Overview:
The text, “Gas and Oil Engines, Simply Explained,” written by Walter C. Runciman in 1905, offers a comprehensive guide to the workings of early internal combustion engines. It begins with a historical overview, tracing the evolution of the gas engine from the rudimentary gunpowder-powered machines of the 17th century to the more efficient, four-stroke Otto cycle engines of the early 20th century. The author emphasizes the importance of understanding the fundamental principles of gas behavior and combustion for achieving optimal engine performance.
The book then delves into the construction and function of engine components. Runciman explains the various types of ignition devices, including the hot tube, porcelain tube, and electric ignition, as well as different governing mechanisms like inertia governors and centrifugal governors. He elaborates on the importance of proper valve settings for engine efficiency, and provides a detailed guide to understanding and adjusting these settings. The text concludes with a discussion of oil engines, highlighting various vaporizer designs for converting oil into usable gas.
Key Findings:
- The Otto cycle: The four-stroke cycle, known as the Otto cycle, became the standard for most gas engines by the early 1900s. This cycle involves four strokes of the piston: suction, compression, power (expansion), and exhaust.
- Importance of Proper Ignition: The ignition device is crucial for successful engine operation. The text details different ignition methods, highlighting their strengths and weaknesses.
- Governing Mechanisms: Governors are essential for regulating engine speed and preventing overspeeding. Runciman describes various governor types, including centrifugal governors and inertia governors.
- Valve Settings and Engine Efficiency: Proper valve timing is paramount to optimal engine performance. The text details how to adjust valve settings for different engine types.
- Early Oil Engines: The book introduces the challenges and advancements in early oil engines, specifically focusing on different vaporizer designs for converting oil into gas.
Learning:
- The Four-Stroke Otto Cycle: The reader will understand the fundamental working principles of the Otto cycle gas engine, encompassing suction, compression, power, and exhaust strokes.
- Ignition Devices: The text explains the function of various ignition devices, including the hot tube, porcelain tube, and electric ignition, providing insight into their advantages and disadvantages.
- Governing Mechanisms: The reader will learn about the role of governors in regulating engine speed and how different types, like centrifugal and inertia governors, work.
- Valve Timing and Engine Performance: The text emphasizes the importance of proper valve timing for optimal engine efficiency and provides a practical guide to adjusting valve settings.
- Early Oil Engine Development: The reader will gain an understanding of the challenges associated with developing early oil engines and how vaporizer designs play a crucial role in their function.
Historical Context:
The text was written in 1905, a time when internal combustion engines were rapidly evolving. The book reflects the technological advancements made during the late 19th and early 20th centuries, showcasing the transition from rudimentary gas engines to more efficient and sophisticated designs. The author also describes the challenges and uncertainties faced by early users, such as inconsistent ignition and the need for frequent maintenance.
Facts:
- Gas alone is not explosive. It requires air to create a flammable mixture.
- The Otto cycle is a four-stroke cycle. This means it takes two full revolutions of the crankshaft to complete one cycle.
- The combustion chamber is usually about one-fourth the volume of the cylinder. This is where the fuel-air mixture is ignited.
- The exhaust valve must be kept cool. Overheating can lead to seizing and damage.
- Porcelain ignition tubes are more durable than iron tubes. But they require higher temperatures to function.
- A magneto ignition system does not require batteries. It uses a small generator to produce the spark.
- The air vessel in an oil engine pump helps maintain constant pressure. This ensures a steady flow of fuel.
- The first real gas engine used coal tar, spirit, or turpentine as fuel. It was developed by Robert Street in 1794.
- The principle of compression was applied to gas engines in 1838 by Barnett. This significantly improved efficiency.
- Lenoir’s engine, introduced in 1860, was very popular but not very efficient. It consumed a lot of gas.
- The Otto cycle is named after Nikolaus Otto. He was the first to implement Beau de Rochas’s principles for maximizing engine efficiency.
- Early engines often required a lot of maintenance. The text emphasizes the need for regular inspection and adjustment.
- Modern gas engines have significantly higher efficiency than early models. This is due to improved design and manufacturing.
