Tham khảo tài liệu 'advances in gas turbine technology part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 50 Advances in Gas Turbine Technology In the marine low-speed Diesel engines another portion of energy that can be used along with the exhaust gas energy is a huge amount of so-called waste heat of relatively low temperature. In the low-speed engines the waste heat comprises the following components with their proportions to the heat delivered to the engine in fuel - heat in the scavenge air cooler 17-20 of an approximate temperature of about 2000C - heat in the lubricating oil cooler 3-5 of an approximate temperature of about 500 . - heat in the jacket water cooler 5-6 of the temperature of an order of 1000C. This shows that the amount of the waste heat that remains for our disposal is equal to about 25-30 of the heat delivered in fuel. Part of this heat can be used in the combined circuit with the Diesel engine. Energy evaluation of the combined propulsion system The adopted concept of the combined ship propulsion system requires energy evaluation Fig. 4. Formulas defining the system efficiency are derived on the basis of the adopted scheme. The power of the combined propulsion system is determined by summing up individual powers of system components the main engine the power gas turbine and the steam turbine N . Nn NrT NST 1 combi D PT ST hence the efficiency of the combined system is - Ncombi Np Nst i n I 1 I mfD Wu lD Nd Nd J 2 and the specific fuel consumption is b Nj N g kWh 3 1 N N where qD beD- is the efficiency and specific fuel consumption of the main engine. Relations 2 and 3 show that each additional power in the propulsion system increases the system efficiency and consequently decreases the fuel consumption. And the higher the additional power achieved from the utilisation of the heat in the exhaust gas leaving the main engine the lower the specific fuel consumption. Therefore the maximal available power levels are to be achieved from both the power gas turbine and the steam turbine. The power of the steam turbine mainly depends on the live .
