AME Unit 10 Q4 – Answer

(a) Block Diagram:

Here’s a block diagram of a split-range control system for jacket water temperature:

Components and Functions:

  • Temperature Sensor: Measures the jacket water temperature (T_jacket).
  • Controller (Split-Range): Receives the temperature signal and compares it to two setpoints:
    • Setpoint (Low): Minimum desired temperature (T_min).
    • Setpoint (High): Maximum desired temperature (T_max).
    • Calculates separate errors for each setpoint.
    • Uses separate gains for each error (Gain_Low, Gain_High).
    • Generates two output signals based on the errors and gains.
  • Cooling Valve: Opens or closes based on the low-range output signal to regulate cooling water flow.
  • Heating Valve (Optional): Opens or closes based on the high-range output signal to regulate heating water flow (if needed).
  • Bypass Valve (Optional): Allows bypassing the cooler or heater when unnecessary.

(b) System Operation:

  1. Temperature Measurement: The sensor continuously measures the T_jacket.
  2. Error Calculation:
    • The controller compares T_jacket with both setpoints (T_min and T_max).
    • If T_jacket is below T_min, a positive error occurs for the low-range control.
    • If T_jacket is above T_max, a positive error occurs for the high-range control.
    • If T_jacket is within the desired range (T_min <= T_jacket <= T_max), both errors are zero.
  1. Output Signal Generation:
    • The controller uses separate gains (Gain_Low and Gain_High) to amplify the calculated errors.
    • The low-range output signal controls the cooling valve.
      • Higher error (T_jacket below T_min) opens the valve more for increased cooling.
      • Lower error (T_jacket closer to T_min) closes the valve partially.
    • The high-range output signal controls the heating valve (if present).
      • Higher error (T_jacket above T_max) opens the valve more for increased heating.
      • Lower error (T_jacket closer to T_max) closes the valve partially.
    • The bypass valve might be used to avoid unnecessary operation of the cooler or heater when T_jacket is within the desired range.
  1. System Response:
    • The controlled valve openings adjust the cooling or heating water flow, affecting T_jacket.
    • The system continuously monitors and adjusts to maintain T_jacket within the desired range despite disturbances.

Additional Notes:

  • The specific gains and setpoints are chosen based on engine requirements and operating conditions.
  • This is a simplified explanation, and actual systems may have additional features and complexities.