No abstract

An expert system is developed for engineering design based on an object-oriented knowledge representation concept. The design process is understood as determining design variables and their relationships which compose the design model. The design model is represented as a network in the computer system using the object-oriented knowledge representation. The system built with the above concept provides the following abilities: (1) flexible model building and easy modification, (2) effective diagnosis of the design process, (3) supporting method for redesign, (4) a hybrid function with numerical computations and graphics, and (5) applicability for various design problems. Finally, it is applied to the basic design of a ship.

The objective of this paper is to develop a computer‐aided optimal planning method for designing a marine heat and power generation plant which is composed of combining Diesel and turbogenerators, an exhaust gas economizer, auxiliary boilers and so forth. As there exist many alternative combinations concerning generators and boilers in constructing the abovementioned plant, it is important to determine the plant construction properly by selecting total numbers and scales of respective generators and boilers so as to optimize the long‐term economy of the plant. In this planning method, several design conditions are first set which are necessary for the planning of the objective plant, i.e. several patterns of ship's operational condition are set first, and both energy demands and steam output from an exhaust gas economizer are estimated for each pattern. Next, setting an alternative plant composed of combining generators and boilers adequately, the optimal operational policy for each pattern is determined by minimizing the fuel cost under several physical constraints based on linear and quadratic programming methods. Considering the results obtained above hierarchically, annual capital and operational costs of each plant are calculated, and the best plant construction is lastly determined by comparing the economy of all alternative plants. A numerical study has been carried out on a plant of a high speed container ship actually planned, and it is ascertained that to find the best construction of the plant the optimal planning method proposed here is advantageous compared with the conventional trial and error method.

The influence of fuel cost on the operation is investigated for a gas turbine-waste heat boiler cogeneration plant by an optimal operational planning method. A planning method is first presented by which the operational policy of each piece of constituent equipment is determined so as to minimize the operational cost. Then, a case study is performed for a cogeneration plant used for district heating and cooling. Through the study, it is made clear how the optimal operational policy and the economic or energy conservative properties are influenced by the costs of purchased electric power and natural gas. It is also shown that the optimal operational policy is superior in economy as compared with other conventional ones.

A hybrid type approach to plant layout design is presented using a constraint-directed search procedure and a mathematical optimization technique. In layout design, a plant must be arranged to satisfy spatial constraints imposed by its components. In our approach the whole space of a plant building is divided into the finite compartments with a modular size in order to separate the description of the layout into the combinatorial part and the sizing part. The approach consists of two steps. In the first step, a constraint-directed search procedure is applied to find a combinatorial solution among plant components so as to satisfy the spatial layout conditions. In the second step, an optimization technique is applied to determine the actual dimensions of components so as to minimize a measure of an overall size of a plant building considering size of components. The approach is implemented with an object-oriented programming environment and the system can automatically produce a layout from the declarative representation of layout conditions. Finally, the approach has been applied to the design of a nuclear power plant in order to check its validity and effectiveness.