Hot gas engine

A hot gas engine (1) comprising:

• a cylinder (2) extending in a longitudinal direction having a first end (3), a second end (4) and a longitudinal extending wall (5) between said first and second ends (3, 4) thereby defining a cylinder space, said cylinder (2) further provided with inlet (15, 17) and outlet (16, 18) openings for a working fluid to enter into and to be exhausted from said cylinder (2);
• a piston (6) located within said cylinder (2), said piston (6) adapted to be able to move back and forth within said cylinder (2) in the longitudinal direction and having a first surface (7) facing said first end (3) of said cylinder (2) thereby defining together with the longitudinal extending cylinder wall (5) a first cylinder chamber (9) within the cylinder (2), said piston (6) further having a second surface (8) facing the second end (4) of said cylinder (2) thereby defining together with the cylinder wall (5) a second cylinder chamber (10) within the cylinder;
• and
• a piston rod (11) having a first end (12) and a second end (13) wherein said first end (12) is connected to said piston (6), said piston rod (11) passing through said cylinder (2) through either said first or second end (3, 4) of the cylinder (2),
• wherein said first cylinder chamber (9) comprises a first inlet opening (15) provided with a first inlet valve (19) and a first outlet opening (16) provided with a first outlet valve (20),
• wherein said second cylinder chamber (10) comprises a second inlet opening (17) provided with a second inlet valve (21) and a second outlet opening (18) provided with a second outlet valve (22),
• wherein said first outlet opening (16) in the first cylinder space (9) is connected to said second inlet opening (17) in the second cylinder space (10) so as to allow a flow of working fluid from said first cylinder chamber (9) to said second cylinder chamber (10), wherein said engine (1) comprises an external heating chamber (23) connected by a third inlet opening (24) in the heating chamber (23) to said first outlet opening (16) in the first cylinder space (9) and a third outlet opening (25) in the heating chamber (23) is connected to said second inlet opening (17) in the second cylinder space (10) so as to allow a flow of working fluid from said first cylinder chamber (9) to said second cylinder chamber (10) via said heating chamber (23),
• wherein said engine (1) is designed to transfer work from the piston rod (11) by an essentially only rectilinear movement of the piston rod (11),
• wherein the ratio between the maximum volume of the first cylinder chamber (9) and the maximum volume of the second cylinder chamber (10) is selected between 1:1.5 and 1:2,
• wherein said heating chamber (23) is provided with a burner for heating gases in the heating chamber (23), the burner being located within the heating chamber (23), the burner combusting a fuel in the heating chamber thereby producing combustion products that form part of the flow of working fluid from said first cylinder chamber (9) to said second cylinder chamber (10), the heating chamber being free of any heat exchanger,
• wherein said hot gas engine (1) is arranged such that during a major part of a first stroke during which the piston (6) travels from the first end (3) of the cylinder (2) to the second end (4) of the cylinder (2) the valves (19, 20, 21, 22) are controlled such that
• i) said first inlet valve (19) in the first inlet opening (15) in the first piston chamber (9) and said second outlet valve (22) in the second outlet opening (18) in the second cylinder chamber (10) are open, and
• ii) said first outlet valve (20) in said first outlet opening (16) in said first cylinder chamber (9) and said second inlet valve (21) in said second inlet opening (17) in said second cylinder chamber (10) are closed in order to provide for a constant volume heating of the gas comprised in the heating chamber (23) while essentially no work is performed on or by the piston (6),
• wherein said hot gas engine (1) is further arranged such that
• i) said first inlet valve (19) in said first inlet opening (15) in said first cylinder chamber (9) and said second outlet valve (22) in said second outlet opening (18) of the second cylinder chamber (10) are closed during a major part of a second stroke during which the piston (6) moves from the second end (4) to the first end (3) of the cylinder (2),
• ii) during a first phase of said second stroke, said first outlet valve (20) in said first outlet opening (16) in said first cylinder chamber (9) is closed while said second inlet valve (21) in said second inlet opening (17) in said second cylinder chamber (10) is open thus allowing the heated gas from said heating chamber (23) to expand into the second cylinder chamber (10) while performing a positive work on the piston (6) such that the gas in the first chamber (9) will be compressed, and
• iii) during a second phase of said second stroke said first outlet valve (20) in said first outlet opening (16) in said first cylinder chamber (9) is open while said second inlet valve (21) in said second inlet opening (17) in said second cylinder chamber (10) is closed thus allowing the gas in the second chamber (10) to expand only within the second chamber (10) while the gas comprised in the first cylinder chamber (9) is compressed together with the gas comprised in the heating chamber (23) while performing a negative work on the piston (6).