Large Diesel Engines Research Articles

Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.

Lubricant transport across the piston ring with flat and triangular lubrication injection profiles on the liner in large two-stroke marine diesel engines

A theoretical investigation of the lubricant transport across the top compression piston ring in a large two-stroke marine diesel engine is presented. A numerical model for solving Reynolds equation between the piston ring and cylinder liner based on the finite difference method in one dimension has been made. The model includes force equilibrium of the piston ring, perturbation of Reynolds equation, and transient mass conservation. The model represents a new method of achieving mass conservation across the piston ring and between different time-dependent positions. For analyzing the lubricant transport across the piston ring, two different kinds of initial lubricant profile on the liner and two different kinds of load are investigated i.e. a flat profile and an approximated triangular profile as well as no load and a combustion load based on a combustion pressure profile. The impact from the different load conditions and different lubricant profiles on the liner are presented for film thicknesses, development in the lubricant profiles on the liner as well as the lubricant consumption at each stroke.

Adaptive Observer for Nonlinearly Parameterized Hammerstein System With Sensor Delay—Applied to Ship Emissions Reduction

Taking offspring in a problem of ship emission reduction by exhaust gas recirculation control for large diesel engines, an underlying generic estimation challenge is formulated as a problem of joint state and parameter estimation for a class of multiple-input single-output Hammerstein systems with first-order dynamics, sensor delay, and a bounded time-varying parameter in the nonlinear part. This brief suggests a novel scheme for this estimation problem that guarantees exponential convergence to an interval that depends on the sensitivity of the system. The system is allowed to be nonlinear, parameterized, and time dependent, which are characteristics of the industrial problem we study. The approach requires the input nonlinearity to be a sector nonlinearity in the time-varying parameter. Salient features of the approach include simplicity of design and implementation. The efficacy of the adaptive observer is shown on simulated cases, on tests with a large diesel engine on test bed, and on tests with a container vessel.

Adaptive feedforward control of exhaust recirculation in large diesel engines

Environmental concern has led the International Maritime Organization to restrict NOx emissions from marine diesel engines. Exhaust gas recirculation (EGR) systems have been introduced in order to comply to the new standards. Traditional fixed-gain feedback methods are not able to control the EGR system adequately in engine loading transients so alternative methods are needed. This paper presents the design, convergence proofs and experimental validation of an adaptive feedforward controller that significantly improves the performance in loading transients. First the control concept is generalized to a class of first order Hammerstein systems with sensor delay and exponentially converging bounds of the control error are proven analytically. It is then shown how to apply the method to the EGR system of a two-stroke crosshead diesel engine. The controller is validated by closed loop simulation with a mean-value engine model, on an engine test bed and on a vessel operating at sea. A significant reduction of smoke formation during loading transients is observed both visually and with an opacity sensor.

Modeling the condensation of sulfuric acid and water on the cylinder liner of a large two-stroke marine diesel engine

Corrosive wear of cylinder liners in large two-stroke marine diesel engines that burn heavy fuel oil containing sulfur is coupled to the formation of gaseous sulfur trioxide (SO3) and subsequent combined condensation of sulfuric acid (H2SO4) and water (H2O) vapor. The present work seeks to address how fuel sulfur content, charge air humidity and liner temperature variations affects the deposition of water and sulfuric acid at low load operation. A phenomenological engine model is applied to simulate the formation of cylinder/bulk gas combustion products and dew points comply with H2O–H2SO4 vapor liquid equilibrium. By assuming homogenous cylinder gas mixtures condensation is modeled using a convective heat and mass transfer analogy combined with realistic liner temperature profiles. Condensation of water is significantly altered by the liner temperature and charge air humidity while sulfuric acid condensation (the order is a few mg per cylinder every cycle) is proportional to the fuel sulfur content. Condensation takes place primarily in the upper part of the cylinder liner where a reduction of the surface temperature or saturated charge air provides that the deposited acid can be highly diluted with water.

