Small Internal Combustion Engine Research Articles

Development of a micro-combined heat and power powered by an opposed-piston engine in building applications

Residential homes and light commercial buildings usually require substantial heat and electricity simultaneously. A combined heat and power system enables more efficient and environmentally friendly energy usage than that achieved when heat and electricity are produced in separate processes. However, due to financial and space constraints, residential and light commercial buildings often limit the use of traditional large-scale industrial equipment. Here we develop a micro–combined heat and power system powered by an opposed-piston engine to simultaneously generate electricity and provide heat to residential homes or light commercial buildings. The developed prototype attains the maximum AC electrical efficiency of 35.2%. The electrical efficiency breaks the typical upper boundary of 30% for micro–combined heat and power systems using small internal combustion engines (i.e., <10 kW). Moreover, the developed prototype enables maximum combined electrical and thermal efficiencies greater than 93%. The prototype is optimally designed for natural gas but can also run renewable biogas and hydrogen, supporting the transition from current conventional fossil fuels to zero carbon emissions in the future. The analysis of the unit’s decarbonization and cost-saving potential indicate that, except for specific locations, the developed prototype might excel in achieving decarbonization and cost savings primarily in US northern and middle climate zones.

Study of an LLC Converter for Thermoelectric Waste Heat Recovery Integration in Shipboard Microgrids

Static waste heat recovery, by means of thermoelectric generator (TEG) modules, constitutes a fast-growing energy harvesting technology on the way towards greener transportation. Many commercial solutions are already available for small internal combustion engine (ICE) vehicles, whereas further development and cost reductions of TEG devices expand their applicability at higher-power transportation means (i.e., ships and aircrafts). In this light, the integration of waste heat recovery based on TEG modules in a shipboard distribution network is studied in this work. Several voltage step-up techniques are considered, whereas the most suitable ones are assessed via the LTspice simulation platform. The design procedure of the selected LLC resonant converter is presented and analyzed in detail. Furthermore, a flexible control strategy is proposed, capable of either output voltage regulation (constant voltage) or maximum power point tracking (MPPT), according to the application demands. Finally, both simulations and experiments (on a suitable laboratory testbench) are performed. The obtained measurements indicate the high efficiency that can be achieved with the LLC converter for a wide operating area as well as the functionality and adequate performance of the control scheme in both operating conditions.

Study on combustion and emission characteristics of a micro‐rotary cam internal combustion engine

AbstractIn this article, the construction principle of rotary engine and sliding vane internal combustion engine is carefully analyzed, and the concept of micro‐rotary cam internal combustion engine is proposed by integrating and innovating on them. Overall design, theoretical analysis, and model making of miniature rotary cam internal combustion engine and its supporting system. The effects of different air intake modes and different ignition advance angles on the combustion and emission characteristics of internal combustion engines were studied. Through the study of the flow field, combustion and emission characteristics of small rotating internal combustion engines, it is found that the intake form has a great influence on the cylinder smoothness of rotating internal combustion engines. The vortex formed by the end cover inlet air in the middle of the combustion chamber can fully mix the fuel and air in the cylinder, and the mixture is evenly distributed in the combustion chamber to effectively promote the spread of flame. Compared with the surrounding air intake structure, the heat release should be increased by 4.3%, and the total amount of HC and CO generated was 26.8% and 15.7% less, respectively. By studying the turbulent kinetic energy, combustion heat release, peak temperature and pressure in the cylinder, fuel consumption rate and emission characteristics of small rotary internal combustion engine, it is found that when the ignition advance angle of the small rotating internal combustion engine is 5°, the peak pressure in the cylinder is increased by 2.3% compared with other schemes, the fuel consumption rate is high, and the combustion is more complete. In addition, in terms of emission characteristics, the amount of CO and HC generated when the ignition advance angle is 5° are reduced by 35% and 35.3%, respectively.

