Stirling engine instability detection and prevention

A method of detecting instabilities of a Stirling engine of a domestic combined heat and power dchp unit, the dchp unit having a combustible fuel supply, being capable of generating a heat output, and having a generator for producing an electrical power output, the Stirling engine having an engine head and a burner to input heat energy into the engine head to drive a reciprocating member, the method comprising:

• receiving a signal from the generator of the dchp unit;
• carrying out a Fourier Transform on that signal;
• monitoring the Fourier Transform so as to identify the presence of artefacts within the Fourier Transform which are indicative of existing or developing instabilities in the Stirling engine;
• and
• responding to the identified presence of artefacts by implementing action on the Stirling engine to correct the instabilities.

An instability detection apparatus for detecting instabilities within an engine of a domestic combined heat and power, dchp, unit, the dchp unit having a combustible fuel supply and a generator for producing an electrical power output, the apparatus being arranged to receive a signal from the generator of the dchp, to carry out a Fourier Transform on that signal, and to monitor the Fourier Transform so as to identify the presence of artefacts within the Fourier Transform which are indicative of existing or developing instabilities within the dchp unit, the instability detection apparatus further comprising:

• a dchp unit having:
• an engine with a reciprocating member;
• a combustible fuel supply;
• a heat output;
• and
• a generator for generating an electrical power output;
• a stroke length detector arranged to provide a stroke length detection output;
• and
• a system controller arranged to receive as a first input from the instability detection apparatus, an indication of the presence of artefacts in the Fourier Transform of the generator output, to receive as a second input from the stroke length indicator the said stroke length detection output;
• and to control the dchp unit so as to reduce the stroke length of the reciprocating member in dependence upon the first input thereto, the second input thereto, or both.

An instability detection apparatus for detecting instabilities within an engine of a domestic combined heat and power unit, the dchp unit having a combustible fuel supply and a generator for producing an electrical power output, the apparatus being arranged to receive a signal from the generator of the dchp, to carry out a Fourier Transform on that signal, and to monitor the Fourier Transform so as to identify the presence of artefacts within the Fourier Transform which are indicative of existing or developing instabilities within the dchp unit, the instability detection apparatus further comprising:

• a dchp unit having a combustible fuel supply;
• a generator for producing an electrical power output;
• a heat output;
• and
• a controller arranged to receive an output from the instability detection apparatus indicative of the presence of the said artefacts in the Fourier Transform, the controller being configured to control the dchp engine to reduce the presence of instabilities when the said output of the apparatus indicates the presence of the artefacts in the Fourier Transform.