Stoddard engine

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Equilibrium / Non-equilibrium

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System properties

Note: Conjugate variables in italics

Functions of state
Property diagrams Intensive and extensive properties
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Work Heat

Material properties

Property databases

Specific heat capacity

c=

$T$	$\partial S$
$N$	$\partial T$

Compressibility

\beta =-

$1$	$\partial V$
$V$	$\partial p$

Thermal expansion

\alpha =

$1$	$\partial V$
$V$	$\partial T$

Equations

Potentials

Internal energy
$U(S,V)$
Enthalpy
$H(S,p)=U+pV$
Helmholtz free energy
$A(T,V)=U-TS$
Gibbs free energy
$G(T,p)=H-TS$

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Scientists

Book:Thermodynamics

Elliott J. Stoddard invented and patented two versions of the Stoddard engine, the first in 1919 and the second in 1933. The general engine classification is an external combustion engine with valves and single-phase gaseous working fluid (i.e. a "hot air engine"). The internal working fluid was originally air, although in modern versions, other gases such as helium or hydrogen may be used.

One potential thermodynamic advantage of using valves is to minimize the adverse effects of "unswept volume" in the heat exchangers (sometimes called "dead volume"), which is known to reduce engine efficiency and power output in the valveless Stirling engine.

The 1919 Stoddard engine

The generalized thermodynamic processes of the 1919 Stoddard cycle are:^[1]

Adiabatic compression
Isobaric heat-addition
Adiabatic expansion
Isobaric heat-removal

The engine design in the patented was using a scotch yoke.

The 1933 Stoddard engine

In the 1933 design,^[2] Stoddard reduced the internal volume of the heat exchangers maintaining the same generalized thermodynamic processes as the 1919 cycle.

Gallery

Stoddard engine diagrams

The 1919 Stoddard Engine

The 1933 Stoddard Engine

References

Weblinks

Wikimedia Commons has media related to Stoddard engine.

Thermodynamic cycles

External combustion

Without phase change (hot air engines)	Bell Coleman Brayton / Joule Carnot Ericsson Stirling Stirling (pseudo / adiabatic) Stoddard

With phase change	Kalina Hygroscopic Rankine (Organic Rankine) Regenerative

Internal combustion

Mixed

Refrigeration

Uncategorized

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