Evolution of Materials for Internal Combustion Engines Pistons

Piston is one of the most important components in an internal combustion engine which transfers combustion energy to the crankshaft via a connecting rod. Increase in an engine’s efficiency has somehow necessitated improvement in the piston. This improvement can be achieved by better piston design or using material with superior mechanical properties. Engineers have experimented with different materials for pistons since the introduction of internal combustion engines. This paper reviews the evolution of materials for pistons since the beginning of automotive industry to present day and analyses the properties that attracted engineers to use these materials. The paper also focuses on newly developed materials that have the potentials to replace current piston materials and the work that is taking place. The current trend of changing from diesel to petrol in small internal combustion engines and the affect this will have on piston materials has been analysed. Keywords: Aluminium, Combustion Engine, Nanostructured, Piston Material, Piston.

Battery selection criteria for electric vehicles: techno-economic analysis

In this study, different battery types to be used in the conversion of a small and light (600-1000 kg) internal combustion engine vehicle into an electric vehicle were analyzed. The study was conducted to ensure that this vehicle is suitable for urban use and has a range of approximately 100 km. Each battery technology capacity is evaluated to be approximately 15 kWh. While performing the techno-economic analysis of different battery types, it was taken into account that they provide the necessary energy for about 10 years. Seven different battery technologies (lead-acid, gel, Ni-Cd, Li-Ion, LiFePo4, LiPo, Ni-MH) were used for comparison. In the analysis; price assessment in US Dollars ($), 10-year investment cost, weight and volume values, weight and volume values required to produce 1 kWh of energy were presented in tables. In addition to these, a review of battery life was made. Finally, the advantages and disadvantages of battery technologies compared to each other are given. As a result of the study, it was seen that the cheapest technology for a 10-year lifespan was lead-acid technology. It has been determined that lead-acid technology is 30% cheaper than the second cheapest gel technology and 82% cheaper than the most expensive technology, LiPo technology. In the study, it was revealed that the lightest technology was LiPo. It has been determined that this technology is 85% lighter than gel technology. Besides this information, data on cycle life, self-discharge, advantages and disadvantages are presented in tabular form.

Production of the cylinder head and crankcase of a small internal combustion engine using metal laser powder bed fusion

This effort investigates the use of metal additive manufacturing, specifically laser powder bed fusion (LPBF) for the automotive and defense industries by demonstrating its feasibility to produce working internal combustion (IC) engine components. Through reverse engineering, model modifications, parameter selection, build layout optimization, and support structure design, the production of a titanium crankcase and aluminum cylinder head for a small IC engine was made possible. Computed tomography (CT) scans were subsequently used to quantify whether defects such as cracks, geometric deviations, and porosity were present or critical. Once viability of the parts was established, machining and other post-possessing were completed to create functional parts. Final X-ray CT and micro-CT results showed all critical features fell within ±0.127 mm of the original equipment manufacturer (OEM) parts. This allowed reassembly of the engine without any issues hindering later successful operation. Furthermore, the LPBF parts had significantly reduced porosity percentages, potentially making them more robust than their cast counterparts.

Determination of a heat transfer correlation for small internal combustion engines

Small internal combustion engines (ICEs) with displacements < 100 cm3 have greater surface area-to-volume ratios that promote heat transfer through the combustion chamber walls, subsequently lowering the fuel conversion efficiency. As a result, employing common heat transfer correlations developed for larger engines to estimate wall heat transfer yields inaccurate results. Therefore, it is necessary to review literature correlations and determine their applicability for small ICEs. To this end, this paper first presents a literature review highlighting the characteristic length scales, characteristic velocities, and the properties of the working fluid for ICE convective heat transfer correlations. This information is used within a zero-dimensional ICE model to determine an appropriate heat transfer expression for a relatively small two-stroke ICE (53.2 cm3). Through parameter optimization, by matching the gross indicated power over 85 experimental data points using MATLAB’s fmincon routine, the developed expression (Nu=0.449Re3/4Pr1/3) shows good confidence with respect to the power (R2 = 0.924, RMS = 0.257) and an in-cylinder pressure data trace (R2 = 0.991, RMS = 1.52). A following parametric study varying the bore-to-stroke (BtS) ratio for small engines (0.15 cm3 to 100 cm3) finds a localized choice of the BtS and ignition timing at each displacement volume based on the minimum heat transfer due to the combination of a changing surface area and heat transfer coefficient. In the future, including the effects of volumetric efficiency and tuned exhaust pipes can enhance the scope of the proposed model.

