Experimental Investigation of Fuel Anti-Knock-Index Requirements in Three Small Two-Stroke Engines for Remotely Piloted Aircraft

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Joseph K. Ausserer ◽  
Marc D. Polanka ◽  
Paul J. Litke ◽  
Jacob A. Baranski
Keyword(s):  
Power Plants ◽  
Internal Combustion Engines ◽  
Fuel Conversion ◽  
Combustion Heat ◽  
Absolute Increase ◽  
Fuel Switching ◽  
Remotely Piloted Aircraft ◽  
Si Engines ◽  
Commercial Off The Shelf ◽  
Burn Rate

Small remotely piloted aircraft (10–25 kg) that are powered by internal combustion engines typically operate on gasoline with an anti-knock index (AKI) > 80. To comply with the single-battlefield-fuel initiative [Department of Defense (DoD) Directive 4140.25], interest has increased in converting power plants for these platforms to run on low-AKI fuels such as diesel and Jet-A with AKIs of ∼20. It has been speculated that the higher losses (short circuiting, incomplete combustion, heat transfer) that cause these engines to have lower efficiencies than their conventional-scale counterparts may also relax their required fuel AKI. The fuel-AKI requirements of three two-stroke spark ignition (SI) engines with 28, 55, and 85 cm3 displacements were mapped, and the performance was compared to that on 98 ON (octane number) fuel. Switching from 98 ON fuel to 20 ON (Jet-A and diesel equivalent AKI) fuel while maintaining optimum combustion phasing led to a 3–5 crank-angle degree (CAD) reduction in burn angle, a 2–3% increase in power, and a 0.5–1% (absolute) increase in fuel-conversion efficiency at non-knock-limited conditions through shortening of the CA0–CA10 burn angle. The efficiency improvement translates to a 6% increase in range or endurance. The results indicate that abnormal combustion is not a significant obstacle to operating small commercial-off-the-shelf (COTS) engines on low-AKI fuels and that most of the power and efficiency improvements demonstrated in previous heavy-fuel conversion efforts were the result of modifications made to accommodate low-volatility fuels, not the faster burn rate of the low-AKI fuels themselves.

Engine-Control Impact on Energy Balances for Two-Stroke Engines for 10–25 kg Remotely Piloted Aircraft

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Joseph K. Ausserer ◽  
Marc D. Polanka ◽  
Paul J. Litke ◽  
Jacob A. Baranski
Keyword(s):  
Conversion Efficiency ◽  
Equivalence Ratio ◽  
Internal Combustion Engines ◽  
Rapid Expansion ◽  
Combustion Stability ◽  
Fuel Conversion ◽  
Absolute Increase ◽  
Spark Timing ◽  
Remotely Piloted Aircraft ◽  
Energy Pathways

The rapid expansion of the market for remotely piloted aircraft (RPA) includes a particular interest in 10–25 kg vehicles for monitoring, surveillance, and reconnaissance. Power-plant options for these aircraft are often 10–100 cm3 internal combustion engines (ICEs). The present study builds on a previous study of loss pathways for small, two-stroke engines by quantifying the trade space among energy pathways, combustion stability, and engine controls. The same energy pathways are considered in both studies—brake power, heat transfer from the cylinder, short circuiting, sensible exhaust enthalpy, and incomplete combustion. The engine controls considered in the present study are speed, equivalence ratio, combustion phasing (ignition timing), cooling-air flow rate, and throttle. Several options are identified for improving commercial-off-the-shelf (COTS)-engine efficiency and performance for small, RPA. Shifting from typical operation at an equivalence ratio of 1.1–1.2 to lean operation at an equivalence ratio of 0.8–0.9 results in a 4% (absolute) increase in fuel-conversion efficiency at the expense of a 10% decrease in power. The stock, linear timing maps are excessively retarded below 3000 rpm, and replacing them with custom spark timing improves ease of engine start. Finally, in comparison with conventional-size engines, the fuel-conversion efficiency of the small, two-stroke ICEs improves at throttled conditions by as much as 4–6% (absolute) due primarily to decreased short-circuiting. When no additional short-circuiting mitigation techniques are employed, running a larger engine at partial throttle may lead to an overall weight savings on longer missions. A case study shows that at 6000 rpm, the 3W-55i engine at partial throttle will yield an overall weight saving compared to the 3W-28i engine at wide-open throttle (WOT) for missions exceeding 2.5 h (at a savings of ∼5 g/min).

scholarly journals Modeling of advanced fossil fuel power plants

2021 ◽  
Author(s):  
Farshid Zabihian
Keyword(s):  
Power Generation ◽  
Gas Turbine ◽  
Power Plants ◽  
Fossil Fuel ◽  
Specific Power ◽  
Operating Pressure ◽  
Utilization Factor ◽  
Fuel Switching ◽  
Wide Range ◽  
Cycle Efficiency