Design, development, and implementation of low cost high performance mufflers for heavy duty diesel engines

In this paper, details on the design and fabrication of affordable high-performing passive exhaust mufflers and associated low volume manufacturing technology for commercial heavy duty diesel engines are presented. The exhaust noise radiation to the atmosphere from large diesel engines used in earth-moving, military, and other heavy equipment machines ranks as a major noise source of the urban environment. A solution to this problem is the use of mufflers to significantly reduce noise pollution to the atmosphere. There are several types of common mufflers, including reactive designs using resonators, expansion chambers, perforations, and dissipative configurations using absorptive materials. The design and realization of mufflers for a particular engine is dependent on several design parameters, such as internal combustion engine characteristics, acoustical requirements by standards, production volumes and cost, with the requirements varying from application to application. Particulars of successful muffler designs for three different machines—a commercial excavator, a tele handler, and a military ground vehicle are presented in this paper. The designs include both box type and round mufflers with Helmholtz resonators, reversible flow chambers, and perforated tubes, all capable of custom fabrication using conventional manufacturing processes in a local machine shop using commercially available materials.

A Robust Industrial Procedure for Measuring Modal Sound Fields in the Development of Radial Compressor Stages

The turbocharger is a significant noise source in large diesel engines, such as those used in container vessels. Its main noise source is the radial compressor, where improvements in silencers and turbocharger insulation have led to a considerable reduction of compressor inlet noise emission over the past few years. As a result, compressor outlet noise is now becoming increasingly significant for large engines. Recently, an in-house compressor testbed was upgraded by adding an acoustic modal measurement system (MSMS) that allows detailed investigation of modal sound fields inside the piping. This forms part of an updated compressor acoustic qualification procedure. This paper is an in-depth treatise of the characteristics of this modal measurement system. The calculation approach for the modal decomposition and a simplified alternative that assumes axial propagation, as well as relevant considerations, such as spatial resolution, averaging, and the use of multiple reference sensors, are addressed. Various measurement parameters, such as repeatability, measurement time, required temperature stability, pressure scaling, flow noise and their impact on measurement uncertainty were investigated. A successful validation of the modal sound measurement system with a well-known modal sound field at the compressor inlet is also presented. Finally, the characteristics of the modal sound fields of the compressor outlet of a typical modern turbocharger are discussed. Modal decompositions at the first two blade passing frequencies (BPFs) are presented for selected operating points (OPs). The response of total sound power levels (PWLs) to compressor speed along the operating line (OL) is examined by means of both the present and the simplified algorithm. A sensitivity analysis shows the impact of volume flow and rotational speed on the modal sound distribution.

Cavitation Flow Visualization in Marine Diesel Injectors

Injector geometries of large marine two-stroke diesel engines differ extensively from configurations typically used in diesel engines for heavy duty and automotive applications. Fuel is usually injected into the cylinder using multiple injectors that are arranged around the cylinder wall. As a result, the injector orifices are asymmetrically arranged as all the bores face a similar direction. Due to this geometric setup, the orifices are also distributed eccentric with respect to the central bore of the injector. Experiments have shown that sprays from such orifices propagate nonsymmetrical to the nominal axis of the orifice. Those spray deviations can lead to wall wetting which increases fuel consumption, emissions, component temperatures and loss of lubrication film on the cylinder wall. In addition, preliminary work using CFD simulations with an advanced cavitation model indicates that the two-phase, highly compressible flow inside the nozzle may strongly influence the spray propagation. To further investigate the in-nozzle flow and how it affects the spray morphology for large marine two-stroke diesel engine injectors, experiments were performed using transparent nozzles made of PMMA. The transparent nozzles were mounted on a marine diesel injector which was operated under ambient conditions and run with diesel at a pressure of 50 MPa. The nozzle used was an orthogonally arranged 0.75 mm diameter, one-hole setup that matches large marine two-stroke diesel engines injector nozzle diameters. High-speed shadowgraphy using a far-field microscope was applied to visualize the cavitation in the nozzle during the quasi-steady state injection process. These imaging results are used to compute statistical evaluations of cavitation in the nozzle over a range of conditions.