Use of Small Internal Combustion Engines for LNG Boil-Off Gas Conversion: An Experimental and Numerical Analysis

LNG technologies have long been used but only recently found widespread employment on medium and small scales compared to the traditional cycle of liquefaction, transport by ship, regasification and injection into the gas network. This has increased the direct use of LNG with the problem of limiting greenhouse gas emissions, linked to gas released principally in the event of prolonged absence of fuel drawing from the cryogenic tank. This study analyzes the energetic exploitation of BOG in small internal combustion engines. The effect on CO2 equivalent emissions was evaluated, making a comparison with the BOG emission into the atmosphere directly or after burning. A 1 kW gasoline engine was selected for a 500-litre LNG tank and converted to gas fueling. The measured consumption and emissions resulted in compliance with a lower environmental impact compared to direct BOG release into the atmosphere despite simplified technical solutions, such a cheap and light 2-stroke engine. In contrast, only a 4-stroke engine has performance such as achieving a reduction in GHG emissions, up to zero, even compared to the case of BOG combustion before releasing it into the atmosphere.

Comprehensive model for energetic analyses of a series hybrid-electric vehicle powered by a passive Turbulent Jet Ignition engine

In the last decades, the concern about vehicles’ environmental impact has progressively increased. Therefore, car manufacturers are moving towards vehicles with low emissions like Hybrid Electric Vehicles (HEV), that in the series architecture utilize an internal combustion engine (ICE) to power an electric generator for battery recharging thus extending the driving range of a Battery Electric Vehicle (BEV). For such applications, small four-stroke spark-ignition (SI) engines are a suitable solution, as they are proven low-cost and reliable systems and allow to increase vehicle driving range with reduced environmental impact. In series HEV the ICE is decoupled from the drive wheels and operates at a fixed working point regardless to the instantaneous power demand, thus promoting the lean mixture operation to achieve high efficiency and low CO2 emissions. In this work, the performance, in terms of driving range, energy consumption and CO2 emissions, of a series HEV are analyzed in experimental and simulation environment. Particularly, the Auxiliary Power Unit (APU) is a small ICE equipped with a passive Turbulent Jet Ignition (TJI) that allows to guarantee stable combustion also under lean mixture operation, with an increase of engine efficiency and a reduction of CO2 emissions. The effects of lean air–fuel ratio on combustion process and engine performance are investigated by a one-dimension (1-D) model and validated vs experimental measurements at the test bench on a prototype single cylinder engine equipped with passive prechamber. The benefits of the high efficiency ICE operation on the series HEV performance, energy consumption and CO2 emissions vs standard and arbitrary driving cycles are analyzed in simulation environment, making use of the simulation results gathered by the 1-D engine model. Simulation analyses are carried out to evaluate the best compromise between battery pack downsizing and energy consumption for a fixed target of vehicle drive range. Simulation results show that TJI concept allows to achieve an APU efficiency up to 32 %, by operating with λ equal to 1.26. Additionally, the analysis on battery pack downsizing evidences that switching from 150 % to 50 % of the reference battery pack capacity results in an increase of the overall energy consumption up to 22 %.

Development of a methodology for calculating the working process of a small-size two-stroke internal combustion engine

On the basis of the available theoretical calculations, methods for calculating the working process and power characteristics of internal combustion engines and the experimental studies carried out, a method for calculating the working process for small-sized two-stroke internal combustion engines was developed and tested. In the course of this work, the following results were obtained: the parameters of the working process and power characteristics of a small two-stroke internal combustion engine; the parameters obtained by calculation during the study of the Evolution 20GX2 engine were compared with the results of an experimental study. According to the results of the comparison, deviations in the values of the parameters of the engine under study from the results of the experimental study at the maximum power and maximum speed modes were identified.

