Method and apparatus for achieving higher thermal efficiency in a steam engine or steam expander

A method of operating a steam expander for producing power in an engine having at least one cylinder, a piston sealingly and slidably mounted for reciprocation within the cylinder and operatively connected to a crankshaft, said method comprising the steps of:

• providing a cylinder head that includes spaced apart steam inlet and steam exhaust valves that each has a valve head with a face located on an end wall of a steam expansion chamber and both valves communicate with the steam expansion chamber located between the piston and the cylinder head,
• maintaining the exhaust valve open during at least a terminal part of an exhaust stroke of the piston,
• providing a clearance between the piston and cylinder head of a magnitude that is about 8% or less of a stroke of the piston,
• preventing contact between the piston and cylinder head while the steam in a clearance volume between the piston and the cylinder head is at a pressure established by the steam exhaust valve being open during the terminal part of the exhaust stroke of the piston such that the pressure in the clearance volume at a closing of the exhaust valve approximates ambient or condenser pressure, and
• providing a transition from exhausting through said exhaust valve and an admission of steam through said admission valve by a bump force applied to each valve by piston contact proximate the terminal part of the exhaust stroke of the piston when the cylinder clearance is minimized.

A method of operating a steam expander of an engine having at least one cylinder, a cylinder head, a piston sealingly and slidably mounted for reciprocation within the cylinder and operatively connected to a crankshaft, said method comprising the steps of:

• providing a steam inlet valve comprising a valve body yieldable biased to a closed position and a steam exhaust valve that both communicate with a cylinder having a piston slidably mounted therein and a cylinder head at one end thereof defining a steam expansion chamber therebetween,
• providing a clearance of about eight percent or less of the stroke between the piston and the cylinder head while determining a steam compression in the steam expansion chamber between the piston and the cylinder head by exhausting steam through the exhaust valve proximate an end of an exhaust stroke of the piston and the exhaust valve then being closed such that the steam compression in the steam expansion chamber before steam is injected does not exceed a pressure established by the exhaust valve being open proximate the end of the exhaust stroke of the piston,
• locating a face of each valve on an end of the steam expansion chamber in the cylinder that is devoid of an empty recess that contributes substantially to a clearance volume and
• providing a transition from exhausting through said exhaust valve and a steam admission through said admission valve without significant loss of an admission steam mass through the exhaust valve by closing the steam exhaust valve proximate an opening of the steam inlet valve.

A method of operating a steam expander for producing power in an engine having at least one cylinder, a piston sealingly and slidably mounted for reciprocation within the cylinder and operatively connected to a crankshaft, said method comprising the steps of:

• providing a cylinder head that includes spaced apart steam inlet and steam exhaust valves located on an end wall of a steam expansion chamber and both valves communicate with a steam expansion chamber located between the piston and the cylinder head,
• maintaining the exhaust valve open during at least a terminal part of an exhaust stroke of the piston,
• providing a clearance between the piston and cylinder head of a magnitude that is about 8% or less of a stroke of the piston,
• preventing contact between the piston and cylinder head while the steam in a clearance volume between the piston and the cylinder head is at a pressure established by the steam exhaust valve being open during the terminal part of the exhaust stroke of the piston such that the pressure in the clearance volume at a closing of the exhaust valve approximates ambient or condenser pressure, and
• providing a transition from exhausting through said exhaust valve and an admission of steam through said admission valve by a bump force applied to each valve by piston contact proximate termination of the exhaust stroke of the piston when the cylinder clearance is minimized and including the step of:
• facilitating the actuation of the admission valve by applying a steam power assist to the admission valve to open the admission valve by the force of the steam applied thereto from a steam supply that is used to run the engine.

A method of operating a steam expander for producing power in an engine having at least one cylinder, a piston sealingly and slidably mounted for reciprocation within the cylinder and operatively connected to a crankshaft, said method comprising the steps of:

• providing a cylinder head that includes spaced apart steam inlet and steam exhaust valves located on an end wall of the steam expansion chamber and both valves communicate with a steam expansion chamber located between the piston and the cylinder head,
• maintaining the exhaust valve open during at least a terminal part of an exhaust stroke of the piston,
• providing a clearance between the piston and cylinder head of a magnitude that is less about 8% of a stroke of the piston,
• preventing contact between the piston and cylinder head while the steam in a clearance volume between the piston and the cylinder head is at a pressure established by the steam exhaust valve being open during the terminal part of the exhaust stroke of the piston such that the pressure in the clearance volume at a closing of the exhaust valve approximates ambient or condenser pressure,
• providing a transition from exhausting through said exhaust valve and an admission of steam through said admission valve by a bump force applied to each valve by piston contact proximate the terminal part of the exhaust stroke of the piston when the cylinder clearance is minimized, and
• providing the steam expander as a part of a dual cycle internal combustion steam engine having at least one combustion chamber therein for burning fuel and a combustion exhaust port connected for providing exhaust gasses to fire a heater for steam that is supplied to the steam expansion chamber of the engine.

