Heat engine

A heat engine comprising:

• a compressor comprising:
• a compression chamber;
• and
• a first positive displacement member reciprocable within the compression chamber;
• an expander comprising:
• an expansion chamber;
• and
• a second positive displacement member reciprocable within the expansion chamber;
• a first conduit fluidly coupling an outlet of the compressor to an inlet of the expander;
• a second conduit fluidly coupling an outlet of the expander to an inlet of the compressor;
• a working fluid comprising a diluent;
• a reactor in which first and second reactants in the working fluid can react with each other, the reactor arranged in the first conduit between the compressor and the expander;
• and
• a condenser arranged in the second conduit between the expander and the compressor, the condenser receiving the working fluid having a pre-condenser concentration of the diluent, the condenser for condensing a gas in the working fluid into a condensate, the gas being a combustion product from a reaction of the first and second reactants, the condenser comprising a drainage line for draining the condensate from the condenser, and the remaining working fluid flowing from the condenser having a post-condenser concentration of the diluent that is greater than the pre-condenser concentration;
• wherein the first and second positive displacement members are of a low friction piston design;
• wherein the diluent operates in a closed loop in the heat engine;
• wherein the pre-condenser concentration of the diluent in the working fluid is at least 5% by volume;
• wherein the diluent has a ratio of specific heats which is at least 1.4;
• and
• wherein the diluent is selected from the group consisting of Ar, He, Ne, Kr, and Xe.