Optimal Hybridization of Conventional ICE Vehicles

Most commercially available hybrid electric vehicle (HEV) drivetrains are made of small internal combustion (IC) engines and large electric drives to improve fuel economy. They usually have higher cost than the conventional IC-engine-based vehicles because of the high costs of the electric drives. This paper proposes a hybridized powertrain composed of the original full-size engine of the vehicle and a universally optimum size parallel electric drive. The dynamic programming (DP) algorithm was used to obtain the sensitivity of the maximum miles per gallon (MPG) values versus the power rating of the electric drive. This sensitivity was then analyzed to determine the optimal window of the electric drive power ratings. This was proven to be universal for all passenger cars of various masses and engine powers. The fuel economy and vehicle performance of this HEV was compared with those of the 2019 Toyota Corolla, a conventional IC-engine-based vehicle, and the 2019 Toyota Prius, a commercially available HEV. The results showed that the proposed universally optimized HEV powertrain achieved better fuel economy and vehicle performance than both the original ICE and HEV vehicles, at low additional vehicle cost.

Comparative analysis of non-exhaust airborne particles from electric and internal combustion engine vehicles

This paper evaluates the effect of the electrification of the small, medium, and large internal combustion engine (ICE) passenger cars on the levels of total particulate matter (PM). The total mean PM10 and PM2.5 emission factors (EFs) on urban, rural, and motorway roads are in the range of 26.13 − 39.57 mg km−1 veh−1 and 13.39 − 18.44 mg km−1 veh−1, respectively, from small to large ICE passenger cars. Correspondingly, the total mean PM10 and PM2.5 non-exhaust EFs on urban, rural, and motorway roads range from 27.76 to 43.43 mg km−1 veh−1 and 13.17 –19.24 mg km−1 veh−1 from equivalent small to large electric vehicles (EVs) without regenerative braking. These results show that the total non-exhaust PM from the equivalent EVs may exceed all PM from ICE passenger cars, including exhaust particle emissions, which are dependent mainly on the extent of regenerative braking, followed by passenger car type and road type. PM10 EFs for equivalent EVs without regenerative braking on urban, rural, and motorway roads are all higher than those from ICE cars. As for PM2.5, most of the equivalent EVs require different extents of regenerative braking to reduce brake emissions to be in line with all particle emissions from relative ICE cars.

Numerical investigations of combustion and emissions characteristics of a novel small scale opposed rotary piston engine fuelled with hydrogen at wide open throttle and stoichiometric conditions

Popularisations of hybrid vehicles and range extender electric vehicles promote the development of high power density and small scale internal combustion engines. Opposed rotary piston (ORP) engines characterised by compact designs, few moving parts and high power density are an ideal power source for the above mentioned vehicles. Due to the short cyclic period of the ORP engine, hydrogen fuel was applied to decrease the combustion duration. This paper investigated the in-cylinder combustion and emissions characteristics of the hydrogen fuelled ORP engine using 3D numerical simulation method at various engine speeds and full load conditions. In-cylinder pressure evolutions, heat release rates, nitrogen monoxide (NO) formations, and power density were analysed to evaluate the engine performance. The results indicated that volumetric efficiency of this ORP engine was higher than 88.3% for all the given scenarios, being benefited from large area of intake ports. Peak in-cylinder pressure decreased significantly with engine speeds, which was mainly resulted from low fuel mass burn fraction before top dead centre (TDC) for high engine speed conditions. As long as the combustion chambers passed TDC, combustion flame propagated from the bowls into the gaps between end faces of adjacent pistons rapidly. In the exhaust stroke, free discharge process of this ORP engine lasted longer duration than reciprocating engines, which would lead to more energy losses. NO was mainly formed after TDC, with the accumulated NO mass being in the range of 0.07 mg–0.5 mg per cycle per cylinder in the engine speed range of 1000–5000 r/min. Maximum power density and NO emissions factor of this engine fuelled with hydrogen was approximately 69.2 kW·L−1 and 10.60 g·(kW·h)−1, respectively. Indicated thermal efficiency dropped from 36.2% to 26.5% when the engine speed increased from 1000 to 5000 r/min.