A method of operating a steam expander of an engine having at least one cylinder, a cylinder head, a piston sealingly and slidably mounted for reciprocation within the cylinder and operatively connected to a crankshaft, said method comprising the steps of:

• providing a steam inlet valve comprising a valve body yieldable biased to a closed position and a steam exhaust valve that both communicate with a cylinder having a piston slidably mounted therein and a cylinder head at one end thereof,
• providing a clearance of about eight percent or less of the stroke between the piston and the cylinder head while determining a steam compression in an expansion chamber between the piston and the cylinder head by exhausting steam through the exhaust valve proximate an end of an exhaust stroke of the piston and the exhaust valve then being closed such that the steam compression in the expansion chamber before steam is injected does not exceed a pressure established by the exhaust valve being open proximate the end of the exhaust stroke of the piston,
• providing a transition from exhausting through said exhaust valve and a steam admission through said admission valve without significant loss of an admission steam mass through the exhaust valve by closing the steam exhaust valve proximate an opening of the steam inlet valve,
• providing a valve face on a free end surface of the inlet valve,
• sealingly mounting the inlet valve in a bore having a compartment in communication with the inlet valve,
• momentarily holding the inlet valve open by steam pressure applied to the valve face thereof, and
• providing a steam admission timing control by selecting a flow of steam into the compartment communicating with the inlet valve for regulating a fraction of the power stroke of the piston during which steam is admitted through said inlet valve.

A method of operating a steam expander of an engine having at least one cylinder, a cylinder head and a piston that is operatively connected to a crankshaft and is sealed in the cylinder for performing a power stroke and a return stroke, said method comprising the steps of:

• (a) providing a steam admission port in the cylinder head that is sealed by a steam admission valve which is located within a bore in the cylinder head so as to open in a direction away from a steam expansion chamber for controlling the admission of supply steam into the steam expansion chamber within the cylinder through the steam admission port and allowing pressure in the bore on an opposite side of steam admission valve from the steam admission port in the cylinder to fall after each power stroke such that the steam supplied thereto establishes is a pressure differential across the steam admission valve that forces the admission valve open by steam pressure applied thereto,
• (b) providing an exhaust outlet communicating with the expansion chamber that is sealed by an exhaust valve which is located in the exhaust outlet,
• (c) coupling the piston to the crankshaft so as to provide a clearance between the piston and a cylinder head that is no greater than about 8% of a maximum clearance between the cylinder head and the piston,
• (d) operating the exhaust valve to keep the exhaust outlet open during at least a portion of the return stroke for exhausting steam from the cylinder,
• (e) providing the clearance between the cylinder head and the piston at a minimum and the piston proximate an end of the piston return stroke while the exhaust valve is open and
• (f) closing the exhaust valve and opening the steam admission valve to inject steam into the clearance between the cylinder head and the piston proximate a beginning of the power stroke to thereby power the engine and impart rotation to the crankshaft.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve body having a sidewall slidably mounted in a bore having a compartment on a first side of an admission valve, the admission valve being operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder on a second side of the admission valve between the piston and the cylinder head and an aperture radially outward of the steam admission valve body sidewall to apply steam pressure to the sidewall when the admission valve is closed and thereafter when partially open applying steam pressure to an end thereof that forces the admission valve open,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• an operative connection between the piston and the crankshaft that maintains a clearance between the cylinder head and the piston at about 8% or less of the clearance at maximum displacement, and
• an exhaust valve mechanism element for opening the exhaust valve that is operatively associated with the exhaust valve so as to exhaust steam from the cylinder through the exhaust valve during a portion of each return stroke of the piston within the cylinder, and
• a member for shutting the exhaust valve proximate an end of each exhaust stroke for reducing compression of residual steam remaining within a clearance volume.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve in a bore having a compartment on a first side of the steam admission valve, the steam admission valve being operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder on a second side of the admission valve between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• an operative connection between the piston and the crankshaft that maintains a clearance between the cylinder head and the piston at about 8% or less of the clearance at maximum displacement,
• an exhaust valve mechanism element for opening the exhaust valve that is operatively associated with the exhaust valve so as to exhaust steam from the cylinder through the exhaust valve during a portion of each return stroke of the piston within the cylinder, and
• a member for shutting the exhaust valve proximate an end of each exhaust stroke for reducing compression of residual steam remaining within a clearance volume, and
• wherein the steam admission valve is opened by the piston or a lifter operatively associated therewith, and
• wherein a timing delay element is operatively associated with the admission valve to reduce or eliminate power loss due to reverse torque caused by a premature opening thereof while the clearance volume is contracting.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve in a bore having a compartment on a first side of the steam admission valve, the steam admission valve being operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder on a second side of the admission valve between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• an operative connection between the piston and the crankshaft that maintains a clearance between the cylinder head and the piston at about 8% or less of the clearance at maximum displacement,
• an exhaust valve mechanism element for opening the exhaust valve that is operatively associated with the exhaust valve so as to exhaust steam from the cylinder through the exhaust valve during a portion of each return stroke of the piston within the cylinder, and
• a member for shutting the exhaust valve proximate an end of each exhaust stroke for reducing compression of residual steam remaining within a clearance volume,
• wherein the steam admission valve further comprises:
• an axially movable poppet valve element, and
• a metering valve connected for adjusting a rate of flow for steam flowing from the steam expansion chamber to the compartment in the bore to thereby achieve a desired timing to regulate the cutoff of steam by the valve element to the steam expansion chamber.