- Cooling water is essential to prevent overheating. It circulates around the cylinder and exhaust valve.
- The cooling water passages should be designed to cool the hottest parts of the engine. This ensures optimal performance and prevents damage.
- The air and gas mixture needs to be homogeneous for efficient combustion. This ensures all fuel is burned.
- The cold portion of the bunsen flame should not touch the ignition tube. Only the hot portion should be directed at the tube.
- The size and shape of the cams determine the valve timing. This is crucial for engine efficiency.
- The exhaust cam is often fitted with a swelling to relieve compression when starting. This aids in starting the engine.
- Early oil engines relied on vaporizers to convert oil into gas. Different designs were developed to achieve this.
- Capel’s oil engine design was notable for its simplicity. It could be easily adapted from a gas engine.
Statistics:
- Coal gas is composed of five main gases: Hydrogen (50%), marsh gas (38%), carbon monoxide (4%), olefines (4%), and nitrogen (4%).
- A typical explosive mixture requires ten parts air to one part gas. This is important for safety and efficient combustion.
- Lenoir engines were initially claimed to be very economical. They were said to use 3.4 shillings per day, half the cost of a steam engine.
- The actual fuel consumption of Lenoir engines was significantly higher than advertised. They often consumed up to 105 cubic feet of gas per horsepower per hour.
- The exhaust cam often opens about 10° before the crank reaches bottom dead center. This allows some of the exhaust gases to escape before the compression stroke begins.
- The exhaust cam closes about 35° after the crank reaches bottom dead center. This ensures all the exhaust gases are expelled.
Terms:
- Otto Cycle: The four-stroke cycle of operation used in most gas engines, involving suction, compression, power, and exhaust strokes.
- Ignition Device: A mechanism that initiates the combustion process in the engine cylinder, using various methods like hot tube, porcelain tube, or electric spark.
- Vaporizer: A device used in oil engines to convert liquid oil into vapor, making it suitable for combustion.
- Governor: A mechanism that regulates engine speed and prevents overspeeding, often using centrifugal or inertia principles.
- Cams: Rotating components with shaped profiles that control the timing and duration of valve opening and closing.
- Valve Settings: The precise timing of valve opening and closing, which greatly influences engine efficiency.
- Compression Ratio: The ratio of the volume of the cylinder at the beginning of the compression stroke to the volume at the end of the stroke.
- Brake Horsepower (BHP): The actual power output of an engine, measured by a brake test.
- Half-Compression: A mechanism that allows for partial opening of the exhaust valve during the compression stroke, aiding in starting the engine.
- Homogeneous Mixture: A uniform and consistent blend of air and fuel, ensuring efficient combustion.
Examples:
- Barsanti and Matteucci: Developed an engine similar to Otto & Langen’s atmospheric engine, but it never became commercially successful.
- Robert Street’s engine: The first real gas engine, which used coal tar, spirit, or turpentine as fuel, with ignition by an external flame.
- Lenoir’s engine: A popular but inefficient engine that consumed a significant amount of gas.
- Otto & Langen’s atmospheric engine: Utilized a free piston and a rack-and-pinion system to generate power, achieving some commercial success.
- Hugon’s engine: A modification of Lenoir’s engine that employed water injection and flame ignition, reducing fuel consumption.
- Capel’s oil engine: A simple and efficient design that could be easily adapted from their existing gas engines.
- Hornsby-Akroyd’s engine: An early oil engine that used automatic ignition by compression heat.
- The Bunsen burner: A commonly used gas burner, producing a distinct inner (cold) cone and outer (hot) zone.
- The magneto ignition system: A self-contained generator that eliminates the need for batteries for spark ignition.
- The Capel oil engine vaporizer: A tubular casting with ribs and an annular space for mixing air and oil vapor.
Conclusion:
The text “Gas and Oil Engines, Simply Explained” provides a valuable historical perspective on the development of internal combustion engines. It outlines the fundamental principles of these engines, highlighting the importance of understanding gas behavior, ignition systems, governing mechanisms, and valve timing. The text offers practical insights into engine construction, operation, and maintenance, providing valuable information for both aspiring mechanics and those interested in the history of internal combustion engines.