The dynamic characteristics of diesel engines have been examined using mathematical models and simulations. The mathematical approach uses sampled data analysis and small perturbation techniques in conjunction with frequency response methods. Extensive test work on a three cylinder compression ignition engine has shown that the sampled data model is valid for stability prediction. A method of plotting the experimental results is suggested which has the advantage of generality and as it takes into account both engine and load torque speed characteristics gives a unique plot for all engines. It shows clearly how the stability of the control loop can depend on the number of cylinders and the engine speed. Two simulations of engines are presented - an analogue computer simulation which is restricted in the form presented to a three cylinder engine, and a digital computer simulation which can be used for any naturally aspirated engine with a variety of governor characteristics. Both simulations accurately predict engine performance. The experimental methods used involve the use of electro- hydraulic systems and test techniques. These are shown to have great advantages in providing the appropriate inputs and loading conditions.
|Date of Award||1972|