Transportation refrigeration system comprising a refrigeration unit and a diesel engine

A transport refrigeration system including a refrigeration unit comprising:

• a diesel engine having an exhaust system for discharging engine exhaust from the diesel engine;
• an exhaust treatment unit disposed in the diesel engine exhaust system, the exhaust treatment unit including a diesel oxidation catalyst and a diesel particulate filter;
• an air control valve configured to control a quantity of air provided to the diesel engine from an air supply fluidly coupled to the diesel engine;
• and
• a controller operably coupled to the air control valve, wherein the controller is configured to operate the system in one of a primary regeneration mode and a secondary regeneration mode in response to a temperature condition monitored within the exhaust treatment unit, wherein the temperature condition is a rate of temperature change of the exhaust gas upstream from the diesel particulate filter and the secondary regeneration mode is used if the rate of temperature change satisfies a predetermined condition, wherein in the secondary regeneration mode, the diesel particulate filter is regenerated using only the air control valve.