Automatic Control Example

Combustion Control System (CCS) software can include automatic control functions to increase system reliability, reduce operator workload and enhance the safety of system operation.

The Main Combustor Auto Start function, is an example of an automatic control function that is commonly incorporated into systems developed by Bergmans Mechatronics LLC (BML). The objectives of this function are two-fold: i) to safely and reliably start the main combustion chamber of the device under test; and, ii) to perform an automatic shutdown of the device under test in the event of a anomaly.

The Auto Start function achieves these objectives by monitoring a key combustion chamber parameter such as chamber pressure or temperature and ensuring that the parameter remains within a predefined envelop during the start process.

Using combustor temperature an an example, the Auto Start function operates as follows. With reference to the plot at right, upon detecting stable igniter operation at the origin of the time axis (t=0), the main run valves of the combustion system are opened and fuel and oxygen begin flowing into combustor.  Three possible outcomes and the corresponding response of the Auto Start function to this event are as follows.

1. Nominal Combustor Ignition - The combustor temperature rises above the user-defined "Combustor Ignition Threshold Temperature" and stabilizes below a user-defined "Maximum Combustor Temperature".  Normal steady state operation of the combustion system then begins.


2. Combustor Ignition Failure - The combustor temperature does not reach the "Combustor Ignition Threshold Temperature" within the user-defined "Maximum Time to Threshold Temperature". In this case, an abort sequence is automatically executed to terminate the test and return the test stand to a safe state.


3. High Combustor Temperature - The combustor temperature exceeds the "Maximum Combustor Temperature" upon opening the run valves. An example of a condition causing this case is an improper ratio of oxygen to fuel flowrates. To avoid possible damage from excessively high temperatures, an abort sequence is automatically executed and the test is terminated to return the test stand to a safe state.

In some combustion applications, beginning full main fuel and oxygen flow upon detecting stable igniter operation can produce undesirable results. To accommodate such situations, BML also has experience with developing more complex start algorithms that include features such as user-defined delay times for main fuel and oxygen flow and pre-programmed ramping of main flow proportional valves.

Main Combustion Auto Start Function