The first part of this thesis deals with greenhouse gas (GHG) emissions from fossil fuel-fired power stations. The GHG emission estimation from fossil fuel power generation industry signifies that emissions from this industry can be significantly reduced by fuel switching and adaption of advanced power generation technologies. In the second part of the thesis, steady-state models of some of the advanced fossil fuel power generation technologies are presented. The impacts of various parameters on the solid oxide fuel cell (SOFC) overpotentials and outputs are investigated. The detail analyses of operation of the hybrid SOFC-gas turbine (GT) cycle when fuelled with methane and syngas demonstrate that the efficiencies of the cycles with and without anode exhaust recirculation are close, but the specific power of the former is much higher. The parametric analysis of the performance of the hybrid SOFC-GT cycle indicates that increasing the system operating pressure and SOFC operating temperature and fuel utilization factor improves cycle efficiency, but the effects of the increasing SOFC current density and turbine inlet temperature are not favourable. The analysis of the operation of the system when fuelled with a wide range of fuel types demonstrates that the hybrid SOFC-GT cycle efficiency can be between 59% and 75%, depending on the inlet fuel type. Then, the system performance is investigated when methane as a reference fuel is replaced with various species that can be found in the fuel, i.e., H₂, CO₂, CO, and N₂. The results point out that influence of various species can be significant and different for each case. The experimental and numerical analyses of a biodiesel fuelled micro gas turbine indicate that fuel switching from petrodiesel to biodiesel can influence operational parameters of the system. The modeling results of gas turbine-based power plants signify that relatively simple models can predict plant performance with acceptable accuracy. The unique feature of these models is that they are developed based on similar assumptions and run at similar conditions; therefore, their results can be compared. This work demonstrates that, although utilization of fossil fuels for power generation is inevitable, at least in the short- and mid-term future, it is possible and practical to carry out such utilization more efficiently and in an environmentally friendlier manner.

scholarly journals Thermodynamic modeling of solid fuel gasification in mixtures of oxygen and carbon dioxide

2021 ◽  
Vol 2119 (1) ◽  
pp. 012101
Author(s):  
I G Donskoy
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Modeling ◽  
Solid Fuel ◽  
Carbon Capture ◽  
Power Plants ◽  
Thermal Power ◽  
Carbon Capture And Storage ◽  
Low Oxygen ◽  
Fuel Conversion ◽  
Oxygen Concentrations

Abstract One of the main problems in the use of solid fuels is inevitable formation of significant amounts of carbon dioxide. The prospects for reducing CO2 emissions (carbon capture and storage, CCS) are opening up with the use of new coal technologies, such as thermal power plants with integrated gasification (IGCC) and transition to oxygen-enriched combustion (oxyfuel). In order to study the efficiency of solid fuel conversion processes using carbon dioxide, thermodynamic modeling was carried out. Results show that difference between efficiency of fuel conversion in O2/N2 and O2/CO2 mixtures increases with an increase in the volatile content and a decrease in the carbon content. The effect of using CO2 as a gasification agent depends on the oxygen concentration: at low oxygen concentrations, the process temperature turns out to be low due to dilution; at high oxygen concentrations, the CO2 concentration is not high enough for efficient carbon conversion.

The CFD Design and Optimisation of a 100 kW Hydrogen Fuelled mGT

2020 ◽  
Author(s):  
Cedric Devriese ◽  
Gijs Penninx ◽  
Guido de Ruiter ◽  
Rob Bastiaans ◽  
Ward De Paepe
Keyword(s):  
Combustion Chamber ◽  
Power Plants ◽  
Internal Combustion Engines ◽  
Cone Angle ◽  
Electricity Production ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Large Power ◽  
Power Sources ◽  
The Impact

Abstract Against the background of a growing deployment of renewable electricity production, like wind and solar, the demand for energy storage will only increase. One of the most promising ways to cover the medium to long-term storage is to use the excess electricity to produce hydrogen via electrolysis. In a modern energy grid, filled with intermittent power sources and ever-increasing problems to construct large power plants in densely populated areas, a network of Decentralised Energy Systems (DES) seems more logical. Therefore, the importance of research into the design of a small to medium-sized hydrogen fuelled micro Gas Turbine (mGT) unit for efficient, local heat and electricity production becomes apparent. To be able to compete with Reciprocating Internal Combustion Engines (RICEs), the mGT needs to reach 40% electrical efficiency. To do so, there are two main challenges; the design of an ultra-low NOX hydrogen combustor and a high Turbine Inlet Temperature (TIT) radial turbine. In this paper, we report on the progress of our work towards that goal. First, an improvement of the initial single-nozzle swirler (swozzle) combustor geometry was abandoned in favour of a full CFD (steady RANS) design and optimisation of a micromix type combustion chamber, due to its advantages towards NOx-emission reduction. Second, a full CFD design and optimisation of the compressor and turbine is performed. The improved micromix combustor geometry resulted in a NOx level reduction of more than 1 order of magnitude compared to our previous swozzle design (from 1400 ppm to 250 ppm). Moreover, several design parameters, such as the position and diameter of the hydrogen injection nozzle and the Air Guiding Panel (AGP) height, have been optimized to improve the flow patterns. Next to the combustion chamber, CFD simulations of the compressor and turbine matched the 1D performance calculations and reached the desired performance goals. A CFD analysis of the impact of the tip gap and exhaust diffuser cone angle led to a choice of these parameters that improved the compressor and turbine performance with a limited loss in efficiency.