A steam expander of an engine comprising:

• at least one cylinder, a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• wherein the admission valve is a poppet valve comprising a poppet piston having a cylindrical sidewall slidably and sealingly enclosed within a cylindrical bore that terminates in a valve seat and the poppet piston is yieldably biased toward a closed position against the valve seat in the engine at one end of the bore, the poppet piston having a valve face that extends centrally from the sidewall thereof and also extends centrally from a wall of the bore to form a seal against the seat when the admission valve is closed, and
• a steam supply chamber in the engine communicating between the bore and a steam supply,
• such that with the poppet piston in the closed position steam in the supply chamber is unable to apply an axial force on the poppet piston but when the valve is at least partially open steam from the supply chamber is able to flow into the bore between the face of the poppet piston and the steam expansion chamber to thereby create a pressure differential across the poppet piston that exerts an axial lifting force on the poppet piston which slides the poppet piston open by means of the lifting force of the steam to a more fully open position.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve having a face located in a wall of the cylinder head that forms an end of the cylinder so as to confront the piston for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke;
• wherein the exhaust valve is open during a substantial part of each exhaust stroke,
• an exhaust valve mechanism element for closing the exhaust valve exhaust valve when the admission valve opens proximate an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to a closing of the exhaust valve that is able to trap a remaining residual fraction of the initial steam mass which was not exhausted,
• wherein the operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at the beginning of said exhaust stroke, and
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve located in the cylinder head so as to confront the piston for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve mechanism having an exhaust valve that is open during a substantial part of each exhaust stroke,
• an exhaust valve mechanism element for closing the exhaust valve when the admission valve opens proximate an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to the closing of the exhaust valve that is able to trap a remaining residual fraction of the initial steam mass which was not exhausted,
• wherein an operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at a beginning of said exhaust stroke,
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume;
• and
• wherein the admission valve includes a delay element that retards the opening thereof after the admission valve leaves a valve seat while the piston is still approaching an end of each steam exhaust stroke.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve having a face-located in a wall of the cylinder head that forms an end of the cylinder so as to confront the piston for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke;
• wherein the exhaust valve is open during a substantial part of each exhaust stroke,
• an exhaust valve mechanism element for closing the exhaust valve when the admission valve opens proximate an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to a closing of the exhaust valve that is able to trap a remaining residual fraction of the initial steam mass which was not exhausted,
• wherein the operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of a clearance at a beginning of said exhaust stroke,
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume;
• and
• wherein a control member is operatively associated with the steam admission valve to time the closing thereof.

A steam expander of an engine comprising:

