small space, it its heated in proportion to the amount to which it has been compressed.

What is ignition?
      - The act of setting on fire. In a gasoline engine, the electric spark sets the gasoline mixture on fire (Fig. 2). In the Diesel engine, the heat of compression in the cylinders sets the fuel oil on fire (Fig. 2). In both instances, the fuel is ''ignited.''


                            OPERATING PRINCIPLES

 
Upon what basic principle does the Diesel engine operate?

      A charge of fuel oil is injected into heated air in the working cylinder. The heat ignites the oil, form gas, raises the temperature, expands, and moves the piston.

What creates the heat in the cylinder?

      Air is compressed required until it attains a temperature high enough to ignite the fuel oil.

What air pressure is required to produce the required temperatures?

      From 350 to 500 pounds per square inch.

How does the principle of Diesel engine operation differ from that of the gasoline engine?

      It differs in that, in the gasoline engine, a charge of gasoline and air is mixed in a carburetor, injected into the cylinder, compressed in the cylinder and then ignited by an electric spark: while in the Diesel engine, a charge of air alone is compressed in the cylinder, fuel oil is injected and ignited by heat of the compressed air.

What are the four strokes in the four-stroke-cycle Diesel engine?

      In the four-stroke-cycle Diesel engine (Fig. 1), four strokes of the piston are required to complete one cycle or series of events which must take places, in regular order, to operate the engine. This type of engine is commonly called the four-cycle engine. The four stroke are us follows:
      1. First stroke draws air into the cylinder.
      2. Second stroke compresses the air.
      3. Third stroke is produced by the burning gases. It is the power stroke.
      4. Fourth stroke expels the burned gases.

List the series of events in the four-stroke-cycle Diesel engine.
      The series of events taking place in a cylinder of a four-stroke-cycle engine, and making up one complete cycle, are shown in Fig. 1 as follows:
      1. First, the air-inlet valve opens, permitting air to be drawn into the cylinder by downward stroke of the piston.
      2. Second, the valve is closed and the piston starts upward, compressing the air for producing the heat needed to ignite the fuel oil.
      3. Third, the fuel valve opens and the fuel oil is injected into the hot air where it ignites.
      4. fourth, the burning fuel forms gases which create pressure and send the piston downward; this is the power stroke of the engine.
      5. Fifth, when the piston has completed its power stroke, the exhaust valve opens and permits the burned gases to escape.
      6. Sixth, the piston returning upward forces out the remaining gases in the cylinder. The exhaust valve closes and cycle repeats.

What are the two stroke in a two-stroke-cycle Diesel engine?

      In the two-stroke-cycle Diesel engine, two stroke of the piston are required to complete one cycle or series of events which must take place, in regular order, to operate the engine. This type of engine is commonly called the two-cycle engine. The stroke are as follows:
      1. One stroke compresses air in the cylinder to ignite the fuel oil.
      2. The other stroke is produced by the burning gases. It is the power stroke.

List the series of events in the two-stroke-cycle Diesel engine.
      The series of events taking place in a cylinder having charging and scavenging-air valves in the cylinder head and the exhaust port at the side, is shown in Fig. 2 as follow:

      1. Air, under slight pressure, is blown into and fills the cylinder through the open valves in the head.
      2. The piston is starting upward to compress the air for producing heat to ignite the fuel.
      3. The air is fully compressed and very hot.
      4. The fuel valve opens and fuel oil is injected into the hot air where ignites.
      5. The burning fuel forms gases which create a pressure and send the piston downward; this is the power stroke of the engine. When the piston is near the end of its stroke, it unconvers an opening, or port, in the cylinder through which the burned gases escape.
      6. The scavenging and charging-air valve in the head then open and air under pressure forces out whatever remaining gases may be in cylinder, leaving clean air for the next compression.