Constant Volume Heat Addition

Advantages of constant volume heat addition

Constant volume heat addition can provide 50% more power and there by efficiency (15% of total fuels energy) while using same amount of fuel (Ref: ‘Design and Simulation of 4-Stroke Engines’ by SAE press – page 81; Author Gordon P. Blair). During ignition and flame propagation, the volume of charge is lowest, so faster flame propagation results (Fuel particles inthe mixture are closer to each other. And the distance from spark plug (From where the flame spreads) to most distant fuel particle is lowest.) So faster and better combustion Takes place. This also results in higher temperature with minimum fuel. This will increase efficiency. Since increasing T3 (combustion temperature) increases efficiency. Since surface area is lowest during combustion, less heat is lost to the surroundings. Since ignition is not done before compression stroke ends, there will not be any back pressure due to combustion. The combustion takes place faster due to the constant volume heat addition, so we get more work because of the earlier expansion of gases and a full power stroke with entire fuels energy converted to mechanical energy. In piston engine combustion finishes only after 15-30 degree of rotation from TDC. So only a part of the fuel’s energy is getting during TDC to 15-30 degree of rotation. Since combustion takes place at fairly high temperature all fuel particles are burned faster even near the surface of combustion chamber. Don’t forget that higher combustion temp is only because of the constant volume heat addition, all other factors like air/fuel ratio and compression ratio are kept same. Increasing T3 (combustion temperature) increases efficiency.

Implementation of constant volume heat addition in Anyoon Rotary Engine

Implementation of constant volume heat addition is considered to be a holy grail in IC engine design and Constant volume heat addition can provide 50% more power and there by efficiency while using same amount of fuel (Ref: ‘Design and Simulation of 4-Stroke Engines’ by SAE press – page 81; Author Gordon P. Blair).

Constant volume heat addition is possible by increasing the width of rotor’s one lobe. In the rotor (figure is on next page) from points A to B the radius of the outer profile is same as that of inner profile of Casing, so opening of combustion chamber is closed from points A to B (i.e. volume is constant). When point A of the rotor reaches point C of combustion chamber, opening of combustion chamber is closed and remains closed until point B on rotor crosses point D on combustion chamber. So we getconstant volume for combustion chamber during this period (i.e. 40-10= 30 angle of rotation of rotor). This angle can be increased. In piston engine normally combustion begins 20o before piston reaches TDC and combustion continuous until 30o of rotation of crank after TDC. More than 30 degree of constant volume heat addition can be achieved in the Anyoon Rotary Engine.