Im just collecting some data here,
http://www.engineeringtoolbox.com/steam-vapor-enthalpy-d_160.htmlhttp://www.auto-ware.com/combust_bytes/eng_sci.htmhttp://steamautomobile.com/phorum5214/read.php?1,15817http://steamautomobile.com/phorum5214/read.php?1,10574,page=2http://steamautomobile.com/phorum5214/read.php?1,14903The last three links there are some of my threads on the SACA Forum, I am a member of the Steam Automoble Club of America.
Since the 4cycle steam engine is not a rankine cycle engine, calculating thermal efficiency is not very straight forward. Im making these note's here because it will assist me in calculating projected engine/expander efficiency.
*** I also welcome any help from others, who are interested in this type of steam engine.***
We already know it works, (4cycle flash steam engine) but it is disired to know exactly why and how it works.
The following are two links of interest, the second link is the most relevant, qoutes from it are provided below.
http://en.wikipedia.org/wiki/Thermal_efficiencyhttp://en.wikipedia.org/wiki/EnthalpyThe total enthalpy, H, of a system cannot be measured directly. Thus, change in enthalpy, ΔH, is a more useful value than H itself. The value of ΔH is positive in endothermic reactions. ΔH of a system is equal to the sum of non-mechanical work done on it and the heat supplied to it. For quasistatic processes under constant pressure, ΔH is equal to the change in the internal energy of the system, plus the work that the system has done on its surroundings.[1]
The main reason this quote is relevant, is because of the discovery of the "Heat of Rejection" factor, and using "heat of rejection" as a framework, the underlaying thermodynamic mechanisms may become more clear.
Here's another example
Heats of Reaction
The total enthalpy of a system cannot be measured directly; the enthalpy change of a system is measured instead. Enthalpy change is defined by the following equation:
ΔH = Hfinal − Hinitial
where
ΔH is the enthalpy change
Hfinal is the final enthalpy of the system, expressed in joules. In a chemical reaction, Hfinal is the enthalpy of the products.
Hinitial is the initial enthalpy of the system, expressed in joules. In a chemical reaction, Hinitial is the enthalpy of the reactants.
For an exothermic reaction at constant pressure, the system's change in enthalpy equals the energy released in the reaction, including the energy retained in the system and lost through expansion against its surroundings. In a similar manner, for an endothermic reaction, the system's change in enthalpy is equal to the energy absorbed in the reaction, including the energy lost by the system and gained from compression from its surroundings. A relatively easy way to determine whether or not a reaction is exothermic or endothermic is to determine the sign of ΔH. If ΔH is positive, the reaction is endothermic, that is heat is absorbed by the system due to the products of the reaction having a greater enthalpy than the reactants. On the other hand if ΔH is negative, the reaction is exothermic, that is the overall decrease in enthalpy is achieved by the generation of heat.
Although enthalpy is commonly used in engineering and science, it is impossible to measure directly, as enthalpy has no datum (reference point). Therefore enthalpy can only accurately be used in a closed system. However, few real-world applications exist in closed isolation, and it is for this reason that two or more closed systems cannot be compared using enthalpy as a basis, although sometimes this is done erroneously.
Specific Enthalpy
Specific enthalpy (h) is defined as h = u + Pn, where u is the specific internal energy (Btu/lbm)
of the system being studied, P is the pressure of the system (lbf/ft2), and n is the specific volume
(ft3/lbm) of the system. Enthalpy is usually used in connection with an "open" system problem
in thermodynamics. Enthalpy is a property of a substance, like pressure, temperature, and
volume, but it cannot be measured directly. Normally, the enthalpy of a substance is given with
respect to some reference value. For example, the specific enthalpy of water or steam is given
using the reference that the specific enthalpy of water is zero at .01°C and normal atmospheric
pressure. The fact that the absolute value of specific enthalpy is unknown is not a problem,
however, because it is the change in specific enthalpy (Dh) and not the absolute value that is
important in practical problems. Steam tables include values of enthalpy as part of the
information tabulated.
Now this is where things get interesting.
http://www.flashsteam.com/Heat.htmThe injector has a internal pressure of 1784.4psi and 620°f, the discharged water, has 638.3btu/lb. The percentage of flash steam produced is 61.7% The percentage of heat transfer is 93.8%
That's nearly 100% heat transfer rate, and this is not good.
Remember the engine did not turn over under these conditions. All the heat from the flash steam was transferred into the engine block. None of it was rejected, as the result there was no positive pressure produced in the cylinder.
But, at a block temp of 180°f(147.9btu/lb) the engine turned over, there was positive pressure developed from the injected water, since heat was conserved or rejected by the system.
In this case, the equation yielded 50% flash steam discharge and 77% heat transfer rate, that's 20% less (heat transfer) than with the cold engine block.
It may be noticed that as heat transfer decreases. That the resulting steam produced, performs more work. This occurs with less percentage of flash steam than would occur at colder temperatures according to the formula.
This is what is meant by Heat Of Rejection.
It is important to keep in mind, that only the "power-stroke" is being considered here. The goal is to effectively create a "power-pulse" which means there is expansion of the injected water, while a simultaneous rise in the "pressure in the cylinder" is occuring. Piston cylinder pressures to 1500psi may be achieved.(with 600°f superheating)
, for an endothermic reaction, the system's change in enthalpy is equal to the energy absorbed in the reaction, including the energy lost by the system and gained from compression from its surroundings.
This leads me to believe the reaction is actually a "Polytropic" expansion process. Both pressure rise and expansion of the injected water are occuring. This is very clearly observed when the parameters defined by Heat of Rejection are trending toward endothermic (hence de-superheating). In this case there are a total of 3 possible heat inputs that must be considered at piston TDC on a power-stroke.
A. The injected water is near 400°f, and is under a hydrostatic pressure of about 2000psi before/during injection.
B. The upper third of the engine cylinder, cylinder head, and injector nozzle body are heated by means of heat transfer fluid to appox 400°f. These fluid passages are insulated on there external surfaces.
C. Low pressure 525°f to 600°f superheated steam is aspired into the engine cylinder and fully compressed at approx 9 to 1 compression ratio,(captured) just as the beginning of the power-stroke event occurs, the piston begins downward movement, expansion begins.
"A" determines the quantity of "expansion factor" of the system.(1600 to 1 water expansion ratio) depending on the programable lift setting(mechanical) in the injector valve and hydrostatic pressure of the injection system, combined with desired angular setting and cutoff(which are digital control in this case, im thinking about 8% to a max cutoff, of about 25%, and 5° to 0° admission advance setting).
"B" and "C" are Heat of Rejection factors with "C" being the primary factor, "B" is used for engine startup and may be disengaged.
When the engine(4 cycle steam) aspires superheated steam and compresses it, its best described as a conservation process, the aspired saturated steam (before superheating) is able to retain its latent heat energy when it is re-used by the engine cycle.
Jeremy
