Influence of Exhaust Temperature and Flow Velocity of Marine Diesel Engines on Exhaust Gas Boiler Heat Transfer Performance

Abstract

Due to the relatively cheap price of diesel, most Marine engines use diesel as Marine fuel, but its emissions contain a lot of carbon. To reduce carbon emissions, International Maritime Organization (IMO) has established an Energy Efficiency Design Index (EEDI) and Energy Efficiency Existing-Ship Index (EEXI). Currently, a popular way is to reduce EEDI by optimizing the heat transfer performance of exhaust gas boilers on new ships, but there is little research on the EEXI index of existing ships. For operating ships, the thermal conductivity of exhaust gas boiler materials and other parameters has been fixed, so the main factors affecting the heat transfer coefficient of the exhaust gas boiler are exhaust gas temperature and flow velocity. Therefore, this paper studies the influence of engine exhaust temperature and flow rate on boiler heat transfer coefficients and optimizes it to achieve the EEXI value required by IMO. Firstly, based on the conservation of mass and energy as the basic equation, a heat exchange model of the exhaust gas boiler is established by using the hybrid modeling method and lumped parameter method. Secondly, for the given boiler, since other parameters are basically unchanged, the input temperature and flow rate of the model are changed by the control variable method, and the temperature of the boiler outlet is simulated by the test algorithm. Through the simulation operation of an Aalborg OC-type boiler, the results show that when the exhaust gas flow velocity is 15 m/s, 17.2 m/s, 22.4 m/s and 25 m/s, respectively, the heat transfer coefficient at each flow velocity increases first and then slowly decreases with the increase of temperature, and there is an optimal temperature at each velocity, which is 230 °C, 227 °C, 225 °C and 224 °C, respectively. The innovation of this study lies in the research on the inlet temperature and flow rate of the exhaust gas boiler of the operating ship based on the EEXI, and the relevant results are obtained, which provides theoretical guidance for the operation management of the exhaust gas boiler of the operating ship.

Hydrophobic Black Carbon Capture from Ship Emissions Based on a Charger-Coupled Wet Scrubber

“…20 In addition, the massive BC emission and higher exhaust temperature of marine engines contribute to a rapid increase in backpressure, thereby reducing the engine's thermal efficiency and increasing the risk of damage to exhaust valves and turbochargers. 21,22 Therefore, the feasibility of employing particulate filters for BC capture on large low-speed engine vessels is limited.…”

“…However, the emission characteristics of BC from ships vary significantly by fuel, with marine diesel oil and heavy fuel oil engines emitting approximately 2–15 times more BC emissions than marine gas oil engines, mainly due to their higher average sulfur content. , The high sulfur content can lead to catalyst deactivation and the formation of thermally stable sulfates, causing severe difficulties in the regeneration of particulate filters . In addition, the massive BC emission and higher exhaust temperature of marine engines contribute to a rapid increase in backpressure, thereby reducing the engine’s thermal efficiency and increasing the risk of damage to exhaust valves and turbochargers. , Therefore, the feasibility of employing particulate filters for BC capture on large low-speed engine vessels is limited.…”

Unsteady Heat Transfer of Pulsating Gas Flows in a Gas-Dynamic System When Filling and Emptying a Cylinder (as Applied to Reciprocating Machines)

“…It is worth highlighting studies in which researchers and professionals develop special technical devices for their installation in the exhaust system in order to additionally use the energy (temperature) of the exhaust gases of RICE [21][22][23][24]. For example, P. Fernández-Yáñez and colleagues studied the thermoelectric generator installation in the exhaust system of RICE [21].…”

“…It has been established that the energy produced from a thermoelectric generator is several times higher than the resistance losses. D. Jiang et al studied the efficiency of a waste heat boiler for exhaust gases from a marine engine [22]. Optimal operating modes of the engine and waste heat boiler were obtained on the basis of data on average speeds and temperatures in the exhaust system of the RICE.…”