The Effects of the Intake Pipe Configuration on Gas Exchange, and Technical and Economic Indicators of Diesel Engine with 21/21 Dimension

The increase of the power density, improvement of fuel efficiency and minimization of the environmental impact of modern internal combustion engines form the main trend of the engine development. Turbocharging is pivotal to ensure the thermodynamical as well as commercial competitiveness of modern large diesel and gas engines. The optimization of the gas-dynamic and heat transfer characteristics of the gas flow in the intake system targeting the optimization of the gas exchange process is an important task in engine building. Numerical simulation of working process of the 8-cylinder 21/21 diesel-motor (Russia, Ekaterinburg) was performed with the ACTUS simulation software (Switzerland, Baden, ABB Turbo Systems Ltd). The numerical study showed that the geometric dimensions of the intake pipe significantly impact the flow dynamics. In particular, it is shown that the use of inlet pipe with a larger diameter (on the 8DM-21 engine) leads to the average 0.5% increase in the filling ratio. This leads to an up to 0.7 % increase in engine power and reduces the effective specific fuel consumption by about 0.50-0.75.

Research on the Field Dynamic Balance Technologies for Large Diesel Engine Crankshaft System

In order to reduce the unbalancing mass and the accompanying unbalancing vibration of diesel engine crankshaft system, the field dynamic balancing method and its key technologies are presented in the paper. In order to separate the unbalancing vibration signal from the total vibration signal of crankshaft system, the fundamental frequency signal fitting principle based on the least square method was introduced firstly, and then wavelet noise reduction method was applied to improve the signal fitting precision of least square method. Based on the unbalancing vibration signal analysis and assessment of crankshaft system, the influence coefficient method was applied to calculate the value and phase of the equivalent unbalancing mass in flywheel. To easily correct the unbalancing condition of crankshaft system, the unbalancing adjustment equipment was designed based on the flywheel structure. The balancing effect of field dynamic balancing system designed for the large diesel engine has been verified by field experiments.

Measuring Sound Pressure Levels during Thermoacoustic Instabilities in Large Engines: Case Study

This paper attempts to present some registers of sound pressure levels during the operation of large diesel engines (10 MW). During these registers we have found the preparation, occurrence and ending of events of thermoacoustic instability. They appear after a loosing of chaos period or a reduction in fluctuations in some frequencies. The most interesting phenomena were registered at low frequencies. However, they were accompanied by variations in sound emissions at medium and high frequencies. As there has been very little published data concerning these phenomena at real scale, it is imperative to point out that every quasi-stationary state we have measured during these episodes has lasted some minutes, significantly much more time than that of lab scale results.

Expansion of organic Rankine cycle working fluid in a cylinder of a low-speed two-stroke ship engine

Electricity and power produced from waste heat is particularly relevant in shipping because fuel expenses constitute the majority of the cost of operating the ships; however, the cost-benefit aspect limits the widespread implementation of waste heat recovery power units on ships. This paper presents the thermodynamic analysis of a concept that aims at reducing the cost of an organic Rankine cycle unit by using one of the cylinders in a large diesel engine as expansion device. Numerical models were used to optimise the process parameters and thereby determine the power potential for this concept. The evaluation of 104 working fluids points to cyclopropane, R245fa and R1234ze(z) as the most promising. The results suggest that the power produced by the organic Rankine cycle cylinder is at least equivalent to that of the cylinders operating with the diesel process. This enables potential fuel savings and emissions reductions of about 8.3% in the studied scenario.

Control-Oriented Model of Molar Scavenge Oxygen Fraction for Exhaust Recirculation in Large Diesel Engines

Exhaust gas recirculation (EGR) systems have been introduced to large marine engines in order to reduce NOx formation. Adequate modeling for control design is one of the bottlenecks to design EGR control that also meets emission requirements during transient loading conditions. This paper therefore focuses on deriving and validating a mean-value model of a large two-stroke crosshead diesel engine with EGR. The model introduces a number of amendments and extensions to previous, complex models and shows in theory and practice that a simplified nonlinear model captures all essential dynamics that is needed for EGR control. Our approach is to isolate and reduce the gas composition part of the more complex models using nonlinear model reduction techniques. The result is a control-oriented model (COM) of the oxygen fraction in the scavenge manifold with three molar flows being inputs to the COM, and it is shown how these flows are estimated from signals that are commonly available. The COM is validated by first comparing the output to a simulation of the full model, then by comparing with measurement series from two engines. The control-oriented nonlinear model is shown to be able to replicate the behavior of the scavenge oxygen fraction well over the entire envelope of load and blower speed range that are relevant for EGR. The simplicity of the new model makes it suitable for observer and control design, which are essential steps to meet the emission requirements for marine diesel engines that take effect from 2016.

