Control method for variable geometry exhaust turbine
A method of setting actuator position of a variable geometry turbine linked to drive a compressor for a compression ignition engine using exhaust gas recirculation. The method includes detecting an engine transient event; determining current mass air flow through the compressor and exhaust temperature; resetting variable geometry turbine position to maximize mass air flow through the compressor; adding the maximum allowable quantity of fuel; determining exhaust temperature increase; adjusting exhaust pressure to allow an increase in mass air flow and exhaust temperature; and returning to the resetting step until a limit is reached.
1. A method of setting flow through variable geometry turbine linked to drive a compressor into an intake manifold for a compression ignition engine, the method comprising the steps of:
a) detecting engine operational transient events demanding increased power output;
b) from current mass air flow through the compressor, exhaust temperature and intake manifold pressure, selecting a predetermined exhaust back pressure target setpoint to maximize mass air flow and minimize pumping loss;
c) obtaining current exhaust back pressure;
d) determining the difference between current exhaust back pressure and the exhaust back pressure target setpoint;
e) varying flow through the variable geometry turbine to eliminate the difference;
f) increasing fuel flow to a maximum allowable rate; and
g) returning to step b) until the engine steady state operating conditions exist or a predetermined limit condition is met.
2. The method of claim 1 wherein step e) is modified to limit variation to maintain a minimum level of exhaust gas recirculation.
3. The method of claim 2 wherein step e) includes adjusting vane position in the variable geometry turbine.