Development of a highly compact steam generator

Conventional steam generators are the largest components in steam power plant, and add considerably to the physical size of gas turbine based combined cycle and combined heat and power plant. Availability of compact steam generators capable of operating at high pressures would make heat recovery from engine and turbine exhausts attractive in a wider range of applications. The advantages of small size are particularly marked in mobile systems. This paper describes the design and preliminary testing of a steam boiler suitable for use in a steam engine powered car. The boiler has a nominal rating (based on water entering at 100 °C when producing steam at 40 bar, 400 °C) of 135 kW. The volume of the boiler (excluding the burner) is approximately 0.06 m3, giving a volumetric power density of over 2 MW/m3. Mechanical design of the boiler is such that the operating temperature and pressure may be increased to improve overall system performance. The influence of various parameters on the performance and stable operation of the boiler is examined. It is shown that the concepts discussed could be applied to heat recovery steam generators, thus permitting economical heat recovery from internal combustion engines and micro gas turbines.