Demonstrating Improved Fuel Economy Using Subsystem Specific Lubricants on a Modified Diesel Engine

ABSTRACTFuel economy performance in modern internal combustion engines is of increasing importance to lubricant formulators due to regulations targeting global greenhouse gas emissions. Engines typically employ a single lubricant, with a common sump, to service all components. As a result, base oil and additive selection for fuel economy performance is a compromise among competing demands for different engine subsystems. Opportunities for significant fuel economy improvement through targeted formulation of lubricants for specific engine subsystems are presented, with specific emphasis on segregating the lubricant supplies for the valve train and the power cylinder subsystems. A working prototype was developed in a lab environment by modifying a commercially available twin-cylinder diesel engine. Motored valve train and whole-engine fired test results were obtained and compared to model data. Fuel economy benefits were demonstrated using market representative heavy-duty diesel lubricants, including mineral oil and polyalphaolefin (PAO) blends. The fuel economy benefits of a dual-loop lubricant system are demonstrated through significant viscosity reduction in the power cylinder subsystem, achieving overall engine friction reductions of up to 8% for the investigated operating condition. Results suggest that additional gains may be realized through targeted base oil and additive formulation. Implications for incorporation in larger diesel engines are also considered.

Testing of bearing materials for large two-stroke marine diesel engines

In large two-stroke marine diesel engines, bearings are designed to last the lifetime of the engine. The design has shown very good service experiences. The design parameters of the main bearings are, among others, based on the average maximum specific load which the bearing should operate under. In general, the frictional loss is less than 1% of the nominal power of the engine but is still a target for optimization. Fatigue mechanisms of bearing lining material are not fully understood and the design limits with regards to minimum oil film thickness, max oil film pressure and oil film pressure gradient are not established. Large two-stroke journal bearings are not suitable for fatigue test due to the size, the low rotational speed and the complexity of such a test-rig. The disc fatigue test rig was designed with the purpose to test white metal coatings under realistic bearing conditions, in a confined time-frame. The test-rig simulates a scale model of a thrust bearing, in contrary to standard design, the bearing lining material is applied to the rotating collar. Parameters, such as bearing load, rotational speed, oil temperature, oil contamination is controlled/monitored in order to achieve repeatability and a systematic approach to the experiments. Test performed on the test-rig shows good correlation on the fatigue cracks with those experienced on large two-stroke journal bearings.

Optimizations of the waste heat recovery system for a large marine diesel engine based on transcritical Rankine cycle

The aim of this study is to investigate the economic performance of the waste heat recovery (WHR) system for a marine diesel engine. Four waste heat sources, which are exhaust gas, cylinder cooling water, scavenge air cooling water and lubricating oil of a marine diesel engine, are first applied to drive the transcritical Rankine cycle (TRC). R1234yf, R1234ze, R134a, R152a, R236fa and R290 are employed in the system as working fluids. The effects of expander inlet pressure and temperature on net power output, thermal efficiency, total cost, mass flow rate, and available efficiency of the WHR system are analyzed. The levelized energy cost is used to evaluate the economic optimizations and their corresponding optimal parameters in the WHR system. The results show that the optimal levelized energy cost of R236fa is the most excellent and is lower than that of R1234ze, R134a, R152a, R1234yf or R290 by 5.07%, 6.25%, 7.42%, 9.77% or 12.11%, respectively. The payback period, fuel oil saving, and CO2 emission reduction are applied to assess the suitability of these working fluids. Furthermore, the economic optimization correlations in terms of dimensionless optimal pressures and temperature difference ratios are proposed for the system design of the optimal operating conditions.

Fault diagnosis for large diesel fuel engine based on chaotic fractal method

In contrast with the large diesel engine fuel system operational condition complexity, the chaotic fractal characteristics in the combustion process of the diesel engine fuel system are systematically analyzed. Then, based on chaotic fractal method, an effective fault diagnosis method is further proposed. And under the two kinds of typical failure modes, the two important characteristic parameters variation trend for chaotic system, namely, correlation dimensions and the calculation methods of the maximum Lyapunov exponent are discussed. On the process of chaotic parameters calculation the wavelet noise reduction method is used to handle the original signal to conquer the linear scaling region properly. The results show that the maximum Lyapunov exponent method is a more effective method on the diesel engine fuel system fault diagnosis than the correlation dimension method, which can be further used in health condition assessment for this type fuel engine.

