Variable cycle stirling engine and gas leakage control system therefor

A thermal engine comprising:

• an engine housing;
• a chamber defined within said housing;
• a displacer piston reciprocable within said chamber;
• a working fluid within said chamber susceptible to a thermodynamic cycle responsively to movement of said displacer piston;
• a first piston bore defined in said housing;
• a work piston reciprocably driven by said working fluid within said first bore;
• a hydraulic piston reciprocable for pumping an output fluid in a second piston bore defined in said housing;
• partition means defining a linkage bore between said first and second piston bores;
• linkage rod means extending through said linkage bore and transmitting the reciprocating movement of said work piston to said hydraulic piston, said linkage bore being of reduced diameter relative to either of said piston bores to thus facilitate sealing of said working and output fluids against leakage from their respective piston bores.

In a thermal engine of the type having a displacer piston reciprocable within a displacer chamber, an engine burner, a working fluid within said chamber susceptible to a thermodynamic cycle responsively to movement of said displacer piston and a working piston driven by said working fluid, an improved compound work piston comprising:

• a first work piston element reciprocable in a first bore and driven by said working fluid;
• a second work piston element reciprocable in a second bore for pumping a hydraulic fluid;
• means defining a passage between said first and second bores, said passage being of restricted aperture relative to the diameter of either of said first or second bores;
• linkage means extending through said passage for transmitting the reciprocating movement of said first work piston element to said second work piston element;
• and
• dynamic seal means for substantially sealing said passage against leakage of said working fluid therethrough into said second bore.

A thermal engine comprising:

• an engine housing;
• a chamber defined within said housing;
• a displacer piston within said chamber;
• means for reciprocating said displacer piston;
• a working fluid within said chamber susceptible to a thermodynamic cycle responsively to movement of said displacer piston;
• a work piston reciprocably driven by said working fluid;
• and
• means for locking said working piston against movement during selected portions of of the displacer movement independently from said means for reciprocating said displacer piston.

A thermal engine comprising:

• an engine housing;
• a chamber defined within said housing;
• a displacer piston within said chamber;
• means for reciprocating said displacer piston;
• a working fluid within said chamber susceptible to a thermodynamic cycle responsively to movement of said displacer piston;
• a work piston reciprocably driven by said working fluid;
• and
• liquid spring means compressed by said working piston and valve means associated with said liquid spring means for slowing or stopping said working piston relative to said displacer piston independently from said means for reciprocating said displacer piston.

A thermal engine comprising:

• an engine housing;
• a chamber defined within said housing;
• a displacer piston within said chamber;
• means for reciprocating said displacer piston;
• a working fluid within said chamber susceptible to a thermodynamic cycle responsively to movement of said displacer piston;
• a work piston reciprocably driven by said working fluid;
• said working piston working against a hydraulic fluid to produce an output of hydraulic fluid;
• a source of hydraulic fluid connected for supplying fluid to said piston;
• an accumulator connected for receiving said hydraulic output;
• valve means connected for restricting one or both of said supply and said output of hydraulic fluid to thereby control the motion of said working piston relative to said displacer piston;
• sensor means for deriving a first input indicative of the position of said displacer piston and a second input indicative of the position of said working piston;
• and
• engine controller means receiving said first and second inputs and deriving an output connected for controlling said valve means in predetermined relationship to said inputs.