Combined Effect Of Inlet Manifold Swirl And Piston Head Configuration In A Constant Speed Four Stoke Diesel Engine

The internal combustion engine manifold has a subsystem that supplies the fresh A/F mixture to the engine cylinders where the fuel is combusted. For efficient combustion of charge, the walls of the intake manifold must be smooth / polished to minimize any side resistance. To redesign the inlet port of a small internal combustion engine, to increase the production of turbulence by a swirl. A good swirl promotes more rapid combustion and improves efficiency. The CI engine has a piston shaped flat on the crown and a concave combustion chamber, with this geometry we are driving the engine. But here the A/F ratio mixture cannot mix properly. To avoid this we make piston geometry changes. The main objective of this project is that three new technologies have been adopted here. The first stage is varying the diameter of the convergence - the divergent nozzle. The second stage is the change on the piston head and the last stage is replacing the inlet and exhaust valve with pitch 0.5. Mm to 2 mm and the cut thread depth is 4 mm and three threads per inch. All of these techniques aim to investigate performance techniques to increase air flow to achieve improved engine performance and emissions in direct injection (DI) single cylinder diesel engines. Compared with traditional engine.

Design of energy and materials for ammonia-based extended-range electric vehicles

Under the background of energy and environmental pressure, the traditional automobiles directly driven by fossil fuel-based internal combustion engines are facing elimination. Extended-range electric vehicles (EREVs) charged by small internal combustion engines become an alternative choice because EREVs have longer range and higher efficiency than battery-based electric vehicles, such as lithium battery-based vehicles. However, most EREVs still utilizes fossil fuel-based internal combustion engines, which still have significant carbon footprint. To compromise this downside, this paper proposes a hydrogen fuel cell extended-range electric vehicle design using liquid ammonia as hydrogen source, and quantify the energy and materials flows for the design. This paper establishes a conceptual model of the entire vehicle taking a truck as an example. A typical configuration is selected to perform energy flow balance calculation. The dynamic model of the vehicle is further constructed based on the conceptual model. Based on the performance requirements of the vehicle’s driving, parameters were determined for the motor system, fuel cell system, battery system and super capacitor system.

Energy Balance and Power Loss Pathway Study of a 120 cc Four-Stroke Internal Combustion Engine

Efforts to improve the range and endurance of group 2 (10–25 kg), internal combustion engine (ICE) powered unmanned aerial vehicles (UAVs) have been underway for several years at Air Force Research Laboratory (AFRL). To obtain the desired performance improvements, research into improving the overall efficiency of the ICE powerplants is of great interest. The high specific energy of hydrocarbon fuels (13,000 W h/kg for gasoline), but low fuel conversion efficiency for small ICEs means that relatively minor improvements in the fuel conversion efficiency of the engines can yield large improvements in range and endurance. Little information is available however for the efficiency of ICEs in the size range of interest (10–200 cm3 displacement volume) for group 2 UAVs. Most of the currently available efficiency data for 10–200 cm3 ICEs is for two-stroke engines. The goal of this study was to provide an in-depth probe of the efficiency and energy losses of a small displacement four-stroke engine which could potentially be used to power a group 2 UAV. Energy balances were performed on a Honda GX120 four-stroke engine using empirical research methods. The engine was a 118 cm3 displacement, single cylinder ICE. Energy pathways were characterized as a percentage of the total chemical energy available in the fuel. Energy pathways were characterized into four categories: brake power, cooling load, exhaust sensible enthalpy and incomplete combustion. The effect of five operating parameters was examined in the study. Fuel conversion efficiency ranged from 22.2% to 25.8% as engine speed was swept from 2000 to 3600 RPM, from 20.8% to 27.3% as equivalence ratio was swept from 0.85 to 1.25, and from 15.7% to 24.9% as throttle was swept from 28.5% to 100%. Combustion phasing and cylinder head temperature sweeps showed only minor changes in fuel conversion efficiency.

