Dynamic Flow Engine Valve Configuration & Gas Flow

Challenges in Conventional 4-Stroke and 2-Stroke Engines:

Over the past 10 to 15 years, there has been little improvement in the thermal efficiency of conventional combustion engines, whether in laboratory settings or real-world applications. At Dynamic Alpha Automotive Technology, we have identified that the flow capacity of gases in conventional 4-stroke and 2-stroke engines is a key factor limiting their potential for achieving higher thermal efficiency and power output.

Two-stroke engines have approximately 50% greater intake air flow and 135% greater exhaust gas flow compared to conventional 4-stroke engines. However, the operational cycles of 2-stroke engines have significantly shorter gas flow durations than 4-stroke engines.

In modern engines, the flow of intake air and exhaust gases plays a crucial role in both rapid high-power generation and slower, more efficient power generation. Engines designed for higher acceleration and horsepower tend to be less efficient than those designed for slower acceleration and higher torque. This is because the design elements that enhance engine efficiency often conflict with those that increase power output in terms of gas flow.

In conventional 4-stroke engines, the intake and exhaust valves are located at the top of the cylinder within the cylinder head, occupying the available surface area. The operational nature of 4-stroke engines requires that these valves be in close proximity to each other, and the surface area of the cylinder head is limited by the diameter of the cylinder. Consequently, engines with larger cylinder diameters have more surface area available for larger or more numerous intake and exhaust valves. Larger or more numerous valves can reduce gas flow restriction at higher RPMs, translating into higher power generation.

One proven mechanical approach to increasing combustion engine thermal efficiency is to adopt a more undersquare engine design, characterized by a smaller bore-to-stroke ratio, where the bore is smaller than the stroke. To maintain a similar compression ratio, any change in stroke length requires a corresponding change in bore size. The bore diameter must decrease as the stroke length increases to retain the same compression ratio. As a result, more efficient engines typically have smaller bore diameters, which indirectly reduces the surface area available at the cylinder head for intake and exhaust valves. This reduction leads to smaller valves, which restrict gas flow at higher RPMs and thus decrease engine’s acceleration performance.

Dynamic Flow Engine’s Larger Gas Flow Capacity:

The Dynamic Flow engine revolutionizes valve placement by moving the intake and exhaust valves outside of the cylinder and combustion chamber. This allows for larger intake and exhaust valves with higher gas flow rates and longer flow durations, unhindered by the constraints of the engine’s operational process. The Dynamic Flow engine introduces a new type of valve, the “main cylinder valve,” which performs dual tasks—acting as both an intake valve during the intake stroke and an exhaust valve during the exhaust stroke. This dual functionality allows for more numerous valves with a higher gas flow rate, comparable to that of a 2-stroke engine. However, as a 4-stroke engine, it retains the longer gas flow duration characteristic of 4-stroke engines. This combination results in a significantly higher gas flow capacity compared to both conventional 4-stroke and 2-stroke engines.

Adopting a More Undersquare Engine Design:

With its larger gas flow capacity, the Dynamic Flow engine can adopt a more undersquare design for higher efficiency without sacrificing performance at higher RPMs. An undersquare engine features a longer stroke and a smaller bore diameter. While a smaller bore typically requires smaller valves, the Dynamic Flow engine’s more numerous main cylinder valves ensure sufficient performance even at higher RPMs. For instance, a 3.0-liter I6 Dynamic Flow engine with an undersquare design can achieve similar horsepower to an oversquare 3.0-liter I6 conventional engine, while also offering significantly higher thermal efficiency.

Core Advantages of Engine with Higher Gas Flow Capacity:

The Dynamic Flow engine’s larger gas flow capacity allows it to achieve significantly higher thermal efficiency than current 4-stroke engines. Dynamic Flow gasoline and diesel engines can reach thermal efficiencies of 48% or higher, marking a substantial improvement in 4-stroke engine technology.

Comparison of Gas Flow Between Conventional 4-Stroke Engine and Dynamic Flow Engine

In our OpenFOAM computational fluid dynamics (CFD) study of a single-cylinder, conventional 4-stroke engine with a bore diameter of 5.5 inches, the intake and exhaust valves were set to the maximum size allowed by the cylinder bore, with a volumetric flow rate of 200 liters per second. We observed a 10.13% pressure drop in the intake airflow and a 30.67% pressure drop in the exhaust gases flow. These pressure drops indicate restrictions in gas flow, with lower pressure drops being more favorable. Higher pressure drops signal increased valve restrictions, which negatively impact engine efficiency and performance.

Our OpenFOAM CFD study of a single-cylinder Dynamic Flow engine with a bore diameter of 5.5 inches, the main cylinder valve was set to the maximum size permitted by the cylinder bore, with a volumetric flow rate of 200 liters per second. We observed a 3.79% pressure drop in the intake airflow and a 4.16% pressure drop in the exhaust gas flow. Comparing the CFD pressure data between the conventional 4-stroke engine and the Dynamic Flow engine, we can conclude that the Dynamic Flow valve system has superior gas flow compare to conventional 4-stroke engine valve system with a similar bore size.

Our OpenFOAM CFD study of a single-cylinder Dynamic Flow engine with a bore diameter of 4.57 inches, we reduced the main cylinder valve size by 33.4% to imitate engine with smaller undersquare bore design, volumetric flow rate were set at 200 liters per second. This bore size and valves size adjustment resulted in a 7.09% pressure drop in intake airflow and a 7.54% pressure drop in exhaust gas flow. When comparing the CFD pressure data between the conventional 4-stroke engine with a 5.5-inch bore and the Dynamic Flow engine with the reduced bore size of 4.57 inches, we found that the Dynamic Flow valve system, even with a smaller bore, surpasses the conventional 4-stroke engine valve system in gas flow capacity.

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