Modification of marine engine to DME fuel for less emission from diesel engine
The idea of the pilot investment was to establish a testing facility for selected fuel system configurations to make marine diesel engine more environmentally friendly. In this regard, the Floating Laboratory PHOTON, being in fact 40 feet, 45 m2 sails and 43 HP diesel engine, steel research vessel owned by the Gdansk University of Technology has been adopted to be powered by mixture of diesel oil and dimethyl ether (DME). High oxygen content and absence of C–C bonds in the DME molecule significantly contribute to smokeless combustion which is one of the most important advantages of DME. PHOTON maintains simultaneously the ability to run the engine on exclusively the base fuel, which is diesel oil.
Components installed in the solution
Remodeling of PHOTON required among others reconstruction of the engine compartment and drive system as well as assembly of tanks with pumps and valves for liquid and gaseous fuel, including:
- development and installation of a dual-fuel diesel engine supply system;
- adaptation works of the hull and selected equipment systems in terms of the installation of a sealed, ventilated engine compartment and fuel tanks, adapted to the use of a gas-liquid dual fuel system;
- design, development, construction, installation and commissioning of the environmental assessment system for engine operation;
- design of data acquisition, installation of sensors, commissioning and testing of the system;
- system testing in selected fuel mixture configurations.
The solution was designed by the Gdansk Tech team in cooperation with the GAS-TECH Bogusław Skarpetowski Company and the JABO Stocznia Jachtowa Jan Wierzchowski Company, both from Gdansk.
Elements of the system were installed both onboard and within the hull of the research boat. DME pressure tanks are located on the stern for safety reasons. The fixing enables easy disconnection and removal of the tanks, each with individual shut-off valve.
An electro-valve automatically cuts off the gas supply to the installation in emergency situations, e.g. when the gas detection alarm in the engine room is triggered. From storage tanks DME is transferred in copper pipes to the reducer where it is turned from the liquid phase to the gas phase. The required heat for gas expansion origins from the engine cooling system. Subsequently, the gas is delivered to the engine. Each of four cylinders has its own injector located in the intake manifold directly above the valve seat. Such solution enables better control of the fuel dose and injection timing. The gas injectors are electronically controlled by a programmed computer.
The dual fuel installation is to enable the engine to function in two fueling modes: diesel fuel only and a mixture of diesel oil and DME. Another gas fuel such as LPG can be used. Therefore, the existing diesel fuel delivery system required adjustments, including the control of the diesel high pressure pump. As a standard, the pump is mechanically regulated. This solution is not sufficient when the engine is converted to work in various fuel modes. Therefore, automatic adjustment of the injection pump, reducing the amount of diesel oil with respect to the DME dose was introduced.
The exhaust gas emissions are measured with the Testo 350 exhaust gas analyzer. At the same time, data are transferred to the computer from sensors, including: fuel flow rate, measurement of engine operating parameters, number of engine revolutions, as well as indications of a dynamometer measuring engine thrust during tethered tests. The exhaust gas analysis includes CO2, CO, NOx, NO, NO2, O2, SO2, CH and temperature. The sampling probe was positioned directly at the exit of the engine exhaust manifold. The flue gas analyzer connects wirelessly to the data acquisition system. Samples for quantitative and qualitative analysis of fine particles present in the exhaust gases are collected directly after the mixer of sea water and exhaust gases after 3 minutes of stabilization of the engine speed and the composition of the exhaust gases. Sea water is also taken as a reference sample.
The data acquisition system includes 64 variables with the possibility of graphical presentation, data archiving, report generation and takes into account alarm occurrences. The system is equipped with mnemonic diagrams of engine structures and selected measuring points.
The test results are developed in terms of the functionality and durability of the engine, changes in the dynamics of its work and reduction of the emission of toxic compounds. As part of international cooperation, joint research on the PHOTON vessel is planned with members of the Cross-Border Cluster of Green Technologies established as part of the RBR project. The aim is to reduce pollutant emissions from marine engines through more environmentally friendly combustion of a mixture of liquid and gaseous fuel, primarily for renewable fuels.