Thermal management of newly developed non-noble metal-based catalytic converter to reduce cold start emissions of small internal combustion engine

ABSTRACTIn this study, thermal management of a newly developed non-noble metal-based catalytic converter, more suitable to smaller engines, has been investigated. Two different approaches are explored; first, use of phase change material (PCM) to keep the converter hot beyond light off temperature during shorter soak times and second, electrically heating up converter before or after engine cold start-up to reduce cold start emissions. The converter used had light off temperatures of 195 and 206°C for carbon monoxide and hydro carbons, respectively. Results showed that 1 kg of PCM was capable of keeping the converter hot beyond light off temperatures for a soak time of 2.5 h. Similarly, use of glow plugs also decreased the light off time of the converter to less than 2 min as compared to 13 min without thermal management measures.

Conceptual study of scroll-type rotary gasoline Internal Combustion Engine

This paper reports the study of a conceptual gasoline Internal Combustion Engine (ICE) using scroll type rotary device rather than conventional piston as the main engine component. The proposed innovate engine adopts Humphrey Cycle to maximize the power performance of ICE. A performance comparison of the Humphrey Cycle, Otto cycle and Brayton cycle has firstly been conducted and studied. The effects of using different designed compression ratio under variable expansion ratio have been investigated, which identify the optimal operational conditions under different compression/expansion ratio of the engine. A case study has been conducted to study the performance of small scale scroll-type rotary ICE. Results pointed out under designed compression ratio from 2:1 to 10:,1 the effective energy efficiency of the scroll-type rotary ICE ranges from 0.41 to 0.55 and the effective power from the system ranges from 2.88 to 15.82 kW.

Optimization of an organic Rankine cycle as bottoming cycle of a 1 kWe GENSET for residential applications

A novel 1 kWe GENSET featuring an internal combustion engine (ICE) operating on Spark-Assisted Compression Ignition (SACI) combustion of natural gas is under development to achieve an overall power generation efficiency of 40%. The aim is to create an efficient electricity generation system that can provide the energy necessary for light residential use at high thermal efficiency and low user cost. In order to achieve such power generation efficiency for a small-scale energy/heat production unit, an organic Rankine cycle (ORC) has been proposed as a bottoming cycle to recover heat from the exhaust of the small internal combustion engine. The ORC has been optimized to operate with a heat source inlet temperature of 400 ºC, which is necessary for use with the integrated catalytic converter evaporator proposed for the system. By means of a thermodynamic cycle model, the final cycle architecture has been identified along with the design of a novel two-stage scroll expander integrated with working fluid pump. Results showed that by employing R1233zd(E) as the working fluid, the theoretical ORC thermal efficiency is as high as 14.79% with a net ORC power output of 148.6 W.

Comparative assessments of two integrated systems with/without fuel cells utilizing liquefied ammonia as a fuel for vehicular applications

In the current study, two different integrated systems for vehicular applications are presented and thermodynamically analyzed. The first system consists of liquefied ammonia tank, dissociation and separation unit (DSC) for decomposition of ammonia and an internal combustion engine (ICE) to power the vehicle. The second system is a hybrid system consisting of liquefied ammonia tank, DSC unit, a small ICE and a fuel cell system. In the second system, the main power unit is fuel cell and a supplementary internal combustion engines is also utilized. The exhaust gasses emitted from the ICE are used to provide the required heat for the thermal decomposition process of ammonia. The ICE is fueled with a mix of ammonia and hydrogen generated from the DSC unit that is installed in the two systems. Hydrogen generated from DSC unit will be utilized to operate fuel cell installed in system 2. The proposed systems are analyzed and assessed both energetically and exergetically. A comprehensive parametric study is carried out for comparative assessments to determine the influence of altering design and operating parameters such as the amount of ammonia fuel supplied to the two systems on the performance of the two systems. The overall energy and exergy efficiencies for system 1 and system 2 are found to be 61.89%, 63.34%, 34.73% and 38.44% respectively. The maximum exergy destruction rate in the two systems occurred in the ICE.