• at least one cylinder, a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• wherein the admission valve is a poppet valve comprising a poppet piston having a cylindrical sidewall slidably and sealingly enclosed within a cylindrical bore that terminates in a valve seat and the poppet piston is yieldably biased toward a closed position against the valve seat in the engine at one end of the bore, the poppet piston having a valve face that extends centrally from the sidewall to form a seal against the seat when the admission valve is closed, and
• a steam supply chamber in the engine communicating between the bore and a steam supply,
• such that with the poppet piston in the closed position steam in the supply chamber is unable to apply an axial force on the poppet piston but when the valve is at least partially open steam from the supply chamber is able to flow into the bore between the face of the poppet piston and the steam expansion chamber to thereby create a pressure differential across the poppet piston that exerts an axial lifting force on the poppet piston which slides the poppet piston open by means of the lifting force of the steam to a more fully open position and
• wherein the admission valve includes a delay element that retards the opening thereof when the valve face leaves the valve seat as the piston approaches the end of a return stroke.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve located in the cylinder head for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke;
• an exhaust valve mechanism element that holds the exhaust valve open during a substantial part of each exhaust stroke,
• a member that closes the exhaust valve when the admission valve opens proximate dead center at an end of each exhaust stroke such that any compression at the end of each exhaust stroke is substantially compression due to the closing of the exhaust valve that is able to trap a remaining residual fraction of the initial steam mass,
• wherein an operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at a beginning of said exhaust stroke,
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume;
• and
• wherein the admission valve has a timing control including a metering valve connected to control a pressure differential across the admission valve for establishing a closing time for the admission valve.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve in a bore having a compartment on a first side of the steam admission valve, the steam admission valve being operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder on a second side of the admission valve between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• an operative connection between the piston and the crankshaft that maintains a clearance between the cylinder head and the piston at about 8% or less of the clearance at maximum displacement,
• an exhaust valve mechanism element for opening the exhaust valve that is operatively associated with the exhaust valve so as to exhaust steam from the cylinder through the exhaust valve during a portion of each return stroke of the piston within the cylinder, and
• a member for shutting the exhaust valve proximate an end of each exhaust stroke for reducing compression of residual steam remaining within a clearance,
• wherein the steam admission valve is a duplex poppet valve which further comprises:
• an outer valve element having a tubular sidewall and at one end thereof a first circular valve seat therefor surrounds a steam admission port to the engine cylinder, and
• a core valve element slidably mounted therein for engaging a second circular seat between the core element and the outer valve element to control steam flow therethrough, a valve actuator is the piston or a lifter for raising the outer element from its seat and the duplex valve has an opening to allow steam to flow from a steam supply chamber communicating with the duplex valve into the engine cylinder when the duplex valve is opened by the piston or the lifter.

A steam expander of an engine comprising:

• at least one cylinder, a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• wherein the admission valve is a poppet valve comprising a poppet piston having a cylindrical sidewall slidably and sealingly enclosed within a cylindrical bore that terminates in a valve seat and the poppet piston is yieldably biased toward a closed position against the valve seat in the engine at one end of the bore, the poppet piston having a valve face that extends centrally from the sidewall to form a seal against the seat when the admission valve is closed, and
• a steam supply chamber in the engine communicating between the bore and a steam supply,
• such that with the poppet piston in the closed position steam in the supply chamber is unable to apply an axial force on the poppet piston but when the valve is at least partially open steam from the supply chamber is able to flow into the bore between the face of the poppet piston and the steam expansion chamber to thereby create a pressure differential across the poppet piston that exerts an axial lifting force on the poppet piston which slides the poppet piston open by means of the lifting force of the steam to a more fully open position and
• wherein the poppet piston is connected to a control for establishing the closing time of the poppet piston, said control comprising at least one fluid-containing compartment operatively related to the poppet piston and a metering member for determining the flow of a fluid into or out of the compartment.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve mounted within a bore having a compartment on a first side of the steam admission valve, the steam admission valve being operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder on a second side of the steam admission valve between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• an operative connection between the piston and the crankshaft that maintains a clearance between the cylinder head and the piston at about 8% or less of the clearance at maximum displacement,
• an exhaust valve mechanism element for opening the exhaust valve that is operatively associated with the exhaust valve so as to exhaust steam from the cylinder through the exhaust valve during a portion of each return stroke of the piston within the cylinder, and
• a member for shutting the exhaust valve proximate an end of each exhaust stroke for reducing compression of residual steam remaining within a clearance volume,
• wherein the steam admission valve further comprises a poppet piston valve with a cylindrical sidewall that is slidable to an open position in the bore so as to communicate with a steam chest through an aperture in a sidewall of the bore when the admission valve is open,
• wherein the poppet piston valve has a sealing surface at one end of the cylindrical sidewall of the poppet piston valve, and
• wherein said sealing surface on the poppet piston valve forms a seal against a valve seat which communicates with a port in the steam expansion chamber, such that the steam chest communicates with the valve bore through the aperture in the bore when the poppet piston valve is moved axially off of the seat for admitting steam from the steam chest into the steam expansion chamber of the engine.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve having a face located in a wall of the cylinder head that forms an end of the cylinder so as to confront the piston for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke,
• an exhaust valve mechanism element that holds the exhaust valve open during a substantial part of each exhaust stroke, and
• a member that closes the exhaust valve when the admission valve opens proximate dead center at an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to the closing of the exhaust valve that is able to trap a remaining residual fraction of an initial steam mass,
• wherein an operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at a beginning of said exhaust stroke,
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume, and
• wherein the steam expander is a part of a dual cycle internal combustion steam engine having at least one combustion chamber therein for burning fuel and a combustion exhaust port connected for providing exhaust gasses to fire a heater for steam that is supplied to the steam expansion chamber of the engine and the valves are both actuated by a force applied thereto by piston movement.

