Diesel Combustion

In the context of internal combustion engines, including diesel engines, the term sinusoidal cam usually refers to the shape of the camshaft's lobes. The camshaft is responsible for opening and closing the engine's valves at appropriate times during the combustion cycle.

In 2006, the AVEC Workhorse 7.1 engine from Axial Vector Engine Corporation was fired-up and produced power for the first time in Detroit. The engine development testing continued with the resolution of test cell instrumentation issues. This was a significant and important event since it was the first time that a diesel engine with such a power transmission design (sinusoidal cam) ever fired up and produced power.

A sinusoidal cam is shaped such that the movement of the valve follows a sinusoidal motion profile. This means that the valve's rate of acceleration and deceleration as it opens and closes follows a smooth, continuous, wave-like pattern.

Sinusoidal Cam Benefits

1. Smooth Operation: The smooth acceleration and deceleration of the valves can lead to quieter operation and less wear on the valve train components.
2. Air Flow: The timing and rate of valve opening can influence the amount and speed of air that enters the combustion chamber, which can affect combustion efficiency and power output.
3. Power Delivery: The timing of valve opening and closing can be optimized for different engine speeds to deliver power more effectively.
4. Fuel Efficiency: Optimizing the valve timing can also improve fuel efficiency by ensuring that the right amount of air is mixed with the fuel.

In a diesel engine, the valve timing is particularly important because diesel engines rely on compression ignition. This means the fuel-air mixture is ignited by the heat of compression, not by a spark plug as in gasoline engines. Therefore, the amount and timing of air entering the combustion chamber can have a significant impact on the combustion process.

Sinusoidal Cam Rare

However, using a strictly sinusoidal cam profile is not standard practice in the design of diesel engines, or any internal combustion engines. This is because the ideal valve motion profile for engine performance and efficiency tends to be more complex than a simple sinusoid. This is something that engineers take into account when designing engines, and they use a variety of techniques and technologies, such as variable valve timing, to achieve the desired performance characteristics.

Other Advances in Diesel Engine Technology

1. Common Rail Fuel Injection: This technology, which uses a common rail to supply fuel to all the engine's injectors, allows for precise control of fuel injection timing and quantity. This can result in improved fuel efficiency, reduced emissions, and better performance.
2. Variable Geometry Turbocharging: Variable geometry turbochargers can adjust the flow of exhaust gas to the turbine, improving efficiency across a wide range of engine speeds. This can provide better low-speed torque and response while also improving high-speed power and efficiency.
3. Exhaust Gas Recirculation (EGR): EGR systems recirculate a portion of the engine's exhaust back into the intake, reducing the production of nitrogen oxides (NOx), which are harmful pollutants. This can be particularly beneficial in meeting stricter emission regulations.
4. Selective Catalytic Reduction (SCR): This is another technology used to reduce NOx emissions. It uses a urea solution (often marketed as Diesel Exhaust Fluid or DEF) which, when injected into the exhaust stream and passed over a catalyst, breaks down NOx into nitrogen and water.
5. Diesel Particulate Filters (DPF): These devices capture soot particles in the exhaust stream, preventing them from being released into the atmosphere. The soot is periodically burned off in a process known as regeneration.
6. Advanced Engine Control Units (ECU): Modern diesel engines use sophisticated computer controls to optimize every aspect of engine operation, including fuel injection, valve timing, turbocharging, and emissions control systems. This can improve efficiency, power, and emissions performance.
7. Hybridization: Some manufacturers have introduced hybrid systems that combine a diesel engine with an electric motor and battery. This can significantly improve fuel efficiency and reduce emissions, particularly in city driving.
8. Biodiesel and Renewable Diesel: Advances in fuel technology have resulted in cleaner-burning diesel alternatives, such as biodiesel and renewable diesel. These fuels can be used in diesel engines without modification and can significantly reduce greenhouse gas emissions.
9. Low-Temperature Combustion: Experimental technologies like homogeneous charge compression ignition (HCCI) and other forms of low-temperature combustion have the potential to further improve the efficiency and emissions performance of diesel engines.