S. Szwaja

The effect of methanol-diesel combustion on performance and emissions of a direct injection diesel engine

The results of CFD modelling a dual fuel diesel engine powered with both methanol and diesel fuel is presented in the paper. Modelling was performed with 20 and a 50% energetic share of methanol in the entire dose. The analysis was conducted on both the thermodynamic parameters and exhaust toxicity of dual fuel engine. It was found that the various share of methanol influences the ignition delay of the combustion process and after start of main phase of combustion, the process occurs faster than in case of the diesel engine. It was found that the time of 10-90% burn of the fuel is much shorter than it is in the diesel engine. The dual fuel engine was characterized by higher indicated mean pressure in the whole range of diesel fuel injection timings. While analysing toxic exhaust emission from the dual fuel engine powered with methanol, it was found that the rate of NO formation was significantly higher than from the diesel engine. The combustion process in the dual fuel engine occurs more rapidly than in the conventional diesel engine, which contributes to form areas with high temperature, and in combination with presence of oxygen from the air and oxygen bonded in the methanol, promotes the NO formation. In the case of the dual fuel engine, it was found that soot emission was reduced. The engine running with diesel injection start at 8.5 deg before TDC, the soot emissions were more than twice lower in the dual fuel engine, while the emission of NO was much higher.

Influence of intake valve closure angle on IC engine indicated parameters

The paper presents results of modelling study of influence of an intake valve closure angle on IC engine indicated parameters. The modelled engine was Andoria S231, which was working on methane. At first, optimizations of the model were done by comparison of the indicated mean effective pressure for real engine and modelled engine. Next, modelling was done for early intake valve closure angle in comparison to original closure angle. The engine was simulated as a naturally aspirated one and for the cases such indicated; parameters as indicated efficiency, mean indicated pressure, fuel consumption were calculated. During the modelling ignition, timing and air-fuel ratio were fixed. For better comparison for two cases of early intake valve closure angle the engine was modelled as supercharged one where mean indicated pressure was fixed at the same level as for the naturally aspirated engine working with original valve timing and indicated parameters were calculated and compared with in parameters determined from this naturally aspirated engine. Because of the calculations, characteristics of indicated parameters vs. intake valve closure angle were computed. As a result of this research, both the decrease in indicated efficiency, indicated mean effective pressure were shown, temperature of fresh charge, end of compression stroke and maximum incylinder temperature were observed for naturally aspirated engine with early intake valve closure angle.

Anomalies in combustion of hydrogen in a SI engine modified to work as a supercharged one

The paper describes combustion anomalies of various types randomly or permanently occurring while hydrogen is burnt in a supercharged spark ignited reciprocating engine. The anomalies were mainly identified as result of combustion pressure data analysis. Originally, the engine was a compression ignition one fuelled with diesel fuel. Modifications done on the engine dealt with decrease in its geometric compression ratio and equipping it with a spark plug located in diesel fuel injector position. The anomalies presented in the paper are typically associated with several abnormal phenomena as follows: flame propagation into intake manifold called back-fire, hydrogen spontaneous ignition by hot surface, flame propagation during valves overlap and extinguishing spark discharge flame kernel by high turbulence around a spark plug. These anomalies were observed in the supercharged engine, however, some of them were also detected while the engine was operated as a freely aspirated one. As investigated, some of these malfunctions would have been removed by change in engine operating parameters. Others need major changes in both exhaust pipeline geometry, hydrogen injection system, engine cylinder geometry and valve timing.

Hydrogen combustion in the supercharged SI engine

The experimental results of combustion pressure processing from a supercharged spark ignition (SI) engine that was running on hydrogen are exposed in the paper. Hydrogen was delivered in two ways by an injector and mixer installed in an intake port. In–cylinder pressure while combusting hydrogen was analyzed with various coefficient of stechiometry and boost pressure. These parameters were limited by abnormal combustion known as “knock” combustion. Hydrogen fueled engine has tendency to generate “knock”, especially this abnormal combustion phenomena increases with increase in boosting pressure. Hence, the thermodynamic parameters such as pressure and temperature of fresh air fuel mixture are elevated. The experimental numeric data analysis permit for compare to naturally aspirated engine such parameters as mean indicated pressure, indicated efficiency. Also for both cases, the coefficient of variation for mean indicated pressure was determined. It was found that combustion duration shortens itself with higher boosting pressure. Thus, optimal spark timing to get the maximum indicated mean effective pressure is shifted closer to the TDC. Another parameter that was expected to be increased was the knock intensity. It was observed, that knock intensity did not increase significantly and was still below the limit for pressure pulsations treated as combustion noise coming from light combustion instabilities.

Conversion of exhaust gases from the internal combustion engine to electrical power at small scale

Concept of a small scale waste heat recovery system using exhaust gases from the internal combustion engine is presented in the paper. The system is based on the Clausius-Rankine steam cycle as recommended for this purpose due to its simplicity and relatively lower investment costs if compared to the organic Rankine cycle systems. The source of the waste heat were exhaust gases from the internal combustion engine fueled with a biogas (60% methane and 40% carbon dioxide). The engine power was assumed of 700 kW. On the basis of thermodynamic analysis the following results were obtained: the waste heat recovery boiler produced steam at amounts of 158 kg/h at 350°C and 12 bar. The turbine generates power of 24 kW and overall heat-to-electricity efficiency of this power system was approximately 17%. Furthermore, impacts of several parameters on cycle efficiency and turbine power were investigated with aim to provide the system optimization. Summing up, waste heat recovery systems, as presented in the paper, can be proposed as promising solutions for increasing overall efficiency of fuel-to-power conversion systems based on combustion technologies.

