Operation of transport refrigeration systems to prevent engine stall and overload
The performance of a transport refrigeration system having a transport refrigeration unit powered by a diesel engine is optimized by matching a capacity output of the transport refrigeration unit to an available shaft power of the diesel engine.
1. A method for controlling the performance of a transport refrigeration system having a transport refrigeration unit powered by an engine, comprising matching a capacity output of the transport refrigeration unit to an available shaft power of the engine; the method further comprising:
monitoring an operating engine load of the engine;
monitoring an operating engine speed of the engine;
operating the transport refrigeration system at the capacity output necessary to meet a current refrigeration demand load so as long as both the operating engine load of the engine is not at or above a predetermined maximum value and the operating engine speed of the engine is not below a predetermined engine operating speed; and
reducing the cooling capacity output of the refrigeration unit to a non-zero cooling capacity by adjusting a flow of refrigerant to a compressor when the operating engine load of the engine is at or above the predetermined maximum value and an operating engine speed of the engine is less than the predetermined engine operating speed.
2. The method of claim 1 , further comprising operating the transport refrigeration system at the capacity output necessary to meet the current refrigeration demand load so as long as both the operating engine load of the engine is not at a second predetermined maximum value and the operating engine speed of the engine is not below a second predetermined engine operating speed.
3. The method of claim 1 , wherein the predetermined maximum value is 100%.
4. The method of claim 1 , wherein the predetermined maximum value is 90%.
5. The method of claim 1 , wherein the predetermined engine operating speed is 98% of a target engine operating speed.
6. The method of claim 2 , wherein the second predetermined maximum value is 85%.
7. The method of claim 2 , wherein the second predetermined engine operating speed is 98% of a target engine operating speed.
8. The method of claim 2 , wherein the predetermined maximum value and the second predetermined maximum value are the same.
9. The method of claim 2 , wherein the predetermined maximum value and the second predetermined maximum value are different.
10. The method of claim 2 , wherein the predetermined engine operating speed and the second predetermined engine operating speed are the same.
11. The method of claim 2 , wherein the predetermined engine operating speed and the second predetermined engine operating speed are different.
12. The method of claim 1 wherein the compressor is driven by the engine.
13. The method of claim 12 wherein the engine directly drives the compressor.
14. The method of claim 12 wherein the engine drives an electric generator for generating electrical power to the compressor.
15. The method of claim 1 wherein the engine is a diesel engine.
16. The method of claim 1 wherein the predetermined engine operating speed comprises a predetermined percentage of a target engine operating speed.
17. The method of claim 1 wherein the operating engine load of the engine is indicated by a fuel flow.
18. The method of claim 1 wherein the operating engine speed of the engine is indicated by RPM.
19. The method of claim 1 wherein reducing the cooling capacity output of the refrigeration unit comprises adjusting an opening of a suction modulation valve to adjust a flow of refrigerant to a suction inlet of the compressor.
20. The method of claim 1 wherein reducing the cooling capacity output of the refrigeration unit to the non-zero cooling capacity comprises running the compressor.
21. The method of claim 1 wherein the predetermined maximum value being dependent on an operating mode of the engine.