Split-cycle four-stroke engine
View Patent ↗An engine has a crankshaft, rotating about a crankshaft axis of the engine. An expansion piston is slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft. A compression piston is slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke of the same four stroke cycle during the same rotation of the crankshaft. A ratio of cylinder volumes from BDC to TDC for either one of the expansion cylinder and compression cylinder is substantially 20 to 1 or greater.
1. An engine comprising:
a crankshaft, rotating about a crankshaft axis of the engine;
an expansion piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft;
a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke of the same four stroke cycle during the same rotation of the crankshaft; and
a ratio of cylinder volumes from BDC to TDC for either one of the expansion cylinder and compression cylinder being substantially 26 to 1 or greater at full load.
2. The engine of claim 1 comprising the ratio of cylinder volumes from BDC to TDC for either one of the expansion cylinder and compression cylinder being substantially 40 to 1 or greater.
3. The engine of claim 1 comprising the ratio of cylinder volumes from BDC to TDC for either one of the expansion cylinder and compression cylinder being substantially 80 to 1 or greater.
4. The engine of claim 1 comprising the expansion piston and the compression piston having a TDC phasing of substantially 50° crank angle or less.
5. The engine of claim 1 comprising the expansion piston and the compression piston having a TDC phasing of less than 30° crank angle.
6. The engine of claim 1 comprising the expansion piston and the compression piston having a TDC phasing of substantially 25° crank angle or less.
7. The engine of claim 1 comprising:
a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including an inlet valve and a crossover valve defining a pressure chamber therebetween, wherein the crossover valve has a crossover valve duration of substantially 69° of crank angle or less.
8. The engine of claim 7 comprising the crossover valve having a crossover valve duration of substantially 50° of crank angle or less.
9. The engine of claim 7 comprising the crossover valve having a crossover valve duration of substantially 35° of crank angle or less.
10. The engine of claim 7 wherein the crossover valve remains open during at least a portion of a combustion event in the expansion cylinder.
11. The engine of claim 10 wherein substantially at least 5% of the total combustion event occurs prior to the crossover valve closing.
12. The engine of claim 10 wherein substantially at least 10% of the total combustion event occurs prior to the crossover valve closing.
13. The engine of claim 10 wherein substantially at least 15% of the total combustion event occurs prior to the crossover valve closing.
14. An engine comprising:
a crankshaft, rotating about a crankshaft axis of the engine;
an expansion piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft;
a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke of the same four stroke cycle during the same rotation of the crankshaft; and
a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including an inlet valve and a crossover valve defining a pressure chamber therebetween;
wherein the crossover valve permits subtantially one way flow of gas from the pressure chamber to the expansion cylinder during the entire four stroke cycles, the crossover valve has a crossover valve duration of substantially 49° of crank angle or less, piston reaches top dead center.
15. The engine of claim 14 comprising the crossover valve having a crossover valve duration of substantially 50° of crank angle or less.
16. The engine of claim 14 comprising the crossover valve having a crossover valve duration of substantially 35° of crank angle or less.
17. The engine of claim 14 comprising the expansion piston and the compression piston having a TDC phasing of substantially 50° crank angle or less.
18. The engine of claim 14 comprising the expansion piston and the compression piston having a TDC phasing of less than 30° crank angle.
19. The engine of claim 14 comprising the expansion piston and the compression piston having a TDC phasing of substantially 25° crank angle or less.
20. The engine of claim 14 wherein the crossover valve remains open during at least a portion of a combustion event in the expansion cylinder.
21. The engine of claim 20 wherein substantially at least 5% of the total combustion event occurs prior to the crossover valve closing.
22. The engine of claim 20 wherein substantially at least 10% of the total combustion event occurs prior to the crossover valve closing.
23. The engine of claim 20 wherein substantially at least 15% of the total combustion event occurs prior to the crossover valve closing.
24. The engine of claim 14 wherein the crossover valve opens between 0 and 10° of crank angle before the expansion piston reaches top dead center.
25. A method of combusting gas in an engine, the engine including a crankshaft, rotating about a crankshaft axis of the engine, an expansion piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft, a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke of the same four stroke cycle during the same rotation of the crankshaft; and a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including an inlet valve and a crossover valve defining a pressure chamber therebetween, the method comprising the steps of:
intaking gas into the compression cylinder of the engine;
compressing the gas within the compression cylinder;
opening the inlet valve to permit flow of the compressed gas from the compression cylinder to the crossover passage of the engine;
opening the crossover valve to permit flow of the compressed gas from the crossover passage to the expansion cylinder of the engine; and
initiating combustion of the gas within the expansion cylinder while the crossover valve is still open.
26. The method of claim 25 further comprising the step of:
closing the crossover valve after at least 5% of the total combustion of the gas has occurred.
27. The method of claim 25 further comprising the step of:
closing the crossover value after at least 10% of the total combustion of the gas has occurred.
28. The method of claim 25 further comprising the step of:
closing the crossover valve after at least 15% of the total combustion of the gas has occurred.