Performance and emission characteristics of additives-enhanced heavy fuel oil in large two-stroke marine diesel engine

The International Maritime Organization (IMO) Marine Environment Protection Committee (MEPC) has gradually strengthened the laws regulating ship exhaust emissions. The majority of ships designed for international voyages and powered by large two-stroke marine diesel engines use heavy fuel oil (HFO), which has the advantage of a low price compared to other types of fuel. However, HFO generates large amounts of harmful exhaust emissions during combustion in a marine diesel engine. In addition, as fuel costs account for a large portion of the expenditure budgets of the shipping companies that operate and manage such ships, fuel cost reduction is of considerable interest to such companies. In this study, two fuel additives, oil-soluble Ca-based and oil-soluble Fe-based organometallic compounds, which can improve the performance of diesel engines, were injected into HFO at fixed concentrations (1/4000 and 1/6000 of the total fuel, respectively), in attempts to reduce fuel consumption and exhaust emissions. For enhanced experimental accuracy and reproducibility, a large two-stroke diesel engine installed in a land-based power plant was used as the test subject. Evaluative tests were conducted for three engine loads (50%, 75%, and 100%). The engine performance (i.e., the fuel consumption rate, maximum combustion pressure, and exhaust gas temperature) and the exhaust emissions (NOx, particulate matter (PM)) were analyzed before and after the fuel additive insertion.

Effects of oxidized biodiesel on formation of particulate matter and NO x from diesel engine

A test was conducted to investigate the effect of pure biodiesel without additives on formation of particulate matter (PM) and nitrogen oxide (NOx) in the exhaust gas of a diesel engine. Pure biodiesel from waste cooking oil without adding any additive was used. The biodiesel was oxidized at 110 °C for 10 days and blended with commercial automobile diesel oil distributed in the market as a testing fuel. Blended fuels were produced by adding 10% of oxidized biodiesel and un-oxidized biodiesel to automobile diesel oil, respectively. Material properties such as density, kinematic viscosity, oxidation stability, and cetane number were tested. Emission tests were conducted using a large diesel engine of direct injection type, inline six-cylinder, 4 stroke, turbocharger and intercooler. The oxidized and unoxidized biodiesel blends did not show any difference in density and kinematic viscosity. The oxidation stability of the oxidized biodiesel blends was lower than that of the unoxidized biodiesel blends. In the emission test, the two blends showed almost no difference in the total number of concentration of the micro-particles, and also showed almost no difference in particle size distribution such as nucleation mode and accumulation mode. On the other hand, the oxidized biodiesel blends showed less PM and NOx emission than the unoxidized biodiesel blends.

Thermodynamic and economic performance improvement of ORCs through using zeotropic mixtures: Case of waste heat recovery in an offshore platform

This paper presents a comparative thermodynamic and economic analysis of two kinds of organic Rankine cycles (ORCs) with pure and zeotropic mixtures for recovering waste heat from the exhaust gases of large diesel engines used in the offshore platforms of phase 12 of South Pars Gas on Persian Gulf. The mixtures of three hydrocarbons with two refrigerants in two cycle arrangements (simple ORC and ORC with internal heat exchanger) at different evaporation temperatures are investigated to optimize three indicators. The results showed that both the energy and exergy efficiencies are maximized at particular mass fractions of refrigerants. The ORC with mixture of R236ea/Cyclohexane (with a ratio of 0.6/0.4) has the best performance as its energy and exergy efficiency are 14.57% and 37.84%, respectively. These values are increased to 16.81% and 40.75%, respectively by adding IHE to system. The minimum amount of the specific investment cost for the most cases is achieved at the mass fractions of 0.1 and 0.5 and it is greater for the ORC with IHE. Also the payback period of investment is calculated for comparison of economic value of systems and it is observed that its amounts for the ORC with IHE are greater than simple one.