초록 ▼

For an unmanned aerial vehicle (UAV) engine, an exhaust gas temperature control method is provided during operation of the UAV engine to protect exhaust components, particularly lightweight aluminium components, from overheating or melting. The engine is operated with a leaner than stoichiometric ai

For an unmanned aerial vehicle (UAV) engine, an exhaust gas temperature control method is provided during operation of the UAV engine to protect exhaust components, particularly lightweight aluminium components, from overheating or melting. The engine is operated with a leaner than stoichiometric air-fuel ratio during low or part engine load conditions. Transition to a richer than stoichiometric air-fuel ratio is made as engine load or engine speed, or both engine load and engine speed, increase(s). At sufficiently low engine loads, the air-fuel ratio can be maintained in a lean ratio region. As demand on the engine causes engine speed and load to increase, the amount of excess air available reduces. The ability to operate lean is reduced and the exhaust gas temperature increases as the mixture becomes richer. In order to obtain the demand power, and keep exhaust temperature below an exhaust gas temperature limit, the air-fuel ratio is transitioned to a richer than stoichiometric region. As engine load and speed demand decreases, the air-fuel ratio can be transitioned back to a leaner region.

대표청구항 ▼

1. A method of controlling exhaust gas temperature of an exhaust system of an unmanned aerial vehicle (UAV) engine during operation, the UAV engine having an engine management system for controlling the operation of the UAV engine, the method including the engine management system controlling the en

1. A method of controlling exhaust gas temperature of an exhaust system of an unmanned aerial vehicle (UAV) engine during operation, the UAV engine having an engine management system for controlling the operation of the UAV engine, the method including the engine management system controlling the engine to operate with a leaner than stoichiometric air-fuel ratio during low or part engine load conditions, and controlling the exhaust gas temperature to be no higher than a threshold exhaust gas temperature by transitioning the air-fuel ratio to a richer than stoichiometric air-fuel ratio based on a measured, demanded or required increase in engine load or engine speed, or both engine load and engine speed. 2. A method as claimed in claim 1, including the UAV engine utilising direct injection. 3. A method as claimed in claim 2, including the UAV engine utilising dual fluid direct injection. 4. A method as claimed in claim 3, the use of the dual fluid direct injection including injecting heavy fuel. 5. A method as claimed in claim 4, whereby injecting the heavy fuel includes injecting jet propellant (JP). 6. A method as claimed in claim 5, wherein the jet propellant is JP5 or JP8. 7. A method as claimed in claim 2, including, when operating the UAV engine at the leaner than stoichiometric air-fuel ratio, injecting a stratified fuel delivery into at least one combustion chamber of the UAV engine, the stratified fuel delivery including a portion at or close to stoichiometric air-fuel ratio. 8. A method as claimed in claim 2, including providing multiple injection events per cycle per cylinder. 9. A method as claimed in claim 1, including cooling exhaust gas temperature using air cooling at part or low engine load when operating the UAV engine at the lean air-fuel ratio, and cooling exhaust gas temperature at increased or high engine load by transitioning the air-fuel ratio to the richer than stoichiometric ratio. 10. A method as claimed in claim 1, including determining engine load demand, and transitioning air-fuel ratio based on that demand. 11. A method as claimed in claim 10, including determining the engine load demand from one or more operator inputs. 12. A method as claimed in claim 11, the one or more operator inputs including an indication of throttle position or the engine speed requested. 13. A method as claimed in claim 1, including controlling transition between leaner than stoichiometric and richer than stoichiometric air fuel ratios based on exhaust gas temperature over a predefined range or ranges of engine speed or engine load, or both engine speed and engine load. 14. A method as claimed in claim 13, including utilising a look up table or algorithm using engine speed or engine load demand to determine a required said air-fuel ratio to maintain the exhaust gas temperature below a desired value or within a desired temperature range. 15. A method as claimed in claim 1, including determining a temperature value relating to the exhaust gas temperature, and using that determined temperature value to transition the air-fuel ratio towards a richer air-fuel ratio to reduce the exhaust gas temperature, maintain exhaust gas temperature at a desired level or slow down the rate of increase of exhaust gas temperature. 16. A method as claimed in claim 15, including preventing exhaust gas temperature exceeding the threshold temperature by richening the air-fuel ratio. 17. A UAV engine controlled according to the method of claim 1. 18. A method as claimed in claim 1, wherein the air-fuel ratio is varied as a function of exhaust gas temperature by feedback whereby rate of increase in the air-fuel ratio is reduced or stopped as detected exhaust gas temperature reduces with richening air-fuel ratio. 19. A method as claimed in claim 18, whereby the rate of increase in air-fuel ratio is reduced or stopped to control the exhaust gas temperature to be no higher than the threshold value or within a required band of air-fuel ratio.