A steam expander of an engine comprising:

• at least one cylinder, a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve operatively associated with the cylinder for admitting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an exhaust valve operatively associated with the cylinder for exhausting steam from the steam expansion chamber,
• wherein the admission valve is a poppet valve comprising a poppet piston having a cylindrical sidewall slidably and sealingly enclosed within a cylindrical bore that terminates in a valve seat and the poppet piston is yieldably biased toward a closed position against the valve seat in the engine at one end of the bore, the poppet piston having a valve face that extends centrally from the sidewall to form a seal against the seat when the admission valve is closed,
• a steam supply chamber in the engine communicating between the bore and a steam supply,
• such that with the poppet piston in the closed position steam in the supply chamber is unable to apply an axial force on the poppet piston but when the valve is at least partially open steam from the supply chamber is able to flow into the bore between the face of the poppet piston and the steam expansion chamber to thereby create a pressure differential across the poppet piston that exerts an axial lifting force on the poppet piston which slides the poppet piston open by means of the lifting force of the steam to a more fully open position and
• wherein the bore communicates through a steam admission port in the cylinder head with the steam expansion chamber of the cylinder and the poppet piston is at least partially opened by a member selected from the engine piston, a lifter on the engine piston or on the poppet piston, an electrical solenoid for starting or running the engine and a cam that is operatively connected to the engine.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve located in the cylinder head for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke;
• wherein the exhaust valve is open during a substantial part of each exhaust stroke,
• an exhaust valve mechanism element for closing the exhaust valve when the admission valve opens proximate an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to the closing of the exhaust valve that is able to trap a remaining residual fraction of the initial steam mass which was not exhausted,
• wherein an operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at a beginning of said exhaust stroke,
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume;
• and
• wherein the steam admission valve further comprises,
• a pair of valve elements including an outer admission valve element having a poppet valve face at an end thereof and a sidewall slidably supported in the engine,
• a first valve seat for the poppet valve face surrounding a steam admission port to the engine cylinder,
• a core valve element being slidably mounted in the outer admission valve element for engaging a second valve seat between the core element and the outer admission valve element to control steam flow therethrough, and
• wherein said admission valve mechanism element is the piston or a lifter for opening the admission valve to allow steam to flow from a steam supply into the engine cylinder when the admission valve is opened by the piston or by the lifter.

A steam expander of an engine comprising:

• at least one cylinder having a cylinder head and a piston that is slidably and sealingly mounted in the cylinder and is operatively connected to a crankshaft for imparting rotation to the crankshaft,
• a steam admission valve located in the cylinder head for injecting steam into a steam expansion chamber located in the cylinder between the piston and the cylinder head,
• an admission valve mechanism element for opening the admission valve that admits steam into the cylinder proximate the beginning of a power stroke of the piston,
• an exhaust valve having a valve end face in a wall of the expansion chamber for exhausting steam from the steam expansion chamber during an exhaust stroke,
• an exhaust valve mechanism element that holds the exhaust valve open during a substantial part of each exhaust stroke, and
• a member that closes the exhaust valve when the admission valve opens proximate dead center at an end of each exhaust stroke such that any compression at the end of the exhaust stroke is substantially compression due to the closing of the exhaust valve that is able to trap a remaining residual fraction of an initial steam mass,
• wherein the operative connection between the piston and the crankshaft establishes a clearance between the piston and the cylinder head to be at a minimum during a transition from exhaust to admission and about 8% or less of the clearance at a beginning of said exhaust stroke, and
• wherein a clearance volume of the steam expansion chamber is devoid of an empty recess that contributes substantially to the clearance volume,
• wherein the steam expander is a part of a dual cycle internal combustion steam engine having at least one combustion chamber therein for burning fuel and a combustion exhaust port connected for providing exhaust gasses to fire a heater for steam that is supplied to the steam expansion chamber of the engine and the valves are both actuated by a force applied thereto by piston movement, and
• wherein the dual cycle internal combustion steam engine includes a fixed inward cylinder head within the cylinder, at least one piston is slidably and sealingly mounted with respect to both the cylinder and the inward cylinder head, and the steam, inlet and exhaust valves are disposed in a side-by-side relationship within the inward cylinder head.