Exhaust gas temperature control

A transport refrigeration unit (TRU), comprising:

• an engine system comprising an inlet to mix fuel and air and a TRU engine to combust the mixed fuel and air to produce exhaust gas;
• an exhaust system through which the exhaust gas is flown and comprising a catalyst operable in a temperature range to catalyze the exhaust gas;
• temperature sensors respectively disposed to sense exhaust gas temperatures upstream of and downstream from the catalyst;
• first, second and third valves, each of which is proportionally controllable to moderate amounts of air provided to the TRU engine, fuel provided to the TRU engine and air provided to the catalyst, respectively, the first and second valve being disposed in parallel upstream from the TRU engine;
• and
• a controller coupled to the temperature sensors and each of the first, second and third valves and configured to:
• compare sensed exhaust gas temperatures with the temperature range, and
• issue first, second and third proportional signals to each of the first, second and third valves, respectively, in accordance with results of the comparison.

A method of operating an exhaust gas system for a transport refrigeration unit (TRU) engine, the method comprising:

• arranging first and second proportionally controllable valves in parallel upstream from the TRU engine, the first and second proportionally controllable valves being configured to moderate amounts of air and fuel provided to the TRU engine, respectively;
• arranging a third proportionally controllable valve upstream from a catalyst, the third proportionally controllable valve being configured to moderate an amount of air provided to the catalyst;
• sensing exhaust gas temperatures proximate to the catalyst which is operable in a temperature range;
• comparing the sensed exhaust gas temperatures with the temperature range;
• and
• issuing first, second and third proportional signals to each of the first, second and third proportionally controllable valves, respectively, to moderate the amounts of air provided to the TRU engine, fuel provided to the TRU engine and air provided to the catalyst respectively, in accordance with results of the comparison.