Combustion of the biomethane in an IC engine with over-expanded cycle

The paper presents results of the experimental investigation on an internal combustion (IC) over-expanded engine fueled with biomethane. During this research the pressure trace of the combustion was collected and on that basis the analysis of the combustion process has been made. The measurements were done for two engine configurations with the classic Otto cycle and the over-expanded cycle. Over-expanded cycle was achieved by changing the intake cam profile and provide earlier intake valve closure before BDC. To recompense the lost in the engine power a supercharging was used. Additionally, during the measurements the parameters as TDC position, crankshaft position, temperature of both the intake air, the engine coolant and fuel were collected. On the basis of those measurements the characteristics of the pressure as functions of crank angle and mass fraction burned (xb) were performed to show possibilities for different engine configurations. As a result of this research, it can be concluded that the over-expanded cycle in the IC engine leads to increase in thermal efficiency and the supercharging is a proper measure to compensate losses in engine power caused by use the over-expanded cycle.

The possibility of use a waste product of biofuels production-glycerol as a fuel to the compression ignition engine

The article presents results of tests performed in a combustion research unit (CRU) with the two following fuels: light fuel oil (LFO) and glycerol. The CRU is a constant volume combustion chamber machine equipped with an injection system based on that used in common-rail diesel engines with electromagnetic injectors. This machine allows to compare various combustion properties between fuels for specified parameters of injection and a combustion chamber as well. As it is known glycerol is a substance which is obtained from several technological processes such as production of biofuel thus in this way it can be treated as an alternative renewable fuel. The glycerol is characterized by low heating value of 16MJ/kg and relatively high density of 1261 kg/m3. However, its heating value by volume is higher if compared to other liquid fuels. From that reason decrease in energy that can be delivered with fuel is smaller compared to LFO which is approximately 16%. The parameters measured during this research were: pressure increase, rate of pressure increase (ROHR), ignition delay (ID), main reaction delay (MRD), main combustion period (MCP), end of main combustion (EMC), end of combustion (EC), position of max ROHR (PMR) and max ROHR. The tests were performed with different injection parameters such as injection pressure, injection duration and injection delay as well as under various conditions in the CRU combustion chamber expressed by pressure and temperature. On the basis of these tests the comparison between LFO and glycerol was done. The results were presented in diagrams. The research shows that glycerol used as a fuel, to obtain the same output power, should be injected at higher amounts. Glycerol as a fuel cannot ignite itself, hence to provide combustion the pilot injection of another fuel have to be applied.

New concept of a rocker engine - kinematic analysis

The paper presents concept and design of a four-stroke 4-cylinder internal combustion engine consisted of a single connecting rod to a crankshaft and four additional rods joining pistons with a rocker. The rocker is a specific element in the engine construction that makes this engine different from the typical reciprocating internal combustion piston engine. Furthermore, kinematical analysis of this piston rocker crankshaft mechanism was conducted. As concluded from the analysis, this mechanism implemented to the engine, provides several advantages with respect to both dynamic and thermodynamic related issues. First of all, a profile of the piston motion can be easily changed with change in the mechanism geometry e.g. major dimensions of connecting rods, the rocker etc. Thus, the piston motion profile can be asymmetrical with slow motion to and relatively fast distancing from the TDC. This feature can be useful in reducing thermal losses to an engine cooling system. Additionally, the mechanism characterizes itself with low transverse force from the piston, which acts on a cylinder liner. As a result, it significantly reduces frictional losses and should increase the overall efficiency of the engine. Among disadvantages, higher inertial forces are the most important problem. As analyzed, the rocker is the main component that contributes to increase in inertial forces by approximately three to four times. On the other hand, total inertia forces, due to specific kinematical chain of the mechanism, can be remarkably reduced in case the mechanism is correctly optimized.

Cost analysis of hydrogen energy generation

Relatively high energy costs and the perspective of running out fossil fuel natural resources stimulates scientists and engineers all over the world to concentrate their efforts on inventing new sources of energy. For decades, hydrogen technology is considered as source of renewable energy. Hydrogen can be used both as the energy carrier as far as substrate in the chemical industry. Plans for hydrogen utilization as the fuel applied to automotive engines also is under investigation. Lot of works describing various technologies for hydrogen processing have come into being, the ways of production and storing this substance have also been worked out. The important part in analysis is costs of applying fuels with respect to their impact on natural environment. As found, these costs are usually difficult to be estimated. In this paper, the main directions in development of hydrogen technologies were analysed concerning total costs for hydrogen processing. As concluded, overall costs of the technology for both hydrogen generation and electric power production are significantly higher with respect to costs for energy generation by coal-fired power plants. The hydrogen production costs characterized themselves with the highest share in overall costs at hydrogen economy, and they depend on technology development. It is expected that overall costs of production, transportation and storage of hydrogen should be remarkably reduced in short-medium term future because of development in: photovoltaic technology – that will contribute to reduce hydrogen production costs by electrolysis process. Additionally, it is expected to reduce costs for hydrogen storage.