Dynamic engine parameters, Powerstroke lenght-Humphrey cycle

[OneCycle]

Suppose you were given the dynamic control of engine parameters such as the powerstroke lenght, variable compression ratio and total compression volume. It is simple to state the conditions for Max power. What is much more difficult is how to optomize the efficiency for low and mid range power.
I know there are not enough details to the question, but it is not a hypothetical one. It is not a piston engine but more resembling (at least in operation) a positive discplacement turbine.
And yes it uses the Brayton cycle but can also break up the CP burn into an intermitant CV Humphrey cycle.
I am particularly interested in knowledge about localized rich flame propagation in a general lean environment, and thoughts about emission results in that environment.

 

[PJGD]

A poorly expressed question, but nevertheless, it sounds as if you are contemplating the Humphrey Pump which was typically used for municipal water supply almost a century ago. Usually they ran on methane or coal gas, and so I assume your question pertains to a gaseous fuel?

Your last paragraph suggests that you are seeking stratified charge, which is not always easy to create reliably, but there are several stratified natural gas engines out in the parc.

In general, stratified charge combustion will be lower in NOx than stoichiometric homogeneous charge, but there will still be the rich regions that will produce high temperatures and thus NOx. What you should consider, is a lean HCCI combustion system, which should give you virtually no NOx or PM. It will detract from the basic simplicity of the Humphrey cycle, since you will need EGR and a pressure charging system (a supercharger) to achieve the specific power of the naturally aspirated version.

PJGD