Possibility of using gas lubricant in the cylinders of internal combustion engines of transport vehicles

2021 ◽  
pp. 13-20
Author(s):  
Keyword(s):  
Internal Combustion Engine ◽  
Bearing Capacity ◽  
Power Plants ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Engine Piston ◽  
Suspension Stiffness ◽  
Gas Layer

The prospects of using the gas-static suspension of the internal combustion engine piston in transport vehicles and power plants are considered. The diagram of the piston and the method for calculating the stiffness and bearing capacity of the gas layer surrounding the piston are presented, as well as the results of experiments that showed the relevance of this method. The possibility of gas and static centering of the engine piston is confirmed. Keywords: internal combustion engine, piston, gasstatic suspension, stiffness, bearing capacity, gas medium. [email protected]

Heat Transfer Analysis of Regenerative Thermo-Mechanical Refrigeration System

2020 ◽  
Author(s):  
Ahmad K. Sleiti ◽  
Mohammed Al-Khawaja
Keyword(s):  
Environmental Effects ◽  
Power Efficiency ◽  
Power Plants ◽  
Internal Combustion Engines ◽  
Waste Heat ◽  
Heat Transfer Analysis ◽  
Working Fluid ◽  
Refrigeration System ◽  
Renewable Energy Resources ◽  
Working Fluids

Abstract Refrigeration systems contribute to the critical environmental concerns including global warming and ozone depletion. It is necessary to develop new systems that use renewable energy resources and waste heat to perform the cooling function with eco-friendly working fluids. This improves the energy efficiency of the power systems and minimizes the harmful effects of conventional refrigeration systems. This paper introduces an analysis of a regenerative thermo-mechanical refrigeration system that is powered with renewable heat sources (solar, geothermal) or waste heat (from internal combustion engines, gas power plants, and steam power plants). The system operates at the supercritical conditions of the working fluids. The performance of the system is evaluated based on power efficiency, the COP, and the expander-compressor diameters. Also, a number of working fluids were compared with each other based on their performance and environmental effects. There is a trade-off between high-performance fluids and their environmental effects. Using R32 as a working fluid at Th = 150 °C and Tc1 = 40 °C, the system produces a cooling capacity of 1 kW with power efficiency of 10.23%, expander diameter of 53.12 mm and compressor diameter of 75.4mm. The regenerator increases the power efficiency by about 1%. However, the size of the regenerator is small (Dr = 6.5 mm, Lr = 142 mm].

Improved method to mitigate the effect of coal fuel switching on critical process parameters of a steam generator in a thermal power plant

2011 ◽  
Vol 225 (8) ◽  
pp. 1026-1040 ◽  
Author(s):  
S Dharmalingam ◽  
L Sivakumar ◽  
T Anandhi ◽  
M Umapathy
Keyword(s):  
Process Parameters ◽  
Power Plants ◽  
Thermal Power ◽  
Improved Method ◽  
Heating Value ◽  
Fuel Switching ◽  
Coal Fuel ◽  
Embedded Controller ◽  
Critical Process Parameters ◽  
Critical Process

The design and performance of steam generators supplied to thermal power plants are greatly influenced by the properties of coal burnt. All coals are not same and the variation of heating value of coal supplied to boiler results in changes in critical process parameters like pressure and temperature of main steam produced. These fluctuations are normally controlled by master pressure controller, provided the variation in heating value is within certain limits. If the heating value of coal being burnt varies substantially, a remedial measure is necessary to control the pressure and temperature fluctuations during coal fuel switching. The composition of the coal burnt currently in a boiler is determined from an online analyser, and an embedded controller computes the current heating value of the coal and suitably modifies the gains of all the controllers to arrest the undue fluctuations in pressure and temperature. A validated mathematical model for a typical 500 MW plant is used to simulate the variations in pressure and temperature of steam with normal and embedded controllers. Significant reduction in pressure and temperature variation has been achieved with an embedded controller. This article discusses the improved method of ensuring optimum boiler performance during coal fuel switchover.

scholarly journals Heat Emission from a Burning Cigarette

2001 ◽  
Vol 19 (5) ◽  
pp. 245-249
Author(s):  
K Miura ◽  
A Nagao ◽  
K Ueyama
Keyword(s):  
Heat Transfer ◽  
Heat Emission ◽  
Total Heat ◽  
Radiation Heat ◽  
Combustion Heat ◽  
Burn Rate ◽  
The Relationship

AbstractWe investigated the relationship between the smoldering burn rate and the heat transfer from a burning cigarette by measuring the heat emitted by radiation and convection, separately. The net heat generated and the net heat emitted by a burning cigarette did not vary with a change of the cigarette smoldering burn rate. The total heat emitted from a statically burning cigarette was about 50% of the total combustion heat. About 50% of the heat emitted was released as radiation heat. The smoldering burn rate did not affect the total amount of heat emitted nor the ratio of radiated heat to convected heat.

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