Internal combustion engine mechanism
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Internal Combustion Engine Mechanism: Key Components and Variations
Basic Mechanism and Components of Internal Combustion Engines
The traditional internal combustion engine (ICE) mechanism consists of cylinders where combustion occurs, pistons that move up and down, connecting rods that link the pistons to a crankshaft, and the crankshaft itself, which converts the pistons' linear motion into rotational motion. This setup is often enhanced with mechanisms to alter the compression ratio, such as length-altering connecting rods, and lubrication systems to reduce friction and wear on moving parts .
Crankshaft and Connecting Rod Mechanism
The most common ICE mechanism uses a crankshaft and connecting rod system. The piston moves within the cylinder, and the connecting rod transmits this motion to the crankshaft, which rotates to produce usable power. Some designs introduce an offset crankshaft, which increases mechanical efficiency, net torque output, and reduces friction between the piston and cylinder, leading to smoother operation and less energy loss .
Alternative Mechanisms for Improved Efficiency
Several studies have proposed alternative mechanisms to address the inefficiencies of the traditional crankshaft system:
- Rack and Pinion Mechanisms: Replacing the connecting rod with a rack and the crankshaft with a gear can maintain a constant force arm, improving efficiency and simplifying the structure. This design ensures the force applied by the piston is always optimal, regardless of its position, and can replace the conventional crankshaft-connecting rod system . A similar approach uses a rack and pinion assembly connected to a crank rocker four-bar mechanism, eliminating side-thrust loads and piston slap, which increases work per cycle by about 27% and reduces noise and friction .
- Direct Gear Transmission: Another innovative mechanism eliminates the crankshaft for power transmission, using partial teething gears attached directly to the pistons. This design transmits kinetic energy more efficiently, doubling the power output during the power stroke compared to classical engines .
- Cycloidal and Rotary Mechanisms: Some engines use cycloidal curves and rotary pistons, with components like flywheels, sun gears, and planetary gears. These mechanisms create multiple combustion chambers and use rotary motion to achieve the four-stroke cycle, offering unique kinematic properties .
Addressing Energy Losses and Parasitic Forces
Traditional crank mechanisms are responsible for significant energy losses in ICEs, with over 30% of the pressure force energy lost to parasitic forces such as friction in plain bearings. Research suggests that replacing these with mechanisms that minimize or eliminate parasitic forces, such as those using rolling bearings or direct gear transmission, can increase engine efficiency by up to 130% or more. Rolling bearings alone can improve efficiency by an additional 4-6% compared to plain bearings .
Dual Combustion Chambers and Power Multiplication
Some advanced ICE designs feature dual combustion chambers within a single cylinder, increasing the utilization rate of the cylinder and boosting engine power. This is achieved by having upper and lower cylinder covers, each with their own inlets, outlets, and injectors, allowing for more efficient combustion and power output .
Novel and Original Mechanism Designs
Newly proposed mechanisms, such as the MF1, offer alternative ways to determine and optimize the kinematics and efficiency of ICEs. These designs focus on dynamic efficiency and can be adapted to work as both engines and other mechanical devices, with efficiency calculations that can include or exclude friction effects .
Conclusion
The internal combustion engine mechanism has evolved from the classic crankshaft and connecting rod system to include a variety of innovative designs aimed at improving efficiency, reducing friction, and increasing power output. Alternative mechanisms such as rack and pinion systems, direct gear transmission, cycloidal rotary engines, and dual combustion chambers demonstrate significant potential for future ICE development. Addressing parasitic forces and optimizing mechanical transmission are key to achieving higher efficiency and better performance in internal combustion engines 葛宪琪2013梁振勇2011Dado2021+5 MORE.
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